JP7363611B2 - AC motor control device - Google Patents

Description

The present invention relates to a control device for an AC motor.

As an AC motor control device, the d-axis voltage command value and q-axis voltage command value generated by PI control (Proportional Integral) are used as the d-axis current command value and the q-axis current command value output from the low-pass filter. Some corrections are made using non-interference control. According to this control device, the high frequency components included in the d-axis current command value and the q-axis current command value can be suppressed by the low-pass filter, and the response speed [rad/s] in the low-pass filter can be adjusted to the response speed in PI control. By bringing them closer together, current responsiveness can be improved. A related technique is Patent Document 1.

By the way, in order to bring the response speed of the low-pass filter closer to the response speed of PI control, it is necessary to adjust the cutoff frequency of the low-pass filter.

Therefore, in the above control device, when adjusting the cutoff frequency using experiments or simulations, there is a concern that the adjustment requires a relatively large number of man-hours.

Japanese Patent Application Publication No. 2004-072856

An object of one aspect of the present invention is to convert the d-axis voltage command value and q-axis voltage command value generated by PI control to non-standard values using the d-axis current command value and q-axis current command value output from a low-pass filter. An object of the present invention is to reduce the number of man-hours required for adjusting the cutoff frequency of a low-pass filter in a control device for an AC motor that corrects by interference control.

A control device for an AC motor, which is one embodiment of the present invention, includes an inverter circuit that drives the AC motor based on the comparison result between a carrier wave and a voltage command value, and a circuit that converts the current flowing through the AC motor into a d-axis current and a q-axis current. Then, by PI control, the d-axis voltage command value is calculated so that the difference between the d-axis current and the d-axis current command value becomes small, and the q-axis voltage command value is calculated so that the difference between the q-axis current and the q-axis current command value becomes small. The control circuit includes a control circuit that calculates a voltage command value and converts a corrected d-axis voltage command value and a corrected q-axis voltage command value into voltage command values.

The control circuit includes a first low-pass filter to which a d-axis current command value is input, a second low-pass filter to which a q-axis current command value is input, and a d-axis current command value output from the first low-pass filter. and a q-axis current output from the second low-pass filter; a second adjustment unit that adjusts the cutoff frequency of the second low-pass filter such that a second difference between the current command value and the q-axis current is equal to or less than a second threshold; Outputting a d-axis voltage command value corresponding to a variation in the d-axis current command value output from the first low-pass filter due to the interference as a first correction value, and causing the d-axis current to interfere with the q-axis current. a non-interference control unit that outputs, as a second correction value, a q-axis voltage command value corresponding to a variation in the q-axis current command value output from a second low-pass filter; A first addition unit outputs the added value with the second correction value as the corrected d-axis voltage command value, and outputs the added value of the uncorrected q-axis voltage command value and the first correction value with the corrected d-axis voltage command value. and a second addition section that outputs the q-axis voltage command value.

As a result, the response speeds of the first and second low-pass filters can be brought closer to the response speeds of the PI control in the first and second adjustment sections, so that the cutoff frequencies of the first and second low-pass filters can be adjusted. The number of man-hours required for adjustment can be reduced.

Alternatively, the first threshold value may be the minimum value of the first difference, and the second threshold value may be the minimum value of the second difference.

This further improves current responsiveness compared to the case where the first threshold value is set to a value larger than the first minimum value of the difference, and the second threshold value is set to a value larger than the second minimum value of the difference. I can do it.

Further, the first and second adjustment sections may be configured to repeatedly adjust the cutoff frequencies of the first and second low-pass filters while the AC motor is being driven.

As a result, even if the response speed in PI control changes due to deterioration of the AC motor while the AC motor is being driven, the response speeds of the first and second low-pass filters can be changed to follow the changing response speed. Therefore, current responsiveness can be maintained.

According to the present invention, the d-axis voltage command value and the q-axis voltage command value generated by PI control are corrected by non-interference control using the d-axis current command value and the q-axis current command value output from the low-pass filter. In the control device for an AC motor, the number of man-hours required for adjusting the cutoff frequency of the low-pass filter can be reduced.

FIG. 1 is a diagram showing a control device for an AC motor according to an embodiment. FIG. 3 is a diagram showing a correction value output section.

Embodiments will be described in detail below based on the drawings.

FIG. 1 is a diagram showing a control device for an AC motor according to an embodiment.

The control device 1 shown in FIG. 1 is, for example, a control device for driving an AC motor M (such as a permanent magnet synchronous motor) mounted on a vehicle (such as an electric forklift or a plug-in hybrid vehicle), and includes an inverter circuit 2. and a control circuit 3. It is assumed that the AC motor M includes an electrical angle detection section Sp (such as a resolver) that detects the phase θ (electrical angle) of the rotor and outputs the detected phase θ to the control circuit 3.

The inverter circuit 2 converts DC power supplied from a power supply P into AC power to drive an AC motor M, and includes a capacitor C and switching elements SW1 to SW6 (IGBT (Insulated Gate Bipolar Transistor), etc.). and current sensors Si1 and Si2. That is, one end of the capacitor C is connected to the positive terminal of the power supply P and the collector terminals of the switching elements SW1, SW3, and SW5, and the other end of the capacitor C is connected to the negative terminal of the power supply P and each of the switching elements SW2, SW4, and SW6. Connected to the emitter terminal. A connection point between the emitter terminal of switching element SW1 and the collector terminal of switching element SW2 is connected to the U-phase input terminal of AC motor M via current sensor Si1. A connection point between the emitter terminal of switching element SW3 and the collector terminal of switching element SW4 is connected to the V-phase input terminal of AC motor M via current sensor Si2. A connection point between the emitter terminal of switching element SW5 and the collector terminal of switching element SW6 is connected to the W-phase input terminal of AC motor M.

Capacitor C smoothes the voltage output from power supply P to inverter circuit 2 .

The switching element SW1 is turned on when the pulse width modulation signal S1 output from the control circuit 3 is at a high level, and is turned off when the pulse width modulation signal S1 is at a low level. The switching element SW2 is turned on when the pulse width modulation signal S2 output from the control circuit 3 is at a high level, and is turned off when the pulse width modulation signal S2 is at a low level. The switching element SW3 is turned on when the pulse width modulation signal S3 output from the control circuit 3 is at a high level, and is turned off when the pulse width modulation signal S3 is at a low level. The switching element SW4 is turned on when the pulse width modulation signal S4 output from the control circuit 3 is at a high level, and turned off when the pulse width modulation signal S4 is at a low level. The switching element SW5 is turned on when the pulse width modulation signal S5 output from the control circuit 3 is at a high level, and is turned off when the pulse width modulation signal S5 is at a low level. The switching element SW6 is turned on when the pulse width modulation signal S6 output from the control circuit 3 is at a high level, and is turned off when the pulse width modulation signal S6 is at a low level. Note that the carrier wave may be a triangular wave, a sawtooth wave, a reverse sawtooth wave, or the like.

By turning on and off the switching elements Sw1 to SW6, the DC voltage output from the power supply P is converted into AC voltages Vu, Vv, and Vw whose phases differ by 120 degrees from each other. Then, AC voltage Vu is applied to the U-phase input terminal of AC motor M, AC voltage Vv is applied to the V-phase input terminal of AC motor M, and AC voltage Vw is applied to the W-phase input terminal of AC motor M. By being applied, alternating currents Iu, Iv, and Iw whose phases differ by 120 degrees from each other flow through the alternating current motor M, and the rotor of the alternating current motor M rotates.

Current sensor Si1 includes a Hall element, a shunt resistor, and the like, and detects alternating current Iu flowing in the U phase of alternating current motor M, and outputs the detected alternating current Iu to control circuit 3. Further, the current sensor Si2 includes a Hall element, a shunt resistor, and the like, and detects the alternating current Iv flowing in the V phase of the alternating current motor M, and outputs the detected alternating current Iv to the control circuit 3.

The control circuit 3 includes a drive circuit 4, a calculation section 5, and a storage section 6. Note that the storage unit 6 is configured with a RAM (Random Access Memory), a ROM (Read Only Memory), or the like.

The drive circuit 4 is composed of an IC (Integrated Circuit) and the like, and receives the U-phase voltage command value Vu*, V-phase voltage command value Vv*, and W-phase voltage command value Vw* output from the calculation unit 5 and a carrier wave. A comparison is made, and pulse width modulation signals S1 to S6 corresponding to the comparison results are outputted to respective gate terminals of switching elements SW1 to SW6.

For example, when the U-phase voltage command value Vu* is equal to or higher than the carrier wave, the drive circuit 4 outputs the high-level pulse width modulation signal S1 and the low-level pulse width modulation signal S2, and outputs the U-phase voltage command value Vu*. When Vu* is smaller than the carrier wave, a low-level pulse width modulation signal S1 is output, and a high-level pulse width modulation signal S2 is output. Further, when the V-phase voltage command value Vv* is equal to or higher than the carrier wave, the drive circuit 4 outputs the high-level pulse width modulation signal S3 and the low-level pulse width modulation signal S4, and outputs the V-phase voltage command value Vv*. When Vv* is smaller than the carrier wave, a low-level pulse width modulation signal S3 is output, and a high-level pulse width modulation signal S4 is output. Further, when the W-phase voltage command value Vw* is equal to or higher than the carrier wave, the drive circuit 4 outputs the high-level pulse width modulation signal S5 and the low-level pulse width modulation signal S6, and outputs the W-phase voltage command value Vw*. When Vw* is smaller than the carrier wave, a low-level pulse width modulation signal S5 is output, and a high-level pulse width modulation signal S6 is output.

The calculation section 5 is composed of a microcomputer or the like, and includes a rotation speed calculation section 7, a subtraction section 8, a torque control section 9, a torque/current command value conversion section 10, a coordinate conversion section 11, a subtraction section 12, and the like. , a subtraction section 13, a current control section 14, a correction value output section 15, an addition section 16, an addition section 17, and a coordinate conversion section 18. For example, by executing the program stored in the storage unit 6 by the microcomputer, the rotation speed calculation unit 7, subtraction unit 8, torque control unit 9, torque/current command value conversion unit 10, coordinate conversion unit 11, subtraction section 12, subtraction section 13, current control section 14, correction value output section 15, addition section 16, addition section 17, and coordinate transformation section 18.

The rotation speed calculation section 7 calculates the rotation speed ω of the AC motor M using the phase θ detected by the electrical angle detection section Sp. For example, the rotation speed calculation section 7 calculates the rotation speed ω by dividing the phase θ by a predetermined time T (such as the operating clock of the calculation section 5).

The subtraction unit 8 calculates the difference Δω between the rotation speed command value ω* input from the outside and the rotation speed ω output from the rotation speed calculation unit 7.

The torque control section 9 uses the difference Δω output from the subtraction section 8 to obtain a torque command value T*. For example, the torque control unit 9 refers to information stored in the storage unit 6 in which the rotational speed ω of the AC motor M and the torque of the AC motor M are correlated with each other, and determines the rotation rate corresponding to the difference Δω. The torque corresponding to the number ω is determined as the torque command value T*.

The torque/current command value conversion unit 10 converts the torque command value T* output from the torque control unit 9 into a d-axis current command value Id* and a q-axis current command value Iq*. For example, the torque/current command value conversion unit 10 associates the torque of the AC motor M with the d-axis current command value Id* and the q-axis current command value Iq* stored in the storage unit 6. With reference to the information, a d-axis current command value Id* and a q-axis current command value Iq* corresponding to the torque corresponding to the torque command value T* are determined.

The coordinate conversion unit 11 determines the alternating current Iw flowing in the W phase of the alternating current motor M using the alternating current Iu detected by the current sensor Si1 and the alternating current Iv detected by the current sensor Si2. Note that the currents detected by the current sensors Si1 and Si2 are not limited to the combination of alternating currents Iu and Iv, but may be a combination of alternating currents Iv and Iw or a combination of alternating currents Iu and Iw. When alternating currents Iv and Iw are detected by current sensors Si1 and Si2, coordinate conversion unit 11 uses alternating currents Iv and Iw to obtain alternating current Iu. Furthermore, when the current sensors Si1 and Si2 detect the alternating currents Iu and Iw, the coordinate conversion unit 11 uses the alternating currents Iu and Iw to obtain the alternating current Iv.

Further, the coordinate conversion unit 11 uses the phase θ detected by the electrical angle detection unit Sp to transform the alternating currents Iu, Iv, and Iw into a d-axis current Id (current component for generating field weakening) and a q-axis current component. Convert to current Iq (current component for generating torque). For example, the coordinate conversion unit 11 converts alternating currents Iu, Iv, and Iw into a d-axis current Id and a q-axis current Iq using a conversion matrix C1 shown in Equation 1 below.

Further, when the inverter circuit 2 further includes a current sensor Si3 that detects the AC current Iw flowing in the W phase of the AC motor M in addition to the current sensors Si1 and Si2, the coordinate conversion unit 11 uses the electrical angle detection unit Sp to The detected phase θ may be used to convert the alternating currents Iu, Iv, and Iw detected by the current sensors Si1 to Si3 into the d-axis current Id and the q-axis current Iq.

The subtraction unit 12 calculates the difference ΔId between the d-axis current command value Id* output from the torque/current command value conversion unit 10 and the d-axis current Id output from the coordinate conversion unit 11.

The subtraction unit 13 calculates the difference ΔIq between the q-axis current command value Iq* output from the torque/current command value conversion unit 10 and the q-axis current Iq output from the coordinate conversion unit 11.

The current control unit 14 calculates the d-axis voltage command value Vd* and the q-axis voltage command value Vq* by PI control using the difference ΔId output from the subtraction unit 12 and the difference ΔIq output from the subtraction unit 13. For example, the current control unit 14 calculates the d-axis voltage command value Vd* using Equation 2 below, and calculates the q-axis voltage command value Vq* using Equation 3 below. In addition, Kp is the constant of the proportional term of PI control, Ki is the constant of the integral term of PI control, Lq is the q-axis inductance of the coil that constitutes the AC motor M, and Ld is the d of the coil that constitutes the AC motor M. It is assumed that the shaft inductance is the shaft inductance, ω is the rotation speed of the rotor of the AC motor M, and Ke is the induced voltage constant.

d-axis voltage command value Vd* = Kp x difference ΔId + Ki x ∫ (difference ΔId) - ωLqIq...Formula 2

Q-axis voltage command value Vq*=Kp×difference ΔIq+Ki×∫ (difference ΔIq)+ωLdId+ωKe...Formula 3

The correction value output unit 15 outputs the d-axis current command value Id* and the q-axis current command value Iq* output from the torque/current command value conversion unit 10 and the d-axis current Id and q-axis output from the coordinate conversion unit 11. A correction value v_dc* and a correction value v_qc* are output using the current Iq.

The adding unit 16 corrects the sum of the d-axis voltage command value Vd* (d-axis voltage command value before correction) output from the current control unit 14 and the correction value v_qc* output from the correction value output unit 15. It is output as the subsequent d-axis voltage command value Vd**.

The addition unit 17 corrects the sum of the q-axis voltage command value Vq* (q-axis voltage command value before correction) output from the current control unit 14 and the correction value v_dc* output from the correction value output unit 15. Output as the subsequent q-axis voltage command value Vq**.

The coordinate conversion unit 18 converts the d-axis voltage command value Vd** and the q-axis voltage command value Vq** into the U-phase voltage command value Vu* and the V-phase voltage command value using the phase θ detected by the electrical angle detection unit Sp. It is converted into a voltage command value Vv* and a W-phase voltage command value Vw*. For example, the coordinate conversion unit 18 converts the d-axis voltage command value Vd** and the q-axis voltage command value Vq** into the U-phase voltage command value Vu* and the V-phase voltage using the transformation matrix C2 shown in Equation 4 below. It is converted into a command value Vv* and a W-phase voltage command value Vw*.

FIG. 2 is a diagram showing the correction value output section 15.

The correction value output unit 15 shown in FIG. 2 includes a low-pass filter 151 (first low-pass filter), a low-pass filter 152 (second low-pass filter), an adjustment unit 153 (first adjustment unit), and an adjustment unit 154 (second adjustment section) and a non-interference control section 155.

The low-pass filter 151 suppresses high frequency components of the d-axis current command value Id* output from the torque/current command value converter 10 and outputs the d-axis current command value Id**. Note that it is assumed that the response speed of the low-pass filter 151 changes depending on the cutoff frequency ωcd that the low-pass filter 151 has.

The low-pass filter 152 suppresses high frequency components of the q-axis current command value Iq* output from the torque/current command value converter 10 and outputs the q-axis current command value Iq**. Note that it is assumed that the response speed of the low-pass filter 152 changes depending on the cutoff frequency ωcq that the low-pass filter 152 has.

The adjustment unit 153 adjusts the low-pass so that the first difference between the d-axis current command value Id** output from the low-pass filter 151 and the d-axis current Id output from the coordinate conversion unit 11 is equal to or less than a first threshold value. The cutoff frequency ωcd of the filter 151 is adjusted. For example, the first threshold value is an arbitrary value in the range from the minimum value Idmin (such as zero) of the first difference to a predetermined value Idref larger than the minimum value Idmin. For example, the predetermined value Idref is the sum of the amount of change in the d-axis current command value Id* required to change the response speed of the d-axis current command value Id* in the current control unit 14 by 5% and the minimum value Idmin. value. When the first threshold value is set to the minimum value Idmin, the current responsiveness can be further improved compared to when the first threshold value is set to a value larger than the minimum value Idmin.

For example, the adjustment unit 153 calculates the cutoff frequency ωcd that minimizes the first difference by the weighted least squares method using the evaluation function shown in Equation 5 below and the algorithm shown in Equation 6 below. Note that y _i is expressed by the following formula 7, and θ ^T z _i is expressed by the following formula 8. Further, λ is a weighting coefficient, and 0<λ≦1.

y _i =d-axis current Id...Equation 7

θ ^T z _i = d-axis current command value Id** = (1 - cutoff frequency ωcd x predetermined time T) x d-axis current command value Id** _k-1 + cutoff frequency ωcd x predetermined time T x d-axis Current command value Id* _k-1 ...Formula 8

The adjustment unit 154 performs low-pass control so that the second difference between the q-axis current command value Iq** output from the low-pass filter 152 and the q-axis current Iq output from the coordinate conversion unit 11 is equal to or less than a second threshold value. The cutoff frequency ωcq of the filter 152 is adjusted. For example, the second threshold value is an arbitrary value in the range from the minimum value Iqmin (such as zero) of the second difference to a predetermined value Iqref larger than the minimum value Iqmin. For example, the predetermined value Iqref is the sum of the amount of change in the q-axis current command value Iq* necessary to change the response speed of the q-axis current command value Iq* in the current control unit 14 by 5% and the minimum value Iqmin. value. When the second threshold value is set to the minimum value Iqmin, the current responsiveness can be further improved compared to when the second threshold value is set to a value larger than the minimum value Iqmin.

For example, the adjustment unit 154 calculates the cutoff frequency ωcq that minimizes the second difference by the weighted least squares method using the evaluation function shown in Equation 5 above and the algorithm shown in Equation 6 above. Note that y _i is expressed as the following formula 9, and θ ^T z _i is expressed as the following formula 10.

y _i =q-axis current Iq...Equation 9

θ ^T z _i = q-axis current command value Iq** = (1 - cutoff frequency ωcq x predetermined time T) x q-axis current command value Iq** _k-1 + cutoff frequency ωcq x predetermined time T x q-axis Current command value Iq* _k-1 ...Formula 10

Note that the adjustment timing of the cutoff frequencies ωcd and ωcq is not particularly limited. For example, the adjustment units 153 and 154 adjust the cutoff frequencies ωcd and ωcq when the AC motor M starts driving. Alternatively, the adjustment units 153 and 154 repeatedly adjust the cutoff frequencies ωcd and ωcq while the AC motor M is being driven. When the cutoff frequencies ωcd and ωcq are repeatedly adjusted while the AC motor M is being driven, even if the response speed in PI control changes due to deterioration of the AC motor M while the AC motor M is being driven, the change will not occur. Since the response speeds of the low-pass filters 151 and 152 can be changed in accordance with the response speed, current responsiveness can be maintained.

The non-interference control unit 155 sets the d-axis voltage command value Vd* corresponding to the variation in the d-axis current command value Id** output from the low-pass filter 151 due to the interference of the q-axis current Iq with the d-axis current Id. The q-axis voltage command value Vq* corresponds to the variation in the q-axis current command value Iq** outputted from the low-pass filter 152 due to the interference of the d-axis current Id with the q-axis current Iq while being output as the correction value v_dc*. is output as a correction value v_qc*. For example, the non-interference control unit 155 uses the multiplication value of the d-axis current command value Id** and the d-axis inductance Ld as the correction value v_dc*, and the multiplication value of the q-axis current command value Iq** and the q-axis inductance Lq. is the correction value v_qc*. Then, the d-axis voltage command value Vd* and the correction value v_dc* are added to correct the d-axis voltage command value Vd*, and the q-axis voltage command value Vq* and the correction value v_qc* are added to By correcting the voltage command value Vq*, the fluctuation of the d-axis current command value Id* due to the interference of the q-axis current Iq with the d-axis current Id, and the interference of the d-axis current Id with the q-axis current Iq. The fluctuations in the q-axis current command value Iq* due to the above cancel each other out, making it possible to improve current responsiveness.

The control device 1 of the embodiment uses a low-pass filter so that the first difference between the d-axis current command value Id** output from the low-pass filter 151 and the d-axis current Id, which is the actual current, is equal to or less than the first threshold value. The second difference between the q-axis current command value Iq** outputted from the adjustment unit 153 that adjusts the cutoff frequency ωcd of 151 and the low-pass filter 152 and the q-axis current Iq that is the actual current is less than or equal to the second threshold value. This configuration includes an adjustment section 154 that adjusts the cutoff frequency ωcq of the low-pass filter 152 so that In this way, the cutoff frequencies ωcd and ωcq can be automatically adjusted by the adjustment units 153 and 154, so compared to the conventional case where the cutoff frequencies ωcd and ωcq are adjusted by experiments, simulations, etc. The number of man-hours required for adjusting the cutoff frequencies ωcd and ωcq can be reduced.

Note that the present invention is not limited to the above-described embodiments, and various improvements and changes can be made without departing from the gist of the present invention.

1 Control device 2 Inverter circuit 3 Control circuit 4 Drive circuit 5 Arithmetic unit 6 Storage unit 7 Rotation speed computing unit 8 Subtraction unit 9 Torque control unit 10 Torque/current command value conversion unit 11 Coordinate conversion unit 12 Subtraction unit 13 Subtraction unit 14 Current Control section 15 Correction value output section 16 Addition section 17 Addition section 18 Coordinate transformation sections 151, 152 Low pass filters 153, 154 Adjustment section 155 Non-interference control section

Claims (2)

an inverter circuit that drives an AC motor based on a comparison result between a carrier wave and a voltage command value;
The current flowing through the AC motor is converted into a d-axis current and a q-axis current, and a d-axis voltage command value is calculated by PI control so that the difference between the d-axis current and the d-axis current command value is small, and the q-axis current is Calculate the q-axis voltage command value so that the difference between the axis current and the q-axis current command value is small, and apply the corrected d-axis voltage command value and the corrected q-axis voltage command value to the voltage command value. A control circuit to convert,
Equipped with
The control circuit includes:
a first low-pass filter into which the d-axis current command value is input;
a second low-pass filter into which the q-axis current command value is input;
adjusting the cutoff frequency of the first low-pass filter so that a first difference between the d-axis current command value output from the first low-pass filter and the d-axis current is equal to or less than a first threshold; 1 adjustment section;
adjusting the cutoff frequency of the second low-pass filter so that a second difference between the q-axis current command value output from the second low-pass filter and the q-axis current is equal to or less than a second threshold; 2 adjustment section;
outputting, as a first correction value, a d-axis voltage command value corresponding to a variation in the d-axis current command value output from the first low-pass filter due to interference of the q-axis current with the d-axis current; A non-controller that outputs a q-axis voltage command value as a second correction value corresponding to a variation in the q-axis current command value output from the second low-pass filter due to interference of the d-axis current with the q-axis current. an interference control section;
a first addition unit that outputs an added value of the d-axis voltage command value before correction and the second correction value as the d-axis voltage command value after correction;
a second addition unit that outputs an added value of the q-axis voltage command value before correction and the first correction value as the q-axis voltage command value after correction;
A control device for an AC motor, comprising: The AC motor control device according to claim 1 ,
The control device for an AC motor, wherein the first and second adjustment units repeatedly adjust cutoff frequencies of the first and second low-pass filters while the AC motor is being driven.

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