CONTROL DEVICE, PROGRAM, AND CONTROL METHOD

Abstract

To provide a power conversion device that can be miniaturized.SOLUTION: A power conversion device 11 comprises: a rotary electric machine 40 having windings 41U to 41W; an inverter 30 having upper arm switches QUH to QWH and lower arm switches QUL to QWL; a connection path 60 which electrically connects an intermediate terminal B to which a negative electrode terminal of a first storage battery 21 and a positive electrode terminal of a second storage battery 22 are connected, with a neutral point O of the windings 41U to 41W; a connection switch 61 that is provided on the connection path 60, and electrically connects the intermediate terminal B and the neutral point O when turned on and electrically disconnects the intermediate terminal B and the neutral point O when turned off; and a control device 70 that determines whether or not to turn on the connection switch 61, and when it is determined to turn on the connection switch 61, turns on the connection switch 61 and performs switching control of the upper and lower arm switches QUH to QUW.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to CONTROL DEVICE, PROGRAM, AND CONTROL METHOD Regarding. [Background technology]

[0002] A known power conversion device includes a rotating electric machine having a winding and an inverter having a series connection of upper and lower arm switches. The power conversion device performs various operations to meet requirements during switching control of the upper and lower arm switches. For example, in the power conversion device described in Patent Document 1, switching control is performed based on the air pressure around the rotating electric machine to ensure the insulation performance of the rotating electric machine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-288170 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to meet the requirements for switching control, the power conversion device may become larger. For example, in order to ensure the desired insulation performance, the insulation distance between the windings of the rotating electric machine is increased, which increases the size of the rotating electric machine. There is still room for improvement in the power conversion device to address such issues.

[0005] The present invention has been made in view of the above problems, and its main object is to provide a device that can be made compact. CONTROL DEVICE, PROGRAM, AND CONTROL METHOD The purpose of this project is to provide [Means for solving the problem]

[0006] The first configuration of the present invention is a rotating electric machine having star-connected windings; An inverter having a series connection of upper arm switches and lower arm switches, a connection path that electrically connects a negative electrode side of the first power storage unit and a positive electrode side of the second power storage unit, in a first power storage unit and a second power storage unit that are connected in series, to a neutral point of the winding; a connection switch that is provided in the connection path and that, when turned on, electrically connects a negative electrode side of the first power storage unit and a positive electrode side of the second power storage unit to the neutral point and, when turned off, electrically disconnects the negative electrode side of the first power storage unit and the positive electrode side of the second power storage unit from the neutral point; a determination unit that determines whether or not to turn on the connection switch; The power conversion device includes a control unit that turns on the connection switch and performs switching control of the upper arm switch and the lower arm switch when the judgment unit judges that the connection switch should be turned on.

[0007] The power conversion device of the first configuration includes a connection path that electrically connects the negative electrode side of the first power storage unit and the positive electrode side of the second power storage unit with the neutral point of the winding, a connection switch provided in the connection path, and a determination unit. The determination unit determines whether or not to turn on the connection switch in order to respond to a request during switching control. When the determination unit determines that the connection switch should be turned on, the connection switch is turned on and switching control of the upper arm switch and the lower arm switch is performed. This makes it possible to perform various operations to respond to requests while suppressing the addition of new components. As a result, the power conversion device can be made smaller.

[0008] In the second configuration, in the first configuration, the determination unit performs a determination process to determine to turn on the connection switch when it determines that the amount of partial discharge generated in the windings of the same phase is greater than an allowable value.

[0009] If the amount of partial discharge generated in the windings of the same phase becomes larger than the allowable value, the windings may deteriorate, and the insulation performance of the windings may decrease. In order to address this problem, it is conceivable to set the insulation distance between the windings to be longer in order to ensure the desired insulation performance. However, in this case, there is a concern that the rotating electric machine will become larger.

[0010] In this regard, according to the second configuration, it is determined whether or not the amount of partial discharge generated in the windings of the same phase is greater than the allowable value, and the connection switch is turned on and off based on the result of the determination. When the connection switch is in the off state, a voltage difference corresponding to a divided value of the terminal voltage of the series connection of the first and second power storage units is generated in the windings. The maximum value of this divided voltage is higher than a value obtained by dividing the terminal voltage of the series connection of the first and second power storage units in half. On the other hand, when the connection switch is in the on state, the negative pole side of the first power storage unit and the positive pole side of the second power storage unit are connected to the neutral point of the winding. In this case, when the upper and lower arm switches are switched, the terminal voltage of the first power storage unit or the second power storage unit is applied to the winding of each phase. Therefore, when the connection switch is turned on, the voltage difference between the windings of the same phase can be reduced more than when the connection switch is turned off. This makes it possible to reduce the amount of partial discharge generated in the windings of the same phase. As a result, the insulation distance between the windings can be set to be short, and the rotating electric machine can be made smaller in size.

[0011] Furthermore, in the second configuration, the voltage difference between the windings of the same phase can be reduced without lowering the voltage supplied to the inverter, thereby making it possible to suppress a decrease in the output of the rotating electric machine.

[0012] The third configuration is the first configuration, a voltage acquisition unit that acquires a voltage parameter that is a terminal voltage of each of the first power storage unit and the second power storage unit or a correlation value of the terminal voltages; the determination unit determines to turn on the connection switch when a larger voltage parameter of the acquired voltage parameters of the first power storage unit and the second power storage unit is equal to or smaller than a voltage threshold value; When the control unit determines to turn on the connection switch, it turns on the connection switch and performs the switching control to transfer energy from one of the first storage unit and the second storage unit to the other storage unit by flowing current between the first storage unit and the second storage unit via the inverter, the winding, and the connection path.

[0013] Conventionally, a control is performed to transfer energy between a plurality of power storage units. This control requires dedicated switch elements and reactors for transferring energy between the power storage units, which increases the number of components in the power conversion device. In this case, there is a concern that the power conversion device may become large.

[0014] In this regard, according to the third configuration, voltage parameters of the first power storage unit and the second power storage unit are acquired. When the larger of the acquired voltage parameters is equal to or less than the voltage threshold value, it is determined that the connection switch is turned on. With the connection switch in the on state, switching control is performed to transfer energy from one of the first power storage unit and the second power storage unit to the other power storage unit. This allows energy to be transferred between the first power storage unit and the second power storage unit using the winding and the inverter. This allows the power conversion device to be miniaturized.

[0015] Furthermore, in the above-described configuration, energy is exchanged when the voltage parameters of the power storage units are in a reduced state. The smaller the voltage parameters of the power storage units, the smaller the ripple current flowing through the windings. The smaller the ripple current, the smaller the iron loss occurring in the rotating electric machine. Therefore, according to the third configuration, it is possible to reduce the energy loss occurring when exchanging energy.

[0016] The fourth configuration is the first configuration, a voltage acquisition unit that acquires a voltage of the first power storage unit and a voltage of the second power storage unit; the determination unit determines whether or not there is a control request to flow a current between the first power storage unit and the second power storage unit, and determines to turn on the connection switch when it is determined that there is the control request; The control unit is when the determination unit determines to turn on the connection switch and when the voltages of the first power storage unit and the second power storage unit acquired by the voltage acquisition unit are determined to be within a specified voltage range, performing the switching control such that a current flows between the first power storage unit and the second power storage unit via the inverter, the winding, and the connection path in a state in which the connection switch is turned on; when it is determined that the connection switch should be turned on and when it is determined that the minimum value of the voltages of the first power storage unit and the second power storage unit is below a lower limit value of the specified voltage range, performing the switching control so that a discharge current discharged by one of the first power storage unit and the second power storage unit that is an over-discharge protection target having a minimum voltage is made smaller than when the voltages of the first power storage unit and the second power storage unit are within the specified voltage range; When it is determined that the connection switch should be turned on and when it is determined that the maximum value of each of the voltages of the first and second storage units exceeds the upper limit value of the specified voltage range, the switching control is performed so that the charging current charged to the overcharge protection target of the first and second storage units whose voltages are maximum is smaller than when the voltages of the first and second storage units are within the specified voltage range.

[0017] Conventionally, for example, when the temperature of the power storage unit is low, control is performed to pass a current between multiple power storage units in order to raise the temperature of the power storage unit. In this control, there is a concern that the terminal voltage of the power storage unit may deviate from a voltage range in which the reliability of the power storage unit can be maintained, causing degradation of the power storage unit.

[0018] In this regard, in the above-mentioned fourth configuration, when it is determined to turn on the connection switch, with the connection switch turned on, the upper arm switch and the lower arm switch are turned on and off so that current flows between the first and second storage units via the inverter, the winding, and the connection path.

[0019] In the above-mentioned configuration, when it is determined that the connection switch is turned on and the minimum value of the voltages of the first and second power storage units is below the lower limit of the specified voltage range, the discharge current of the overdischarge protection target is reduced. Also, when it is determined that the connection switch is turned on and the maximum value of the voltages of the first and second power storage units is above the upper limit of the specified voltage range, the charge current of the overcharge protection target is reduced. This makes it possible to prevent the voltages of the overdischarge protection target and the overcharge protection target from falling outside the voltage range in which the reliability of the power storage units can be maintained. As a result, it is possible to prevent the first and second power storage units from deteriorating. [Brief description of the drawings]

[0020] [Figure 1] 1 is a configuration diagram of a power conversion system according to a first embodiment. [Diagram 2] Cross-sectional view of the in-phase winding. [Diagram 3] FIG. 4 is a graph showing the relationship between the partial discharge inception voltage and the atmospheric pressure and temperature. [Figure 4] FIG. 4 is a diagram showing the relationship between the winding voltage, the terminal voltage of the storage battery, and the phase current of the winding. [Diagram 5] FIG. 13 is a diagram showing the maximum value of the winding voltage when the connection switch is turned off. [Figure 6] FIG. 13 is a diagram showing the maximum value of the winding voltage when the connection switch is turned on. [Figure 7] 5 is a flowchart showing a procedure for switch drive control. [Figure 8] FIG. 4 is a diagram showing an example of switch drive control. [Figure 9] FIG. 4 is a configuration diagram of a power conversion system according to a modified example of the first embodiment. [Figure 10] FIG. 4 is a configuration diagram of a power conversion system according to a modified example of the first embodiment. [Figure 11] FIG. 11 is a diagram showing an equivalent circuit according to a second embodiment. [Figure 12] FIG. 4 is a functional block diagram of the control device when the vehicle is stopped. [Figure 13]FIG. 4 is a diagram showing a method for setting a neutral point command current. [Figure 14] FIG. 4 is a functional block diagram of the control device when the rotating electric machine is driven. [Figure 15] 4 is a time chart showing the transition of the neutral point current. [Figure 16] 1 is a diagram showing the relationship between the terminal voltage and SOC of a storage battery. [Figure 17] FIG. 4 is a diagram showing the relationship between energy loss occurring in energy management control and power transfer. [Figure 18] FIG. 13 is a diagram showing the relationship between power conversion efficiency and input / output power. [Figure 19] FIG. 13 is a diagram showing the relationship between the power transferred and the power conversion efficiency for each phase of a winding through which a current flows. [Figure 20] 4 is a flowchart showing a processing procedure of energy management control. [Figure 21] FIG. 11 is a functional block diagram of a temperature rise control according to a third embodiment. [Figure 22] FIG. 4 is a diagram showing a method for setting a neutral point command current. [Figure 23] FIG. 13 is a diagram showing a method for calculating a droop coefficient. [Figure 24] 4 is a flowchart showing a procedure for temperature rise control. [Diagram 25] 4 is a time chart showing an example of temperature rise control. [Figure 26] 4 is a time chart showing an example of temperature rise control. [Figure 27] FIG. 13 is a functional block diagram of a temperature rise control according to a modified example of the third embodiment. [Figure 28] FIG. 13 is a configuration diagram of a power conversion system in which the number of phases of the rotating electric machine and the switching device unit is five. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] First Embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a power conversion device according to the present invention will now be described with reference to the drawings. The power conversion system of this embodiment is mounted on, for example, an electric vehicle or a hybrid vehicle.

[0022] As shown in Fig. 1, the power conversion system 10 includes a power conversion device 11. The power conversion device 11 includes an inverter 30 and a rotating electric machine 40. The rotating electric 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. The phase windings 41U, 41V, and 41W are arranged with an electrical angle of 120° between them. The rotating electric machine 40 is, for example, a permanent magnet synchronous machine. In this embodiment, the rotating electric machine 40 is an in-vehicle main engine, and serves as a power source for running the vehicle.

[0023] The inverter 30 includes a switching device section 31. The switching device section 31 includes three phases of series-connected upper arm switches QUH, QVH, and QWH and lower arm switches QUL, QVL, and QWL. In this embodiment, a voltage-controlled semiconductor switching element is used as each of the switches QUH, QVH, QWH, QUL, QVL, and QWL, and specifically, an IGBT is used. For this reason, the high-potential side terminal of each of the switches QUH, QVH, QWH, QUL, QVL, and QWL is a collector, and the low-potential side terminal is an emitter. The switches QUH, QVH, QWH, QUL, QVL, and QWL are connected in inverse parallel to the diodes DUH, DVH, DWH, DUL, DVL, and DWL as freewheel diodes.

[0024] A 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 33U such as a bus bar. A 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 33V such as a bus bar. A 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 33W such as a bus bar. Second ends of the U-, V-, and W-phase windings 41U, 41V, and 41W are connected to each other at a 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, for example, the inductance of each phase winding 41U, 41V, and 41W is set to be the same.

[0025] 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 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 Ln such as a bus bar.

[0026] The power conversion device 11 includes a capacitor 32 that connects the positive bus bar Lp and the negative bus bar Ln. The capacitor 32 may be built in the inverter 30 or may be provided outside the inverter 30.

[0027] The battery pack 20 is configured as a series connection of battery cells acting as single batteries, and has a terminal voltage of, for example, several hundred volts. 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. For example, secondary batteries such as lithium ion batteries can be used as the battery cells.

[0028] In this embodiment, among the battery cells constituting the battery pack 20, a series connection of multiple battery cells on the high potential side constitutes the first storage battery 21, and a series connection of multiple battery cells on the low potential side constitutes the second storage battery 22. That is, 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. The first storage battery 21 corresponds to the "first power storage unit" and the second storage battery 22 corresponds to the "second power storage unit."

[0029] In the battery pack 20, an intermediate terminal B is connected to the negative terminal of the first storage battery 21 and the positive terminal of the second storage battery 22.

[0030] The power conversion device 11 includes a connection path 60 and a connection switch 61. The connection path 60 electrically connects the intermediate terminal B and the neutral point O of the battery pack 20. 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 intermediate terminal B and the neutral point O are electrically disconnected.

[0031] The power conversion system 10 includes a monitoring unit 50. The monitoring unit 50 detects the terminal voltage, SOC, and temperature of each battery cell that constitutes the battery pack 20, and monitors the state of each battery cell. Battery information including the terminal voltage, SOC, and temperature of each battery cell detected by the monitoring unit 50 is input to a control device 70 included in the inverter 30.

[0032] The power conversion system 10 includes a current sensor 62 and a phase current sensor 63. The current sensor 62 detects a neutral point current IMr, which is a current flowing through the connection path 60. The detection value of the current sensor 62 is input to the control device 70. The phase current sensor 63 detects phase currents for at least two phases. The phase current sensor 63 detects, for example, currents flowing through conductive members for at least two phases among the conductive members 32U to 32W. The detected current Ir of the phase current sensor 63 is input to the control device 70.

[0033] The power conversion system 10 includes an air pressure sensor 51. The air pressure sensor 51 detects the air pressure around the rotary electric machine 40. The air pressure detection value Pr of the air pressure sensor 51 is input to the control device .

[0034] The power conversion system 10 includes a temperature sensor 52. The temperature sensor 52 detects the temperature of at least one of the windings 41U, 41V, and 41W or the temperature of its peripheral configuration. The detected temperature Tr of the temperature sensor 52 is input to the control device 70.

[0035] The control device 70 is mainly configured with a microcomputer, and performs switch drive control to turn on and off the switches QUH to QWL of the switching device unit 31 in order to feedback control the control amount of the rotating electric machine 40 to a command value. For example, the control amount is torque, and the command value is a torque command value Trq* output from the upper control device 53. In each phase, the upper arm switch and the lower arm switch are alternately turned on.

[0036] The control device 70 executes programs stored in its own storage device to realize various control functions. The various functions may be realized by electronic circuits, which are hardware, or may be realized by both hardware and software. The control device 70 corresponds to the "control unit."

[0037] Next, partial discharges occurring in the respective phase windings 41U, 41V, and 41W during switch drive control will be described. Here, a winding of any one of the U-, V-, and W-phase windings 41U, 41V, and 41W is defined as an in-phase winding 41a. The in-phase winding 41a has a conductor 41b, and the outside of the conductor 41b is covered with an insulating layer 41c. The insulating layer 41c is made of an electrically insulating material, such as synthetic resin. FIG. 2 is a cross-sectional view of the in-phase windings 41a arranged adjacent to each other and in contact with each other's insulating layers 41c. When the winding voltage, which is the potential difference between the adjacent in-phase windings 41a, becomes high, partial discharges occur between the adjacent in-phase windings 41a. When the winding voltage becomes higher than a partial discharge inception voltage (PDIV), partial discharges occur or the possibility of partial discharges occurring becomes extremely high.

[0038] Partial discharges are more likely to occur as the partial discharge inception voltage is lower. The lower the air density, the lower the partial discharge inception voltage. The air density becomes lower as the air pressure around the rotating electric machine 40 becomes lower or the temperature of the in-phase winding 41a becomes higher. For this reason, as shown in Fig. 3, the partial discharge inception voltage becomes lower as the air pressure around the rotating electric machine 40 becomes lower or the temperature of the in-phase winding 41a becomes higher.

[0039] Partial discharges are more likely to occur as the winding voltage increases, and the amount of partial discharges is more likely to increase as the difference between the winding voltage and the partial discharge inception voltage increases. The higher the terminal voltage of each of the storage batteries 21, 22, which is the voltage supplied to the switching device unit 31, the higher the output voltage of the switching device unit 31. Therefore, as shown in FIG. 4, the higher the terminal voltage of each of the storage batteries 21, 22, the higher the winding voltage becomes. In addition, the surge voltage generated when each of the switches QUH to QWL is turned off becomes higher as the phase current flowing through the common-phase winding 41a becomes larger. When the surge voltage propagates to the rotating electric machine 40, the winding voltage of the common-phase winding 41a momentarily increases. Therefore, as shown in FIG. 4, the winding voltage becomes higher as the phase current flowing through the common-phase winding 41a becomes larger.

[0040] Next, the winding voltage of the in-phase winding 41a generated when the switch drive control is performed will be described. The switch drive control is usually performed with the connection switch 61 turned off. Fig. 5 is a diagram for explaining the maximum value Vm of the winding voltage generated in the in-phase winding 41a with the connection switch 61 turned off. In Fig. 5, the switches QUH, QVH, QWH, QUL, QVL, and QWL, the connection path 60, and the connection switch 61 are not shown, and the same components as those in Fig. 1 are denoted by the same reference numerals for convenience.

[0041] In the case where the three-phase winding is switch-driven, one of the positive terminal of the first storage battery 21 and the negative terminal of the second storage battery 22 is connected to the in-phase winding 41a for one phase, and the in-phase winding 41a for two phases is connected to the other. Fig. 5 shows an example in which the in-phase winding 41a for one phase is connected to the positive terminal of the first storage battery 21, and the in-phase winding 41a for two phases is connected to the negative terminal of the second storage battery 22. In this case, the maximum value Vm of the winding voltage generated in the in-phase winding 41a for one phase is the divided value 2 / 3 x Vdc ​​of the terminal voltage of the assembled battery 20. Here, Vdc indicates the power supply voltage, i.e., the terminal voltage of the assembled battery 20. Since the maximum value Vm of the winding voltage generated in the in-phase winding 41a for one phase is higher than the maximum value 1 / 3×Vdc of the winding voltage generated in the in-phase winding 41a for two phases connected in parallel, partial discharges are likely to occur in the in-phase winding 41a for one phase, and the amount of partial discharge is likely to become large.

[0042] If the actual partial discharge amount becomes larger than the allowable value of the partial discharge amount of the in-phase winding 41a, the insulating layer 41c of the in-phase winding 41a may be deteriorated. In order to address this problem, it is conceivable to set the insulation distance of the in-phase winding 41a to be long in order to ensure the desired insulation performance. In this case, however, there is a concern that the rotating electric machine 40 will become large in size.

[0043] Therefore, in this embodiment, the insulation performance of the in-phase winding 41a is ensured by controlling the connection switch 61. More specifically, the switch drive control is performed when the connection switch 61 is in the on state. Fig. 6 is a diagram for explaining the winding voltage generated in the in-phase winding 41a when the connection switch 61 is in the on state. In Fig. 6, the switches QUH, QVH, QWH, QUL, QVL, and QWL and the connection switch 61 are not shown, and the same components as those in Fig. 1 are denoted by the same reference numerals for convenience.

[0044] When the connection switch 61 is in an on state, the neutral point O and the intermediate terminal B of the battery pack 20 are electrically connected. Therefore, when switch drive control is performed, one end of the in-phase winding 41a for one phase is connected to either the positive terminal of the first storage battery 21 or the negative terminal of the second storage battery 22, and the other end is connected to the intermediate terminal B. Therefore, the winding voltage generated in the in-phase winding 41a for one phase becomes the terminal voltage of the first storage battery 21 or the terminal voltage of the second storage battery 22.

[0045] 6 shows a case where the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22 are both 1 / 2×Vdc. In this case, the maximum winding voltage Vm with the connection switch 61 turned off is 2 / 3×Vdc, whereas the maximum winding voltage Vm with the connection switch 61 turned on can be reduced to 1 / 2×Vdc.

[0046] The terminal voltage of the first storage battery 21 and the terminal voltage (for example, rated voltage) of the second storage battery 22 are desirably set to the same or equivalent values, but may be different values.

[0047] The control device 70 determines whether or not the amount of partial discharge occurring in the in-phase winding 41a is greater than an allowable value based on the air pressure detection value Pr of the air pressure sensor 51, the temperature detection value Tr of the temperature sensor 52, the current detection value Ir of the phase current sensor 63, and the terminal voltage Vr of the battery pack 20. In this embodiment, the process of determining whether or not partial discharge occurs in the in-phase winding 41a is performed as the process of determining whether or not the amount of partial discharge occurring in the in-phase winding 41a is greater than an allowable value. Specifically, the control device 70 determines that partial discharge occurs in the in-phase winding 41a when it is determined that at least one of the following first to fourth conditions is satisfied.

[0048] The first condition is that the air pressure detection value Pr detected by the air pressure sensor 51 is equal to or smaller than the air pressure determination value Pth.

[0049] The second condition is that the detected temperature Tr of the temperature sensor 52 is equal to or higher than the temperature judgment value Tth.

[0050] The third condition is that the absolute value of the current Ir detected by the phase current sensor 63 is equal to or greater than the current determination value Ith. The current Ir detected by the phase current sensor 63 corresponds to the "current parameter."

[0051] The fourth condition is that the terminal voltage Vr of the battery pack 20 is equal to or higher than the voltage determination value Vdcth. The terminal voltage Vr of the battery pack 20 may be acquired based on the battery information of the monitoring unit 50. The terminal voltage Vr of the battery pack 20 acquired from the monitoring unit 50 corresponds to the “voltage parameter”.

[0052] When it is determined that a partial discharge occurs, the control device 70 turns on the connection switch 61. The control device 70 corresponds to a "determination unit."

[0053] 7 shows a procedure for the control process performed by the control device 70. This control process is repeatedly performed at a predetermined control period.

[0054] In step S10, it is determined whether or not there is a request to drive the rotating electric machine 40. In this embodiment, this drive request includes a request to run the vehicle by rotationally driving the rotating electric machine 40. If a negative determination is made in step S10, the process proceeds to step S11.

[0055] In step S11, a standby mode is set. By setting the standby mode, the switches QUH to QWL of the switching device unit 31 are turned off. Then, in step S12, the connection switch 61 is turned off. As a result, the intermediate terminal B and the neutral point O are electrically disconnected.

[0056] If the determination in step S10 is positive, the process proceeds to step S13. In step S13, it is determined whether or not a partial discharge occurs in the in-phase winding 41a. Specifically, the atmospheric pressure detection value Pr, the detected temperature Tr, the detected current Ir, and the terminal voltage Vr are acquired. Then, it is determined whether or not at least one of the above-mentioned first to fourth conditions is satisfied. If the determination in step S13 is negative, the process proceeds to step S14. Note that step S13 corresponds to the "atmospheric pressure information acquisition unit", the "temperature acquisition unit", the "current acquisition unit", and the "voltage acquisition unit".

[0057] In step S14, a normal mode in which switch drive control is performed is set. Then, in step S15, the connection switch 61 is turned off. This electrically disconnects the intermediate terminal B from the neutral point O. In step S16, with the connection switch 61 turned off, the upper and lower arm switches QUH to QWL of each phase are turned on and off. Specifically, for example, a switch operation signal (duty signal) for the upper and lower arm switches in each phase is generated by PWM control based on a magnitude comparison between a signal in which the command voltage of each phase is normalized by the power supply voltage Vdc and a carrier signal such as a triangular wave signal.

[0058] On the other hand, if the determination in step S13 is affirmative, the process proceeds to step S17. In step S17, an insulation protection mode is set in which switch drive control is performed while insulation protection is performed for the in-phase winding 41a. Then, in step S18, the connection switch 61 is turned on. This electrically connects the intermediate terminal B and the neutral point O. In step S19, with the connection switch 61 turned on, the upper and lower arm switches QUH to QWL of each phase are turned on and off. Specifically, the same PWM control as in step S16 is performed.

[0059] Fig. 8 shows an example of switch drive control in which the connection switch 61 is controlled based on the air pressure detection value Pr of the air pressure sensor 51. Fig. 8 shows the relationship between the air pressure detection value Pr and the maximum winding voltage Vm of the in-phase winding 41a and the partial discharge inception voltage PDIV. In Fig. 8, the solid line indicates the maximum winding voltage Vm, and the dashed line indicates the partial discharge inception voltage PDIV. When the maximum winding voltage Vm is lower than the partial discharge inception voltage PDIV, this indicates that partial discharge will not occur or that the possibility of partial discharge occurring is extremely low, and when the maximum winding voltage Vm is equal to or greater than the partial discharge inception voltage PDIV, this indicates that partial discharge will occur or that the possibility of partial discharge occurring is extremely high.

[0060] In an area where the atmospheric pressure detection value Pr is higher than the atmospheric pressure determination value Pth, the connection switch 61 is turned off, and the partial discharge inception voltage PDIV becomes higher than 2 / 3×Vdc, which is the maximum winding voltage Vm when the connection switch 61 is turned off. In this case, even if switch drive control is performed, partial discharge does not occur or the possibility of partial discharge occurring is extremely low. In Fig. 8, the atmospheric pressure detection value Pr around the rotating electric machine 40 when the partial discharge inception voltage PDIV is the same value as 2 / 3×Vdc is set as the atmospheric pressure determination value Pth.

[0061] On the other hand, in the region where the atmospheric pressure detection value Pr is equal to or less than the atmospheric pressure determination value Pth, the partial discharge inception voltage PDIV is equal to or less than 2 / 3×Vdc, which is the maximum value Vm of the winding voltage when the connection switch 61 is turned off. Therefore, when the connection switch 61 is turned off, there is a concern that partial discharge may occur in the in-phase winding 41a. Therefore, in the region where the atmospheric pressure detection value Pr is equal to or less than the atmospheric pressure determination value Pth, the control device 70 determines that the first condition is satisfied and turns on the connection switch 61. This makes it possible to reduce the maximum value Vm of the winding voltage generated in the in-phase winding 41a when switch drive control is performed to 1 / 2×Vdc, which is lower than the partial discharge inception voltage PDIV. As a result, even in the region where the atmospheric pressure detection value Pr is equal to or less than the atmospheric pressure determination value Pth, partial discharge may be suppressed from occurring in the in-phase winding 41a when switch drive control is performed.

[0062] When the connection switch 61 is controlled based on the detected temperature Tr of the temperature sensor 52, the same control as when the connection switch 61 is controlled based on the air pressure detection value Pr of the air pressure sensor 51 is performed. In detail, in a region where the detected temperature Tr is lower than the temperature judgment value Tth, the partial discharge inception voltage PDIV is higher than 2 / 3×Vdc, which is the maximum value Vm of the winding voltage, so that even if the switch drive control is performed with the connection switch 61 turned off, partial discharge does not occur. On the other hand, in a region where the detected temperature Tr is equal to or higher than the temperature judgment value Tth, the partial discharge inception voltage PDIV is equal to or lower than 2 / 3×Vdc, which is the maximum value Vm of the winding voltage. Therefore, in a region where the detected temperature Tr is equal to or higher than the temperature judgment value Tth, the control device 70 determines that the second condition is satisfied and turns on the connection switch 61. The control device 70 performs the switch drive control with the connection switch 61 turned on, thereby suppressing the occurrence of partial discharge.

[0063] When the absolute value of the detected current Ir of the phase current sensor 63 is smaller than the current determination value Ith, the control device 70 performs switch drive control with the connection switch 61 in the OFF state. On the other hand, when the absolute value of the detected current Ir of the phase current sensor 63 is equal to or larger than the current determination value Ith, the control device 70 determines that the third condition is satisfied and turns on the connection switch 61. The control device 70 performs switch drive control with the connection switch 61 in the ON state.

[0064] When the terminal voltage Vr of the battery pack 20 is lower than the voltage determination value Vdcth, the control device 70 performs switch drive control with the connection switch 61 in an OFF state. When the terminal voltage Vr of the battery pack 20 is equal to or higher than the voltage determination value Vdcth, the control device 70 determines that the fourth condition is met and turns on the connection switch 61. The control device 70 performs switch drive control with the connection switch 61 in an ON state.

[0065] The control device 70 may set each of the determination values ​​Pth, Tth, Ith, and Vdcth based on the detected air pressure value Pr, the detected temperature Tr, the detected current Ir, and the terminal voltage Vr of the battery pack 20, for example.

[0066] In detail, the control device 70 may set the air pressure determination value Pth using correspondence information (e.g., map information or formula information) in which at least one of the detected temperature Tr, the detected current Ir, and the terminal voltage Vr of the assembled battery 20 is previously associated with the air pressure determination value Pth that can reduce the amount of partial discharge to the allowable value or less. The control device 70 may set the temperature determination value Tth using correspondence information in which at least one of the detected air pressure value Pr, the detected current Ir, and the terminal voltage Vr of the assembled battery 20 is previously associated with the temperature determination value Tth that can reduce the amount of partial discharge to the allowable value or less.

[0067] The control device 70 may set the current determination value Ith using correspondence information in which at least one of the atmospheric pressure detection value Pr, the detected temperature Tr, and the terminal voltage Vr of the battery pack 20 is previously associated with the current determination value Ith that can reduce the amount of partial discharge to the allowable value or less. The control device 70 may set the voltage determination value Vdcth using correspondence information in which at least one of the atmospheric pressure detection value Pr, the detected temperature Tr, and the detected current Ir is previously associated with the voltage determination value Vdcth that can reduce the amount of partial discharge to the allowable value or less. When partial discharge is not permitted, the allowable value is set to, for example, 0, and when partial discharge is permitted, the allowable value is set to a value greater than 0.

[0068] According to the present embodiment described above in detail, the following effects can be obtained.

[0069] The power conversion device 11 includes a connection path 60 that electrically connects the negative terminal of the first storage battery 21 and the positive terminal of the second storage battery 22 to a neutral point O, a connection switch 61 provided on the connection path 60, and a control device 70. The control device 70 determines whether or not at least one of the first to fourth conditions is satisfied. If it is determined that at least one of the first to fourth conditions is satisfied, it is determined that a partial discharge has occurred, and the connection switch 61 is turned on.

[0070] In the above-described configuration, when the connection switch 61 is in an OFF state, the divided voltage value of the terminal voltage of the battery pack 20 is applied to the in-phase winding 41a in the switch drive control. In this case, the maximum value Vm of the winding voltage is 2 / 3×Vdc. On the other hand, when the connection switch 61 is in an ON state, a voltage equivalent to the terminal voltage of the first storage battery 21 or the terminal voltage of the second storage battery 22 is applied to the in-phase winding 41a. If the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22 are the same, the maximum value Vm of the winding voltage is 1 / 2×Vdc. Therefore, by performing the switch drive control with the connection switch 61 in an ON state, the maximum value Vm of the winding voltage generated in the in-phase winding 41a can be reduced more than when the switch drive control is performed with the connection switch 61 in an OFF state. As a result, the occurrence of partial discharge can be suppressed by utilizing the switching device unit 31 and the rotating electric machine 40. As a result, the insulation distance of the in-phase winding 41a can be set short, and the rotating electric machine 40 can be made smaller in size.

[0071] Unlike the present embodiment, it is conceivable to reduce the winding voltage and suppress the occurrence of partial discharge by stepping down the terminal voltage of the battery pack 20 and supplying it to the switching device unit 31. However, in this case, there is a concern that the output of the rotating electric machine 40 in the switch drive control will decrease. In contrast, in the present embodiment, the switch drive control is performed with the connection switch 61 in an on state, so that the maximum value Vm of the winding voltage can be reduced. This makes it possible to suppress a decrease in the output of the rotating electric machine 40 in the switch drive control.

[0072] The air pressure detection value Pr of the air pressure sensor 51 is acquired. The lower the air pressure around the rotating electric machine 40, the lower the partial discharge inception voltage becomes, and the more likely partial discharge occurs. Therefore, based on the acquired air pressure detection value Pr, it is possible to accurately determine the state in which the connection switch 61 should be turned on.

[0073] The temperature Tr detected by the temperature sensor 52 is acquired. The higher the temperature of the in-phase winding 41a, the lower the partial discharge inception voltage, making it easier for partial discharge to occur. Therefore, based on the temperature Tr detected by the temperature sensor 52, it is possible to accurately determine the state in which the connection switch 61 should be turned on.

[0074] The detected current Ir of the phase current sensor 63 is acquired. In a situation where the phase current flowing through the same-phase winding 41a is large, the surge voltage generated by turning off each of the switches QUH to QWL becomes high, and the maximum winding voltage Vm also becomes high. As a result, partial discharge becomes more likely to occur. Therefore, based on the detected current Ir of the phase current sensor 63, it is possible to accurately determine the state in which the connection switch 61 should be turned on.

[0075] The terminal voltage Vr of the battery pack 20 is acquired from the monitoring unit 50. When the terminal voltage Vr of the battery pack 20 is high, the output voltage of the switching device section 31 is high. This increases the maximum winding voltage Vm, making partial discharge more likely to occur. Therefore, it is possible to accurately determine the state in which the connection switch 61 should be turned on based on the acquired terminal voltage Vr of the battery pack 20.

[0076] <Modification of the first embodiment> The power conversion system 10 may include an altitude sensor that acquires altitude instead of the air pressure sensor 51. Altitude information detected by the altitude sensor is input to the control device 70. The control device 70 acquires a detected air pressure value Pr around the rotating electrical machine 40 based on the altitude information.

[0077] In the third condition, instead of determining whether the detected current Ir of the phase current sensor 63 is greater than the current determination value Ith, it may be determined whether the torque command value Trq* output from the upper control device 53 is greater than the torque determination value Trqth. In this case, the control device 70 acquires the torque command value Trq*, and when the torque command value Trq* is greater than the torque determination value Trqth, determines that the third condition is satisfied.

[0078] When the torque command value Trq* is large, the phase current flowing through the in-phase winding 41a also becomes large, so that the surge voltage generated by turning off each switch QUH to QWL becomes high, and the winding voltage becomes high. As a result, partial discharge is likely to occur. Therefore, it is possible to accurately determine the state in which the connection switch 61 should be turned on based on the acquired torque command value Trq*.

[0079] In the third condition, instead of the torque command value Trq*, it may be determined whether the magnitude of a command current vector determined corresponding to the d- and q-axis command currents is greater than a predetermined value. In this case, the control device 70 acquires the command current vector, and determines that the third condition is met if the magnitude of the command current vector is greater than a predetermined value. The torque command value Trq* and the magnitude of the command current vector correspond to the "current parameter."

[0080] The recovery surge voltage generated when each of the switches QUH to QWL is turned on becomes higher as the phase current flowing through the in-phase winding 41a becomes smaller. This may cause the winding voltage of the in-phase winding 41a to momentarily increase.

[0081] Therefore, instead of the condition for determining whether the absolute value of the detected current Ir of the phase current sensor 63 is equal to or less than the current determination value Ith, the third condition may be a condition for determining whether the absolute value of the detected current Ir of the phase current sensor 63 is equal to or less than the small current determination value. In this case, the control device 70 may determine that the third condition is satisfied when the detected current Ir of the phase current sensor 63 is equal to or less than the small current determination value.

[0082] The fourth condition may be a condition for determining whether the SOC of the battery pack 20 is greater than the capacity judgment value SOCth, instead of a condition for determining whether the acquired terminal voltage Vr of the battery pack 20 is higher than the voltage judgment value Vdcth. In this case, the control device 70 acquires the SOC from the monitoring unit 50, and when the acquired SOC of the battery pack 20 is greater than the capacity judgment value SOCth, determines that the fourth condition is met. The SOC acquired from the monitoring unit 50 corresponds to the "voltage parameter."

[0083] When the SOC of the battery pack 20 is high, the terminal voltage of the battery pack 20 becomes high. Therefore, the output voltage of the switching device unit 31 becomes high, and the maximum winding voltage Vm also becomes high. As a result, partial discharge becomes more likely to occur. Therefore, it is possible to accurately determine the state in which the connection switch 61 should be turned on based on the acquired SOC of the battery pack 20.

[0084] The location of the intermediate terminal B may be changed. As shown in Fig. 9, the power conversion device 11 includes a first capacitor 32a and a second capacitor 32b having the same capacitance. In Fig. 9, the same components as those shown in Fig. 1 are denoted by the same reference numerals for convenience. Note that the capacitance of the first capacitor 32a and the capacitance of the second capacitor 32b do not have to be the same.

[0085] A first end of the first capacitor 32a is connected to the positive bus bar Lp, and a first end of the second capacitor 32b is connected to the negative bus bar Ln. An intermediate terminal B is connected to a second end of the first capacitor 32a and a second end of the second capacitor 32b. The first capacitor 32a corresponds to a "first power storage unit," and the second capacitor 32b corresponds to a "second power storage unit."

[0086] In the first embodiment, the power conversion system 10 may include a series connection of different types of power storage units instead of the battery pack 20. As shown in Fig. 10, the power conversion system 10 includes a power source 23. In Fig. 10, the same components as those shown in Fig. 1 are denoted by the same reference numerals for convenience.

[0087] The power source 23 has a first storage battery 21 and a capacitor 24 instead of the second storage battery 22. The positive terminal of the storage battery 21 is connected to a positive bus bar Lp, and the negative terminal of the capacitor 24 is connected to a negative bus bar Ln. An intermediate terminal B is connected to the negative terminal of the storage battery 21 and the positive terminal of the capacitor 24. The power source 23 may include the capacitor 24 instead of the first storage battery 21 and the second storage battery 22. Here, it is preferable that a supercapacitor having a large electrostatic capacity is used as the capacitor 24. In this embodiment, the capacitor 24 corresponds to the "second power storage unit."

[0088] <Second embodiment> Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the control device 70 performs energy management control for transferring energy between the first storage battery 21 and the second storage battery 22.

[0089] The energy management control performed when the connection switch 61 is turned on will now be described.

[0090] Fig. 11(a) shows an equivalent circuit of the power conversion system 10 used in the energy management control. In Fig. 11(a), each phase winding 41U-41W is shown as a winding 41, each upper arm switch QUH, QVH, QWH is shown as an upper arm switch QH, and each upper arm diode DUH, DVH, DWH is shown as an upper arm diode DH. In addition, each lower arm switch QUL, QVL, QWL is shown as a lower arm switch QL, and each lower arm diode DUL, DVL, DWL is shown as a lower arm diode DL.

[0091] The equivalent circuit of FIG. 11(a) can be shown as the equivalent circuit of FIG. 11(b). The circuit of FIG. 11(b) is a step-up / step-down chopper circuit capable of bidirectional power transmission between the first storage battery 21 and the second storage battery 22. In FIG. 11(b), IBH indicates a current flowing through the first storage battery 21, and IBL indicates a current flowing through the second storage battery 22. When a charging current flows through the first and second storage batteries 21 and 22, IBH and IBL are negative, and when a discharging current flows through the first and second storage batteries 21 and 22, IBH and IBL are positive. In addition, VR indicates the terminal voltage of the winding 41, and IMr indicates the neutral point current. The neutral point current IMr is positive when it flows from the winding 41 to the intermediate terminal B, and negative when it flows in the opposite direction.

[0092] 11(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." In other words, when the upper arm switch QH is turned on, an excitation current can be caused to flow in the positive direction through the winding 41, and when the lower arm switch QL is turned on, an excitation current can be caused to flow in the negative direction through the winding 41.

[0093] A block diagram of the energy management control is shown in Fig. 12. Fig. 12 is a control block diagram of the energy management control that is performed while the vehicle is stopped before the rotating electric machine 40 is driven.

[0094] The control device 70 includes an energy control unit 90. The energy control unit 90 includes a command value setting unit 91, a neutral point deviation calculation unit 92, a neutral point control unit 93, and U- to W-phase superimposing units 94U to 94W.

[0095] The command value setting unit 91 sets the neutral point command current IM*. In this embodiment, the command value setting unit 91 calculates the judgment voltage Vj (=VBH-VBL) by subtracting the terminal voltage VBL of the second storage battery 22 from the terminal voltage VBH of the first storage battery 21. When the calculated judgment voltage Vj is a positive value, the command value setting unit 91 sets the neutral point command current IM* to a positive value. More specifically, as shown in FIG. 13, the higher the judgment voltage Vj is, the larger the neutral point command current IM* is set. When the calculated judgment voltage Vj is a negative value, the command value setting unit 91 sets the neutral point command current IM* to a negative value, more specifically, the larger the absolute value of the judgment voltage Vj is, the larger the absolute value of the neutral point command current IM* is set. Therefore, in this embodiment, energy management control is performed with the aim of equalizing the terminal voltages of the first storage battery 21 and the second storage battery 22.

[0096] The neutral point deviation calculation unit 92 calculates the neutral point current deviation ΔIM by subtracting the neutral point current IMr, which is the current detected by the current sensor 62, from the neutral point command current IM*. In this embodiment, the neutral point command current IM* is a DC current.

[0097] The neutral point control unit 93 calculates an offset correction amount CF as an operation amount for feedback controlling the calculated neutral point current deviation ΔIM to 0. In this embodiment, proportional integral control is used as this feedback control. Note that the feedback control is not limited to proportional integral control, and may be, for example, proportional integral derivative control.

[0098] The U-phase superimposing unit 94U calculates a U-phase final command voltage "Vu+CF" by adding an offset correction amount CF to the U-phase command voltage Vu. The V-phase superimposing unit 94V calculates a V-phase final command voltage "Vv+CF" by adding an offset correction amount CF to the V-phase command voltage Vv. The W-phase superimposing unit 94W calculates a W-phase final command voltage "Vw+CF" by adding an offset correction amount CF to the W-phase command voltage Vw. In the process of FIG. 12, since the vehicle is stopped, the command voltages Vu, Vv, and Vw of each phase are set to 0. Therefore, the final command voltage of each phase becomes the offset correction amount CF.

[0099] The control device 70 includes U-phase to W-phase modulation units 95U to 95W. The U-phase modulation unit 95U calculates a U-phase modulation factor Mu by dividing the U-phase final command voltage by the power supply voltage Vdc. Here, the power supply voltage Vdc is the sum of the terminal voltage VBH of the first storage battery 21 and the terminal voltage VBL of the second storage battery 22 acquired from the monitoring unit 50. The V-phase modulation unit 95V calculates a V-phase modulation factor Mv by dividing the V-phase final command voltage by the power supply voltage Vdc. The W-phase modulation unit 95W calculates a W-phase modulation factor Mw by dividing the W-phase final command voltage by the power supply voltage Vdc.

[0100] The control device 70 performs switching control of the three-phase switches QUH to QWL based on the calculated modulation factors Mu, Mv, and Mw. Specifically, for example, the control device 70 may perform switching control by PWM control based on a magnitude comparison between each of the modulation factors Mu, Mv, and Mw and a carrier signal (e.g., a triangular wave signal).

[0101] The energy management control can be performed not only when the vehicle is stopped but also when the vehicle is moving. Fig. 14 is a control block diagram of the energy management control performed in this case. In Fig. 14, the same components as those shown in Fig. 12 are denoted by the same reference numerals for convenience.

[0102] The control device 70 includes d-axis and q-axis deviation calculation units 100d and 100q, d-axis and q-axis control units 101d and 101q, and a three-phase conversion unit 102.

[0103] In the control device 70, a d-axis deviation calculation unit 100d calculates a d-axis current deviation ΔId by subtracting a d-axis current Idr from a d-axis command current Id*. A q-axis deviation calculation unit 100q calculates a q-axis current deviation ΔIq by subtracting a q-axis current Iqr from a q-axis command current Iq*. Here, the d-axis command current Id* and the q-axis command current Iq* are set based on a torque command value Trq* of the rotating electric machine 40. In addition, the d-axis current Idr and the q-axis current Iqr are calculated based on a detected current Ir of the phase current sensor 63 and an electrical angle of the rotating electric machine 40. Note that the electrical angle may be a detected value of a rotation angle sensor such as a resolver, or may be an estimated value estimated by position sensorless control.

[0104] The d-axis control unit 101d calculates a d-axis voltage Vd as an operation amount for feedback controlling the calculated d-axis current deviation ΔId to 0. The q-axis control unit 101q calculates a q-axis voltage Vq as an operation amount for feedback controlling the calculated q-axis current deviation ΔIq to 0. In this embodiment, proportional integral control is used as the feedback control of each of the control units 101d and 101q. Note that the feedback control is not limited to proportional integral control, and may be, for example, proportional integral derivative control.

[0105] The three-phase conversion unit 102 calculates U-W phase command voltages Vu-Vw in a three-phase fixed coordinate system based on the d-axis voltage Vd, the q-axis voltage Vq, and the electrical angle. The phase command voltages Vu-Vw are signals (specifically, sinusoidal signals) whose phases are shifted by 120 electrical degrees. An offset correction amount CF is added to the U-W phase command voltages Vu-Vw calculated by the three-phase conversion unit 102 in the U-W phase superimposing units 94U-94W. As a result, the U-W phase final command voltages are calculated.

[0106] With the above-described configuration, energy is exchanged between the first storage battery 21 and the second storage battery 22. In detail, when the neutral point command current IM* is positive, energy is supplied from the first storage battery 21 to the second storage battery 22, and when the neutral point command current IM* is negative, energy is supplied from the second storage battery 22 to the first storage battery 21.

[0107] In the energy management control, it is desirable that the power conversion efficiency, which is the ratio between the output energy of the storage battery on the energy supply side and the input energy of the storage battery on the energy supply side, is high, in other words, that the loss of the energy exchanged is low. Therefore, in this embodiment, the control device 70 is provided with a configuration that enhances the power conversion efficiency of the energy management control.

[0108] Energy loss occurring in the energy management control includes iron loss occurring in the rotating electric machine 40. It is known that iron loss occurs due to the ripple current Irip. More specifically, iron loss increases in proportion to the square of the ripple current Irip. The ripple current Irip in this embodiment is the fluctuation range of the neutral point current IMr that occurs with the on / off of each switch QUH to QWL, as shown in FIG. 15. The ripple current Irip is expressed by the following formula (e1).

[0109]

number

[0110] In order to reduce iron loss in the energy management control, the control device 70 supplies energy from one of the storage batteries 21, 22 to the other on the condition that the higher terminal voltage VB of the storage batteries 21, 22 is equal to or lower than a voltage specification value Vp. The terminal voltage VB of the storage battery corresponds to the "voltage parameter."

[0111] For example, the voltage specified value Vp is set by taking into consideration that the terminal voltage VB of the storage battery is low in a low SOC state in which the SOC of each storage battery 21, 22 is low. FIG. 16 shows the relationship between the terminal voltage VB of the storage battery and the SOC. There is a correlation between the terminal voltage VB of the storage battery and the SOC, and the voltage change amount, which is the change amount of the terminal voltage VB per unit change amount of the SOC of the storage battery, changes according to the magnitude of the SOC, and there is a region where the voltage change amount is large and a region where the voltage change amount is small. If the SOC of the storage battery drops to the region where the voltage change amount is large, deterioration of the storage battery may occur. In consideration of this, for example, a value of SOC slightly larger than the lower limit value of the region where the voltage change amount is small may be set as the SOC specified value Sp, and the terminal voltage VB of the storage battery corresponding to the SOC specified value Sp may be set as the voltage specified value Vp.

[0112] On the condition that the higher terminal voltage VB of the storage batteries 21, 22 is equal to or lower than the voltage specification value Vp, energy is supplied from one of the storage batteries 21, 22 to the other, thereby reducing the ripple current Irip. This makes it possible to reduce iron loss occurring in the energy management control.

[0113] The energy losses generated in the energy management control include, in addition to the iron loss generated in the rotating electric machine 40, copper loss generated in the rotating electric machine 40 and the switching device section 31, and switching losses generated in each of the switches QUH to QWL of the switching device section 31.

[0114] Here, a supplementary explanation will be given on the energy loss occurring in the energy management control. Fig. 17 shows the relationship between the energy loss and the power exchanged when energy is exchanged between the first storage battery 21 and the second storage battery 22 in the energy management control. In Fig. 17, the solid line indicates the iron loss occurring in the rotating electric machine 40, the dashed line indicates the copper loss occurring in the rotating electric machine 40 and the switching device section 31, and the dashed line indicates the switching loss occurring in each of the switches QUH to QWL of the switching device section 31.

[0115] Iron loss in the rotating electric machine 40 occurs at a substantially constant magnitude regardless of the value of the power being transmitted and received. Copper loss in the rotating electric machine 40 and the switching device unit 31 increases in proportion to the square of the power being transmitted and received. Switching loss in the switching device unit 31 increases in proportion to the power being transmitted and received.

[0116] Therefore, in this embodiment, the iron loss, copper loss, and switching loss are taken into consideration and a configuration is adopted in which the power conversion efficiency in the energy management control is increased.

[0117] Fig. 18 shows the relationship between the transmitted and received power and the power conversion efficiency when iron loss, copper loss, and switching loss are taken into consideration. The power conversion efficiency has a maximum value ηmax, and the transmitted and received power at the maximum power conversion efficiency ηmax is defined as the maximum efficient power Pmax. In a region where the transmitted and received power is greater than the maximum efficient power Pmax, copper loss and switching loss increase with increasing transmitted and received power, so the power conversion efficiency decreases as the transmitted and received power increases. On the other hand, in a region where the transmitted and received power is less than the maximum efficient power Pmax, the power conversion efficiency decreases as the transmitted and received power decreases, due to the fact that the iron loss is approximately constant regardless of the value of the transmitted and received power.

[0118] The control device 70 performs energy management control so that the power exchanged in the energy management control becomes the command power W*. The control device 70 sets the command power W* to the maximum efficiency power Pmax. Here, the maximum efficiency power Pmax is determined in advance for each phase of the windings 41 through which current flows in the energy management control.

[0119] FIG. 19 shows the relationship between the power transfer efficiency and the power conversion efficiency for each phase of the winding 41 through which the current flows in the energy management control. The solid line indicates the case where the phase number of the winding 41 through which the current flows is one phase, the dashed line indicates the case where the phase number of the winding 41 through which the current flows is two phases, and the dashed line indicates the case where the phase number of the winding 41 through which the current flows is three phases. The greater the phase number of the winding 41 through which the current flows, the greater the maximum efficiency power Pmax. In other words, the maximum efficiency power Pmax1 when the phase number of the winding 41 through which the current flows is one phase is smaller than the maximum efficiency power Pmax2 when the phase number of the winding 41 through which the current flows is two phases. Also, the maximum efficiency power Pmax2 when the phase number of the winding 41 through which the current flows is two phases is smaller than the maximum efficiency power Pmax3 when the phase number of the winding 41 through which the current flows is three phases.

[0120] 19, the control device 70 can change the number of phases of the windings 41 through which a current flows when there is no request to drive the rotating electric machine 40. In this embodiment, the control device 70 calculates the number of phases of the windings 41 through which a current flows based on the magnitude of the required power Wreq.

[0121] For example, the controller 70 calculates the required power Wreq exchanged between the first storage battery 21 and the second storage battery 22 to be larger as the difference between the terminal voltage VBH of the first storage battery 21 and the terminal voltage VBL of the second storage battery 22 increases.

[0122] The control device 70 calculates one of the maximum efficiency powers Pmax1, Pmax2, and Pmax3 as a command power W* based on the calculated required power Wreq.

[0123] In detail, when the required power Wreq is within the range of the first region DP1, the control device 70 calculates the maximum efficient power Pmax1 in the case of one phase as the command power W*. Here, the first region DP1 is a region of the power transmitted and received in which the power conversion efficiency in the case of one phase is higher than the power conversion efficiency in the case of the other number of phases. When the required power Wreq is within the range of the second region DP2, the control device 70 calculates the maximum efficient power Pmax2 in the case of two phases as the command power W*. Here, the second region DP2 is a region of the power transmitted and received in which the power conversion efficiency in the case of two phases is higher than the power conversion efficiency in the case of the other number of phases. When the required power Wreq is within the range of the third region DP3, the control device 70 calculates the maximum efficient power Pmax3 in the case of three phases as the command power W*. Here, the third region DP3 is a region of the power transmitted and received in which the power conversion efficiency in the case of three phases is higher than the power conversion efficiency in the case of the other number of phases. It should be noted that the greater the command power W*, the greater the neutral point command current IM* set by the command value setting unit 91 is.

[0124] The control device 70 performs energy management control by passing a current through the windings 41 of the number of phases corresponding to the calculated maximum efficiency power Pmax. In particular, when the maximum efficiency power Pmax3 for three phases is calculated as the command power W*, the inverter 30 performs switching control of the upper and lower arm switches for three phases so as to pass a current through the three-phase windings 41. When the maximum efficiency power Pmax2 for two phases is calculated, switching control for two phases is performed so as to pass a current through the two-phase windings 41, and the upper and lower arm switches for the remaining one phase are turned off. When the maximum efficiency power Pmax1 for one phase is calculated, switching control for one phase is performed so as to pass a current through the one-phase winding 41, and the upper and lower arm switches for the remaining two phases are turned off.

[0125] On the other hand, when there is a request to drive the rotating electric machine 40, the control device 70 calculates the maximum efficient power Pmax3 for three phases as the command power W*, and performs switching control of the upper and lower arm switches for three phases so as to pass current through the three-phase windings 41.

[0126] 20 shows a procedure for the energy management control performed by the control device 70. The energy management control is repeatedly performed at a predetermined control period.

[0127] In step S20, it is determined whether or not there is a request for energy transfer between the first storage battery 21 and the second storage battery 22. In this embodiment, when it is determined that the absolute value of the difference between the terminal voltage VBH of the first storage battery 21 and the terminal voltage VBL of the second storage battery 22 exceeds the current deviation ΔV1, it is determined that there is a request for energy transfer. Here, the terminal voltage VBH of the first storage battery 21 and the terminal voltage VBL of the second storage battery 22 may be acquired from the monitoring unit 50.

[0128] If it is determined in step S20 that there is no request for energy transfer, the process proceeds to step S21, where the standby mode is set. By setting the standby mode, the switches QUH to QWL of the switching device unit 31 are turned off. Then, in step S22, the connection switch 61 is turned off. This electrically disconnects the intermediate terminal B from the neutral point O.

[0129] If it is determined in step S20 that there is a request for energy transfer, the process proceeds to step S23. In step S23, it is determined whether the higher of the terminal voltages VBH, VBL of the storage batteries 21, 22, VB, is equal to or lower than the voltage specification value Vp. If the determination in step S23 is negative, the process proceeds to step S21. On the other hand, if the determination in step S23 is positive, the process proceeds to step S24.

[0130] In step S24, the connection switch 61 is turned on. This electrically connects the intermediate terminal B and the neutral point O. Then, in step S25, it is determined whether or not there is a request to drive the rotating electric machine 40. In this embodiment, the drive request includes a request to run the vehicle by rotationally driving the rotating electric machine 40.

[0131] If it is determined in step S25 that there is no drive request, the process proceeds to step S26. In step S26, the command power W* and the number of phases of the windings 41 through which current flows are calculated. In this embodiment, the command power W* and the number of phases of the windings 41 through which current flows are calculated based on the required power Wreq.

[0132] In step S27, a stop-time PWM control is performed to transfer energy between the first storage battery 21 and the second storage battery 22 based on the calculated command power W* and the number of phases of the winding 41. Then, the process proceeds to step S30.

[0133] On the other hand, if it is determined in step S25 that there is a drive request, the process proceeds to step S28. In step S28, a command power W* is calculated. In this embodiment, the maximum efficiency power Pmax3 in the case of three phases is calculated as the command power W*. In this embodiment, steps S26 and S28 correspond to a "power calculation unit."

[0134] In step S29, a current is passed through the three-phase windings 41 to drive the rotating electric machine 40, while performing driving PWM control in which energy is exchanged between the first storage battery 21 and the second storage battery 22 using the calculated power. Then, the process proceeds to step S30.

[0135] In step S30, it is determined whether the energy transfer is completed. In this embodiment, when it is determined that the absolute value of the difference between the terminal voltage VBH of the first storage battery 21 and the terminal voltage VBL of the second storage battery 22 is equal to or smaller than the target value ΔV2, it is determined that the energy transfer is completed.

[0136] According to the present embodiment described above in detail, the following effects can be obtained.

[0137] In the energy management control, unlike the present embodiment, a configuration may be considered in which dedicated switch elements and reactors are required for transferring energy between the storage batteries 21, 22. In this configuration, the number of components in the power conversion device 11 increases, and there is a concern that the power conversion device 11 may become larger.

[0138] In this regard, in the present embodiment, when it is determined that the higher of the terminal voltages VBH, VBL of the storage batteries 21, 22, the terminal voltage VB, is equal to or lower than the voltage specification value Vp, it is determined that the connection switch 61 is turned on. With the connection switch 61 in the on state, PWM control is performed so that a current flows between the first storage battery 21 and the second storage battery 22. As a result, energy is exchanged from one of the first storage battery 21 and the second storage battery 22 to the other. Therefore, energy can be exchanged by utilizing the winding 41 and the switching device unit 31. As a result, the power conversion device 11 can be made smaller in size.

[0139] Energy is exchanged when the terminal voltages VBH, VBL of the storage batteries 21, 22 are low. As the terminal voltages VBH, VBL of the storage batteries 21, 22 decrease, the ripple current Irip, which is the fluctuation range of the neutral point current IMr, becomes smaller. The smaller the ripple current Irip, the more the iron loss generated in the winding 41 is reduced. In view of this, energy is exchanged when the terminal voltages VBH, VBL of the storage batteries 21, 22 are low. This makes it possible to reduce the energy loss that occurs when energy is exchanged.

[0140] When it is determined that there is no request to drive the rotating electric machine 40 and the requested power Wreq is small, the number of phases of the windings 41 through which current flows is reduced. This reduces the magnetic flux passing through the iron core included in the rotating electric machine 40, thereby reducing iron loss generated in the rotating electric machine 40.

[0141] The maximum efficiency power Pmax, which is the power determined according to the number of phases of the winding 41 through which current flows and is the power at the maximum value ηmax of the power conversion efficiency, is calculated as the command power W*. Energy is exchanged between the first storage battery 21 and the second storage battery 22 based on the calculated command power W*. This makes it possible to increase the power conversion efficiency of the energy management control.

[0142] The required power Wreq increases as the difference between the terminal voltage VBH of the first storage battery 21 and the terminal voltage VBL of the second storage battery 22 increases. This makes it possible to shorten the time during which energy management control is performed.

[0143] <Modification of the second embodiment> The energy management control does not necessarily have to aim at equalizing the terminal voltages VBH, VBL of the first storage battery 21 and the second storage battery 22. In this case, for example, a determination is made as to whether or not there is a request for energy transfer from one of the first storage battery 21 and the second storage battery 22 to the other. If it is determined that there is such a request, the command value setting unit 91 may calculate an energy target value to be supplied from one of the first storage battery 21 and the second storage battery 22 to the other, and set the neutral point command current IM* based on the calculated energy target value. In detail, when energy is transferred from the first storage battery 21 to the second storage battery 22, the command value setting unit 91 calculates a positive energy target value, and sets the neutral point command current IM* to a larger value as the positive energy target value is larger. On the other hand, when energy is transferred from the second storage battery 22 to the first storage battery 21, the command value setting unit 91 calculates a negative energy target value, and sets the neutral point command current IM* to a larger value as the absolute value of the negative energy target value is larger.

[0144] The control device 70 may set the command power W* to a value other than the maximum efficiency power Pmax in the energy management control. In this case, the control device 70 may calculate the required power Wreq as the command power W* as is. The control device 70 then selects the number of phases of the windings 41 through which a current flows so that the power conversion efficiency in the energy management control is maximized for the calculated command power W*. In detail, when the command power W* is within the first region DP1, the control device 70 sets the number of phases of the windings 41 through which a current flows to one phase, when the command power W* is within the second region DP2, the control device 70 sets the number of phases of the windings 41 through which a current flows to two phases, and when the command power W* is within the third region DP3, the control device 70 sets the number of phases of the windings 41 through which a current flows to three phases.

[0145] In the above-described configuration, the number of phases of the windings 41 through which current flows is selected so that the power conversion efficiency in the energy management control is maximized for the command power W*. This makes it possible to reduce the energy loss that occurs when energy is exchanged between the first storage battery 21 and the second storage battery 22.

[0146] Instead of determining whether the higher of the terminal voltages VBH, VBL of the storage batteries 21, 22, the terminal voltage VB, is equal to or lower than the specified voltage value Vp, the control device 70 may determine whether the larger of the SOCs of the storage batteries 21, 22, is equal to or lower than the specified SOC value Sp. In this case, the control device 70 supplies energy from one of the storage batteries 21, 22 to the other, on the condition that the SOC of the storage batteries 21, 22 is equal to or lower than the specified SOC value Sp. In this embodiment, the SOC of the storage batteries corresponds to the "voltage parameter."

[0147] <Third embodiment> The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the control device 70 performs temperature rise control of the battery pack 20. In detail, as the temperature rise control, the control device 70 turns on and off each of the switches QUH to QWL so that an AC current flows between the first storage battery 21 and the second storage battery 22 through the switching device unit 31, the winding 41, and the connection path 60 while the connection switch 61 is on. Note that the equivalent circuit of the power conversion device 11 used in the temperature rise control is the same as that shown in FIG. 11 above.

[0148] FIG. 21 shows a functional block diagram of the temperature rise control. The control device 70 includes a command current generating unit 110. The command current generating unit 110 sets the neutral point command current IM*. In this embodiment, the neutral point command current IM* is set as a sine wave as shown in FIG. 22. More specifically, the neutral point command current IM* is set so that the positive neutral point command current IM* and the negative neutral point command current IM* are point-symmetric with respect to the timing (hereinafter, zero cross timing) at which the value of the neutral point command current IM* becomes 0 from a value other than 0 in one period Tc of the neutral point command current IM*. As a result, in FIG. 22, the period from the first zero cross timing C1 to the second zero cross timing C2 of the neutral point command current IM* is equal to the period from the second zero cross timing C2 to the third zero cross timing C3. Here, the magnitude of the positive side amplitude Ia of the neutral point command current IM* is equal to the magnitude of the negative side amplitude Ib.

[0149] In addition, in one period Tc of the neutral point command current IM*, the area S1 of the first region and the area S2 of the second region are equal. The area S1 of the first region is an area surrounded by the time axis from the first zero cross timing C1 to the second zero cross timing C2 of the neutral point command current IM* and the positive neutral point command current IM* in one period Tc of the neutral point command current IM*. The area S2 of the second region is an area surrounded by the time axis from the second zero cross timing C2 to the third zero cross timing C3 of the neutral point command current IM* and the negative neutral point command current IM* in one period Tc.

[0150] By setting the area S1 of the first region and the area S2 of the second region to be equal to each other, it is possible to balance the charge and discharge currents of the first storage battery 21 and the second storage battery 22 in one period Tc. Therefore, it is possible to suppress an increase in the difference between the terminal voltage VBH of the first storage battery 21 and the terminal voltage VBL of the second storage battery 22 due to the temperature rise control.

[0151] In this embodiment, the positive and negative polarities of the neutral point command current IM* are similar to those of the neutral point current IMr in the second embodiment.

[0152] Returning to the explanation of Fig. 21, the control device 70 includes a droop control unit 111. The droop control unit 111 limits the input neutral point command current IM* and outputs it as a final command current IMa*. The absolute value of the neutral point command current IM* is limited to a limit value or less. The method of setting the limit value will be described later.

[0153] The control device 70 includes a current deviation calculation unit 112 , a feedback controller 113 , a PWM generation unit 114 , and an inverter 115 .

[0154] The current deviation calculation unit 112 calculates the neutral point current deviation ΔIM by subtracting the neutral point current IMr detected by the current sensor 62 from the final command current IMa*. The feedback controller 113 calculates a duty signal D as an operation amount for feeding back the neutral point current deviation ΔIM calculated by the current deviation calculation unit 112 to zero. The duty signal D includes the duty ratios of the upper and lower arm switches QUH to QWL of each phase. Here, the duty ratios of the upper and lower arm switches QUH to QWL of each phase are values ​​that determine the ratio (Ton / Tsw) of the on time Ton in one switching period Tsw. The feedback control used by the feedback controller 113 is, for example, proportional-integral control.

[0155] The PWM generating unit 114 generates gate signals for the upper arm switches QUH to QWH based on the duty signal D calculated by the feedback controller 113. The inverter 115 generates gate signals for the lower arm switches QUL to QWL by inverting the logic of the gate signals for the upper arm switches QUH to QWH. Here, the gate signals are signals that instruct the on or off of each of the switches QUH to QWL.

[0156] With the above-mentioned configuration, the switches QUH to QWL are turned on and off so that an AC current flows between the first storage battery 21 and the second storage battery 22, and the temperature of the battery pack 20 is raised. However, the terminal voltage Vce of the battery cells constituting the battery pack 20 fluctuates as a result of the temperature rise control. If the fluctuation in the terminal voltage Vce of the battery cell is large, the battery cell may temporarily enter an over-discharged or over-charged state. As a result, there is a concern that the battery cell may deteriorate.

[0157] Therefore, in this embodiment, the control device 70 is configured to perform droop control when it is determined that an overcharged or overdischarged state occurs in a battery cell, in order to protect the battery cell while ensuring the temperature rise capability in the temperature rise control. In this embodiment, the droop control is a control that changes a limit value that limits the neutral point command current IM* based on the terminal voltage Vce of a battery cell that has experienced an overcharged or overdischarged state among the battery cells that constitute the battery pack 20. A method for setting the limit value will be described below.

[0158] The control device 70 judges whether an overcharged state or an overdischarged state occurs in the battery cells based on the terminal voltages Vce of the battery cells constituting the assembled battery 20. Specifically, when the droop control unit 111 of the control device 70 judges that the terminal voltages Vce of the battery cells are within a specified voltage range, the control device 70 judges that the battery cells constituting the assembled battery 20 are not in an overcharged state or an overdischarged state. The specified voltage range is determined by a specified voltage lower limit Vmin and a specified voltage upper limit Vmax. When the terminal voltage Vce of the battery cell falls below the specified voltage lower limit Vmin, the control device 70 judges that the battery cell is in an overdischarged state. On the other hand, when the terminal voltage Vce of the battery cell exceeds the specified voltage upper limit Vmax, the control device 70 judges that the battery cell is in an overcharged state. The control device 70 treats the battery cell determined to be in an overdischarged state as an overdischarge protection target, and treats the battery cell determined to be in an overcharged state as an overcharge protection target. The terminal voltage Vce of the battery cell corresponds to a "voltage parameter".

[0159] The limit value is set in the droop control unit 111. The droop control unit 111 calculates a droop coefficient CL, which is a value between 0 and 1, based on the terminal voltage Vce of the battery cell, and multiplies predetermined discharge and charge limit values ​​IMd, IMc by the droop coefficient CL to set final discharge and charge limit values ​​IMd, IMc.

[0160] In detail, when the droop control unit 111 determines that neither an over-discharge state nor an over-charge state has occurred in the battery cell, it sets the droop coefficient CL to 1. In this case, the predetermined discharge and charge limit values ​​IMd, IMc become the final discharge and charge limit values ​​IMd, IMc as they are.

[0161] When the droop control unit 111 determines that the battery cell is in an over-discharged state, it calculates a droop coefficient CL that is smaller than 1 based on the terminal voltage Vce of the battery cell that is the target of over-discharge protection. In this case, the droop control unit 111 changes the discharge limit value IMd of the command discharge current, which is the discharge current of the battery cell that is the target of over-discharge protection, out of the neutral point command current IM*, and sets the discharge limit value IMd multiplied by the droop coefficient CL, "CL×IMd", as the final discharge limit value.

[0162] When the droop control unit 111 determines that the battery cell is in an overcharged state, it calculates a droop coefficient CL smaller than 1 based on the terminal voltage Vce of the battery cell that is the overcharge protection target. In this case, the droop control unit 111 changes the charge limit value IMc of the command charge current, which is the charge current of the battery cell that is the overcharge protection target, out of the neutral point command current IM*, and sets "CL×IMc", which is the charge limit value IMc multiplied by the droop coefficient CL, as the final charge limit value.

[0163] The control device 70 limits the absolute value of the neutral point command current IM* to the final discharge and charge limit values ​​IMd, IMc or less. In detail, when the absolute value of the command discharge current is equal to or less than "CL×IMd", the droop control unit 111 calculates the command discharge current as the final command current IMa* as is. When the absolute value of the command discharge current exceeds "CL×IMd", the droop control unit 111 limits the absolute value of the command discharge current to "CL×IMd" and calculates it as the final command current IMa*. On the other hand, when the absolute value of the command charging current is equal to or less than "CL×IMc", the droop control unit 111 calculates the command charging current as the final command current IMa* as is. When the absolute value of the command charging current exceeds "CL×IMc", the droop control unit 111 limits the absolute value of the command charging current to "CL×IMc" and calculates it as the final command current IMa*.

[0164] Here, for example, when a battery cell determined to be in an over-discharged state is included in the first storage battery 21, a current with a positive sign among the neutral point command currents IM* corresponds to the command discharge current. On the other hand, for example, when a battery cell determined to be in an over-discharged state is included in the second storage battery 22, a current with a negative sign among the neutral point command currents IM* corresponds to the command discharge current. Also, for example, when a battery cell determined to be in an over-charged state is included in the first storage battery 21, a current with a negative sign among the neutral point command currents IM* corresponds to the command charge current. On the other hand, for example, when a battery cell determined to be in an over-charged state is included in the second storage battery 22, a current with a positive sign among the neutral point command currents IM* corresponds to the command charge current.

[0165] A method for calculating the drooping coefficient CL is shown in Fig. 23. When the terminal voltage Vce of the battery cell is within a specified voltage range, the drooping control unit 111 sets the drooping coefficient CL to 1. As a result, the neutral point command current IM* is limited by the predetermined discharge and charge limit values ​​IMd and IMc.

[0166] When the terminal voltage Vce of the battery cell falls below the specified voltage lower limit value Vmin, the droop control unit 111 linearly reduces the droop coefficient CL as the terminal voltage Vce of the battery cell becomes lower. Here, the droop coefficient CL can be reduced until it becomes 0. The droop control unit 111 multiplies the discharge limit value IMd by the droop coefficient CL. As a result, the absolute value of the command discharge current is limited to be equal to or less than the reduced discharge limit value "CL x IMd". In this case, the reduced discharge limit value "CL x IMd" becomes smaller than the peak value of the command discharge current.

[0167] When the terminal voltage Vce of a battery cell exceeds the specified voltage upper limit value Vmax, the droop control unit 111 linearly reduces the droop coefficient CL as the terminal voltage Vce of the battery cell increases. Here, the droop coefficient CL can be reduced until it becomes 0. The droop control unit 111 multiplies the charging limit value IMc by the droop coefficient CL. This limits the absolute value of the command charging current to be equal to or less than the reduced charging limit value "CL x IMc". In this case, the reduced charging limit value "CL x IMc" becomes smaller than the peak value of the command charging current.

[0168] 24 shows a procedure for the temperature rise control performed by the control device 70. The temperature rise control is repeatedly performed at a predetermined control period.

[0169] In step S40, it is determined whether or not there is a request to increase the temperature of the first storage battery 21 and the second storage battery 22. In this embodiment, when it is determined that the temperature T of the battery pack 20 is equal to or lower than the target temperature T*, it is determined that there is a request to increase the temperature. Here, the temperature T of the battery pack 20 may be acquired from the monitoring unit 50. Note that the temperature T of the battery pack 20 may be the temperature of the first storage battery 21, the temperature of the second storage battery 22, or the average temperature of the first storage battery 21 and the second storage battery 22.

[0170] If it is determined in step S40 that there is no temperature increase request, the process proceeds to step S41, where it is determined whether there is a request to drive the rotating electric machine 40. This drive request includes a request to drive the rotating electric machine 40 to run the vehicle.

[0171] If it is determined in step S41 that there is no request to drive the rotating electric machine 40, the process proceeds to step S42, where the standby mode is set. In the standby mode, the switches QUH to QWL of the switching device unit 31 are turned off. Then, in step S43, the connection switch 61 is turned off. This electrically disconnects the intermediate terminal B from the neutral point O.

[0172] If it is determined in step S41 that there is a request to drive the rotating electric machine 40, the process proceeds to step S44, where the rotating electric machine drive mode is set. Then, in step S45, the connection switch 61 is turned off. This electrically disconnects the intermediate terminal B and the neutral point O via the connection path 60. After that, in step S46, rotating electric machine drive PWM control is performed. In the rotating electric machine drive PWM control, switching control is performed on the switches QUH to QWL of the switching device unit 31 in order to drive the rotating electric machine 40. This causes the drive wheels of the vehicle to rotate, allowing the vehicle to run.

[0173] If it is determined in step S40 that there is a temperature increase request, the process proceeds to step S47, where it is determined whether or not an overcharged state or an overdischarged state occurs in each of the battery cells constituting the battery pack 20. In more detail, if the terminal voltage Vce of the battery cell falls below the specified voltage lower limit Vmin, it is determined that the battery cell is in an overdischarged state. On the other hand, if the terminal voltage Vce of the battery cell exceeds the specified voltage upper limit Vmax, it is determined that the battery cell is in an overcharged state.

[0174] If it is determined in step S47 that neither the overcharged state nor the overdischarged state occurs in the battery cell, the process proceeds to step S48. In step S48, the temperature rise control mode is set. Then, in step S49, the connection switch 61 is turned on. This electrically connects the intermediate terminal B and the neutral point O via the connection path 60.

[0175] In step S50, a temperature-rise PWM control is performed to raise the temperatures of the first storage battery 21 and the second storage battery 22. In the temperature-rise PWM control, the switches QUH to QWL are turned on and off to control the neutral point current IMr to the final command current IMa*. This causes an AC current to flow between the first storage battery 21 and the second storage battery 22 via the switching device unit 31, the winding 41, and the connection path 60, thereby raising the temperatures of the first storage battery 21 and the second storage battery 22. Note that in the temperature-rise PWM control, the droop coefficient CL calculated by the droop control unit 111 is 1. That is, the neutral point command current IM* is limited by a predetermined limit value, and the final command current IMa* is calculated.

[0176] On the other hand, if it is determined in step S47 that an overcharged state or an overdischarged state has occurred in the battery cell, the process proceeds to step S51. In step S51, the drooping temperature rise control mode is set.

[0177] In step S52, a drooping coefficient CL smaller than 1 is calculated based on the terminal voltage Vce of the battery cell in which an overcharged or overdischarged state has occurred. In detail, when the terminal voltage Vce of the battery cell falls below the specified voltage lower limit Vmin, the drooping coefficient CL is reduced as the terminal voltage Vce of the battery cell decreases, and when the terminal voltage Vce of the battery cell exceeds the specified voltage upper limit Vmax, the drooping coefficient CL is reduced as the terminal voltage Vce of the battery cell increases.

[0178] In step S53, the amplitude of the neutral point command current IM* set in the command current generating unit 110 is increased. Here, increasing the amplitude of the neutral point command current IM* corresponds to increasing the positive side amplitude Ia and the negative side amplitude Ib in FIG.

[0179] In step S54, 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.

[0180] In step S55, drooping temperature rise PWM control is performed to protect the battery cells while ensuring the temperature rise capability in the temperature rise control. In the drooping temperature rise PWM control, if it is determined that the battery cell is in an over-discharged state, the discharge limit value IMd is multiplied by the drooping coefficient CL calculated in step S52. This reduces the discharge limit value IMd. On the other hand, if it is determined that the battery cell is in an over-charged state, the charge limit value IMc is multiplied by the drooping coefficient CL calculated in step S52. This reduces the charge limit value IMc. The final command current IMa* is calculated so that the neutral point command current IM* is equal to or less than the discharge limit value CL×IMd and the charge limit value CL×IMc.

[0181] In order to control the neutral point current IMr to the final command current IMa*, the switches QUH to QWL are turned on and off. As a result, an AC current flows between the first storage battery 21 and the second storage battery 22 via the switching device unit 31, the winding 41, and the connection path 60, and the temperatures of the first storage battery 21 and the second storage battery 22 are raised.

[0182] Fig. 25 shows an example of temperature rise control when a battery cell constituting the first storage battery 21 is determined to be in an over-discharged state. In Fig. 25, (a) shows the transition of the neutral point current IMr, and (b) shows the transition of the terminal voltage Vce of the battery cell determined to be in an over-discharged state. Note that the solid line shows the transition of the neutral point current IMr and the battery cell terminal voltage Vce when droop control is implemented, and the dashed line shows the transition of the neutral point current IMr and the battery cell terminal voltage Vce when droop control is not implemented. For convenience, the process of step S53 is omitted in Fig. 25.

[0183] When the battery cell terminal voltage Vce is within the specified voltage range, the droop coefficient CL is set to 1. When the battery cell terminal voltage Vce falls below the specified voltage lower limit Vmin, a droop coefficient CL smaller than 1 is calculated. As a result, the negative absolute value of the neutral point command current IM* is limited to "CL×IMd" or less, and the negative peak value of the neutral point current IMr becomes "CL×IMd". Note that FIG. 25 shows an example in which the neutral point current IMr is limited to a constant value "CL×IMd" for convenience during the period in which the battery cell terminal voltage Vce falls below the specified voltage lower limit Vmin. However, in reality, during the period in which the battery cell terminal voltage Vce falls below the specified voltage lower limit Vmin, "CL×IMd" may be changed each time based on the battery cell terminal voltage Vce.

[0184] By implementing the droop control, the negative peak value of the neutral point current IMr is limited to or less than "CL x IMd", so that the fluctuation of the terminal voltage Vce of the battery cell is suppressed more than when the droop control is not implemented. This makes it possible to prevent the battery cell from entering an over-discharge state.

[0185] Figure 26 shows the transition of the neutral point current IMr when the amplitude of the neutral point command current IM* is increased by the processing of step S53 in Figure 24 during the period when the terminal voltage Vce of the battery cell is below the specified voltage lower limit value Vmin. In Figure 26, (a) is a comparative example of the transition of the neutral point current IMr when the amplitude of the neutral point command current IM* is not increased, and (b) is the transition of the neutral point current IMr when the neutral point command current IM* is increased. Note that the solid line shows the transition of the neutral point current IMr, and the dashed line shows the transition of the neutral point command current IM*.

[0186] When the neutral point command current IM* is not increased, the waveforms of the neutral point current IMr and the neutral point command current IM* become the waveforms shown in Fig. 26(a). In this case, the waveform of the neutral point command current IM* has a positive amplitude of Ia1 and a negative amplitude of Ib1.

[0187] When the neutral point command current IM* is increased, the waveforms of the neutral point current IMr and the neutral point command current IM* become the waveforms shown in Fig. 26(b). In this case, the positive side amplitude Ia2 of the neutral point command current IM* is larger than the positive side amplitude Ia1 of the neutral point command current IM* in Fig. 26(a), and the negative side amplitude Ib2 is larger than the negative side amplitude Ib1 of the neutral point command current IM* in Fig. 26(a).

[0188] The peak value of the negative neutral point current IMr does not fall below "CL×IMd" due to the implementation of the droop control. However, since the amplitudes Ia2 and Ib2 of the neutral point command current IM* in FIG. 26(b) are increased more than the amplitudes Ia1 and Ib1 of the neutral point command current IM* in FIG. 26(a), the time change amount of the neutral point current IMr in FIG. 26(b) is larger than the time change amount of the neutral point current IMr in FIG. 26(a). Therefore, the area of ​​the region surrounded by the negative neutral point current IMr and the time axis in FIG. 26(a) is "F1", whereas the area of ​​the region surrounded by the negative neutral point current IMr and the time axis in FIG. 26(b) is "F1+F2". The larger the area of ​​the region surrounded by the neutral point current IMr and the time axis, the greater the ability to heat the battery pack 20.

[0189] In addition, by increasing the positive amplitude of the neutral point command current IM*, the area of ​​the region surrounded by the positive side neutral point current IMr and the time axis in Figure 26(b) is also made larger than the area of ​​the region surrounded by the positive side neutral point current IMr and the time axis in Figure 26(a).

[0190] In the droop control, the process of increasing the amplitude of the neutral point command current IM* is performed, so that the temperature rise capability can be improved more than when the amplitude of the neutral point command current IM* is not increased.

[0191] The features of the present embodiment described above are as follows.

[0192] The composition of Section A is as follows: a rotating electric machine having star-connected windings; An inverter having a series connection of upper arm switches and lower arm switches, a connection path that electrically connects a negative electrode side of the first power storage unit and a positive electrode side of the second power storage unit, in a first power storage unit and a second power storage unit that are connected in series, to a neutral point of the winding; a connection switch that is provided in the connection path and that, when turned on, electrically connects a negative electrode side of the first power storage unit and a positive electrode side of the second power storage unit to the neutral point and, when turned off, electrically disconnects the negative electrode side of the first power storage unit and the positive electrode side of the second power storage unit from the neutral point; a determination unit that determines whether or not to turn on the connection switch; a control unit that turns on the connection switch and performs switching control of the upper arm switch and the lower arm switch when the determination unit determines that the connection switch should be turned on; a voltage acquisition unit that acquires a voltage parameter that is a voltage of the first power storage unit and a terminal voltage of the second power storage unit or a correlation value of the terminal voltages; the determination unit determines whether or not there is a control request to flow a current between the first power storage unit and the second power storage unit, and determines to turn on the connection switch when it is determined that there is the control request; The control unit is when it is determined by the determination unit to turn on the connection switch and when it is determined that the voltage parameters of the first power storage unit and the second power storage unit acquired by the voltage acquisition unit are within a specified voltage range, performing the switching control such that a current flows between the first power storage unit and the second power storage unit via the inverter, the winding, and the connection path in a state in which the connection switch is turned on; when it is determined that the connection switch should be turned on and when it is determined that the minimum value of the voltage parameters of each of the first power storage unit and the second power storage unit is below a lower limit value of the specified voltage range, performing the switching control so that a discharge current discharged by one of the first power storage unit and the second power storage unit, which is an over-discharge protection target having the minimum voltage parameter, is made smaller than a discharge current when the voltages of the first power storage unit and the second power storage unit are within the specified voltage range; When it is determined that the connection switch should be turned on and when it is determined that the maximum value of the voltage parameters of the first and second storage units exceeds the upper limit value of the specified voltage range, the switching control is performed so that the charging current charged to the overcharge protection target, of the first and second storage units, whose voltage parameter has the maximum value, is smaller than when the voltages of the first and second storage units are within the specified voltage range.

[0193] In the configuration of B, in the configuration of A, the determination unit determines whether or not there is a request to increase temperatures of the first power storage unit and the second power storage unit as the control request, and determines to turn on the connection switch when it is determined that there is a request to increase temperatures; The control unit is as the switching control when it is determined that the voltage parameters of the first power storage unit and the second power storage unit are within the specified voltage range, an AC current is caused to flow between the first power storage unit and the second power storage unit; as the switching control when it is determined that the minimum value falls below the lower limit value, a peak value of the discharge current of the over-discharge protection target is made smaller than a peak value when the voltage parameters of the first power storage unit and the second power storage unit are within the specified voltage range; As the switching control when it is determined that the maximum value exceeds the upper limit value, the peak value of the charging current of the overcharge protection target is made smaller than when the voltage parameters of the first storage unit and the second storage unit are within the specified voltage range.

[0194] According to the Bth configuration, switching control is performed so that an AC current flows between the first and second power storage units. When it is determined that the minimum value of each of the voltage parameters of the first and second power storage units is below the lower limit of the specified voltage range, the peak value of the discharge current of the over-discharge protection target is reduced. When it is determined that the maximum value of each of the voltage parameters of the first and second power storage units is above the upper limit of the specified voltage range, the peak value of the charge current of the over-charge protection target is reduced. This makes it possible to suppress fluctuations in the voltage of the over-discharge protection target and the over-charge protection target. As a result, it is possible to suppress deterioration of the first and second power storage units.

[0195] In the configuration C, in the configuration B, A current acquisition unit that acquires a current flowing through a neutral point of the winding, The control unit is performing the switching control to control the current acquired by the current acquisition unit to an AC command current when it is determined that the connection switch is to be turned on and when it is determined that the voltage parameters of the first power storage unit and the second power storage unit are each within the specified voltage range; when it is determined that the connection switch is to be turned on and that the minimum value is lower than the lower limit value, limiting a command discharge current, which is a command current for discharging the target for over-discharge protection, to a discharge limit value smaller than an amplitude of the command discharge current; When it is determined that the connection switch is to be turned on and that the maximum value exceeds the upper limit value, the command charging current, which is the command current among the command currents that charges the object of overcharge protection, is limited to a charging limit value that is smaller than the amplitude of the command charging current.

[0196] According to the Cth configuration, switching control is performed to control the current acquired by the current acquisition unit to the command current. In the above-mentioned configuration, when it is determined that the minimum value of each of the voltage parameters of the first and second storage units is below the lower limit of the specified voltage range, the command discharge current is limited to a discharge limit value whose value is smaller than the amplitude of the command discharge current. Also, when it is determined that the maximum value of each of the voltage parameters of the first and second storage units is above the upper limit of the specified voltage range, the command charge current is limited to a charge limit value whose value is smaller than the amplitude of the command charge current. This makes it possible to accurately reduce the peak value of the discharge current of the object of overdischarge protection and the peak value of the charge current of the object of overcharge protection.

[0197] In the configuration of D, in the configuration of C, The control unit is when it is determined that the connection switch is to be turned on and that the maximum value exceeds the upper limit value, the charging limit value is reduced as the voltage parameter of the overcharge protection target is higher; When it is determined that the connection switch should be turned on and that the minimum value falls below the lower limit value, the discharge limit value is made smaller as the voltage parameter of the object to be protected from over-discharge is lower.

[0198] According to the configuration D, the charge limit value and the discharge limit value are set based on the voltage parameters of the respective power storage units, whereby it is possible to appropriately reduce the peak value of the discharge current of the object to be protected from overdischarge and the peak value of the charge current of the object to be protected from overcharge while ensuring the energy exchanged between the first power storage unit and the second power storage unit.

[0199] In the Eth embodiment, in the Dth embodiment, The control unit is When it is determined that the connection switch is to be turned on and the maximum value is greater than the upper limit value, the amplitude of the command charging current is increased; When it is determined that the connection switch should be turned on and that the minimum value falls below the lower limit value, the amplitude of the command discharge current is increased.

[0200] There is a concern that the current flowing between the first and second power storage units may be reduced by limiting the command current by the discharge limit value and the charge limit value. In this regard, according to the configuration of E, when it is determined that the minimum value of each of the voltage parameters of the first and second power storage units is below the lower limit value of the specified voltage range, the amplitude of the command discharge current is increased. Also, when it is determined that the maximum value of each of the voltage parameters of the first and second power storage units is above the upper limit value of the specified voltage range, the amplitude of the command charge current is increased. In this way, by increasing the current flowing between the first and second power storage units, it is possible to ensure the temperature rise capability while suppressing the occurrence of deterioration of each power storage unit.

[0201] In the configuration of F, in the configuration of A, A current acquisition unit that acquires a current flowing through a neutral point of the winding, the determination unit determines whether or not there is a request for energy transfer from one of the first power storage unit and the second power storage unit to the other, as the control request, and when it is determined that there is a request for energy transfer, determines to turn on the connection switch; The control unit is when it is determined that the connection switch is to be turned on and when it is determined that the voltage parameters of each of the first power storage unit and the second power storage unit are within the specified voltage range, performing the switching control to control the current acquired by the current acquisition unit to a DC command current; If it is determined that the minimum value of the voltage parameters of the first and second power storage units falls below the lower limit of a specified voltage range, or the maximum value of the voltage parameters of the first and second power storage units exceeds the upper limit of a specified voltage range, the magnitude of the command current is limited to a DC limit value smaller than the magnitude of the command current.

[0202] According to the configuration F, when the control unit determines that the connection switch is to be turned on and that the voltage parameters of the first and second storage units are within the specified voltage range, the control unit performs switching control to control the current acquired by the current acquisition unit to a DC command current. When the control unit determines that the minimum value of the voltage parameters of the first and second storage units is below the lower limit of the specified voltage range, or when the control unit determines that the maximum value of the voltage parameters of the first and second storage units is above the upper limit of the specified voltage range, the control unit limits the magnitude of the command current to a DC limit value smaller than the magnitude of the command current. This reduces the magnitude of the current when energy is supplied from one of the first and second storage units to the other. This makes it possible to reduce the rate at which the voltages of the first and second storage units decrease or increase. As a result, it is possible to prevent the first and second storage units from becoming over-discharged or over-charged.

[0203] The effects achieved by embodying the above-described features will now be described.

[0204] In this embodiment, when it is determined that there is a request to increase the temperature of the battery pack 20, with the connection switch 61 turned on, each switch QUH to QWL is turned on and off so that an AC current flows between the first storage battery 21 and the second storage battery 22 via the switching device unit 31, the winding 41, and the connection path 60.

[0205] In the above-mentioned configuration, when it is determined that the terminal voltage Vce of the battery cells constituting the assembled battery 20 falls below the specified voltage lower limit Vmin, the amplitude of the neutral point command current IM*, which is the discharge current of the battery cells that are the object of over-discharge protection, is reduced. Also, when it is determined that the terminal voltage Vce of the battery cells constituting the assembled battery 20 exceeds the specified voltage upper limit Vmax, the amplitude of the neutral point command current IM*, which is the charge current of the battery cells that are the object of over-charge protection, is reduced. This makes it possible to prevent the terminal voltage Vce of the battery cells from falling outside the specified voltage range. As a result, it is possible to prevent the first storage battery 21 and the second storage battery 22 from being deteriorated.

[0206] The drooping coefficient CL is set based on the terminal voltages Vce of the battery cells that are the object of over-discharge protection and the battery cells that are the object of over-charge protection, and the reduction amounts of the commanded discharge current and the commanded charge current are set. This makes it possible to appropriately reduce the peak value of the discharge current and the peak value of the charge current while securing the energy for raising the temperature exchanged between the first storage battery 21 and the second storage battery 22.

[0207] There is a concern that the temperature rise capability may be reduced by limiting the neutral point command current IM* by the discharge limit value IMd and the charge limit value IMc. In this regard, in the present embodiment, when it is determined that the terminal voltage Vce of the battery cells constituting the assembled battery 20 is below the specified voltage lower limit value Vmin, and when it is determined that the terminal voltage Vce of the battery cells constituting the assembled battery 20 is above the specified voltage upper limit value Vmax, the amplitudes Ia, Ib of the neutral point command current IM* are increased. This makes it possible to increase the current flowing between the first storage battery 21 and the second storage battery 22 while suppressing the occurrence of deterioration in each storage unit. As a result, it is possible to ensure the temperature rise capability while suppressing the occurrence of deterioration in each storage unit.

[0208] <Modification of the third embodiment> The method of setting the neutral point command current IM* is not limited to that shown in Fig. 22. For example, the positive neutral point command current IM* and the negative neutral point command current IM* may each be set to a trapezoidal wave or a square wave while satisfying a point-symmetric relationship between the positive neutral point command current IM* and the negative neutral point command current IM* with respect to the zero-cross timing of the neutral point command current IM* in one cycle Tc.

[0209] Furthermore, the method of setting the neutral point command current IM* is not limited to the one that satisfies the point symmetry relationship. For example, the neutral point command current IM* may be set so that the period from the first zero cross timing C1 to the second zero cross timing C2 of the neutral point command current IM* is different from the period from the second zero cross timing C2 to the third zero cross timing C3 of the neutral point command current IM* in one cycle Tc, and the area S1 of the first region is equal to the area S2 of the second region. Even in this case, 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 matched.

[0210] The control device 70 may determine whether or not an overcharged or overdischarged state occurs in the battery cells based on the SOC of the battery cells constituting the battery pack 20 instead of the terminal voltage Vce of the battery cells constituting the battery pack 20. Specifically, when the control device 70 determines that the SOC of each battery cell is within a specified SOC range, it determines that the battery cells constituting the battery pack 20 are not in an overcharged or overdischarged state. The specified SOC range is determined by a specified SOC lower limit value and a specified SOC upper limit value. When the SOC of a battery cell falls below the specified SOC lower limit value, the control device 70 determines that the battery cell is in an overdischarged state. On the other hand, when the SOC of a battery cell exceeds the specified SOC upper limit value, the control device 70 determines that the battery cell is in an overcharged state. The SOC of the battery cell corresponds to the "voltage parameter."

[0211] In step S47, if the SOC of the battery cells constituting the assembled battery 20 falls below a specified SOC lower limit, the battery cells are determined to be in an over-discharged state. On the other hand, if the SOC of the battery cells constituting the assembled battery 20 exceeds a specified SOC upper limit, the battery cells are determined to be in an over-charged state. In these cases, the process proceeds to step S51. The SOC of the battery cells may be obtained from the monitoring unit 50.

[0212] The neutral point command current IM* may be a direct current. In this case, the control device 70 performs control to supply energy from one of the first storage battery 21 and the second storage battery 22 to the other, instead of performing temperature increase control of the first storage battery 21 and the second storage battery 22. This control is similar to the control shown in FIG. 24.

[0213] Specifically, in step S40, instead of determining whether or not there is a request to increase the temperatures of the first storage battery 21 and the second storage battery 22, it is determined whether or not there is a request to transfer energy between the first storage battery 21 and the second storage battery 22. The method of determining whether or not there is a request to transfer energy is the same as in the second embodiment.

[0214] If it is determined that there is a request for energy transfer, the process proceeds to step S47. In step S47, it is determined whether or not an overcharged state or an overdischarged state occurs in each of the battery cells constituting the battery pack 20.

[0215] If it is determined in step S47 that neither the overcharged state nor the overdischarged state occurs in the battery cell, the process proceeds to step S48. In step S48, the energy transfer control mode is set instead of the temperature increase control mode. In step S49, the connection switch 61 is turned on.

[0216] In step S50, the control device 70 performs PWM control to transfer energy between the first storage battery 21 and the second storage battery 22. In detail, in a state where the connection switch 61 is turned on, the control device 70 turns on and off each of the switches QUH to QWL so that a current flows between the first storage battery 21 and the second storage battery 22 via the switching device unit 31, the winding 41, and the connection path 60. In detail, when a positive neutral point command current IM* is set in the command current generating unit 110, energy is supplied from the first storage battery 21 to the second storage battery 22, and when a negative neutral point command current IM* is set, energy is supplied from the second storage battery 22 to the first storage battery 21. The equivalent circuit and the functional block diagram are the same as those in the temperature rise control.

[0217] If it is determined in step S47 that an overcharged state or an overdischarged state has occurred in the battery cell, the process proceeds to step S51. In step S51, the drooping energy transfer control mode is set instead of the drooping temperature rise control mode.

[0218] In step S52, the drooping coefficient CL is calculated based on the terminal voltage Vce of the battery cell in which an overcharged or overdischarged state has occurred. In detail, similar to the case where the neutral point command current IM* is an AC current, when the drooping control unit 111 determines that the terminal voltage Vce of the battery cell constituting the battery pack 20 is within the specified voltage range, the drooping control unit 111 sets the drooping coefficient CL to 1. On the other hand, when the drooping control unit 111 determines that the terminal voltage Vce of the battery cell is below the specified voltage lower limit value Vmin or above the specified voltage upper limit value Vmax, the drooping control unit 111 reduces the drooping coefficient CL to a value smaller than 1.

[0219] The droop control unit 111 multiplies the DC limit value IMdc that limits the neutral point command current IM* by the droop coefficient CL to obtain the final DC limit value. The droop control unit 111 limits the absolute value of the neutral point command current IM* to "CL x IMdc" or less. In detail, when the absolute value of the neutral point command current IM* is "CL x IMdc" or less, the droop control unit 111 calculates the neutral point command current IM* as the final command current IMa* as it is. When the absolute value of the neutral point command current IM* exceeds "CL x IMdc", the droop control unit 111 limits the absolute value of the neutral point command current IM* to "CL x IMdc" and calculates it as the final command current IMa*.

[0220] In step S54, the connection switch 61 is turned on. In step S55, the control device 70 performs PWM control to transfer energy between the first storage battery 21 and the second storage battery 22. The process of step S53 is not performed.

[0221] The calculation method of the drooping coefficient CL is not limited to that shown in Fig. 23. In the region where the terminal voltage Vce of the battery cell falls below the specified voltage lower limit Vmin, the drooping control unit 111 is not limited to a method in which the drooping coefficient CL is linearly reduced as the terminal voltage Vce of the battery cell becomes lower, but may be a method in which the drooping coefficient CL is reduced as the terminal voltage Vce of the battery cell becomes lower. Also, in the region where the terminal voltage Vce of the battery cell exceeds the specified voltage upper limit Vmax, the drooping coefficient CL is not limited to a method in which the drooping coefficient CL is linearly reduced as the terminal voltage Vce of the battery cell becomes higher, but may be a method in which the drooping coefficient CL is reduced as the terminal voltage Vce of the battery cell becomes higher.

[0222] The droop control unit 111 may calculate the droop coefficient CL based on the SOC of the battery cell, instead of calculating the droop coefficient CL based on the terminal voltage Vce of the battery cell. In this case, when the SOC of the battery cell is within a specified SOC range, the droop control unit 111 may set the droop coefficient CL to 1. When the SOC of the battery cell falls below a specified SOC lower limit, the droop control unit 111 may reduce the droop coefficient CL as the SOC of the battery cell decreases. When the SOC of the battery cell exceeds a specified SOC upper limit, the droop control unit 111 may reduce the droop coefficient CL as the SOC of the battery cell increases.

[0223] Instead of multiplying the limit value by the droop coefficient CL, the neutral point command current IM* may be multiplied by the droop coefficient CL. As a result, when the terminal voltage Vce of the battery cell falls below the specified voltage lower limit value Vmin or exceeds the specified voltage upper limit value Vmax, the neutral point command current IM* is reduced, so that the peak value of the neutral point command current IM* can be reduced.

[0224] The process of step S53 does not have to be performed.

[0225] Instead of the configuration in Fig. 21, switching control may be performed using the configuration shown in Fig. 27. The control device 70 includes a hysteresis controller 116 instead of the feedback controller 113 and the PWM generating unit 114. The hysteresis controller 116 generates gate signals for each of the upper arm switches QUH to QWH based on the neutral point current deviation ΔIM. In detail, the hysteresis controller 116 generates gate signals for each of the upper arm switches QUH to QWH based on the neutral point current deviation ΔIM so that the neutral point command current IM* falls within a range of ±ΔI determined based on the neutral point command current IM*.

[0226] <Other embodiments> Each of the above embodiments may be modified as follows.

[0227] The rotating electric machine 40 and the switching device unit 31 may be of a phase other than three, such as five phase or seven phase. Fig. 28 shows a power conversion system 10 in which the rotating electric machine 40 and the switching device unit 31 have five phases. In Fig. 28, the same components as those shown in Fig. 1 are denoted by the same reference numerals for convenience.

[0228] 28, X-phase upper and lower arm switches QXH, QXL and diodes DXH, DXL are added to the switching device section 31, and Y-phase upper and lower arm switches QYH, QYL and diodes DYH, DYL are added to the rotating electric machine 40. An X-phase winding 41X and a Y-phase winding 41Y are added to the power conversion device 11. An X-phase conductive member 32X and a Y-phase conductive member 32Y are added to the power conversion device 11.

[0229] In the first embodiment, in the configuration shown in Fig. 28, when the connection switch 61 is in an OFF state, a divided voltage value of the terminal voltage of the battery pack 20 is applied to the in-phase winding 41a, which is a winding of any one of the U- to Y-phase windings 41U-41Y, in the switch drive control. In this embodiment, the maximum winding voltage Vm is 4 / 5 x Vdc. Therefore, the maximum winding voltage Vm is greater in the five-phase case than in the three-phase case. Even in this case, the maximum winding voltage Vm can be reduced to 1 / 2 x Vdc ​​by performing the switch drive control with the connection switch 61 in an ON state.

[0230] In the second embodiment, even when the number of phases of the winding 41 through which a current flows is more than three, the maximum efficient power Pmax increases according to the number of phases of the winding 41 through which a current flows. In other words, the maximum efficient power Pmax4 when the number of phases of the winding 41 through which a current flows is four is greater than the maximum efficient power Pmax3 when the number of phases of the winding 41 through which a current flows is three. Moreover, the maximum efficient power Pmax5 when the number of phases of the winding 41 through which a current flows is five is greater than the maximum efficient power Pmax4 when the number of phases of the winding 41 through which a current flows is four.

[0231] When the required power Wreq is within the range of the fourth region DP4, the control device 70 calculates the maximum efficient power Pmax4 in the case of four phases as the command power W*. Here, the fourth region DP4 is a region of the transmitted and received power in which the power conversion efficiency in the case of four phases is higher than the power conversion efficiency in the case of other numbers of phases. When the required power Wreq is within the range of the fifth region DP5, the control device 70 calculates the maximum efficient power Pmax5 in the case of five phases as the command power W*. Here, the fifth region DP5 is a region of the transmitted and received power in which the power conversion efficiency in the case of five phases is higher than the power conversion efficiency in the case of other numbers of phases.

[0232] The number of battery cells constituting the first storage battery 21 and the number of cells constituting the second storage battery 22 do not have to be the same.

[0233] The upper and lower arm switches constituting the switching device unit 31 are not limited to IGBTs, but may be, for example, N-channel MOSFETs. In this case, the high potential side terminal is the drain, and the low potential side terminal is the source.

[0234] The connection switch 61 is not limited to a relay. For example, a pair of N-channel MOSFETs with their sources connected to each other, or an IGBT may be used as the connection switch 61.

[0235] In the second and third embodiments, the air pressure sensor 51 and the temperature sensor 52 do not necessarily have to be provided.

[0236] The installation of the power conversion system 10 is not limited to a vehicle, and may be a moving body such as an aircraft or a ship. When the moving body is an aircraft, the rotating electric machine 40 serves as a power source for the aircraft to fly, and when the moving body is a ship, the rotating electric machine 40 serves as a power source for the ship to navigate. Furthermore, the installation of the power conversion system 10 is not limited to a moving body.

[0237] The control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by the computer. [Explanation of symbols]

[0238] 21, 22...first and second storage batteries, 30...inverter, QUH to QYH...U to Y phase upper arm switches, QUL to QYL...U to Y phase lower arm switches, 60...connection path, 61...connection switch, 70...control device.

Claims

1. A rotating electric machine (40) having star-connected windings (41U, 41V, 41W, 41X, 41Y); an inverter (30) having upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) connected in series; a connection path (60) electrically connecting a negative electrode side of the first storage unit (21, 32a) and a positive electrode side of the second storage unit (22, 32b) connected in series to a neutral point of the winding; a connection switch (61) that is provided in the connection path and that, when turned on, electrically connects a negative electrode side of the first storage unit and a positive electrode side of the second storage unit to the neutral point, and, when turned off, electrically disconnects the negative electrode side of the first storage unit and the positive electrode side of the second storage unit from the neutral point; A control device (70) for use in a system (10) comprising: a determination unit that determines whether or not to turn on the connection switch; a control unit that turns on the connection switch and performs switching control of the upper arm switch and the lower arm switch when the determination unit determines that the connection switch should be turned on; The control device performs a determination process in which, when it is determined that the amount of partial discharge occurring in the windings of the same phase is greater than a tolerance value, the determination unit determines to turn on the connection switch.

2. an atmospheric pressure information acquisition unit that acquires an atmospheric pressure or an altitude around the rotating electric machine; The control device according to claim 1 , wherein the determination unit performs a process of determining whether or not the amount of partial discharge is greater than the allowable value based on the value acquired by the atmospheric pressure information acquisition unit in the determination process.

3. a temperature acquisition unit that acquires a temperature of the winding or a temperature correlated with the temperature, The control device according to claim 1 or 2, wherein the determination unit performs a process of determining that the amount of partial discharge is greater than the allowable value on condition that the acquired temperature is equal to or greater than a temperature threshold value in the determination process.

4. A control device as described in any one of claims 1 to 3, wherein the judgment unit acquires a torque command value in the judgment process, and when the acquired torque command value is greater than the torque judgment value, performs a process of determining that the partial discharge amount is greater than the allowable value.

5. a current acquisition unit that acquires a current parameter that is a current flowing through the winding or a correlation value of the current, The control device according to any one of claims 1 to 3, wherein the determination unit performs a process of determining that the partial discharge amount is greater than the allowable value on the condition that the acquired current parameter crosses a current threshold value in the determination process.

6. a voltage acquisition unit that acquires a terminal voltage of a series connection of the first power storage unit and the second power storage unit or a voltage parameter that is a correlation value of the terminal voltage; The control device according to any one of claims 1 to 5, wherein the determination unit performs a process of determining that the partial discharge amount is greater than the allowable value, on the condition that the acquired voltage parameter is equal to or greater than a voltage threshold value, in the determination process.

7. A rotating electric machine (40) having star-connected windings (41U, 41V, 41W, 41X, 41Y); an inverter (30) having upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) connected in series; a connection path (60) electrically connecting a negative electrode side of the first storage unit (21, 32a) and a positive electrode side of the second storage unit (22, 32b) connected in series to a neutral point of the winding; a connection switch (61) that is provided in the connection path and that, when turned on, electrically connects a negative electrode side of the first storage unit and a positive electrode side of the second storage unit to the neutral point, and, when turned off, electrically disconnects the negative electrode side of the first storage unit and the positive electrode side of the second storage unit from the neutral point; A control device (70) for use in a system (10) comprising: a determination unit that determines whether or not to turn on the connection switch; a control unit that turns on the connection switch and performs switching control of the upper arm switch and the lower arm switch when the determination unit determines that the connection switch should be turned on; a voltage acquisition unit that acquires a voltage parameter that is a terminal voltage of each of the first power storage unit and the second power storage unit or a correlation value of the terminal voltages; Equipped with the determination unit determines to turn on the connection switch when a larger voltage parameter of the acquired voltage parameters of the first power storage unit and the second power storage unit is equal to or smaller than a voltage threshold value; When the control unit determines that the connection switch should be turned on, the control unit turns on the connection switch and causes a current to flow between the first storage unit and the second storage unit via the inverter, the winding, and the connection path, thereby performing the switching control to transfer energy from one of the first storage unit and the second storage unit to the other storage unit.

8. a power calculation unit that calculates power exchanged between the first power storage unit and the second power storage unit through the switching control, 8. The control device according to claim 7, wherein the control unit performs the switching control so that the power exchanged between the first power storage unit and the second power storage unit becomes the exchanged power calculated by the power calculation unit, and when the exchanged power calculated by the power calculation unit is large, the control unit sets a larger number of phases of the windings through which current flows by the switching control than when the exchanged power is small.

9. 9. The control device according to claim 8, wherein the power calculation unit calculates, as the transmitted / received power, a power determined in accordance with a number of phases of the winding through which a current flows and a power that maximizes power conversion efficiency in the switching control.

10. 9. The control device according to claim 8, wherein, when the control unit controls the power exchanged between the first power storage unit and the second power storage unit to the exchanged power, the control unit performs the switching control such that a number of phases of the winding through which a current flows becomes a number of phases that maximizes power conversion efficiency when power is exchanged between the first power storage unit and the second power storage unit.

11. The control device according to any one of claims 8 to 10, wherein the power calculation unit increases the transmitted and received power as the difference between the voltage parameter of the first storage unit and the voltage parameter of the second storage unit acquired by the voltage acquisition unit becomes larger.

12. The system is mounted on a moving object, The control device according to any one of claims 1 to 11, wherein the rotating electric machine is a power source for moving the moving body.

13. A rotating electric machine (40) having star-connected windings (41U, 41V, 41W, 41X, 41Y), an inverter (30) having upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) connected in series; a connection path (60) electrically connecting a negative electrode side of the first storage unit (21, 32a) and a positive electrode side of the second storage unit (22, 32b) connected in series to a neutral point of the winding; a connection switch (61) that is provided in the connection path and that, when turned on, electrically connects a negative electrode side of the first storage unit and a positive electrode side of the second storage unit to the neutral point, and, when turned off, electrically disconnects the negative electrode side of the first storage unit and the positive electrode side of the second storage unit from the neutral point; A program applied to a system (10) comprising: A computer (70) a determination process for determining whether or not to turn on the connection switch; a control process for turning on the connection switch and performing switching control of the upper arm switch and the lower arm switch when the determination process determines that the connection switch is to be turned on; Execute a process including The program determines, in the determination process, to turn on the connection switch when it is determined that the amount of partial discharge occurring in the winding of the same phase is greater than a tolerance value.

14. A rotating electric machine (40) having star-connected windings (41U, 41V, 41W, 41X, 41Y), an inverter (30) having upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) connected in series; a connection path (60) electrically connecting a negative electrode side of the first storage unit (21, 32a) and a positive electrode side of the second storage unit (22, 32b) connected in series to a neutral point of the winding; a connection switch (61) that is provided in the connection path and that, when turned on, electrically connects a negative electrode side of the first storage unit and a positive electrode side of the second storage unit to the neutral point, and, when turned off, electrically disconnects the negative electrode side of the first storage unit and the positive electrode side of the second storage unit from the neutral point; A program applied to a system (10) comprising: A computer (70) a determination process for determining whether or not to turn on the connection switch; a control process for turning on the connection switch and performing switching control of the upper arm switch and the lower arm switch when the determination process determines that the connection switch is to be turned on; a voltage acquisition process for acquiring a voltage parameter that is a terminal voltage of each of the first power storage unit and the second power storage unit or a correlation value of the terminal voltages; Execute a process including the determination process determines that the connection switch is to be turned on when a larger voltage parameter of the acquired voltage parameters of the first power storage unit and the second power storage unit is equal to or smaller than a voltage threshold value; In the control processing, when it is determined that the connection switch is to be turned on, a program that performs the switching control by turning on the connection switch and flowing a current between the first power storage unit and the second power storage unit via the inverter, the winding, and the connection path, thereby transferring energy from one of the first power storage unit and the second power storage unit to the other power storage unit.

15. A rotating electric machine (40) having star-connected windings (41U, 41V, 41W, 41X, 41Y), an inverter (30) having upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) connected in series; a connection path (60) electrically connecting a negative electrode side of the first storage unit (21, 32a) and a positive electrode side of the second storage unit (22, 32b) connected in series to a neutral point of the winding; a connection switch (61) that is provided in the connection path and that, when turned on, electrically connects a negative electrode side of the first storage unit and a positive electrode side of the second storage unit to the neutral point, and, when turned off, electrically disconnects the negative electrode side of the first storage unit and the positive electrode side of the second storage unit from the neutral point; A control method for a system (10) comprising: a determination step of determining whether or not to turn on the connection switch; a control step of turning on the connection switch and performing switching control of the upper arm switch and the lower arm switch when it is determined in the determination step that the connection switch is to be turned on; Including, In the determining step, when it is determined that an amount of partial discharge occurring in the windings of the same phase is greater than a permissible value, it is determined that the connection switch is to be turned on.

16. A rotating electric machine (40) having star-connected windings (41U, 41V, 41W, 41X, 41Y), an inverter (30) having upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) connected in series; a connection path (60) electrically connecting a negative electrode side of the first storage unit (21, 32a) and a positive electrode side of the second storage unit (22, 32b) connected in series to a neutral point of the winding; a connection switch (61) that is provided in the connection path and that, when turned on, electrically connects a negative electrode side of the first storage unit and a positive electrode side of the second storage unit to the neutral point, and, when turned off, electrically disconnects the negative electrode side of the first storage unit and the positive electrode side of the second storage unit from the neutral point; A control method for a system (10) comprising: a determination step of determining whether or not to turn on the connection switch; a control step of turning on the connection switch and performing switching control of the upper arm switch and the lower arm switch when it is determined in the determination step that the connection switch is to be turned on; a voltage acquiring step of acquiring a voltage parameter which is a terminal voltage of each of the first power storage unit and the second power storage unit or a correlation value of the terminal voltages; Including, in the determining step, when a larger one of the acquired voltage parameters of the first power storage unit and the second power storage unit is equal to or smaller than a voltage threshold value, it is determined that the connection switch is to be turned on; In the control step, when it is determined that the connection switch is to be turned on, the connection switch is turned on and a current is caused to flow between the first power storage unit and the second power storage unit via the inverter, the winding, and the connection path, thereby performing the switching control to transfer energy from one of the first power storage unit and the second power storage unit to the other power storage unit.

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