Power transmission system capable of synchronizing power transmitter apparatus having multiple operation modes, with power receiver apparatus having multiple operation

This application is the U.S. National Phase under 35 U.S.C. § 371 of International Patent Application No. PCT/JP2018/007025, filed on Feb. 26, 2018, which in turn claims the benefit of Japanese Application No. 2017-040602, filed on Mar. 3, 2017, the entire disclosures of which Applications are incorporated by reference herein.

The present disclosure relates to a power transmitter apparatus which transmits power (electric power) via a transmission path, a power receiver apparatus which receives power via a transmission path, and a power transmission system including the power transmitter apparatus and the power receiver apparatus.

In recent years, power supplies of renewable energy, typically photovoltaic power generation, wind power generation, and biofuel power generation, are increasingly used, as well as conventional power supplies provided by power companies, such as thermal power generation, hydropower generation, and nuclear power generation. In addition, apart from large-scale commercial power networks currently provided, local and small-scale power networks capable of achieving local production and local consumption of power have been being spread worldwide in order to reduce losses of long-distance power transmission.

In a small-scale power network, power can be supplied self-sufficiently by using a natural energy power generator, and electric load equipment capable of efficient power regeneration. This type of power network is highly promising as a power transmission system for supplying electricity to non-electrified areas, such as desert oasis and remote islands.

For example, each of Patent Documents 1 to 3 discloses a power transmission system which transmits power from a power supply to a load via a power line.

Patent Documents

PATENT DOCUMENT 1: Japanese Patent Publication No. JP 5612718 B

PATENT DOCUMENT 2: Japanese Patent Publication No. JP 5612920 B

PATENT DOCUMENT 3: Japanese Patent laid-open Publication No. JP 2011-091954 A

Technical Problem

In order to transmit power from a power supply to a load via a power line, a power transmission system includes: a power transmitter apparatus which transmits power supplied from the power supply via a transmission path; and a power receiver apparatus which receives the power via the transmission path and supplies the power to the load.

When transmitting power from an alternating-current power supply to an alternating-current load in a power transmission system, in some case, the phase of power of the power supply should match the phase of power of the load. In this case, it is necessary to surely synchronize the power transmitter apparatus and the power receiver apparatus with each other.

An object of the present disclosure is to solve the aforementioned problems, and to provide a power transmitter apparatus capable of surely synchronizing with a power receiver apparatus.

Solution to Problem

According an aspect of the present disclosure, a power transmitter apparatus transmits power to at least one power receiver apparatus via a transmission path. The power transmitter apparatus is provided with: a measuring device that measures a current value or voltage value associated with input power inputted to the power transmitter apparatus; a code modulation circuit that modulates the input power to generate a code-modulated wave by code modulation using a modulation code based on a code sequence, and transmits the code-modulated wave to the power receiver apparatus via the transmission path; and a control circuit that controls the code modulation circuit. The code modulation circuit has operation modes different from each other depending on a direction of the input power, and a direction of the code-modulated wave to be generated. The control circuit generates waveform information indicating variations of direction of the input power over time, based on the current value or voltage value measured by the measuring device, and determines the operation mode of the code modulation circuit based on the waveform information.

These generic and specific aspects may be implemented as a system, as a method, or as any combination of systems and methods.

Advantageous Effects of Invention

According to the aspect of the present disclosure, the power transmitter apparatus can surely synchronize with a power receiver apparatus.

FIG. 1 is a block diagram showing a configuration of a power transmission system according to a first embodiment.

FIG. 2 is a waveform diagram showing an exemplary signal waveform of a modulated current I 2 of the power transmission system of FIG. 1 .

FIG. 3 is a waveform diagram showing an exemplary signal waveform of a modulated current I 2 of a communication system according to a comparison example.

FIG. 4 is a waveform diagram showing exemplary signal waveforms in the power transmission system of FIG. 1 , in which: (a) shows a signal waveform of a generated current I 1 ; (b) shows a signal waveform of a modulated current I 2 ; and (c) shows a signal waveform of a demodulated current I 3 .

FIG. 5 is a block diagram showing a configuration of a code modulator 2 of FIG. 1 .

FIG. 6 is a block diagram showing a configuration of a code demodulator 4 of FIG. 1 .

FIG. 7 is a block diagram showing configurations of a code modulation circuit 23 and a code demodulation circuit 33 of FIG. 1 .

FIG. 8A is a diagram showing an example of a modulation code of the code modulator 2 and a demodulation code of the code demodulator 4 in the power transmission system of FIG. 1 , as a first implementation example in which direct-current power is transmitted and received.

FIG. 8B is a diagram showing an example of a modulation code of the code modulator 2 and a demodulation code of the code demodulator 4 in the power transmission system of FIG. 1 , as a second implementation example in which direct-current power is transmitted and received.

FIG. 9 is a waveform diagram showing exemplary signal waveforms in the power transmission system according to a second embodiment, in which: (a) shows a signal waveform of a generated current I 1 ; (b) shows a signal waveform of a modulated current I 2 ; and (c) shows a signal waveform of a demodulated current I 3 .

FIG. 10 is a block diagram showing a partial configuration of a code modulator 2 A of the power transmission system according to the second embodiment.

FIG. 11 is a block diagram showing a partial configuration of a code demodulator 4 A of the power transmission system according to the second embodiment.

FIG. 12A is a diagram showing an example of a modulation code of the code modulator 2 A and a demodulation code of the code demodulator 4 A in the power transmission system according to the second embodiment, as a third implementation example in which alternating-current power is transmitted and received.

FIG. 12B is a diagram showing an example of a modulation code of the code modulator 2 A and a demodulation code of the code demodulator 4 A in the power transmission system according to the second embodiment, as a fourth implementation example in which direct-current power is transmitted and received.

FIG. 13A is a circuit diagram showing a configuration of a bidirectional switch circuit SS 21 A for a code modulation circuit 23 A used in a power transmission system according to a modified embodiment of the second embodiment.

FIG. 13B is a circuit diagram showing a configuration of a bidirectional switch circuit SS 22 A for the code modulation circuit 23 A used in the power transmission system according to the modified embodiment of the second embodiment.

FIG. 13C is a circuit diagram showing a configuration of a bidirectional switch circuit SS 23 A for the code modulation circuit 23 A used in the power transmission system according to the modified embodiment of the second embodiment.

FIG. 13D is a circuit diagram showing a configuration of a bidirectional switch circuit SS 24 A for the code modulation circuit 23 A used in the power transmission system according to the modified embodiment of the second embodiment.

FIG. 14A is a circuit diagram showing a configuration of a bidirectional switch circuit SS 31 A for a code demodulation circuit 33 A used in the power transmission system according to the modified embodiment of the second embodiment.

FIG. 14B is a circuit diagram showing a configuration of a bidirectional switch circuit SS 32 A for the code demodulation circuit 33 A used in the power transmission system according to the modified embodiment of the second embodiment.

FIG. 14C is a circuit diagram showing a configuration of a bidirectional switch circuit SS 33 A for the code demodulation circuit 33 A used in the power transmission system according to the modified embodiment of the second embodiment.

FIG. 14D is a circuit diagram showing a configuration of a bidirectional switch circuit SS 34 A for the code demodulation circuit 33 A used in the power transmission system according to the modified embodiment of the second embodiment.

FIG. 15 is a diagram showing waveforms of a generated current, a modulated current, and a demodulated current, when using the modulation code and the demodulation code of FIG. 12A .

FIG. 16 is a block diagram showing a configuration of a power transmission system according to a third embodiment.

FIG. 17A is a diagram showing an example of a modulation code of a code modulator 2 A- 1 and a demodulation code of a code demodulator 4 A- 1 in the power transmission system of FIG. 16 , as a fifth implementation example in which direct-current power is transmitted and received.

FIG. 17B is a diagram showing an example of a modulation code of the code modulator 2 A- 2 and a demodulation code of the code demodulator 4 A- 2 in the power transmission system of FIG. 16 , as a sixth implementation example in which direct-current power is transmitted and alternating-current power is received.

FIG. 18 is a waveform diagram showing exemplary signal waveforms in the power transmission system according to the third embodiment, in which: (a) shows a signal waveform of a generated current I 11 ; (b) shows a signal waveform of a generated current I 12 ; (c) shows a signal waveform of a modulated current I 2 ; (d) shows a signal waveform of a demodulated current I 31 ; and (e) shows a signal waveform of a demodulated current I 32 .

FIG. 19 is a block diagram showing a configuration of a power transmission system according to a fourth embodiment.

FIG. 20 is a block diagram showing a configuration of a code modulator 2 B of FIG. 19 .

FIG. 21 is a block diagram showing a configuration of a code demodulator 4 B of FIG. 19 .

FIG. 22 is a sequence diagram showing generation of a modulation code and a demodulation code in the power transmission system of FIG. 19 .

FIG. 23 is a sequence diagram showing a modified embodiment of generation of a modulation code and a demodulation code in the power transmission system of FIG. 19 .

FIG. 24 is a sequence diagram showing generation of a modulation code and a demodulation code in a power transmission system according to a fifth embodiment.

FIG. 25 is a sequence diagram showing generation of a modulation code and a demodulation code in a power transmission system according to a modified embodiment of the fifth embodiment.

FIG. 26 is a sequence diagram showing generation of a modulation code and a demodulation code in a power transmission system according to a sixth embodiment.

FIG. 27 is a sequence diagram showing generation of a modulation code and a demodulation code in a power transmission system according to a modified embodiment of the sixth embodiment.

FIG. 28 is a sequence diagram showing generation of a modulation code and a demodulation code in a power transmission system according to a seventh embodiment.

FIG. 29 is a sequence diagram showing generation of a modulation code and a demodulation code in a power transmission system according to a modified embodiment of the seventh embodiment.

FIG. 30 is a block diagram showing a configuration of a code modulator 2 B of a power transmission system according to an eighth embodiment.

Findings Underlying Present Disclosure

Patent Document 1 discloses an interconnection apparatus for power transmitter apparatuses, the interconnection apparatus being capable of transmitting and receiving power among a plurality of power systems. According to Patent Document 1, the interconnection apparatus is provided with a converter and an inverter. For power transmission, the converter converts transmitting power from alternating current to direct current, and the converted power is transmitted to the interconnection apparatus connected to a receiving power system. At the interconnection apparatus of the receiving power system, the inverter converts the power so as to have a desired frequency, thus providing power having an optimum frequency for the power system to which the interconnection apparatus is connected. Moreover, Patent Document 2 discloses a configuration further provided with a power storage apparatus, in addition to the components of Patent Document 1.

On the other hand, Patent Document 3 discloses a method of transmitting power from a plurality of power transmitter apparatuses to a plurality of power receiver apparatuses. According to Patent Document 3, power is transmitted from the plurality of power transmitter apparatuses to the plurality of power receiver apparatuses in a time division manner. According to Patent Document 3, control signals are wirelessly transmitted among the power transmitter apparatuses and the power receiver apparatuses in order to transmit and receive power.

However, according to Patent Documents 1 and 2, the interconnection apparatus is provided with the inverter and converter, and basically, individual power transmission cables are required for all combinations of the power systems transmitting and receiving power. According to Patent Documents 1 and 2, the interconnection apparatus may be configured so as to reduce the number of power transmission cables, however, in any case, a large number of power transmission cables are required. Thus, installation costs and the cables' material costs increase. In addition, the interconnection apparatus should be provided with the same number of pairs of the inverter and the converter as the number of the power systems to be connected. Accordingly, the cables' costs may increase, and costs may further increase due to the increased size of the interconnection apparatus.

In addition, according to Patent Document 3, it is possible to transmit and receive power among the plurality of power transmitter apparatuses and the plurality of power receiver apparatuses in a time division manner, and advantageously, it is possible to reduce the number of power transmission cables. However, in case of time-division power transmission, it is not possible to transmit and receive power among the plurality of power systems, simultaneously. In other words, it may not be possible to immediately handle a power demand from a load connected to a power receiver. Furthermore, when transmitting and receiving power among a large number of pairs of the power transmitter apparatuses and the power receiver apparatuses, only a short time is allocated for one pair of the power transmitter apparatus and the power receiver apparatus to transmit and receive power, and therefore, large pulse power is transmitted via the power transmission cable. Accordingly, the transmission cable with a high power durability is required, and thus, it may increase costs. In addition, since time intervals in which power can not be received occur, it may be required to provide the power receiver apparatuses with a buffer for large power. Furthermore, in order to transmit and receive power in a time division manner, time-synchronization is required among the plurality of power transmitter apparatuses and the plurality of power receiver apparatuses. In order to achieve such synchronization, very accurate controls among the apparatuses are required, and thus, it may increase the entire system costs.

As described above, according to both Patent Documents 1 and 2, a large number of power transmission cables are used, and therefore, it is not possible to reduce the power transmission cables by multiplexed power transmission. Further, the interconnection apparatus requires a pair of inverter and converter for each of the power transmission cables, and therefore, it is not possible to reduce the size of the interconnection apparatus. Accordingly, it is difficult to transmit and receive power among a large number of power systems. On the other hand, according to Patent Document 3, power is transmitted and received among the plurality of power transmitter apparatuses and the plurality of power receiver apparatuses via the power transmission cables in a time division manner, thus reducing the number of the power transmission cables. However, it is not possible to provide a transmission system capable of transmitting and receiving power among the plurality of power systems, simultaneously. Accordingly, there is a demand for a power transmission system with a reduced number of power transmission cables, and capable of transmitting and receiving power from a plurality of power transmitter apparatuses to a plurality of power receiver apparatuses, simultaneously, and more reliably, while reducing sizes and thicknesses of the power transmitter apparatuses and the power receiver apparatuses.

Further, as described above, when transmitting power from an alternating-current power supply to an alternating-current load, in some case, the phase of power of the power supply should match the phase of power of the load. In this case, it is necessary to surely synchronize the power transmitter apparatus and the power receiver apparatus with each other.

In addition, when an alternating-current power supply is connected to a power transmitter apparatus, the waveform of power transmitted over the transmission path depends on an operation mode of the power transmitter apparatus. Therefore, in order for a power receiver apparatus to receive the transmitted power in an appropriate manner, the power receiver apparatus should surely synchronize with the power transmitter apparatus, and an appropriate operation mode should be selected corresponding to the operation mode of the power transmitter apparatus.

Based on the above consideration, the inventors provide the following aspects of the invention.

Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. In the following embodiments, similar constituent elements are denoted by identical reference numerals.

An object of the present disclosure is to provide a power transmitter apparatus and a power receiver apparatus, capable of selecting appropriate operation modes, respectively, and capable of surely synchronizing with each other, and provide a power transmission system including such a power transmitter apparatus and a power receiver apparatus. In first to third embodiments, we describe preparatory overviews of power transmission systems. Thereafter, in fourth to eighth embodiments, we describe power transmission systems which solves the problems.

First Embodiment

FIG. 1 is a block diagram showing a configuration of a power transmission system according to the first embodiment. Referring to FIG. 1 , the power transmission system according to the first embodiment is provide with a power generator 1 , a code modulator 2 , a transmission path 3 , a code demodulator 4 , a load 5 , and a controller 10 . The transmission path 3 is, for example, a wired transmission path including two power lines, or a wireless transmission path.

The controller 10 is provided with a control circuit 11 and a communication circuit 12 . The control circuit 11 communicates with the code modulator 2 and the code demodulator 4 via the communication circuit 12 , and controls operations of the code modulator 2 and the code demodulator 4 .

In the power transmission system of FIG. 1 , the code modulator 2 operates as a power transmitter apparatus, and the code demodulator 4 operates as a power receiver apparatus. The code modulator 2 modulates first power to generate a code-modulated wave by code modulation using a modulation code based on a code sequence, and transmits the code-modulated wave to the code demodulator 4 via the transmission path 3 . The code demodulator 4 receives the code-modulated wave from the code modulator 2 via the transmission path 3 , and demodulates the received code-modulated wave to generate second power by code demodulation using a demodulation code based on a code sequence identical to the code sequence of the modulation code used for the code modulation. The first power is, for example, direct-current power generated by the power generator 1 , and is shown as a generated current I 1 in FIG. 1 . The code-modulated wave is alternating-current power modulated by code modulation, and is shown as a modulated current I 2 in FIG. 1 . The second power is, for example, direct-current power to be supplied to the load 5 , and is shown as a demodulated current I 3 in FIG. 1 .

The power transmission system of FIG. 1 is further provided with power meters 1 m and 5 m . The power meter 1 m is first power measuring means which measures an amount of the first power. More specifically, the power meter 1 m measures an amount of direct-current power generated by the power generator 1 and transmitted from the power generator 1 to the code modulator 2 . The power meter 1 m may be provided to the power generator 1 , or disposed between the power generator 1 and the code modulator 2 . The power meter 5 m is second power measuring means for measuring an amount of the second power. More specifically, the power meter 5 m measures an amount of direct-current power transmitted from the code demodulator 4 to the load 5 , and used by the load 5 . The power meter 5 m may be provided to the load 5 , or may be disposed between the code demodulator 4 and the load 5 . The amounts of powers measured by the power meters 1 m and 5 m are transmitted to the controller 10 .

The controller 10 controls operations of the code modulator 2 and the code demodulator 4 based on the amounts of powers received from the power meters 1 m and 5 m . For example, the controller 10 transmits control signals to the code modulator 2 and the code demodulator 4 , the control signals including synchronization signals for synchronizing the code modulator 2 and the code demodulator 4 to each other, thus achieving code modulation and code demodulation of power in an accurately synchronized manner.

The controller 10 sets a modulation code to the code modulator 2 , and a demodulation code to the code demodulator 4 , based on one code sequence. The code sequence of the modulation code used for modulation by the code modulator 2 , and the code sequence of the demodulation code used for demodulation by the code demodulator 4 may be set in advance to the code modulator 2 and the code demodulator 4 . In addition, for example, the controller 10 may transmit, as the control signals, the code sequence of the modulation code used for modulation by the code modulator 2 , and the code sequence of the demodulation code used for demodulation by the code demodulator 4 . Further, the controller 10 may transmit, as the control signals, only information specifying the code sequences, without transmitting the code sequences themselves, so that the code modulator 2 and the code demodulator 4 to generates the code sequences, respectively. In this case, it is possible to achieve code modulation and code demodulation between the code modulator 2 and the code demodulator 4 corresponding to each other in an accurately synchronized manner.

FIG. 2 is a waveform diagram showing an exemplary signal waveform of the modulated current I 2 of the power transmission system of FIG. 1 . In addition, FIG. 3 is a waveform diagram showing an exemplary signal waveform of a modulated current I 2 of a communication system according to a comparison example.

The code modulator 2 of FIG. 1 modulates a current of power, which is generated by the power generator 1 , by code modulation using a modulation code based on a predetermined code sequence. In this case, the code modulator 2 generates an alternating-current code-modulated wave made of currents flowing in directions corresponding to code values of “1” and “−1”, respectively, as shown in FIG. 2 . This code-modulated wave can transmit power in both periods of positive current flows, and periods of negative current flows (e.g., period T 01 of FIG. 2 ). While the first embodiment indicates an example in which direct-current power is modulated by code modulation, alternating-current power may be modulated by code modulation as in a second embodiment described below.

In the data transmission system according to the comparison example, e.g., to be used for communication, code values of “1” and “0” are typically used for code modulation, as shown in FIG. 3 . However, according to the code-modulated wave as shown in FIG. 3 , when the code value of the modulation code is “0” (e.g., period T 02 of FIG. 3 ), a modulated current or voltage becomes zero, that is, a period of no power transmission occurs. Such periods of no power transmission may reduce overall power transmission efficiency. More specifically, for the case of communication, since information such as data should be transmitted in an accurately synchronized manner, it is only required that the code demodulator accurately distinguish between “0” and “1”. On the other hand, for the case of power transmission, a power loss due to the period of no power transmission is not permissible from a viewpoint of efficiency in use of energy. Accordingly, by using an alternating-current code-modulated wave flowing in directions corresponding to the code values of “1” and “−1”, respectively, as shown in FIG. 2 , it is possible to transmit power with higher transmission efficiency than that of the comparison example.

FIG. 4 is a waveform diagram, where (a) to (c) show exemplary signal waveforms in the power transmission system of FIG. 1 . In FIG. 4 , (a) shows a signal waveform of the generated current I 1 , (b) shows a signal waveform of the modulated current I 2 , and (c) shows a signal waveform of the demodulated current I 3 . The power generator 1 generates the direct-current generated current I 1 . The code modulator 2 multiplies the generated current I 1 by a modulation code m 0 to generate the alternating-current modulated current I 2 . The code demodulator 4 multiplies the modulated current I 2 by a demodulation code d 0 identical to the modulation code m 0 to reproduce the direct-current power generated by the power generator 1 , and supply the reproduced direct-current power to the load 5 .

Referring to FIG. 4 , T 10 indicates a period of one cycle of the modulation code m 0 and the demodulation code d 0 . The same also applies to subsequent drawings.

According to the exemplary signal waveform of FIG. 4 , the direct-current generated current I 1 ( FIG. 4( a ) ) is multiplied by the modulation code m 0 having a frequency of 35 kHz, to generate the modulated current I 2 ( FIG. 4( b ) ) of the code-modulated wave. In this case, the duration of each bit of the modulation code m 0 is 1/(35 kHz)/2=14.2 microseconds.

Each bit of the modulation code m 0 and the demodulation code d 0 has a code value “1” or “−1”. The code value “1” of the modulation code m 0 indicates that the code modulator 2 outputs a current in the same direction as the direction of an inputted current, and the code value “−1” of the modulation code m 0 indicates that the code modulator 2 outputs a current in the direction opposite to the direction of the inputted current. Similarly, the code value “1” of the demodulation code d 0 indicates that the code demodulator 4 outputs a current in the same direction as the direction of an inputted current, and the code value “−1” of the demodulation code d 0 indicates that the code demodulator 4 outputs a current in the direction opposite to the direction of the inputted current.

For example, the modulation code m 0 and the demodulation code d 0 are given as follows.

m 0=[1 −1 1 1 1 −1 −1 −1 1 −1 −1 −1 1 1]  (1)

d 0 =m 0=[1 −1 1 1 1 −1 −1 −1 1 −1 −1 −1 1 1]  (2)

Subsequently, the modulated current I 2 of the code-modulated wave generated by the modulation code m 0 is multiplied by the demodulation code d 0 . This multiplication is denoted as follows.

m 0 ×d 0=[1 1 1 1 1 1 1 1 1 1 1 1 1 1]  (3)

As apparent from Mathematical Expression (3), the demodulated current I 3 ( FIG. 4( c ) ) is obtained, which is direct current similarly to the original generated current I 1 .

As described above, it is possible to achieve direct-current power transmission in an accurately synchronized manner, without power loss, by using the code modulator 2 and the code demodulator 4 according to the present embodiment. In addition, it is possible to achieve efficient power transmission for a longer period, for example, by repeatedly using the modulation code m 0 and demodulation code d 0 as described above.

Further, the modulation code m 0 can be divided into its first half code portion m 0 a , and its second half code portion m 0 b , as follows.

m 0 a =[1 −1 1 1 1 −1 −1]  (4)

m 0 b =[−1 1 −1 −1 −1 1 1]  (5)

In this case, the code portion m 0 b is generated by inverting the sign of the code value of each bit of the code portion m 0 a . More specifically, when the code value of a certain bit of the code portion m 0 a is “1”, the code value of a corresponding bit of the code portion m 0 b is “−1”. Similarly, when the code value of a certain bit of the code portion m 0 a is “−1”, the code value of a corresponding bit of the code portion m 0 b is “1”.

FIG. 5 is a block diagram showing a configuration of the code modulator 2 of FIG. 1 . Referring to FIG. 5 , the code modulator 2 is provided with a control circuit 20 , a communication circuit 21 , a code generation circuit 22 , and a code modulation circuit 23 . The communication circuit 21 receives a synchronization signal and a control signal from the controller 10 , the control signal including a code sequence itself or information specifying the code sequence, and outputs the received signals to the control circuit 20 . In this case, the synchronization signal may be, for example, trigger signals to start and end modulation, or time information indicating a start time and an end time of modulation. Based on the control signal, the control circuit 20 controls the code generation circuit 22 so as to generate a modulation code based on a code sequence and output the modulation code to the code modulation circuit 23 , and controls start and end of operation of the code modulation circuit 23 . The code modulation circuit 23 has input ports T 1 and T 2 connected to the power generator 1 , and output ports T 3 and T 4 connected to the transmission path 3 .

FIG. 6 is a block diagram showing a configuration of the code demodulator 4 of FIG. 1 . Referring to FIG. 6 , The code demodulator 4 is provided with a control circuit 30 , a communication circuit 31 , a code generation circuit 32 , and a code demodulation circuit 33 . The communication circuit 31 receives a synchronization signal and a control signal from the controller 10 , the control signal including a code sequence itself or information specifying the code sequence, and outputs the received signals to the control circuit 30 . In this case, the synchronization signal may be, for example, trigger signals to start and end demodulation, or time information indicating a start time and an end time of demodulation. Based on the control signal, the control circuit 30 controls the code generation circuit 32 so as to generate a demodulation code based on a code sequence and output the demodulation code to the code demodulation circuit 33 , and controls start and end of operation of the code demodulation circuit 33 . The code demodulation circuit 33 has input ports T 11 and T 12 connected to the transmission path 3 , and output ports T 13 and T 14 connected to the load 5 .

Note that in the power transmission system of FIG. 1 , the control signals from the controller 10 to the code modulator 2 and the code demodulator 4 may be transmitted via control signal lines different from the transmission path 3 , or may be transmitted via the transmission path 3 in a manner multiplexed with the code-modulated wave using some multiplexing scheme. In the latter case, it is possible to omit cables provided for communication from the controller 10 to the code modulator 2 and the code demodulator 4 , and reduce cost.

FIG. 7 is a block diagram showing configurations of the code modulation circuit 23 and the code demodulation circuit 33 of FIG. 1 . Referring to FIG. 7 , the code modulation circuit 23 is provided with four switch circuits SS 1 to SS 4 connected in a bridge configuration. The switch circuits SS 1 to SS 4 include unidirectional switch elements S 1 to S 4 , respectively, each made of, for example, a metal-oxide-semiconductor (MOS) transistor. In addition, the code demodulation circuit 33 is provided with four switch circuits SS 11 to SS 14 connected in a bridge configuration. The switch circuits SS 11 to SS 14 include unidirectional switch elements S 11 to S 14 , respectively, each made of, for example, an MOS transistor.

The code generation circuit 22 generates and outputs the modulation codes m 1 and m 2 to the code modulation circuit 23 under control of the control circuit 20 , in order to operate the code modulator 2 according to the modulation code m 0 as described above. The switch elements S 1 and S 4 of the code modulation circuit 23 are controlled according to the modulation code m 1 , and the switch elements S 2 and S 3 of the code modulation circuit 23 are controlled according to the modulation code m 2 . Each of the modulation codes m 1 and m 2 has code values “1” and “0”. For example, when a signal of the code value “1” is inputted to each of the switch elements S 1 to S 4 , each of the switch elements S 1 to S 4 is turned on. When a signal of the code value “0” is inputted to each of the switch elements S 1 to S 4 , each of the switch elements S 1 to S 4 is turned off. Note that switch elements other than the switch elements S 1 to S 4 described in the present description operate in a similar manner. In this case, the switch elements S 1 to S 4 have directionality as follows. When the switch element S 1 is turned on, the switch element S 1 outputs a generated current inputted from the port T 1 , to the port T 3 . When the switch element S 3 is turned on, the switch element S 3 outputs a generated current inputted from the port T 1 , to the port T 4 . When the switch element S 2 is turned on, the switch element S 2 outputs a modulated current inputted from the port T 3 , to the port T 2 . When the switch element S 4 is turned on, the switch element S 4 outputs a modulated current inputted from the port T 4 , to the port T 2 .

The code generation circuit 32 generates and outputs the demodulation codes d 1 and d 2 to the code demodulation circuit 33 under control of the control circuit 30 , in order to operate the code demodulator 4 according to the demodulation code d 0 as described above. The switch elements S 11 and S 14 of the code demodulation circuit 33 are controlled according to the demodulation code d 2 , and the switch elements S 12 and S 13 of the code demodulation circuit 33 are controlled according to the demodulation code d 1 . Each of the demodulation codes d 1 and d 2 has code values “1” and “0”. In this case, the switch elements S 11 to S 14 have directionality as described below. When the switch element S 11 is turned on, the switch element S 11 outputs a modulated current inputted from the port T 12 , to the port T 13 . When the switch element S 13 is turned on, the switch element S 13 outputs a modulated current inputted from the port T 11 , to the port T 13 . When the switch element S 12 is turned on, the switch element S 12 outputs a demodulated current inputted from the port T 14 , to the port T 12 . When the switch element S 14 is turned on, the switch element S 14 outputs a demodulated current inputted from the port T 14 , to the port T 11 .

In the notation of FIG. 7 , directions of current flows in the switch elements S 11 to S 14 of the code demodulator 4 are opposite to directions of current flows in the switch elements S 1 to S 4 of the code modulator 2 .

FIG. 8A is a diagram showing an example of a modulation code of the code modulator 2 and a demodulation code of the code demodulator 4 in the power transmission system of FIG. 1 , as a first implementation example in which direct-current power is transmitted and received. More specifically, FIG. 8A shows an example of the modulation codes m 1 and m 2 inputted to the switch elements S 1 to S 4 of the code modulator 2 , and the demodulation codes d 1 and d 2 inputted to the switch elements S 11 to S 14 of the code demodulator 4 .

As shown in FIG. 8A , the modulation code m 1 and the demodulation code d 1 are identical to each other, and each is made of a code sequence c 1 a . In addition, the modulation code m 2 and the demodulation code d 2 are identical to each other, and each is made of a code sequence c 1 b . In addition, the code sequences c 1 a and c 1 b are configured such that when the code value of a certain bit of the code sequence c 1 a is “1”, the code value of a corresponding bit of the code sequence c 1 b is “0”; and when the code value of a certain bit of the code sequence c 1 a is “0”, the code value of a corresponding bit of the code sequence c 1 b is “1”.

Accordingly, among the switch elements S 1 to S 4 and S 11 to S 14 of FIG. 7 , when a switch element receiving the code value of a certain bit of the code sequence c 1 a is turned on, the switch element receiving the code value of a corresponding bit of the code sequence c 1 b is turned off. In addition, when the switch element receiving the code value of a certain bit of the code sequence c 1 a is turned off, the switch element receiving the code value of a corresponding bit of the code sequence c 1 b is turned on.

According to the code modulation circuit 23 of FIG. 7 , when the switch elements S 1 and S 4 are turned on, the switch elements S 2 and S 3 are turned off; and when the switch elements S 1 and S 4 are turned off, the switch elements S 2 and S 3 are turned on. Thus, when the switch elements S 1 and S 4 are turned on, and the switch elements S 2 and S 3 are turned off, the modulated current I 2 flows in the transmission path 3 in a positive direction, i.e., in a direction of solid arrows. On the other hand, when the switch elements S 1 and S 4 are turned off, and the switches S 2 and S 3 are turned on, the modulated current I 2 flows in the transmission path 3 in a negative direction, i.e., in a direction of dotted arrows. Accordingly, as shown in FIG. 4 , when the direct-current generated current I 1 is inputted to the code modulator 2 , the alternating-current modulated current I 2 can be transmitted to the transmission path 3 .

In the code demodulation circuit 33 of FIG. 7 , the switch elements S 11 to S 14 are turned on or off in response to the demodulation codes d 1 and d 2 in synchronization with the code modulation circuit 23 . In this case, the switch elements S 12 and S 13 are turned on or off in accordance with the demodulation code d 1 identical to the modulation code m 1 , and the switch elements S 11 and S 14 are turned on or off in accordance with the demodulation code d 2 identical to the modulation code m 2 . Thus, when the code value of the modulation code m 1 is “1”, and the code value of the modulation code m 2 is “0”, i.e., when the modulated current I 2 flows in the transmission path 3 in the positive direction, the code value of the demodulation code d 1 is “1”, and the code value of the demodulation code d 2 is “0”. Accordingly, by turning on the switch elements S 13 and S 12 and turning off the switch elements S 11 and S 14 , the demodulated current I 3 flows at the output ports T 13 and T 14 of the code demodulation circuit 33 in the positive direction, i.e., in the direction of the solid arrows. On the other hand, when the code value of the modulation code m 1 is “0”, and the code value of the modulation code m 2 is “1”, i.e., when the modulated current I 2 flows in the transmission path 3 in the negative direction, the code value of the demodulation code d 1 is “0”, and the code value of the demodulation code d 2 is “1”. Accordingly, by turning on the switch elements S 11 and S 14 and turning off the switch elements S 12 and S 13 , the demodulated current I 3 again flows at the output ports T 13 and T 14 of the code demodulation circuit 33 in the positive direction, i.e., in the direction of the solid arrows.

As described above, when using the modulation codes m 1 and m 2 and the demodulation codes d 1 and d 2 of FIG. 8A , equivalently, the code modulator 2 operates according to the modulation code m 0 of Mathematical Expression (1), and the code demodulator 4 operates according to the demodulation code d 0 of Mathematical Expression (2).

As described above, according to FIGS. 7 and 8A , when the direct-current generated current I 1 is inputted to the code modulator 2 , it is possible to extract the demodulated current I 3 from the code demodulator 4 , the demodulated current I 3 being also a direct current similarly to the generated current I 1 inputted to the code modulator 2 . Therefore, according to the first embodiment, it is possible to modulate the direct-current generated current I 1 by code modulation into the alternating-current modulated current I 2 , and then, transmit the modulated current I 2 via the transmission path 3 , and then, demodulate the modulated current I 2 into the direct-current demodulated current I 3 .

FIG. 8B is a diagram showing an example of a modulation code of the code modulator 2 and a demodulation code of the code demodulator 4 in the power transmission system of FIG. 1 , as a second implementation example in which direct-current power is transmitted and received. When in each of the code sequences c 1 a and c 1 b , the number of bits of the code value “1” is equal to the number of bits of the code value “0”, the modulated current I 2 being modulated by code modulation and flowing in the transmission path 3 includes, in average, no direct-current component, but includes only an alternating-current component. However, in some code sequence, the number of bits of the code value “1” is different from the number of bits of the code value “0”, and thus, a direct-current component occurs. When using such a code sequence, by concatenating the code sequence with a code sequence of bits having code values inverted from those of corresponding bits, respectively, it is possible to generate a modulation code and a demodulation code, in each of which the number of bits of the code value “1” is equal to the number of bits of the code value “0”. According to the example of FIG. 8B , each of the modulation code m 1 and the demodulation code d 1 is a code sequence [c 1 a c 1 b ] which is a concatenation of the code sequence c 1 a and the code sequence c 1 b , and each of the modulation code m 2 and the demodulation code d 2 is a code sequence [c 1 b c 1 a ] which is a concatenation of the code sequence c 1 b and the code sequence c 1 a . As a result, the average value of the code-modulated current I 2 flowing in the transmission path 3 becomes zero, and the modulated current I 2 includes only an alternating-current component.

Note that the power generator 1 or the load 5 may be a power storage apparatus, such as a battery and a capacitor. When a power storage apparatus is incorporated in the power transmission system according to the present embodiment, it is possible to effectively utilize power generated during hours of low or no power consumption, and thus, improve overall power efficiency.

Second Embodiment

In the first embodiment, we have described the power transmission system which modulates and transmits a direct-current generated current by code modulation. Meanwhile, in a second embodiment, we describe a power transmission system which modulates and transmits an alternating-current generated current by code modulation.

The power transmission system according to the second embodiment includes a code modulator 2 A and a code demodulator 4 A, which will be described below with reference to FIGS. 10 and 11 , in place of the code modulator 2 and the code demodulator 4 of FIG. 1 . The other portions of the power transmission system according to the second embodiment are configured in a manner similar to that of the power transmission system according to the first embodiment.

FIG. 9 is a waveform diagram, where (a) to (c) show exemplary signal waveforms in the power transmission system according to the second embodiment. In FIG. 9 , (a) shows a signal waveform of a generated current I 1 ; (b) shows a signal waveform of a modulated current I 2 ; and (c) shows a signal waveform of a demodulated current I 3 . More specifically, FIG. 9 shows exemplary signal waveforms generated as follows: the code modulator 2 A modulates the (single-phase) alternating-current generated current I 1 by code modulation, and then, the modulated current I 2 is transmitted via a transmission path 3 , and then, the code demodulator 4 A demodulates the modulated current I 2 by code demodulation.

The power generator 1 generates the alternating-current generated current I 1 . For example, the alternating-current generated current I 1 has a rectangular waveform at a frequency of 5 kHz, which cyclically repeats positive and negative periods every 200 microseconds. Also in this case, the code modulator 2 A multiplies the generated current I 1 by a modulation code m 0 to generate the alternating modulated current I 2 , in a manner similar to the code modulation of the direct-current generated current I 1 as shown in FIG. 4 . The code demodulator 4 A multiplies the modulated current I 2 by a demodulation code d 0 identical to the modulation code m 0 to reproduce the alternating-current power generated by the power generator 1 , and supply the reproduced alternating-current power to a load 5 .

The frequency of the modulation code m 0 and the demodulation code d 0 is set to frequencies higher than the frequency of the generated current I 1 and the frequency of the demodulated current I 3 . According to the exemplary signal waveform of FIG. 9 , the alternating-current generated current I 1 ( FIG. 9( a ) ) is multiplied by the modulation code m 0 having a frequency of 35 kHz to generate the modulated current I 2 ( FIG. 9( b ) ) of the code-modulated wave. In this case, the duration of each bit of the modulation code m 0 is 1/(35 kHz)/2=14.2 microseconds.

Each bit of the modulation code m 0 and the demodulation code d 0 has a code value “1” or “−1”. In case of transmission of the alternating-current generated current I 1 , the meaning of the code value “1” or “−1” in a period when the generated current I 1 is positive (period from 0 to 100 microsecond in FIG. 9( a ) ) is different from that of a period when the generated current I 1 is negative (period from 100 to 200 microsecond in FIG. 9( a ) ). In the period when the generated current I 1 is positive, the code value “1” of the modulation code m 0 indicates that the code modulator 2 A outputs a current in the same direction as the direction of an inputted current, and the code value “−1” of the modulation code m 0 indicates that the code modulator 2 A outputs a current in the direction opposite to the direction of an inputted current. Similarly, in the period when the generated current I 1 is positive, the code value “1” of the demodulation code d 0 indicates that the code demodulator 4 A outputs a current in the same direction as the direction of an inputted current, and the code value “−1” of the demodulation code d 0 indicates that the code demodulator 4 A outputs a current in the direction opposite to the direction of an inputted current. In the period when the generated current I 1 is negative, the code value “1” of the modulation code m 0 indicates that the code modulator 2 A outputs a current in the direction opposite to the direction of an inputted current, and the code value “−1” of the modulation code m 0 indicates that the code modulator 2 A outputs a current in the same direction as the direction of an inputted current. Similarly, in the period when the generated current I 1 is negative, the code value “1” of the demodulation code d 0 indicates that the code demodulator 4 A outputs a current in the direction opposite to the direction of an inputted current, and the code value “−1” of the demodulation code d 0 indicates that the code demodulator 4 A outputs a current in the same direction as the direction of an inputted current.

For example, the modulation code m 0 and the demodulation code d 0 are given as follows.

m 0=[1 −1 1 1 1 −1 −1 −1 1 −1 −1 −1 1 1]  (6)

d 0 =m 0=[1 −1 1 1 1 −1 −1 −1 1 −1 −1 −1 1 1]  (7)

Similarly to the code demodulation according to the first embodiment, the modulated current I 2 of the code-modulated wave generated by the modulation code m 0 is multiplied by the demodulation code d 0 . This multiplication is denoted as follows.

m 0 ×d 0=[1 1 1 1 1 1 1 1 1 1 1 1 1 1]  (8)

As apparent from Mathematical Expression (8), the demodulated current I 3 ( FIG. 8( c ) ) is obtained, which is an alternating current similarly to the original generated current I 1 .

As described above, it is possible to achieve power transmission in an accurately synchronized manner, without power loss, by using the method of code modulation and code demodulation according to the present embodiment. In addition, it is possible to achieve efficient power transmission for a longer period, for example, by repeatedly using the modulation code m 0 and demodulation code d 0 as described above.

FIG. 10 is a block diagram showing a partial configuration of the code modulator 2 A of the power transmission system according to the second embodiment. The code modulator 2 A of FIG. 10 is provided with a code generation circuit 22 A and a code modulation circuit 23 A, in place of the code generation circuit 22 and the code modulation circuit 23 of FIG. 5 . The code modulator 2 A of FIG. 10 is further provided with a control circuit 20 and a communication circuit 21 similarly to the code modulator 2 of FIG. 5 , which are omitted in FIG. 10 for ease of illustration.

The code generation circuit 22 A and the code modulation circuit 23 A of FIG. 10 are different from the code generation circuit 22 and the code modulation circuit 23 of FIG. 7 in following points.

(1) The code generation circuit 22 A generates four modulation codes m 1 to m 4 in place of the two modulation codes m 1 and m 2 , and outputs the generated modulation codes m 1 to m 4 to the code modulation circuit 23 A.

(2) The code modulation circuit 23 A is provided with four bidirectional switch circuits SS 21 to SS 24 connected in a bridge configuration, in place of the unidirectional switch circuits SS 1 to SS 4 .

The code generation circuit 22 A generates and outputs the modulation codes m 1 to m 4 to the code modulation circuit 23 A under control of the control circuit 20 , in order to operate the code modulator 2 A according to the modulation code m 0 as described above. Each of the modulation codes m 1 to m 4 has code values “1” and “0”.

In the code modulation circuit 23 A, the switch circuit SS 21 is provided with the switch element S 1 of FIG. 7 to be turned on and off in response to the modulation code m 1 , and further provided with a switch element S 21 having directionality opposite to that of the switch element S 1 , connected in parallel to the switch element S 1 , and to be turned on and off in response to the modulation code m 3 . The switch circuit SS 22 is provided with the switch element S 2 of FIG. 7 to be turned on and off in response to the modulation code m 2 , and further provided with a switch element S 22 having directionality opposite to that of the switch element S 2 , connected in parallel to the switch element S 2 , and to be turned on and off in response to the modulation code m 4 . The switch circuit SS 23 is provided with the switch element S 3 of FIG. 7 to be turned on and off in response to the modulation code m 2 , and further provided with a switch element S 23 having directionality opposite to that of the switch element S 3 , connected in parallel to the switch element S 3 , and to be turned on and off in response to the modulation code m 4 . The switch circuit SS 24 is provided with the switch element S 4 of FIG. 7 to be turned on and off in response to the modulation code m 1 , and further provided with a switch element S 24 having directionality opposite to that of the switch element S 4 , connected in parallel to the switch element S 4 , and to be turned on and off in response to the modulation code m 3 . Each of the switch elements S 21 to S 24 is made of, for example, an MOS transistor. The code modulation circuit 23 A has ports T 1 and T 2 connected to a power generator 1 , and ports T 3 and T 4 connected to the transmission path 3 . Alternating-current power is inputted from the power generator 1 to the code modulation circuit 23 A. The code modulation circuit 23 A modulates the alternating-current power by code modulation, and then, outputs a code-modulated wave to the transmission path 3 .

FIG. 11 is a block diagram showing a partial configuration of the code demodulator 4 A of the power transmission system according to the second embodiment. The code demodulator 4 A of FIG. 11 is provided with a code generation circuit 32 A and a code demodulation circuit 33 A, in place of the code generation circuit 32 and the code demodulation circuit 33 of FIG. 6 . The code demodulator 4 A of FIG. 11 is further provided with a control circuit 30 and a communication circuit 31 similarly to the code demodulator 4 of FIG. 5 , which are omitted in FIG. 11 for ease of illustration.

The code generation circuit 32 A and the code demodulation circuit 33 A of FIG. 11 are different from the code generation circuit 32 and the code demodulation circuit 33 of FIG. 7 in following points.

(1) The code generation circuit 32 A generates four demodulation codes d 1 to d 4 in place of the two modulation codes d 1 and d 2 , and outputs the generated demodulation codes d 1 to d 4 to the code demodulation circuit 33 A.

(2) The code demodulation circuit 33 A is provided with four bidirectional switch circuits SS 31 to SS 34 connected in a bridge configuration, in place of the unidirectional switch circuits SS 11 to SS 14 .

The code generation circuit 32 A generates and outputs the demodulation codes d 1 to d 4 to the code demodulation circuit 33 A under control of the control circuit 30 , in order to operate the code demodulator 4 A according to the demodulation code d 0 as described above. Each of the demodulation codes d 1 and d 4 has code values “1” and “0”.

In the code demodulation circuit 33 A, the switch circuit SS 31 is provided with the switch element S 11 of FIG. 7 to be turned on and off in response to the demodulation code d 2 , and further provided with a switch element S 31 having directionality opposite to that of the switch element S 11 , connected in parallel to the switch element S 11 , and to be turned on and off in response to the demodulation code d 4 . The switch circuit SS 32 is provided with the switch element S 12 of FIG. 7 to be turned on and off in response to the demodulation code d 1 , and further provided with a switch element S 32 having directionality opposite to that of the switch element S 12 , connected in parallel to the switch element S 12 , and to be turned on and off in response to the demodulation code d 3 . The switch circuit SS 33 is provided with the switch element S 13 of FIG. 7 to be turned on and off in response to the demodulation code d 1 , and further provided with a switch element S 33 having directionality opposite to that of the switch element S 13 , connected in parallel to the switch element S 13 , and to be turned on and off in response to the demodulation code d 3 . The switch circuit SS 34 is provided with the switch element S 14 of FIG. 7 to be turned on and off in response to the demodulation code d 2 , and further provided with a switch element S 34 having directionality opposite to that of the switch element S 14 , connected in parallel to the switch element S 14 , and to be turned on and off in response to the demodulation code d 4 . Each of the switch elements S 31 to S 34 is made of, for example, an MOS transistor. The code demodulation circuit 33 A has ports T 11 and T 12 connected to the transmission path 3 , and ports T 13 and T 14 connected to the load 5 . An alternating-current code-modulated wave is inputted from the transmission path 3 to the code demodulation circuit 33 A. The code demodulation circuit 33 A demodulates the code-modulated wave by code demodulation into alternating-current demodulated power, and then outputs the demodulated power to the load 5 .

FIG. 12A is a diagram showing an example of a modulation code of the code modulator 2 A and a demodulation code of the code demodulator 4 A in the power transmission system according to the second embodiment, as a third implementation example in which alternating-current power is transmitted and received. More specifically, FIG. 12A shows an example of the modulation codes m 1 to m 4 inputted to the bidirectional switch circuits SS 21 to SS 24 of the code modulation circuit 23 A, and the demodulation codes d 1 to d 4 inputted to the bidirectional switch circuits SS 31 to SS 34 of the code demodulation circuit 33 A.

As shown in FIG. 12A , the modulation code m 1 and the demodulation code d 1 are identical to each other, and the modulation code m 2 and the demodulation code d 2 are identical to each other. Similarly, the modulation code m 3 and the demodulation code d 3 are identical to each other, and the modulation code m 4 and the demodulation code d 4 are identical to each other. In addition, similarly to the case of direct-current power transmission, code sequences c 1 a and c 1 b are configured such that when the code value of a certain bit of the code sequence c 1 a is “1”, the code value of a corresponding bit of the code sequence c 1 b is “0”; and when the code value of a certain bit of the code sequence c 1 a is “0”, the code value of a corresponding bit of the code sequence c 1 b is “1”.

FIG. 12A shows a case in which the duration of the code sequence c 1 a and the code sequence c 1 b is set to be equal to a half of the cycle of the alternating-current generated current I 1 . In a period when the alternating-current generated current I 1 flows in the positive direction (in example of FIG. 12A , first half period of each cycle), the modulation codes m 1 and m 2 are the code sequences c 1 a and c 1 b , respectively, and on the other hand, all code values of the modulation codes m 3 and m 4 are “0”. In a period when the alternating-current generated current I 1 flows in the negative direction (in example of FIG. 12A , second half period of each cycle), all the code values of the modulation codes m 1 and m 2 are “0”, and on the other hand, the modulation codes m 3 and m 4 are the code sequences c 1 a and c 1 b , respectively. Each of the modulation codes m 1 to m 4 for one cycle is generated by concatenating bits for a first half of each cycle with bits for a second half of each cycle. Accordingly, in the first half of each cycle, the switch elements S 1 to S 4 are turned on and off according to the modulation codes m 1 and m 2 , and on the other hand, the switch elements S 21 to S 24 are disconnected and no current flows. In addition, in the second half of each cycle, the switch elements S 1 to S 4 are disconnected and no current flows, and on the other hand, the switch elements S 21 to S 24 are turned on and off according to the modulation codes m 3 and m 4 . Similarly to the modulation codes m 1 to m 4 , each of the demodulation codes d 1 to d 4 for one cycle is generated by concatenating bits for the first half of each cycle with bits for the second half of each cycle.

Now, operation of the code modulation circuit 23 A is described.

At first, operation is described for a case in which the generated current I 1 flows at the input ports T 1 and T 2 in the positive direction, i.e., in a direction of solid arrows A 1 . In this case, when the switch elements S 1 and S 4 receiving the code value “1” of the modulation code m 1 are turned on, the switch elements S 2 and S 3 receiving the code value “0” of the modulation code m 2 are turned off. In addition, when the switch elements S 1 and S 4 receiving the code value “0” of the modulation code m 1 are turned off, the switch elements S 2 and S 3 receiving the code value “1” of the modulation code m 2 are turned on. Thus, when the switch elements S 1 and S 4 are turned on, and the switch elements S 2 and S 3 are turned off, the modulated current I 2 flows in the transmission path 3 in a positive direction, i.e., in a direction of the solid arrows A 1 . On the other hand, when the switch elements S 1 and S 4 are turned off, and the switch elements S 2 and S 3 are turned on, the modulated current I 2 flows in the transmission path 3 in a negative direction, i.e., in a direction of dotted arrows A 2 . Accordingly, when the current of positive period of the alternating-current generated current I 1 is inputted to the code modulation circuit 23 A, it is possible to transmit the alternating-current modulated current I 2 to the transmission path 3 , as shown in FIG. 9( b ) .

Next, operation is described for a case in which the generated current I 1 flows at the input ports T 1 and T 2 in a negative direction, i.e., in a direction of chain arrows B 1 . In this case, when the switch elements S 21 and S 24 receiving the code value “1” of the modulation code m 3 are turned on, the switch elements S 22 and S 23 receiving the code value “0” of the modulation code m 4 are turned off. In addition, when the switch elements S 21 and S 24 receiving the code value “0” of the modulation code m 3 are turned off, the switch elements S 22 and S 23 receiving the code value “1” of the modulation code m 4 are turned on. Thus, when the switch elements S 21 and S 24 are turned on, and the switch elements S 22 and S 23 are turned off, the modulated current I 2 flows in the transmission path 3 in a negative direction, i.e., in a direction of the chain arrows B 1 . On the other hand, when the switch elements S 21 and S 24 are turned off, and the switch elements S 22 and S 23 are turned on, the modulated current I 2 flows in the transmission path 3 in a positive direction, i.e., in a direction of two-dot chain arrows B 2 . Accordingly, when the current of negative period of the alternating-current generated current I 1 is inputted to the code modulation circuit 23 A, it is possible to transmit the alternating-current modulated current I 2 to the transmission path 3 , as shown in FIG. 9( b ) .

As described with reference to FIG. 10 , the code modulation circuit 23 A can generate the alternating-current modulated current I 2 , as shown in FIG. 9( b ) , in both the positive and negative periods of the alternating-current generated current I 1 .

Next, operation of the code demodulation circuit 33 A of FIG. 11 is described.

At first, we consider a case in which the generated current I 1 flows at the input ports T 1 and T 2 of the code modulation circuit 23 A in the positive direction, i.e., in the direction of the solid arrows A 1 . In this case, the alternating-current modulated current I 2 flowing in the positive and negative directions is inputted to the input ports T 11 and T 12 of the code demodulation circuit 33 A via the transmission path 3 . When the code demodulation circuit 33 A correctly performs demodulation operation, the demodulated current I 3 flows at the output ports T 13 and T 14 of the code demodulation circuit 33 A in a positive direction, i.e., in a direction of solid arrows C 1 . These operations are described below. In this case, all code values of the demodulation code d 3 and the demodulation code d 4 are “0”, and all the switch elements S 31 to S 34 are turned off.

At first, operation of the code demodulation circuit 33 A is described for a case in which the generated current I 1 flows at the input ports T 1 and T 2 of the code modulation circuit 23 A in the positive direction, and the modulated current I 2 flows at the input ports T 11 and T 12 of the code demodulation circuit 33 A in the positive direction, i.e., in the direction of the solid arrows C 1 . In this case, the code value of the code sequence c 1 a is “1”, and the code value of the code sequence c 1 b is “0”. Accordingly, the switch elements S 12 and S 13 receiving the code value “1” of the demodulation code d 1 are turned on, and the switch elements S 11 and S 14 receiving the code value “0” of the demodulation code d 2 are turned off. Therefore, the demodulated current I 3 flows at the output ports T 13 and T 14 in the positive direction, i.e., in the direction of the solid arrows C 1 .

Next, operation of the code demodulation circuit 33 A is described for a case in which the generated current I 1 flows at the input ports T 1 and T 2 of the code modulation circuit 23 A in the positive direction, and the modulated current I 2 flows at the input ports T 11 and T 12 of the code demodulation circuit 33 A in the negative direction, i.e., in the direction of dotted arrows C 2 . In this case, the code value of the code sequence c 1 a is “0”, and the code value of the code sequence c 1 b is “1”. Accordingly, the switch elements S 12 and S 13 receiving the code value “0” of the demodulation code d 1 are turned off, and the switch elements S 11 and S 14 receiving the code value “1” of the demodulation code d 2 are turned on. Therefore, the demodulated current I 3 flows at the output ports T 13 and T 14 in the positive direction, i.e., in the direction of the solid arrows C 1 . Accordingly, when the current of positive period of the alternating-current generated current I 1 is inputted to the code modulation circuit 23 A, the code demodulation circuit 33 A can output the demodulated current I 3 which is correctly demodulated with positive polarity, to the load 5 , as shown in FIG. 9( c ) .

Next, we consider a case in which the generated current I 1 flows at the input ports T 1 and T 2 of the code modulation circuit 23 A in the negative direction, i.e., in the direction of the chain arrows B 1 . Similarly to the above case, the alternating-current modulated current I 2 flowing in the positive and negative directions is inputted to the input ports T 11 and T 12 of the code demodulation circuit 33 A via the transmission path 3 . When the code demodulation circuit 33 A correctly performs demodulation operation, the demodulated current I 3 flows at the output ports T 13 and T 14 of the code demodulation circuit 33 A in the negative direction, i.e., in a direction of the dotted arrows C 2 . These operations are described below. In this case, all code values of the demodulation codes d 1 and d 2 are “0”, and all the switch elements S 11 to S 14 are turned off.

At first, described is operation of the code demodulation circuit 33 A for a case in which the generated current I 1 flows at the input ports T 1 and T 2 of the code modulation circuit 23 A in the negative direction, and the modulated current I 2 flows at the input ports T 11 and T 12 of the code demodulation circuit 33 A in the negative direction, i.e., in the direction of dotted arrows C 2 . In this case, the code value of the code sequence c 1 a is “1”, and the code value of the code sequence c 1 b is “0”. Accordingly, the switch elements S 32 and S 33 receiving the code value “1” of the demodulation code d 3 are turned on, and the switch elements S 31 and S 34 receiving the code value “0” of the demodulation code d 4 are turned off. Therefore, the demodulated current I 3 flows at the output ports T 13 and T 14 in the negative direction, i.e., in the direction of the dotted arrows C 2 .

Next, operation of the code demodulation circuit 33 A is described for a case in which the generated current I 1 flows at the input ports T 1 and T 2 of the code modulation circuit 23 A in the negative direction, and the modulated current I 2 flows at the input ports T 11 and T 12 of the code demodulation circuit 33 A in the positive direction, i.e., in the direction of the solid arrows C 1 . In this case, the code value of the code sequence c 1 a is “0”, and the code value of the code sequence c 1 b is “1”. Accordingly, the switch elements S 32 and S 33 receiving the code value “0” of the demodulation code d 3 are turned off, and the switch elements S 31 and S 34 receiving the code value “1” of the demodulation code d 4 are turned on. Therefore, the demodulated current I 3 flows at the output ports T 13 and T 14 in the negative direction, i.e., in the direction of the dotted arrows C 2 . Accordingly, when the current of negative period of the alternating-current generated current I 1 is inputted to the code modulation circuit 23 A, the code demodulation circuit 33 A can output the demodulated current I 3 which is correctly demodulated with negative polarity, to the load 5 , as shown in FIG. 9( c ) .

As described above, when using the modulation codes m 1 to m 4 and the demodulation codes d 1 to d 4 of FIG. 12A , equivalently, the code modulator 2 A operates according to the modulation code m 0 of Mathematical Expression (6), and the code demodulator 4 A operates according to the demodulation code d 0 of Mathematical Expression (7).

As described above, according to FIGS. 10, 11, and 12A , when the alternating-current generated current I 1 is inputted to the code modulator 2 A, it is possible to extract the demodulated current I 3 from the code demodulator 4 A, the demodulated current I 3 being also an alternating current similarly to the generated current I 1 inputted to the code modulator 2 A. Therefore, according to the second embodiment, it is possible to modulate the alternating-current generated current I 1 by code modulation into the alternating-current modulated current I 2 , and then, transmit the modulated current I 2 via the transmission path 3 , and then, demodulate the modulated current I 2 into the alternating-current demodulated current I 3 .

FIG. 15 is a diagram showing waveforms of a generated current, a modulated current, and a demodulated current, when using the modulation code and the demodulation code of FIG. 12A .

As described with reference to FIG. 10 , the code modulation circuit 23 A operates in one of the following operation modes (1) to (4) dependent on the direction of current at the input terminals T 1 and T 2 , and the direction of current outputted from the output terminals T 3 and T 4 .

(1) When a positive current (arrow A 1 ) is inputted into the input terminals T 1 and T 2 , the switch elements S 1 and S 4 are turned on, and the switch elements S 2 and S 3 are turned off, and therefore, a positive currents (arrow A 1 ) are outputted from the output terminals T 3 and T 4 .

(2) When a positive current (arrow A 1 ) is inputted into the input terminals T 1 and T 2 , the switch elements S 1 and S 4 are turned off, and the switch elements S 2 and S 3 are turned on, and therefore, a negative currents (arrow A 2 ) are outputted from the output terminals T 3 and T 4 .

(3) When a negative currents (arrow B 1 ) is inputted into the input terminals T 1 and T 2 , the switch elements S 21 and S 24 are turned on, and the switch elements S 22 and S 23 are turned off, and therefore, a negative currents (arrow B 1 ) are outputted from the output terminals T 3 and T 4 .

(4) When a negative currents (arrow B 1 ) is inputted into the input terminals T 1 and T 2 , the switch elements S 21 and S 24 are turned off, and the switch elements S 22 and S 23 are turned on, and therefore, a positive currents (arrow B 2 ) are outputted from the output terminals T 3 and T 4 .

The control circuit 20 of the code modulator 2 A determines an operation mode of the code modulation circuit 23 A, based on the direction of the current at the input terminals T 1 and T 2 , and the direction of the current outputted from the output terminals T 3 and T 4 . The code generation circuit 22 A generates a modulation code in accordance with the determined operation mode.

In addition, as described with reference to FIG. 11 , the code demodulation circuit 33 A operates in one of the following operation modes (5) to (8) dependent on the direction of current at the input terminals T 11 and T 12 , and the direction of current outputted from the output terminals T 13 and T 14 .

(5) When a positive currents (arrow C 1 ) is inputted into the input terminals T 11 and T 12 , the switch elements S 12 and S 13 are turned on, and the switch elements S 11 and S 14 are turned off, and therefore, a positive currents (arrow C 1 ) are outputted from the output terminals T 13 and T 14 .

(6) When a negative currents (arrow C 2 ) is inputted into the input terminals T 11 and T 12 , the switch elements S 12 and S 13 are turned off, and the switch elements S 11 and S 14 are turned on, and therefore, a positive currents (arrow C 1 ) are outputted from the output terminals T 13 and T 14 .

(7) When a negative currents (arrow C 2 ) is inputted into the input terminals T 11 and T 12 , the switch elements S 32 and S 33 are turned on, and the switch elements S 31 and S 34 are turned off, and therefore, a negative currents (arrow C 2 ) are outputted from the output terminals T 13 and T 14 .

(8) When a positive currents (arrow C 1 ) is inputted into the input terminals T 11 and T 12 , the switch elements S 32 and S 33 are turned off, and the switch elements S 31 and S 34 are turned on, and therefore, a negative currents (arrow C 2 ) are outputted from the output terminals T 13 and T 14 .

The control circuit 30 of the code demodulator 4 A determines an operation mode of the code demodulation circuit 33 A based on the direction of the current at the input terminals T 11 and T 12 , and the direction of the current outputted from the output terminals T 13 and T 14 . The code generation circuit 32 A generates a demodulation code in accordance with the determined operation mode.

Numerals “1” to “8” in FIG. 15 indicate operation modes (1) to (8), respectively. For example, as shown in FIG. 15 , power can be modulated and demodulated by changing the operation mode of the code modulation circuit 23 A and the operation mode of the code demodulation circuit 33 A.

FIG. 12B is a diagram showing an example of a modulation code of the code modulator 2 A and a demodulation code of the code demodulator 4 A in the power transmission system according to the second embodiment, as a fourth implementation example in which direct-current power is transmitted and received. In this case, in the code modulation circuit 23 A of FIG. 10 and the code demodulation circuit 33 A of FIG. 11 , all code values of the modulation codes m 3 and m 4 and the demodulation codes d 3 and d 4 are set to “0” as shown in FIG. 12B , and thus, the switch elements S 21 to S 24 and S 31 to S 34 are turned off. Thus, the code modulation circuit 23 A of FIG. 10 and the code demodulation circuit 33 A of FIG. 11 operate as the code modulation circuit 23 and the code demodulation circuit 33 of FIG. 7 , respectively. Accordingly, it is possible to achieve direct-current power transmission of FIG. 4 by generating the modulation codes m 1 and m 2 and the demodulation codes d 1 and d 2 from the code sequences c 1 a and c 1 b as shown in FIG. 12B . Thus, by changing the modulation codes m 1 to m 4 and the demodulation codes d 1 to d 4 , it is possible to achieve a favorable power transmission system capable of supporting both direct-current power transmission and alternating-current power transmission using the code modulation circuit 23 A of FIG. 10 and the code demodulation circuit 33 A of FIG. 11 .

The direct-current power generator 1 may be, for example, a photovoltaic power generator. The alternating-current power generator 1 may be, for example, a power generator provided with a turbine rotated by thermal power, hydraulic power, wind power, nuclear power, tidal power, or the like.

As described above, by using the modulation code and the demodulation code identical to each other, the power transmission system according to the second embodiment is capable of modulating and transmitting the direct-current generated current I 1 and demodulating the modulated current into the direct-current demodulated current I 3 , and is also capable of modulating and transmitting the alternating-current generated current I 1 and demodulating the modulated current into the alternating-current demodulated current I 3 . In addition, by using the demodulation code different from the modulation code, the power transmission system according to the second embodiment is capable of modulating and transmitting the direct-current generated current I 1 and demodulating the modulated current into the alternating-current demodulated current I 3 , and is also capable of modulating and transmitting the alternating-current generated current I 1 and demodulating the modulated current into the direct-current demodulated current I 3 .

Since the code modulation circuit 23 A of FIG. 10 and the code demodulation circuit 33 A of FIG. 11 are provided with the bidirectional switch circuits SS 21 to SS 24 and SS 31 to SS 34 , these circuits are reversible. More specifically, the code modulation circuit 23 A is also operable as a code demodulation circuit to demodulate a modulated current inputted from the ports T 3 and T 4 and output the demodulated current from the ports T 1 and T 2 . The code demodulation circuit 33 A is also operable as a code modulation circuit to modulate a generated current inputted from the ports T 13 and T 14 and output the modulated current from the ports T 11 and T 12 . Thus, it is possible to transmit power from the code demodulator 4 A provided with the code demodulation circuit 33 A, to the code modulator 2 A provided with the code modulation circuit 23 A.

FIGS. 10 to 11 show the example in which each of the bidirectional switch circuits SS 21 to SS 34 is made of a pair of switch elements connected in parallel such that currents flow in opposite directions (S 1 , S 21 ; S 2 , S 22 ; S 3 , S 23 ; S 4 , S 24 ; S 11 , S 31 ; S 12 , S 32 ; S 13 , S 33 ; S 14 , S 34 ). Alternatively, each of the bidirectional switch circuits SS 21 to SS 34 may be made of a pair of switch elements connected in series, as shown in FIGS. 13A to 14D (S 41 , S 51 ; S 42 , S 52 ; S 43 , S 53 ; S 44 , S 54 ). In each of FIGS. 13A to 14D , the direction from top to bottom is referred to as a “positive direction”, and the direction from bottom to top is referred to as a “negative direction”.

FIG. 13A is a circuit diagram showing a configuration of a bidirectional switch circuit SS 21 A for a code modulation circuit 23 A used in a power transmission system according to a modified embodiment of the second embodiment. The switch circuit SS 21 A of FIG. 13A corresponds to the switch circuit SS 21 of FIG. 10 , and is made of series connection of: (1) a switch element S 41 connected in parallel with a diode D 1 allowing a current to flow in the negative direction, and turned on and off in accordance with the modulation code m 1 ; and (2) a switch element S 51 connected in parallel with a diode D 11 allowing a current to flow in the positive direction, and turned on and off in accordance with the modulation code m 3 .

FIG. 13B is a circuit diagram showing a configuration of a bidirectional switch circuit SS 22 A for the code modulation circuit 23 A used in the power transmission system according to the modified embodiment of the second embodiment. The switch circuit SS 22 A of FIG. 13B corresponds to the switch circuit SS 22 of FIG. 10 , and is made of series connection of: (1) a switch element S 42 connected in parallel with a diode D 2 allowing a current to flow in the negative direction, and turned on and off in accordance with the modulation code m 2 ; and (2) a switch element S 52 connected in parallel with a diode D 12 allowing a current to flow in the positive direction, and turned on and off in accordance with the modulation code m 4 .

FIG. 13C is a circuit diagram showing a configuration of a bidirectional switch circuit SS 23 A for the code modulation circuit 23 A used in the power transmission system according to the modified embodiment of the second embodiment. The switch circuit SS 23 A of FIG. 13C corresponds to the switch circuit SS 23 of FIG. 10 , and is made of series connection of: (1) a switch element S 43 connected in parallel with a diode D 3 allowing a current to flow in the negative direction, and turned on and off in accordance with the modulation code m 2 ; and (2) a switch element S 53 connected in parallel with a diode D 13 allowing a current to flow in the positive direction, and turned on and off in accordance with the modulation code m 4 .

FIG. 13D is a circuit diagram showing a configuration of a bidirectional switch circuit SS 24 A for the code modulation circuit 23 A used in the power transmission system according to the modified embodiment of the second embodiment. The switch circuit SS 24 A of FIG. 13D corresponds to the switch circuit SS 24 of FIG. 10 , and is made of series connection of: (1) a switch element S 44 connected in parallel with a diode D 4 allowing a current to flow in the negative direction, and turned on and off in accordance with the modulation code m 1 ; and (2) a switch element S 54 connected in parallel with a diode D 14 allowing a current to flow in the positive direction, and turned on and off in accordance with the modulation code m 3 .

FIG. 14A is a circuit diagram showing a configuration of a bidirectional switch circuit SS 31 A for a code demodulation circuit 33 A used in the power transmission system according to the modified embodiment of the second embodiment. The switch circuit SS 31 A of FIG. 14A corresponds to the switch circuit SS 31 of FIG. 11 , and is made of series connection of: (1) a switch element S 61 connected in parallel with a diode D 31 allowing a current to flow in the positive direction, and turned on and off in accordance with the demodulation code d 2 ; and (2) a switch element S 71 connected in parallel with a diode D 21 allowing a current to flow in the negative direction, and turned on and off in accordance with the demodulation code d 4 .

FIG. 14B is a circuit diagram showing a configuration of a bidirectional switch circuit SS 32 A for the code demodulation circuit 33 A used in the power transmission system according to the modified embodiment of the second embodiment. The switch circuit SS 32 A of FIG. 14B corresponds to the switch circuit SS 32 of FIG. 11 , and is made of series connection of: (1) a switch element S 62 connected in parallel with a diode D 32 allowing a current to flow in the positive direction, and turned on and off in accordance with the demodulation code d 1 ; and (2) a switch element S 72 connected in parallel with a diode D 22 allowing a current to flow in the negative direction, and turned on and off in accordance with the demodulation code d 3 .

FIG. 14C is a circuit diagram showing a configuration of a bidirectional switch circuit SS 33 A for the code demodulation circuit 33 A used in the power transmission system according to the modified embodiment of the second embodiment. The switch circuit SS 33 A of FIG. 14C corresponds to the switch circuit SS 33 of FIG. 11 , and is made of series connection of: (1) a switch element S 63 connected in parallel with a diode D 33 allowing a current to flow in the positive direction, and turned on and off in accordance with the demodulation code d 1 ; and (2) a switch element S 73 connected in parallel with a diode D 23 allowing a current to flow in the negative direction, and turned on and off in accordance with the demodulation code d 3 .

FIG. 14D is a circuit diagram showing a configuration of a bidirectional switch circuit SS 34 A for the code demodulation circuit 33 A used in the power transmission system according to the modified embodiment of the second embodiment. The switch circuit SS 34 A of FIG. 14D corresponds to the switch circuit SS 34 of FIG. 11 , and is made of series connection of: (1) a switch element S 64 connected in parallel with a diode D 34 allowing a current to flow in the positive direction, and turned on and off in accordance with the demodulation code d 2 ; and (2) a switch element S 74 connected in parallel with a diode D 24 allowing a current to flow in the negative direction, and turned on and off in accordance with the demodulation code d 4 .

Referring to FIG. 13A to FIG. 14D , each of the switch elements S 41 to S 74 may be made of, for example, an MOS transistor. Parallel parasitic (body) diodes D 1 to D 34 of MOS transistors may be used. For example, when each of the switch circuits SS 21 A to SS 34 A of FIGS. 13A to 14D is implemented by a switch element of an MOS transistor and one diode, two MOS transistors and two diodes are required for each one of the bidirectional switch circuit SS 21 A to SS 34 A. Meanwhile, packaged MOS transistors are widely available, including a built-in diode having good reverse characteristics. When using such packaged MOS transistors, each of the bidirectional switch circuits SS 21 A to SS 34 A can be made of two switch elements, and thus, size can be reduced.

Third Embodiment

In the first and second embodiments, we have described the power transmission systems which transmit power from the one power generator 1 to the one load 5 . Meanwhile, in a third embodiment, we describe a power transmission system which transmits powers from a plurality of power generators to a plurality of loads.

FIG. 16 is a block diagram showing a configuration of a power transmission system according to the third embodiment. Referring to FIG. 16 , the power transmission system according to the third embodiment includes a plurality of power generators 1 - 1 and 1 - 2 , a plurality of code modulators 2 A- 1 and 2 A- 2 , a transmission path 3 , a plurality of code demodulators 4 A- 1 and 4 A- 2 , a plurality of loads 5 - 1 and 5 - 2 , and a controller 10 A.

The controller 10 A is provided with a control circuit 11 and a communication circuit 12 A. The control circuit 11 communicates with the code modulators 2 A- 1 and 2 A- 2 and the code demodulators 4 A- 1 and 4 A- 2 via the communication circuit 12 A, and controls operations of the code modulators 2 A- 1 and 2 A- 2 and the code demodulators 4 A- 1 and 4 A- 2 .

In the power transmission system of FIG. 16 , each of the code modulators 2 A- 1 and 2 A- 2 operates as a power transmitter apparatus, and each of the code demodulators 4 A- 1 and 4 A- 2 operates as a power receiver apparatus. Each code modulator of the code modulators 2 A- 1 and 2 A- 2 modulates first power to generate a code-modulated wave by code modulation using a modulation code based on a code sequence, and transmits the code-modulated wave to one of the code demodulators 4 A- 1 and 4 A- 2 via the transmission path 3 . Each one of the code demodulators 4 A- 1 and 4 A- 2 receives the code-modulated wave from one of the code modulators 2 A- 1 and 2 A- 2 via the transmission path 3 , and demodulates the received code-modulated wave to generate second power by code demodulation using a demodulation code based on a code sequence identical to the code sequence of the modulation code used for the code modulation. The first powers are, for example, powers generated by the power generators 1 - 1 and 1 - 2 , and are shown as generated currents I 11 and I 12 in FIG. 16 . The code-modulated wave is alternating-current power modulated by code modulation, and is shown as a modulated current I 2 in FIG. 16 . The second power are, for example, powers to be supplied to the loads 5 - 1 and 5 - 2 , and are shown as demodulated currents I 31 and I 32 in FIG. 16 .

In this case, the code modulators 2 A- 1 and 2 A- 2 and the code demodulators 4 A- 1 and 4 A- 2 of FIG. 16 are configured and operated similarly to the code modulator 2 A and the code demodulator 4 A according to the second embodiment.

The power transmission system of FIG. 16 is further provided with power meters 1 m - 1 , 1 m - 2 , 5 m - 1 , and 5 m - 2 . Each of the power meters 1 m - 1 and 1 m - 2 is first power measuring means which measures an amount of the first power. More specifically, each of the power meters 1 m - 1 and 1 m - 2 measures an amount of power generated by the power generators 1 - 1 and 1 - 2 and transmitted from the power generators 1 - 1 and 1 - 2 to the code modulators 2 A- 1 and 2 A- 2 . Each of the power meters 5 m - 1 and 5 m - 2 is second power measuring means which measures an amount of the second power. More specifically, each of the power meters 5 m - 1 and 5 m - 2 measures an amount of power transmitted from the code demodulators 4 A- 1 and 4 A- 2 to the loads 5 - 1 and 5 - 2 , and used by the loads 5 - 1 and 5 - 2 . The amounts of powers measured by the power meters 1 m - 1 , 1 m - 2 , 5 m - 1 , and 5 m - 2 are transmitted to the controller 10 A.

The controller 10 A controls operations of the code modulators 2 A- 1 and 2 A- 2 and the code demodulators 4 A- 1 and 4 A- 2 based on the amounts of powers received from the power meters 1 m - 1 , 1 m - 2 , 5 m - 1 , and 5 m - 2 . For example, the controller 10 A transmits control signals to the code modulators 2 A- 1 and 2 A- 2 and the code demodulators 4 A- 1 and 4 A- 2 , the control signals including synchronization signals for synchronizing the code modulators 2 A- 1 and 2 A- 2 and the code demodulators 4 A- 1 and 4 A- 2 to each other, thus achieving code modulation and code demodulation of power in an accurately synchronized manner.

The controller 10 A transmits the code sequences of the modulation codes, or information specifying the code sequences, to at least one of the code modulators 2 A- 1 and 2 A- 2 , which is to transmit power, and transmits the code sequences of the demodulation codes, or information specifying the code sequences, to at least one of the code demodulators 4 A- 1 and 4 A- 2 , which is to receive power. For example, when transmitting power from the code modulator 2 A- 1 to the code demodulator 4 A- 1 , the controller 10 A sets a modulation code to the code modulator 2 A- 1 , and a demodulation code to the code demodulator 4 A- 1 , based on one code sequence. When simultaneously transmitting power from the code modulator 2 A- 2 to the code demodulator 4 A- 2 , the controller 10 A sets a modulation code to the code modulator 2 A- 2 , and a demodulation code to the code demodulator 4 A- 2 , based on another different code sequence. When simultaneously transmitting powers from the plurality of code modulators 2 A- 1 and 2 A- 2 to the plurality of code demodulators 4 A- 1 and 4 A- 2 , a plurality of low-correlated (e.g., orthogonal) code sequences may be used.

Thus, it is possible to transmit powers from the plurality of power generators 1 - 1 and 1 - 2 to the plurality of loads 5 - 1 and 5 - 2 .

Now, we describe exemplary operations of the code modulators 2 A- 1 and 2 A- 2 and the code demodulators 4 A- 1 and 4 A- 2 for transmitting powers generated by the power generators 1 - 1 and 1 - 2 to the loads 5 - 1 and 5 - 2 .

In the third embodiment, we describe a case in which the power generators 1 - 1 and 1 - 2 output direct-current powers, direct-current power is inputted to the load 5 - 1 , and alternating-current power is inputted to the load 5 - 2 . That is, when transmitting power from the power generator 1 - 2 to the load 5 - 2 , direct-current power is converted into alternating-current power.

FIG. 17A is a diagram showing an example of a modulation code of the code modulator 2 A- 1 and a demodulation code of the code demodulator 4 A- 1 in the power transmission system of FIG. 16 according to the third embodiment, in which direct-current power is transmitted and received. In addition, FIG. 17B is a diagram showing an example of a modulation code of the code modulator 2 A- 2 and a demodulation code of the code demodulator 4 A- 2 in the power transmission system of FIG. 16 according to the third embodiment, in which direct-current power is transmitted and alternating-current power is received.

FIG. 17A shows modulation codes and demodulation codes inputted to the switch elements S 1 to S 44 of the code modulator 2 A- 1 and the code demodulator 4 A- 1 . In this case, modulation codes m 1 a to m 4 a correspond to the modulation codes m 1 to m 4 of the code modulation circuit 23 A of FIG. 10 , respectively, and demodulation codes d 1 a to d 4 a correspond to the demodulation codes d 1 to d 4 of the code demodulation circuit 33 A of FIG. 11 , respectively. In this case, as described with reference to FIG. 12B , by setting all the code values of the modulation codes m 3 a and m 4 a and the demodulation codes d 3 a and d 4 a to “0”, the switch elements S 21 to S 24 and S 31 to S 34 are turned off. In addition, the modulation codes m 1 a and m 2 a and the demodulation codes d 1 a and d 2 a are generated from the code sequence c 1 a and the code sequence c 1 b , as described with reference to FIG. 12B .

Further, FIG. 17B shows modulation codes and demodulation codes inputted to the switch elements S 1 to S 44 of the code modulator 2 A- 2 and the code demodulator 4 A- 2 . In this case, modulation codes m 1 a to m 4 a correspond to the modulation codes m 1 to m 4 of the code modulation circuit 23 A of FIG. 10 , respectively, and demodulation codes d 1 a to d 4 a correspond to the demodulation codes d 1 to d 4 of the code demodulation circuit 33 A of FIG. 11 , respectively. In this case, by setting all the code values of the modulation codes m 3 b and m 4 b to “0”, the switch elements S 21 to S 24 are turned off. In addition, the modulation codes m 1 b and m 2 b and the demodulation codes d 1 b to d 4 b are generated from the code sequence c 2 a and the code sequence c 2 b . The principle of code modulation and code demodulation of currents is similar to that of the first and second embodiments, and therefore, its explanation is omitted here.

Now, with reference to FIG. 18 , we describe an operation of transmitting powers from the plurality of power generators 1 - 1 and 1 - 2 to the plurality of loads 5 - 1 and 5 - 2 .

FIG. 18 are waveform diagrams, where (a) to (e) show exemplary signal waveforms of the power transmission system according to the third embodiment. In FIG. 18 , (a) shows a signal waveform of a generated current I 11 , (b) shows a signal waveform of a generated current I 12 , (c) shows a signal waveform of a modulated current I 2 , (d) shows a signal waveform of a demodulated current I 31 , and (e) shows a signal waveform of a demodulated current I 32 .

The code modulator 2 A- 1 modulates the direct-current generated current I 11 by code modulation into an alternating-current code-modulated wave. Similarly, the code modulator 2 A- 2 modulates the direct-current generated current I 12 by code modulation into an alternating-current code-modulated wave. As shown in FIG. 18( c ) , the code-modulated wave generated by the code modulator 2 A- 1 and the code-modulated wave generated by the code modulator 2 A- 2 are transmitted as the combined modulated current I 2 via the transmission path 3 .

As described above, the code modulators 2 A- 1 and 2 A- 2 have an identical configuration, and are configured in a manner similar to that of the code modulator 2 A of FIG. 10 . In addition, the code demodulators 4 A- 1 and 4 A- 2 also have an identical configuration, and are configured in a manner similar to that of the code demodulator 4 A of FIG. 11 . The difference between the code modulators 2 A- 1 and 2 A- 2 , and the difference between the code demodulators 4 A- 1 and 4 A- 2 reside in the use of different sets of the code sequences c 1 a and c 1 b , and the code sequences c 2 a and c 2 b . The code modulator 2 A- 1 and the code demodulator 4 A- 1 use the code sequences c 1 a and c 1 b , and the code modulator 2 A- 2 and the code demodulator 4 A- 2 use the code sequences c 2 a and c 2 b . In this case, the code sequences c 1 a and c 2 a are orthogonal to each other, and therefore, the code sequences c 1 b and c 2 b are also orthogonal to each other. In this case, Gold sequences of seven stages are adopted, and different Gold sequences are set to the code sequences c 1 a and c 2 a.

The code demodulators 4 A- 1 and 4 A- 2 can demodulate the modulated current I 2 to extract powers generated by the corresponding code modulators 2 A- 1 and 2 A- 2 , respectively, by using the orthogonal code sequences c 1 a and c 2 a . Accordingly, as shown in FIGS. 18( d ) and ( e ) , the generated currents I 11 and I 12 are inputted to the code modulators 2 A- 1 and 2 A- 2 , and then, the currents are transmitted as code-modulated waves, and then, the corresponding code demodulators 4 A- 1 and 4 A- 2 correctly demodulate and output the demodulated currents I 31 and I 32 . As a result, the demodulated currents I 31 and I 32 having desired waveforms (direct current or alternating current) and desired magnitudes are supplied to the loads 5 - 1 and 5 - 2 , respectively.

As described above, according to the present embodiment, it is possible to simultaneously perform two power transmissions via the one transmission path 3 in a multiplexed manner, and separate the transmitted powers from each other, by using the code modulators 2 A- 1 and 2 A- 2 and the code demodulators 4 A- 1 and 4 A- 2 . Accordingly, it is possible to achieve a favorable power transmission system capable of simultaneously transmitting currents of desired magnitudes from the two power generators 1 - 1 and 1 - 2 to the two loads 5 - 1 and 5 - 2 .

By measuring instantaneous powers at the code modulators 2 A- 1 and 2 A- 2 or the code demodulators 4 A- 1 and 4 A- 2 and comparing the instantaneous powers with the code sequences, it is possible to know which of the power generators 1 - 1 and 1 - 2 transmits power, which of the loads receives power, and what amount of power is transmitted. Accordingly, when a plurality of the different power generators 1 - 1 and 1 - 2 requiring different generation costs are connected, it is possible to conduct power business with electricity charges dependent on which of the power generators 1 - 1 and 1 - 2 transmits power. Alternatively, in case of a system having variable power transmission efficiency depending on which of the power generators 1 - 1 and 1 - 2 transmits power and which of the loads 5 - 1 and 5 - 2 receives the power, it is possible to achieve optimum power supply by managing and analyzing information on power transmission.

As described above, according to the present embodiment, it is possible to provide the power transmission system capable of efficiently supplying power from the one or more power generators 1 - 1 and 1 - 2 to the one or more loads 5 - 1 and 5 - 2 , by using the code modulators 2 A- 1 and 2 A- 2 and the code demodulators 4 A- 1 and 4 A- 2 .

In the above described embodiment, we indicated the example of the power transmission system including the two power generators 1 - 1 and 1 - 2 and the two loads 5 - 1 and 5 - 2 , but the present disclosure is not limited thereto. It is possible to provide power transmission systems including the one power generator 1 - 2 and the two or more loads 5 - 1 and 5 - 2 , or including two or more power generators 1 - 1 and 1 - 2 and the two or more loads 5 - 1 and 5 - 2 . In this case, it is possible to simultaneously perform a number of power transmissions using one transmission path 3 . Accordingly, it is possible to reduce costs for installation of the transmission path 3 , and reduce costs by reducing the number of transmission paths 3 , etc.

In the above described embodiment, we indicated the example in which each of the code modulators 2 A- 1 and 2 A- 2 of FIG. 16 is configured as the code modulation circuit 23 A of FIG. 10 , but the present disclosure is not limited thereto. For example, when the output powers from the power generators 1 - 1 and 1 - 2 are direct-current powers, each of the code modulators 2 A- 1 and 2 A- 2 may be configured as the code modulation circuit 23 of FIG. 7 . In addition, when the input powers to the loads 5 - 1 and 5 - 2 are direct-current powers, each of the code demodulators 4 A- 1 and 4 A- 2 may be configured as the code demodulation circuit 33 of FIG. 7 . In these cases, it is possible to simplify the circuit configurations of the code modulators 2 A- 1 and 2 A- 2 and the code demodulators 4 A- 1 and 4 A- 2 , and accordingly, there are advantageous effects of reducing the number of parts, reducing costs, and reducing size of the apparatuses.

In the third embodiment, we indicated the example of the power transmission system which transmits powers from two power generators each having direct-current output power, to one load having direct-current input power, and to one load having alternating-current input power, but the present disclosure is not limited thereto. The power transmission system may receive powers from any number of power generators each having direct-current output power, and from any number of power generators each having alternating-current output power. In addition, the power transmission system may supply powers to any number of loads each having direct-current input power, and to any number of loads each having alternating-current input power.

Photovoltaic power generation, which generates most of natural energy, generates direct-current power. On the other hand, wind power generation and geothermal power generation generate alternating-current power. In this case, since it is not desirable that both direct-current power supplies and alternating-current power supplies are connected to the same power network, according to conventional power transmission systems, all power generators (power supplies) and loads should be of only direct current or only alternating current.

On the other hand, according to the power transmission system according to the present embodiment, by using code modulation and code demodulation, it is possible simultaneously transmit powers from a direct-current power supply to a direct-current load, from a direct-current power supply to an alternating-current load, from an alternating-current power supply to a direct-current load, and from an alternating-current power supply to an alternating-current load, via one transmission path.

Thus, according to the first to third embodiments, it is possible to provide a favorable power transmission system capable of correctly perform code modulation and code demodulation of power, and further, capable of simultaneously performing a plurality of power transmissions in a multiplexed manner via one transmission path.

Fourth Embodiment

FIG. 19 is a block diagram showing a configuration of a power transmission system according to a fourth embodiment. Referring to FIG. 19 , the power transmission system according to the fourth embodiment is provided with a power generator 1 , a code modulator 2 B, a transmission path 3 , a code demodulator 4 B, a load 5 , and a controller 10 B.

The controller 10 B is provided with a control circuit 11 B and a communication circuit 12 . The control circuit 11 B communicates with the code modulator 2 B and the code demodulator 4 B via the communication circuit 12 , and controls operations of the code modulator 2 B and the code demodulator 4 B. The control circuit 11 B controls the code modulator 2 B and the code demodulator 4 B in a manner similar to that of the control circuit of the controller according to the first and second embodiments, and further executes a process for synchronizing the code modulator 2 B with the code demodulator 4 B.

FIG. 20 is a block diagram showing a configuration of the code modulator 2 B of FIG. 19 . The code modulator 2 B of FIG. 20 is provided with a control circuit 20 B, a communication circuit 21 , a code generation circuit 22 A, a code modulation circuit 23 A, and a current meter 2 m . The communication circuit 21 , the code generation circuit 22 A, and the code modulation circuit 23 A of FIG. 20 are configured in a manner similar to that of the corresponding components of the code modulator according to the second embodiment. The current meter 2 m is a measuring device which measures a current value of a generated current (input power inputted to the code modulator 2 B). The control circuit 20 B controls the code generation circuit 22 A and the code modulation circuit 23 A in a manner similar to that of the control circuit of the code modulator according to the second embodiment, and further executes a process for synchronizing the code modulator 2 B with the code demodulator 4 B.

FIG. 21 is a block diagram showing a configuration of the code demodulator 4 B of FIG. 19 . The code demodulator 4 B of FIG. 21 is provided with a control circuit 30 B, a communication circuit 31 , a code generation circuit 32 A, and a code demodulation circuit 33 A. The communication circuit 31 , the code generation circuit 32 A, and the code demodulation circuit 33 A of FIG. 21 are configured in a manner similar to that of the corresponding components of the code demodulator according to the second embodiment. The control circuit 30 B controls the code generation circuit 32 A and the code demodulation circuit 33 A in a manner similar to that of the control circuit of the code demodulator according to the second embodiment, and further executes a process for synchronizing the code modulator 2 B with the code demodulator 4 B.

In order to synchronize the code modulator 2 B with the code demodulator 4 B, at first, the control circuit 20 B of the code modulator 2 B synchronizes operation of the code modulation circuit 23 A with a phase of a generated current. To this end, the control circuit 20 B measures a current value of the generated current using the current meter 2 m , and determines an operation mode of the code modulation circuit 23 A based on the measured current value. On the other hand, the control circuit 30 B of the code demodulator 4 B can not determine a phase of a demodulated current based on a modulated current received via the transmission path 3 . Accordingly, the code modulator 2 B transmits information about the current value of the generated current to the code demodulator 4 B via the controller 10 B. Subsequently, the control circuit 30 B of the code demodulator 4 B determines an operation mode of the code demodulation circuit 33 A based on the received information about the current value of the generated current.

FIG. 22 is a sequence diagram showing generation of a modulation code and a demodulation code in the power transmission system of FIG. 19 .

In step S 101 , the control circuit 11 B of the controller 10 B assigns addresses to the code modulator 2 B and the code demodulator 4 B, respectively, to pair the code modulator 2 B with the code demodulator 4 B between which power is transmitted. In step S 102 , the control circuit 11 B of the controller 10 B transmits the addresses to the code modulator 2 B and the code demodulator 4 B via the communication circuit 12 , respectively. In step S 103 , the control circuit 20 B of the code modulator 2 B receives the address via the communication circuit 21 . In step S 104 , the control circuit 30 B of the code demodulator 4 B receives the address via the communication circuit 31 .

In step S 105 , the current meter 2 m measures the current value of the generated current. In step S 106 , the control circuit 20 B of the code modulator 2 B obtains the current value from the current meter 2 m . The control circuit 20 B may directly process an analog current value, or may convert the analog current value to a digital value for processing. In step S 107 , the control circuit 20 B judges a direction (i.e., polarity) of the current, and generates waveform information indicating variations of direction of the generated current over time. For example, the control circuit 20 B generates the waveform information indicating the variations of the direction of the generated current over time, by detecting moments at which the direction of the current value measured by the current meter 2 m changes. In step S 108 , the control circuit 20 B of the code modulator 2 B transmits the waveform information to the controller 10 B via the communication circuit 21 . In step S 109 , the control circuit 11 B of the controller 10 B relays the waveform information received from the code modulator 2 B to transmit to the code demodulator 4 B, via the communication circuit 12 . In step S 110 , the control circuit 30 B of the code demodulator 4 B receives the waveform information via the communication circuit 31 .

In step S 111 , the control circuit 20 B of the code modulator 2 B determines an operation mode of the code modulation circuit 23 A based on the waveform information. In step S 112 , the control circuit 20 B generates a modulation code using the code generation circuit 22 A.

In step S 113 , the control circuit 30 B of the code demodulator 4 B determines an operation mode of the code demodulation circuit 33 A based on the waveform information. In step S 114 , the control circuit 30 B generates a demodulation code using the code generation circuit 32 A.

Subsequently, the code modulator 2 B and the code demodulator 4 B transmit and receive power using the generated modulation code and demodulation code, respectively.

According to the operation of FIG. 22 , the code modulator 2 B and the code demodulator 4 B can determine appropriate operation modes of the code modulator 2 B and the code demodulator 4 B in synchronization with the phase of the generated current, and surely synchronize with each other.

The control circuit 20 B of the code modulator 2 B may use either a normal comparator or a hysteresis comparator for judging the direction of the current in step S 107 .

If the cycle of the generated current is fixed, then it is not necessary to judge the direction of the current for each cycle. For example, the waveform information indicating the variations of the direction of the generated current over time may be generated during initialization of the code modulator 2 B.

On the other hand, when the cycle of the generated current varies, for example, when a motor's regenerative current is used as a power supply, the following problems may arise. As described above, the current meter 2 m measures the current value of the generated current, the control circuit 20 B of the code modulator 2 B generates the waveform information, and thereafter, the code modulator 2 B transmits the waveform information to the code demodulator 4 B via the controller 10 B. In this case, the control circuit 30 B of the code demodulator 4 B may be unable to determine a correct operation mode due to a delay of signal transmission. When a motor's regenerative current is used as power supply, the delay should be sequentially compensated using, for example, hysteresis control. The control circuit 20 B generates waveform information indicating the variations of the direction of the generated current over time, not by detecting moments at which of the direction of the current value changes, but by predicting moments at which the direction of the generated current changes, based on the current value.

FIG. 23 is a sequence diagram showing a modified embodiment of generation of a modulation code and a demodulation code in the power transmission system of FIG. 19 . Steps S 101 to S 106 and S 108 to S 114 of FIG. 23 are similar to the corresponding steps of FIG. 22 .

In step S 121 , the control circuit 11 B of the controller 10 B measures a delay of signal transmission and a delay of power transmission. In step S 122 , the control circuit 11 B transmits delay information to the code demodulator 4 B via the communication circuit 12 . In step S 123 , the control circuit 30 B of the code demodulator 4 B receives the delay information from the communication circuit 31 .

The control circuit 20 B of the code modulator 2 B executes step S 107 A, instead of step S 107 of FIG. 22 . In step S 107 A, the control circuit 20 B predicts zero-crossing moments of the current, and generates waveform information indicating variations of direction of the generated current over time.

In step S 124 , the control circuit 30 B of the code demodulator 4 B compensates for a delay based on the delay information, before determining an operation mode of a code demodulation circuit 33 A. For example, the control circuit 30 B compensates for the delay so as to reduce the delay of the code demodulation circuit 33 A from a code modulation circuit 23 A.

According to the operation of FIG. 23 , the code modulator 2 B and the code demodulator 4 B can determine appropriate operation modes of the code modulator 2 B and the code demodulator 4 B in synchronization with the phase of the generated current, and surely synchronize with each other.

The current meter 2 m is not limited to be provided outside the code modulator 2 B as shown in FIG. 19 , but may be integrated with or built in the code modulator 2 B.

It is not essential that the code modulator 2 B transmits the waveform information to the code demodulator 4 B as shown in FIGS. 22 and 23 . Alternatively, the control circuit 20 B of code modulator 2 B may determine the operation mode of the code demodulation circuit 33 A of the code demodulator 4 B, and the code modulator 2 B notifies the code demodulator 4 B of the determined operation mode.

Fifth Embodiment

A power transmission system according to a fifth embodiment is configured in a manner similar to that of the power transmission system of FIG. 19 . According to the fourth embodiment, the code modulator 2 B generates the waveform information. On the other hand, according to the fifth embodiment, the controller 10 B generates the waveform information.

FIG. 24 is a sequence diagram showing generation of a modulation code and a demodulation code in the power transmission system according to the fifth embodiment. Steps S 101 to S 106 and S 111 to S 114 of FIG. 24 are similar to the corresponding steps of FIG. 22 .

In step S 131 , a control circuit 20 B of a code modulator 2 B transmits a current value to the controller 10 B via a communication circuit 21 . In step S 132 , a control circuit 11 B of the controller 10 B receives the current value via a communication circuit 12 . In step S 133 , the control circuit 11 B judges a direction of the current, and generates waveform information indicating variations of direction of the generated current over time, in a manner similar to that of step S 107 of FIG. 22 . In step S 134 , the control circuit 11 B transmits waveform information to the code modulator 2 B and a code demodulator 4 B via the communication circuit 12 . In step S 135 , the control circuit 20 B of the code modulator 2 B receives the waveform information via the communication circuit 21 . In step S 136 , a control circuit 30 B of the code demodulator 4 B receives the waveform information via a communication circuit 31 .

According to the operation of FIG. 24 , the code modulator 2 B and the code demodulator 4 B can determine appropriate operation modes of the code modulator 2 B and the code demodulator 4 B in synchronization with the phase of the generated current, and surely synchronize with each other.

FIG. 25 is a sequence diagram showing generation of a modulation code and a demodulation code in a power transmission system according to a modified embodiment of the fifth embodiment. Steps S 101 to S 106 , S 111 to S 114 , S 131 to S 132 , and S 134 to S 136 of FIG. 25 are similar to the corresponding steps of FIG. 24 .

In step S 121 , the control circuit 11 B of the controller 10 B measures a delay of signal transmission and a delay of power transmission. In step S 122 , the control circuit 11 B transmits delay information to the code modulator 2 B and the code demodulator 4 B via the communication circuit 12 . In step S 125 , the control circuit 20 B of the code modulator 2 B receives the delay information via the communication circuit 21 . In step S 123 , the control circuit 30 B of the code demodulator 4 B receives the delay information via the communication circuit 31 .

The control circuit 11 B of the controller 10 B executes step S 133 A, instead of step S 133 of FIG. 24 . In step S 133 A, the control circuit 11 B predicts zero-crossing moments of the current, and generates waveform information indicating variations of direction of the generated current over time.

In step S 126 , the control circuit 20 B of the code modulator 2 B compensates for a delay based on the delay information, before determining an operation mode of a code modulation circuit 23 A. In step S 124 , the control circuit 30 B of the code demodulator 4 B compensates for a delay based on the delay information, before determining an operation mode of a code demodulation circuit 33 A.

According to the operation of FIG. 25 , the code modulator 2 B and the code demodulator 4 B can determine appropriate operation modes of the code modulator 2 B and the code demodulator 4 B in synchronization with the phase of the generated current, and surely synchronize with each other.

In the power transmission system according to the fifth embodiment, the current meter 2 m may be directly connected to the controller 10 B, instead of being connected to the code modulator 2 B.

Sixth Embodiment

A power transmission system according to a sixth embodiment is configured in a manner similar to that of the power transmission system of FIG. 19 . According to the fourth embodiment, the code modulator 2 B generates the waveform information, and according to the fifth embodiment, the controller 10 B generates the waveform information. On the other hand, according to the sixth embodiment, both the code modulator 2 B and the code demodulator 4 B generate the wave information.

FIG. 26 is a sequence diagram showing generation of a modulation code and a demodulation code in the power transmission system according to the sixth embodiment. Steps S 101 to S 106 and S 111 to S 114 of FIG. 26 are similar to the corresponding steps of FIG. 22 .

In step S 141 , a control circuit 20 B of the code modulator 2 B transmits a current value via a communication circuit 21 . In step S 142 , a control circuit 11 B of a controller 10 B relays the current value received from the code modulator 2 B to transmit to the code demodulator 4 B, via a communication circuit 12 . In step S 143 , a control circuit 30 B of the code demodulator 4 B receives the current value via a communication circuit 31 .

In step S 144 , the control circuit 20 B of the code modulator 2 B judges a direction of the current, and generates waveform information indicating variations of direction of the generated current over time.

In step S 145 , the control circuit 30 B of the code demodulator 4 B judges a direction of the current, and generates waveform information indicating variations of direction of the generated current over time.

According to the operation of FIG. 26 , the code modulator 2 B and the code demodulator 4 B can determine appropriate operation modes of the code modulator 2 B and the code demodulator 4 B in synchronization with the phase of the generated current, and surely synchronize with each other.

FIG. 27 is a sequence diagram showing generation of a modulation code and a demodulation code in a power transmission system according to a modified embodiment of the sixth embodiment. Steps S 101 to S 106 , S 111 to S 114 , and S 141 to S 143 of FIG. 27 are similar to the corresponding steps of FIG. 26 , and steps S 121 to S 124 of FIG. 27 are similar to the corresponding steps of FIG. 23 . A control circuit 20 B of the code modulator 2 B executes step S 144 A, instead of step S 144 of FIG. 26 . In step S 144 A, the control circuit 20 B predicts zero-crossing moments of the current, and generates waveform information indicating variations of phase of the generated current over time. A control circuit 30 B of the code demodulator 4 B executes step S 145 A, instead of step S 145 of FIG. 26 . In step S 145 A, the control circuit 30 B predicts zero-crossing moments of the current, and generates waveform information indicating variations of phase of the generated current over time.

According to the operation of FIG. 27 , the code modulator 2 B and the code demodulator 4 B can determine appropriate operation modes of the code modulator 2 B and the code demodulator 4 B in synchronization with the phase of the generated current, and surely synchronize with each other.

Seventh Embodiment

A power transmission system according to a seventh embodiment is configured in a manner similar to that of the power transmission system of FIG. 19 . When a generated current has a fixed cycle, a phase of the current may be determined, instead of detecting or predicting moments at which the direction of a current value changes.

FIG. 28 is a sequence diagram showing generation of a modulation code and a demodulation code in the power transmission system according to the seventh embodiment. Steps S 101 to S 106 and S 111 to S 114 of FIG. 28 are similar to the corresponding steps of FIG. 22 .

A control circuit 20 B of a code modulator 2 B executes step S 107 B, instead of step S 107 of FIG. 22 . In step S 107 B, the control circuit 20 B judges a phase of a current, and generates waveform information indicating variations of phase of a generated current over time.

According to the operation of FIG. 28 , the code modulator 2 B and the code demodulator 4 B can determine appropriate operation modes of the code modulator 2 B and the code demodulator 4 B in synchronization with the phase of the generated current, and surely synchronize with each other.

FIG. 29 is a sequence diagram showing generation of a modulation code and a demodulation code in a power transmission system according to a modified embodiment of the seventh embodiment. Steps S 101 to S 106 and S 108 to S 114 of FIG. 29 are similar to the corresponding steps of FIG. 28 .

In step S 121 , a control circuit 11 B of a controller 10 B measures a delay of signal transmission and a delay of power transmission. In step S 122 , the control circuit 11 B transmits delay information to the code demodulator 4 B via a communication circuit 12 . In step S 123 , the control circuit 30 B of the code demodulator 4 B receives the delay information via the communication circuit 31 .

A control circuit 20 B of the code modulator 2 B executes step S 107 C, instead of step S 107 B of FIG. 28 . In step S 107 C, the control circuit 20 B predicts zero-crossing moments of the current, and generates waveform information indicating variations of phase of the generated current over time.

In step S 124 , the control circuit 30 B of the code demodulator 4 B compensates for a delay based on the delay information, before determining an operation mode of a code demodulation circuit 33 A.

According to the operation of FIG. 29 , the code modulator 2 B and the code demodulator 4 B can determine appropriate operation modes of the code modulator 2 B and the code demodulator 4 B in synchronization with the phase of the generated current, and surely synchronize with each other.

Eighth Embodiment

FIG. 30 is a block diagram showing a configuration of a code modulator 2 B of a power transmission system according to an eighth embodiment. A code modulator 2 B (or code modulator 2 or 2 A of the first to third embodiments) may be connected to a power generator 1 via a reactor L 1 . By providing the reactor L 1 , switching noise occurring in the code modulation circuit 23 A is less likely to arrive at the power generator 1 . Accordingly, it is possible to improve quality and safety of power transmission.

When the code modulator 2 B is connected to the power generator 1 via the reactor L 1 , a current meter 2 m is connected between the reactor and the power generator 1 . Accordingly, the current meter 2 m can accurately detect variations of direction of a generated current.

In the third to eighth embodiments, a plurality of code modulators may use the same code sequence, and a plurality of code demodulators may use the same code sequence. Thus, one code modulator may transmit powers to a plurality of code demodulators, a plurality of code modulators may transmit powers to one code demodulator, and a plurality of code modulators may transmit powers to a plurality of code demodulators.

In the first to eighth embodiments, we have indicated the example in which power is transmitted using code modulation and code demodulation of current, but the power transmission is not limited thereto. Power may be transmitted using code modulation and code demodulation of direct-current or alternating-current voltage. In this case, similar advantageous effects can be achieved.

In the fourth to eighth embodiments, we have described measurement of a current value of a generated current using the current meter 2 m . Alternatively, a voltage value associated with source power may be measured to generate waveform information indicating variations of direction of voltage over time.

A power transmitter apparatus, a power receiver apparatus, and a power transmission system according to several aspects of the present disclosure have following configurations.

According to a power transmitter apparatus of a first aspect, a power transmitter apparatus transmits power to at least one power receiver apparatus via a transmission path. The power transmitter apparatus is provided with: a measuring device that measures a current value or voltage value associated with input power inputted to the power transmitter apparatus; a code modulation circuit that modulates the input power to generate a code-modulated wave by code modulation using a modulation code based on a code sequence, and transmits the code-modulated wave to the power receiver apparatus via the transmission path; and a control circuit that controls the code modulation circuit. The code modulation circuit has operation modes different from each other depending on a direction of the input power, and a direction of the code-modulated wave to be generated. The control circuit generates waveform information indicating variations of direction of the input power over time, based on the current value or voltage value measured by the measuring device, and determines the operation mode of the code modulation circuit based on the waveform information.

According to a power transmitter apparatus of a second aspect, in the power transmitter apparatus of the first aspect, the control circuit generates the waveform information indicating the variations of the direction of the input power over time, by detecting moments at which the direction of the current value or voltage value measured by the measuring device changes.

According to a power transmitter apparatus of a third aspect, in the power transmitter apparatus of the first aspect, the control circuit generates the waveform information indicating the variations of the direction of the input power over time, by predicting moments at which the direction of the input power changes, based on the current value or voltage value measured by the measuring device.

According to a power transmitter apparatus of a fourth aspect, in the power transmitter apparatus of one of the first to third aspects, the power transmitter apparatus is connected to a power supply for the input power, via a reactor. The measuring device is connected between the reactor and the power supply.

According to a power transmitter apparatus of a fifth aspect, a power transmitter apparatus transmits power to at least one power receiver apparatus via a transmission path. The power transmitter apparatus is provided with: a communication circuit that receives waveform information indicating variations of direction of input power over time, the input power being inputted to the power transmitter apparatus; a code modulation circuit that modulates the input power to generate a code-modulated wave by code modulation using a modulation code based on a code sequence, and transmits the code-modulated wave to the at least one power receiver apparatus via the transmission path; and a control circuit that controls the code modulation circuit. The code modulation circuit has operation modes different from each other depending on a direction of the input power, and a direction of the code-modulated wave to be generated. The control circuit determines the operation mode of the code modulation circuit based on the waveform information.

According to a power transmitter apparatus of a sixth aspect, in the power transmitter apparatus of one of the first to fifth aspects, the control circuit compensates for a delay occurring due to transmission of the waveform information.

According to a power receiver apparatus of a seventh aspect, a power receiver apparatus receives a code-modulated wave from at least one power transmitter apparatus via a transmission path, the code-modulated wave including power modulated by code modulation using a modulation code based on a code sequence. The power receiver apparatus is provided with: a communication circuit that receives a current value or voltage value associated with input power inputted to the power transmitter apparatus; a code demodulation circuit that demodulates the received code-modulated wave to generate output power by code demodulation using a demodulation code based on a code sequence identical to the code sequence of the modulation code used for the code modulation, and supplies the demodulated power to the load; and a control circuit that controls the code demodulation circuit. The code demodulation circuit has operation modes different from each other depending on a direction of the code-modulated wave, and a direction of the output power to be generated. The control circuit generates waveform information indicating variations of direction of the input power over time, based on the current value or voltage value received by the communication circuit, and determines the operation mode of the code demodulation circuit based on the waveform information.

According to a power receiver apparatus of an eighth aspect, in the power receiver apparatus of the seventh aspect, the control circuit generates the waveform information indicating the variations of the direction of the input power over time, by detecting moments at which the direction of the current value or voltage value received by the communication circuit changes.

According to a power receiver apparatus of a ninth aspect, in the power receiver apparatus of the seventh aspect, the control circuit generates the waveform information indicating the variations of the direction of the input power over time, by predicting moments at which the direction of the input power changes, based on the current value or voltage value received by the communication circuit.

According to a power receiver apparatus of a 10th aspect, a power receiver apparatus receives a code-modulated wave from at least one power transmitter apparatus via a transmission path, the code-modulated wave including power modulated by code modulation using a modulation code based on a code sequence. The power receiver apparatus is provided with: a communication circuit that receives waveform information indicating variations of direction of input power over time, the input power being inputted to the power transmitter apparatus; a code demodulation circuit that demodulates the received code-modulated wave to generate output power by code demodulation using a demodulation code based on a code sequence identical to the code sequence of the modulation code used for the code modulation, and supplies the demodulated power to the load; and a control circuit that controls the code demodulation circuit. The code demodulation circuit has operation modes different from each other depending on a direction of the code-modulated wave, and a direction of the output power to be generated. The control circuit determines the operation mode of the code demodulation circuit based on the waveform information.

According to a power receiver apparatus of a 11th aspect, in the power receiver apparatus of one of the seventh to 10th aspects, the control circuit compensates for a delay occurring due to transmission of the waveform information.

According to a controller of a 12th aspect, a controller is provided for a power transmission system, the power transmission system including a power transmitter apparatus of the fifth aspect, and a power receiver apparatus of the 10th aspect. The controller is provided with: a communication circuit that receives a current value or voltage value associated with input power inputted to the power transmitter apparatus; and a control circuit. The control circuit of the controller generates waveform information indicating variations of direction of the input power over time, based on the current value or voltage value received by the communication circuit of the controller, and transmits the waveform information to the power transmitter apparatus and the power receiver apparatus via the communication circuit.

According to a controller of a 13th aspect, in the controller of the 12th aspect, the control circuit generates the waveform information indicating the variations of the direction of the input power over time, by detecting moments at which the direction of the current value or voltage value received by the communication circuit changes.

According to a controller of a 14th aspect, in the controller of the 12th aspect, the control circuit generates the waveform information indicating the variations of the direction of the input power over time, by predicting moments at which the direction of the input power changes, based on the current value or voltage value received by the communication circuit.

According to a power transmission system of a 15th aspect, a power transmission system includes: a power transmitter apparatus of one of the first to fourth aspects; and a power receiver apparatus of the 10th aspect.

According to a power transmission system of a 16th aspect, a power transmission system includes: a power transmitter apparatus of the fifth aspect; a power receiver apparatus of the 10th aspect; and a controller of one of the 12th to 14th aspects.

According to a power transmission system of a 17th aspect, a power transmission system includes: a power transmitter apparatus of one of the first to fourth aspects; and a power receiver apparatus of one of the seventh to ninth aspects.

A power transmission system according to the present disclosure is suitable for power transmission from a power generator, such as solar power generation, wind power generation, and hydroelectric power generation, to a load, such as a railway and an electric vehicle (EV).

A power transmission system according to the present disclosure can achieve efficient and reliable power transmission in an environment including a combination of direct-current power supplies, such as rechargeable batteries, solar power generation, fuel cells, etc., and/or alternating-current power supplies, such as commercial power, regenerative power of a motor, etc.

1 , 1 - 1 to 1 - 2 : POWER GENERATOR

1 m , 1 m - 1 , 1 m - 2 : POWER METER

2 , 2 A, 2 A- 1 to 2 A- 2 , 2 B: CODE MODULATOR

3 : TRANSMISSION PATH

4 , 4 A, 4 A- 1 to 4 A- 2 , 4 B: CODE DEMODULATOR

5 , 5 - 1 to 5 - 2 : LOAD

5 m , 5 m - 1 to 5 m - 2 : POWER METER

10 , 10 A to 10 B: CONTROLLER

11 , 11 B: CONTROL CIRCUIT

12 , 12 A: COMMUNICATION CIRCUIT

20 , 20 B: CONTROL CIRCUIT

21 : COMMUNICATION CIRCUIT

22 , 22 A: CODE GENERATION CIRCUIT

23 , 23 A: CODE MODULATION CIRCUIT

30 , 30 B: CONTROL CIRCUIT

31 : COMMUNICATION CIRCUIT

32 , 32 A: CODE GENERATION CIRCUIT

33 , 33 A: CODE DEMODULATION CIRCUIT

D 1 to D 34 : DIODE

S 1 to S 74 : SWITCH ELEMENT

SS 1 to SS 34 , SS 21 A to SS 34 A: SWITCH CIRCUIT

T 1 to T 14 : PORT