Drive unit

Abstract

This suppresses instability in motor control while also preventing the surge voltage applied to the motor from becoming relatively large. [Solution] The drive device comprises a motor, an inverter that drives the motor, and a control device that sets three-phase voltage commands based on the motor's torque command, generates a three-phase PWM signal by comparing the three-phase voltage command-related values ​​associated with the three-phase voltage commands with a triangular wave, and controls the inverter. In this case, when the difference between the voltage command-related values ​​of two of the three-phase voltage command-related values ​​is less than or equal to a predetermined difference, the control device corrects the voltage command-related values ​​so that the later of the cross timings between the two-phase voltage command-related values ​​and the triangular wave becomes even later.

Description

Technical Field

[0001] The present disclosure relates to a drive device.

Background Art

[0002] Conventionally, a drive device including a motor and an inverter that drives the motor by switching a plurality of switching elements has been proposed (see, for example, Patent Document 1). In this drive device, an anti-simultaneous switching circuit is inserted between a three-phase PWM signal generation circuit that generates three-phase control signals (PWM signals) and a plurality of gate drive circuits for driving the plurality of switching elements respectively. The anti-simultaneous switching circuit includes a plurality of input means that take in the three-phase control signals from the three-phase PWM signal generation circuit as input signals, masking pulse generation means that generates masking pulses for masking the rising edges of the input signals of the other phases during a predetermined period in synchronization with the rising edge of one-phase input signal, masking signal formation means that outputs a masking signal having a pulse width formed by the logical sum of the plurality of masking pulses from the masking pulse generation means of the other phases as a masking period, signal masking means that receives one-phase input signal and outputs a signal whose rising edge is delayed until the end of the masking period of the output signal from the masking signal formation means, and a plurality of output means that output the output signal from the signal masking means to the outside.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the aforementioned drive system, the simultaneous switching prevention circuit suppresses simultaneous switching of multiple phases, thereby preventing the surge voltage applied to the motor from becoming relatively large. However, because it does not switch multiple switching elements according to the three-phase control signal from the three-phase PWM signal generation circuit, there is a possibility that the motor control may become unstable.

[0005] The primary objective of the drive device of this disclosure is to suppress the surge voltage applied to the motor while suppressing instability in motor control. [Means for solving the problem]

[0006] The drive device of this disclosure employs the following means to achieve the main objective described above.

[0007] [1] The drive device of the present disclosure is A drive device comprising: a motor; an inverter for driving the motor; and a control device that sets three-phase voltage commands based on the torque command of the motor, generates three-phase PWM signals by comparing the three-phase voltage command-related values ​​associated with the three-phase voltage commands with a triangular wave, and controls the inverter, The control device corrects the voltage command-related values ​​so that the later of the crossover timings between the two phases of the voltage command-related values ​​and the triangular wave becomes even later when the difference between the voltage command-related values ​​of two of the three phases is less than or equal to a predetermined difference. This is the gist of it.

[0008] In the drive device of this disclosure, the control device sets three-phase voltage commands based on the torque command of a phase AC motor, and controls the inverter by generating a three-phase PWM signal by comparing the three-phase voltage command-related values ​​associated with the three-phase voltage commands with a triangular wave. In this case, when the difference between the voltage command-related values ​​of two of the three-phase voltage command-related values ​​is less than or equal to a predetermined difference, the control device corrects the voltage command-related values ​​so that the later of the crossover timings between the two-phase voltage command-related values ​​and the triangular wave becomes even later. Therefore, since the inverter is controlled by correcting the voltage command-related values ​​as described above without providing a simultaneous switching prevention circuit, it is possible to suppress the motor control from becoming unstable while suppressing the surge voltage applied to the motor from becoming relatively large.

[0009] [2] In the drive device of the present disclosure (the drive device described in [1] above), the control device may set the voltage command related values ​​of the three phases from the timing of the next peak of the triangular wave onward at the timing of the trough of the triangular wave, and if the difference is less than or equal to the predetermined difference, the voltage command related values ​​may be corrected so that the cross timing of the two phases whose cross timing with the descending triangular wave is later becomes even later.

[0010] [3] In the drive device of the present disclosure (the drive device described in [1] or [2] above), the control device may set the voltage command related values ​​of the three phases from the timing of the next trough of the triangular wave onward at the timing of the peak of the triangular wave, and if the difference is less than or equal to the predetermined difference, the voltage command related values ​​may be corrected so that the cross timing of the two phases whose cross timing with the rising triangular wave is later becomes even later.

[0011] [4] In a drive device of the present disclosure (a drive device described in any one of [1] to [3] above), the control device sets the three-phase duty cycle commands based on the three-phase voltage commands, generates the three-phase PWM signals by comparing the three-phase duty cycle commands with the triangular wave, and the control device may correct the voltage commands so that the later of the two-phase duty cycle commands and the triangular wave cross timings becomes even later when the difference between the two-phase voltage commands is less than or equal to the predetermined difference. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of an electric vehicle 10 equipped with the drive unit of the embodiment. [Figure 2] This is a block diagram showing an example of a control function block for inverter 24. [Figure 3] This is a flowchart showing an example of a processing routine. [Figure 4] This is an explanatory diagram illustrating an example of the relationship between duty cycles Du*, Dv* and triangular waves and PWM signals Su*, Sv*. [Modes for carrying out the invention]

[0013] Embodiments for implementing this disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram of an electric vehicle 10 equipped with a drive unit according to an embodiment of this disclosure. As shown in the figure, the electric vehicle 10 of the embodiment comprises a motor 22, an inverter 24, a battery 26, and an electronic control unit (hereinafter referred to as "ECU") 50.

[0014] The motor 22 is configured as a three-phase AC motor and has a rotor with permanent magnets embedded in the rotor core and a stator with three-phase (U-phase, V-phase, W-phase) coils wound around the stator core. The rotor of the motor 22 is connected to a drive shaft 16 which is connected to the drive wheels 12a and 12b via a differential gear 14.

[0015] The inverter 24 is connected to the power line 28 (positive line 28p and negative line 28n) to which the battery 26 is connected. The inverter 24 comprises six switching elements, transistors T11 to T16, and six diodes D11 to D16, each connected in parallel to the six transistors T11 to T16. The transistors T11 to T16 are arranged in pairs, with two on each side acting as the source and sink sides with respect to the positive line 28p and the negative line 28n. Each connection point of a pair of transistors T11 to T16 is connected to the three-phase (U-phase, V-phase, W-phase) coils of the motor 22. Therefore, by adjusting the ratio of the on-times of the paired transistors T11 to T16, the ECU 50 forms a rotating magnetic field in the three-phase coils of the motor 22, and the motor 22 (rotor) is driven to rotate. Hereafter, transistors T11 and T14 will be referred to as the "U-phase arm," transistors T12 and T15 as the "V-phase arm," and transistors T13 and T16 as the "W-phase arm."

[0016] The battery 26 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery. The positive and negative terminals of the battery 26 are connected to the power line 28. A smoothing capacitor 30 is connected to the power line 28.

[0017] The ECU50 is equipped with a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, as well as various drive circuits and various logic ICs. Signals from various sensors are input to the ECU50. For example, the rotational position θm of the rotor of the motor 22 from the rotational position sensor 22a, and the phase currents Iu, Iv, and Iw of each phase of the motor 22 from the current sensors 22u, 22v, and 22w are input. The voltage Vb of the battery 26 from the voltage sensor 26v, the current Ib of the battery 26 from the current sensor 26i, the temperature Tb of the battery 26 from the temperature sensor 26t, and the voltage VH of the capacitor 30 (power line 28) from the voltage sensor 30v are also input. The ECU 50 also receives an on / off signal from the power switch 60, the operating position of the shift lever 61 from the shift position sensor 62 (shift position SP), the amount of depression of the accelerator pedal 63 from the accelerator pedal position sensor 64 (accelerator opening Acc), the amount of depression of the brake pedal 65 from the brake pedal position sensor 66 (brake pedal position BP), and the vehicle speed V from the vehicle speed sensor 67. The ECU 50 outputs switching control signals to the transistors T11 to T16 of the inverter 24. The ECU 50 calculates the electrical angle θe and rotational speed Nm of the motor 22 based on the rotational position θm of the rotor of the motor 22, and calculates the charge level (SOC) of the battery 26 based on the integrated value of the current Ib of the battery 26.

[0018] In the electric vehicle 10 of this embodiment, the ECU 50 sets the required torque Td* required for driving (required to the drive shaft 16) based on the accelerator opening Acc and vehicle speed V, sets the torque command Tm* for the motor 22 to drive with the set required torque Td*, and performs switching control of transistors T11 to T16 of the inverter 24 based on the set torque command Tm*.

[0019] Here, the control of the inverter 24 by the ECU 50 will be described. FIG. 2 is a block diagram showing an example of functional blocks in the control of the inverter 24 by the ECU 50. As shown in the figure, the ECU 50, through the cooperation of hardware such as a CPU and a plurality of programs (software) installed in a ROM or a flash memory, functions as functional blocks including a current command setting unit 71, a dq-axis current calculation unit 72, a subtraction unit 73, a d-axis voltage command calculation unit 74, a subtraction unit 75, a q-axis voltage command calculation unit 76, a phase voltage command calculation unit 77, a phase voltage command correction unit 78, a duty conversion unit 79, and a triangular wave comparison unit 80.

[0020] The current command setting unit 71 sets the current commands Id*, Iq* for the d-axis and q-axis based on the torque command Tm*. The current commands Id*, Iq* for the d-axis and q-axis are set, for example, by applying the torque command Tm* to a map predetermined by experiments, analysis, etc. as the relationship between the torque command Tm* and the current commands Id*, Iq*, and deriving the corresponding current commands Id*, Iq* from the map. The dq-axis current calculation unit 72 performs coordinate transformation (three-phase to two-phase transformation) of the phase currents Iu, Iv, Iw of the U-phase, V-phase, and W-phase into the d-axis and q-axis currents Id, Iq using the electrical angle θe of the motor 22. The subtraction unit 73 subtracts the d-axis current Id from the d-axis current command Id*. The d-axis voltage command calculation unit 74 calculates the d-axis voltage command Vd* by current feedback control so that the value (Id* - Id) obtained by subtracting the d-axis current Id from the d-axis current command Id* is canceled out. The subtraction unit 75 subtracts the q-axis current Iq from the q-axis current command Iq*. The q-axis voltage command calculation unit 76 calculates the q-axis voltage command Vq* by current feedback control so that the value (Iq* - Iq) obtained by subtracting the q-axis current Iq from the q-axis current command Iq* is canceled out.

[0021] The phase voltage command calculation unit 77 performs coordinate transformation (two-phase to three-phase conversion) on the voltage commands Vd* and Vq* of the d-axis and q-axis using the electrical angle θe of the motor 22 to obtain the voltage commands Vu*, Vv*, and Vw* of the U-phase, V-phase, and W-phase. The phase voltage command correction unit 78 corrects any one of the voltage commands Vu*, Vv*, and Vw* of the U-phase, V-phase, and W-phase as necessary. The duty conversion unit 79 divides the voltage commands Vu*, Vv*, and Vw* of the U-phase, V-phase, and W-phase by the voltage VH of the capacitor 30 (power line 28) to calculate the duty commands Du*, Dv*, and Dw* of the U-phase, V-phase, and W-phase. The triangular wave comparison unit 80 generates the PWM signals Su*, Sv*, and Sw* of the U-phase, V-phase, and W-phase by comparing the duty commands Du*, Dv*, and Dw* of the U-phase, V-phase, and W-phase with a triangular wave (carrier). When the PWM signals Su*, Sv*, and Sw* of the U-phase, V-phase, and W-phase are generated in this way, they are used to perform the switching of the transistors T11 to T16.

[0022] Here, the details of the phase voltage command correction unit 78 will be described. The phase voltage command correction unit 78 executes the processing routine of FIG. 3. In the embodiment, at the timing of the peak and valley of the triangular wave, as an interrupt process, after the voltage commands Vu*, Vv*, and Vw* of the U-phase, V-phase, and W-phase from the next valley and peak timing of the triangular wave (specifically, from the next valley and peak timing to the next peak and valley timing) are set by the current command setting units 71 to the phase voltage command calculation unit 77, the phase voltage command correction unit 78 executes the processing routine of FIG. 3.

[0023] When the processing routine shown in Figure 3 is executed, the ECU 50 first determines whether the current interrupt is a trough timing interrupt (hereinafter referred to as a "trough interrupt") or a peak timing interrupt (hereinafter referred to as a "peak interrupt") of the triangular wave (step S100). If it is determined that the current interrupt is a trough interrupt, the ECU 50 calculates the difference ΔVuv as the absolute value of the difference between the U-phase voltage command Vu* and the V-phase voltage command Vv* from the phase voltage command calculation unit 77 (step S110), and compares the calculated difference ΔVuv with the threshold value ΔVref (step S112). When the PWM signals Su*, Sv*, and Sw* for each phase are generated and the switching of each phase arm is performed, there is a concern that the surge voltage applied to the motor 22 may become relatively large if the switching timings of the two phase arms are relatively close to each other. The threshold value ΔVref is used to determine whether or not such a concern exists.

[0024] If it is determined in step S112 that the difference ΔVuv is less than the threshold ΔVref, it is determined that there is a concern that the surge voltage applied to the motor 22 will be relatively large because the switching timings of the U-phase and V-phase arms are relatively close to each other, and the voltage commands Vu* and Vv* of the U-phase and V-phase are compared with each other (step S114). In this case, the voltage commands Vu* and Vv* are the values ​​of the timing of the next peak of the triangular wave, so the U-phase and V-phase PWM signals Su* and Sv* will be switched from off to on at the cross timing between the U-phase and V-phase duty commands Du* and Dv* based on the voltage commands Vu* and Vv* and the descending triangular wave (hereinafter referred to as the "U-phase and V-phase descending cross timings" respectively). Therefore, the cross timing between the smaller of the duty commands Du* and Dv* and the triangular wave will be later than the cross timing between the larger of the duty commands and the triangular wave. Note that the duty cycle commands Du* and Dv* are obtained by dividing the voltage commands Vu* and Vv* by the voltage VH of capacitor 30 (power line 28), so the relative magnitudes of the duty cycle commands Du* and Dv* are the same as the relative magnitudes of the voltage commands Vu* and Vv*. The process in step S114 is to determine which of the U-phase and V-phase down cross timings is slower.

[0025] If step S114 determines that the U-phase voltage command Vu* is less than the V-phase voltage command Vv*, it is determined that the U-phase down cross timing is slower than the V-phase down cross timing, and the voltage command Vu* is corrected by setting a new voltage command Vu* with a value obtained by subtracting a predetermined value α from the voltage command Vu* (step S116), and this routine ends. On the other hand, if step S114 determines that the U-phase voltage command Vu* is greater than or equal to the V-phase voltage command Vv*, it is determined that the V-phase down cross timing is slower than the U-phase down cross timing or that both are the same, and the voltage command Vv* is corrected by setting a new voltage command Vv* with a value obtained by subtracting a predetermined value α from the voltage command Vv* (step S118), and this routine ends. The processing in steps S116 and S118 is a process to correct either the voltage command Vu* or Vv* so that the slower of the U-phase or V-phase down cross timing becomes even slower. The predetermined value α is determined based on the slope of the triangular wave, etc., as a value that can suppress the surge voltage applied to the motor 22 from becoming relatively large. This process suppresses the switching timing of the U-phase and V-phase arms from becoming relatively close, thereby suppressing the surge voltage applied to the motor 22 from becoming relatively large.

[0026] If it is determined in step S112 that the difference ΔVuv is greater than or equal to the threshold ΔVref, the difference ΔVuw is calculated as the absolute value of the value obtained by subtracting the W-phase voltage command Vw* from the U-phase voltage command Vu* from the phase voltage command calculation unit 77 (step S130), and the calculated difference ΔVuw is compared with the threshold ΔVref (step S132). If it is determined that the difference ΔVuw is less than the threshold ΔVref, the U-phase and W-phase voltage commands Vu* and Vw* are compared with each other (step S134). If it is determined that the U-phase voltage command Vu* is less than the W-phase voltage command Vw*, the voltage command Vu* is corrected by setting a new voltage command Vu* to a value obtained by subtracting a predetermined value α from the voltage command Vu* (step S136), and this routine is terminated. On the other hand, when it is determined that the voltage command Vu* of the U phase is equal to or greater than the voltage command Vw* of the W phase, the voltage command Vw* is corrected by setting a new voltage command Vw* to a value obtained by subtracting a predetermined value α from the voltage command Vw* (step S138), and this routine is terminated.

[0027] The processing in steps S130 to S138 for voltage commands Vu* and Vw* is the same as the processing in steps S110 to S118 for voltage commands Vu* and Vv*. That is, when the difference ΔVuw is less than the threshold ΔVref, it is determined that there is a concern that the surge voltage applied to the motor 22 will be relatively large due to the switching timings of the U-phase and W-phase arms being relatively close to each other, and one of the voltage commands Vu* and Vw* is corrected so that the later of the crossover timings of the duty cycle commands Du* and Dw* based on the voltage commands Vu* and Vw* and the descending triangular wave becomes even later. This processing suppresses the switching timings of the U-phase and W-phase arms from being relatively close, and suppresses the surge voltage applied to the motor 22 from becoming relatively large.

[0028] If it is determined in step S132 that the difference ΔVuw is greater than or equal to the threshold ΔVref, the difference ΔVvw is calculated as the absolute value of the value obtained by subtracting the W-phase voltage command Vw* from the V-phase voltage command Vv* from the phase voltage command calculation unit 77 (step S150), and the calculated difference ΔVvw is compared with the threshold ΔVref (step S152). If it is determined that the difference ΔVvw is less than the threshold ΔVref, the V-phase and W-phase voltage commands Vv* and Vw* are compared with each other (step S154). If it is determined that the V-phase voltage command Vv* is less than the W-phase voltage command Vw*, the voltage command Vv* is corrected by setting a new voltage command Vv* to a value obtained by subtracting a predetermined value α from the voltage command Vv* (step S156), and this routine is terminated. On the other hand, when it is determined that the voltage command Vv* of the V phase is equal to or greater than the voltage command Vw* of the W phase, the voltage command Vw* is corrected by setting a new voltage command Vw* to a value obtained by subtracting a predetermined value α from the voltage command Vw* (step S158), and this routine is terminated.

[0029] The processing in steps S150 to S158 for voltage commands Vv* and Vw* is the same as the processing in steps S110 to S118 for voltage commands Vu* and Vv*. That is, when the difference ΔVvw is less than the threshold ΔVref, it is determined that there is a concern that the surge voltage applied to the motor 22 will be relatively large due to the switching timings of the V-phase and W-phase arms being relatively close to each other, and one of the voltage commands Vv* and Vw* is corrected so that the later of the crossover timings of the duty cycle commands Dv* and Dw* based on the voltage commands Vv* and Vw* and the descending triangular wave becomes even later. This processing suppresses the switching timings of the V-phase and W-phase arms from being relatively close, and suppresses the surge voltage applied to the motor 22 from being relatively large. If it is determined in step S152 that the difference ΔVvw is greater than or equal to the threshold ΔVref, this routine is terminated without correcting any of the voltage commands Vu*, Vv*, and Vw* for the U-phase, V-phase, and W-phase.

[0030] If it is determined in step S100 that the current interrupt is a mountain interrupt, the difference ΔVuv is calculated as the absolute value of the difference between the U-phase voltage command Vu* and the V-phase voltage command Vv* from the phase voltage command calculation unit 77 (step S120), and the calculated difference ΔVuv is compared with the threshold ΔVref (step S122). The process in step S122 is the same as the process in step S112.

[0031] If it is determined in step S122 that the difference ΔVuv is less than the threshold ΔVref, it is determined that there is a concern that the surge voltage applied to the motor 22 will be relatively large because the switching timings of the U-phase and V-phase arms are relatively close to each other, and the voltage commands Vu* and Vv* of the U-phase and V-phase are compared (step S124). In this case, the voltage commands Vu* and Vv* are the values ​​of the timing of the next trough of the triangular wave, so the U-phase and V-phase PWM signals Su* and Sv* will be switched from on to off at the cross timing between the U-phase and V-phase duty commands Du* and Dv* based on the voltage commands Vu* and Vv* and the rising triangular wave (hereinafter referred to as the "U-phase and V-phase rising cross timings" respectively). Therefore, the cross timing between the larger of the duty commands Du* and Dv* and the triangular wave will be later than the cross timing between the smaller of the duty commands and the triangular wave. The process in step S124 is to determine which of the U-phase and V-phase rising cross timings is later.

[0032] If step S124 determines that the U-phase voltage command Vu* is greater than the V-phase voltage command Vv*, then it is determined that the U-phase up cross timing is later than the V-phase up cross timing, and the voltage command Vu* is corrected by setting a new voltage command Vu* with a predetermined value α added to the voltage command Vu* (step S126), and the routine ends. On the other hand, if step S124 determines that the U-phase voltage command Vu* is less than or equal to the V-phase voltage command Vv*, then it is determined that the V-phase up cross timing is later than the U-phase up cross timing or that both are the same, and the voltage command Vv* is corrected by setting a new voltage command Vv* with a predetermined value α added to the voltage command Vv* (step S128), and the routine ends. The processing in steps S126 and S128 is a process to correct either the voltage command Vu* or Vv* so that the later of the U-phase and V-phase up cross timings becomes even later. This process suppresses the switching timings of the U-phase and V-phase arms from becoming relatively close, thereby suppressing the surge voltage applied to the motor 22 from becoming relatively large.

[0033] If it is determined in step S122 that the difference ΔVuv is greater than or equal to the threshold ΔVref, the difference ΔVuw is calculated as the absolute value of the value obtained by subtracting the W-phase voltage command Vw* from the U-phase voltage command Vu* from the phase voltage command calculation unit 77 (step S140), and the calculated difference ΔVuw is compared with the threshold ΔVref (step S142). If it is determined that the difference ΔVuw is less than the value ΔVref, the U-phase and W-phase voltage commands Vu* and Vw* are compared with each other (step S144). If it is determined that the U-phase voltage command Vu* is greater than the W-phase voltage command Vw*, the voltage command Vu* is corrected by setting a new voltage command Vu* to a value obtained by adding a predetermined value α to the voltage command Vu* (step S146), and this routine is terminated. On the other hand, when it is determined that the voltage command Vu* of the U phase is less than or equal to the voltage command Vw* of the W phase, the voltage command Vw* is corrected by adding a predetermined value α to the voltage command Vw* and setting that value as the new voltage command Vw* (step S148), and this routine ends.

[0034] The processing in steps S140 to S148 for voltage commands Vu* and Vw* is the same as the processing in steps S120 to S128 for voltage commands Vu* and Vv*. That is, when the difference ΔVuw is less than the threshold ΔVref, it is determined that there is a concern that the surge voltage applied to the motor 22 will be relatively large due to the switching timings of the U-phase and W-phase arms being relatively close to each other, and one of the voltage commands Vu* and Vw* is corrected so that the later of the crossover timings of the duty cycle commands Du* and Dw* based on the voltage commands Vu* and Vw* and the rising triangular wave becomes even later. This processing suppresses the switching timings of the U-phase and W-phase arms from being relatively close, and suppresses the surge voltage applied to the motor 22 from becoming relatively large.

[0035] If it is determined in step S142 that the difference ΔVuw is greater than or equal to the threshold ΔVref, the difference ΔVvw is calculated as the absolute value of the value obtained by subtracting the W-phase voltage command Vw* from the V-phase voltage command Vv* from the phase voltage command calculation unit 77 (step S160), and the calculated difference ΔVvw is compared with the threshold ΔVref (step S162). If it is determined that the difference ΔVvw is less than the value ΔVref, the V-phase and W-phase voltage commands Vv* and Vw* are compared with each other (step S164). If it is determined that the V-phase voltage command Vv* is greater than the W-phase voltage command Vw*, the voltage command Vv* is corrected by setting a new voltage command Vv* to a value obtained by adding a predetermined value α to the voltage command Vv* (step S166), and this routine is terminated. On the other hand, when it is determined that the voltage command Vv* of the V phase is less than or equal to the voltage command Vw* of the W phase, the voltage command Vw* is corrected by adding a predetermined value α to the voltage command Vw* and setting that value as the new voltage command Vw* (step S168), and this routine ends.

[0036] The processing in steps S160 to S168 for voltage commands Vv* and Vw* is the same as the processing in steps S120 to S128 for voltage commands Vu* and Vv*. That is, when the difference ΔVvw is less than the threshold ΔVref, it is determined that there is a concern that the surge voltage applied to the motor 22 will be relatively large due to the switching timings of the V-phase and W-phase arms being relatively close to each other, and one of the voltage commands Vv* and Vw* is corrected so that the later of the crossover timings of the duty cycle commands Dv* and Dw* based on the voltage commands Vv* and Vw* and the rising triangular wave becomes even later. This processing suppresses the switching timings of the V-phase and W-phase arms from being relatively close, and suppresses the surge voltage applied to the motor 22 from being relatively large. If it is determined in step S162 that the difference ΔVvw is greater than or equal to the threshold ΔVref, this routine is terminated without correcting any of the voltage commands Vu*, Vv*, and Vw* for the U-phase, V-phase, and W-phase.

[0037] Figure 4 is an explanatory diagram showing an example of the relationship between duty cycles Du*, Dv* and the triangular wave and PWM signals Su*, Sv*. In the figure, times t11, t13, and t15 are the trough timings of the triangular wave, and trough interrupt processing is performed. Times t12 and t14 are the peak timings of the triangular wave, and peak interrupt processing is performed. In addition, the PWM signals Su*, Sv* are switched from on to off at the U-phase and V-phase up cross timing, and the PWM signals Su*, Sv* are switched from off to on at the U-phase and V-phase down cross timing. Note that the duty cycle commands Du*, Dv* are obtained by dividing the voltage commands Vu*, Vv* by the voltage VH of capacitor 30 (power line 28), so the magnitude relationship of the duty cycle commands Du*, Dv* is the same as the magnitude relationship of the voltage commands Vu*, Vv*.

[0038] In this embodiment, at times t11, t12, t13, ..., voltage commands Vu*, Vv*, Vw* are set for times t12~t13, t13~t14, t14~t15, ... as valley interrupt processing, peak interrupt processing, valley interrupt processing, ... respectively. Then, at the valley interrupt processing at time t13, if it is determined that the difference ΔVuv is less than the threshold ΔVref and that the voltage command Vu* is less than the voltage command Vv* (duty command Du* is less than the duty command Dv*), it is determined that the U-phase down cross timing is later than the V-phase down cross timing, and the voltage command Vu* is corrected by setting a new voltage command Vu* to a value obtained by subtracting a predetermined value α from the voltage command Vu*. As a result, the duty cycle command Du* at times t14 to t15 is changed from the value corresponding to the uncorrected voltage command Vu* to the value corresponding to the corrected voltage command Vv* (change from solid line to dashed line in the figure). This correction of the voltage command Vu* (duty cycle command Du*) delays the timing of switching the PWM signal Su* from off to on (change from solid line to dashed line in the figure), suppresses the switching timing of the U-phase and V-phase arms from becoming relatively close, and suppresses the surge voltage applied to the motor 22 from becoming relatively large. Note that the correction of either the voltage command Vu* or Vw* when the difference ΔVuw is less than the threshold ΔVref, and the correction of either the voltage command Vv* or Vw* when the difference ΔVvw is less than the threshold ΔVref are omitted here.

[0039] In the drive system mounted on the electric vehicle 10 of the embodiment described above, when the difference ΔVuv between voltage commands Vu* and Vv* is less than the threshold ΔVref, one of the voltage commands Vu* and Vv* is corrected so that the later of the duty cycle commands Du* and Dv* based on the voltage commands Vu* and Vv* and the triangular wave crossover timing becomes even later. This suppresses the switching timings of the U-phase and V-phase arms from becoming relatively close, and suppresses the surge voltage applied to the motor 22 from becoming relatively large. The same applies when the difference ΔVuw between voltage commands Vu* and Vw* is less than the threshold ΔVref, or when the difference ΔVvw between voltage commands Vv* and Vw* is less than the threshold ΔVref. Moreover, without providing a simultaneous switching prevention circuit (adding hardware configuration) as in the above-mentioned Patent Document 1, the surge voltage applied to the motor 22 is suppressed to become relatively large by correcting one of the voltage commands Vu*, Vv*, and Vw*, thus suppressing instability in the control of the motor 22.

[0040] In the embodiment described above, the phase voltage command calculation unit 77 uses the electrical angle θe of the motor 22 to perform coordinate transformations on the voltage commands Vd* and Vq* of the d axis and q axis to the voltage commands Vu*, Vv* and Vw* of the U phase, V phase and W phase, respectively, but is not limited to this. For example, instead of the electrical angle θe, a predicted electrical angle θees may be used, which is the electrical angle θe with a compensation amount Δθe added to it. The compensation amount Δθe is used to compensate for the difference between the electrical angle θe used in the dq axis current calculation unit 72 and the actual electrical angle when the phase voltage command calculation unit 77 is executed, and is set to increase as the rotational speed Nm of the motor 32 increases.

[0041] In the embodiment described above, the duty cycle conversion unit 79 calculates the duty cycle commands Du*, Dv*, Dw* for the U-phase, V-phase, and W-phase by dividing the voltage commands Vu*, Vv*, Vw* for the U-phase, V-phase, and W-phase by the voltage VH of the capacitor 30 (power line 28), and the triangular wave comparison unit 80 generates the PWM signals Su*, Sv*, Sw* for the U-phase, V-phase, and W-phase by comparing the duty cycle commands Du*, Dv*, Dw* for the U-phase, V-phase, and W-phase with a triangular wave, but the embodiment is not limited to this. For example, without the duty cycle conversion unit 79, the triangular wave comparison unit 80 may generate the PWM signals Su*, Sv*, Sw* for the U-phase, V-phase, and W-phase by comparing the voltage commands Vu*, Vv*, Vw* for the U-phase, V-phase, and W-phase with a triangular wave. In this case, the amplitude of the triangular wave may be set to a value obtained by multiplying the reference value by the voltage VH of capacitor 30. Also, when the difference ΔVuv between voltage commands Vu* and Vv* is less than the threshold ΔVref, either of the voltage commands Vu* or Vv* should be corrected so that the later of the crossover timings between the voltage commands Vu* and Vv* and the triangular wave becomes even later. The same applies when the difference ΔVuw between voltage commands Vu* and Vw* is less than the threshold ΔVref, or when the difference ΔVvw between voltage commands Vv* and Vw* is less than the threshold ΔVref.

[0042] In the embodiment described above, interrupt processing is performed at the timing of the peaks and troughs of the triangular wave, but this is not limited to this. For example, interrupt processing may be performed only at the timing of either the peak or trough of the triangular wave. When interrupt processing is performed only at the timing of the trough of the triangular wave, the current command setting unit 71 to the phase voltage command calculation unit 77 set the voltage commands Vu*, Vv*, Vw* for the U phase, V phase, and W phase from the timing of the next trough of the triangular wave onward (specifically, from the timing of the next trough to the timing of the next trough), and then the phase voltage command correction unit 78 executes the processing routine shown in Figure 3. In step S100, it is determined that the current interrupt processing is a trough interrupt processing, and the processing from step S110 onward is executed. If interrupt processing is to be executed only at the timing of the peaks of the triangular wave, the current command setting unit 71 to the phase voltage command calculation unit 77 set the voltage commands Vu*, Vv*, Vw* for the U phase, V phase, and W phase from the timing of the next peak of the triangular wave onward (specifically, from the timing of the next peak to the timing of the next peak), and then the phase voltage command correction unit 78 executes the processing routine shown in Figure 3. In step S100, it is determined that the current interrupt processing is a peak interrupt processing, and the processing from step S120 onward is executed.

[0043] In the embodiment described above, the drive system is configured to be mounted on an electric vehicle 10 that includes a motor 22, an inverter 24, and a battery 26, but it is not limited to this. For example, it may be configured to be mounted on a hybrid vehicle that has an engine in addition to the same hardware configuration as the electric vehicle 10, or it may be configured to be mounted on a fuel cell vehicle that has a fuel cell in addition to the same hardware configuration as the electric vehicle 10.

[0044] The above describes the forms for implementing this disclosure using embodiments, but this disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0045] This disclosure can be used in industries such as the manufacturing of drive systems. [Explanation of Symbols]

[0046] 22 Motor, 22a Rotation position sensor, 22u, 22v, 22w, 26i Current sensor, 24 Inverter, 26 Battery, 26t Temperature sensor, 26v, 30v Voltage sensor, 28 Power line, 28n Negative electrode line, 28p Positive electrode line, 30 Capacitor, 32 Motor, 50 ECU, 71 Current command setting unit, 72 DQ axis current calculation unit, 73, 75 Subtraction unit, 74 D axis voltage command calculation unit, 76 Q axis voltage command calculation unit, 77 Phase voltage command calculation unit, 78 Phase voltage command correction unit, 79 Duty cycle conversion unit, 80 Triangular wave comparison unit, D11~D16 Diodes, T11~T16 Transistors.

Claims

1. A drive device comprising: a motor; an inverter for driving the motor; and a control device that sets three-phase voltage commands based on the torque command of the motor, generates three-phase PWM signals by comparing the three-phase voltage command-related values ​​associated with the three-phase voltage commands with a triangular wave, and controls the inverter, The control device corrects the voltage command-related values ​​so that the later of the crossover timings between the two phases of the voltage command-related values ​​and the triangular wave becomes even later when the difference between the voltage command-related values ​​of two phases and the voltage command-related values ​​of the three phases is less than or equal to a predetermined difference. Drive unit.

2. A drive device according to claim 1, The control device sets the voltage command-related values ​​for the three phases from the timing of the next peak of the triangular wave onward at the timing of the trough of the triangular wave, and when the difference is less than or equal to the predetermined difference, it corrects the voltage command-related values ​​so that the cross timing of the two phases with the descending triangular wave becomes even later. Drive unit.

3. A drive device according to claim 1 or 2, The control device sets the voltage command-related values ​​for the three phases from the timing of the next trough of the triangular wave onward at the timing of the peak of the triangular wave, and when the difference is less than or equal to the predetermined difference, it corrects the voltage command-related values ​​so that the cross timing of the two phases that has a later cross timing with the rising triangular wave becomes even later. Drive unit.

4. A drive device according to claim 1, The control device sets the three-phase duty cycle commands based on the three-phase voltage commands, and generates the three-phase PWM signals by comparing the three-phase duty cycle commands with the triangular wave. The control device corrects the voltage command such that the later of the two phase duty cycle commands and the triangular wave crossover timings becomes even later when the difference between the two phase voltage commands is less than or equal to the predetermined difference. Drive unit.

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