Control device for power converter, power conversion system, program, and control method for power converter

Abstract

A control device (16-19) is applied to a power conversion system (10). The power conversion system comprises a plurality of power storage unit modules (30, 60, 90, 130, 160, 190, 230, 260, 290) respectively including: power storage units (31, 61, 91, 131, 161, 191, 231, 261, 291); and power converters (40, 70, 100, 140, 170, 1100, 240, 270, 2100) that are electrically connected to the power storage units. The control device comprises: a voltage acquisition unit (16a) that acquires the terminal voltage of at least one among the power converters; and a control unit (16c) that performs switching control of the power converters so as to prevent the magnitude of an acquired terminal voltage from exceeding an upper limit voltage.

Description

Power converter control device, power conversion system, program, and power converter control method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2023-209101, filed on December 12, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a power converter control device, a power conversion system, a program, and a power converter control method.

[0003] A power conversion system having a power converter and a plurality of storage batteries is known. The power converter converts power between the storage batteries. An example of such a technology is disclosed in Patent Document 1.

[0004] JP 2022-23722 A

[0005] A plurality of power storage modules, each having a power storage unit and a power converter, may be electrically connected in parallel. In this case, it is desirable to appropriately realize a power conversion system in which the power storage modules are electrically connected in parallel.

[0006] The present disclosure has been made to solve the above-mentioned problems, and its main purpose is to provide a power converter control device, a power conversion system, a program, and a power converter control method that can appropriately realize a power conversion system in which multiple storage modules are electrically connected in parallel.

[0007] The present disclosure provides a system including a plurality of power storage modules, each having a power storage unit and a power converter electrically connected to the power storage unit, in which a power converter control device is applied to a power conversion system in which the power storage modules are electrically connected in parallel, the control device comprising: a voltage acquisition unit that acquires a terminal voltage of at least one of the power converters; and a control unit that performs switching control of the power converters so as to prevent the magnitude of the acquired terminal voltage from exceeding an upper limit voltage.

[0008] In a configuration in which multiple power storage modules are electrically connected in parallel, each power storage module shares the power required for the power conversion system. In this case, if the sharing of the power required is inappropriate, there is a concern that an overvoltage may be applied to at least one of the power converters. In this case, there is a concern that the power conversion system in which the power storage modules are electrically connected in parallel may not be properly realized.

[0009] Therefore, in the present disclosure, switching control of each power converter is performed to prevent the magnitude of the terminal voltage of at least one of the power converters from exceeding an upper voltage limit. In this case, each power storage module can perform power adjustment to prevent an overvoltage from being applied to each power converter. This makes it possible to prevent an overvoltage from being applied to the power converter while meeting the requirements for the power conversion system. As a result, a power conversion system in which each power storage module is electrically connected in parallel can be appropriately realized.

[0010] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. The drawings are as follows: Figure 1 is a configuration diagram of a power conversion system according to a first embodiment; Figure 2 is a diagram showing an example of a power converter; Figure 3 is a flowchart showing the processing procedure for overvoltage suppression control; Figure 4 is a diagram showing an example of redistribution processing in overvoltage suppression control; Figure 5 is a diagram showing an example of redistribution processing in overvoltage suppression control; Figure 6 is a diagram showing an example of redistribution processing in overvoltage suppression control; Figure 7 is a diagram showing an example of redistribution processing in overvoltage suppression control; Figure 8 is a flowchart showing the processing procedure for overcurrent suppression control; Figure 9 is a diagram showing an example of redistribution processing in overcurrent suppression control; Figure 10 is a diagram showing an example of redistribution processing in overcurrent suppression control; Figure 11 is a diagram showing an example of reduction processing in overcurrent suppression control; Figure 12 is a configuration diagram of a power conversion system according to a second embodiment; Figure 13 is a configuration diagram of a power conversion system according to another embodiment; Figure 14 is a configuration diagram of a power conversion system according to another embodiment; and Figure 15 is a configuration diagram of a power conversion system according to another embodiment.

[0011] Several embodiments will be described with reference to the drawings. In several embodiments, functionally and / or structurally corresponding and / or associated parts may be designated by the same reference numerals or reference numerals that differ in the hundredth or more digit. For corresponding and / or associated parts, reference may be made to the descriptions of other embodiments.

[0012] A first embodiment of a control device according to the present disclosure will now be described with reference to the drawings. In this embodiment, the control device constitutes a power conversion system mounted on an electrically powered vehicle such as an electric vehicle or a hybrid vehicle.

[0013] FIG. 1 shows a configuration diagram of a power conversion system 10 mounted on a vehicle. The power conversion system 10 includes a plurality of storage battery modules (corresponding to "power storage module"), and in this embodiment, includes three modules: a first storage battery module 30, a second storage battery module 60, and a third storage battery module 90. Each storage battery module 30, 60, 90 includes a storage battery 31, 61, 91 (corresponding to "power storage module"). Each storage battery 31, 61, 91 is, for example, a battery pack configured as a series connection of battery cells serving as single cells. The battery cells may be, for example, secondary batteries such as lithium-ion batteries.

[0014] A load 21 is electrically connected to a high-potential side terminal 11 and a low-potential side terminal 12 of the power conversion system 10. The high-potential side terminal 11 is electrically connected to the positive electrode sides of the storage battery modules 30, 60, and 90 via a high-potential side path 13 such as a bus bar. The low-potential side terminal 12 is electrically connected to the negative electrode sides of the storage battery modules 30, 60, and 90 via a low-potential side path 14 such as a bus bar. As a result, the storage battery modules 30, 60, and 90 are electrically connected in parallel to the load 21.

[0015] Specifically, the load 21 is a three-phase inverter 22 and a rotating electric machine 23 having armature windings corresponding to the number of phases and electrically connected to the inverter 22. The inverter 22 controls the current flowing through the windings of each phase. The rotating electric machine 23 is an on-board main engine, and a rotor of the rotating electric machine 23 is capable of transmitting power to the drive wheels of the vehicle. The rotating electric machine 23 is, for example, a permanent magnet synchronous machine.

[0016] The high-potential side path 13 is electrically connected to the positive electrode side of the inverter 22, and the low-potential side path 14 is electrically connected to the negative electrode side of the inverter 22. This enables current to flow between the power conversion system 10 and the load 21. The inverter 22 converts DC power supplied from the power conversion system 10 into AC power and supplies the power to each phase winding of the rotating electric machine 23. In this case, the rotating electric machine 23 serves as a power source for running the vehicle. The rotating electric machine 23 also generates regenerative power using rotational force applied to the rotor. The inverter 22 converts the generated AC power into DC power and outputs the power to the power conversion system 10.

[0017] Each storage battery module 30, 60, 90 includes a power converter 40, 70, 100. In each storage battery module 30, 60, 90, the power converter 40, 70, 100 is electrically connected to the storage battery 31, 61, 91 and the load 21. Hereinafter, the storage battery 31 and the power converter 40 of the first storage battery module 30 will be referred to as the "first storage battery 31" and the "first power converter 40," the storage battery 61 and the power converter 70 of the second storage battery module 60 will be referred to as the "second storage battery 61" and the "second power converter 70," and the storage battery 91 and the power converter 100 of the third storage battery module 90 will be referred to as the "third storage battery 91" and the "third power converter 100."

[0018] Next, a specific description will be given of the connection relationships between the storage batteries 31, 61, 91, the power converters 40, 70, 100, and the load 21 in each of the storage battery modules 30, 60, 90. First, the first storage battery module 30 will be described as an example.

[0019] The first power converter 40 includes a primary-side positive terminal 41 and a primary-side negative terminal 42 that constitute a primary-side terminal pair, and a secondary-side positive terminal 43 and a secondary-side negative terminal 44 that constitute a secondary-side terminal pair. The primary-side positive terminal 41 of the first power converter 40 is electrically connected to the positive electrode side of the first storage battery 31. The primary-side negative terminal 42 of the first power converter 40 and the negative electrode side of the first storage battery 31 are electrically connected to the inverter 22 via the low-potential-side path 14. In other words, the primary-side terminal pair of the first power converter 40 is electrically connected in parallel to the first storage battery 31. In this case, the voltage of the first storage battery 31 is applied to the primary-side terminal pair of the first power converter 40.

[0020] A secondary-side negative terminal 44 of the first power converter 40 is electrically connected to the positive electrode side of the first storage battery 31. A secondary-side positive terminal 43 of the first power converter 40 is electrically connected to the inverter 22 via the high-potential-side path 13. In other words, the secondary-side terminal pair of the first power converter 40 is electrically connected in series to the first storage battery 31 on the positive electrode side of the first storage battery 31.

[0021] The second power converter 70 includes a primary-side positive terminal 71 and a primary-side negative terminal 72 that constitute a primary-side terminal pair, and a secondary-side positive terminal 73 and a secondary-side negative terminal 74 that constitute a secondary-side terminal pair. The third power converter 100 includes a primary-side positive terminal 101 and a primary-side negative terminal 102 that constitute a primary-side terminal pair, and a secondary-side positive terminal 103 and a secondary-side negative terminal 104 that constitute a secondary-side terminal pair. In the second and third storage battery modules 60 and 90, the connections between the terminals 71 to 74 and 101 to 104 of the corresponding power converters 70 and 100, the corresponding storage batteries 61 and 91, and the load 21 are similar to those in the first storage battery module 30, although detailed description will be omitted. In other words, the storage battery modules 30, 60, and 90 are electrically connected in parallel to the load 21.

[0022] In each storage battery module 30, 60, 90, the secondary-side terminal voltages Vo1, Vo2, and Vo3 applied to the secondary-side terminal pairs of the power converters 40, 70, and 100 are the differential voltages between the voltages between the paths 13 and 14 (specifically, the voltages supplied to the inverter 22) and the voltages Vbat1, Vbat2, and Vbat3 of the corresponding storage batteries 31, 61, and 91. The secondary-side terminal voltages Vo1, Vo2, and Vo3 of each storage battery module 30, 60, and 90 are lower than the rated voltages (e.g., 400 V) of the corresponding storage batteries 31, 61, and 91. Therefore, the rated secondary voltages on the secondary sides of the power converters 40, 70, and 100 are set lower than the rated voltages of the corresponding storage batteries 31, 61, and 91, e.g., 16 V. This allows the power converters 40, 70, and 100 to be miniaturized.

[0023] FIG. 2 shows an example of a first power converter 40. The first power converter 40 is an isolated DC-DC converter. The first power converter 40 includes first to eighth switches S1 to S8, a primary-side capacitor 51, a secondary-side capacitor 52, and a transformer 53. In this embodiment, voltage-controlled semiconductor switching elements, more specifically, N-channel MOSFETs, are used as the first to eighth switches S1 to S8. In this case, the high-potential side terminal of each switch S1 to S8 is the drain, and the low-potential side terminal is the source. Each switch S1 to S8 also has a body diode.

[0024] The drain of the first switch S1 and the drain of the third switch S3 are electrically connected to the primary-side positive terminal 41 and a first end of the primary-side capacitor 51. The source of the first switch S1 is connected to the drain of the second switch S2, and the source of the third switch S3 is connected to the drain of the fourth switch S4. The sources of the second switch S2 and the fourth switch S4 are electrically connected to the primary-side negative terminal 42 and the second end of the primary-side capacitor 51.

[0025] The drain of the fifth switch S5 and the drain of the seventh switch S7 are electrically connected to the secondary-side positive terminal 43 and the first end of the secondary-side capacitor 52. The source of the fifth switch S5 is connected to the drain of the sixth switch S6, and the source of the seventh switch S7 is connected to the drain of the eighth switch S8. The sources of the sixth switch S6 and the eighth switch S8 are electrically connected to the secondary-side negative terminal 44 and the second end of the secondary-side capacitor 52.

[0026] The transformer 53 includes a primary winding 53a and a secondary winding 53b, which are wound around a common core. As a result, the primary winding 53a and the secondary winding 53b are magnetically coupled by the common core. When the potential at the first end of the primary winding 53a becomes higher relative to the second end, an induced voltage is generated such that the potential at the first end of the secondary winding 53b becomes higher than the potential at the second end. On the other hand, when the potential at the second end of the primary winding 53a becomes higher relative to the first end, an induced voltage is generated such that the potential at the second end of the secondary winding 53b becomes higher than the potential at the first end.

[0027] A first end of the primary winding 53a is electrically connected to the connection point of the first switch S1 and the second switch S2, a second end of the primary winding 53a is electrically connected to the connection point of the third switch S3 and the fourth switch S4, a first end of the secondary winding 53b is connected to the connection point of the seventh switch S7 and the eighth switch S8, and a second end of the secondary winding 53b is electrically connected to the connection point of the fifth switch S5 and the sixth switch S6.

[0028] The second power converter 70 and the third power converter 100 are isolated DC-DC converters, and similar to the first power converter 40, each of them includes first to eighth switches, a primary-side capacitor, a secondary-side capacitor, and a transformer. In this embodiment, the first power converter 40, the second power converter 70, and the third power converter 100 have basically the same configuration, and therefore detailed description of the second power converter 70 and the third power converter 100 will be omitted.

[0029] The power conversion system 10 includes battery monitoring devices 32, 62, and 92. The battery monitoring devices 32, 62, and 92 are provided corresponding to the respective storage batteries 31, 61, and 91. For example, the first battery monitoring device 32 detects the terminal voltage, current, internal resistance, SOC, and the like of each battery cell constituting the first storage battery 31, and monitors the state of the first storage battery 31. The second battery monitoring device 62 monitors the state of the second storage battery 61, similar to the first battery monitoring device 32. The third battery monitoring device 92 monitors the state of the third storage battery 91, similar to the first battery monitoring device 32. The detected values ​​detected by the battery monitoring devices 32, 62, and 92 are input to the control device 16 provided in the power conversion system 10.

[0030] The power conversion system 10 includes voltage sensors 45, 75, 105 and current sensors 46, 76, 106. The voltage sensors 45, 75, 105 and current sensors 46, 76, 106 are provided corresponding to each storage battery module 30, 60, 90. Each voltage sensor 45, 75, 105 detects a secondary-side terminal voltage Vo1, Vo2, Vo3 of the corresponding power converter 40, 70, 100. Each current sensor 46, 76, 106 detects a secondary-side current Io1, Io2, Io3 flowing through the secondary side of the corresponding power converter 40, 70, 100. Specifically, taking the first power converter 40 as an example, as shown in FIG. 2 , the voltage sensor 45 detects the voltage of the secondary-side capacitor 52. The current sensor 46 detects a current flowing through the secondary-side positive terminal 43 and the first end of the secondary-side capacitor 52. The detected values ​​of the sensors 45 , 46 , 75 , 76 , 105 , and 106 are input to the control device 16 .

[0031] The control device 16 is an ECU (electronic control unit) primarily composed of a microcomputer equipped with a CPU and various memories. The functions provided by the microcomputer can be provided by software stored in a physical memory device and a computer executing the software, software alone, hardware alone, or a combination thereof. For example, when the microcomputer is provided by hardware electronic circuits, the functions can be provided by digital circuits including numerous logic circuits or analog circuits. For example, the microcomputer executes programs stored in a non-transitory tangible storage medium serving as its own storage unit. The programs include, for example, programs for the processes shown in Figures 3 and 8. Execution of the programs results in the execution of a method corresponding to the programs. The storage unit is, for example, a non-volatile memory. The programs stored in the storage unit can be downloaded and updated via a communication network such as the Internet, for example, via OTA (Over the Air).

[0032] The control device 16 performs switching control of each of the power converters 40, 70, and 100. In this embodiment, the control device 16 controls the module current of each of the storage battery modules 30, 60, and 90 in order to supply a required current to the power conversion system 10 during switching control. The module current is specifically the secondary current Io1, Io2, and Io3 of each of the storage battery modules 30, 60, and 90. The control device 16 sets current command values ​​for the secondary currents Io1, Io2, and Io3 in each of the storage battery modules 30, 60, and 90 based on the required current to the power conversion system 10. The control device 16 performs switching control of each of the power converters 40, 70, and 100 based on the set current command values. As a result, the required current share is distributed to each of the storage battery modules 30, 60, and 90.

[0033] For example, the control device 16 sets a current command value based on a required current corresponding to the driving state of the rotating electric machine 23. Specifically, a request may arise to flow a current from the power conversion system 10 to the rotating electric machine 23 in order to power the rotating electric machine 23. In this case, the control device 16 sets a current command value that causes at least one of the storage batteries 31, 61, and 91 to discharge. Also, a request may arise to flow a current from the rotating electric machine 23 to the power conversion system 10 in order to regeneratively drive the rotating electric machine 23. In this case, the control device 16 sets a current command value that causes at least one of the storage batteries 31, 61, and 91 to charge.

[0034] For example, the control device 16 sets the current command value based on a required current according to the state of each storage battery 31, 61, 91. More specifically, a request may arise to exchange power between the storage batteries 31, 61, 91 in order to control the amount of charge (e.g., SOC) of each storage battery 31, 61, 91. In this case, the control device 16 sets a current command value that causes some of the storage batteries 31, 61, 91 to be discharged and at least some of the remaining storage batteries 31, 61, 91 to be charged.

[0035] Note that, for example, a request may arise to exchange power between the rotating electric machine 23 and each storage battery 31, 61, 91 in order to drive the rotating electric machine 23 in power running or regenerative driving and control the amount of electricity stored in each storage battery 31, 61, 91. In this case, too, the control device 16 sets a current command value that discharges some of the storage batteries 31, 61, 91 and charges at least some of the remaining storage batteries 31, 61, 91. Control of the amount of electricity stored in each storage battery 31, 61, 91 is performed, for example, to equalize the amount of electricity stored in each storage battery 31, 61, 91 or to charge or discharge only a specific storage battery among the storage batteries 31, 61, 91.

[0036] However, there is a concern that an overvoltage may be applied to at least one secondary-side terminal pair of each of the power converters 40, 70, 100 due to an inappropriate distribution of the required current in each of the storage battery modules 30, 60, 90. In this case, there is a concern that the power conversion system 10 in which the storage battery modules 30, 60, 90 are electrically connected in parallel may not be properly realized.

[0037] Therefore, the control device 16 performs overvoltage suppression control during the execution of switching control. The overvoltage suppression control is control for suppressing application of an overvoltage to the secondary-side terminal pairs of each of the power converters 40, 70, and 100.

[0038] Specifically, in the overvoltage suppression control, the control device 16 acquires the secondary-side terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90. The control device 16 then performs switching control of the power converters 40, 70, and 100 so as to suppress the magnitudes of the acquired secondary-side terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90 from exceeding an upper limit voltage VT. The upper limit voltage VT is determined according to the secondary-side rated voltage of the power converter 40, 70, and 100, and is set to a value between 80% and 90% or between 90% and 100% of the secondary-side rated voltage, for example.

[0039] In the present embodiment, in the overvoltage suppression control, power adjustment for suppressing application of an overvoltage to the secondary-side terminal pairs of each power converter 40, 70, 100 can be performed by each storage battery module 30, 60, 90. This makes it possible to suppress application of an overvoltage to each power converter 40, 70, 100 while meeting the requirements for the power conversion system 10. As a result, it is possible to appropriately realize the power conversion system 10 in which the storage battery modules 30, 60, 90 are electrically connected in parallel.

[0040] In each storage battery module 30, 60, 90, the primary terminal pairs of the power converters 40, 70, 100 are electrically connected in parallel to the storage batteries 31, 61, 91, and the secondary terminal pairs are electrically connected in series to the storage batteries 31, 61, 91. In this configuration, the rated voltage of each power converter 40, 70, 100 may be set lower than the voltage of each storage battery 31, 61, 91, or the secondary terminal voltages Vo1, Vo2, Vo3 of each power converter 40, 70, 100 may be affected by the voltage of the corresponding storage battery 31, 61, 91. In this case, there is a relatively high possibility that an overvoltage will be applied to the secondary terminal pairs of each power converter 40, 70, 100. Therefore, there is a significant advantage to performing overvoltage suppression control during execution of switching control.

[0041] The overvoltage suppression control will be specifically described below.

[0042] The control device 16 includes a voltage acquisition unit 16a, a voltage determination unit 16b, and a control unit 16c. The voltage acquisition unit 16a acquires the secondary terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90. In this embodiment, the voltage acquisition unit 16a acquires the secondary terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90 from the following: detected voltages of the voltage sensors 45, 75, and 105; and calculated values ​​of the secondary terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90. The secondary terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90 can be calculated using the detected values ​​of the corresponding battery monitoring devices 32, 62, and 92. Specifically, the voltages Vbat1, Vbat2, and Vbat3 of the storage batteries 31, 61, and 91 detected by the battery monitoring devices 32, 62, and 92 can be used to calculate the secondary-side terminal voltages Vo1, Vo2, and Vo3 of the corresponding storage battery modules 30, 60, and 90. Furthermore, the battery parameters detected by the battery monitoring devices 32, 62, and 92 can be used to calculate the secondary-side terminal voltages Vo1, Vo2, and Vo3 of the corresponding storage battery modules 30, 60, and 90. The battery parameters are parameters that correlate with the voltages Vbat1, Vbat2, and Vbat3 of the storage batteries, such as the currents Ibat1, Ibat2, and Ibat3 flowing through the respective storage batteries 31, 61, and 91, the internal resistance, and the SOC.

[0043] The voltage determination unit 16b determines whether there is an overvoltage module based on the acquired secondary terminal voltages Vo1, Vo2, Vo3 of each storage battery module 30, 60, 90. An overvoltage module is a storage battery module among the storage battery modules 30, 60, 90 whose secondary terminal voltages Vo1, Vo2, Vo3 exceed the upper limit voltage VT.

[0044] According to this embodiment, during overvoltage suppression control, the detected voltages of the voltage sensors 45, 75, and 105 are acquired. This allows the secondary terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90 to be properly determined. This allows for a configuration suitable for determining whether or not there is an overvoltage module.

[0045] Furthermore, in the overvoltage suppression control, the calculated values ​​of the secondary terminal voltages Vo1, Vo2, and Vo3 are acquired, thereby improving the accuracy of determining whether or not there is an overvoltage module.

[0046] If it is determined that there is an over-voltage module, the control unit 16c performs a redistribution process. The redistribution process is a process of redistributing the required current share to each storage battery module 30, 60, 90. In the redistribution process, the control unit 16c changes the secondary current so as to reduce the magnitude of the secondary terminal voltage of the over-voltage module. Then, the control unit 16c changes the secondary current of the storage battery modules 30, 60, 90 other than the over-voltage module in accordance with the change in the secondary current of the over-voltage module. For example, in the redistribution process, the control unit 16c changes the secondary current of each storage battery module 30, 60, 90 by resetting a current command value in switching control.

[0047] By reducing the magnitude of the secondary terminal voltage of the over-voltage module, it is possible to accurately prevent an overvoltage from being applied to the power converter corresponding to the over-voltage module. Furthermore, by changing the secondary current of the storage battery modules 30, 60, 90 other than the over-voltage module, it is possible to compensate for the change in the secondary current of the over-voltage module. Therefore, it is possible to accurately prevent an overvoltage from being applied to each power converter 40, 70, 100 while meeting the requirements of the power conversion system 10.

[0048] 3 shows a procedure for the overvoltage suppression control executed by the control device 16. This control is repeatedly executed at predetermined intervals during the execution of the switching control.

[0049] In step S10, the voltage acquisition unit 16a acquires the secondary terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90. In step S11, the voltage determination unit 16b determines whether or not there is an overvoltage module based on the acquired secondary terminal voltages Vo1, Vo2, and Vo3. If the determination in step S11 is negative, the process proceeds to step S12. On the other hand, if the determination in step S11 is positive, the process proceeds to step S13.

[0050] In step S12, the control unit 16c continues the current switching control in each of the power converters 40, 70, and 100. In this case, the current secondary-side currents Io1, Io2, and Io3 are maintained in each of the storage battery modules 30, 60, and 90. This allows the state in which no overvoltage occurs to continue.

[0051] In step S13, the control unit 16c performs a redistribution process. The redistribution process will be specifically described below for each state of the storage batteries 31, 61, and 91.

[0052] 4 to 7 compare the secondary terminal voltages Vo1, Vo2, and Vo3 and the secondary currents Io1, Io2, and Io3 of the storage battery modules 30, 60, and 90 before and after the redistribution process. Before the redistribution process, the secondary terminal voltages Vo1 and Vo3 of the first and third storage battery modules 30 and 90 are equal to or lower than the upper limit voltage VT, and the secondary terminal voltage Vo2 of the second storage battery module 60 exceeds the upper limit voltage VT. In other words, of the storage battery modules 30, 60, and 90, the second storage battery module 60 is an over-voltage module.

[0053] Here, possible causes of an overvoltage module include differences in the voltage and other characteristics of the storage batteries 31, 61, and 91. Specifically, in a storage battery module 30, 60, and 90 where the storage battery 31, 61, and 91 has a low voltage, the differential voltage between the voltage across the paths 13 and 14 and the storage battery voltage is high. In this case, the secondary terminal voltage of a storage battery module 30, 60, and 90 where the differential voltage is high may exceed the upper limit voltage VT. The voltages of the storage batteries 31, 61, and 91 may differ from each other in their initial states or due to changes in the internal resistance of the storage batteries 31, 61, and 91 caused by deterioration. For example, a storage battery 31, 61, and 91 with a high internal resistance will have a lower voltage during discharge than a storage battery with a low internal resistance, even when the same amount of discharge current is flowing.

[0054] 4, it is assumed that there is a request to power the rotating electric machine 23. In this case, the storage battery modules 30, 60, and 90 share and output the current flowing from the power conversion system 10 to the inverter 22. Therefore, the storage batteries 31, 61, and 91 are discharged.

[0055] The control unit 16c performs switching control of the second power converter 70 so as to reduce the magnitude of the secondary current Io2 in the second storage battery module 60 by an adjustment amount ΔIo. This reduces the discharge current of the second storage battery 61. In this case, the amount of voltage drop across the internal resistance of the second storage battery 61 during discharge is reduced, and the voltage of the second storage battery 61 increases. This reduces the differential voltage between the voltage across each of the paths 13 and 14 and the voltage of the second storage battery 61. Therefore, after the redistribution process is performed, the secondary terminal voltage Vo2 of the second storage battery module 60 is reduced by ΔVo2, and the secondary terminal voltage Vo2 becomes equal to or lower than the upper limit voltage VT.

[0056] Furthermore, the control unit 16c performs switching control of the first power converter 40 so as to increase the magnitude of the secondary-side current Io1 in the first storage battery module 30 by the adjustment amount ΔIo. This makes it possible to maintain the magnitude of the current flowing from the power conversion system 10 to the inverter 22 before and after the redistribution process. Therefore, in the switching control for discharging each of the storage batteries 31, 61, 91, it is possible to suppress the occurrence of overvoltage while performing power running of the rotating electric machine 23 in the same manner as before the redistribution process.

[0057] The control unit 16c may increase the magnitude of the secondary current Io3 in the third storage battery module 90 to compensate for the adjustment amount ΔIo (specifically, the reduction) of the secondary current Io2 in the second storage battery module 60. The control unit 16c may increase the magnitude of the secondary currents Io1 and Io3 in both the first and third storage battery modules 30 and 90 to compensate for the adjustment amount ΔIo (specifically, the reduction) of the secondary current Io2 in the second storage battery module 60.

[0058] 5 assumes a case where a request has been made to regeneratively drive the rotating electric machine 23. In this case, the storage battery modules 30, 60, and 90 share the current flowing from the inverter 22 to the power conversion system 10 and receive the power. Therefore, the storage batteries 31, 61, and 91 are charged.

[0059] The control unit 16c performs switching control of the second power converter 70 so as to increase the magnitude of the secondary current Io2 in the second storage battery module 60 by the adjustment amount ΔIo. This increases the charging current of the second storage battery 61. In this case, the amount of voltage drop across the internal resistance of the second storage battery 61 during charging increases, and the voltage of the second storage battery 61 during charging increases. This reduces the differential voltage between the voltages across the paths 13 and 14 and the voltage of the second storage battery 61. Therefore, after the redistribution process is executed, the secondary terminal voltage Vo2 of the second storage battery module 60 is reduced, and the secondary terminal voltage Vo2 becomes equal to or lower than the upper limit voltage VT.

[0060] Furthermore, the control unit 16c performs switching control of the first power converter 40 so as to reduce the magnitude of the secondary-side current Io1 in the first storage battery module 30 by the adjustment amount ΔIo. This makes it possible to maintain the magnitude of the current flowing from the inverter 22 to the power conversion system 10 before and after the redistribution process. Therefore, in the switching control for charging each of the storage batteries 31, 61, 91, it is possible to suppress the occurrence of overvoltage while performing regenerative driving of the rotating electric machine 23 in the same manner as before the redistribution process.

[0061] The control unit 16c may reduce the magnitude of the secondary currents Io1 and Io3 in at least one of the first and third battery modules 30 and 90 to compensate for the adjustment amount ΔIo (specifically, the increase amount) of the secondary current Io2 in the second battery module 60.

[0062] 6 assumes a case where the rotating electric machine 23 is powered and there is a demand to increase the amount of electricity stored in the third storage battery 91. In this case, the first and second storage battery modules 30, 60 share and output the current supplied to the inverter 22 and the third storage battery module 90. Therefore, the first and second storage batteries 31, 61 are discharged, and the third storage battery 91 is charged.

[0063] The control unit 16c performs switching control of the second power converter 70 so as to reduce the magnitude of the secondary-side current Io2 in the second storage battery module 60 by an adjustment amount ΔIo. As a result, the secondary-side terminal voltage Vo2 in the second storage battery module 60 becomes equal to or lower than the upper limit voltage VT, as in the case described with reference to FIG.

[0064] Furthermore, the control unit 16c performs switching control of the third power converter 100 so as to reduce the magnitude of the secondary-side current Io3 in the third storage battery module 90 by the adjustment amount ΔIo. This makes it possible to maintain the magnitude of the current flowing from the power conversion system 10 to the inverter 22 before and after the redistribution process. Therefore, in the switching control that discharges the first and second storage batteries 31, 61 and charges the third storage battery 91, it is possible to suppress the occurrence of overvoltage while performing the power running drive of the rotating electric machine 23 in the same manner as before the redistribution process.

[0065] The control unit 16c may increase the magnitude of the secondary current Io1 in the first storage battery module 30 to compensate for the adjustment amount ΔIo (reduction) of the secondary current Io2 in the second storage battery module 60. Alternatively, the control unit 16c may increase the magnitude of the secondary current Io1 in the first storage battery module 30 and reduce the magnitude of the secondary current Io3 in the third storage battery module 90 to compensate for the adjustment amount ΔIo of the secondary current Io2 in the second storage battery module 60.

[0066] 7 assumes a case where the rotating electric machine 23 is powered and there is a demand to increase the amount of electricity stored in the second storage battery 61. In this case, the first and third storage battery modules 30, 90 share and output the current supplied to the inverter 22 and the second storage battery module 60. Therefore, the first and third storage batteries 31, 91 are discharged, and the second storage battery 61 is charged.

[0067] The control unit 16c performs switching control of the second power converter 70 so as to increase the magnitude of the secondary-side current Io2 in the second storage battery module 60 by an adjustment amount ΔIo. As a result, the secondary-side terminal voltage Vo2 in the second storage battery module 60 becomes equal to or lower than the upper limit voltage VT, as in the case described with reference to FIG.

[0068] Furthermore, the control unit 16c performs switching control of the third power converter 100 so as to increase the magnitude of the secondary-side current Io3 in the third storage battery module 90 by the adjustment amount ΔIo. This makes it possible to maintain the magnitude of the current flowing from the power conversion system 10 to the inverter 22 before and after the redistribution process. Therefore, in the switching control that discharges the first and third storage batteries 31, 91 and charges the second storage battery 61, it is possible to suppress the occurrence of overvoltage while performing the power running drive of the rotating electric machine 23 in the same manner as before the redistribution process.

[0069] The control unit 16c may increase the secondary currents Io1 and Io3 in at least one of the first and third storage battery modules 30 and 60 to compensate for the adjustment amount ΔIo (increase) of the secondary current Io2 in the second storage battery module 60.

[0070] 4 to 7 , the secondary-side terminal voltage of one of the first and third storage battery modules 30, 90 increases with the change in the secondary-side current (see ΔVo1 and ΔVo3). Therefore, the control unit 16c may select the storage battery module with the lower secondary-side terminal voltage Vo1 or Vo3 from among the first and third storage battery modules 30, 90, and change the magnitude of the secondary-side current in the selected storage battery module. This allows the appropriate selection of the storage battery module whose secondary-side terminal voltage is to be increased, and the process of changing the secondary-side currents Io1, Io2, and Io3 of each storage battery module 30, 60, and 90 to be performed.

[0071] Here, there is a concern that, during the execution of the switching control, an overcurrent may flow in at least one of the storage battery modules 30, 60, 90. For example, when the overvoltage suppression control is executed, the magnitude of the secondary current in the storage battery modules other than the overvoltage module among the storage battery modules 30, 60, 90 may be increased to compensate for the adjustment of the secondary current for the overvoltage module. In this case, there is a concern that an overcurrent may flow in the storage battery module in which the magnitude of the secondary current is increased.

[0072] Therefore, in this embodiment, the control device 16 performs overcurrent suppression control during execution of switching control. The overcurrent suppression control is control to suppress overcurrent from flowing through the secondary terminal pairs of each of the power converters 40, 70, and 100.

[0073] The overcurrent suppression control will be specifically described below.

[0074] The control device 16 includes a current obtaining unit 16d, a current determination unit 16e, and a distribution determination unit 16f. In the present embodiment, the current obtaining unit 16d obtains the secondary currents Io1, Io2, and Io3 of the storage battery modules 30, 60, and 90. The currents detected by the current sensors 46, 76, and 106 can be used as the secondary currents Io1, Io2, and Io3 of the storage battery modules 30, 60, and 90.

[0075] The current determination unit 16e determines whether or not there is an excess current module based on the acquired secondary-side currents Io1, Io2, and Io3 of each storage battery module 30, 60, and 90. An excess current module is a storage battery module among the storage battery modules 30, 60, and 90 in which the magnitude of the acquired secondary-side current Io1, Io2, and Io3 exceeds an upper limit current IT. The upper limit current IT is determined based on at least one of the secondary-side rated current of each power converter 40, 70, and 100 and the rated current of each storage battery 31, 61, and 91, and is set to, for example, a value between 80% and 90% or between 90% and 100% of the secondary-side rated current.

[0076] When it is determined that there is an excess current module, the distribution determination unit 16f determines whether or not to perform redistribution processing based on the acquired secondary side terminal voltages Vo1, Vo2, and Vo3. The determination processing by the distribution determination unit 16f will be described later.

[0077] When it is determined that the redistribution process should be executed, the control unit 16c performs the redistribution process. In this case, the control unit 16c controls the switching of the power converters 40, 70, and 100 so as to distribute the excess of the secondary current in the current-excess module over the upper limit current IT to the storage battery modules 30, 60, and 90 other than the current-excess module.

[0078] On the other hand, when it is determined that the redistribution process is not to be executed, the control unit 16c executes the reduction process. In this case, in the reduction process, the control unit 16c controls the switching of the power converters 40, 70, and 100 so as to reduce the total current of the secondary currents Io1, Io2, and Io3 in the storage battery modules 30, 60, and 90.

[0079] 8 shows a processing procedure of the overcurrent suppression control executed by the control device 16. This control is repeatedly executed at a predetermined cycle in parallel with the overvoltage suppression control while the switching control is being executed.

[0080] In step S20, the voltage acquiring unit 16a acquires the secondary terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90. The current acquiring unit 16d acquires the secondary currents Io1, Io2, and Io3 of the storage battery modules 30, 60, and 90.

[0081] In step S21, the current determination unit 16e determines whether or not there is an excess current module based on the acquired secondary-side currents Io1, Io2, and Io3 of each storage battery module 30, 60, and 90. If a negative determination is made in step S21, the process proceeds to step S22. In step S22, the control unit 16c continues the current switching control of each power converter 40, 70, and 100. In this case, the current secondary-side currents Io1, Io2, and Io3 of each storage battery module 30, 60, and 90 are maintained. This allows a state in which no overcurrent occurs to continue. Note that even if a process for maintaining the secondary-side currents Io1, Io2, and Io3 is performed in step S22, if a positive determination is made in step S11 of FIG. 3 , a redistribution process in the overvoltage suppression control may be performed to change the secondary-side currents Io1, Io2, and Io3.

[0082] If the determination in step S21 is affirmative, the process proceeds to step S23. In step S23, the allocation determination unit 16f determines, based on the acquired secondary-side terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90, whether or not the secondary-side terminal voltages Vo1, Vo2, and Vo3 are likely to exceed the upper limit voltage VT as a result of the execution of the redistribution process. Here, the secondary-side terminal voltages Vo1, Vo2, and Vo3 can be changed between their current values ​​and the upper limit voltage VT. Therefore, in this embodiment, the allocation determination unit 16f calculates the remaining voltages until the acquired secondary-side terminal voltages Vo1, Vo2, and Vo3 of the storage battery modules 30, 60, and 90 reach the upper limit voltage VT. Based on the calculated remaining voltages, the allocation determination unit 16f determines whether or not the secondary-side terminal voltages Vo1, Vo2, and Vo3 are likely to exceed the upper limit voltage VT as a result of the execution of the redistribution process.

[0083] For example, when the allocation determination unit 16f determines that there is a remaining voltage (e.g., the remaining voltage is higher than 0) in a storage battery module of the storage battery modules 30, 60, 90 whose secondary-side terminal voltage is increased by the execution of the redistribution process, the allocation determination unit 16f makes a negative determination in step S23. On the other hand, when the allocation determination unit 16f determines that there is no remaining voltage (e.g., the remaining voltage is 0) in a storage battery module of the storage battery modules 30, 60, 90 whose secondary-side terminal voltage is increased by the execution of the redistribution process, the allocation determination unit 16f makes a positive determination in step S23.

[0084] If the determination in step S23 is negative, the process proceeds to step S24. In step S24, the distribution determination unit 16f determines whether the current secondary currents Io1, Io2, and Io3 can be adjusted by the redistribution process based on the acquired secondary currents Io1, Io2, and Io3 in each storage battery module 30, 60, and 90. Here, each secondary current Io1, Io2, and Io3 can be adjusted from its current value until it reaches the upper limit current IT. Therefore, in this embodiment, the distribution determination unit 16f calculates an adjustable current until the magnitude of the acquired secondary currents Io1, Io2, and Io3 in each storage battery module 30, 60, and 90 reaches the upper limit current IT. Based on the calculated adjustable currents, the distribution determination unit 16f determines whether the current secondary currents Io1, Io2, and Io3 can be adjusted by the redistribution process.

[0085] For example, when the distribution determination unit 16f determines that there is an adjustable current (for example, the adjustable current is greater than 0) in a storage battery module of the storage battery modules 30, 60, 90 in which the magnitude of the secondary current is increased by the execution of the redistribution process, the distribution determination unit 16f makes a positive determination in step S24. On the other hand, when the distribution determination unit 16f determines that there is no adjustable current (for example, the adjustable current is 0) in a storage battery module of the storage battery modules 30, 60, 90 in which the magnitude of the secondary current is increased by the execution of the redistribution process, the distribution determination unit 16f makes a negative determination in step S24.

[0086] If the determination in step S24 is affirmative, the distribution determination unit 16f determines to execute the redistribution process, and the process proceeds to step S25. In step S25, the control unit 16c executes the redistribution process. If the determination in step S23 is affirmative or if the determination in step S24 is negative, the distribution determination unit 16f determines not to execute the redistribution process, and the process proceeds to step S26. In step S26, the control unit 16c executes the reduction process. Note that if the determination in step S23 is negative without executing the process in step S24, the distribution determination unit 16f may determine to execute the redistribution process.

[0087] An example of overcurrent suppression control is shown in Figures 9, 10, and 11. In Figures 9 to 11, the first battery module 30 of the battery modules 30, 60, and 90 is the excess current module. In Figures 9 and 11, the batteries 31, 61, and 91 are being discharged. In Figure 10, the batteries 31, 61, and 91 are being charged.

[0088] In Fig. 9, the distribution determination unit 16f determines that the second and third storage battery modules 60 and 90 have remaining voltages Va2 and Va3, respectively, and makes a negative determination in step S23 in Fig. 8. The distribution determination unit 16f also determines that the second and third storage battery modules 60 and 90 have adjustable currents Ia2 and Ia3, respectively, and makes a positive determination in step S24 in Fig. 8. Therefore, the control unit 16c executes the redistribution process.

[0089] In the redistribution process, the control unit 16c performs switching control of the first power converter 40 so as to reduce the magnitude of the secondary-side current Io1 in the first storage battery module 30 by an adjustment amount ΔIo. The control unit 16c adjusts the secondary-side current Io1 in the first storage battery module 30 within a range in which the secondary-side terminal voltages Vo2 and Vo3 of the second and third storage battery modules 60 and 90, which compensate for the adjustment amount ΔIo, do not exceed the upper limit voltage VT. Here, the control unit 16c sets the adjustment amount ΔIo of the secondary-side current Io1 to be greater than the amount by which the secondary-side current Io1 exceeds the upper limit current IT. Therefore, after the redistribution process is performed, the magnitude of the secondary-side current Io1 in the first storage battery module 30 is equal to or less than the upper limit current IT.

[0090] Furthermore, in the redistribution process, the control unit 16c distributes the adjustment amount ΔIo of the secondary-side current Io1 in the first storage battery module 30 to the second storage battery module 60. In other words, the control unit 16c controls the switching of the second power converter 70 so as to increase the magnitude of the secondary-side current Io2 in the second storage battery module 60 by the adjustment amount ΔIo. Accordingly, the secondary-side terminal voltage Vo2 increases by ΔVo2. In FIG. 9 , the increase amount ΔVo2 of the secondary-side terminal voltage Vo2 in the second storage battery module 60 is lower than the remaining voltage Va2, and the adjustment amount ΔIo of the secondary-side current Io2 is smaller than the adjustable current Ia2. Therefore, in the second storage battery module 60 after the redistribution process is executed, the secondary-side terminal voltage Vo2 is set to be equal to or lower than the upper limit voltage VT, and the magnitude of the secondary-side current Io2 is set to be equal to or lower than the upper limit current IT.

[0091] In Fig. 10, the distribution determination unit 16f determines that the first storage battery module 30 has a remaining voltage Vb1, and makes a negative determination in step S23 in Fig. 8. The distribution determination unit 16f also determines that the second and third storage battery modules 60 and 90 have adjustable currents Ib2 and Ib3, and makes a positive determination in step S24 in Fig. 8. Therefore, the control unit 16c executes the redistribution process.

[0092] In the redistribution process, the control unit 16c controls the switching of the first power converter 40 so as to reduce the magnitude of the secondary-side current Io1 in the first storage battery module 30 by an adjustment amount ΔIo. In FIG. 10 , the control unit 16c sets the adjustment amount ΔIo of the secondary-side current Io1 to be greater than the amount by which the secondary-side current Io1 exceeds the upper limit current IT. Therefore, after the redistribution process is performed, the magnitude of the secondary-side current Io1 in the first storage battery module 30 is equal to or less than the upper limit current IT. Furthermore, the control unit 16c adjusts the secondary-side current Io1 in the first storage battery module 30 within a range in which the secondary-side terminal voltage Vo1 of the first storage battery module 30 does not exceed the upper limit voltage VT. In FIG. 10 , the increase ΔVo1 in the secondary-side terminal voltage Vo1 in the first storage battery module 30 is lower than the remaining voltage Vb1. Therefore, after the redistribution process is executed, the secondary side terminal voltage Vo1 of the first storage battery module 30 is set to be equal to or lower than the upper limit voltage VT.

[0093] Furthermore, in the redistribution process, the control unit 16c distributes the adjustment amount ΔIo of the secondary current Io1 in the first storage battery module 30 to the second storage battery module 60. In other words, the control unit 16c performs switching control of the second power converter 70 so as to increase the magnitude of the secondary current Io2 in the second storage battery module 60 by the adjustment amount ΔIo. In Fig. 10 , in the second storage battery module 60, the adjustment amount ΔIo of the secondary current Io2 is smaller than the adjustable current Ib2. Therefore, after the redistribution process is executed, the magnitude of the secondary current Io2 is set to be equal to or less than the upper limit current IT.

[0094] According to this embodiment, the redistribution process is performed in the overvoltage suppression control, and the redistribution process is also performed in the overcurrent suppression control, thereby suppressing the occurrence of overvoltage and overcurrent in each of the storage battery modules 30, 60, 90. As a result, it is possible to accurately suppress the occurrence of problems during the execution of switching control.

[0095] In Fig. 11 , the distribution determination unit 16f determines that there are no remaining voltages Vc2, Vc3 in the second and third storage battery modules 60, 90, and makes a positive determination in step S23 in Fig. 8. The distribution determination unit 16f also determines that there are no adjustable currents Ic2, Iac in the second and third storage battery modules 60, 90, and makes a negative determination in step S24 in Fig. 8. Therefore, the control unit 16c executes a reduction process.

[0096] In the reduction process, the control unit 16c controls the switching of the first power converter 40 so as to reduce the magnitude of the secondary current Io1 in the first storage battery module 30 by the excess amount ΔIo relative to the upper limit current IT. The control unit 16c also continues the current switching control of the second and third power converters 70, 100.

[0097] According to this embodiment, the total current of the secondary currents Io1, Io2, and Io3 in each of the storage battery modules 30, 60, and 90 is reduced. As a result, even when it is determined that the redistribution process cannot be performed, the magnitude of the secondary current in the current-excess module can be kept below the upper limit current IT. Therefore, a configuration suitable for preventing an overcurrent from flowing in each of the storage battery modules 30, 60, and 90 can be realized.

[0098] Modification of First Embodiment In the overvoltage suppression control, the control device 16 only needs to suppress application of an overvoltage to the secondary-side terminal pair of at least one of the power converters 40, 70, 100. In this case, the voltage acquisition unit 16a only needs to acquire the secondary-side terminal voltage Vo1, Vo2, Vo3 of at least one of the storage battery modules 30, 60, 90.

[0099] In the overcurrent suppression control, the control device 16 only needs to suppress an overcurrent from flowing through the secondary-side terminal pair of at least one of the power converters 40, 70, and 100. In this case, the current acquiring unit 16d only needs to acquire the secondary-side current Io1, Io2, and Io3 of at least one of the storage battery modules 30, 60, and 90.

[0100] Instead of performing the overvoltage suppression control and the overcurrent suppression control, the control device 16 may perform only the overvoltage suppression control out of the overvoltage suppression control and the overcurrent suppression control.

[0101] In the switching control, the control device 16 may control the secondary currents of one or two of the storage battery modules 30, 60, 90 and control the secondary terminal voltages Vo1, Vo2, Vo3 of the remaining storage battery modules, instead of controlling the secondary currents Io1, Io2, Io3 of the storage battery modules 30, 60, 90. For example, in the switching control, the control device 16 may control the secondary terminal voltage Vo1 of the first storage battery module 30 and control the secondary currents Io2, Io3 of the second and third storage battery modules 60, 90. In this case, the control device 16 may perform switching control of the first power converter 40 in the first storage battery module 30 so that the secondary terminal voltage Vo1 becomes the required voltage of the rotating electric machine 23.

[0102] An overcurrent in each of the storage battery modules 30, 60, 90 can also occur due to a sudden change in the demand for the power conversion system 10 from the rotating electric machine 23. Specifically, if the demand for power from the rotating electric machine 23 suddenly increases, the increased demand for power may be borne by the storage battery module that is subjected to voltage control among the storage battery modules 30, 60, 90, causing an increase in the secondary current. In this case, there is a concern that an overcurrent may flow in the storage battery module that is subjected to voltage control among the storage battery modules 30, 60, 90.

[0103] Even if one of the storage battery modules 30, 60, and 90 undergoing voltage control becomes an excess-current module, the redistribution process in step S25 of FIG. 8 can be performed to suppress the occurrence of an overcurrent in the excess-current module. In this case, the control unit 16c increases the magnitude of the secondary current in the storage battery modules 30, 60, and 90 other than the excess-current module and undergoing current control. This reduces the share of the required power in the excess-current module, thereby reducing the magnitude of the secondary current Io1 in the excess-current module. This suppresses the occurrence of an overcurrent in the storage battery modules 30, 60, and 90 undergoing voltage control. In addition to the overcurrent suppression control described above, overvoltage suppression control may also be performed. This suppresses the occurrence of overcurrent and overvoltage in the storage battery modules 30, 60, and 90.

[0104] In this embodiment, instead of performing both the overvoltage suppression control and the overcurrent suppression control, the control device 16 may perform only the overcurrent suppression control out of the overvoltage suppression control and the overcurrent suppression control.

[0105] In steps S12 and S13 of FIG. 3 and steps S22, S25, and S26 of FIG. 8 , the control unit 16c may control the currents Ibat1, Ibat2, and Ibat3 flowing through the storage batteries 31, 61, and 91, instead of controlling the secondary currents Io1, Io2, and Io3 of the storage battery modules 30, 60, and 90. Even in this case, overvoltage suppression control and overcurrent suppression control can be performed. In this embodiment, the currents Ibat1, Ibat2, and Ibat3 flowing through the storage batteries 31, 61, and 91 correspond to the “module current.”

[0106] The current acquiring unit 16d may acquire the currents Ibat1, Ibat2, Ibat3 flowing through the storage batteries 31, 61, 91, instead of acquiring the secondary currents Io1, Io2, Io3 of the storage battery modules 30, 60, 90. The detected currents of the battery monitoring devices 32, 62, 92 can be used as the currents Ibat1, Ibat2, Ibat3 flowing through the storage batteries 31, 61, 91.

[0107] The current determination unit 16e may determine whether or not there is an excess current module based on the acquired currents Ibat1, Ibat2, and Ibat3 flowing through the storage batteries 31, 61, and 91. In this case, the upper limit current IT may be determined according to the rated current of each storage battery 31, 61, and 91, and may be set to, for example, a value between 80% and 90% or between 90% and 100% of the rated current of each storage battery 31, 61, and 91.

[0108] The voltage acquiring unit 16a may acquire at least one or two of the detected voltages of the voltage sensors 45, 75, 105, the secondary-side terminal voltages Vo1, Vo2, Vo3 calculated based on the detected voltages of the battery monitoring devices 32, 62, 92, and the secondary-side terminal voltages Vo1, Vo2, Vo3 calculated based on the storage battery parameters of the battery monitoring devices 32, 62, 92. Note that when the secondary-side terminal voltages Vo1, Vo2, Vo3 calculated based on the detected values ​​of the battery monitoring devices 32, 62, 92 are acquired, the voltage sensors 45, 75, 105 do not need to be provided in the power converters 40, 70, 100.

[0109] During the overvoltage suppression control, the control unit 16c may change the secondary-side current of the storage battery modules 30, 60, 90 other than the overvoltage module by an amount greater than or less than the adjustment amount ΔIo. In this case, although the current flowing between the power conversion system 10 and the inverter 22 changes before and after the redistribution process, it is possible to suppress the application of an overvoltage to the secondary-side terminal pairs of the power converters 40, 70, 100.

[0110] Second Embodiment A second embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, the configuration of the storage battery modules is changed. Specifically, as shown in FIG. 12 , the power conversion system 10 includes a first storage battery module 130, a second storage battery module 160, and a third storage battery module 190. First, the configuration of the first storage battery module 130 will be described below.

[0111] The first storage battery module 130 includes a first power converter 140 and a first storage battery 131. A primary side positive terminal 141 of the first power converter 140 and the positive electrode side of the first storage battery 131 are electrically connected to the inverter 22 via the high potential side path 13. A primary side negative terminal 142 of the first power converter 140 is electrically connected to the negative electrode side of the first storage battery 131.

[0112] A secondary-side positive terminal 143 of the first power converter 140 is electrically connected to the negative electrode side of the first storage battery 131. A secondary-side negative terminal 144 of the first power converter 140 is electrically connected to the inverter 22 via the low-potential-side path 14. In other words, the secondary-side terminal pair of the first power converter 140 is electrically connected in series to the first storage battery 131 on the negative electrode side of the first storage battery 131.

[0113] The second storage battery module 160 includes a second power converter 170 and a second storage battery 161. The third storage battery module 190 includes a third power converter 1100 and a third storage battery 191. The configurations of the second and third storage battery modules 160 and 190 are similar to that of the first storage battery module 130, and therefore detailed description thereof will be omitted. Note that, for example, the power converters 140, 170, and 1100 are isolated DC-DC converters, as in the first embodiment. For example, the storage batteries 131, 161, and 191 are assembled batteries, as in the first embodiment.

[0114] As in the first embodiment, the control device 16 performs switching control of the power converters 140, 170, and 1100. Furthermore, as in the first embodiment, the control device 16 performs overvoltage suppression control and overcurrent suppression control while performing switching control.

[0115] As explained in the modified example of the first embodiment, this embodiment may be implemented by modifying each component.

[0116] Other Embodiments The above-described embodiments may be modified as follows.

[0117] The configuration of the storage battery modules may be changed as shown in Fig. 13. Specifically, the power conversion system 10 includes a first storage battery module 230, a second storage battery module 260, and a third storage battery module 290. The configuration of the first storage battery module 230 will be described below first.

[0118] The first storage battery module 230 includes a first power converter 240 and a first storage battery 231. A primary-side positive terminal 241 of the first power converter 240 is electrically connected to the positive electrode side of the first storage battery 231, and a primary-side negative terminal 242 of the first power converter 240 is electrically connected to the negative electrode side of the first storage battery 231. A secondary-side positive terminal 243 of the first power converter 240 is electrically connected to the inverter 22 via the high-potential side path 13, and a secondary-side negative terminal 244 of the first power converter 240 is electrically connected to the inverter 22 via the low-potential side path 14.

[0119] The second storage battery module 260 includes a second power converter 270 and a second storage battery 261. The third storage battery module 290 includes a third power converter 2100 and a third storage battery 291. The configurations of the second and third storage battery modules 260 and 290 are similar to that of the first storage battery module 230, and therefore detailed description thereof will be omitted. Note that, for example, the power converters 240, 270, and 2100 are isolated DC-DC converters, as in the first embodiment. The storage batteries 231, 261, and 291 are, for example, assembled batteries, as in the first embodiment.

[0120] As in the first embodiment, the control device 16 performs switching control of the power converters 240, 270, and 2100. Furthermore, as in the first embodiment, the control device 16 performs overvoltage suppression control and overcurrent suppression control while performing switching control.

[0121] The voltage applied to the secondary terminal pairs of each power converter 240, 270, 2100 is the voltage between each path 13 and 14. Therefore, unlike the first and second embodiments, the voltage of each storage battery 231, 261, 291 is less affected by the voltage applied to the secondary terminal pairs of each power converter 240, 270, 2100. Therefore, the possibility of an overvoltage being applied to the secondary terminal pairs of each power converter 240, 270, 2100 is lower than in the first and second embodiments. However, for example, if the load 21 suddenly changes from a driven state to a no-load state, a current may temporarily flow between each storage battery module 230, 260, 290. In this case, a storage battery module that receives current from another storage battery module among the storage battery modules 230, 260, 290 may temporarily receive an overvoltage or an overcurrent. Therefore, by having the control device 16 execute at least one of the overvoltage suppression control and the overcurrent suppression control, it is possible to appropriately realize the power conversion system 10 in which the storage battery modules 230, 260, 290 are electrically connected in parallel.

[0122] The control device is not limited to one that controls the power converters 40, 70, and 100 collectively, but may also control each power converter 40, 70, and 100 individually. Specifically, as shown in FIG. 14 , the power conversion system 10 may include first, second, and third control devices 17, 18, and 19. The first control device 17 is provided corresponding to the first storage battery module 30. The first control device 17 receives the detection values ​​of the first battery monitoring device 32 and the sensors 45 and 46. The second control device 18 is provided corresponding to the second storage battery module 60. The second control device 18 receives the detection values ​​of the second battery monitoring device 62 and the sensors 75 and 76. The third control device 19 is provided corresponding to the third storage battery module 90. The third control device 19 receives the detection values ​​of the third battery monitoring device 92 and the sensors 105 and 106.

[0123] Each of the control devices 17, 18, and 19 sets a current command value for the secondary current in the corresponding storage battery module, and performs switching control of the corresponding power converter based on the set current command value.

[0124] The control devices 17, 18, and 19 are capable of communicating with each other via wired or wireless communication means, and are able to mutually transmit and receive information such as input detection values ​​and current command values. Even in this case, the functions of the voltage acquisition unit 16 a, voltage determination unit 16 b, control unit 16 c, current acquisition unit 16 d, current determination unit 16 e, and distribution determination unit 16 f described in the first embodiment and the modified example of the first embodiment can be realized by each of the control devices 17, 18, and 19.

[0125] Note that each of the control devices 17, 18, and 19 is not limited to being provided outside the corresponding storage battery module 30, 60, and 90, but may be provided inside the corresponding storage battery module 30, 60, and 90. In the power conversion system 10 described in the second embodiment or Fig. 13, the control device may individually control each power converter, as in this embodiment.

[0126] The configuration of the power conversion system 10 may be changed as shown in Fig. 15. The power conversion system 10 may include first, second, and third high-side switches 301a, 302a, and 303a, and first, second, and third low-side switches 301b, 302b, and 303b. Each of the switches 301a, 302a, 303a, 301b, 302b, and 303b is a relay or a semiconductor switching element.

[0127] The first high potential side switch 301a is provided in the high potential side path 13 closer to the first storage battery module 30 than the connection point with the second storage battery module 60. The first low potential side switch 301b is provided in the low potential side path 14 closer to the first storage battery module 30 than the connection point with the second storage battery module 60, and on the lower potential side than the connection point with the primary side negative terminal 42 of the first power converter 40.

[0128] The second high-potential-side switch 302a is provided in a path that electrically connects the secondary-side positive terminal 73 of the second power converter 70 and the high-potential-side path 13. The second low-potential-side switch 302b is provided in a path that electrically connects the negative terminal of the second storage battery 61 and the low-potential-side path 14, on the lower-potential side of the connection point with the primary-side negative terminal 72 of the second power converter 70.

[0129] The third high-potential-side switch 303a is provided in a path electrically connecting the secondary-side positive terminal 103 of the third power converter 100 and the high-potential-side path 13. The third low-potential-side switch 303b is provided in a path electrically connecting the negative terminal of the third storage battery 91 and the low-potential-side path 14, on the lower potential side of the connection point with the primary-side negative terminal 102 of the third power converter 100.

[0130] The power conversion system 10 may include a first connection path 304 and a second connection path 305. A first end of the first connection path 304 is electrically connected between a connection point of the low potential side path 14 with the primary side negative terminal 42 of the first power converter 40 and the first low potential side switch 301b. A second end of the first connection path 304 is electrically connected between the secondary side positive terminal 73 of the second power converter 70 and the second high potential side switch 302a in a path electrically connecting the high potential side path 13 with the secondary side positive terminal 73 of the second power converter 70. Note that the configuration is not limited to that shown in FIG. 15 , and the first end of the first connection path 304 may be electrically connected between a connection point of the low potential side path 14 with the primary side negative terminal 42 of the first power converter 40 and the negative terminal of the first storage battery 31. In other words, the first end of the first connection path 304 may be electrically connected to the low potential side path 14 between the negative terminal of the first storage battery 31 and the first low potential side switch 301b.

[0131] A first end of the second connection path 305 is electrically connected between the second low-potential-side switch 302b and a connection point between the primary-side negative terminal 72 of the second power converter 70 and the second low-potential-side switch 302b in a path electrically connecting the negative terminal of the second storage battery 61 and the low-potential-side path 14. A second end of the second connection path 305 is electrically connected between the secondary-side positive terminal 103 of the third power converter 100 and the high-potential-side path 13 and the third high-potential-side switch 303a in a path electrically connecting the secondary-side positive terminal 103 of the third power converter 100 and the high-potential-side path 13. Note that the configuration is not limited to that shown in FIG. 15 , and the first end of the second connection path 305 may be electrically connected between the negative terminal of the second storage battery 61 and a connection point between the primary-side negative terminal 72 of the second power converter 70 and the negative terminal of the second storage battery 61 in a path electrically connecting the negative terminal of the second storage battery 61 and the low-potential-side path 14. In other words, the first end of the second connection path 305 needs only to be electrically connected between the negative terminal of the second storage battery 61 and the second low-potential side switch 302b, among the paths that electrically connect the negative terminal of the second storage battery 61 and the low-potential side path 14.

[0132] The power conversion system 10 includes a first connection switch 306 and a second connection switch 307. Each of the connection switches 306, 307 is a relay or a semiconductor switching element. The first connection switch 306 is provided on the first connection path 304. The second connection switch 307 is provided on the second connection path 305.

[0133] The control device 16 may switch the electrical connection relationship between the load 21 and the storage battery modules 30, 60, and 90 by controlling the switches 301a, 302a, 303a, 301b, 302b, 303b, 306, and 307. For example, the control device 16 may turn on the switches 301a, 302a, 303a, 301b, 302b, and 303b and turn off the connection switches 306 and 307. In this case, the storage battery modules 30, 60, and 90 are electrically connected in parallel to the load 21. Alternatively, for example, the control device 16 may turn on the switches 301a, 303b, 306, and 307 and turn off the switches 301b, 302a, 302b, and 303a. In this case, the storage battery modules 30, 60, and 90 are electrically connected in series to the load 21.

[0134] In this embodiment, the control device 16 can perform at least one of overvoltage suppression control and overcurrent suppression control, similarly to the above-described embodiments, when the storage battery modules 30, 60, 90 are electrically connected in parallel to the load 21. Note that, in the power conversion system 10 described in the second embodiment or FIG. 13, it is also possible to configure the electrical connection relationship between the load 21 and each storage battery module to be switchable, as described in this embodiment.

[0135] The control device 16 may perform at least one of overvoltage suppression control and overcurrent suppression control when the load 21 is not electrically connected to the power conversion system 10. For example, when there is no request to power or regenerate the rotating electric machine 23 and there is a request to control the amount of electricity stored in each of the storage batteries 31, 61, 91, there may be a request to exchange power only between the storage batteries 31, 61, 91. In this case, the control device 16 may perform at least one of overvoltage suppression control and overcurrent suppression control while the switching control is being executed.

[0136] When the operation of the power converter in a specific battery module among the battery modules 30, 60, and 90 is stopped, the control device 16 may perform only the overcurrent suppression control of the overvoltage suppression control and the overcurrent suppression control on the specific battery module. In this case, in step S10, the voltage acquisition unit 16a may not acquire the secondary terminal voltage of the specific battery module. Also, for example, in step S11, the voltage determination unit 16b may not determine whether the specific battery module is an overvoltage module.

[0137] The load electrically connected to the power conversion system 10 is not limited to the inverter 22 and the rotating electric machine 23, but may be a DC-DC converter, an external charger, an electric heater, or the like.

[0138] The switches constituting the power converter are not limited to N-channel MOSFETs, but may be IGBTs. In this case, the high-potential terminal of each switch is the collector, and the low-potential terminal is the emitter. A freewheeling diode is connected in antiparallel to each switch.

[0139] The power converter is not limited to the one described in FIG. 2, and it is also possible to use a non-insulated DC-DC converter such as a center-tap type isolated DC-DC converter, a resonant DC-DC converter, or a buck converter.

[0140] The power conversion system 10 may be a combination of at least two of the storage battery module described in the first embodiment, the storage battery module described in the second embodiment, and the storage battery module described in FIG. 13 .

[0141] The number of storage battery modules included in the power conversion system may be two, four, or more. In this case, each storage battery module may be configured similarly to the storage battery module described in the first embodiment, the storage battery module described in the second embodiment, or the storage battery module described in FIG. 13 .

[0142] The power storage unit included in each power storage module is not limited to a storage battery, but may be, for example, a large-capacity electric double layer capacitor, or both a storage battery and an electric double layer capacitor. The power storage unit may also be a fuel cell.

[0143] The power conversion system is not limited to being installed in a vehicle, but may also be installed in a moving object such as an aircraft or a ship. If the moving object is an aircraft, the rotating electric machine serves as the power source for the aircraft's flight, and if the moving object is a ship, the rotating electric machine serves as the power source for the ship's navigation. Furthermore, the power conversion system is not limited to being installed in a moving object, but can also be used as a stationary power source.

[0144] The control unit and the method described herein may be implemented by a special-purpose computer configured by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the control unit and the method described herein may be implemented by a special-purpose computer configured by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described herein may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to perform one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

[0145] The following describes characteristic configurations extracted from the above-described embodiments. [Configuration 1] A system including a plurality of power storage modules (30, 60, 90, 130, 160, 190, 230, 260, 290) each having a power storage unit (31, 61, 91, 131, 161, 191, 231, 261, 291) and a power converter (40, 70, 100, 140, 170, 1100, 240, 270, 2100) electrically connected to the power storage unit, wherein a power converter control device (16-19) applied to a power conversion system (10) in which the power storage modules are electrically connected in parallel includes: a voltage acquisition unit (16a) that acquires a terminal voltage of at least one of the power converters, and a control unit (16c) that performs switching control of the power converters so as to prevent the magnitude of the acquired terminal voltage from exceeding an upper limit voltage. [Configuration 2] In each of the power storage modules (31, 61, 91, 131, 161, 191), one of the pair of primary terminals of the power converter (40, 70, 100, 140, 170, 1100) is electrically connected to the positive electrode side of the power storage unit, and the other is electrically connected to the negative electrode side of the power storage unit; in each of the power storage modules, one of the pair of secondary terminals of the power converter is electrically connected to the positive electrode side or the negative electrode side of the power storage unit, and the other is electrically connected to a load (21); in each of the power storage modules, the one of the positive electrode side and the negative electrode side of the power storage unit that is not connected to the pair of secondary terminals of the power converter is electrically connected to the load; and the voltage acquisition unit acquires a secondary terminal voltage applied to at least one pair of secondary terminals of each of the power converters, 2. The control device for a power converter according to configuration 1, wherein the control unit performs the switching control so as to prevent the magnitude of the acquired secondary-side terminal voltage from exceeding the upper limit voltage.[Configuration 3] The control device for a power converter according to Configuration 2, further comprising: a voltage determination unit (16b) that determines whether any of the power storage modules is an over-voltage module whose acquired secondary-side terminal voltage exceeds the upper limit voltage; and when it is determined that any of the power storage modules is an over-voltage module, the control unit, in the switching control, changes a module current flowing through the over-voltage module so as to reduce the secondary-side terminal voltage of the over-voltage module, and changes a module current flowing through any of the power storage modules other than the over-voltage module in accordance with the change in the module current of the over-voltage module. [Configuration 4] The control device for a power converter according to Configuration 3, wherein, when it is determined that there is an over-voltage module, the control unit, in the switching control for discharging the power storage unit of the over-voltage module, reduces the magnitude of the module current in the over-voltage module, and increases the magnitude of the module current in power storage modules other than the over-voltage module that are discharging their power storage units, or reduces the magnitude of the module current in power storage modules that are charging their power storage units. [Configuration 5] The control device for a power converter according to Configuration 3 or 4, wherein, when it is determined that there is an over-voltage module, the control unit, in the switching control for charging the power storage unit of the over-voltage module, increases the magnitude of the module current in the over-voltage module, and reduces the magnitude of the module current in power storage modules other than the over-voltage module that are charging their power storage units, or increases the magnitude of the module current in power storage modules that are discharging their power storage units.[Configuration 6] The control device for a power converter according to any one of Configurations 3 to 5, comprising: a current acquisition unit (16d) that acquires the module current of at least one of the power storage modules; and a current determination unit (16e) that determines whether or not there is a current exceeding module among the power storage modules, the magnitude of the acquired module current exceeding an upper limit current, wherein if it is determined that there is a current exceeding module, the control unit performs a distribution process in the switching control to distribute an excess of the module current in the current exceeding module over the upper limit current to the power storage modules other than the current exceeding module. [Configuration 7] The control device for a power converter according to Configuration 6, further comprising: a distribution determination unit (16f) that determines whether or not to execute the distribution process if it is determined that there is a current exceeding module, wherein, in the switching control, the control unit performs the distribution process if it is determined that the distribution process should be executed, and reduces the total current of the module currents in the power storage modules if it is determined that the distribution process should not be executed. [Configuration 8] The control device for a power converter according to Configuration 6 or 7, wherein the control unit maintains the magnitude of the module current in each of the power storage modules when it is determined in the switching control that there is no excess-voltage module or no excess-current module. [Configuration 9] The control device for a power converter according to any one of Configurations 2 to 8, wherein the voltage acquisition unit acquires, as the secondary-side terminal voltage, a detected voltage of a voltage sensor (45, 75, 105) provided on a secondary-side terminal pair of at least one of the power converters. [Configuration 10] The control device for a power converter according to any one of Configurations 2 to 9, wherein the voltage acquisition unit acquires the secondary-side terminal voltage calculated based on the voltage of at least one of the power storage units. [Configuration 11] The control device for a power converter according to any one of Configurations 2 to 10, wherein the voltage acquisition unit acquires the secondary-side terminal voltage calculated based on a power storage unit parameter indicating a state of at least one of the power storage units.[Configuration 12] A system including a plurality of power storage modules (30, 60, 90, 130, 160, 190, 230, 260, 290) each having a power storage unit (31, 61, 91, 131, 161, 191, 231, 261, 291) and a power converter (40, 70, 100, 140, 170, 1100, 240, 270, 2100) electrically connected to the power storage unit, wherein a control device (16-19) for a power converter applied to a power conversion system (10) in which the power storage modules are electrically connected in parallel includes: a current acquisition unit (16d) that acquires a module current of at least one of the power storage modules; and a current determination unit (16e) that determines whether or not there is a current excess module among the power storage modules, the magnitude of the acquired module current exceeding an upper limit current, a control unit (16c) that controls switching of the power converters so as to distribute, when it is determined that there is an excess current module, the module current in the excess current module over the upper limit current to the power storage modules other than the excess current module among the power storage modules. [Configuration 13] A power conversion system comprising: a plurality of the power storage modules; and the control unit according to any one of Configurations 1 to 12.[Configuration 14] A system including a plurality of power storage modules (30, 60, 90, 130, 160, 190, 230, 260, 290) each having a power storage unit (31, 61, 91, 131, 161, 191, 231, 261, 291) and a power converter (40, 70, 100, 140, 170, 1100, 240, 270, 2100) electrically connected to the power storage unit, wherein a program applied to a power conversion system (10) in which the power storage modules are electrically connected in parallel, the program including: a current acquisition process for acquiring a module current of at least one of the power storage modules; and a current determination process for determining whether or not there is a current exceeding module among the power storage modules, the magnitude of the acquired module current exceeding an upper limit current, a control process for controlling switching of the power converters so that, when it is determined that there is an excess current module, the excess amount of the module current in the excess current module over the upper limit current is distributed to the power storage modules other than the excess current module among the power storage modules.[Configuration 15] A control method for a power converter applied to a power conversion system (10) including a plurality of power storage modules (30, 60, 90, 130, 160, 190, 230, 260, 290) each having a power storage unit (31, 61, 91, 131, 161, 191, 231, 261, 291) and a power converter (40, 70, 100, 140, 170, 1100, 240, 270, 2100) electrically connected to the power storage unit, wherein the power storage modules are electrically connected in parallel, the control method comprising: a current acquisition step of acquiring a module current of at least one of the power storage modules; and a current determination step of determining whether or not there is a current exceeding module among the power storage modules, the magnitude of the acquired module current exceeding an upper limit current. a control step of performing switching control of the power converters so that, when it is determined that there is an excess current module, the excess amount of the module current in the excess current module over the upper limit current is distributed to the power storage modules other than the excess current module among the power storage modules.

[0146] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A system including a plurality of power storage modules (30, 60, 90, 130, 160, 190, 230, 260, 290) each having a power storage unit (31, 61, 91, 131, 161, 191, 231, 261, 291) and a power converter (40, 70, 100, 140, 170, 1100, 240, 270, 2100) electrically connected to the power storage unit, wherein a power converter control device (16-19) is applied to a power conversion system (10) in which the power storage modules are electrically connected in parallel, the power converter control device comprising: a voltage acquisition unit (16a) that acquires a terminal voltage of at least one of the power converters; and a control unit (16c) that performs switching control of the power converters so as to prevent the magnitude of the acquired terminal voltage from exceeding an upper limit voltage.

2. In each of the energy storage modules (31, 61, 91, 131, 161, 191), one of the primary side terminal pair of the power converter (40, 70, 100, 140, 170, 1100) is electrically connected to the positive electrode side of the energy storage unit, and the other is electrically connected to the negative electrode side of the energy storage unit; in each of the energy storage modules, one of the secondary side terminal pair of the power converter is electrically connected to the positive electrode side or the negative electrode side of the energy storage unit, and the other is electrically connected to a load (21); in each of the energy storage modules, the one of the positive electrode side and the negative electrode side of the energy storage unit that is not connected to the secondary side terminal pair of the power converter is electrically connected to the load; and the voltage acquisition unit acquires a secondary side terminal voltage applied to at least one secondary side terminal pair of each of the power converters, The control device for a power converter according to claim 1 , wherein the control unit performs the switching control so as to prevent the magnitude of the acquired secondary side terminal voltage from exceeding the upper limit voltage.

3. The control device for a power converter as claimed in claim 2, further comprising a voltage determination unit (16b) that determines whether or not there is an over-voltage module among the power storage modules whose acquired secondary terminal voltage exceeds the upper limit voltage, and when it is determined that there is an over-voltage module, the control unit, in the switching control, changes the module current flowing to the over-voltage module so as to reduce the secondary terminal voltage in the over-voltage module, and changes the module current flowing to the power storage modules other than the over-voltage module among the power storage modules in accordance with the change in the module current in the over-voltage module.

4. The control device for a power converter according to claim 3, wherein, when it is determined that there is an over-voltage module, in the switching control for discharging the storage unit of the over-voltage module, the control unit reduces the magnitude of the module current in the over-voltage module, increases the magnitude of the module current in a storage unit module other than the over-voltage module among the storage units and in which the storage unit is being discharged, or reduces the magnitude of the module current in a storage unit module in which the storage unit is being charged.

5. The control device for a power converter according to claim 3, wherein, when it is determined that there is an over-voltage module, in the switching control for charging the storage unit of the over-voltage module, the control unit increases the magnitude of the module current of the over-voltage module, reduces the magnitude of the module current in a storage unit module other than the over-voltage module among the storage units and in which the storage unit is being charged, or increases the magnitude of the module current in a storage unit module in which the storage unit is being discharged.

6. A control device for a power converter as described in claim 3, comprising: a current acquisition unit (16d) that acquires the module current of at least one of the power storage modules; and a current determination unit (16e) that determines whether or not there is a current excess module among the power storage modules in which the acquired module current exceeds an upper limit current, wherein when it is determined that there is a current excess module, in the switching control, the control unit performs a distribution process of distributing the excess of the module current in the current excess module over the upper limit current to the power storage modules other than the current excess module among the power storage modules.

7. The control device for a power converter as described in claim 6, further comprising a distribution determination unit (16f) that determines whether or not to execute the distribution process when it is determined that there is an excess current module, and wherein, in the switching control, the control unit executes the distribution process when it is determined that the distribution process should be executed, and reduces the total current of the module currents in each of the storage modules when it is determined that the distribution process should not be executed.

8. The control device for a power converter as described in claim 6, wherein the control unit maintains the magnitude of the module current in each of the storage modules when it is determined in the switching control that there is no over-voltage module or over-current module.

9. A control device for a power converter as described in claim 2, wherein the voltage acquisition unit acquires, as the secondary terminal voltage, a detection voltage of a voltage sensor (45, 75, 105) provided on at least one secondary terminal pair of each of the power converters.

10. The control device for a power converter according to claim 2, wherein the voltage acquisition unit acquires the secondary terminal voltage calculated based on the voltage of at least one of the power storage units.

11. The control device for a power converter according to claim 2, wherein the voltage acquisition unit acquires the secondary terminal voltage calculated based on a storage unit parameter indicating a state of at least one of the storage units.

12. A system including a plurality of power storage modules (30, 60, 90, 130, 160, 190, 230, 260, 290) each having a power storage unit (31, 61, 91, 131, 161, 191, 231, 261, 291) and a power converter (40, 70, 100, 140, 170, 1100, 240, 270, 2100) electrically connected to the power storage unit, wherein a control device (16-19) for a power converter applied to a power conversion system (10) in which the power storage modules are electrically connected in parallel, the control device (16-19) includes: a current acquisition unit (16d) that acquires a module current of at least one of the power storage modules; and a current determination unit (16e) that determines whether or not there is a current excess module among the power storage modules, the magnitude of the acquired module current exceeding an upper limit current, a control unit (16c) that performs switching control of each of the power converters so that, when it is determined that there is a current-excess module, an excess of the module current in the current-excess module over the upper limit current is distributed to one of the power storage modules other than the current-excess module.

13. A power conversion system comprising: a plurality of the power storage modules; and the control device according to any one of claims 1 to 12.

14. A program applied to a power conversion system (10) including a plurality of power storage modules (30, 60, 90, 130, 160, 190, 230, 260, 290) having a power storage unit (31, 61, 91, 131, 161, 191, 231, 261, 291) and a power converter (40, 70, 100, 140, 170, 1100, 240, 270, 2100) electrically connected to the power storage unit, the program causing a computer (16-19) to execute a voltage acquisition process for acquiring a terminal voltage of at least one of the power converters, and a control process for performing switching control of the power converters so as to prevent the magnitude of the acquired terminal voltage from exceeding an upper limit voltage.

15. A method for controlling a power converter applied to a power conversion system (10) including a plurality of power storage modules (30, 60, 90, 130, 160, 190, 230, 260, 290) having a power storage unit (31, 61, 91, 131, 161, 191, 231, 261, 291) and a power converter (40, 70, 100, 140, 170, 1100, 240, 270, 2100) electrically connected to the power storage unit, the power converter control method including: a voltage acquisition step of acquiring a terminal voltage of at least one of the power converters; and a control step of performing switching control of the power converters so as to prevent the magnitude of the acquired terminal voltage from exceeding an upper limit voltage.

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