Motor control device and electric vehicle

Abstract

In a state in which an inverter (power converter 2) and a DC power supply (DC power supply 9) are connected to each other, a processor of a motor control device (300) switches a plurality of switching elements of the inverter and thereby performs normal control for converting DC current supplied from the DC power supply into AC current and supplying the AC current to a motor (PMSM1). When the inverter and the DC power supply are disconnected (power shortage detection), the processor switches the plurality of switching elements and thereby performs constant output voltage control, fixing the output voltage of the inverter to a value near zero. Thus, when the DC power supply and the inverter are disconnected, the overvoltage of the capacitor of the inverter and the current vibration of the motor can be suppressed.

Description

Motor control device and electric vehicle

[0001] The present invention relates to a motor control device and an electric vehicle.

[0002] In motor drive systems, a switching device is provided to separate the DC power supply from the inverter to protect the DC power supply (the battery in the case of an automobile) from overvoltage and overcurrent. If the DC power supply is separated by this switching device, the inverter's capacitor may be charged by the regenerative power of the motor, which may cause damage due to overvoltage.

[0003] In Patent Document 1, when disconnection is performed by the switching means, all of the upper arms or all of the lower arms of the inverter are turned on to perform a three-phase short circuit, thereby suppressing overvoltage in the capacitor.

[0004] In Patent Document 2, the current is controlled to the current when a three-phase short circuit occurs, and then the three-phase short circuit is performed, thereby suppressing the overvoltage of the capacitor and the current jump when the three-phase short circuit is switched.

[0005] Japanese Patent Publication No. 9-47055 Japanese Patent Publication No. 6342043 Japanese Patent Publication No. 5948266 Japanese Patent Publication No. 2021-151003

[0006] The method of Patent Document 1 can suppress the overvoltage of the capacitor, but has the problem of current jumping when switching between three-phase short circuits.

[0007] Although Patent Document 2 addresses this issue, the output voltage is uniquely determined in a three-phase short circuit, so current jumps occur depending on the current controlled immediately before the three-phase short circuit. Alternatively, there is the problem that current oscillations continue after switching to a three-phase short circuit.

[0008] In view of the above, an object of the present invention is to provide a motor control device and an electric vehicle that can suppress overvoltage in the inverter capacitor and current oscillation in the motor when the DC power supply and the inverter are disconnected.

[0009] In order to achieve the above object, one example of a motor control device of the present invention includes a processor that performs normal control in which, when an inverter is connected to a DC power supply, the DC current supplied from the DC power supply is converted into AC current by switching multiple switching elements of the inverter and supplied to the motor, and constant output voltage control in which, when the inverter is disconnected from the DC power supply, the output voltage of the inverter is fixed to a value close to zero by switching multiple switching elements.

[0010] According to the present invention, when the DC power supply and the inverter are disconnected, it is possible to suppress the overvoltage of the inverter capacitor and the current oscillation of the motor. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments.

[0011] 1 is a block diagram showing the overall configuration of a motor control device according to a first embodiment. An example of a block diagram of a current command value generating unit according to the first embodiment. An example of a block diagram of an output voltage switching unit according to the first embodiment. A flowchart according to the first embodiment. An example of a voltage command value according to the first embodiment. A block diagram showing the overall configuration of a motor control device according to a second embodiment. An example of a block diagram of a damping ratio control unit 14 according to the second embodiment. An example of a block diagram of an output voltage switching unit 18B according to the second embodiment. An example of a voltage command value according to the second embodiment. Another example of a voltage command value according to the second embodiment. A block diagram showing the overall configuration of a motor control device according to a third embodiment. An example of a block diagram of a damping ratio control unit 14B according to the third embodiment. A configuration diagram of an electric vehicle according to a fourth embodiment.

[0012] Although the following description focuses on a permanent magnet synchronous motor (PMSM), the effects of the embodiments of the present invention are not limited to permanent magnet synchronous motors, and similar effects can be obtained with any AC motor or AC generator, such as a synchronous reluctance motor, a permanent magnet synchronous generator, a wound-rotor synchronous machine, an induction motor, or an induction generator. Also, although the semiconductor switching elements of the inverter device are IGBTs, the effects of the embodiments of the present invention are not limited to this, and may be MOSFETs or other power semiconductor elements.

[0013] First Embodiment The components of the first embodiment will be described.

[0014] FIG. 1 is a block diagram showing the overall configuration of a motor control device 300 according to a first embodiment of the present invention.

[0015] The overall configuration of a motor control device 300 of this embodiment will be described with reference to Fig. 1. In Fig. 1, a power converter 2 has a switching device 6 and a capacitor 8 between it and a DC voltage source 9 (e.g., a battery), and during normal operation, the switching device 6 is closed and DC power from the DC voltage source 9 is converted into AC power in accordance with a gate signal, which will be described later, to drive a PMSM 1.

[0016] The phase current detection means 3 is comprised of a Hall CT (Current Transformer) or the like, and detects the current waveforms Iuc, Ivc, and Iwc of three phases, U, V, and W, that flow from the power converter 2 to the PMSM 1. The magnetic pole position detection means 4 is comprised of a resolver or the like, and detects the magnetic pole position of the PMSM 1 and outputs magnetic pole position information θ*. The frequency calculation unit 5 outputs speed information ω1* from the magnetic pole position information θ* detected by the magnetic pole position detection means 4, for example, by a differential calculation.

[0017] A coordinate conversion unit 7 converts Iuc, Ivc, and Iwc detected by the phase current detection means 3 into coordinates using magnetic pole position information θ* detected by the magnetic pole position detection means 4, and outputs dq-axis current detection values ​​Idc and Iqc. A current command value generation unit 12 normally generates dq-axis current command values ​​Id* and Iq* based on the torque command value T* and speed information ω1* using, for example, a look-up table or a formula. On the other hand, the operation when the opening and closing means 6 is opened due to a power supply abnormality or the like will be described later.

[0018] The current control unit 16 performs PI control so that the currents (dq-axis current detection values ​​Idc, Iqc) match the dq (dq-axis current command values ​​Id*, Iq*), respectively, and outputs dq-axis voltage command values ​​Vdc*, Vqc*. The output voltage switching unit 18 normally outputs dq-axis voltage command values ​​Vdc*, Vqc*. On the other hand, the operation when the switching means 6 is opened due to a power supply abnormality or the like will be described later. The coordinate conversion unit 11 converts the dq-axis voltage command values ​​Vd*, Vq* into three-phase voltage command values ​​Vu*, Vv*, Vw* based on the magnetic pole position θ*. The PWM controller 10 generates pulses by comparing them with, for example, a triangular wave, and generates and outputs gate signals taking dead time into consideration.

[0019] The current command value generating unit 12 and the output voltage switching unit 18, which are key features of the embodiment of the present invention, will be described below.

[0020] 2 shows an example of the current command value generator 12. A normal current command value generator 21 receives the torque command value T* and the speed ω1* as inputs and generates normal dq-axis current command values ​​Idn* and Iqn* using, for example, a look-up table. Next, an open-circuit dq-axis current command value generator 23 sets the open-circuit dq-axis current command values ​​Idop* and Iqop* using, for example, Equation 1, which corresponds to the steady-state currents for constant output voltage control in the open-circuit state.

[0021]

[0022] where Vdcst* and Vqcst* represent the d-axis and q-axis voltage command values ​​during constant output voltage control. R is the motor resistance, Φm is the permanent magnet flux linkage, Ld is the d-axis inductance, and Lq is the q-axis inductance.

[0023] When the setting is as in Equation 1, in the absence of parameter errors, it is possible to switch between open-circuit current control and constant output voltage control without torque shock or current fluctuation. When the open-circuit control flag fop is off, the switch 25 outputs the normal dq-axis current command values ​​Idn*, Iqn* as the dq-axis current command values ​​Id*, Iq*, and when the open-circuit control flag fop is on, it outputs the open-circuit dq-axis current command values ​​Idop*, Iqop*.

[0024] 3 shows an example of the output voltage switching unit 18. When the open control flag fop is turned on, the on-time delay 31 turns on the constant output voltage control flag fcst after a predetermined time has elapsed. The predetermined time is set, for example, to be five times or more the time constant of the current control, and the on-time delay 31 is turned on when the d-axis and q-axis currents match the open-circuit current command values ​​Idop* and Iqop*. When the constant output voltage control flag fcst is off, the switch 37 outputs the current control d-axis and q-axis voltage command values ​​Vdc* and Vqc* as the d-axis and q-axis voltage command values ​​Vd* and Vq*, and when the constant output voltage control flag fcst is on, it outputs the open-circuit d-axis and q-axis voltage command values ​​Vdop* and Vqop*.

[0025] The change amount limits 33, 35 for the switching transition period impose change amount limits on the dq-axis voltage command values ​​Vdcst*, Vqcst* during constant output voltage control, and output the open dq-axis voltage command values ​​Vdop*, Vqop*. By setting the change amount limits, it is possible to suppress the occurrence of current oscillations due to a sudden change in output voltage.

[0026] FIG. 4 shows a flowchart of Patent Document 2 and an embodiment of the present invention, and FIG. 5 shows example waveforms of voltage command values ​​of Patent Document 2 and an embodiment of the present invention (however, an example is shown in which the d-axis and q-axis voltage command values ​​Vdcst* and Vqcst* during constant output voltage control are both set to 0 V).

[0027] In Patent Document 2, when a power supply abnormality (opening of a switch) is detected, open-time current control is performed, the current is controlled so that it approaches the steady-state current of a three-phase short circuit, and after the current converges, the system switches to a three-phase short circuit. In the case of a three-phase short circuit, the voltage is fixed at 0 V, so a step occurs at the time of switching due to errors in parameters, etc.

[0028] On the other hand, in the embodiment of the present invention, when a power supply abnormality (opening of the switch) is detected, the open control flag fop is turned on and open current control is activated. In the open current control, a current command value of Equation 1 different from that in normal operation is set, and the current is controlled so that it approaches the steady current of constant output voltage control.

[0029] Next, when the constant output voltage control flag fcst is turned on after a predetermined time has elapsed in the on-time delay 31, the output voltage is switched from the current control dq-axis voltage command values ​​Vdc*, Vqc* to the open-circuit dq-axis voltage command values ​​Vd*, Vqop*. However, the output voltage is switched gradually until the output voltage is controlled to be constant by the change amount limits 33, 35 for the switching transition period. Unlike a three-phase short circuit, the output voltage can be switched, allowing for gradual switching and suppressing current spikes during switching.

[0030] When the dq-axis voltage command values ​​Vdcst* and Vqcst* are both set to 0 V during constant output voltage control, this is equivalent to a three-phase short circuit, but they do not necessarily have to be 0 V. They may be close to 0 V, which is a voltage at which an increase in the capacitor voltage is allowed.

[0031] In the embodiment of the present invention, since there is a risk that the capacitor voltage may rise depending on the error in dead time compensation, it is preferable to suppress the rise in the capacitor voltage by setting the d-axis voltage command value Vdcst* during constant output voltage control to a small negative value. Specifically, when the maximum error in dead time compensation is dter, it is preferable to set it using the following equation 2.

[0032]

[0033] where fc is the carrier frequency and Vdc is the DC voltage. When the output voltage is set to approximately 0, the current flows in the negative direction of the d-axis. In this case, the voltage error ΔVdt* due to the dead time appears entirely in the d-axis voltage and is expressed by the following equation 3.

[0034]

[0035] Dead time compensation is performed to compensate for this, but if the compensation is insufficient, the capacitor voltage will rise due to the input power calculated as the product of the voltage error ΔVdt* and the d-axis current Idc. The d-axis voltage command value Vdcst* can be set to prevent this. Note that, instead of setting the d-axis voltage command value Vdcst* to a negative value, the same effect can be achieved by setting the dead time compensation setting to overcompensate by the amount of the expected error.

[0036] The q-axis voltage command value Vqcst* is preferably set to 0 V as an average value in order to suppress fluctuations in the capacitor voltage.

[0037] In this embodiment, when the opening of the switch is detected, the opening control flag fop is turned on, but the method of detecting the opening of the switch may be any of the following: the capacitor voltage remains lower than a predetermined value for a predetermined period of time, a signal is received from the switch, etc. For example, in a system without a switch, it may be possible to consider a case where the wiring at the switch is cut and the capacitor voltage becomes low, and it is determined that the opening of the switch has been detected.

[0038] In addition, whereas heat concentrates in the upper arm or the lower arm in a three-phase short circuit, in this embodiment, the heat can be dispersed to the upper arm and the lower arm. Furthermore, the coordinate conversion unit 11 can adjust the heat balance between the upper arm and the lower arm by setting a zero-phase voltage when converting the dq-axis voltage command values ​​Vd* and Vq* into three-phase voltage command values ​​Vu*, Vv*, and Vw* based on the magnetic pole position θ*.

[0039] In this embodiment, the transition control is performed after the open-circuit current control is performed, but the transition control may be performed directly without the open-circuit current control.

[0040] In this embodiment, the open dq axis current command values ​​Idop* and Iqop* are set, but they may be set as shown in Equation 4, ignoring the resistance component.

[0041]

[0042] Alternatively, in consideration of the fact that the d-axis and q-axis voltage command values ​​Vdcst* and Vqcst* are set to minute values ​​during constant output voltage control, they may be approximated to 0 and set as shown in Equation 5.

[0043]

[0044] In the case of the embodiment of the present invention, since the switching can be performed gradually, even if there is a small error, the current can be shifted to constant output voltage control without jumping.

[0045] The main features of the first embodiment can be summarized as follows.

[0046] When the inverter (power converter 2) and DC power supply (DC voltage source 9) are connected, the processor of the motor control device 300 performs normal control, converting DC current supplied from the DC power supply into AC current by switching on and off multiple switching elements of the inverter, and supplies the AC current to the motor (PMSM1).When the inverter and DC power supply are disconnected (lack of power detection), the processor performs constant output voltage control, fixing the inverter output voltage to a value close to zero by switching on and off multiple switching elements (FIG. 5).

[0047] By switching multiple switching elements, the output voltage of the inverter (power converter 2) is fixed at a value close to zero, allowing the output voltage to be switched gradually. This suppresses current jumps when switching to constant output voltage control. As a result, when the DC power supply and the inverter are disconnected, overvoltage of the inverter capacitor and current oscillations in the motor can be suppressed. It also makes it possible to distribute heat between the upper and lower arms of the inverter.

[0048] The value near zero (including zero) is set by a formula, experiment, simulation, or the like so that the capacitor does not become overvoltage when the inverter is disconnected from the DC power supply.

[0049] For example, in the constant output voltage control, the processor fixes the q-axis output voltage (q-axis voltage command value Vqcst*) to zero. This suppresses the rise in the capacitor voltage of the inverter (power converter 2). As a result, the capacitor can be made smaller and less expensive.

[0050] In the constant output voltage control, the processor preferably sets the fixed value (d-axis voltage command value Vdcst*) that is the center value of the d-axis output voltage to a small negative value. This suppresses the induced voltage, thereby further suppressing the rise in the inverter capacitor voltage.

[0051] In the constant output voltage control, the processor changes the fixed value (d-axis voltage command value Vdcst*) in proportion to either or both of the carrier frequency fc and the DC voltage Vdc (Equation 2), thereby suppressing an increase in the capacitor voltage due to insufficient dead time compensation.

[0052] In the constant output voltage control, the processor may set a fixed value (d-axis voltage command value Vdcst*) that is the center value of the d-axis output voltage to zero, thereby suppressing an increase in the capacitor voltage of the inverter.

[0053] When the inverter and DC power supply are disconnected (lack of power detection), the processor performs open-circuit current control, which switches multiple switching elements so that the current of the motor (PMSM1) becomes a steady current in constant output voltage control (open-circuit dq-axis current command values ​​Idop*, Iqop*, Equation 1). This makes it possible to suppress torque shock and current oscillation when switching from open-circuit current control to constant output voltage control.

[0054] When the inverter and the DC power supply are disconnected (lack of power detected), the processor performs transition control to gradually bring the inverter output voltage to a value close to zero (variation limiters 33 and 35, FIG. 3). This makes it possible to further suppress current oscillation. In addition to the variation limiters 33 and 34 of the first embodiment, the transition control may also use a low-pass filter to gradually bring the output voltage to a value close to zero.

[0055] Second Embodiment The components of the second embodiment will be described.

[0056] FIG. 6 is a block diagram showing the overall configuration of a motor control device 300 according to a second embodiment of the present invention.

[0057] The differences in configuration from the first embodiment will be explained.

[0058] In the second embodiment, an attenuation ratio control unit 14 is added, and the output voltage switching unit 18 is changed to an output voltage switching unit 18B.

[0059] The damping ratio control unit 14 is configured, for example, as shown in Figure 7. The q-axis current command value is passed through a first-order lag filter 41, which takes into account the delay of ωc, the cutoff frequency of the current control unit 16, to take the difference with the q-axis current detection value Iqc, and then passed through a high-pass filter 45 to extract the first-order vibration component of the fundamental wave. Furthermore, this is multiplied by the speed ω1* in a multiplier 47, and then multiplied by twice the damping ratio ζ and the q-axis inductance Lq in a gain 49, to output a q-axis damping ratio control voltage command value Vqd*. Furthermore, the q-axis damping ratio control voltage command value Vqd* and the q-axis current detection value Iqc are multiplied by a multiplier 51, divided by Idc in a divider 53, and multiplied by -1 in a gain 55, to output a d-axis damping ratio control voltage command value Vdd*.

[0060] The output voltage switching unit 18B is configured as shown in Fig. 8, for example. The differences from Fig. 3 are that the change amount limits 33 and 35 are eliminated and that adders 38 and 39 are added. In the case of this embodiment, the damping ratio control unit 14 can suppress current oscillations at the time of switching, so that oscillations can be suppressed without providing a transition period.

[0061] The principle will be explained below.

[0062] Damping ratio control is a controller that suppresses the fundamental primary oscillation component, and is proposed in, for example, Patent Document 3. When a three-phase short circuit occurs, the voltage converges to a steady-state value while oscillating with the fundamental primary oscillation component. Unlike a three-phase short circuit, constant output voltage control as in the embodiment of the present invention can control the voltage, so suppressing the fundamental primary oscillation component makes it possible to suppress oscillation during switching.

[0063] Damping ratio control is performed on the q-axis because the current command value on the q-axis side is nearly zero. The input power is proportional to the product of the voltage and current, and a large current flows in the negative direction on the d-axis side. If damping ratio control were performed on the d-axis side, the capacitor voltage would fluctuate greatly due to oscillations in the voltage command value. On the other hand, because the current command value on the q-axis side is nearly zero, the current only has an oscillation component, and the amount of fluctuation is small. Furthermore, if the d-axis damping ratio control voltage command value Vdd* is given using the following equation 6 so as to cancel out the input power Pqd on the q-axis side, fluctuations in capacitor voltage due to damping ratio control can be completely suppressed.

[0064]

[0065] In this embodiment, similarly to the first embodiment, it is preferable to set a small negative value as the d-axis voltage command value Vdcst* during constant output voltage control.

[0066] As described above, this embodiment can suppress both the overvoltage and current oscillation of the capacitor.

[0067] The main features of the second embodiment can be summarized as follows.

[0068] 9A , when the inverter (power converter 2) and the DC power supply (DC voltage source 9) are disconnected, the processor performs damping ratio control to output a q-axis damping ratio control voltage (q-axis damping ratio control voltage command value Vqd*) so as to cancel out the vibration component of the q-axis current or magnetic flux. In constant output voltage control, the processor fixes the d-axis output voltage (open-circuit d-axis voltage command value Vdop*) to a predetermined value (d-axis voltage command value Vdcst*), and outputs the q-axis damping ratio control voltage (q-axis damping ratio control voltage command value Vqd*), which is the output of the damping ratio control, as the q-axis output voltage (open-circuit q-axis voltage command value Vqop*).

[0069] As a result, current oscillation can be suppressed when switching to constant output voltage control without providing a transition period. Note that, as shown in Fig. 8, the open-circuit dq-axis voltage command values ​​Vdop* and Vqop* are the sums of the dq-axis voltage command values ​​Vdcst* and Vqcst* and the dq-axis damping ratio control voltage command values ​​Vdd* and Vqd*, respectively, during constant output voltage control, but the example in Fig. 9A corresponds to the case where the d-axis damping ratio control voltage command value Vdd* = 0 and the q-axis voltage command value Vqcst* = 0.

[0070] As shown in FIG. 9B , in the damping ratio control, the processor outputs a d-axis damping ratio control voltage (d-axis damping ratio control voltage command value Vdd*) so as to cancel out the power due to the q-axis damping ratio control voltage (q-axis damping ratio control voltage command value Vqd*). In the constant output voltage control, the processor calculates the d-axis output voltage (open d-axis voltage command value Vdop*) by adding the d-axis damping ratio control voltage to a predetermined value (for example, a small negative value). This makes it possible to completely suppress fluctuations in the capacitor voltage due to the damping ratio control. Note that the example in FIG. 9B corresponds to the case where the q-axis voltage command value Vqcst*=0.

[0071] Third Embodiment The components of a third embodiment will be described.

[0072] FIG. 10 is a block diagram showing the overall configuration of a motor control device 300B according to a third embodiment of the present invention.

[0073] The differences in configuration from the second embodiment will be explained.

[0074] In the third embodiment, the current is controlled using the magnetic flux command value generating unit 13, the magnetic flux estimation value generating unit 15, and the magnetic flux control unit 17 described in Patent Document 4 instead of the current control unit 16. In addition, in accordance with the control using magnetic flux, the damping ratio control unit 14 is changed to a damping ratio control unit 14B.

[0075] The flux command value generation unit 13 generates dq-axis flux command values ​​φd*, φq* from the dq-axis current command values ​​Id*, Iq*. This is implemented using a lookup table, an approximate formula, or the like. The flux estimation value generation unit 15 generates dq-axis flux estimation values ​​φdc, φqc from the dq-axis current detection values ​​Idc, Iqc. The calculation method is the same as that of the flux command value generation unit 13. The flux control unit 17 controls using a PI controller so that the dq-axis flux command values ​​φd*, φq* and the dq-axis flux estimation values ​​φdc, φqc coincide with each other. As described in Patent Document 4, it may be configured using an integrator and an inverse model of the motor.

[0076] The configuration of the damping ratio control unit 14B is shown in Figure 11. The q-axis magnetic flux command value is passed through a first-order lag filter 61, which takes into account the delay of ωc, the cutoff frequency of the magnetic flux control unit 17, to take the difference with the q-axis magnetic flux estimate value φqc. This difference is then passed through a high-pass filter 65 to extract the first-order vibration component of the fundamental wave. This result is then multiplied by the speed ω1* in a multiplier 67, and multiplied by twice the damping ratio ζ in a gain 69 to output a q-axis damping ratio control voltage command value Vqd*. Furthermore, the q-axis damping ratio control voltage command value Vqd* and the q-axis current detection value Iqc are multiplied by a multiplier 71, divided by Idc in a divider 73, and multiplied by -1 in a gain 75 to output a d-axis damping ratio control voltage command value Vdd*.

[0077] Even if the input for the damping ratio control is magnetic flux, current oscillation can be suppressed when switching to constant output voltage control, as in the second embodiment.

[0078] Fourth Embodiment The components of a fourth embodiment will be described.

[0079] 12 shows the configuration of an electric vehicle according to a fourth embodiment of the present invention. As shown in the first to third embodiments, the motor control device 300 (or 300B) controls the power supplied from the power converter 2 to the PMSM 1. A DC voltage source 9 (e.g., a battery) supplies power to the power converter 2. The PMSM 1 is connected to a transmission 301. The transmission 301 is connected to a drive shaft 305 via a differential gear 303 and supplies power to wheels 307. Note that a configuration may be adopted in which the transmission 301 is not used and the drive shaft 305 is connected directly to the differential gear 303, or a configuration in which the PMSM 1 and power converter 2 are applied to both the front and rear wheels.

[0080] In automobiles, torque fluctuations are directly linked to ride comfort, so requirements for torque fluctuations are stricter than in other applications, making this an application in which the effects of the embodiments of the present invention are more readily apparent. By applying the present invention, ride comfort in automobiles can be improved during power supply abnormalities.

[0081] The main features of the fourth embodiment can be summarized as follows.

[0082] The electric vehicle is equipped with a motor control device 300 (or 300B) according to any one of the first to third embodiments. A motor (PMSM1) supplies power to wheels 307 of the electric vehicle. The motor control device 300 (or 300B) suppresses torque fluctuations during a power outage (when the battery and inverter are disconnected due to an inverter or battery abnormality such as an overcurrent or overvoltage, a vehicle malfunction, a collision, or the like). As a result, it is possible to suppress a sudden change in the driver's riding comfort during a power outage.

[0083] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0084] Furthermore, some or all of the above-described configurations, functions, etc. may be implemented in hardware, for example, by designing them as integrated circuits. Furthermore, the above-described configurations, functions, etc. may be implemented in software by a processor interpreting and executing a program that implements each function. Information such as the programs, tables, and files that implement each function can be stored in a memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

[0085] This embodiment may be configured as follows.

[0086] (1) An inverter control device that controls an inverter circuit that converts DC power into AC current and supplies it to a motor by switching on and off multiple switching elements, and that performs constant output voltage control to fix the output voltage of the inverter circuit to a value close to zero by switching on and off the switching elements when the inverter and DC power supply are disconnected due to the detection of an abnormality on the power supply side, etc.

[0087] (2) In the AC motor control device described in (1), the output voltage constant control is performed by fixing the q-axis output voltage to zero.

[0088] (3) In the AC motor control device described in (1), a damping ratio control is performed to output a q-axis damping ratio control voltage so as to cancel out the vibration component of the q-axis current, and the constant output voltage control fixes the d-axis output voltage to a predetermined value, and outputs a q-axis damping ratio control voltage that is the output of the damping ratio control as the q-axis output voltage.

[0089] (4) In the AC motor control device described in (3), the damping ratio control section outputs a d-axis damping ratio control voltage so as to cancel out the power due to the q-axis damping ratio control voltage, and the constant output voltage control is performed by adding the d-axis damping ratio control voltage to a predetermined d-axis output voltage.

[0090] (5) In the AC motor control device according to any one of (2) to (4), the constant output voltage control is characterized in that the fixed value that is the center value of the d-axis output voltage is a small negative value.

[0091] (6) In the AC motor control device described in (5), the constant output voltage control is characterized in that the central value of the d-axis output voltage is changed in proportion to either the carrier frequency or the DC voltage, or both.

[0092] (7) In the AC motor control device according to any one of (2) to (4), the constant output voltage control is characterized in that the fixed value that is the center value of the d-axis output voltage is zero.

[0093] (8) The AC motor control device according to any one of (1) to (7), further comprising open-circuit current control that switches the switching element so that the current of the motor becomes a steady-state current under constant output voltage control.

[0094] (9) The AC motor control device according to (8), further comprising a switching control for gradually switching from the open-circuit current control to the constant output voltage control.

[0095] (10) An electric vehicle equipped with an AC motor control device that drives an AC motor, the vehicle comprising the AC motor control device according to any one of (1) to (9) as the control device for the AC motor.

[0096] According to (1)-(10), both the capacitor overvoltage and the motor current oscillation can be suppressed, and it is possible to achieve both a reduction in the capacitor capacity and an improvement in the ride comfort during a power supply abnormality.

[0097] 1: PMSM 2: Power converter 3: Phase current detection means (phase current detector) 4: Magnetic pole position detection means (magnetic pole position detector) 5: Frequency calculation unit 6: Switching means (switch) 7: Coordinate conversion unit 8: Capacitor 9: DC voltage source 11: Coordinate conversion unit 12: Current command value generation unit 13: Magnetic flux command value generation unit 14: Damping ratio control unit 14B: Damping ratio control unit (Embodiment 3) 15: Magnetic flux estimated value generation unit 16: Current control unit 17: Magnetic flux control unit 18: Output voltage switching unit 18B: Output voltage switching unit (Embodiment 2) 21: Normal current command value generation unit 23: Open dq axis current command value generation unit 25: Switch 31: On-time delay 33: Change amount limit for switching transition period 35: Change amount limit for switching transition period 37: Switch 38: Adder 39: Adder 41: First-order lag filter (LPF) 43: Subtractor 45: High-pass filter 47: Multiplier 49: Gain 51: Multiplier 53: Divider 55: Gain 61: First-order lag filter (LPF) 63: Subtractor 65: High-pass filter 67: Multiplier 69: Gain 71: Multiplier 73: Divider 75: Gain 300: Motor control device 300B: Motor control device 301: Transmission 303: Differential gear 305: Drive shaft 307: Wheel

Claims

1. A motor control device equipped with a processor that performs normal control in which, when an inverter is connected to a DC power supply, a DC current supplied from the DC power supply is converted into AC current by switching a number of switching elements of the inverter and supplied to a motor, and when the inverter is disconnected from the DC power supply, a constant output voltage control in which, when the inverter is disconnected from the DC power supply, a constant output voltage control is performed ...

2. A motor control device according to claim 1, characterized in that said processor fixes the q-axis output voltage to zero in said constant output voltage control.

3. A motor control device as described in claim 1, wherein the processor, when the inverter and the DC power supply are disconnected, performs damping ratio control to output a q-axis damping ratio control voltage so as to cancel out the vibration component of the q-axis current or magnetic flux, and in the constant output voltage control, fixes the d-axis output voltage to a predetermined value and outputs the q-axis damping ratio control voltage, which is the output of the damping ratio control, as the q-axis output voltage.

4. A motor control device as described in claim 3, wherein the processor, in the damping ratio control, outputs a d-axis damping ratio control voltage so as to cancel out the power due to the q-axis damping ratio control voltage, and, in the constant output voltage control, calculates the d-axis output voltage by adding the d-axis damping ratio control voltage to the predetermined value.

5. A motor control device according to claim 2, wherein the processor sets a fixed value that is a central value of the d-axis output voltage to a very small negative value during the constant output voltage control.

6. A motor control device according to claim 5, characterized in that, in the constant output voltage control, said processor changes said fixed value in proportion to either or both of a carrier frequency and a DC voltage.

7. A motor control device according to claim 2, characterized in that the processor sets a fixed value, which is a central value of the d-axis output voltage, to zero in the constant output voltage control.

8. A motor control device as described in claim 1, characterized in that the processor performs open-state current control in which, when the inverter and the DC power supply are disconnected, the multiple switching elements are switched so that the motor current becomes a steady-state current in the constant output voltage control.

9. A motor control device according to claim 8, characterized in that, when the inverter and the DC power supply are disconnected, the processor performs transition control to gradually bring the output voltage of the inverter to a value close to zero.

10. An electric vehicle comprising the motor control device according to claim 1, wherein the motor supplies power to the wheels of the electric vehicle.

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