Power conversion device, program, and method of controlling power conversion device

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 a power conversion device including a rotating electrical machine having windings, an inverter having a series connection of upper and lower arm switches, and a capacitor connected in parallel to the series connection.

Background Art

[0002] As this type of power conversion device, as disclosed 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 a current flows from the storage battery to the capacitor, the inverter and the windings are used as a boost chopper circuit, and when a current flows from the capacitor to the storage battery, the inverter and the windings 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 by the withstand voltage performance of the capacitor, resulting in a decrease in the reliability of the capacitor.

[0005] On the one hand, due to fluctuations in the terminal voltage of the capacitor, the terminal voltage of the capacitor can become excessively low. When a current flows 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, if 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 amount of fluctuation in the terminal voltage of the capacitor. To reduce the amount of fluctuation, a measure of increasing the capacitance of the capacitor can be considered. However, in this case, the capacitor will become larger in size.

[0007] On the other hand, in addition to increasing the capacitance of the capacitor to reduce the amount of fluctuation, a measure of increasing the frequency of the reactive power (ripple current) can also be considered. However, in this case, the noise will increase and the NVH characteristics of the power conversion device will deteriorate.

[0008] A main object of the present invention is to provide a power conversion device capable of reducing the noise generated during the temperature rise control of the storage battery.

Means for Solving the Problems

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

[0010] The capacity of the storage battery is sufficiently larger than that of the capacitor. Therefore, the increase or decrease amount of the terminal voltage with respect to the charge and discharge current of the storage battery is sufficiently smaller than the increase or decrease amount of the terminal voltage with respect to the charge and discharge current of the capacitor. Thus, if power can be exchanged between the storage batteries instead of between the capacitor and the storage battery, the fluctuation amount of the terminal voltage of the capacitor during the 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 storage batteries via the inverter, the present invention provides a connection path that electrically connects the negative electrode side of the first storage battery and the positive electrode side of the second storage battery in the first storage battery and the second storage battery connected in series, and the winding of the rotating electrical machine. And, the control unit of the present invention performs switching control of the upper arm switch and the lower arm switch so that a current flows between the first storage battery and the second storage battery via the inverter, the winding, and the connection path in order to raise the temperature of the first and second storage batteries. Thereby, the fluctuation amount of the terminal voltage of the capacitor can be reduced without increasing the switching frequency of the upper and lower arm switches. Therefore, according to the present invention described above, the noise generated during the temperature rise control of the first and second storage batteries can be reduced.

Brief Description of the Drawings

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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 electrical machine 40. The power conversion device 10 has a function of exchanging power between the battery pack 20 and the rotating electrical machine 40 via the inverter 30 in order to raise the temperature of the battery pack 20.

[0015] The rotating electrical machine 40 is a three-phase synchronous machine and includes U, V, and W phase windings 41U, 41V, and 41W that are star-connected as stator windings. Each phase winding 41U, 41V, and 41W is arranged with a 120° electrical angle shift. The rotating electrical machine 40 is, for example, a permanent magnet synchronous machine. In the present embodiment, the rotating electrical machine 40 is an in-vehicle main machine and serves as a driving power source for the vehicle.

[0016] The inverter 30 includes three sets of series-connected bodies of upper arm switches QUH, QVH, QWH and lower arm switches QUL, QVL, QWL. In the present embodiment, voltage-controlled semiconductor switching elements are used as the switches QUH, QVH, QWH, QUL, QVL, QWL, and specifically IGBTs are used. Therefore, the high-potential side terminals of the switches QUH, QVH, QWH, QUL, QVL, QWL are collectors, and the low-potential side terminals are emitters. Diodes DUH, DVH, DWH, DUL, DVL, DWL as freewheel diodes are connected in anti-parallel to the switches QUH, QVH, QWH, QUL, QVL, QWL.

[0017] The first end of the U-phase winding 41U 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 a U-phase conductive member 32U such as a bus bar. The first end of the V-phase winding 41V is connected to the emitter of the V-phase upper arm switch QVH and the collector of the V-phase lower arm switch QVL via a V-phase conductive member 32V such as a bus bar. The first end of the W-phase winding 41W 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 a W-phase conductive member 32W such as a bus bar. The second ends of the U, V, and W-phase windings 41U, 41V, and 41W are connected to each other at the neutral point O. In this embodiment, the number of turns of 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 the upper arm switches QUH, QVH, and QWH are connected to the positive terminal of the battery pack 20 by a positive bus bar Lp such as a bus bar. The emitters of the lower arm switches QUL, QVL, and QWL are connected to the negative terminal of the battery pack 20 by a negative bus bar Ln such as a bus bar.

[0019] The power conversion device 10 includes a capacitor 31 that connects the positive bus bar Lp and the negative bus bar Ln. Note that 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 battery cells as single cells, and the terminal voltage is, for example, several hundred V. In this embodiment, the terminal voltages (for example, rated voltages) of the battery cells constituting the battery pack 20 are set to be the same as each other. As the battery cell, for example, a secondary battery such as a lithium ion battery can be used.

[0021] In this embodiment, among the battery cells constituting the assembled battery 20, a series connection body of a plurality of battery cells on the high potential side constitutes the first storage battery 21, and a series connection body of a plurality of battery cells on the low potential side constitutes the second storage battery 22. That is, the assembled battery 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. For this reason, the terminal voltage (for example, the rated voltage) of the first storage battery 21 is the same as the terminal voltage (for example, the rated voltage) of the second storage battery 22.

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

[0023] The power conversion device 10 includes a monitoring unit 50 (corresponding to a voltage information detection unit). The monitoring unit 50 monitors the terminal voltage, SOC, SOH, temperature, etc. of each battery cell constituting the assembled battery 20.

[0024] The power conversion device 10 includes a connection path 60 and a connection switch 61. The connection path 60 electrically connects the intermediate terminal B of the assembled battery 20 and 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 conversion device 10 includes a current sensor 62 that detects the current flowing through the connection path 60. The detection value of the current sensor 62 is input to a control device 70 (corresponding to a control unit) included in the power conversion device 10.

[0026] The control device 70 is mainly composed of a microcomputer, and performs switching control of each switch constituting the inverter 30 in order to feedback-control the control amount of the rotating electrical machine 40 to its command value. The control amount is, for example, torque.

[0027] The control device 70 controls the connection switch 61 to be turned on and off, and is also capable of communicating with the monitoring unit 50. Further, the control device 70 is capable of communicating with a host control device 80 provided outside the power conversion device 10. The host control device 80 oversees the control of the vehicle.

[0028] Incidentally, the control device 70 realizes various control functions by executing a program stored in a storage device provided therein. The various functions may be realized by an electronic circuit which is hardware, or may be realized by both hardware and software.

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

[0030] In step S10, it is determined whether there is a temperature increase request for the battery pack 20. For example, if it is determined that there is a temperature increase instruction for the battery pack 20 from the host control device 80, or if it is determined that the temperature of the battery pack 20 detected by the monitoring unit 50 is less than the threshold temperature, it may be determined that there is a temperature increase request. Here, the temperature to be compared with the threshold temperature may be, for example, the lowest temperature among the temperatures of the detected battery cells, or the average temperature of each battery cell calculated based on the temperatures of the detected battery cells.

[0031] In the present embodiment, the situation where an affirmative determination is made in step S10 assumes the situation during vehicle stop before the rotation electric machine 40 is driven.

[0032] If it is determined in step S10 that there is no temperature increase request, the process proceeds to step S11, and it is determined whether there is a drive request for the rotation electric machine 40. In the present embodiment, this drive request includes a request to drive the vehicle by rotationally driving the rotation 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 standby mode is set. By setting this mode, each switch QUH to QWL of the inverter 30 is turned off. Then, in step S13, the connection switch 61 is turned off. As a result, the intermediate terminal B and the neutral point O are electrically disconnected.

[0034] If it is determined in step S11 that there is a drive request, the process proceeds to step S14 and the drive mode of the rotating electrical machine 40 is set. Then, in step S16, the connection switch 61 is turned on. As a result, the intermediate terminal B and the neutral point O are electrically connected via the connection path 60. Thereafter, in step S16, switching control of each switch QUH to QWL of the inverter 30 is performed to rotationally drive the rotating electrical machine 40. As a result, the drive wheels of the vehicle rotate and the vehicle can be driven. Note that the switching control in step S16 may be implemented, for example, using PWM or a pulse pattern based on a comparison of the command voltage applied to each phase winding 41U to 41W and a carrier signal (e.g., a triangular wave signal).

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

[0036] In step S19, temperature increase PWM control for increasing the temperature of the battery pack 20 is performed. Hereinafter, this control will be described.

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

[0038] The equivalent circuit of Fig. 3(a) can be shown as the equivalent circuit of Fig. 3(b). The circuit of Fig. 3(b) is a buck-boost chopper circuit capable of bidirectional power transfer between the first battery 21 and the second battery 22. In Fig. 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 the charging currents of the first and second batteries 21 and 22 flow, IBH and IBL become negative, and when the discharging currents of the first and second batteries 21 and 22 flow, IBH and IBL become positive. Also, VR represents the terminal voltage of the winding 41, and IR represents the current flowing into the neutral point O. When a current flows into the neutral point O in the positive direction from the winding 41 toward the intermediate terminal B, IR becomes negative, and when a current flows into the neutral point O in the opposite direction, IR becomes positive.

[0039] Referring to Fig. 3(b), when the upper-arm switch QH is turned on, the terminal voltage VR of the winding 41 becomes "VBH". On the other hand, when the lower-arm switch QL is turned on, the terminal voltage VR of the winding 41 becomes "-VBL". That is, by turning on the upper-arm switch QH, an exciting current can flow in the positive direction through the winding 41, and by turning on the lower-arm switch QL, an exciting current can flow in the negative direction through the winding 41.

[0040] Fig. 4 shows a block diagram of the temperature-rising PWM control.

[0041] In the control device 70, a current deviation calculation unit 71 calculates a current deviation by subtracting a current (hereinafter, detected current IMr) detected by a current sensor 62 from a command current IM*. In the present embodiment, as shown in FIG. 5, the command current IM* is set as a sine wave. Specifically, in one cycle Tc of the command current IM*, the command current IM* is set such that the positive command current IM* and the negative command current IM* are point-symmetrical with respect to the zero-crossing timing of the command current IM*. Thereby, the period from the zero-up-crossing timing to the zero-down-crossing timing of the command current IM* and the period from the zero-down-crossing timing to the zero-up-crossing timing of the command current IM* become the same. Also, in one cycle Tc of the command current IM*, the area S1 of the first region and the area S2 of the second region become equal. The first region S1 is a region surrounded by the time axis from the zero-up-crossing timing to the zero-down-crossing timing of the command current IM* and the positive command current IM* in one cycle Tc of the command current IM*. The second region is a region surrounded by the time axis from the zero-down-crossing timing to the zero-up-crossing timing of the command current IM* and the negative command current IM* in one cycle Tc. By setting "S1 = S2", the balance of the charge and discharge currents of the first storage battery 21 and the second storage battery 22 in one cycle Tc can be made to match, and an increase in the difference between the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22 due to the temperature rise control can be suppressed.

[0042] Note that the frequency fc of the command current IM*, which is the reciprocal of one cycle Tc of the command current IM*, is preferably set to, for example, a frequency on the lower limit side of the audible range of humans. Specifically, the frequency fc is preferably set to 1 kHz or less, which is a frequency region where the correction value (dB) is 0 or less in the A characteristic, and more preferably set to a frequency (for example, 50 Hz) between 30 Hz and 100 Hz.

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

[0044] The PWM generation unit 73 generates gate signals for each of the upper - arm switches QUH, QVH, QWH based on the calculated duty ratio Duty. The gate signal is a signal that instructs on - control or off - control. In this embodiment, the gate signals of each of the upper - arm switches QUH, QVH, QWH are synchronized.

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

[0046] Fig. 6 shows the transition of the switching pattern and the like during the temperature - rising PWM control. Fig. 6(a) shows the transition of the gate signals of each of the upper - arm switches QUH, QVH, QWH, Fig. 6(b) shows the transition of the gate signals of each of the lower - arm switches QUL, QVL, QWL. Fig. 6(c) shows the transition of the current IR flowing through the neutral point O and the transition of the command current IM*. Fig. 6(d) shows the transition of the current IBH flowing through the first storage battery 21, and Fig. 6(e) shows the transition of the current IBL flowing through the second storage battery 22.

[0047] As shown in FIGS. 6(a) and 6(b), a temperature-rising PWM control is implemented in which the upper-arm switches QUH, QVH, QWH and the lower-arm switches QUL, QVL, QWL are alternately turned on. This control continues until the temperature-rising requirement in step S10 of FIG. 2 disappears. By this control, as shown in FIGS. 6(d) and 6(e), pulsed currents flow through the first storage battery 21 and the second storage battery 22. During the period when the command current IM* is positive, the first storage battery 21 discharges and the second storage battery 22 is charged. On the other hand, during the period when the command current IM* is negative, the second storage battery 22 discharges and the first storage battery 21 is charged. Note that the average values IBHave and IBLave of the pulsed currents are sinusoidal currents including components having the same frequency as the frequency of the command current IM*.

[0048] FIG. 7 shows the simulation results of the present embodiment. FIGS. 7(a) to 7(c) correspond to FIGS. 6(c) to 6(e) above, and FIG. 7(d) shows the transition of the terminal voltage of the capacitor 31. As shown in FIG. 7(d), the terminal voltage of the capacitor 31 does not fluctuate.

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

[0050] As shown in FIG. 8(b), in the comparative example, the terminal voltage of the capacitor fluctuates greatly with the same period as the current IR flowing through the neutral point O. In order to reduce this fluctuation, it is necessary to increase the capacitance of the capacitor or reduce the amplitude of the command current IM*, that is, the temperature-rising ability.

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

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

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

[0054] In the temperature rise control, the control device 70 synchronizes the switching control of the upper arm switches QUH, QVH, QWH of all phases, and also synchronizes the switching control of the lower arm switches QUL, QVL, QWL of all phases. Thereby, each phase winding 41U, 41V, 41W can be regarded as an equivalent circuit in which the windings are connected in parallel. For this reason, the inductance of the winding during the temperature rise control can be reduced. Thereby, the amount of change in the current flowing through the neutral point O in one switching period Tsw can be increased, and the temperature rise control can be performed using a large current.

[0055] Also, by synchronizing the switching control, rotation of the rotor of the rotating electrical machine 40 can be suppressed.

[0056] When the control device 70 determines that there is a temperature rise request for the battery pack 20, it turns on the connection switch 61, and when it determines that there is no temperature rise request, it turns off the connection switch 61. Thereby, it is possible to suppress current from flowing from the neutral point O to the intermediate terminal B during vehicle travel.

[0057] <Modification Example 1 of the First Embodiment> As shown in FIG. 9, it is also possible to perform temperature increase PWM control by performing on-off control on two out of the three phases. FIG. 9 shows an example in which the upper and lower arm switches QWH and QWL of the W phase are maintained in the off control. FIG. 9(a) shows the transition of the gate signals of the upper arm switches QUH and QVH of the U and V phases, FIG. 9(b) shows the transition of the gate signals of the lower arm switches QUL and QVL of the U and V phases, FIG. 9(c) shows the transition of the gate signals of the upper and lower arm switches QWH and QWL of the W phase, and FIGS. 9(d) to (f) correspond to FIGS. 6(c) to (e) above.

[0058] Also, as shown in FIG. 10, it is also possible to perform temperature increase PWM control by performing on-off control on one out of the three phases. FIG. 10 shows an example in which only the upper and lower arm switches QUH and QUL of the U phase are subjected to on-off control. FIGS. 10(a) and (b) show the transition of the gate signals of the upper arm switches QUH and QUL of the U phase, FIG. 10(c) shows the transition of the gate signals of the upper and lower arm switches QVH and QVL of the V phase and the upper and lower arm switches QWH and QWL of the W phase, and FIGS. 10(d) to (f) correspond to FIGS. 9(d) to (f) above.

[0059] Even in the switching control shown in FIGS. 9 and 10, when the ripple current is small, the equivalent inductance of the winding 41 can be increased to reduce the current ripple, and in some cases, the iron loss can be reduced compared to performing switching control on all phases.

[0060] <Modification Example 2 of the First Embodiment> Instead of the configuration of FIG. 4, switching control may be performed according to the configuration shown in FIG. 11. In the control device 70, the hysteresis control unit 75 generates gate signals for the upper arm switches QUH, QVH, and QWH shown in FIG. 12(b) based on the command current IM* and the detected current IMr. Specifically, the hysteresis control unit 75 generates gate signals for the upper arm switches 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 the lower arm switches QUL, QVL, and QWL shown in FIG. 12(c) by inverting the logic of the gate signals for the upper arm switches QUH, QVH, and QWH generated by the hysteresis control unit 75. As a result, as shown in FIG. 12(a), the detected current IMr is controlled within a range having a width of ±ΔI with respect to the command current IM*.

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

[0062] In this embodiment, the control device 70 corrects the command current IM* so that the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22 are equalized. Specifically, the control device 70 calculates the terminal voltage VHr of the first storage battery 21 and the terminal voltage VLr of the second storage battery 22 based on the information transmitted from the monitoring unit 50. When the control device 70 determines that the terminal voltage VHr of the first storage battery 21 is higher than the terminal voltage VLr of the second storage battery 22, as shown in FIG. 13, a DC component Idc (>0) is added to the command current IM* to calculate the corrected command current. 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. As a result, in one cycle Tc, the discharge current of the first storage battery 21 exceeds the discharge current of the second storage battery 22, and the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22 are equalized.

[0063] On one hand, when 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, as shown in FIG. 14, it calculates the corrected command current by subtracting the DC component Idc from the command current IM*. 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 present embodiment described above, while performing the temperature rise control, it is possible to equalize the terminal voltages of the first battery 21 and the second battery 22.

[0065] <Modification Example of the Second Embodiment> · 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, the DC component Idc may be variably set. 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 the "VHr - VLr", 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 the "VLr - VHr", the larger the DC component Idc may be set.

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

[0067] <Third Embodiment> Hereinafter, the third embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, when the driving of the rotating electrical machine 40 is stopped, the control device 70 sets the switching frequency fsw (= 1 / Tsw) to be higher than the switching frequencies of the upper and lower arm switches QUH to QWL when the rotating electrical machine 40 is rotationally driven and the vehicle is running, and to a frequency within the inaudible range of humans.

[0068] Fig. 15 shows the procedure of 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 Fig. 15, the same processes as those shown in Fig. 2 above are given the same reference numerals for convenience.

[0069] After the completion of the process in 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 the process of step S16. Specifically, the switching frequency fsw is set to a frequency of 16 kHz or higher, for example, to a frequency within the inaudible range of humans (20 kHz or higher).

[0070] The temperature rise control is performed while the vehicle is stopped. Such a situation is one in which the human auditory sensitivity to the noise associated with the switching control of the inverter 30 is high. Therefore, by setting the switching frequency fsw to a frequency of 16 kHz or higher at which it is difficult for humans to hear and which is not in the inaudible range, or to a frequency in the inaudible range, the NVH characteristics of the power conversion device 10 during the temperature rise control can be improved. Note that since a frequency of 16 kHz or higher is an excessively high frequency, heat generation of each switch QUH to QWL due to switching losses is a concern. However, during the temperature rise control, since the environment around the vehicle is a low-temperature environment, the temperature of each switch QUH to QWL is unlikely to exceed its allowable upper limit value.

[0071] <Fourth Embodiment> In the first embodiment, the rotating electrical machine and the inverter may be other than three-phase, such as five-phase or seven-phase. FIG. 16 shows a power conversion device in the case of five-phase. In FIG. 16, the same components as those shown in FIG. 1 above are given the same reference numerals for convenience.

[0072] In FIG. 16, in the inverter 30, the upper and lower arm switches QXH and QXL of the X phase and the respective diodes DXH and DXL are added, and the upper and lower arm switches QYH and QYL of the Y phase and the respective diodes DYH and DYL are added. Also, in the rotating electrical machine 40, an X-phase winding 41X and a Y-phase winding 41Y are added. Further, in the power conversion device 10, an X-phase conductive member 32X and a Y-phase conductive member 32Y are added.

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

[0074] FIG. 17 shows a configuration diagram of the power conversion device in this embodiment. In FIG. 17, the same components as those shown in FIG. 1 above are given the same reference numerals for convenience.

[0075] In the configuration of the first embodiment shown in FIG. 1 above, the power conversion device 10 included a connection path 60, a connection switch 61, and a current sensor 62. Instead of these configurations, in this embodiment, the power conversion device 10 includes a connection path 90, a connection switch 91, and a current sensor 92. 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 connection path 90. The connection switch 91 and the current sensor 92 are provided on the connection path 90.

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

[0077] FIG. 18 shows a block diagram of the temperature increase PWM control in this embodiment. In FIG. 18, since the configurations of the current deviation calculation unit 71 and the feedback control unit 72 and the method of setting the command current IM* are the same as those in the first embodiment, the description thereof 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 ratio Duty 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 of 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. Also, 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 synchronized.

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

[0080] In this embodiment, as shown in FIG. 19(d), the upper and lower arm switches QUH and QUL of the U phase are turned off. Also, as shown in FIGS. 19(e) and 19(f), the upper arm switches QVH and QWH of the V and W phases and the lower arm switches QVL and QWL of the V and W phases are alternately turned on. By this control, as shown in FIGS. 19(b) and 19(c), a pulsed current flows through the first storage battery 21 and the second storage battery 22, and as shown in FIG. 19(a), the current IR is controlled to the command current IM*.

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

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

[0083] The intermediate terminal B of the battery pack 20 is connected to the emitter of the upper arm switch QUH of the U phase and the collector of the lower arm switch QUL of the U phase via the connection path 90. In this configuration, the control device 70 performs switching control of each switch QUH to QWL so that a ripple current flows between the first storage battery 21 and the second storage battery 22 via the upper and lower arm switches QVH, QWH, QVL, QWL of the V and W phases, each phase winding 41U, 41V, 41W, and the connection path 90. Thereby, the same effect as that of the first embodiment can be obtained.

[0084] In the temperature rise control, the control device 70 synchronizes the switching control of the upper arm switches QVH and QWH of the V and W phases, and also synchronizes the switching control of the lower arm switches QVL and QWL of the V and W phases. Thereby, the V and W phase windings 41V and 41W can be regarded as an equivalent circuit in which the windings are connected in parallel. Therefore, the inductance of the winding during the temperature rise control can be reduced.

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

[0086] <Modification Example 2 of the Fifth Embodiment> The control device 70 may perform temperature-rise PWM control for on / off control of only one phase. FIG. 22 shows an example in which the upper and lower arm switches QWH and QWL of phase W are subjected to on / off control. FIGS. 22(a) to (c) correspond to FIGS. 19(a) to (c) above. FIG. 22(d) shows the transition of the gate signals of the upper and lower arm switches QUH, QUL, QVH, and QVL of phases U and V, FIG. 22(e) shows the transition of the gate signal of the upper arm switch QWH of phase W, and FIG. 22(f) shows the transition of the gate signal of the lower arm switch QWL of phase W.

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

[0088] According to the switching control shown in FIG. 22, when the ripple current is small, the equivalent inductance of the winding 41 is increased to reduce the current ripple, and the iron loss can be reduced more than when performing switching control of phases V and W.

[0089] <Modification Example 3 of the Fifth Embodiment> The control device 70 may perform temperature increase control according to the procedure shown in the previous FIG. 15. In this case, after the completion of the process of step S18 in the previous FIG. 15, the control device 70 proceeds to step S20 and performs temperature increase PWM control. In the present embodiment, the switching frequency fsw of the upper and lower arm switches QVH, QWH, QVL, and QWL of the V and W phases is set higher than the switching frequency set in the process of step S16. Thereby, the same effect as that of the third embodiment can be obtained.

[0090] <Modification Example 4 of the Fifth 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. Thereby, the same effect as that of the second embodiment can be obtained.

[0091] <Modification Example 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 the upper and lower arm switches QUH and QUL of the U phase, and may be, for example, the upper and lower arm switches QVH and QVL of the V phase. In this case, in the temperature increase control, the upper and lower arm switches QVH and QVL of the V phase are turned off. Also, the upper arm switches QUH and QWH of the U and W phases and the lower arm switches QUL and QWL of the U and W phases are alternately turned on.

[0092] Also, the upper and lower arm switches connected to the intermediate terminal B may be, for example, the upper and lower arm switches QWH and QWL of the W phase. In this case, in the temperature increase control, the upper and lower arm switches QWH and QWL of the W phase are turned off. Also, the upper arm switches QUH and QVH of the U and V phases and the lower arm switches QUL and QVL of the U and V phases are alternately turned on.

[0093] <Sixth Embodiment> Hereinafter, the sixth embodiment will be described with reference to the drawings, centering on the differences from the fifth embodiment. In the present 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 only necessary that the intermediate terminal B is not connected to the upper and lower arm switches of all of the U, V, and W phases.

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

[0095] In the present embodiment, when performing the temperature rise PWM control, the upper and lower arm switches QUH, QUL, QWH, and QWL of the U and W phases are turned off. Further, the upper arm switch QVH of the V phase and the lower arm switch QVL of the V phase are alternately turned on.

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

[0097] <Seventh Embodiment> In the fifth embodiment, as described in the fourth embodiment, the rotating electrical machine and the inverter may be other than three-phase, such as five-phase or seven-phase. Fig. 24 shows a power conversion device in the case of five-phase. In Fig. 24, the same components as those shown in Fig. 17 are given the same reference numerals for convenience.

[0098] <Other Embodiments> Note that the above embodiments may be implemented with the following modifications.

[0099] · The installation location of the current sensor for detecting the current flowing through the neutral point O is not limited to that illustrated in Fig. 1. For example, current sensors may be provided on the respective conductive members 32U, 32V, and 32W in Fig. 1. In this case, during the temperature rise control, the total value of the currents detected by the current sensors on the respective conductive members 32U, 32V, and 32W may be defined as the detected current IMr.

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

[0101] Also, the method for setting the command current IM* is not limited to those satisfying the above point-symmetrical relationship. For example, in one cycle Tc, the period from the zero up-crossing timing to the zero down-crossing timing of the command current IM* and the period from the zero down-crossing timing to the zero up-crossing timing of the command current IM* are made different, and the command current IM* may be set so that the area S1 of the first region and the area S2 of the second region are equal. Even in this case, the balance of the charge and discharge currents of the first battery 21 and the second battery 22 in one cycle Tc can be adjusted.

[0102] ·The number of battery cells of each of 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 are different, and also, the intermediate terminal B is provided at a position that does not equally divide each battery cell constituting the battery pack 20.

[0103] ·In the first embodiment, in the temperature increase control, the switching control of the upper arm switches QUH, QVH, QWH of all phases does not have to be synchronized, and the switching control of the lower arm switches QUL, QVL, QWL of all phases does not have to be synchronized either.

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

[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] ·In configuring the upper and lower arm switches that make up the inverter, they are not limited to IGBTs, and for example, N-channel MOSFETs may be used. In this case, the high-potential side terminal becomes the drain and the low-potential side terminal becomes the source.

[0107] ·The first battery and the second battery do not necessarily constitute a battery pack.

[0108] The control unit and its method described in the present disclosure may be implemented by a dedicated computer configured by a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and its method described in the present disclosure may be implemented by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Or, the control unit and its method described in the present disclosure may be implemented by one or more dedicated computers configured by a combination of a processor programmed to execute one or more functions and a memory and a processor configured by one or more hardware logic circuits. Also, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer.

Description of Reference Numerals

[0109] 10... Power conversion device, 20... Battery pack, 30... Inverter, 31... Capacitor, 40... Rotating electrical machine, 41U, 41V, 41W... U, V, W phase windings, 60, 90... Connection paths, 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 switches, QUL, QVL, QWL... U, V, W phase lower arm switches.

Claims

1. A polyphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y); a polyphase inverter (30) having upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) connected in series; A power conversion device (10) including a capacitor (31) connected in parallel to the series-connected body, a connection path (60) electrically connecting a negative electrode side of the first storage battery (21) and a positive electrode side of the second storage battery (22) connected in series with a neutral point (O) of the winding; A power conversion device comprising: a control unit (70) that performs switching control of the upper arm switch and the lower arm switch so that current flows between the first storage battery and the second storage battery via the inverter, the winding, and the connection path.

2. The power conversion device according to claim 1, wherein the control unit performs switching control of the upper arm switches and the lower arm switches of at least two phases so that current flows between the first storage battery and the second storage battery via the inverter, the winding, and the connection path.

3. The power conversion device according to claim 2, wherein the control unit synchronizes switching control of the upper arm switches of all phases and also synchronizes switching control of the lower arm switches of all phases so that current flows between the first storage battery and the second storage battery via the inverter, the winding, and the connection path.

4. The power conversion device according to any one of claims 1 to 3, further comprising a connection switch (61) that is provided on the connection path and that, when turned on, electrically connects the negative electrode side of the first storage battery and the positive electrode side of the second storage battery to the neutral point, and, when turned off, electrically disconnects the negative electrode side of the first storage battery and the positive electrode side of the second storage battery from the neutral point.

5. A polyphase rotating electric machine (40) having windings (41U, 41V, 41W, 41X, 41Y); a polyphase inverter (30) having upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) connected in series; A power conversion device (10) including a capacitor (31) connected in parallel to the series-connected body, In each phase, a connection point of the upper arm switch and the lower arm switch constituting the series-connected body is electrically connected to one end of the winding opposite to a neutral point (O), a connection path (90, 90U, 90W) electrically connecting a negative electrode side of the first storage battery and a positive electrode side of the second storage battery in a first storage battery (21) and a second storage battery (22) connected in series to a connection point of the upper arm switch and the lower arm switch constituting the series-connected body of a part of a plurality of phases; a control unit (70) that performs switching control of the upper arm switch and the lower arm switch so that a current flows between the first storage battery and the second storage battery via the inverter, the winding, and the connection path; a connection switch (91) that is provided on the connection path, and that, when turned on, electrically connects the negative electrode side of the first storage battery and the positive electrode side of the second storage battery to the connection points of the upper arm switch and the lower arm switch, and, when turned off, electrically disconnects the negative electrode side of the first storage battery and the positive electrode side of the second storage battery from the connection points, Among the multiple phases, there are two or more phases to which the connection path is not connected to the connection point, The control unit of the power conversion device turns on the connection switch when current flows between the first storage battery and the second storage battery via the connection path, controls off the upper arm switch and the lower arm switch of the phase among the multiple phases to which the connection path is connected, and switches on and off the upper arm switch and the lower arm switch of at least two phases among the multiple phases to which the connection path is not connected.

6. The power conversion device according to claim 5, wherein the control unit synchronizes switching control of the upper arm switches of all phases to which the connection path is not connected among the multiple phases, so that current flows between the first storage battery and the second storage battery via the inverter, the winding, and the connection path, and also synchronizes switching control of the lower arm switches of all phases to which the connection path is not connected among the multiple phases.

7. The power conversion device according to claim 5 or 6, wherein the control unit turns the connection switch on when it determines that there is a request to increase the temperature of the first storage battery and the second storage battery, and turns the connection switch off when it determines that there is no request to increase the temperature.

8. The power conversion device according to any one of claims 1 to 7, wherein the control unit sets a switching frequency of the switching control when the driving of the rotating electric machine is stopped to a frequency higher than the switching frequency of the upper and lower arm switches when the rotating electric machine is driven.

9. The power conversion device according to any one of claims 1 to 8, wherein the control unit sets the command value so that, in one cycle of the command value for the current to be flowed through the connection path, the area of ​​an area specified by a positive command value is equal to the area of ​​an area specified by a negative command value, and performs the switching control to control the current flowing through the connection path to the command value.

10. The power conversion device according to claim 9 , 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 a zero-crossing timing of the command value in one cycle of the command value.

11. A voltage information detection unit (50) that detects voltage information of the first storage battery and the second storage battery, The power conversion device according to claim 9 or 10, wherein the control unit corrects the command value based on the detected voltage information so that a terminal voltage of the first storage battery and a terminal voltage of the second storage battery are equalized.

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