JP5418416B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device including an inverter and a smoothing capacitor connected to a DC power source, and an AC motor driven by the inverter.

  2. Description of the Related Art In recent years, electric vehicles and hybrid vehicles equipped with an AC motor as a power source for vehicles have attracted attention due to social demands for low fuel consumption and low exhaust emissions. In such an electric vehicle or a hybrid vehicle, an inverter connected to a DC power source composed of a secondary battery or the like converts a DC voltage into an AC voltage to drive an AC motor, and a smoothing capacitor connected to the DC power source. Some have smoothed the voltage of the power line.

  In such a motor control system, for example, as described in Patent Document 1 (Japanese Patent No. 3289567), when the relay is opened (turned off) and the DC power supply is disconnected from the inverter and the smoothing capacitor. When performing discharge control for discharging the charge stored in the smoothing capacitor, the d-axis current command (excitation current command) of the AC motor is set to non-zero and the deviation between the d-axis current command and the d-axis current detection value The d-axis current feedback control for setting the d-axis voltage command value based on the q-axis current command is executed, and the q-axis current command (torque current command) is set to zero and the deviation between the q-axis current command and the q-axis current detection value is set. Q-axis current feedback control is performed to set the q-axis voltage command value based on the d-axis voltage command value, and the inverter is controlled based on these d-axis voltage command value and q-axis voltage command value. By controlling the energization of the motor, the AC motor's torque is controlled to zero while discharging the smoothing capacitor by consuming electrical energy (converted to Joule heat) in the winding of the AC motor. is there.

Japanese Patent No. 3289567

  In the technique of the above-mentioned patent document 1, when discharging the electric charge stored in the smoothing capacitor, both the d-axis current and the q-axis current of the AC motor are feedback controlled, so that the calculation load of the control circuit is increased. There are drawbacks. Further, the d-axis current command may be set to a negative value, and if the d-axis current command is set to a negative value, the following problem may occur.

  As shown in FIG. 5B, the equal torque curve (curve representing the current that generates the same torque) of the AC motor has a characteristic that the interval in the q-axis direction becomes narrower as the d-axis moves in the negative direction. When the d-axis current command is set to a negative value, the torque sensitivity in the q-axis direction increases, and the torque generated when the current vector fluctuates in the q-axis direction increases. For this reason, there is a possibility that the AC motor will rotate due to torque due to fluctuations in the current vector. When the AC motor rotates, the teeth of the gear mechanism of the power transmission system collide with the teeth depending on how the motor rotates. There is a possibility that problems such as noise and vehicle movement may occur.

  Therefore, the problem to be solved by the present invention is to suppress the rotation of the AC motor while reducing the calculation load of the control circuit when the electric energy is consumed by the AC motor and the electric charge of the smoothing capacitor is discharged. An object of the present invention is to provide a motor control device that can be used.

  In order to solve the above-described problem, an invention according to claim 1 is directed to a motor control device including an inverter and a smoothing capacitor connected to a DC power source, and an AC motor driven by the inverter. When discharging the electric charge stored in the smoothing capacitor while being disconnected from the capacitor, the d-axis voltage command value is set to a positive value so that a d-axis current that does not contribute to torque generation of the AC motor flows. The q-axis voltage command is set so that the q-axis current command value is set to 0 so that the q-axis current that contributes to the torque generation of the motor does not flow and the deviation between the q-axis current command value and the q-axis current detection value becomes small. Discharge motor that executes q-axis current feedback control to set a value and controls the inverter based on the d-axis voltage command value and the q-axis voltage command value to control energization of the AC motor In which was configured to include a control means.

  In this configuration, when discharging the electric charge stored in the smoothing capacitor, the d-axis voltage command value of the AC motor is set to a positive value, the q-axis current command value is set to 0, and the q-axis current command is set. Q-axis current feedback control is performed to set the q-axis voltage command value so that the deviation between the value and the q-axis current detection value is small, and the inverter is controlled based on the d-axis voltage command value and the q-axis voltage command value. By controlling the energization of the AC motor, it is possible to control the torque of the AC motor to almost zero while consuming electric energy (converting to Joule heat) by the winding of the AC motor and discharging the charge of the smoothing capacitor. it can.

  In this case, since the d-axis current is not feedback-controlled but only the q-axis current is feedback-controlled, the calculation load of the control circuit can be reduced. Further, as shown in FIG. 5A, the equal torque curve of the AC motor (curve representing the current that generates the same torque) has a characteristic that the interval in the q-axis direction becomes narrower as the d-axis moves in the negative direction. However, in the present invention, since the d-axis voltage command value is set to a positive value, the torque sensitivity in the q-axis direction can be lowered as compared with the case where the d-axis voltage command value is set to a negative value. The torque generated when the current vector fluctuates in the q-axis direction can be reduced. For this reason, it is possible to suppress the rotation of the AC motor due to the torque due to the fluctuation of the current vector, and the trouble due to the rotation of the AC motor (the teeth of the gear mechanism of the power transmission system collide with the teeth and an annoying rattling sound is generated. Can be prevented).

  In this case, the d-axis voltage command value may be set based on the capacitance of the smoothing capacitor, the winding resistance of the AC motor, and a predetermined required discharge time. In this way, the d-axis voltage command value (for example, initial value) can be set so that the discharge of the smoothing capacitor can be completed within the required discharge time.

  Further, as described in claim 3, the d-axis voltage command value may be changed so that the modulation rate (duty ratio) when the inverter is controlled by the PWM control method is constant. In this way, as the smoothing capacitor discharges, the residual charge of the smoothing capacitor decreases and the input voltage of the inverter (the voltage across the smoothing capacitor) decreases. The d-axis voltage command value can be set to an appropriate value that corresponds to the input voltage of the inverter (the voltage across the smoothing capacitor), reducing variations in the discharge time of the smoothing capacitor (the time required to complete the discharge). can do.

  By the way, the smaller the modulation rate when controlling the inverter by the PWM control method, the greater the influence of the inverter dead time (the time during which both the upper arm and lower arm switching elements are turned off). For this reason, in a region where the input voltage of the inverter is low, if the modulation rate is too small, the output voltage of the inverter (applied voltage of the AC motor) is excessively reduced due to the dead time, and the discharge time of the smoothing capacitor becomes long. there is a possibility.

  Therefore, as in claim 4, in the region where the input voltage of the inverter is equal to or higher than the predetermined voltage, the d-axis voltage command value is changed so that the modulation factor when the inverter is controlled by the PWM control method becomes the first predetermined value. Then, the d-axis voltage command value may be changed so that the modulation factor becomes a second predetermined value larger than the first predetermined value in a region where the input voltage of the inverter is lower than the predetermined voltage. In this way, in the region where the input voltage of the inverter is lower than the predetermined voltage, it is possible to moderately increase the modulation factor to reduce the influence of the inverter dead time, and the inverter output voltage (applied voltage of the AC motor). ) Is prevented from excessively decreasing, and the discharge time of the smoothing capacitor can be prevented from becoming long.

FIG. 1 is a diagram showing a schematic configuration of an entire drive system of a hybrid vehicle in one embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of an AC motor control system. FIG. 3 is a block diagram illustrating motor control during normal operation. FIG. 4 is a block diagram illustrating motor control during discharging. FIG. 5A is a diagram for explaining the torque sensitivity of the motor control at the time of discharge in this embodiment, and FIG. 5B is a diagram for explaining the torque sensitivity of the motor control at the time of discharge of the comparative example. FIG. 6 is a flowchart for explaining the processing flow of the motor control routine during discharging. FIG. 7 is a time chart for explaining an execution example of motor control during discharging.

Hereinafter, an embodiment in which a mode for carrying out the present invention is applied to a hybrid vehicle will be described.
First, the overall configuration of the hybrid vehicle drive system will be described with reference to FIG.

  An engine 11 that is an internal combustion engine and an AC motor 12 are mounted as power sources for the vehicle. The power of the output shaft (crankshaft) of the engine 11 is transmitted to the transmission 13 via the AC motor 12 and the clutch 17, and the power of the output shaft of the transmission 13 is transmitted to the wheels via the differential gear mechanism 14, the axle 15 and the like. 16 is transmitted. The transmission 13 may be, for example, a torque converter, a transmission mechanism, and the like, and may be a stepped transmission that switches a gear step among a plurality of gear steps, or a CVT that changes continuously (nothing). A step transmission).

  Further, the rotation shaft of the AC motor 12 is connected between the engine 11 and the transmission 13 in the power transmission path for transmitting the power of the engine 11 to the wheels 16 so that the power can be transmitted. Between the machine 13 (or between the engine 11 and the AC motor 12), a clutch 17 for interrupting power transmission is provided. The clutch 13 may be a hydraulically driven hydraulic clutch or an electromagnetically driven electromagnetic clutch. In addition, an inverter 18 that drives the AC motor 12 is connected to a battery 19, and the AC motor 12 exchanges electric power with the battery 19 via the inverter 18.

  The hybrid ECU 20 is a computer that comprehensively controls the entire hybrid vehicle, and detects an accelerator sensor 21 that detects an accelerator opening (amount of operation of an accelerator pedal), a shift switch 22 that detects an operation position of a shift lever, and a brake operation. The driving signal of the vehicle is detected by reading the output signals of various sensors and switches such as the brake switch 23 and the vehicle speed sensor 24 for detecting the vehicle speed. The hybrid ECU 20 includes an engine ECU 25 that controls the operation of the engine 11, an MG-ECU 26 that controls the inverter 18 to control the operation of the AC motor 12, and a transmission ECU 27 that controls the transmission 13 and the clutch 17. A control signal, a data signal, etc. are transmitted / received, and each engine 25-27 controls the engine 11, the AC motor 12, the transmission 13, and the clutch 17 according to the driving | running state of a vehicle.

Next, a schematic configuration of the control system for the AC motor 12 will be described with reference to FIG.
A booster converter 30 (DC-DC converter) is connected to the battery 19, which is a DC power source composed of a secondary battery or the like, via relays 28 and 29. The booster converter 30 boosts the DC voltage of the battery 19. A function of generating a DC system voltage between the system power supply line 31 and the earth line 32 or returning the power to the battery 19 by reducing the system voltage is provided. Note that the boost converter 30 may be omitted. A smoothing capacitor 33 that smoothes the system voltage and a voltage-controlled three-phase inverter 18 are connected between the system power supply line 31 and the earth line 32, and the AC motor 12 is driven by the inverter 18. A configuration in which the smoothing capacitor 33 is incorporated in the inverter 18 may be adopted.

  The AC motor 12 is, for example, a three-phase permanent magnet type synchronous motor, in which a permanent magnet is built, and a rotor rotational position sensor 34 that detects the rotational position θ (rotational angle) of the rotor is mounted. The voltage-controlled three-phase inverter 18 includes six switching elements 35 to 40 (three switching elements 35, 37, and 39 for each phase of the upper arm and three switching elements 36 and 38 for each phase of the lower arm). , 40), and free-wheeling diodes 41 to 46 are connected in parallel to the switching elements 35 to 40, respectively.

  The inverter 18 is connected to the DC voltage (boosted by the boost converter 30) of the system power line 31 based on the three-phase six-arm voltage command signals UU, UL, VU, VL, WU, WL output from the MG-ECU 26. System voltage) is converted into three-phase AC voltages U, V, and W to drive AC motor 12. A U-phase current iu flowing in the U-phase of AC motor 12 is detected by U-phase current sensor 47, and a W-phase current iw flowing in the W-phase of AC motor 12 is detected by W-phase current sensor 48.

  The MG-ECU 26 controls the boost converter 30 so that the system voltage becomes the target voltage during normal operation of the vehicle, and controls the inverter 18 so that the output torque of the AC motor 12 becomes the target torque (torque command value). Torque control for adjusting the AC voltage applied to the AC motor 12 is executed. In this torque control, the torque command value output from the hybrid ECU 20, the U-phase current iu and the W-phase current iw of the AC motor 12 (output signals of the current sensors 47 and 48), and the rotor rotational position θ ( Based on the output signal of the rotor rotational position sensor 34), for example, a three-phase voltage command signal is generated by a sine wave PWM control method or a rectangular wave control method, and is output to the inverter 18.

  Specifically, as shown in FIG. 3, in the dq coordinate system set as the rotor rotation coordinate of the AC motor 12, in order to independently perform feedback control of the d-axis current id and the q-axis current iq, an AC Based on the torque command value and the rotational speed of the motor 12, the command current vector (d-axis current command value Id, q-axis current command value Iq) is calculated using a map or a mathematical expression.

  Further, based on the U-phase current iu and the W-phase current iw of the AC motor 12 (output signals of the current sensors 47 and 48) and the rotor rotational position θ of the AC motor 12 (the output signal of the rotor rotational position sensor 34), A detection current vector (d-axis current detection value id, q-axis current detection value iq), which is a detection value of the current flowing through AC motor 12, is calculated.

  Thereafter, the d-axis voltage command value Vd is calculated by PI control or the like so that the deviation Δid between the d-axis current command value Id and the detected d-axis current value id becomes small, and the q-axis current command value Iq and the q-axis current are calculated. The q-axis voltage command value Vq is calculated by PI control or the like so that the deviation Δiq from the detected value iq is small, and a command voltage vector (d-axis voltage command value Vd, q-axis voltage command value Vq) is obtained.

  Based on this command voltage vector (d-axis voltage command value Vd, q-axis voltage command value Vq) and rotor rotation position θ of AC motor 12 (output signal of rotor rotation position sensor 34), three-phase voltage command value Vu. , Vv, Vw are calculated, and these three-phase voltage command values Vu, Vv, Vw are converted into three-phase six-arm voltage command signals UU, UL, VU by, for example, a sine wave PWM control method or a rectangular wave control method. , VL, WU, WL, and these three-phase 6-arm voltage command signals UU, UL, VU, VL, WU, WL are output to the inverter 18.

  Further, the MG-ECU 26 executes a discharge motor control routine shown in FIG. 6 to be described later, so that, for example, the relays 28 and 29 are opened (turned off) when an ignition switch (not shown) is turned off, and the battery 19 is connected to the inverter 19. 18 and the smoothing capacitor 33 are electrically disconnected from the smoothing capacitor 33, and when a discharge request for the smoothing capacitor 33 is generated, electric energy is consumed (converted to Joule heat) by the winding of the AC motor 12 and stored in the smoothing capacitor 33. The discharge control for discharging the charged charges is executed. At this time, when the AC motor 12 rotates, depending on how the AC motor 12 rotates, the teeth of the gear mechanism of the power transmission system (for example, the transmission 13 and the like) collide with each other to generate an annoying rattling sound or the vehicle moves. Such a problem may occur.

  As a countermeasure against this, the MG-ECU 26 causes the d-axis voltage command to flow a d-axis current that does not contribute to the torque generation of the AC motor 12 as shown in FIG. Set the value Vd to a positive value. The q-axis current command value Iq is set to 0 so that no q-axis current contributing to torque generation of the AC motor 12 flows, and the U-phase current iu and W-phase current iw of the AC motor 12 (current sensors 47, 48) and the rotor rotational position θ of the AC motor 12 (the output signal of the rotor rotational position sensor 34), the q-axis current detection value iq is calculated, and the q-axis current command value Iq and the q-axis current are calculated. The q-axis current feedback control is executed to set the q-axis voltage command value Vq by PI control or the like so that the deviation Δiq from the detected value iq becomes small.

  Thereafter, based on the command voltage vector (d-axis voltage command value Vd, q-axis voltage command value Vq) and the rotor rotation position θ of AC motor 12 (output signal of rotor rotation position sensor 34), a three-phase voltage command is generated. After calculating the values Vu, Vv, Vw, these three-phase voltage command values Vu, Vv, Vw are converted into three-phase six-arm voltage command signals UU, UL by, for example, a sine wave PWM control method or a rectangular wave control method. , VU, VL, WU, WL, and these three-phase 6-arm voltage command signals UU, UL, VU, VL, WU, WL are output to the inverter 18 to control the energization of the AC motor 12. Thus, the torque of the AC motor 12 is controlled to be substantially zero while the electric energy is consumed (converted to Joule heat) by the winding of the AC motor 12 and the electric charge stored in the smoothing capacitor 33 is discharged.

  Further, as shown in FIG. 5A, the isotorque curve of AC motor 12 (curve representing the current that generates the same torque) has a characteristic that the interval in the q-axis direction becomes narrower as the d-axis moves in the negative direction. However, in this embodiment, since the d-axis voltage command value is set to a positive value, the torque sensitivity in the q-axis direction is made lower than when the d-axis voltage command value is set to a negative value. The torque generated when the current vector fluctuates in the q-axis direction can be reduced. For this reason, it is possible to suppress the rotation of the AC motor 12 due to the torque due to the fluctuation of the current vector.

Hereinafter, the processing content of the motor control routine at the time of discharging shown in FIG. 6 executed by the MG-ECU 26 will be described.
The discharge motor control routine shown in FIG. 6 is repeatedly executed at a predetermined cycle while the MG-ECU 26 is powered on, and serves as a discharge motor control means in the claims. When this routine is started, first, at step 101, it is determined whether or not a discharge request for the smoothing capacitor 33 has occurred. For example, the relays 28 and 29 are opened (off) by turning off an ignition switch (not shown). Whether or not the battery 19 is electrically disconnected from the inverter 18 and the smoothing capacitor 33 is determined.

  If it is determined in step 101 that a discharge request for the smoothing capacitor 33 has not occurred, this routine is terminated without executing the processing related to the discharge control in step 102 and subsequent steps.

  On the other hand, if it is determined in step 101 that a discharge request for the smoothing capacitor 33 has occurred, the process related to the discharge control after step 102 is performed as follows at that time t1 (see FIG. 7). Run. First, in step 102, the input voltage Vdc of the inverter 18 (voltage across the smoothing capacitor 33) detected by a voltage sensor (not shown) is acquired, and then the process proceeds to step 103, where the input voltage Vdc of the inverter 18 is a predetermined determination. It is determined whether the value is higher than V1. Here, the determination value V1 is set to, for example, the voltage across the smoothing capacitor 33 when the discharge of the smoothing capacitor 33 is almost completed or in the vicinity thereof.

  If it is determined in step 103 that the input voltage Vdc of the inverter 18 is higher than the determination value V1, the charge stored in the smoothing capacitor 33 needs to be discharged (discharge control needs to be executed). And the processing after step 104 is executed as follows.

  First, after setting the q-axis current command value Iq to 0 in step 104, the process proceeds to step 105, where the U-phase current iu and the W-phase current iw (output signals of the current sensors 47 and 48) of the AC motor 12 and the AC Based on the rotor rotational position θ of the motor 12 (output signal of the rotor rotational position sensor 34), a q-axis current detection value iq is calculated.

  Thereafter, the process proceeds to step 106, and after calculating a deviation Δiq (= Iq−iq) between the q-axis current command value Iq and the q-axis current detection value iq, the process proceeds to step 107, and the q-axis current command value Iq and the q-axis The q-axis current feedback control is executed to calculate the q-axis voltage command value Vq by PI control or the like so that the deviation Δiq from the detected current value iq is small.

  Thereafter, the process proceeds to step 108, and the d-axis voltage command value Vd is set to a positive value. In this case, the first time after the discharge request is generated, the discharge of the smoothing capacitor 33 is completed within the required discharge time based on the capacitance of the smoothing capacitor 33, the winding resistance of the AC motor 12, and the predetermined required discharge time. An initial value (see FIG. 7) of the d-axis voltage command value Vd is set so that it can be performed. As the initial value of the d-axis voltage command value Vd, a value calculated in advance based on test data, design data, or the like may be stored in the ROM of the MG-ECU 26 (or the hybrid ECU 20 or the like). The initial value of the d-axis voltage command value Vd may be corrected according to the input voltage Vdc of the inverter 18 (the voltage across the smoothing capacitor 33).

  In the second and subsequent times after the occurrence of the discharge request, the d-axis voltage command value Vd is set so that the modulation factor (= Vd / Vdc) when the inverter 18 is controlled by the PWM control method is constant (or substantially constant). Change. As a result, as shown in FIG. 7, as the smoothing capacitor 33 is discharged, the residual charge of the smoothing capacitor 33 is reduced, and the input voltage Vdc (the voltage across the smoothing capacitor 33) of the inverter 18 is reduced. Then, the d-axis voltage command value Vd is lowered.

  Thereafter, the process proceeds to step 109, based on the command voltage vector (d-axis voltage command value Vd, q-axis voltage command value Vq) and the rotor rotational position θ (output signal of the rotor rotational position sensor 34) of the AC motor 12. After calculating the three-phase voltage command values Vu, Vv, Vw, these three-phase voltage command values Vu, Vv, Vw are converted into three-phase six-arm voltage command signals UU, UL, VU, By converting these three-phase 6-arm voltage command signals UU, UL, VU, VL, WU, WL to the inverter 18 and controlling the energization of the AC motor 12, The electric motor consumes electric energy (converted into Joule heat) by the windings of the motor 12 and discharges the electric charge stored in the smoothing capacitor 33, while controlling the torque of the AC motor 12 to be substantially zero.

  Thereafter, if it is determined in step 102 that the input voltage Vdc of the inverter 18 is equal to or less than the determination value V1, it is determined that the discharge of the smoothing capacitor 33 is completed at that time t2 (see FIG. 7). By ending this routine without executing the processing after step 103, the discharge control is ended and the discharge request is turned off.

  In the present embodiment described above, when discharging the electric charge stored in the smoothing capacitor 33, the d-axis voltage command value Vd of the AC motor 12 is set to a positive value, and the q-axis current command value Iq is set to 0. The q-axis current feedback control is performed to set the q-axis voltage command value Vq so that the deviation Δiq between the q-axis current command value Iq and the q-axis current detection value iq becomes small, and the d-axis voltage command value Vd Since the inverter 18 is controlled on the basis of the q-axis voltage command value Vq and the energization of the AC motor 12 is controlled, electric energy is consumed (converted to Joule heat) by the winding of the AC motor 12, and a smoothing capacitor is obtained. The torque of the AC motor 12 can be controlled to almost zero while discharging the electric charge 33.

  In this case, since the d-axis current is not feedback-controlled and only the q-axis current is feedback-controlled, the calculation load on the MG-ECU 26 (control circuit) can be reduced. Further, since the d-axis voltage command value Vd is set to a positive value, the torque sensitivity in the q-axis direction can be lowered compared to the case where the d-axis voltage command value Vd is set to a negative value, and the current vector The torque generated when the fluctuates in the q-axis direction can be reduced. For this reason, it is possible to suppress the rotation of the AC motor 12 due to the torque due to the fluctuation of the current vector, and the trouble due to the rotation of the AC motor 12 (the teeth of the gear mechanism of the power transmission system collide with the teeth and the annoying rattling. It is possible to prevent problems such as generation of sound and vehicle movement.

  In this embodiment, the initial value of the d-axis voltage command value Vd is set based on the capacitance of the smoothing capacitor 33, the winding resistance of the AC motor 12, and the predetermined required discharge time. The initial value of the d-axis voltage command value Vd can be set so that the discharge of the smoothing capacitor 33 can be completed within the discharge time.

  Furthermore, in this embodiment, since the d-axis voltage command value Vd is changed so that the modulation rate (duty ratio) when the inverter 18 is controlled by the PWM control method is constant, the smoothing capacitor 33 is discharged. Along with this, the remaining charge of the smoothing capacitor 33 decreases and the input voltage Vdc (the voltage across the smoothing capacitor 33) of the inverter 18 decreases. The voltage command value Vd can be set to an appropriate value corresponding to the input voltage Vdc of the inverter 18 (the voltage across the smoothing capacitor 33), and variations in the discharge time (time required to complete the discharge) of the smoothing capacitor 33 are reduced. be able to.

  By the way, the smaller the modulation factor when controlling the inverter 18 by the PWM control method, the greater the influence of the dead time of the inverter 18 (the time during which both the upper arm and lower arm switching elements are turned off). For this reason, in a region where the input voltage Vdc of the inverter 18 is low, if the modulation factor is too small, the output voltage of the inverter 18 (the applied voltage of the AC motor 12) is excessively lowered due to the dead time, and the smoothing capacitor 33 The discharge time can be long.

  Therefore, in the region where the input voltage Vdc of the inverter 18 is equal to or higher than the predetermined voltage (region where the influence of the dead time is small), the d-axis voltage command value Vd is changed so that the modulation factor becomes the first predetermined value. In a region where the input voltage Vdc is lower than the predetermined voltage (region where the influence of dead time is large), the d-axis voltage command value Vd is changed so that the modulation factor becomes a second predetermined value larger than the first predetermined value. You may do it. In this way, in the region where the input voltage Vdc of the inverter 18 is lower than the predetermined voltage, the modulation factor can be increased moderately to reduce the influence of the dead time of the inverter 18, and the output voltage (AC) of the inverter 18 can be reduced. It can be avoided that the applied voltage of the motor 12 is excessively lowered, and the discharge time of the smoothing capacitor 33 is prevented from becoming long.

In the region where the input voltage Vdc of the inverter 18 is lower than the predetermined voltage, the d-axis voltage command value Vd may be changed so that the modulation rate gradually increases.
In the above embodiment, the d-axis voltage command value Vd is changed. However, the present invention is not limited to this, and the d-axis voltage command value Vd may be maintained at a constant value.

  In the above embodiment, the present invention is applied to the hybrid vehicle motor control system using both the engine and the AC motor as the power source. However, the present invention is not limited to this, and the motor of the electric vehicle using only the AC motor as the power source. The present invention may be applied to a control system. Furthermore, the present invention may be applied to motor control systems other than electric vehicles and hybrid vehicles.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... AC motor, 18 ... Inverter, 19 ... Battery (DC power supply), 20 ... Hybrid ECU, 25 ... Engine ECU, 26 ... MG-ECU (motor control means during discharge), 27 ... Transmission ECU 33 ... Smoothing capacitor 34 ... Rotor rotational position sensor 47, 48 ... Current sensor

Claims (4)

In a motor control device comprising an inverter and a smoothing capacitor connected to a DC power source, and an AC motor driven by the inverter,
When discharging the electric charge stored in the smoothing capacitor in a state where the DC power source is disconnected from the inverter and the smoothing capacitor, a d-axis voltage command is used to flow a d-axis current that does not contribute to torque generation of the AC motor. The q-axis current command value and the q-axis current detection value are set to 0 so that the q-axis current command value is set to 0 so that the q-axis current contributing to the torque generation of the AC motor does not flow. Q-axis current feedback control is performed to set a q-axis voltage command value so that a deviation from the AC motor becomes small, and the inverter is controlled based on the d-axis voltage command value and the q-axis voltage command value, thereby A motor control apparatus comprising: a motor controller for discharging that controls energization of the motor.   2. The discharge motor control means sets the d-axis voltage command value based on a capacitance of the smoothing capacitor, a winding resistance of the AC motor, and a predetermined required discharge time. The motor control device described in 1.   3. The discharge motor control means includes means for changing the d-axis voltage command value so that a modulation rate when the inverter is controlled by a PWM control method is constant. The motor control apparatus described.   The discharging motor control means sets the d-axis voltage command value so that a modulation factor when controlling the inverter by a PWM control method is a first predetermined value in a region where the input voltage of the inverter is equal to or higher than a predetermined voltage. And a means for changing the d-axis voltage command value so that the modulation rate becomes a second predetermined value larger than the first predetermined value in a region where the input voltage of the inverter is lower than the predetermined voltage. The motor control device according to claim 1, wherein the motor control device is a motor control device.

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