JP2021007287A - Synchronous motor control device - Google Patents

Abstract

To obtain a configuration that can accurately control a d-axis current and a q-axis current even in a case of rectangular wave drive control in a control device that switches drive control of a synchronous motor between PWM drive control and rectangular wave drive control.SOLUTION: A control device 1 that controls a drive of a motor 2 includes a current command generation unit 10, a voltage command generation unit, a PWM signal generation unit, a rectangular wave signal generation unit, a control switching unit, and a main circuit 50. The current command generation unit 10 generates a current command so that a voltage utilization rate does not exceed a predetermined voltage utilization rate in which current flowing through the motor 2 is equal in a case of minimum current control by PWM drive and in a case of rectangular wave drive control. The control switching unit inputs a voltage command to the PWM signal generation unit when the voltage utilization rate is smaller than the predetermined voltage utilization rate, while inputting the voltage command to the rectangular wave signal generation unit when the voltage utilization rate is the predetermined voltage utilization rate.SELECTED DRAWING: Figure 1

Description

The present invention relates to a control device that controls the drive of a synchronous motor.

As a control method for controlling the drive of the synchronous motor, PWM drive control using a PWM signal and square wave drive control using a pulsed square wave signal are known. In the PWM drive control, a voltage within the range of the voltage waveform of the sine wave output from the control device of the synchronous motor can be applied to the synchronous motor. On the other hand, in the square wave drive control, since the voltage is applied to the synchronous motor in a pulsed manner, the maximum voltage input to the control device of the synchronous motor can be applied to the synchronous motor. Therefore, in general, the voltage utilization rate in the rectangular wave drive control is higher than the voltage utilization rate in the PWM drive control. Here, the voltage utilization rate is obtained by dividing the effective line voltage value by the input voltage.

In order to improve the voltage utilization rate of the synchronous motor, a method of switching between the PWM drive control and the rectangular wave drive control is used as the control method of the synchronous motor. As a configuration for switching between the PWM drive control and the rectangular wave drive control in this way, for example, the configuration disclosed in Patent Document 1 is known.

Patent Document 1 discloses a drive control device for an AC motor that switches between a PWM current control mode and a rectangular wave voltage phase control mode according to the current phase of the AC current supplied to the AC motor. In the PWM current control mode, the drive control device disclosed in Patent Document 1 generates a current command based on a torque command, and generates a voltage command from the current command. When this voltage command is input to the PWM circuit, a switching command is generated in the PWM circuit. Further, in the rectangular voltage phase control mode, the drive control device obtains a voltage phase by using the difference between the torque command and the detection value of the torque detection unit, and generates a rectangular wave voltage by using the voltage phase.

Japanese Unexamined Patent Publication No. 2005-218299

By the way, in PWM drive control, the amplitude and phase of the output voltage, which is a switching command, can be adjusted. Therefore, when controlling the current of the synchronous motor, the d-axis current and the q-axis current can be controlled individually.

On the other hand, in the rectangular wave drive control, the amplitude of the output voltage, which is the rectangular wave voltage, is constant, and only the phase can be adjusted. Therefore, when the current of the synchronous motor is controlled, the d-axis current and the q-axis current flowing through the synchronous motor cannot be controlled individually. Therefore, the command values of the d-axis current and the q-axis current may deviate from the actual d-axis current and q-axis current. In this case, the torque of the synchronous motor cannot be accurately controlled by the rectangular wave drive control.

In the case of the square wave drive control, generally, as disclosed in Patent Document 1 described above, the square wave voltage is determined by the voltage phase obtained by comparing the torque command and the torque feedback value. Control the phase. In this case, the d-axis current and the q-axis current are not controlled.

An object of the present invention is to obtain a configuration in which a control device that switches drive control of a synchronous motor between PWM drive control and square wave drive control can accurately control d-axis current and q-axis current even in the case of square wave drive control. There is.

The control device for a synchronous motor according to an embodiment of the present invention is a control device for a synchronous motor that controls the drive of the synchronous motor. This control device includes a current command generation unit that generates a current command from a torque command, a voltage command generation unit that generates a voltage command based on the current command, and a PWM signal generation unit that generates a PWM signal based on the voltage command. The voltage command is input to one of the unit, the rectangular wave signal generation unit that generates a rectangular wave signal based on the voltage command, and the PWM signal generation unit and the rectangular wave signal generation unit according to the voltage utilization rate. It includes a control switching unit and a drive control unit that controls the drive of the synchronous electric motor by using the signal generated by the PWM signal generation unit or the rectangular wave signal generation unit. When the voltage utilization rate of the current command generator is equal between the case where the synchronous electric motor is driven by the PWM signal with the minimum current and the case where the synchronous electric motor is driven by the rectangular wave signal, the current flowing through the synchronous electric motor is equal. The current command is generated so as not to exceed the predetermined voltage utilization rate, and when the voltage utilization rate is smaller than the predetermined voltage utilization rate, the control switching unit outputs the voltage to the PWM signal generation unit. While inputting a command, when the voltage utilization rate is the predetermined voltage utilization rate, the voltage command is input to the rectangular wave signal generation unit (first configuration).

With this configuration, in a control device including a PWM signal generation unit that generates a PWM signal and a rectangular wave signal generation unit that generates a rectangular wave signal, the voltage utilization rate drives the synchronous electric motor with the minimum current by the PWM signal. A current command is generated so that the currents flowing through the synchronous electric motor do not exceed a predetermined voltage utilization rate when the synchronous electric motor is driven by the rectangular wave signal and the voltage utilization rate is the predetermined voltage. If it is smaller than the utilization rate, PWM drive control can be performed, while if the voltage utilization rate is the predetermined voltage utilization rate, rectangular wave drive control can be performed. As a result, it is possible to switch between PWM drive control and square wave drive control using the current command generated by one controller. Therefore, the configuration of the control device can be simplified.

Further, when the voltage utilization rate is the predetermined voltage utilization rate, the minimum current in the PWM drive control and the current in the rectangular wave drive control are equal to each other. Therefore, when the voltage utilization rate reaches the predetermined voltage utilization rate, the change in the current at the time of switching the control can be suppressed by switching between the PWM drive control and the rectangular wave drive control. As a result, it is possible to prevent the occurrence of disturbance of the current waveform when switching the control.

Further, as described above, when the voltage utilization rate reaches the predetermined voltage utilization rate, by switching from the PWM drive control to the rectangular wave drive control, the d-axis current and the q-axis current in the rectangular wave drive control Both can be controlled accurately.

In the first configuration, the current command includes a d-axis current command. The current command generation unit corrects the d-axis current command so that the voltage utilization rate becomes the predetermined voltage utilization rate when the voltage utilization rate is larger than the predetermined voltage utilization rate. It has a field weakening control unit that obtains a current command correction value (second configuration).

As a result, even in the case of rectangular wave drive control, the current can be controlled with high accuracy by controlling the d-axis current.

In the first or second configuration, the voltage when a current equal to that of the synchronous motor flows between the case where the synchronous motor is driven by the PWM signal with the minimum current and the case where the synchronous motor is driven by the rectangular wave signal. The utilization rate is 0.78 (third configuration).

As a result, PWM drive control or square wave drive control can be performed as drive control of the synchronous motor in accordance with the voltage utilization rate of 0.78 of the square wave drive control. Therefore, in PWM drive control and square wave drive control, The current can be controlled accurately. Moreover, since a dedicated control unit is not required for each control, the configuration of the control device can be simplified.

According to the control device of the synchronous motor according to the embodiment of the present invention, the control device includes a current command generation unit, a voltage command generation unit, a PWM signal generation unit, a square wave signal generation unit, a control switching unit, and a drive control unit. Has. The current command generator has a predetermined voltage utilization rate when the current flowing through the synchronous motor is equal between the case where the synchronous motor is driven by the PWM signal with the minimum current and the case where the synchronous motor is driven by the rectangular wave signal. Generate a current command so that the voltage utilization rate is not exceeded. The control switching unit inputs a voltage command to the PWM signal generation unit when the voltage utilization rate is smaller than the predetermined voltage utilization rate, while the voltage utilization rate is the predetermined voltage utilization rate. A voltage command is input to the square wave signal generation unit. As a result, PWM drive control and square wave drive control can be performed by the current command, so that the control device can be simplified. Further, in the PWM drive control and the rectangular wave drive control, the current can be controlled with high accuracy.

FIG. 1 is a control block diagram showing a schematic configuration of a control device according to an embodiment. FIG. 2 is a control block diagram showing a schematic configuration of a current control unit. FIG. 3 is a flowchart showing a control switching operation in the control device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

(overall structure)
FIG. 1 is a block diagram showing a schematic configuration of a control device 1 according to an embodiment of the present invention. The control device 1 generates the q-axis current command Iq_ref and the d-axis current command Id_ref based on the torque command as the input command, and then the current control unit 20 performs PWM based on the q-axis current command Iq_ref and the d-axis current command Id_ref. Generate a signal or square wave signal. Further, the control device 1 drives and controls the motor 2 (synchronous motor) by the main circuit 50 by using the PWM signal or the square wave signal generated by the current control unit 20. In the present embodiment, the motor 2 is a three-phase AC motor having a rotor and a stator, but the motor 2 may be a motor having any configuration.

The control device 1 includes a current command generation unit 10, a current control unit 20, a main circuit 50 (drive control unit), a three-phase two-phase conversion unit 60, a current sensor 70, and a position sensor 80.

The current sensor 70 detects the U-phase and W-phase currents among the currents supplied from the main circuit 50 to the motor 2. The detected current is input to the three-phase two-phase converter 60 as the U-phase current feedback value Iu_fb and the W-phase current feedback value Iw_fb.

The position sensor 80 detects the rotation position of a rotor (not shown) of the motor 2 and outputs the rotation position as a signal of the rotation angle. The rotation angle signal output from the position sensor 80 is input to the current control unit 20.

The current command generation unit 10 generates a current command based on the torque command. Specifically, the current command generation unit 10 generates the q-axis current command Iq_ref and the d-axis current command Id_ref based on the torque command T_ref. Further, when the current command generation unit 10 generates the d-axis current command Id_ref based on the torque command T_ref, the d-axis current command correction value Id_ref0 generated by the field weakening control unit 13 described later is also taken into consideration. Generates the current command Id_ref.

Specifically, the current command generation unit 10 includes a d-axis current command generation unit 11, a q-axis current command generation unit 12, and a field weakening control unit 13.

The d-axis current command generation unit 11 generates the d-axis current command Id_ref by using the torque command T_ref and the d-axis current command correction value Id_ref0 generated by the field weakening control unit 13 described later. The d-axis current command generation unit 11 has a d-axis current command conversion unit 11a and an addition unit 11b. The d-axis current command conversion unit 11a converts the torque command T_ref into the d-axis current command initial value Id_ref1, which is the minimum current in the d-axis current. The addition unit 11b generates the d-axis current command Id_ref by adding the d-axis current command correction value Id_ref0 generated by the field weakening control unit 13 described later to the d-axis current command initial value Id_ref1.

The d-axis current command Id_ref generated by the d-axis current command generation unit 11 is input to the q-axis current command generation unit 12, the current control unit 20, and the field weakening control unit 13.

The q-axis current command generation unit 12 generates the q-axis current command Iq_ref from the d-axis current command Id_ref generated by the d-axis current command generation unit 11. The q-axis current command Iq_ref generated by the q-axis current command generation unit 12 is input to the current control unit 20 and the field weakening control unit 13.

The field weakening control unit 13 uses the d-axis current command Id_ref generated by the d-axis current command generation unit 11, the q-axis current command Iq_ref generated by the q-axis current command generation unit 12, and the input DC voltage of the main circuit 50. Based on this, the voltage utilization rate is calculated, and when the voltage utilization rate is larger than the voltage utilization command value, the result of PI calculation using those differences is output as the d-axis current command correction value Id_ref0.

The field weakening control unit 13 includes a voltage conversion unit 15, a line voltage effective value calculation unit 16, a voltage utilization rate calculation unit 17, a voltage utilization rate comparison unit 18, a PI calculation unit 19, and a determination unit 30. ..

The voltage conversion unit 15 converts the q-axis current command Iq_ref and the d-axis current command Id_ref into the q-axis voltage Vq and the d-axis voltage Vd. Specifically, the voltage conversion unit 15 obtains the q-axis voltage Vq and the d-axis voltage Vd by the following equations (1) and (2).
Vd = R ・ Id−ω ・ Lq ・ Iq (1)
Vq = R ・ Iq + ω ・ (φm + Ld ・ Id) (2)

Here, R is the winding resistance of the motor 2, ω is the rotation angle speed of the motor 2, Ld is the d-axis inductance, Lq is the q-axis inductance, and φm is the maximum interlinkage magnetic flux of the motor 2. The value.

The line voltage effective value calculation unit 16 obtains the line voltage effective value by using the q-axis voltage Vq and the d-axis voltage Vd obtained by the voltage conversion unit 15. Specifically, the line voltage effective value calculation unit 16 obtains the line voltage effective value by the following equation (3).
Line voltage effective value = √ (Vd ^ 2 + Vq ^ 2) (3)

The voltage utilization rate calculation unit 17 calculates the voltage utilization rate from the line voltage effective value obtained by the line voltage effective value calculation unit 16 and the input DC voltage of the main circuit 50. Specifically, the voltage utilization rate calculation unit 17 obtains the voltage utilization rate by the following equation (4).
Voltage utilization rate = effective line voltage / input DC voltage (4)

The voltage utilization rate comparison unit 18 compares the voltage utilization rate calculated by the voltage utilization rate calculation unit 17 with the voltage utilization rate command value, and outputs the comparison result. Specifically, the voltage utilization rate comparison unit 18 outputs the difference of the voltage utilization rate with respect to the voltage utilization rate command value.

The voltage utilization command value may be preset or may be changed by input. In the present embodiment, the voltage utilization command value is set to 0.78, which is the voltage utilization rate in the case of a rectangular wave signal. When the voltage utilization rate is 0.78, the current flowing through the motor 2 during the minimum current control by PWM drive and the current flowing through the motor 2 during the square wave drive control are equal. That is, the voltage utilization command value is set to the voltage utilization when the current flowing through the motor 2 is equal between the case where the motor 2 is driven by the PWM signal with the minimum current and the case where the motor 2 is driven by the rectangular wave signal. To. The voltage utilization command value corresponds to a predetermined voltage utilization.

When the difference obtained by the voltage utilization rate comparison unit 18 is negative, the determination unit 30 outputs the difference obtained by the voltage utilization rate comparison unit 18 to the PI calculation unit 19 as it is. On the other hand, when the difference obtained by the voltage utilization comparison unit 18 is zero or more, the determination unit 30 outputs zero to the PI calculation unit 19 regardless of the value of the difference obtained by the voltage utilization comparison unit 18. ..

That is, the determination unit 30 calculates the difference obtained by the voltage utilization rate comparison unit 18 only when the voltage utilization rate calculated by the voltage utilization rate calculation unit 17 is larger than the voltage utilization rate command value. Output to.

The PI calculation unit 19 performs PI calculation on the output result of the voltage utilization rate comparison unit 18 to obtain the d-axis current command correction value Id_ref0. The d-axis current command correction value Id_ref0 is a value for correcting the d-axis current command Id_ref so that the voltage utilization rate does not exceed the voltage utilization command value. As described above, the determination unit 30 calculates the difference obtained by the voltage utilization rate comparison unit 18 only when the voltage utilization rate calculated by the voltage utilization rate calculation unit 17 is larger than the voltage utilization rate command value. Output to the calculation unit 19. Therefore, the PI calculation unit 19 outputs the d-axis current command correction value Id_ref0 only when the voltage utilization rate calculated by the voltage utilization rate calculation unit 17 is larger than the voltage utilization command value. The d-axis current command correction value Id_ref0 obtained by the PI calculation unit 19 is input to the addition unit 11b of the d-axis current command generation unit 11.

With the configuration of the current command generation unit 10 as described above, the q-axis current command Iq_ref and the d-axis current command Id_ref can be generated by using the torque command and the voltage utilization rate. The current command generation unit 10 can generate the q-axis current command Iq_ref and the d-axis current command Id_ref so that the voltage utilization rate does not exceed the voltage utilization rate command value by the field weakening control unit 13.

The q-axis current command Iq_ref and the d-axis current command Id_ref generated by the current command generation unit 10 are input to the current control unit 20.

The current control unit 20 generates a PWM signal or a square wave signal according to the voltage utilization rate based on the input q-axis current command Iq_ref and d-axis current command Id_ref, and outputs the generated signal to the main circuit 50. To do. The detailed configuration of the current control unit 20 is shown in FIG.

The current control unit 20 includes a voltage command generation unit 21, a control switching unit 22, a PWM signal generation unit 23, and a rectangular wave signal generation unit 24.

The voltage command generation unit 21 generates the q-axis voltage command Vq_ref using the q-axis current command Iq_ref generated by the current command generation unit 10 and the q-axis current feedback value Iq_fb which is the feedback value of the input current of the motor 2. .. Further, the voltage command generation unit 21 uses the d-axis current command Id_ref generated by the current command generation unit 10 and the d-axis current feedback value Id_fb, which is the feedback value of the input current of the motor 2, to generate the d-axis voltage command Vd_ref. Generate.

The voltage command generation unit 21 includes a q-axis current feedback unit 21a, a q-axis current PI calculation unit 21b, a d-axis current feedback unit 21c, and a d-axis current PI calculation unit 21d.

The q-axis current feedback unit 21a subtracts the q-axis current feedback value Iq_fb from the q-axis current command Iq_ref to obtain the q-axis current command correction value. The q-axis current PI calculation unit 21b generates the q-axis voltage command Vq_ref by performing PI calculation on the q-axis current command correction value.

The d-axis current feedback unit 21c subtracts the d-axis current feedback value Id_fb from the d-axis current command Id_ref to obtain the d-axis current command correction value. The d-axis current PI calculation unit 21d generates the d-axis voltage command Vd_ref by performing PI calculation on the d-axis current command correction value.

The control switching unit 22 switches the drive control of the motor 2 to PWM drive control or rectangular wave drive control according to the voltage utilization rate. Specifically, when the voltage utilization rate is smaller than the voltage utilization rate command value, the control switching unit 22 inputs the q-axis voltage command Vq_ref and the d-axis voltage command Vd_ref to the PWM signal generation unit 23 described later. On the other hand, when the voltage utilization rate is the same as the voltage utilization rate command value, the q-axis voltage command Vq_ref and the d-axis voltage command Vd_ref are input to the rectangular wave signal generation unit 24 described later.

The control switching unit 22 obtains the line voltage effective value by the above equation (3) using the q-axis voltage command Vq_ref and the d-axis voltage command Vd_ref, and the line voltage effective value and the main circuit 50. The voltage utilization rate is obtained by the above equation (4) using the input DC voltage of. The control switching unit 22 switches the drive control of the motor 2 to PWM drive control or rectangular wave drive control by using the obtained voltage utilization rate.

The PWM signal generation unit 23 uses the input q-axis voltage command Vq_ref and d-axis voltage command Vd_ref to generate a PWM signal for input to the switching element described later in the main circuit 50. Specifically, the PWM signal generation unit 23 has a two-phase three-phase conversion unit 23a and a triangular wave comparison unit 23b.

The two-phase three-phase conversion unit 23a converts the q-axis voltage command Vq_ref and the d-axis voltage command Vd_ref into three-phase voltages Vu, Vv, Vw. The two-phase three-phase conversion unit 23a converts the rotation angle signal of the motor 2 detected by the position sensor 80 when converting the q-axis voltage command Vq_ref and the d-axis voltage command Vd_ref into the three-phase voltages Vu, Vv, Vw. Use. The triangular wave comparison unit 23b generates a PWM signal by comparing the three-phase voltages Vu, Vv, and Vw with the triangular wave signal. Since the processing operations of the two-phase three-phase conversion unit 23a and the triangular wave comparison unit 23b are the same as those in the prior art, detailed description thereof will be omitted.

The PWM signal generated by the triangular wave comparison unit 23b is input to the main circuit 50. In the main circuit 50, a switching element (not shown) performs an on / off operation in response to a PWM signal. As a result, current is supplied from the main circuit 50 to each of the three phases of the motor 2.

The square wave signal generation unit 24 uses the input q-axis voltage command Vq_ref and d-axis voltage command Vd_ref to generate a square wave signal to be input to the switching element described later in the main circuit 50. Specifically, the rectangular wave signal generation unit 24 has a voltage phase generation unit 24a and an interrupt processing unit 24b.

The voltage phase generation unit 24a generates a voltage phase signal used for generating a square wave signal based on the q-axis voltage command Vq_ref and the d-axis voltage command Vd_ref. The interrupt processing unit 24b generates a three-phase rectangular wave signal that becomes the voltage phase signal generated by the voltage phase generation unit 24a. The interrupt processing unit 24b uses the rotation angle signal of the motor 2 detected by the position sensor 80 when generating the rectangular wave signal. Since the processing operations of the voltage phase generation unit 24a and the interrupt processing unit 24b are the same as those in the prior art, detailed description thereof will be omitted.

The main circuit 50 has a plurality of switching elements (not shown). The plurality of switching elements perform on / off operations in response to a PWM signal or a square wave signal generated by the current control unit 20. As a result, a current having a predetermined waveform is supplied from the main circuit 50 to the motor 2. Therefore, the control device 1 controls the drive of the motor 2.

The three-phase two-phase conversion unit 60 converts the U-phase current feedback value Iu_fb and the W-phase current feedback value Iw_fb detected by the current sensor 70 into the q-axis current feedback value Iq_fb and the d-axis current feedback value Id_fb.

Since the configurations of the main circuit 50 and the three-phase two-phase converter 60 are the same as those of the conventional configuration, detailed description of the main circuit 50 and the three-phase two-phase converter 60 will be omitted.

From the above, in the present embodiment, the control device 1 that controls the drive of the motor 2 includes a current command generation unit 10 that generates current commands Iq_ref and Id_ref from the torque command T_ref, and voltage commands Vq_ref and Vd_ref from the current commands Iq_ref and Id_ref. 21 and a PWM signal generation unit 23 that generates a PWM signal based on the voltage commands Vq_ref and Vd_ref, and a rectangular wave signal generation unit 24 that generates a rectangular wave signal based on the voltage commands Vq_ref and Vd_ref. The control switching unit 22 that inputs the voltage commands Vq_ref and Vd_ref to one of the PWM signal generation unit 23 and the rectangular wave signal generation unit 24 according to the voltage utilization rate, and the PWM signal generation unit 23 or the rectangular wave signal generation unit 24. The main circuit 50 that controls the drive of the motor 2 by using the signal generated in the above is provided. The current command generation unit 10 determines a predetermined voltage utilization rate when the current flowing through the motor 2 is equal between the case where the motor 2 is driven by the PWM signal with the minimum current and the case where the motor 2 is driven by the rectangular wave signal. The current commands Iq_ref and Id_ref are generated so as not to exceed the voltage utilization rate (in this embodiment, the voltage utilization command value). When the voltage utilization rate is smaller than the voltage utilization command value, the control switching unit 22 inputs the voltage commands Vq_ref and Vd_ref to the PWM signal generation unit, while the voltage utilization rate is the same value as the voltage utilization command value. When becomes, the voltage commands Vq_ref and Vd_ref are input to the square wave signal generation unit.

With this configuration, in the control device 1 including the PWM signal generation unit 23 for generating the PWM signal and the rectangular wave signal generation unit 24 for generating the rectangular wave signal, the voltage utilization rate is the minimum current of the motor 2 by the PWM signal. Current commands Iq_ref and Id_ref are generated so that the voltage utilization command values when the currents flowing through the motor 2 are equal between the case of driving and the case of driving the motor 2 by the rectangular wave signal are generated, and the voltage utilization rate is increased. When the voltage utilization rate command value is smaller than the voltage utilization command value, PWM drive control can be performed, while when the voltage utilization rate becomes the same value as the voltage utilization rate command value, rectangular wave drive control can be performed. As a result, it is possible to switch between PWM drive control and rectangular drive wave control using the current commands Iq_ref and Id_ref generated by one controller. Therefore, the configuration of the control device 1 can be simplified.

When the voltage utilization rate is the same as the voltage utilization rate command value, the minimum current in the PWM drive control and the current in the rectangular wave drive control are equal. Therefore, when the voltage utilization rate is the same as the voltage utilization rate command value, the change in current when switching the control can be suppressed by switching between the PWM drive control and the rectangular wave drive control. As a result, it is possible to prevent the occurrence of disturbance of the current waveform when switching the control.

Further, as described above, when the voltage utilization rate is the same as the voltage utilization rate command value, the d-axis current and the q-axis current in the rectangular wave drive control can be obtained by switching from the PWM drive control to the rectangular wave drive control. Both can be controlled with high accuracy.

Further, in the present embodiment, the current command generation unit 10 determines the d-axis current so that when the voltage utilization rate is larger than the predetermined voltage utilization rate, the voltage utilization rate becomes the predetermined voltage utilization rate. It has a field weakening control unit 13 for obtaining a d-axis current command correction value for correcting a command.

As a result, even in the case of rectangular wave drive control, the current can be controlled with high accuracy by controlling the d-axis current.

The voltage utilization rate when a current equal to that of the motor 2 flows between the case where the motor 2 is driven by the PWM signal with the minimum current and the case where the motor 2 is driven by the square wave signal is 0.78.

As a result, PWM drive control or square wave drive control can be performed as drive control of the motor 2 in accordance with the voltage utilization rate of 0.78 of the square wave drive control. Therefore, in PWM drive control and square wave drive control, The current can be controlled accurately. Moreover, since a dedicated control unit is not required for each control, the configuration of the control device 1 can be simplified.

(Switching of motor drive control)
Next, in the control device 1 having the above-described configuration, the selection of the drive control of the motor 2 will be described with reference to FIG. FIG. 3 is a flow showing selection of drive control of the motor 2 by the control device 1.

When the flow shown in FIG. 3 starts (START), first, in step S1, the control switching unit 22 of the control device 1 calculates the voltage utilization rate. The voltage utilization rate is based on the q-axis voltage Vq and d-axis voltage Vd obtained from the q-axis current command Iq_ref and the d-axis current command Id_ref, and the input DC voltage of the main circuit 50, and the above equations (3) and equations (3) and equations. It is obtained by using (4).

Next, in step S2, the control switching unit 22 determines whether or not the obtained voltage utilization rate is 0.78. When the voltage utilization rate is 0.78 (YES), the control switching unit 22 drives and controls the motor 2 by the rectangular wave drive control. That is, the control switching unit 22 outputs the q-axis voltage command Vq_ref and the d-axis voltage command Vd_ref to the rectangular wave signal generation unit 24.

On the other hand, when the voltage utilization rate is smaller than 0.78 (NO), the control switching unit 22 drives and controls the motor 2 by PWM drive control. That is, the control switching unit 22 outputs the q-axis voltage command Vq_ref and the d-axis voltage command Vd_ref to the PWM signal generation unit 23.

Thereby, the drive control of the motor 2 can be switched to the rectangular wave drive control or the PWM drive control according to the voltage utilization rate.

In the present embodiment, when the voltage utilization rate is smaller than 0.78, the control switching unit 22 inputs the voltage commands Vq_ref and Vd_ref to the PWM signal generation unit 23, while the voltage utilization rate is 0.78. Occasionally, voltage commands Vq_ref and Vd_ref are input to the square wave signal generation unit 24.

Thereby, while controlling the drive of the motor 2 with the current commands Iq_ref and Id_ref, the drive control of the motor 2 can be smoothly switched between the PWM drive control and the rectangular wave drive control according to the voltage utilization rate.

(Other embodiments)
Although the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the embodiment is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented within a range that does not deviate from the gist thereof.

In the above embodiment, the voltage conversion unit 15 obtains the q-axis voltage Vq and the d-axis voltage Vd from the q-axis current command Iq_ref and the d-axis current command Id_ref. Is used to calculate the effective line voltage value.

However, the voltage conversion unit obtains the q-axis voltage Vq and the d-axis voltage Vd from the q-axis current feedback value Iq_fb and the d-axis current feedback value Id_f output from the three-phase two-phase conversion unit 60, and the line voltage is effective. The value calculation unit may calculate the line voltage effective value by the equation (3).

Further, the line voltage calculation unit may calculate the line voltage effective value by the equation (3) using the measured value of the line voltage of the motor 2. In this case, the voltage conversion unit as in the above embodiment is unnecessary.

In the above embodiment, the configuration of the control device 1 that controls the drive of the motor 2 that is a three-phase AC motor has been described, but the present invention is not limited to this, and the control device that controls the drive of a multi-phase AC motor other than the three-phase AC motor It may be applied. That is, the motor may have any configuration as long as it is a synchronous motor.

The present invention can be used in a control device capable of switching the drive control of a synchronous electric motor between PWM drive control and rectangular wave drive control.

1 Control device 2 Motor (synchronous motor)
10 Current command generation unit 11 d-axis current command generation unit 11a d-axis current command conversion unit 11b Addition unit 12 q-axis current command generation unit 13 Weak field control unit 15 Voltage conversion unit 16 Line voltage effective value calculation unit 17 Voltage utilization rate calculation Unit 18 Voltage utilization comparison unit 19 PI calculation unit 20 Current control unit 21 Voltage command generation unit 21a q-axis current feedback unit 21b q-axis current PI calculation unit 21c d-axis current feedback unit 21d d-axis current PI calculation unit 22 Control switching unit 23 PWM signal generation unit 23a Two-phase three-phase conversion unit 23b Triangular wave comparison unit 24 Rectangular wave signal generation unit 24a Voltage phase generation unit 24b Interruption processing unit 30 Judgment unit 50 Main circuit (drive control unit)
60 Three-phase two-phase converter 70 Current sensor 80 Position sensor T_ref Torque command value Id_ref d-axis current command Id_ref0 d-axis current command correction value Id_ref1 d-axis current command initial value Id_fb d-axis current feedback value Iq_ref q-axis current command Iq_fb q-axis Current feedback value Iu_fb U-phase current feedback value Iw_fb W-phase current feedback value Vd d-axis voltage Vq q-axis voltage Vq_ref q-axis voltage command Vd_ref d-axis voltage command

Claims (3)

A control device for a synchronous motor that controls the drive of the synchronous motor.
A current command generator that generates a current command from a torque command,
A voltage command generator that generates a voltage command based on the current command,
A PWM signal generator that generates a PWM signal based on the voltage command,
A square wave signal generator that generates a square wave signal based on the voltage command,
A control switching unit that inputs the voltage command to one of the PWM signal generation unit and the rectangular wave signal generation unit according to the voltage utilization rate.
A drive control unit that controls the drive of the synchronous motor by using the signal generated by the PWM signal generation unit or the rectangular wave signal generation unit.
With
When the voltage utilization rate of the current command generator is equal between the case where the synchronous motor is driven by the PWM signal with the minimum current and the case where the synchronous motor is driven by the rectangular wave signal. The current command is generated so as not to exceed the predetermined voltage utilization rate of.
When the voltage utilization rate is smaller than the predetermined voltage utilization rate, the control switching unit inputs the voltage command to the PWM signal generation unit, while the voltage utilization rate is the predetermined voltage utilization rate. In this case, a control device for a synchronous electric motor that inputs the voltage command to the square wave signal generation unit. In the control device for the synchronous motor according to claim 1.
The current command includes a d-axis current command.
The current command generator
When the voltage utilization rate is larger than the predetermined voltage utilization rate, the d-axis current command correction value for correcting the d-axis current command is obtained so that the voltage utilization rate becomes the predetermined voltage utilization rate. A control device for a synchronous motor having a field control unit. In the control device for the synchronous motor according to claim 1 or 2.
The voltage utilization rate when a current equal to that of the synchronous motor flows between the case where the synchronous motor is driven by the PWM signal with the minimum current and the case where the synchronous motor is driven by the rectangular wave signal is 0.78. Synchronous motor control device.

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