Control system for permanent magnet synchronous motor and module

The present application claims priority from Japanese application serial no. 2004-266164, filed on Sep. 14, 2004, the content of which is hereby incorporated by reference into this application.

The present invention relates to a position sensor-less vector control system of a permanent magnet synchronous motor.

As a resistance identification art of the position sensor-less vector control system, in Japanese Patent Laid-open No. 2003-164188, before starting operation of a motor, a method for applying an inverter voltage so as to restrict the motor and identifying the resistance from the voltage and restriction current flowing and during operation, a method for installing a means for identifying the counter electromotive voltage factor of the motor, inferring the motor temperature from the value identified during operation and a preset counter electromotive voltage factor at normal temperature, and identifying the resistance using the inferred temperature are described.

When high torque is required during operation under speed control or torque control, it is necessary to supply a large current corresponding to the torque. When high torque is required for a long period of time, due to generation of heat by the motor current, the resistance R of the motor increases with time.

Further, under the position sensor-less control, for example, an error value (hereinafter referred to as a phase error value Δθ) between “rotation phase instruction value θc* based on control shaft” and “rotation phase instruction value θ based on motor axis” is inferred by calculation, and a frequency instruction value ω 1 * is adjusted so as to reduce an inference phase error value Δθc to zero, and ω 1 * is integrated, thus the rotation phase instruction value θc* is prepared.

In calculations of obtaining voltage instruction values Vd** and Vq** of the inverter and the inference phase error value Δθc like this, it is necessary to set the resistance R of the motor.

When a setting error (R−R*) is caused between the set value R* and the resistance R of the motor, if an impact load disturbance is caused in the low-speed rotation area, the actual phase error value Δθ and the inference phase error value Δθc are shifted from each other, thus the optimal phase cannot be controlled, and the apparatus may fall into an un-operable state.

However, in the method described in Japanese Patent Laid-open No. 2003-164188, the identification calculation of the counter electromotive voltage factor must be executed in an area of small load torque and a problem arises that the calculation accuracy is impaired in an area of high torque.

Therefore, during the high-torque operation, the inference accuracy of the motor temperature is impaired, thus it is impossible to realize “highly accurate resistance identification”.

An object of the present invention is to provide a vector control of a permanent magnet synchronous motor realizing highly accurate position sensor-less vector control even in a high-torque area.

The present invention, using the current control equivalent output value, current detection value, frequency instruction value, inference phase error value, and motor constant, identifies the motor resistance equivalent or resistance setting error equivalent and using the identified value, corrects the set value R* equivalent of the voltage instruction calculation unit and phase error calculation unit.

FIG. 1 is an example of the block diagram of the vector control system for the permanent magnet synchronous motor indicating an embodiment of the present invention,

FIG. 2 is an example of the inverter load characteristic diagram (R=R*) when the resistance identification calculation unit 11 is not used,

FIG. 3 is an example of the inverter load characteristic diagram (R=1.3R*) when the resistance identification calculation unit 11 is not used,

FIG. 4 is an example of the resistance identification calculation unit 11 of the control system shown in FIG. 1 ,

FIG. 5 is an example of the inverter load characteristic diagram (R=1.3R*) when the resistance identification calculation unit 11 is used,

FIG. 6 is a block diagram of the vector control system for the permanent magnet synchronous motor indicating another embodiment of the present invention,

FIG. 7 is an example of the resistance identification calculation unit 11 a of the control system shown in FIG. 6 ,

FIG. 8 is a block diagram of the vector control system for the permanent magnet synchronous motor indicating still another embodiment of the present invention,

FIG. 9 is an example of the resistance identification calculation unit 11 b of the control system shown in FIG. 8 ,

FIG. 10 is an example of the vector control system for the permanent magnet synchronous motor indicating a further embodiment of the present invention, and

FIG. 11 is a diagram of an embodiment that the present invention is applied to a module.

Hereinafter, the embodiments of the present invention will be explained in detail with reference to the accompanying drawings.

First Embodiment

FIG. 1 shows a constitution example of the vector control system for the permanent magnet synchronous motor of an embodiment of the present invention.

Numeral 1 indicates a permanent magnet synchronous motor, 2 an inverter for outputting voltages proportional to 3-phase AC voltage instruction values Vu*, Vv*, and Vw*, 21 a DC power source, 3 a current detector for detecting 3-phase AC currents Iu, Iv, and Iw, 4 a phase error calculation unit for calculating the inference value (Δθc) of the phase error value Δθ (=θc*−θ) which is a deviation between the rotation phase instruction value θc* and the rotation phase value θ of the motor 1 , 5 a frequency calculation unit for calculating the frequency instruction value ω 1 * from the inference phase error value Δθc, 6 a phase calculation unit for calculating the rotation phase instruction value θc* of the motor 1 from the frequency instruction value ω 1 *, 7 a coordinate conversion unit for outputting the d-axial and q-axial current detection values Idc and Iqc from the detection values Iuc, Ivc, and Iwc of the 3-phase AC currents Iu, Iv, and Iw and the rotation phase instruction value θc*, 8 a d-axial current instruction calculation unit for outputting the second d-axial current instruction value Id** according to the deviation between the first d-axial current instruction value Id* given from the host computer and the d-axial current detection value Iqc, 9 a q-axial current instruction calculation unit for outputting the second q-axial current instruction value Iq** according to the deviation between the first q-axial current instruction value Iq* given from the host computer and the q-axial current detection value Iqc, 10 a vector control calculation unit for outputting the voltage instruction values Vd** and Vq** using the d-axial and q-axial second current instruction values Id** and Jq**, the frequency instruction value ω 1 *, and the electrical constant of the motor 1 , 11 a resistance identification calculation unit for identifying the voltage ΔVr including the resistance setting error on the basis of the second q-axial current instruction value Iq**, the q-axial current detection value Iqc, the frequency instruction value ω 1 *, the inference phase error value Δθc, and the electrical constant of the motor 1 , performing proportional or integral calculations using the identified value, calculating the resistance setting error voltage ΔVr*, and outputting it to the calculation unit of the q-axial voltage instruction value Vq*** and the inference phase error value Δθc, and 12 a coordinate conversion unit for outputting the 3-phase AC voltage instruction values Vu*, Vv*, and Vw* from the voltage instruction values Vd** and Vq*** and the rotation phase instruction value θc*.

Firstly, the basic operations of voltage control and phase control of the position sensor-less vector control system when the resistance identification calculation unit 11 which is a characteristic of the present invention is not installed (ΔVr* is zero) will be explained.

The basic operation of voltage control, in the d-axial and q-axial current instruction calculation units 8 and 9 , using the first current instruction values Id* and Iq* given from the host computer and the current detection values Idc and Iqc, calculates the intermediate current instruction values Id** and Iq** used for vector control calculations.

The vector control calculation unit 10 , using the second current instruction values Id** and Iq**, the frequency instruction value ω 1 *, and the set value of the motor constant, calculates the voltage instruction values Vd** and Vq** shown in Formula (1), and controls the voltage instruction values Vu*, Vv*, and Vw* of the inverter.

In this case, R indicates a resistance, Ld a d-axial inductance, Lq a q-axial inductance, Ke an induced voltage factor, and * a set value.

On the other hand, the basic operation of phase control, in the phase error calculation unit 4 , using the voltage instruction values Vd** and Vq**, the current detection values Idc and Iqc, the frequency instruction value ω 1 *, and the set value of the motor constant, infers and calculates the phase error value Δθ(=θc*−θ) which is a deviation between the rotation phase instruction value θc* and the rotation phase value θ. The calculation of the inference phase error value Δθc is performed by Formula (2).

Further, the frequency calculation unit 5 , so as to reduce the inference phase error value Δθc to zero, controls the frequency instruction value ω 1 * by calculation of Formula (3).

wherein Kp indicates a proportional gain and Ki indicates an integration gain.

The phase calculation unit 6 controls the rotation phase instruction value θc* by calculation of Formula (4) using the frequency instruction value ω 1 *.

The aforementioned is the conventional basic operations of voltage control and phase control.

Next, the operation effects when the resistance identification calculation unit 11 which is a characteristic of the present invention is used will be explained.

In the control system shown in FIG. 1 , when the resistance setting error voltage ΔVr* is not added, the simulation characteristics when an impact load is applied are shown in FIGS. 2 and 3 .

FIG. 2 shows the characteristics when the resistance R of the motor and the set value R* set in the phase difference calculation unit 4 and the vector control calculation unit 10 coincide with each other (R=R*).

In a control configuration that a speed control system is added to the host system, when the motor is during the constant operation at the 25[%] speed of the low rotation speed area of the motor, at a point of A after 1 [s], when an impact load of L is applied, the rotation speed of the motor is suddenly reduced closely to the 10[%] speed.

At this time, the situation is found that the actual phase error value Δθ(θc*−θ) and the inference phase error value Δθc coincide with each other and the rotation frequency ω 1 and the frequency instruction value ω 1 * are recovered stably.

However, when the resistance R of the motor and the set value R* do not coincide with each other in FIG. 3 (R=1.3×R*), the situation is found that when the impact load is applied, the rotation frequency ω 1 is reduced to zero and the frequency instruction value ω 1 * is stably fixed to a larger value than zero (here, referred as to an unoperable state). At this time, it is found that the actual phase error value Δθ(θc*−θ) and the inference phase error value Δθc do not coincide with each other.

After all, when there is a resistance setting error (R−R*) in the low rotation speed area in the phase error calculation unit 4 and the vector control calculation unit 10 , at the time of application of the impact load, the unoperable state may be caused.

Here, the resistance identification principle which is a characteristic of the present invention will be explained.

In the vector control calculation unit 10 , the voltage instruction values Vd** and Vq** indicated in Formula (5) which is the same as Formula (1) is calculated.

When the phase error value Δθ which is a deviation between θc* which is a reference of the control shaft and θ which is a reference of the motor is caused, the coordinate conversion matrix from the control shaft (dc-qc) to the motor shaft (d-q) is expressed by Formula (6).

When the aforementioned phase error value Δθ is caused, the application voltages Vd and Vq of the motor which are calculated by the control side are changed from Formulas (5) and (6) to Formula (7).

On the other hand, the application voltages Vd and Vq of the motor are expressed as shown below using the inference phase error value Δθc, the current detection values Idc and Iqc, and the motor constant.

Here, from the relationship of the right side of Formula (7)= the right side of Formula (8), Lq*=Lq, Ld*=Ld, and Ke*=Ke and by setting Id* to zero and Iq* to a predetermined value, when the current instruction value is calculated, the output value Iq** of the q-axial current instruction calculation unit 9 can be expressed by Formula (9).

Further, in Formula (9), in the low rotation speed area, Formula (10) is held.

R* 2 >>Ld·Lq·ω 1 2   (10)

Then, Formula (9) can approximate to Formula (11).

Here, when both sides of Formula (11) are multiplied by the resistance set value R* and the voltage R*×Iqc is subtracted, the following formula is obtained.

When the voltage ΔVr(=(R−R*)×Iqc) including the resistance setting error is obtained from Formula (12), the following formula is obtained.

Therefore, using the second q-axial current instruction value Iq**, the current detection value Iqc, the frequency instruction value ω 1 *, the inference phase error value Δθc, and the motor constant, when Formula (14) is calculated, the voltage ΔVr can be identified.

Next, the resistance setting error correction method using the identified voltage ΔVr^ will be explained. In the operation of voltage control, assuming a signal obtained by multiplying the voltage ΔVr^ calculated by Formula (14) by the proportional gain Kv as ΔVr*, the following formula is obtained.

Δ Vr*=Kv·ΔVr^   (15)

Formula (15) is added to the q-axial voltage instruction value Vq** and the new voltage instruction value is defined as Vq**.

Here, if a case that the phase error value Δθ is caused when the voltage ΔVr* is added is considered, the following formula is obtained.

When the application voltages Vd and Vq of the motor are expressed using the motor constant (Formula 8 is described again), the following formula is obtained.

From the relationship of the right side of Formula (17)=the right side of Formula (18), in the low rotation speed area, the output value Iq** of the q-axial current instruction calculation unit 9 can approximate to Formula (19).

When the second q-axial current instruction value Iq** obtained by Formula (19) is substituted for Formulas (14) and (15), Formula (20) is obtained.

Furthermore, when the proportional gain Kv is set to a value larger than 1 in Formula (20), the following formula is obtained.

ΔVr*≈(R−R*)·Iqc   (21)

From Formula (21), the voltage ΔVr equivalent including the resistance setting error can be supplied from the output value ΔVr* of the resistance identification calculation unit 11 .

Here, by referring to FIG. 4 , the resistance identification calculation unit 11 which is a characteristic of the present invention will be explained.

Basically, the resistance identification calculation unit 11 calculates Formula (14) and to the deviation between the second q-axial current instruction value Iq** and the q-axial current detection value Iqc, adds a first signal obtained by multiplying a set value 111 of the motor resistance, a second signal obtained by multiplying three values including a value obtained by subtracting the cosine (cos) signal of the inference phase error value Δθc from the constant 1, the frequency instruction value ω 1 *, and a set value 112 of the induced voltage factor, and a third signal obtained by multiplying three values including the sine (sin) signal of the inference phase error value, the square of the frequency instruction value, and a constant calculation value 113 of the motor.

The result obtained by multiplying the added value by a proportional gain 114 is input to a primary delay filter 115 equivalent to the current control time lag and the output value thereof is the voltage ΔVr* for correcting the resistance setting error.

Also in the operation of phase control, the resistance setting error correction is performed using the voltage ΔVr*. The phase error calculation unit 4 shown in FIG. 1 , using the voltage instruction values Vd** and Vq***, the current detection values Idc and Iqc, the frequency instruction value ω 1 *, the set value of the motor constant, and the voltage ΔVr*, infers and calculates the phase error value Δθ.

The inference phase error value Δθc is calculated by Formula (22).

From Formulas (21) and (22), the inference phase error value Δθc is expressed by the following formula.

As a result, even if the set value R* set in the phase error calculation unit 4 and the vector control calculation unit 10 does not coincide with the resistance R of the motor, using the output value Iq** of the q-axial current instruction calculation unit 9 , the resistance setting error can be corrected.

FIG. 5 shows a simulation waveform to which this embodiment is applied (R=1.3×R*).

It is found that even if the resistance R and the set value R* do not coincide with each other, by correcting the voltage ΔVr*, the motor does not fall into the unoperable state and is controlled stably.

“Resistance correction rate” shown in the fourth diagram indicates a ratio of “voltage ΔVr* for correcting the resistance setting error” to “product of R* and Iqc”.

It is found that the resistance setting error 30[%] equivalent is corrected faithfully.

In this embodiment, a signal obtained by multiplying the identified voltage ΔVr^ by the proportional gain Kv is defined as ΔVr*. However, even if a signal obtained by integrating the voltage ΔVr*^ is defined as ΔVr*, it is clear that the same results are obtained.

Further, in this embodiment, the voltage ΔVr* is used as a voltage for correcting the resistance setting error. However, even if ΔVr* is divided by Iqc or Iq*, thus the resistance setting error (R−R*) is obtained directly and is directly added to the set values of the phase error calculation unit 4 and the vector control calculation unit 10 , it is clear that the same results are obtained.

Second Embodiment

FIG. 6 shows another embodiment of the present invention.

This embodiment is the vector control system for the permanent magnet synchronous motor for correcting the output values Vd* and Vq* of the vector control calculation unit by the deviation between the current instruction value and the current detection value given from the host computer.

In FIG. 6 , numerals 1 to 7 , 12 , and 21 indicate the same parts as those shown in FIG. 1 .

Numeral 8 a indicates a d-axial current control calculation unit for calculating ΔVd so as to make the d-axial current instruction value Id* and the d-axial current detection value Idc coincide with each other, 9 a a q-axial current control calculation unit for calculating ΔVq so as to make the q-axial current instruction value Iq* and the q-axial current detection value Iqc coincide with each other, 10 a a vector control calculation unit for outputting the reference values Vd* and Vq* of the voltage instruction using the d-axial and q-axial current instruction values Id* and Iq*, the frequency instruction value ω 1 *, and the set value of the motor constant, and 11 a a resistance identification calculation unit for identifying the voltage ΔVr* equivalent including the resistance setting error using the q-axial current control output value ΔVq, the q-axial current detection value Iqc, the frequency instruction value ω 1 *, the inference phase error value Δθc, and the set value of the motor constant.

The difference from FIG. 1 indicated in the previous embodiment is that in the d-axial and q-axial current control calculation units 8 a and 9 a, so as to make the current detection values Idc and Iqc coincide with the current instruction values Id* and Iq* given from the host computer, the voltage correction values ΔVd and ΔVq are calculated.

Further, the difference is that in the vector control calculation unit 10 a, using the current instruction values Id* and Iq*, the frequency instruction value ω 1 *, and the set value of the motor constant, the reference values Vd* and Vq* of the voltage instruction indicated in Formula (24) are calculated and,

As shown in Formula (25), the voltage instruction values Vd** and Vq** of the inverter are calculated.

Next, the operation effects produced by the present invention will be explained.

Firstly, when ΔVr*=0 is held and the phase error value Δθ is caused, the voltage instruction values Vd** and Vq** are expressed by Formula (26).

Further, the application voltages Vd and Vq of the motor are expressed as indicated below using the phase error value Δθ and the motor constant (the same as Formula 8).

Here, from the relationship of the right side of Formula (26)= the right side of Formula (27), Lq*=Lq, Ld*=Ld, and Ke*=Ke and by setting Id* to zero and Iq* to a predetermined value, when the current is controlled, the output value ΔVq of the q-axial current control calculation unit 9 a can be expressed by Formula (28).

Δ Vq =( R−R *)· Iqc−ω 1 ·Ke ·(1−cos Δθ)−ω 1 ·( Ld−Lq )· Iqc ·sin Δθcos Δθ  (28)

Here, when the item of the voltage ΔVr(=(R−R*)×Iqc) including the resistance setting error information is arranged properly, the following formula is obtained.

( R−R *)· Iqc=ΔVq+ω 1 ·Ke ·(1 −cos Δθ)+ω 1 ( Ld−Lq )· Iqc ·sin Δθ·cos Δθ  (29)

From Formula (29), using the output value ΔVq of the q-axial current control, the frequency instruction value ω 1 *, the inference phase error value Δθc, and the set value of the motor constant, when Formula (30) is calculated, the voltage ΔVr can be identified.

Δ Vr^=ΔVq+ω 1 *·Ke *·(1 −cos Δθ c )+ω 1 *·( Ld*−Lq *)· Iqc ·sin Δθ c ·cos Δθ c   (30)

Next, the resistance setting error correction method using the voltage ΔVr^ will be explained.

Assuming a signal obtained by multiplying the voltage ΔVr^ calculated in Formula (30) by the proportional gain Kv as ΔVr*, the following formula is obtained.

Δ Vr*=Kv·ΔVr^   (31)

Here, Formula (31) is added to the q-axial voltage instruction value Vq** and the following formula is obtained.

When Formula 32 is used for calculation of the inference phase error value Δθc, in the same way as with Embodiment 1, the voltage ΔVr equivalent including the resistance setting error can be supplied from the output value ΔVr* of the resistance identification calculation unit 11 a.

This can be applied to the vector control system for the permanent magnet synchronous motor for correcting the output of the vector control calculation unit by the deviation between the current instruction value and the current detection value.

Here, by referring to FIG. 7 , the resistance identification calculation unit 11 a which is a characteristic of the present invention will be explained.

Basically, the resistance identification calculation unit 11 a calculates Formula (30) and adds a first signal which is the output value ΔVq of q-axial current control, a second signal obtained by multiplying three values including a value obtained by subtracting the cosine (cos) signal cos Δθc of the inference phase error value Δθc from the constant 1, the frequency instruction value ω 1 *, and a set value 11 a 1 of the induced voltage factor, and a third signal obtained by multiplying five values including the sine (sin) signal sin Δθc and cosine (cos) signal cos Δθc of the inference phase error value, the frequency instruction value ω 1 *, the q-axial current detection value Iqc, and a difference 11 a 2 between the d-axial inductance of the motor and the q-axial inductance.

The result obtained by multiplying the added value by a proportional gain 11 a 4 is input to a primary delay filter 11 a 5 equivalent to the current control time lag and the output value thereof is the voltage ΔVr* for correcting the resistance setting error.

In this embodiment, a signal obtained by multiplying the identified voltage ΔVr^ by the proportional gain Kv is defined as ΔVr*. However, even if a signal obtained by integrating the voltage ΔVr^ is defined as ΔVr*, it is clear that the same results are obtained.

Further, in this embodiment, the voltage ΔVr* is used as a voltage for correcting the resistance setting error. However, even if ΔVr* is divided by Iqc or Iq*, thus the resistance setting error (R−R*) is directly obtained and is directly added to the set values of the phase error calculation unit 4 and the vector control calculation unit 10 a, it is clear that the same results are obtained.

Third Embodiment

FIG. 8 shows still another embodiment of the present invention.

This embodiment is the vector control system for the permanent magnet synchronous motor for directly controlling the d-axial and q-axial voltage instruction values Vd** and Vq** by the deviation between the current instruction value and the current detection value given from the host computer.

In FIG. 8 , numerals 1 to 7 , 12 , and 21 indicate the same parts as those shown in FIG. 1 . Numeral 8 b indicates a d-axial current control calculation unit for controlling the d-axial voltage instruction value Vd** so as to make the d-axial current instruction value Id* and the d-axial current detection value Idc coincide with each other, 9 b a q-axial current control calculation unit for controlling the q-axial voltage instruction value Vq** so as to make the q-axial current instruction value Iq* and the q-axial current detection value Iqc coincide with each other, and 11 b a resistance identification calculation unit for outputting ΔVr* equivalent to the voltage ΔVr including the resistance setting error using the q-axial voltage control output value Vq**, the q-axial current detection value Iqc, the frequency instruction value ω 1 *, the inference phase error value Δθc, and the set value of the motor constant.

The difference from FIG. 1 indicated in the previous embodiment is that in the d-axial and q-axial current control calculation units 8 b and 9 b, so as to make the current detection values Idc and Iqc coincide with the first current instruction values Id* and Iq* given from the host computer, the voltage instruction values Vd** and Vq** are calculated.

Next, the operation effects produced by the present invention will be explained.

Firstly, the application voltages Vd and Vq of the motor are expressed as indicated below using the phase error value Δθ and the motor constant (the same as Formula 8).

Here, from the relationship that the voltage instruction values Vd** and Vq** coincide with the right side of Formula (33), Lq*=Lq, Ld*=Ld, and Ke*=Ke and by setting Id* to zero and Iq* to a predetermined value, when the current is controlled, the output value Vq** of the q-axial current control calculation unit 9 b can be expressed by Formula (34).

Vq**=R·Iqc+ω 1 ·Ke ·cos Δθ−ω 1 ·( Ld−Lq )· Iqc ·sin Δθ·cosΔθ  (34)

Here, when the item of the voltage ΔVr(=R×Iqc) including the information of the motor resistance is arranged properly, the following formula is obtained.

R·Iqc=Vq**−ω 1 ·Ke ·cos Δθ+ω 1 ·( Ld−Lq )· Iqc ·sin Δθ·cos Δθ  (35)

From Formula (35), using the output value Vq** of q-axial current control, the frequency instruction value ω 1 *, the inference phase error value Δθc, and the set value of the motor constant, when Formula (36) is calculated, the voltage ΔVr can be identified.

Δ Vr^=Vq**−ω 1 *·Ke *·cos Δθ c+ω 1 *·( Ld*−Lq *)· Iqc ·sin Δθ c ·cos Δθ c   (36)

Next, the resistance correction method using the voltage ΔVr^ will be explained.

Assuming a signal obtained by adding the signal obtained by multiplying the voltage ΔVr^ calculated by Formula (36) by the proportional gain Kv to the voltage which is the product of the resistance set value R* set in the phase error calculation unit 4 and the q-axial current detection value Iqc as ΔVr*, the following formula is obtained.

Δ Vr*=Kv·ΔVr^+R*Iqc   (37)

A new q-axial voltage instruction value Vq*** is as indicated below.

Vq***=Vq**+ΔVr*   (38)

Further, when Vq*** is used for calculation of the inference phase error value Δθc, the voltage ΔVr including the resistance can be supplied from the output value ΔVr* of the resistance identification calculation unit 11 b.

This can be applied to the vector control system for the permanent magnet synchronous motor for outputting the vector control calculation by the deviation between the current instruction value and the current detection value.

Here, by referring to FIG. 9 , the resistance identification calculation unit 1 b which is a characteristic of the present invention will be explained. The resistance identification calculation unit 11 b adds a first signal which is the output value Vq** of q-axial current control, a second signal obtained by multiplying three values including the cosine (cos) signal of the inference phase error value Δθc, the frequency instruction value ω 1 *, and a set value 11 b 1 of the induced voltage factor, and a third signal obtained by multiplying five values including the sine (sin) signal sin Δθc and cosine (cos) signal cos Δθc of the inference phase error value Δθc, the frequency instruction value ω 1 *, the q-axial current detection value Iqc, and a difference 11 b 2 between the d-axial inductance of the motor and the q-axial inductance. The result obtained by multiplying the added value by a proportional gain 11 b 4 is input to a primary delay filter 11 b 5 equivalent to the current control time lag, and moreover from the output value, the product of the q-axial current detection value Iqc and a resistance set value 11 b 3 is subtracted, and the voltage ΔVr* for correcting the resistance setting error is obtained.

In this embodiment, a signal obtained by multiplying the identified voltage ΔVr^ by the proportional gain Kv is defined as ΔVr*. However, even if a signal obtained by integrating the voltage ΔVr^ is defined as ΔVr*, it is clear that the same results are obtained.

Further, in this embodiment, the voltage ΔVr* is used as a voltage including the resistance setting error (R−R*). However, even if the voltage ΔVr* is divided by Iqc or Iq*, thus the resistance setting error (R−R*) is directly obtained and is directly added to the set value R* of the phase error calculation unit 4 , the same results are obtained.

Fourth Embodiment

In the first to third embodiments aforementioned, the method for detecting the 3-phase AC currents Iu to Iw detected by the expensive current detector 3 is used. However, the present invention can be applied to a control unit for performing inexpensive current detection.

This embodiment is shown in FIG. 10 .

In FIG. 10 , the components 1 , 2 , 4 to 12 , and 21 are the same as those shown in FIG. 1 .

Numeral 13 indicates a current reproduction unit for reproducing the 3-phase AC currents Iu, Iv, and lw flowing through the motor 1 from a DC current IDC flowing through the input bus of the inverter 2 .

Using the inference currents Iu^, Iv^, and Iw^, the coordinate conversion unit 7 calculates the d-axial and q-axial current detection values Idc and Iqc.

Even such a current sensor-less control system, since Id* and Idc, and Iq* and Iqc respectively coincide with each other, operates in the same way as with the embodiment shown in FIG. 1 and it is clear that the same results are obtained.

Further, in this embodiment, the embodiment shown in FIG. 1 is used. However, even if the embodiments shown in FIGS. 6 and 8 are used, the same results are obtained.

Fifth Embodiment

An example that the present invention is applied to a module will be explained by referring to FIG. 11 . This embodiment indicates the configuration of the first embodiment. Here, the phase error calculation unit 4 , the frequency calculation unit 5 , the phase calculation unit 6 , the coordinate conversion unit 7 , the d-axial current instruction calculation unit 8 , the q-axial current instruction calculation unit 9 , the vector control calculation unit 10 , the resistance identification calculation unit 11 , and the coordinated conversion unit 12 constitute a one-chip microcomputer. Further, the one-chip microcomputer and power converter (the inverter 2 ) are stored in one module formed on the same substrate. The module mentioned above means “standardized constituent unit” and it is composed of separable hardware and software parts. Further, from a viewpoint of manufacture, the parts are preferably formed on the same substrate, though they are not limited to the same substrate. Therefore, the parts may be formed on a plurality of circuit substrates built in the same frame. In other embodiments, the same configuration may be used.

As mentioned above, according to the present invention, in the low rotation speed area under position sensor-less control, the low burst control characteristic can be realized for changing of the resistance constant of the motor. Further, in a system performing inexpensive current detection, a vector control system for a permanent magnet synchronous motor which can be applied in common can be provided.

Further, during actual operation, the resistance equivalent of the motor is identified, and the resistance constant set in the control system is corrected automatically, thus highly precise vector control can be realized.

A vector control system for a permanent magnet synchronous motor realizing highly precise position sensor-less vector control in a high-torque area can be provided.