Inverter system

The present application claims priority to Chinese Patent Application No. 201920592419.9, titled “INVERTER SYSTEM”, filed on Apr. 26, 2019, with the China National Intellectual Property Administration, which is incorporated herein by reference in its entirety.

The present disclosure relates to the technical field of power electronics technology, and in particular, to an inverter system.

A conventional inverter system increases a power level of the inverter system without changing stress of switches by directly connecting multiple inverter modules in parallel. However, when currents flowing in the multiple inverter modules are not uniform, it is inevitable that a current flowing in an individual inverter module exceeds a current-carrying limit of said inverter module, which will cause an overcurrent damage of said inverter module.

In view of the above, the present disclosure provides an inverter system in which the magnitudes of currents flowing through the inverter modules are substantially equal.

An inverter system includes multiple inverter modules connected in parallel, where input terminals of all the inverter modules are connected to a same direct current input bus, and output terminals of all the inverter modules are connected to a same alternating current output bus, and an input contact S 1 of the direct current input bus and an output contact S 2 of the alternating current output bus are located in a manner that a difference between impedances of each two branches between S 1 and S 2 is less than or equal to a preset value.

In an embodiment, the multiple inverter modules are sequentially arranged in a vertical direction, S 2 is located within a preset range centered on an upper left corner of the inverter system, and S 1 is located within a preset range centered on a lower right corner of the inverter system.

In an embodiment, the multiple inverter module are sequentially arranged in a vertical direction, S 2 is located within a preset range centered on a lower left corner of the inverter system, and S 1 is located within a preset range centered on an upper right corner of the inverter system.

In an embodiment, the inverter module has an I-type three-level circuit topology including a first sub-module, a second sub-module and a third sub-module,

where the first sub-module has a positive input terminal connected to a positive terminal of the direct current input bus, a negative input terminal connected to a neutral point of the direct current input bus, and an output terminal connected to a positive input terminal of the third sub-module, and

the second sub-module has a positive input terminal connected to the neutral point of the direct current input bus, a negative input terminal connected to a negative terminal of the direct current input bus, and an output terminal connected to a negative input terminal of the third sub-module.

In an embodiment, the inverter system further includes a first circulation bus and a second circulation bus, where the first circulation bus is connected to the output terminal of each first sub-module, and the second circulation bus is connected to the output terminal of each second sub-module.

In an embodiment, heat dissipation fins with sparse and dense regions are provided on a housing of the inverter,

where the multiple inverter modules in the inverter system are sequentially arranged in a vertical direction, and cold air enters through a bottom of the inverter system and flows out through a top of the inverter system; and

the heat dissipation fins are sparse near a cold air side, and are dense near a hot air side.

In an embodiment, each of the multiple inverter modules is provided with multiple heat pipes, and the heat pipes transfer heat that is not taken away by cold air to an area without heat generation or with less heat generation in the inverter module.

In an embodiment, the multiple inverter modules in the inverter system are sequentially arranged in a vertical direction, and cold air enters through a bottom of the inverter system and flows out through a top of the inverter system;

the first sub-module and the second sub-module are arranged in a vertical direction;

in a horizontal direction of the inverter module, the first sub-module and the second sub-module are arranged at one side in the inverter module, and the third sub-module is arranged at another side in the inverter module; and

first, second, third and fourth heat pipes are provided in the inverter module, where the first heat pipe has a first end arranged on a surface of the first sub-module and a second end arranged in an area where the third sub-module is not installed, the second heat pipe has a third end arranged on the surface of the first sub-module and a fourth end arranged in the area where the third sub-module is not installed, the third heat pipe has a fifth end arranged on a surface of the second sub-module and a sixth end arranged on a surface of the third sub-module, and the fourth heat pipe has a seventh end arranged on the surface of the second sub-module and an eighth end arranged in the area where the third sub-module is not installed.

As can be seen from the above technical solutions, the present disclosure provides a positional relationship between an input contact S 1 of a direct current input bus and an output contact S 2 of an alternating current output bus so that impedances of all branches between S 1 and S 2 are equal (or substantially equal). Thus, currents flowing through all the inverter modules are equal (or substantially equal), thereby solving the problems existing in the prior art.

For clearer illustration of the technical solutions according to embodiments of the present disclosure or conventional techniques, hereinafter are briefly described the drawings to be applied in embodiments of the present disclosure or conventional techniques. Apparently, the drawings in the following descriptions are only some embodiments of the present disclosure, and other drawings may be obtained by those skilled in the art based on the provided drawings without creative efforts.

FIG. 1 is a schematic diagram of a structure of an inverter system according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a position distribution of S 1 and S 2 according to an embodiment of the present disclosure;

FIG. 3 is a schematic diagram of a position distribution of S 1 and S 2 according to another embodiment of the present disclosure;

FIG. 4 is a schematic diagram of a structure of an inverter system according to another embodiment of the present disclosure;

FIG. 5 is a schematic diagram of a structure of an inverter system according to another embodiment of the present disclosure;

FIG. 6 is a schematic diagram of a heat dissipation design of an inverter system according to an embodiment of the present disclosure;

FIG. 7 is a schematic diagram of a heat dissipation design of an inverter system according to another embodiment of the present disclosure; and

FIG. 8 is a schematic diagram of a heat dissipation design of an inverter system according to another embodiment of the present disclosure.

The technical solution of the present disclosure is hereinafter described in detail with reference to the accompanying drawings. It is evident that the embodiments are only some exemplary embodiments of the present disclosure, and the present disclosure is not limited to such embodiments. Other embodiments that those skilled in the art obtain based on embodiments of the present disclosure also all within the protection scope of the present disclosure.

Referring to FIG. 1 , an embodiment of the present disclose provides an inverter system including multiple inverter modules connected in parallel (assuming that there are n inverter modules connected in parallel, where for convenience of description, the n inverter modules are respectively identified as inverter module 1 , inverter module 2 , . . . , inverter module n).

Input terminals of all the inverter modules are connected to a same direct current input bus Bus 1 , and output terminals of all the inverter modules are connected to a same alternating current output bus Bus 2 .

An input contact S 1 of the direct current input bus Bus 1 and an output contact S 2 of the alternating current output bus Bus 2 are located in a manner that a difference between impedances of each two branches between S 1 and S 2 does not exceed a preset value (the preset value is zero or a value very close to zero).

From the above description, a power level of the inverter system is increased without changing stress of switches by directly connecting multiple inverter modules in parallel according to the embodiment of the present disclosure. At the same time, the embodiment of the present disclosure provides a positional relationship between an input contact S 1 of a direct current input bus Bus 1 and an output contact S 2 of an alternating current output bus Bus 2 , so that impedances of all branches between S 1 and S 2 are equal (or substantially equal). Thus, currents flowing through all the inverter modules are equal (or substantially equal), thereby solving the problems existing in the prior art.

For example, as shown in FIG. 2 or FIG. 3 , n=3. The inverter module 1 , the inverter module 2 , and the inverter module 3 are arranged sequentially in a vertical direction from top to bottom. An impedance value of the direct current input bus Bus 1 connected between an input terminal of the inverter module 3 and an input terminal of the inverter module 2 is defined as R 1 , an impedance value of the direct current input bus Bus 1 connected between the input terminal of the inverter module 2 and an input terminal of the inverter module 1 is defined as R 2 , an impedance value of the alternating current output bus Bus 2 connected between an output terminal of the inverter module 3 and an output terminal of the inverter module 2 is defined as R 3 , and an impedance value of the alternating current output bus Bus 2 connected between the output terminal of the inverter module 2 and an output terminal of the inverter module 1 is defined as R 4 .

In a case that R 1 =R 2 =R 3 =R 4 , and impedance values of the inverter module 1 , the inverter module 2 , and the inverter module 3 are also equal, S 2 and S 1 should satisfy a position requirement that S 2 and S 1 form a diagonal. In an embodiment, as shown in FIG. 2 , S 2 is arranged at an upper left corner of the inverter system, and S 1 is arranged at a lower right corner of the inverter system; or, as shown in FIG. 3 , S 2 is arranged at a lower left corner of the inverter system, and S 1 is arranged at an upper right corner of the inverter system. In FIG. 2 and FIG. 3 , there are three current branches between S 1 and S 2 : S 1 →the inverter module 3 →R 3 →R 4 →S 2 , S 1 →R 1 →the inverter module 2 →R 4 →S 2 , and S 1 →R 1 →R 2 →the inverter module 1 →S 2 . Since the impedances of all branches between S 1 and S 2 are equal, currents flowing through the inverter module 1 , the inverter module 2 , and the inverter module 3 are all equal.

In practice, in a case that there is a difference between R 1 , R 2 , R 3 , R 4 , and/or between the impedance values of the inverter module 1 , the inverter module 2 , and the inverter module 3 , the relative positions of S 2 and S 1 in FIG. 2 and FIG. 3 need to be adjusted appropriately until it is verified through tests that the impedances of all branches between S 1 and S 2 are equal (or substantially equal). In an embodiment, the appropriate adjustment for FIG. 2 includes determining a position of S 2 within a preset range centered on the upper left corner of the inverter system, and determining a position of S 1 within a preset range centered on the lower right corner of the inverter system. The appropriate adjustment for FIG. 3 includes determining a position of S 2 within a preset range centered on the lower left corner of the inverter system, and determining a position of S 1 within a preset range centered on the upper right corner of the inverter system.

The relative positions of S 2 and S 1 in FIG. 1 are provided based on FIG. 2 , where the position of S 2 is within the preset range centered on the upper left corner of the inverter system, and the position of S 1 is within the preset range centered on the lower right corner of the inverter system. In a case that the inverter system is provided based on FIG. 3 , the position of S 2 is within the preset range centered on the lower left corner of the inverter system, and the position of S 1 is within the preset range centered on the upper right corner of the inverter system, in which case a schematic structure diagram of the inverter system as shown in FIG. 4 is obtained.

In an embodiment, the inverter system in the embodiment of the present disclosure may be an inverter system with a three-level circuit topology or an inverter system with a five-level circuit topology, which is not limited. Compared with the inverter system with the five-level circuit topology, the inverter system with the three-level circuit topology has the advantages of high switching frequency, low output harmonic content, and high system efficiency, which has a wide range of applications in new energy generation and other fields.

In the inverter system with the three-level circuit topology, the inverter module may adopt an I-type three-level circuit topology to meet the high current level of the inverter system. Referring to FIG. 1 or FIG. 4 , the I-type three-level circuit topology includes: a first sub-module, a second sub-module, and a third sub-module, and the first sub-module, the second sub-module, and the third sub-module are connected to form an I-type topology.

The I-type topology means that a positive input terminal of the first sub-module is connected to a positive terminal of the direct current input bus Bus 1 , a negative input terminal of the first sub-module is connected to a neutral point N of the direct current input bus Bus 1 , a positive input terminal of the second sub-module is connected to the neutral point of the direct current input bus Bus 1 , a negative input terminal of the second sub-module is connected to a negative terminal of the direct current input bus Bus 1 , an output terminal of the first sub-module is connected to a positive input terminal of the third sub-module, and an output terminal of the second sub-module is connected to a negative input terminal of the third sub-module.

In an embodiment, in any of the inverter systems disclosed above, in a case that the inverter module adopts the I-type three-level circuit topology, the inverter system further includes a first circulation bus L 1 and a second circulation bus L 2 . The first circulation bus L 1 is connected to the output terminal of each first sub-module, and the second circulation bus L 2 is connected to the output terminal of each second sub-module, as shown in FIG. 5 .

In FIG. 5 , output potentials of all the first sub-modules are equalized by the first circulation bus L 1 , and output potentials of all the second sub-modules are equalized by the second circulation bus L 2 . In this way, currents flowing through the third module are balanced, thereby avoiding the current overload or even damage to the corresponding third sub-module caused by the damage of an individual first sub-module or an individual second sub-module.

The inverter system disclosed above needs guaranteed heat dissipation performance for each internal inverter module while ensuring the circuit design and function implementation. The heat dissipation performance of the inverter module is of great significance to the stability, product reliability, and service life of the power device of the entire inverter system. Therefore, in the embodiment of the present disclosure according to any of the inverter systems disclosed above, heat dissipation fins with sparse and dense regions are provided on a housing of the inverter system, and/or multiple heat pipes are provided inside the inverter system (the heat pipe uses the principle of heat conduction and the fast heat transfer property of the phase change medium to quickly transfer the heat of the heating object to the heat source, and its heat conduction capacity exceeds that of any known metal).

In an embodiment, the inverter modules in the inverter system are sequentially arranged in a vertical direction, and cold air enters through a bottom of the inverter system and flows out through a top of the inverter system. In order to ensure uniform heat dissipation and temperature of the inverter modules in a longitudinal direction, the heat dissipation fins are sparse near a cold air side, and are dense near a hot air side, as shown in FIG. 6 . In FIG. 6 , legend D 1 denotes a dense region, and legend D 2 denotes a sparse region; legends Z 1 , Z 2 , and Z 3 denote the first sub-module, the second sub-module, and the third sub-module in one module, respectively; and legend CA denotes cold air, and legend HA denotes hot air. Legends Z 1 , Z 2 , Z 3 , CA, and HA are still used in FIG. 7 and FIG. 8 below, and legends D 1 , D 2 in FIG. 7 and FIG. 8 denote the same elements as in FIG. 6 . Among them, sizes of the sparse region and dense region are determined by practical situations.

In any of the inverter systems disclosed above, the inverter modules in the inverter system are sequentially arranged in a vertical direction, and cold air enters through the bottom of the inverter system and flows out through the top of the inverter system. Each inverter module is provided with multiple heat pipes, and the heat that cannot be taken away by the cold air is transferred to a module area where no power module is installed or a power consumption is small (that is, a region without any heat generation or with less heat generation). Thereby, the temperature of the inverter module is substantially uniform in a horizontal direction. Among them, the number of heat pipes and the specific layout are determined according to actual needs.

For example, as shown in FIG. 7 , in a case that the inverter module has an I-type three-level circuit topology, the inverter system may have the following internal configurations. The first sub-module and the second sub-module are arranged in a vertical direction (the first sub-module may be disposed right above the second sub-module, as shown in FIG. 7 ; or the second sub-module may be disposed right above the first sub-module). In a horizontal direction of the inverter module, the first sub-module and the second sub-module are arranged at one side in the inverter module, and the third sub-module is arranged on the other side in the inverter module (for example, the first sub-module and the second sub-module are arranged at a right side in the inverter module, and the third sub-module is arranged at a left side of the inverter module). The internal configuration of each inverter module is the same.

With continued reference to FIG. 7 , in the embodiment, four heat pipes are provided for each inverter module (legends G 1 , G 2 , G 3 , and G 4 in FIG. 7 donate heat pipe 1 , heat pipe 2 , heat pipe 3 , and heat pipe 4 , respectively, and the legends G 1 , G 2 , G 3 , G 4 in FIG. 8 below denote the same elements as in FIG. 7 ), as the three sub-modules in the inverter module generate the same amount of heat and heat accumulation may happen due to the fact that the first sub-module and the second sub-module are arranged in a longitudinal heat dissipation direction. One end of heat pipe 1 is arranged on a surface of the first sub-module, and another end of the heat pipe 1 is arranged in an area where the third sub-module is not installed, which is also the case for heat pipe 2 ; one end of heat pipe 4 is arranged on a surface of the second sub-module, and anther end of the heat pipe 4 is arranged in the area where the third sub-module is not installed; and one end of heat pipe 3 is arranged on the surface of the second sub-module, and another end of heat pipe 3 is arranged on the surface of the third sub-module. The heat pipe 1 and the heat pipe 2 transfer a part of the heat of the first sub-module to an area without a heat source on the left side; the heat pipe 4 transfers a part of the heat of the second sub-module to the area without a heat source on the left side; and the heat pipe 3 transfers a part of the heat of the second sub-module to an area where the third sub-module is located. In this way, uniform temperature in the horizontal direction is achieved and the heat accumulation is avoided by using the heat pipe 1 , the heat pipe 2 , the heat pipe 3 , and the heat pipe 4 .

In an embodiment of the present disclosure, the heat dissipation methods of FIG. 6 and FIG. 7 are combined in application, based on which the embodiment shown in FIG. 8 is obtained. The housing of the inverter system is provided with heat dissipation fins that are non-uniformly distributed, realizing uniform heat dissipation in the longitudinal direction, and multiple heat pipes are provided inside the inverter system, uniform temperature in the horizontal direction is achieved, thereby avoiding heat accumulation in both directions.

The embodiments of the present disclosure are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. Reference may be made to each other of the embodiments for the same and similar parts between the embodiments.

It should also be noted that the relationship terms such as “first”, “second” and the like are only used herein to distinguish one entity or operation from one another, rather than to necessitate or imply that an actual relationship or order exists between the entities or operations. Furthermore, the terms such as “include”, “comprise” or any other variants thereof means to be non-exclusive, so that a process, a method, an article or a device including a series of elements include not only the disclosed elements but also other elements that are not clearly enumerated, or further include inherent elements of the process, the method, the article or the device. Unless expressively limited, the statement “including a . . . ” preceding an element does not exclude the existence of other similar elements in the process, the method, the article or the device other than the enumerated elements.

According to the description of the disclosed embodiments, those skilled in the art can implement or use the present disclosure. Various modifications made to these embodiments may be obvious to those skilled in the art, and the general principle defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments described herein but conforms to a widest scope in accordance with principles and novel features disclosed in the present disclosure.