Motor control device and electric vehicle

Abstract

To provide a motor control device and the like that can suppress an overvoltage of an inverter capacitor and current oscillation of a motor when a DC power supply and an inverter are disconnected.SOLUTION: A processor of a motor control device 300 performs normal control in which, while an inverter (a power converter 2) and a DC power supply (a DC voltage source 9) are connected, the processor switches a plurality of switching elements of the inverter to convert a DC current supplied from the DC power supply into an AC current and supplies the AC current to a motor (a PMSM 1). When the inverter and the DC power supply are disconnected (lack of power detection), the processor performs constant output voltage control in which an output voltage of the inverter is fixed to a value close to zero by switching the plurality of switching elements.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In motor drive systems, a switching means is provided to separate the DC power supply from the inverter in order 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 means, the inverter's capacitor may be charged by the regenerative power of the motor and damaged by overvoltage.

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

[0004] In Patent Document 2, the current during three-phase short circuit is controlled before three-phase short circuit, thereby suppressing capacitor overvoltage and current jumps during three-phase short circuit switching. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-47055 [Patent Document 2] Patent No. 6342043 [Patent Document 3] Patent No. 5948266 [Patent Document 4] Patent Publication No. 2021-151003 Summary of the Invention [Problem to be solved by the invention]

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

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

[0008] In view of the above problem, 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. [Means for solving the problem]

[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, a DC current supplied from the DC power supply is converted into an AC current by switching a plurality of switching elements of the inverter and supplied to a motor, and, when the inverter is disconnected from the DC power supply, performs constant output voltage control in which, when the inverter is disconnected from the DC power supply, a plurality of switching elements are switched to fix the output voltage of the inverter to a value close to zero. Effect of the Invention

[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 apparent from the following description of the embodiments. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram showing the overall configuration of a motor control device according to a first embodiment. [Diagram 2] FIG. 2 is a block diagram illustrating an example of a current command value generating unit according to the first embodiment. [Diagram 3] FIG. 2 is a block diagram of an example of an output voltage switching unit according to the first embodiment. [Figure 4] 3 is a flowchart according to the first embodiment. [Diagram 5] 4 is an example of a voltage command value in the first embodiment. [Figure 6] FIG. 11 is a block diagram showing the overall configuration of a motor control device according to a second embodiment. [Figure 7] FIG. 11 is a block diagram of an example of a damping ratio control section 14 according to the second embodiment. [Figure 8] FIG. 11 is an example of a block diagram of an output voltage switching unit 18B according to the second embodiment. [Figure 9A] 13 is an example of a voltage command value in the second embodiment. [Figure 9B] 13 is another example of a voltage command value in the second embodiment. [Figure 10] FIG. 11 is a block diagram showing the overall configuration of a motor control device according to a third embodiment. [Figure 11] FIG. 13 is an example of a block diagram of a damping ratio control section 14B according to the third embodiment. [Figure 12] FIG. 13 is a configuration diagram of an electric vehicle according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 element of the inverter device is an IGBT, the effects of the embodiments of the present invention are not limited to this, and may be a MOSFET or other power semiconductor element.

[0013] Example 1 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 means 6 and a capacitor 8 between it and a DC voltage source 9 (e.g., a battery), and during normal operation, the switching means 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 made up of Hall CTs (Current Transformers) and 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 made up of a resolver and 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, Iqc. A current command value generation unit 12 normally generates dq-axis current command values ​​Id*, Iq* based on a torque command value T* and speed information ω1* using, for example, a lookup 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 with the dq (dq-axis current command values ​​Id*, Iq*), respectively, and outputs the dq-axis voltage command values ​​Vdc*, Vqc*. The output voltage switching unit 18 normally outputs the dq-axis voltage command values ​​Vdc*, Vqc*. Meanwhile, the operation when the opening and closing 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 a pulse by comparing it with, for example, a triangular wave, and generates and outputs a gate signal taking into account the dead time.

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

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

[0021]

number

[0022] Here, Vdcst* and Vqcst* represent the dq-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] Setting as in Equation 1 enables switching between open-circuit current control and constant output voltage control without torque shock or current fluctuation when there is no parameter error. 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 is 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. For example, the predetermined time is set to be five times or more the time constant of the current control, and the on-time delay 31 is turned on when the dq-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 dq-axis voltage command values ​​Vdc* and Vqc* as the dq-axis voltage command values ​​Vd* and Vq*, and when the constant output voltage control flag fcst is on, it outputs the open-circuit dq-axis voltage command values ​​Vdop* and Vqop*.

[0025] The change amount limits 33, 35 for the switching transition period provide a change amount limit to 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 providing a change amount limit, it is possible to suppress the occurrence of current oscillations due to a sudden change in output voltage.

[0026] FIG. 4 shows flowcharts 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 dq-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, it switches to a three-phase short circuit. In the case of a three-phase short circuit, the voltage is fixed at 0V, so that 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 opening control flag fop is turned on and the 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 the constant output voltage control.

[0029] Next, when the output voltage constant 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 becomes constant due to 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 jumps at the time of switching.

[0030] When the dq-axis voltage command values ​​Vdcst* and Vqcst* during constant output voltage control are both set to 0 V, they are 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 the capacitor voltage is allowed to rise.

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

[0032]

number

[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 that 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]

number

[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. It is advisable to set the d-axis voltage command value Vdcst* to prevent this. Note that, rather than setting the d-axis voltage command value Vdcst* to a negative value, the same effect can be obtained by setting the dead time compensation setting amount to over-compensation by the amount of the expected error.

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

[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 continues to be 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 is detected.

[0038] In addition, while heat is concentrated 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*, Vq* into three-phase voltage command values ​​Vu*, Vv*, 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 the resistance component may be ignored and they may be set as shown in Equation 4.

[0041]

number

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

[0043]

number

[0044] In the case of the embodiment of the present invention, since the switching can be performed gradually, even if there is some error, the current can be prevented from jumping and the output voltage can be controlled to be constant.

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

[0046] With the inverter (power converter 2) and DC power supply (DC voltage source 9) connected, the processor of the motor control device 300 performs normal control to convert DC current supplied from the DC power supply to AC current by switching multiple switching elements of the inverter and supplying it to the motor (PMSM 1). When the inverter and the DC power supply are disconnected (detection of a power shortage), the processor performs constant output voltage control to fix the inverter output voltage to a value close to zero by switching 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 in the inverter capacitor and current oscillations in the motor can be suppressed. It is also possible to distribute heat to the upper and lower arms of the inverter.

[0048] The value close to zero (including zero) is set by a formula, an experiment, a 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 output voltage constant 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 output voltage constant 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. As a result, the rise in the inverter capacitor voltage is further suppressed.

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

[0052] In the output voltage constant control, the processor may set a fixed value (d-axis voltage command value Vdcst*) that is a central 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 (power shortage detection), the processor performs open-circuit current control by switching multiple switching elements so that the current of the motor (PMSM1) becomes the steady-state 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 (detection of a power shortage), the processor performs transition control to gradually bring the output voltage of the inverter to a value close to zero (variation limits 33, 35, FIG. 3). This makes it possible to further suppress current oscillation. In the transition control, in addition to the variation limits 33, 34 of the first embodiment, a low-pass filter may be used to gradually bring the output voltage to a value close to zero.

[0055] Example 2 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 described.

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

[0059] The damping ratio control unit 14 is configured as shown in Fig. 7, for example. The q-axis current command value is passed through a first-order delay filter 41 that takes into account the delay of ωc, which is the cutoff frequency by the current control unit 16, and the difference between the q-axis current detection value Iqc is taken. The difference is passed through a high-pass filter 45 to extract the fundamental wave first-order vibration component. Furthermore, the speed ω1* is multiplied by a multiplier 47, and twice the damping ratio ζ and the q-axis inductance Lq are multiplied by 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, Idc is divided by a divider 53, and the result is multiplied by -1 by 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 difference from Fig. 3 is that the change amount limits 33 and 35 are eliminated and 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. During a three-phase short circuit, the voltage converges to a steady 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 allows voltage control, so it is possible to suppress oscillations at the time of switching by suppressing the fundamental primary oscillation component.

[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 in the d-axis direction here, the capacitor voltage would fluctuate greatly due to vibrations in the voltage command value. On the other hand, since the current command value on the q-axis side is nearly zero, the current only has an oscillatory component, and the amount of fluctuation is small. Furthermore, if the d-axis damping ratio control voltage command value Vdd* is given by the following equation 6 so as to cancel out the input power Pqd on the q-axis side, the fluctuations in capacitor voltage due to damping ratio control can be completely suppressed.

[0064]

number

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

[0066] As described above, this embodiment can suppress both the overvoltage and the 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 (d-axis voltage command value Vdop* when open) 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 (q-axis voltage command value Vqop* when open).

[0069] This makes it possible to suppress current oscillations when switching to constant output voltage control without providing a transition period. As shown in Fig. 8, the open dq-axis voltage command values ​​Vdop* and Vqop* are respectively 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* 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 the fluctuation 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] Example 3 The components of the third embodiment will be described.

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

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

[0074] In the third embodiment, the current is controlled using the magnetic flux command value generating unit 13, the magnetic flux estimated 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 by using a lookup table, an approximation 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 performs control using a PI controller so that the dq-axis flux command values ​​φd*, φq* and the dq-axis flux estimation values ​​φdc, φqc match. As described in Patent Document 4, it may be configured with an integrator and an inverse model of the motor.

[0076] The configuration of the damping ratio control unit 14B is shown in Fig. 11. The q-axis magnetic flux command value is passed through a first-order lag filter 61 that takes into account the delay of ωc, which is the cutoff frequency by the magnetic flux control unit 17, and the difference between the q-axis magnetic flux estimated value φqc is taken. The difference is then passed through a high-pass filter 65 to extract the first-order vibration component of the fundamental wave. Furthermore, the result is multiplied by the speed ω1* in a multiplier 67, multiplied by twice the damping ratio ζ in a gain 69, and the q-axis damping ratio control voltage command value Vqd* is output. 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 damping ratio control is magnetic flux, current oscillation can be suppressed when switching to constant output voltage control, similar to the second embodiment.

[0078] Example 4 The components of the fourth embodiment will be described.

[0079] Fig. 12 shows the configuration of an electric vehicle in a fourth embodiment of the present invention. As shown in the first to third embodiments, a 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 transmission is directly connected to the differential gear 303, or a configuration in which the PMSM 1 and the power converter 2 are applied to both the front and rear wheels.

[0080] In the case of automobiles, torque fluctuations are directly linked to the ride comfort, so the requirements for torque fluctuations are stricter than in other applications, and this is an application in which the effects of the embodiments of the present invention are likely to be seen. By applying the present invention, the ride comfort of an automobile can be improved during a power supply abnormality.

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

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

[0083] The present invention is not limited to the above-mentioned embodiment, but includes various modified examples. For example, the above-mentioned embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to those including all of the configurations described. It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0084] In addition, the above configurations, functions, etc. may be realized in hardware, partly or in whole, by designing them as integrated circuits, etc. In addition, the above configurations, functions, etc. may be realized in software by a processor interpreting and executing a program that realizes each function. Information such as the program, table, file, etc. that realizes 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 a number of switching elements, and when the inverter and DC power supply are disconnected due to detection of an abnormality on the power supply side, etc., performs constant output voltage control by switching the switching elements to fix the output voltage of the inverter circuit to a value close to zero.

[0087] (2) The AC motor control device according to (1), wherein the output voltage constant control fixes the q-axis output voltage to zero.

[0088] (3) An AC motor control device as described in (1), characterized in that the attenuation ratio control outputs 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 the q-axis output voltage outputs the q-axis damping ratio control voltage which is the output of the attenuation ratio control.

[0089] (4) In the AC motor control device described in (3), the damping ratio control unit 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 calculating the d-axis output voltage by adding the d-axis damping ratio control voltage to a predetermined value.

[0090] (5) An AC motor control device as described in any one of (2) to (4), characterized in that in the constant output voltage control, a fixed value that is a central value of the d-axis output voltage is a very 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) An AC motor control device as described in any one of (2) to (4), characterized in that the constant output voltage control is such that a fixed value that is a central value of the d-axis output voltage is zero.

[0093] (8) An AC motor control device as described in any one of (1) to (7), further comprising an open-circuit current control for switching the switching element so that the motor current becomes a steady-state current in 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, as a control device for the AC motor, the AC motor control device according to any one of (1) to (9).

[0096] According to (1)-(10), both the capacitor overvoltage and the motor current oscillation can be suppressed, thereby realizing both a reduction in the capacitor capacity and an improvement in ride comfort during a power supply abnormality. [Explanation of symbols]

[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 section 6: Switching means (switch) 7: Coordinate conversion section 8: Capacitor 9: DC voltage source 11: Coordinate conversion section 12: Current command value generator 13: Magnetic flux command value generator 14: Damping ratio control section 14B: Damping ratio control section (Example 3) 15: Magnetic flux estimate generator 16: Current control section 17: Magnetic flux control unit 18: Output voltage switching section 18B: Output voltage switching unit (Example 2) 21: Normal current command value generator 23: Open-circuit dq-axis current command value generator 25: Switch 31: On Time Delay 33: Change limit for switching transition period 35: Change limit for switching transition period 37: Switch 38: Adder 39: Adder 41: First-order delay filter (LPF) 43: Subtractor 45: High pass filter 47: Multiplier 49: Gain 51: Multiplier 53: Divider 55: Gain 61: First-order delay 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 normal control in which, in a state in which an inverter and a DC power source are connected, a plurality of switching elements of the inverter are switched on and off to convert a DC current supplied from the DC power source into an AC current and supply the AC current to a motor; and when the inverter and the DC power supply are disconnected, a constant output voltage control is performed to fix the output voltage of the inverter to a value close to zero by switching on and off a plurality of the switching elements.

2. 2. The motor control device according to claim 1, The processor, In the output voltage constant control, the q-axis output voltage is fixed to zero. A motor control device comprising:

3. 2. The motor control device according to claim 1, The processor, When the inverter and the DC power supply are disconnected, a damping ratio control is performed to output a q-axis damping ratio control voltage so as to cancel an oscillation component of a q-axis current or a magnetic flux. In the constant output voltage control, the d-axis output voltage is fixed to a predetermined value, and a q-axis damping ratio control voltage, which is the output of the damping ratio control, is output as the q-axis output voltage. A motor control device comprising:

4. 4. The motor control device according to claim 3, The processor, In the damping ratio control, a d-axis damping ratio control voltage is output so as to cancel out power due to the q-axis damping ratio control voltage; In the output voltage constant control, the d-axis output voltage is calculated by adding the d-axis damping ratio control voltage to the predetermined value. A motor control device comprising:

5. 3. The motor control device according to claim 2, The processor, In the output voltage constant control, the fixed value that is the center value of the d-axis output voltage is set to a small negative value. A motor control device comprising:

6. 6. The motor control device according to claim 5, The processor, In the constant output voltage control, the fixed value is changed in proportion to either or both of a carrier frequency and a DC voltage. A motor control device comprising:

7. 3. The motor control device according to claim 2, The processor, In the constant output voltage control, a fixed value that is a center value of the d-axis output voltage is set to zero. A motor control device comprising:

8. 2. The motor control device according to claim 1, The processor, When the inverter and the DC power supply are disconnected, an open-time current control is performed by switching the multiple switching elements so that the current of the motor becomes a steady current in the constant output voltage control. A motor control device comprising:

9. 9. The motor control device according to claim 8, The processor, When the inverter and the DC power supply are disconnected, transition control is performed to gradually change the output voltage of the inverter to a value close to zero. A motor control device comprising:

10. An electric vehicle equipped with the motor control device according to claim 1, The motor powers the wheels of the electric vehicle. An electric vehicle characterized by

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