Power converter, program, and control method for power converter

Abstract

To provide a power conversion device capable of reducing a noise generated at temperature rising control of a battery pack.SOLUTION: A power conversion device 10 comprises: a rotary electric machine 40 that has respective phase coils 41U, 41V, and 41W; an inverter 30 that has series connection bodies of upper and lower arm switches QUH, QVH, QWH, QUL, QVL, and QWL; and a capacitor 31 connected in parallel with the series connection bodies. Further, the power conversion device 10 comprises: a connection path 60 electrically connecting between an intermediate terminal B of a battery pack 20 and a neutral point O; and a control device 70 that performs switching control of the inverter 30 so as to apply a current between a first accumulator battery 21 and a second accumulator battery 22 configuring the battery pack 20 via the inverter 30, the phase coils 41U, 41V, and 41W and the connection path 60.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to Power converter, program, and control method for power converter .

Background Art

[0002] As this type of power conversion device, as seen in Patent Document 1, there is known a device that controls the temperature rise of a storage battery by performing reactive power exchange between the storage battery and a capacitor via an inverter. Specifically, when flowing a current from the storage battery to the capacitor, the inverter and winding are used as a boost chopper circuit, and when flowing a current from the capacitor to the storage battery, the inverter and winding are used as a boost chopper circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the power conversion device described in Patent Document 1, since reactive power is exchanged between the storage battery and the capacitor, the terminal voltage of the capacitor fluctuates in proportion to the reactive power. Due to this fluctuation, there is a concern that the terminal voltage of the capacitor exceeds the allowable upper limit value determined from the withstand voltage performance of the capacitor, and the reliability of the capacitor decreases.

[0005] On the other hand, due to the fluctuation of the terminal voltage of the capacitor, the terminal voltage of the capacitor can become excessively low. When flowing a current from the storage battery to the capacitor via the inverter, it is necessary to make the terminal voltage of the capacitor higher than the terminal voltage of the storage battery. Therefore, when the terminal voltage of the capacitor becomes excessively low, there is a concern that the current flowing from the storage battery to the capacitor cannot be controlled to the desired command current.

[0006] To address the problems described above, it is necessary to reduce the fluctuation in the capacitor's terminal voltage. One possible solution to reduce this fluctuation is to increase the capacitor's capacitance. However, this would result in a larger capacitor.

[0007] On the other hand, in order to reduce fluctuations, in addition to increasing the capacitance of the capacitor, another measure that can be considered is to increase the frequency of reactive power (ripple current). However, in this case, noise increases, and the NVH characteristics of the power converter deteriorate.

[0008] This invention relates to a power conversion device that can reduce noise generated during temperature control of a storage battery. , program, and control method for power converter The primary purpose is to provide [this]. [Means for solving the problem]

[0009] The present invention relates to a rotating electric machine having a winding, An inverter having a series connection of an upper arm switch and a lower arm switch, A power conversion device comprising a capacitor connected in parallel to the series connection, A connection path electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the winding in a series-connected first and second battery, The system includes a control unit that controls the switching of the upper arm switch and the lower arm switch so that current flows between the first battery and the second battery via the inverter, the winding, and the connection path.

[0010] The capacity of the battery is significantly larger than that of the capacitor. Therefore, the increase or decrease in terminal voltage with respect to the battery's charge / discharge current is significantly smaller than the increase or decrease in terminal voltage with respect to the capacitor's charge / discharge current. Consequently, if power can be exchanged between batteries rather than between capacitors and batteries, the fluctuation in the capacitor's terminal voltage during temperature rise control can be reduced without increasing the switching frequency of the upper and lower arm switches.

[0011] Therefore, in order to exchange power between the batteries via an inverter, the present invention provides a connection path that electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the windings of a rotating electric machine in the first and second batteries connected in series. The control unit of the present invention controls the switching of the upper arm switch and the lower arm switch so that current flows between the first and second batteries via the inverter, windings, and connection path in order to raise the temperature of the first and second batteries. This makes it possible to reduce the amount of fluctuation in the terminal voltage of the capacitor without increasing the switching frequency of the upper and lower arm switches. Accordingly, according to the present invention as described above, it is possible to reduce the noise generated when controlling the temperature rise of the first and second batteries. [Brief explanation of the drawing]

[0012] [Figure 1] A diagram illustrating the configuration of a power conversion device according to the first embodiment. [Figure 2] A flowchart showing the processing procedure of the control device. [Figure 3] A diagram showing the equivalent circuit. [Figure 4] Functional block diagram of the control unit. [Figure 5] A diagram showing how to set the command current. [Figure 6] A time chart showing the changes in switch control modes, etc. [Figure 7] A diagram showing the simulation results. [Figure 8] A figure showing the simulation results for the comparative example. [Figure 9] A time chart showing the changes in the control mode of the switch according to Modification 1 of the First Embodiment. [Figure 10] A time chart showing the changes in the control mode of the switch according to Modification 1 of the First Embodiment. [Figure 11] A functional block diagram of a control device according to a modified example 2 of the first embodiment. [Figure 12] A time chart showing the hysteresis control mode. [Figure 13]Figure showing the method for correcting the command current according to the second embodiment. [Figure 14] Figure showing the method for correcting the command current. [Figure 15] Flowchart showing the processing procedure of the control device according to the third embodiment. [Figure 16] Configuration diagram of the power conversion device according to the fourth embodiment. [Figure 17] Configuration diagram of the power conversion device according to the fifth embodiment. [Figure 18] Functional block diagram of the control device. [Figure 19] Time chart showing the transition of the control mode of the switch and the like. [Figure 20] Figure showing the simulation result. [Figure 21] Functional block diagram of the control device according to Modification Example 1 of the fifth embodiment. [Figure 22] Time chart showing the transition of the control mode of the switch and the like according to Modification Example 2 of the fifth embodiment. [Figure 23] Configuration diagram of the power conversion device according to the sixth embodiment. [Figure 24] Configuration diagram of the power conversion device according to the seventh embodiment.

Embodiments for Carrying Out the Invention

[0013] <First Embodiment> Hereinafter, a first embodiment in which the power conversion device according to the present invention is embodied will be described with reference to the drawings. In this embodiment, the power conversion device is mounted on a vehicle.

[0014] As shown in FIG. 1, the power conversion device 10 includes an inverter 30 and a rotating electric machine 40. The power conversion device 10 has a function of exchanging power between the battery pack 20 and the rotating electric machine 40 via the inverter 30 in order to raise the temperature of the battery pack 20.

[0015] The rotating electric machine 40 is a three-phase synchronous machine and is equipped with star-connected U, V, and W phase windings 41U, 41V, and 41W as stator windings. Each phase winding 41U, 41V, and 41W is positioned with an electrical angle offset of 120°. The rotating electric machine 40 is, for example, a permanent magnet synchronous machine. In this embodiment, the rotating electric machine 40 is an on-board main machine and serves as the power source for the vehicle's movement.

[0016] The inverter 30 is equipped with three phases of series connections between upper arm switches QUH, QVH, QWH and lower arm switches QUL, QVL, QWL. In this embodiment, voltage-controlled semiconductor switching elements are used as each switch QUH, QVH, QWH, QUL, QVL, QWL, specifically IGBTs. Therefore, the high-potential terminal of each switch QUH, QVH, QWH, QUL, QVL, QWL is the collector, and the low-potential terminal is the emitter. Each switch QUH, QVH, QWH, QUL, QVL, QWL is connected in antiparallel to diodes DUH, DVH, DWH, DUL, DVL, DWL, which act as freewheeling diodes.

[0017] The emitter of the U-phase upper arm switch QUH and the collector of the U-phase lower arm switch QUL are connected via a U-phase conductive member 32U, such as a busbar, to the first end of the U-phase winding 41U. The emitter of the V-phase upper arm switch QVH and the collector of the V-phase lower arm switch QVL are connected via a V-phase conductive member 32V, such as a busbar, to the first end of the V-phase winding 41V. The emitter of the W-phase upper arm switch QWH and the collector of the W-phase lower arm switch QWL are connected via a W-phase conductive member 32W, such as a busbar, to the first end of the W-phase winding 41W. The second ends of the U, V, and W-phase windings 41U, 41V, and 41W are connected at the neutral point O. In this embodiment, the number of turns for each phase winding 41U, 41V, and 41W is set to be the same. As a result, the inductance of each phase winding 41U, 41V, and 41W is set to be the same, for example.

[0018] The collectors of each upper arm switch QUH, QVH, and QWH are connected to the positive terminal of the battery pack 20 by a positive busbar Lp. The emitters of each lower arm switch QUL, QVL, and QWL are connected to the negative terminal of the battery pack 20 by a negative busbar Ln.

[0019] The power converter 10 includes a capacitor 31 that connects the positive busbar Lp and the negative busbar Ln. The capacitor 31 may be built into the inverter 30 or provided outside the inverter 30.

[0020] The battery pack 20 is configured as a series connection of individual battery cells, with a terminal voltage of, for example, several hundred volts. In this embodiment, the terminal voltages (e.g., rated voltages) of each battery cell constituting the battery pack 20 are set to be the same. As the battery cells, for example, secondary batteries such as lithium-ion batteries can be used.

[0021] In this embodiment, among the battery cells constituting the battery pack 20, a series connection of multiple high-potential battery cells constitutes the first storage battery 21, and a series connection of multiple low-potential battery cells constitutes the second storage battery 22. In other words, the battery pack 20 is divided into two blocks. In this embodiment, the number of battery cells constituting the first storage battery 21 is the same as the number of battery cells constituting the second storage battery 22. Therefore, the terminal voltage (e.g., rated voltage) of the first storage battery 21 is the same as the terminal voltage (e.g., rated voltage) of the second storage battery 22.

[0022] In the battery pack 20, an intermediate terminal B is connected to the negative terminal of the first battery 21 and the positive terminal of the second battery 22.

[0023] The power converter 10 is equipped with a monitoring unit 50 (corresponding to a voltage information detection unit). The monitoring unit 50 monitors the terminal voltage, state of charge (SOC), state of heat (SOH), temperature, etc., of each battery cell constituting the battery pack 20.

[0024] The power converter 10 includes a connection path 60 and a connection switch 61. The connection path 60 electrically connects the intermediate terminal B of the battery pack 20 to the neutral point O. The connection switch 61 is provided on the connection path 60. In this embodiment, a relay is used as the connection switch 61. When the connection switch 61 is turned ON, the intermediate terminal B and the neutral point O are electrically connected. On the other hand, when the connection switch 61 is turned OFF, the connection between the intermediate terminal B and the neutral point O is electrically interrupted.

[0025] The power converter 10 is equipped with a current sensor 62 that detects the current flowing through the connection path 60. The value detected by the current sensor 62 is input to the control device 70 (corresponding to the control unit) of the power converter 10.

[0026] The control device 70 is mainly composed of a microcontroller and controls the switching of each switch that makes up the inverter 30 in order to feed back the controlled amount of the rotating electric machine 40 to its command value. The controlled amount is, for example, torque.

[0027] The control device 70 controls the connection switch 61 by switching it on and off, and is also capable of communicating with the monitoring unit 50. Furthermore, the control device 70 is capable of communicating with a higher-level control device 80 located outside the power converter 10. The higher-level control device 80 oversees the control of the vehicle.

[0028] Incidentally, the control device 70 implements various control functions by executing a program stored in its own memory device. These various functions may be implemented by hardware electronic circuits, or by both hardware and software.

[0029] Next, the temperature rise control of the battery pack 20, performed by the control device 70, will be described. Figure 2 is a flowchart showing the procedure for the temperature rise control process. This process is repeatedly performed by the control device 70, for example, at a predetermined control cycle.

[0030] In step S10, it is determined whether or not there is a request to raise the temperature of the battery pack 20. For example, if it is determined that there is a request to raise the temperature of the battery pack 20 from the higher-level control device 80, or if it is determined that the temperature of the battery pack 20 detected by the monitoring unit 50 is below the threshold temperature, it is determined that there is a request to raise the temperature. Here, the temperature to be compared with the threshold temperature may be, for example, the lowest temperature among the detected temperatures of each battery cell, or the average temperature of each battery cell calculated based on the detected temperatures of each battery cell.

[0031] In this embodiment, the situation that is determined to be positive in step S10 is assumed to be the situation when the vehicle is stationary before the rotating electric machine 40 is driven.

[0032] If it is determined in step S10 that there is no request for heating, the process proceeds to step S11 to determine whether or not there is a request to drive the rotating electric machine 40. In this embodiment, this drive request includes a request to drive the vehicle by rotating the electric machine 40.

[0033] If it is determined in step S11 that there is no drive request, the process proceeds to step S12, and the system is set to standby mode. By setting this mode, switches QUH to QWL of the inverter 30 are turned off. Then, in step S13, the connection switch 61 is turned off. This electrically disconnects the intermediate terminal B and the neutral point O.

[0034] If a drive request is determined in step S11, the process proceeds to step S14, where the rotating electric machine 40 is set to drive mode. Then, in step S16, the connection switch 61 is turned ON. This electrically connects the intermediate terminal B and the neutral point O via the connection path 60. Subsequently, in step S16, the switching control of switches QUH to QWL of the inverter 30 is performed to rotate the rotating electric machine 40. This causes the drive wheels of the vehicle to rotate, allowing the vehicle to move. The switching control in step S16 can be performed, for example, using PWM based on a comparison of the magnitudes of the command voltage applied to each phase winding 41U to 41W and the carrier signal (e.g., a triangular wave signal), or using a pulse pattern.

[0035] If it is determined in step S10 that there is a request for temperature increase, the process proceeds to step S17, and the system is set to temperature increase control mode. In step S18, the connection switch 61 is turned ON.

[0036] In step S19, temperature-boosting PWM control is performed to raise the temperature of the battery pack 20. This control is described below.

[0037] Figure 3(a) shows the equivalent circuit of the power converter 10 used in temperature rise PWM control. In Figure 3(a), each phase winding 41U to 41W is shown as winding 41, each upper arm switch QUH, QVH, QWH is shown as upper arm switch QH, and each upper arm diode DUH, DVH, DWH is shown as upper arm diode DH. In addition, each lower arm switch QUL, QVL, QWL is shown as lower arm switch QL, and each lower arm diode DUL, DVL, DWL is shown as lower arm diode DL.

[0038] The equivalent circuit of Figure 3(a) can be shown as the equivalent circuit of Figure 3(b). The circuit in Figure 3(b) is a step-up / step-down chopper circuit capable of bidirectional power transfer between the first battery 21 and the second battery 22. In Figure 3(b), VBH represents the terminal voltage of the first battery 21, IBH represents the current flowing through the first battery 21, VBL represents the terminal voltage of the second battery 22, and IBL represents the current flowing through the second battery 22. When charging current flows through the first and second batteries 21 and 22, IBH and IBL are negative, and when discharge current flows through the first and second batteries 21 and 22, IBH and IBL are positive. Also, VR represents the terminal voltage of winding 41, and IR represents the current flowing through the neutral point O. When current flows from winding 41 to the intermediate terminal B in the positive direction to the neutral point O, IR is negative, and when current flows in the opposite direction to the neutral point O, IR is positive.

[0039] Referring to Figure 3(b), when the upper arm switch QH is turned ON, the terminal voltage VR of winding 41 becomes "VBH". On the other hand, when the lower arm switch QL is turned ON, the terminal voltage VR of winding 41 becomes "-VBL". In other words, when the upper arm switch QH is turned ON, an excitation current can be passed through winding 41 in the positive direction, and when the lower arm switch QL is turned ON, an excitation current can be passed through winding 41 in the negative direction.

[0040] Figure 4 shows a block diagram of the temperature rise PWM control.

[0041] In the control device 70, the current deviation calculation unit 71 calculates the current deviation by subtracting the current detected by the current sensor 62 (hereinafter referred to as the detected current IMr) from the command current IM*. In this embodiment, the command current IM* is set as a sine wave, as shown in Figure 5. Specifically, in one period Tc of the command current IM*, the command current IM* is set so that the positive command current IM* and the negative command current IM* are point-symmetric with respect to the zero-cross timing of the command current IM*. As a result, the period from the zero-up cross timing to the zero-down cross timing of the command current IM* is the same as the period from the zero-down cross timing to the zero-up cross timing of the command current IM*. Also, in one period Tc of the command current IM*, the area S1 of the first region and the area S2 of the second region are equal. The first region S1 is the region enclosed by the time axis from the zero-up cross timing to the zero-down cross timing of the command current IM* and the positive command current IM* in one period Tc of the command current IM*. The second region is the area enclosed by the time axis from the zero-down cross timing to the zero-up cross timing of the command current IM* in one cycle Tc, and the negative command current IM*. By setting "S1=S2", the balance of charge and discharge currents of the first battery 21 and the second battery 22 in one cycle Tc can be matched, and the large difference between the terminal voltage of the first battery 21 and the terminal voltage of the second battery 22 that occurs with temperature rise control can be suppressed.

[0042] Furthermore, the frequency fc of the command current IM*, which is the reciprocal of the period Tc of the command current IM*, should preferably be set to a frequency at the lower limit of the human audible range. Specifically, the frequency fc should preferably be set to 1 kHz or less, which is the frequency range in which the correction value (dB) in A-weighting becomes 0 or less, and more preferably to a frequency between 30 Hz and 100 Hz (for example, 50 Hz).

[0043] The feedback control unit 72 calculates the duty cycle Duty as an manipulated variable for feedback control to reduce the calculated current deviation to zero. The duty cycle Duty is a value that defines the ratio (Ton / Tsw) of the on-time Ton in one switching period Tsw for each switch QUH to QWL. The feedback control used in the feedback control unit 72 may be, for example, proportional-integral control.

[0044] The PWM generation unit 73 generates gate signals for each upper arm switch QUH, QVH, and QWH based on the calculated duty cycle. The gate signals are signals that instruct ON control or OFF control. In this embodiment, the gate signals for each upper arm switch QUH, QVH, and QWH are synchronized.

[0045] The inverter 74 generates the gate signals for each lower arm switch QUL, QVL, and QWL by inverting the logic of the gate signals for each upper arm switch QUH, QVH, and QWH generated by the PWM generation unit 73. In this embodiment, the gate signals for each lower arm switch QUL, QVL, and QWL are synchronized.

[0046] Figure 6 shows the transitions of switching patterns, etc., during temperature rise PWM control. Figure 6(a) shows the transitions of the gate signals of each upper arm switch QUH, QVH, and QWH, and Figure 6(b) shows the transitions of the gate signals of each lower arm switch QUL, QVL, and QWL. Figure 6(c) shows the transitions of the current IR flowing through the neutral point O and the command current IM*. Figure 6(d) shows the transitions of the current IBH flowing through the first battery 21, and Figure 6(e) shows the transitions of the current IBL flowing through the second battery 22.

[0047] As shown in Figures 6(a) and (b), temperature rise PWM control is performed by alternately turning on the upper arm switches QUH, QVH, QWH and the lower arm switches QUL, QVL, QWL. This control continues until the temperature rise request in step S10 of Figure 2 is no longer needed. As a result of this control, pulsed current flows through the first battery 21 and the second battery 22, as shown in Figures 6(d) and (e). During periods when the command current IM* is positive, the first battery 21 is discharged and the second battery 22 is charged. On the other hand, during periods when the command current IM* is negative, the second battery 22 is discharged and the first battery 21 is charged. The average values ​​of the pulsed currents, IBHave and IBLave, are sinusoidal currents that include a component with the same frequency as the command current IM*.

[0048] Figure 7 shows the simulation results of this embodiment. Figures 7(a) to 7(c) correspond to Figures 6(c) to 6(e), and Figure 7(d) shows the change in the terminal voltage of capacitor 31. As shown in Figure 7(d), the terminal voltage of capacitor 31 does not fluctuate.

[0049] Figure 8 shows the simulation results of a comparative example with the configuration described in Patent Document 1. Figures 8(a) and 8(b) correspond to Figures 7(a) and 7(d) above. Note that SK shown in Figures 8(b) and 7(d) is a symbol indicating the time axis scale.

[0050] As shown in Figure 8(b), in the comparative example, the capacitor terminal voltage fluctuates significantly with the same period as the current IR flowing through the neutral point O. To reduce this fluctuation, it is necessary to either increase the capacitance of the capacitor or decrease the amplitude of the command current IM*, i.e., the heating capability.

[0051] According to the embodiment described in detail above, the following effects can be obtained.

[0052] Intermediate terminal B and neutral point O are connected by a connection path 60 without going through the switches QUH to QWL of the inverter 30. In this configuration, the control device 70 controls the switching of the inverter 30 so that ripple current flows between the first battery 21 and the second battery 22 via the inverter 30, the phase windings 41U, 41V, 41W, and the connection path 60. This reduces the fluctuation amount of the terminal voltage of the capacitor 31 without increasing the frequency fc (=1 / Tc) of the reactive power (ripple current). Therefore, the noise generated when controlling the temperature rise of the battery pack 20 can be reduced.

[0053] Furthermore, since the fluctuation in the terminal voltage of capacitor 31 can be reduced, the capacitance of capacitor 31 can be reduced, and the capacitor 31 can be made smaller.

[0054] The control device 70 synchronizes the switching control of all phase upper arm switches QUH, QVH, and QWH, and also synchronizes the switching control of all phase lower arm switches QUL, QVL, and QWL, during temperature rise control. As a result, each phase winding 41U, 41V, and 41W can be considered as an equivalent circuit with the windings connected in parallel. Therefore, the inductance of the windings can be reduced during temperature rise control. This allows for a large change in the current flowing through the neutral point O in one switching period Tsw, enabling temperature rise control using a large current.

[0055] Furthermore, by synchronizing the switching control, it is possible to suppress the rotational drive of the rotor of the rotating electric machine 40.

[0056] The control device 70 turns on the connection switch 61 when it determines that there is a request for the battery pack 20 to raise its temperature, and turns off the connection switch 61 when it determines that there is no request for the temperature to rise. This suppresses the flow of current from the neutral point O to the intermediate terminal B when the vehicle is running.

[0057] <Modification 1 of the first embodiment> As shown in Figure 9, temperature rise PWM control may be performed by controlling the on / off state of two of the three phases. Figure 9 shows an example in which the W-phase upper and lower arm switches QWH and QWL are kept in the off state. Figure 9(a) shows the transition of the gate signals of the U and V-phase upper arm switches QUH and QVH, Figure 9(b) shows the transition of the gate signals of the U and V-phase lower arm switches QUL and QVL, Figure 9(c) shows the transition of the gate signals of the W-phase upper and lower arm switches QWH and QWL, and Figures 9(d) to (f) correspond to Figures 6(c) to (e) above.

[0058] Alternatively, as shown in Figure 10, temperature rise PWM control may be performed by controlling the on / off state of one of the three phases. Figure 10 shows an example in which only the U-phase upper and lower arm switches QUH and QUL are controlled on / off. Figures 10(a) and (b) show the transition of the gate signals of the U-phase upper arm switches QUH and QUL, Figure 10(c) shows the transition of the gate signals of the V-phase upper and lower arm switches QVH and QVL and the W-phase upper and lower arm switches QWH and QWL, and Figures 10(d) to (f) correspond to Figures 9(d) to (f) above.

[0059] Even with the switching control shown in Figures 9 and 10, if the ripple current is small, increasing the equivalent inductance of winding 41 can reduce current ripple, which may reduce iron loss compared to performing switching control of all phases.

[0060] <Modification 2 of the first embodiment> Instead of the configuration in Figure 4, switching control may be performed using the configuration shown in Figure 11. In the control device 70, the hysteresis control unit 75 generates gate signals for each upper arm switch QUH, QVH, and QWH shown in Figure 12(b) based on the command current IM* and the detected current IMr. More specifically, the hysteresis control unit 75 generates gate signals for each upper arm switch QUH, QVH, and QWH based on the current deviation between the command current IM* and the detected current IMr. The inverter 74 generates gate signals for each lower arm switch QUL, QVL, and QWL shown in Figure 12(c) by inverting the logic of the gate signals for each upper arm switch QUH, QVH, and QWH generated by the hysteresis control unit 75. As a result, as shown in Figure 12(a), the detected current IMr is controlled within a range with a width of ±ΔI relative to the command current IM*.

[0061] <Second Embodiment> The second embodiment will be described below, focusing on the differences from the first embodiment, with reference to the drawings.

[0062] In this embodiment, the control device 70 corrects the command current IM* so that the terminal voltages of the first battery 21 and the second battery 22 are equalized. Specifically, the control device 70 calculates the terminal voltage VHr of the first battery 21 and the terminal voltage VLr of the second battery 22 based on the information transmitted from the monitoring unit 50. Then, if the control device 70 determines that the terminal voltage VHr of the first battery 21 is higher than the terminal voltage VLr of the second battery 22, it calculates the corrected command current by adding the DC component Idc (>0) to the command current IM*, as shown in Figure 13. As a result, in the corrected command current for one cycle Tc, the area S1 of the first region becomes larger than the area S2 of the second region. Consequently, in one cycle Tc, the discharge current of the first battery 21 exceeds the discharge current of the second battery 22, and the terminal voltages of the first battery 21 and the second battery 22 are equalized.

[0063] On the other hand, if the control device 70 determines that the terminal voltage VHr of the first battery 21 is lower than the terminal voltage VLr of the second battery 22, it calculates a corrected command current by subtracting the DC component Idc from the command current IM*, as shown in Figure 14. As a result, in the corrected command current for one cycle Tc, the area S1 of the first region becomes smaller than the area S2 of the second region. Consequently, in one cycle Tc, the discharge current of the second battery 22 exceeds the discharge current of the first battery 21, and the terminal voltages of the first battery 21 and the second battery 22 are equalized.

[0064] According to the embodiment described above, it is possible to equalize the terminal voltage of the first battery 21 and the terminal voltage of the second battery 22 while performing temperature rise control.

[0065] <Modified form of the second embodiment> The DC component Idc may be variably set based on the voltage difference between the terminal voltage VHr of the first battery 21 and the terminal voltage VLr of the second battery 22. Specifically, for example, when the terminal voltage VHr of the first battery 21 is higher than the terminal voltage VLr of the second battery 22, the larger "VHr-VLr" is, the larger the DC component Idc may be set. Also, when the terminal voltage VHr of the first battery 21 is lower than the terminal voltage VLr of the second battery 22, the larger "VLr-VHr" is, the larger the DC component Idc may be set.

[0066] In the correction process for the command current IM*, instead of the terminal voltage of each battery, for example, the lowest terminal voltage among the battery cells constituting each battery, or the average value of the terminal voltages of the battery cells constituting each battery, may be used.

[0067] <Third Embodiment> The third embodiment will now be described, focusing on the differences from the first embodiment, with reference to the drawings. In this embodiment, the control device 70 sets the switching frequency fsw (=1 / Tsw) when the rotation of the electric motor 40 is stopped to a frequency that is higher than the switching frequency of the upper and lower arm switches QUH~QWL when the electric motor 40 is rotating and the vehicle is moving, and is also within the range of human hearing.

[0068] Figure 15 shows the procedure for the temperature rise control process according to this embodiment. This process is repeatedly executed by the control device 70, for example, at a predetermined control cycle. In Figure 15, the same reference numerals are used for the same processes as those shown in Figure 2 for convenience.

[0069] After the completion of step S18, the process proceeds to step S20, where temperature rise PWM control is performed. Here, the switching frequency fsw of each switch QUH to QWL is set higher than the switching frequency set in step S16. Specifically, the switching frequency fsw is set to a frequency of 16kHz or higher, for example, to a frequency in the inaudible range for humans (20kHz or higher).

[0070] The temperature rise control is performed while the vehicle is stopped. In this situation, human hearing sensitivity to noise associated with the switching control of the inverter 30 is high. Therefore, by setting the switching frequency fsw to a frequency of 16kHz or higher that is difficult for humans to hear but is not in the inaudible range, or a frequency in the inaudible range, the NVH characteristics of the power converter 10 during temperature rise control can be improved. However, since frequencies of 16kHz or higher are excessively high, there is a concern about heat generation in each switch QUH to QWL due to switching losses. However, during temperature rise control, the environment around the vehicle is low temperature, so there is little risk of the temperature of each switch QUH to QWL exceeding its permissible upper limit.

[0071] <Fourth Embodiment> In the first embodiment, the rotating electric machine and inverter may be 5-phase or 7-phase, or other types besides 3-phase. Figure 16 shows a power conversion device in the case of 5-phase. In Figure 16, components identical to those shown in Figure 1 are denoted by the same reference numerals for convenience.

[0072] In Figure 16, the inverter 30 has been modified by adding X-phase upper and lower arm switches QXH and QXL and diodes DXH and DXL, as well as Y-phase upper and lower arm switches QYH and QYL and diodes DYH and DYL. In addition, the rotating electric machine 40 has been modified by adding X-phase winding 41X and Y-phase winding 41Y. Furthermore, the power converter 10 has been modified by adding X-phase conductive member 32X and Y-phase conductive member 32Y.

[0073] <Fifth Embodiment> The fifth embodiment will be described below, focusing on the differences from the first embodiment, with reference to the drawings.

[0074] Figure 17 shows a diagram of the power converter in this embodiment. In Figure 17, components identical to those shown in Figure 1 are denoted by the same reference numerals for convenience.

[0075] In the configuration of the first embodiment shown in Figure 1, the power converter 10 was equipped with a connection path 60, a connection switch 61, and a current sensor 62. Instead of these components, in this embodiment, the power converter 10 is equipped with a connection path 90, a connection switch 91, and a current sensor 92. The emitter of the U-phase upper arm switch QUH and the collector of the U-phase lower arm switch QUL are connected to the intermediate terminal B of the battery pack 20 via the connection path 90. The connection switch 91 and the current sensor 92 are provided on the connection path 90.

[0076] In this embodiment as well, the control device 70 executes the temperature rise control process according to the procedure shown in Figure 2. Here, the connection switch 61 in steps S13, S15, and S18 is replaced with the connection switch 91. The equivalent circuit of the power converter 10 used in the temperature rise PWM control of this embodiment is the same as the circuit shown in Figure 3. In addition, in the temperature rise control process of this embodiment, the switching control method in the temperature rise PWM control in step S19 has been changed. This control will be described below.

[0077] Figure 18 shows a block diagram of the temperature rise PWM control in this embodiment. Note that the configuration of the current deviation calculation unit 71 and the feedback control unit 72, and the method for setting the command current IM* in Figure 18 are the same as in the first embodiment, so their explanation is omitted.

[0078] The PWM generation unit 73 generates gate signals for the V and W phase upper arm switches QVH and QWH based on the duty cycle calculated by the feedback control unit 72. The inverter 74 generates gate signals for the V and W phase lower arm switches QVL and QWL by inverting the logic of the gate signals for the V and W phase upper arm switches QVH and QWH. In this embodiment, the U phase upper and lower arm switches QUH and QUL are controlled to be off. Furthermore, the switching control of the V and W phase upper arm switches QVH and QWH is synchronized, and the switching control of the V and W phase lower arm switches QVL and QWL is also synchronized.

[0079] Figure 19 shows the changes in current IR and other parameters in this embodiment. Figure 19(a) shows the changes in current IR flowing through the connection path 90, Figure 19(b) shows the changes in current IBH flowing through the first battery 21, and Figure 19(c) shows the changes in current IBL flowing through the second battery 22. Figure 19(d) shows the changes in the gate signals of the U-phase upper and lower arm switches QUH and QUL, Figure 19(e) shows the changes in the gate signals of the V and W-phase upper arm switches QVH and QWH, and Figure 19(d) shows the changes in the gate signals of the V and W-phase lower arm switches QVL and QWL.

[0080] In this embodiment, as shown in Figure 19(d), the U-phase upper and lower arm switches QUH and QUL are controlled to be OFF. Also, as shown in Figures 19(e) and (f), the V and W-phase upper arm switches QVH and QWH and the V and W-phase lower arm switches QVL and QWL are alternately controlled to be ON. Due to this control, as shown in Figures 19(b) and (c), pulsed current flows through the first battery 21 and the second battery 22, and as shown in Figure 19(a), the current IR is controlled to the command current IM*.

[0081] Figure 20 shows the simulation results of this embodiment. Figures 20(a) to (c) correspond to Figures 19(a) to (c) above, and Figure 20(d) shows the change in the terminal voltage of capacitor 31. As shown in Figure 20(d), the terminal voltage of capacitor 31 does not fluctuate. SK shown in Figure 20(d) is a symbol indicating the time axis scale and corresponds to SK shown in Figure 8(b) above.

[0082] According to the embodiment described in detail above, the following effects can be obtained.

[0083] The intermediate terminal B of the battery pack 20 is connected via the connection path 90 to the emitter of the U-phase upper arm switch QUH and the collector of the U-phase lower arm switch QUL. In this configuration, the control device 70 controls the switching of each switch QUH to QWL so that ripple current flows between the first battery 21 and the second battery 22 via the V and W-phase upper and lower arm switches QVH, QWH, QVL, QWL, the respective phase windings 41U, 41V, 41W, and the connection path 90. This makes it possible to obtain the same effects as in the first embodiment.

[0084] The control device 70 synchronizes the switching control of the V and W phase upper arm switches QVH and QWH, and also synchronizes the switching control of the V and W phase lower arm switches QVL and QWL during temperature rise control. As a result, the V and W phase windings 41V and 41W can be considered as an equivalent circuit with the windings connected in parallel. Therefore, the inductance of the windings can be reduced during temperature rise control.

[0085] <Modification 1 of the 5th embodiment> Instead of the configuration shown in Figure 18, switching control may be performed using the configuration shown in Figure 21. In the control device 70, the hysteresis control unit 75 generates gate signals for the V and W phase upper arm switches QVH and QWH based on the command current IM* and the detected current IMr. The inverter 74 generates gate signals for the V and W phase lower arm switches QVL and QWL by inverting the logic of the gate signals for the V and W phase upper arm switches QVH and QWH generated by the hysteresis control unit 75.

[0086] <Modification 2 of the 5th embodiment> The control device 70 may perform temperature rise PWM control that controls only one phase on and off. Figure 22 shows an example in which the W-phase upper and lower arm switches QWH and QWL are controlled on and off. Figures 22(a) to (c) correspond to Figures 19(a) to (c) above. Figure 22(d) shows the transition of the gate signals of the U and V-phase upper and lower arm switches QUH, QUL, QVH, and QVL, Figure 22(e) shows the transition of the gate signal of the W-phase upper arm switch QWH, and Figure 22(f) shows the transition of the gate signal of the W-phase lower arm switch QWL.

[0087] In this embodiment, as shown in Figure 22(d), the U and V phase upper and lower arm switches QUH, QUL, QVH, and QVL are turned off. Also, as shown in Figures 22(e) and (f), the W phase upper arm switch QWH and the W phase lower arm switch QWL are alternately turned on.

[0088] According to the switching control shown in Figure 22, when the ripple current is small, the equivalent inductance of winding 41 is increased to reduce the current ripple, thereby reducing iron loss compared to performing switching control of the V and W phases.

[0089] <Modification 3 of the 5th embodiment> The control device 70 may perform temperature rise control according to the procedure shown in Figure 15. In this case, after completing the process in step S18 of Figure 15, the control device 70 proceeds to step S20 and performs temperature rise PWM control. In this embodiment, the switching frequency fsw of the V and W phase upper and lower arm switches QVH, QWH, QVL, and QWL is set higher than the switching frequency set in the process of step S16. This makes it possible to obtain the same effect as in the third embodiment.

[0090] <Modification 4 of the 5th embodiment> As described in the second embodiment, the control device 70 may correct the command current IM* so that the terminal voltage of the first battery 21 and the terminal voltage of the second battery 22 are equalized. This will provide the same effects as in the second embodiment.

[0091] <Modification 5 of the fifth embodiment> The upper and lower arm switches connected to the intermediate terminal B of the battery pack 20 are not limited to U-phase upper and lower arm switches QUH and QUL, but may also be V-phase upper and lower arm switches QVH and QVL. In this case, during temperature rise control, the V-phase upper and lower arm switches QVH and QVL are turned off. In addition, the U and W-phase upper arm switches QUH and QWH and the U and W-phase lower arm switches QUL and QWL are alternately turned on.

[0092] Furthermore, the upper and lower arm switches connected to intermediate terminal B may be, for example, W-phase upper and lower arm switches QWH and QWL. In this case, during temperature rise control, the W-phase upper and lower arm switches QWH and QWL are controlled to be OFF. Also, the U and V-phase upper arm switches QUH and QVH and the U and V-phase lower arm switches QUL and QVL are controlled to be ON alternately.

[0093] <Sixth Embodiment> The sixth embodiment will now be described, focusing on the differences from the fifth embodiment, with reference to the drawings. In this embodiment, the upper and lower arm switches connected to the intermediate terminal B of the battery pack 20 are not limited to one phase. It is sufficient that the intermediate terminal B is not connected to the upper and lower arm switches of all U, V, and W phases.

[0094] Figure 23 shows the configuration diagram of a power converter when the intermediate terminal B of the battery pack 20 is connected to the U-phase upper and lower arm switches QUH and QUL and the W-phase upper and lower arm switches QWH and QWL. In this embodiment, the intermediate terminal B of the battery pack 20 is connected to the emitter of the U-phase upper arm switch QUH and the collector of the U-phase lower arm switch QUL via the U-phase connection path 90U. In addition, the intermediate terminal B of the battery pack 20 is connected to the emitter of the W-phase upper arm switch QWH and the collector of the W-phase lower arm switch QWL via the W-phase connection path 90W.

[0095] In this embodiment, when temperature rise PWM control is performed, the U and W phase upper and lower arm switches QUH, QUL, QWH, and QWL are controlled to be OFF. In addition, the V phase upper arm switch QVH and the V phase lower arm switch QVL are controlled to be ON alternately.

[0096] According to the embodiment described above, the same effects as those of the fifth embodiment can be obtained.

[0097] <Seventh Embodiment> In the fifth embodiment, the rotating electric machine and inverter may be 5-phase or 7-phase, or other types besides 3-phase, as described in the fourth embodiment. Figure 24 shows a power conversion device in the case of 5-phase. In Figure 24, components identical to those shown in Figure 17 are denoted by the same reference numerals for convenience.

[0098] <Other Embodiments> Furthermore, each of the above embodiments may be implemented with the following modifications.

[0099] The installation location of the current sensor that detects the current flowing through the neutral point O is not limited to those exemplified in Figure 1. For example, current sensors may be provided on each of the conductive members 32U, 32V, and 32W in Figure 1. In this case, during temperature rise control, the sum of the currents detected by the current sensors on each of the conductive members 32U, 32V, and 32W should be used as the detected current IMr.

[0100] The method for setting the command current IM* is not limited to that shown in Figure 5. While satisfying the point-symmetric relationship between the positive command current IM* and the negative command current IM* with respect to the zero-crossing timing of the command current IM* in one period Tc, the positive command current IM* and the negative command current IM* may each be set to a trapezoidal wave or a square wave, for example.

[0101] Furthermore, the method for setting the command current IM* is not limited to satisfying the point-symmetry relationship described above. For example, in one cycle Tc, the command current IM* may be set such that the period from the zero-up cross timing to the zero-down cross timing of the command current IM* is different from the period from the zero-down cross timing to the zero-up cross timing of the command current IM*, and the area S1 of the first region and the area S2 of the second region are equal. Even in this case, it is possible to balance the charge and discharge currents of the first battery 21 and the second battery 22 in one cycle Tc.

[0102] The number of battery cells in the first battery 21 and the second battery 22 may be different. In this case, the terminal voltage of the first battery 21 and the terminal voltage of the second battery 22 will be different, and the intermediate terminal B will be located in a position that does not equally divide each battery cell constituting the battery pack 20.

[0103] In the first embodiment, the control device 70 does not need to synchronize the switching control of all phase upper arm switches QUH, QVH, QWH in temperature rise control, nor does it need to synchronize the switching control of all phase lower arm switches QUL, QVL, QWL.

[0104] The connection switch 61 is not limited to a relay. For example, a pair of N-channel MOSFETs with their sources connected or an IGBT may be used as the connection switch 61.

[0105] In the first to fourth embodiments, the connection switch 61 is not essential. In this case, the intermediate terminal B and the neutral point O are always electrically connected.

[0106] The upper and lower arm switches that make up the inverter are not limited to IGBTs; for example, an N-channel MOSFET may also be used. In this case, the high-potential terminal becomes the drain, and the low-potential terminal becomes the source.

[0107] The first and second batteries do not necessarily have to constitute a battery pack.

[0108] The control unit and its method described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control unit and its method described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the control unit and its method described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium. [Explanation of symbols]

[0109] 10...Power converter, 20...Battery pack, 30...Inverter, 31...Capacitor, 40...Rotating electric machine, 41U, 41V, 41W...U, V, W phase windings, 60, 90...Connection path, 61...Connection switch, 90U...U phase connection path, 90W...W phase connection path, 70...Control device, QUH, QVH, QWH...U, V, W phase upper arm switch, QUL, QVL, QWL...U, V, W phase lower arm switch.

Claims

1. A multiphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y), A multiphase inverter (30) having a series connection of upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL), In each phase, a conductive member (32U, 32V, 32W) connects the low-potential terminal of the upper arm switch and the high-potential terminal of the lower arm switch to the first end of the winding, A current sensor for detecting the current flowing through each of the aforementioned conductive members, A capacitor (31) connected in parallel to the series connection, In a first battery (21) and a second battery (22) connected in series, a connection path (60) electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point (O) that connects the second ends of the windings of each phase, The system includes a control unit (70) that controls the switching of the upper arm switch and the lower arm switch so that current flows between the first battery and the second battery via the inverter, winding, and connection path, The control unit performs the switching control based on the detected current, which is the sum of the currents flowing through each of the conductive members detected by the current sensor, and the command value of the current to flow through the connection path, in the power converter (10).

2. A multiphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y), A multiphase inverter (30) having a series connection of upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL), In each phase, a conductive member (32U, 32V, 32W) connects the low-potential terminal of the upper arm switch and the high-potential terminal of the lower arm switch to the first end of the winding, A current sensor for detecting the current flowing through each of the aforementioned conductive members, A capacitor (31) connected in parallel to the series connection, In a first battery (21) and a second battery (22) connected in series, a connection path (60) electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point (O) that connects the second ends of the windings of each phase, The system includes a control unit (70) that controls the switching of the upper arm switch and the lower arm switch so that current flows between the first battery and the second battery via the inverter, winding, and connection path, The control unit sets the command value for the current to flow through the connection path such that the area of ​​a region defined by a positive command value and the area of ​​a region defined by a negative command value appear, and performs the switching control to control the current flowing through the connection path to the set command value, power converter (10).

3. The power conversion device according to claim 2, wherein the control unit sets the command value such that, in one cycle of the command value, the area of ​​the region defined by the positive command value is equal to the area of ​​the region defined by the negative command value.

4. The power conversion device according to any one of claims 1 to 3, wherein the control unit sets the command value such that the positive command value and the negative command value are point-symmetric with respect to the zero-crossing timing of the command value in one cycle of the command value.

5. The system includes a voltage information detection unit (50) for detecting voltage information of the first and second batteries, The power conversion device according to any one of claims 1 to 4, wherein the control unit corrects the command value based on the detected voltage information so that the terminal voltage of the first battery and the terminal voltage of the second battery are equalized.

6. A multiphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y), A multiphase inverter (30) having a series connection of upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL), In each phase, a conductive member (32U, 32V, 32W) connects the low-potential terminal of the upper arm switch and the high-potential terminal of the lower arm switch to the first end of the winding, A current sensor for detecting the current flowing through each of the aforementioned conductive members, A capacitor (31) connected in parallel to the series connection, In a first battery (21) and a second battery (22) connected in series, a connection path (60) electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point (O) that connects the second ends of the windings of each phase, The system includes a control unit (70) that controls the switching of the upper arm switch and the lower arm switch so that current flows between the first battery and the second battery via the inverter, winding, and connection path, The control unit sets the command value of the current to flow through the connection path in a sinusoidal shape, and performs the switching control to control the current flowing through the connection path to the set command value, power converter (10).

7. The power conversion device according to any one of claims 1 to 6, wherein the control unit performs switching control of at least two phases of the upper arm switch and the lower arm switch.

8. A multiphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y), A multiphase inverter (30) having a series connection of upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL), In each phase, a conductive member (32U, 32V, 32W) connects the low-potential terminal of the upper arm switch and the high-potential terminal of the lower arm switch to the first end of the winding, A current sensor for detecting the current flowing through each of the aforementioned conductive members, A capacitor (31) connected in parallel to the series connection, In a first battery (21) and a second battery (22) connected in series, a connection path (60) electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point (O) that connects the second ends of the windings of each phase, The system includes a control unit (70) that controls the switching of the upper arm switch and the lower arm switch so that current flows between the first battery and the second battery via the inverter, winding, and connection path, The control unit synchronizes the switching control of the upper arm switches for all phases, and also synchronizes the switching control of the lower arm switches for all phases, in the power converter (10).

9. A multiphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y), A multiphase inverter (30) having a series connection of upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL), In each phase, a conductive member (32U, 32V, 32W) connects the low-potential terminal of the upper arm switch and the high-potential terminal of the lower arm switch to the first end of the winding, A current sensor for detecting the current flowing through each of the aforementioned conductive members, A capacitor (31) connected in parallel to the series connection, In a first battery (21) and a second battery (22) connected in series, a connection path (60) electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point (O) that connects the second ends of the windings of each phase, The system includes a control unit (70) that controls the switching of the upper arm switch and the lower arm switch so that current flows between the first battery and the second battery via the inverter, winding, and connection path, A power converter (10) is provided on the connection path, which is configured to electrically connect the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point when in the ON state, and to electrically disconnect the negative electrode side of the first battery and the positive electrode side of the second battery from the neutral point when in the OFF state.

10. The power conversion device according to claim 9, wherein the control unit turns on the connection switch when there is a request for the first battery and the second battery to increase in temperature.

11. The power conversion device according to claim 10, wherein the control unit turns off the connection switch when there is no request for temperature increase.

12. The power conversion device according to claim 10 or 11, wherein the control unit turns off the connection switch and turns off the upper arm switch and the lower arm switch when there is no request for temperature increase and no request for the rotating electric machine to drive.

13. The power conversion device according to any one of claims 9 to 12, wherein the control unit, when there is a request to drive the rotating electric machine, turns off the connection switch and controls the switching of the upper arm switch and the lower arm switch in order to rotate the rotating electric machine.

14. The aforementioned winding is a three-phase winding. The power conversion device according to any one of claims 1 to 13, wherein the inverter has three series connections of the upper arm switch and the lower arm switch.

15. A multiphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y), A multiphase inverter (30) having a series connection of upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL), In each phase, a conductive member (32U, 32V, 32W) connects the low-potential terminal of the upper arm switch and the high-potential terminal of the lower arm switch to the first end of the winding, A current sensor for detecting the current flowing through each of the aforementioned conductive members, A capacitor (31) connected in parallel to the series connection, In a first battery (21) and a second battery (22) connected in series, a connection path (60) electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point (O) that connects the second ends of the windings of each phase, The system includes a control unit (70) that controls the switching of the upper arm switch and the lower arm switch so that current flows between the first battery and the second battery via the inverter, winding, and connection path, The control unit sets the switching frequency of the switching control when the rotational electric machine is stopped to a higher frequency than the switching frequency of the upper and lower arm switches when the rotational electric machine is being driven. (Power converter (10))

16. A multiphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y), A multiphase inverter (30) having a series connection of upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL), In each phase, a conductive member (32U, 32V, 32W) connects the low-potential terminal of the upper arm switch and the high-potential terminal of the lower arm switch to the first end of the winding, A current sensor for detecting the current flowing through each of the aforementioned conductive members, A capacitor (31) connected in parallel to the series connection, In a first battery (21) and a second battery (22) connected in series, a connection path (60) electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point (O) that connects the second ends of the windings of each phase, The system includes a control unit (70) that controls the switching of the upper arm switch and the lower arm switch so that current flows between the first battery and the second battery via the inverter, winding, and connection path, The control unit is a power converter (10) that performs the switching control when the rotating electric machine is not being driven.

17. A multiphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y), A multiphase inverter (30) having a series connection of upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL), In each phase, a conductive member (32U, 32V, 32W) connects the low-potential terminal of the upper arm switch and the high-potential terminal of the lower arm switch to the first end of the winding, A current sensor for detecting the current flowing through each of the aforementioned conductive members, A capacitor (31) connected in parallel to the series connection, In a first battery (21) and a second battery (22) connected in series, a connection path (60) electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point (O) that connects the second ends of the windings of each phase, In a program applied to a power converter (10) equipped with the following features, A connection switch (61) is provided on the connection path, which, when in the ON state, electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point, and when in the OFF state, electrically disconnects the negative electrode side of the first battery and the positive electrode side of the second battery from the neutral point. A program that causes a computer (70) to perform a process of switching control of the upper arm switch and the lower arm switch so that current flows between the first battery and the second battery through the inverter, the winding, and the connection path.

18. A multiphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y), A multiphase inverter (30) having a series connection of upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL), In each phase, a conductive member (32U, 32V, 32W) connects the low-potential terminal of the upper arm switch and the high-potential terminal of the lower arm switch to the first end of the winding, A current sensor for detecting the current flowing through each of the aforementioned conductive members, A capacitor (31) connected in parallel to the series connection, In a first battery (21) and a second battery (22) connected in series, a connection path (60) electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point (O) that connects the second ends of the windings of each phase, In a control method for a power converter (10) equipped with the following: A connection switch (61) is provided on the connection path, which, when in the ON state, electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery to the neutral point, and when in the OFF state, electrically disconnects the negative electrode side of the first battery and the positive electrode side of the second battery from the neutral point. A control method for a power converter, comprising a control step of performing switching control of the upper arm switch and the lower arm switch so that current flows between the first battery and the second battery via the inverter, the winding, and the connection path.

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