Power conversion device, control program for power conversion device, and control method for power conversion device

Abstract

This power conversion device comprises: positive electrode paths (11, 63a, 64a, 65b, 65c, 263b, 264b) that connect the positive electrode sides of a plurality of electricity storage units (31, 41, 51); negative electrode paths (12, 63b, 63c, 64b, 64c, 65a, 265b) that connect the negative electrode sides of the plurality of electricity storage units; parallel connection switches (62a, 62b, 62c, 62d, 262b, 362a, 362b, 362c, 362d); series connection paths (60, 60a, 60b); series connection switches (61, 61a, 61b); and power converters (32, 42, 52, 242). Each power converter is provided by corresponding to at least one specific electricity storage unit (31, 41, 51) among the plurality of electricity storage units and has a primary-side terminal pair and a secondary-side terminal pair. Each power converter is provided such that, in a state in which the plurality of electricity storage units is connected in series, the secondary-side terminal pair and the plurality of electricity storage units are electrically disconnected.

Description

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

[0001] This application is based on Japanese Application No. 2024-043126 filed on March 19, 2024, the contents of which are incorporated herein by reference.

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

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

[0004] Japanese Patent Application Laid-Open No. 2022-23722

[0005] In a system including a plurality of power storage units, there is a concern that power loss may increase due to conduction loss occurring in a power conversion device.

[0006] An object of the present disclosure is to provide a power conversion device, a control program for the power conversion device, and a control method for the power conversion device that can reduce power loss in a system.

[0007] The present disclosure relates to a power conversion device applied to a system including a plurality of power storage units, the power conversion device comprising: a positive electrode path connecting positive electrode sides of the plurality of power storage units; a negative electrode path connecting negative electrode sides of the plurality of power storage units; a parallel connection switch provided for each of the plurality of power storage units in at least one of the positive electrode path and the negative electrode path; a series connection path connecting the plurality of power storage units in series; a series connection switch provided in the series connection path; and a power converter provided corresponding to at least one specific power storage unit among the plurality of power storage units, the power converter having a primary side terminal pair and a secondary side terminal pair, the primary side terminal pair of the power converter being connected in parallel to the specific power storage unit, and the secondary side terminal pair of the power converter being connected in series to the specific power storage unit, and when the series connection switch is turned off and the parallel connection switch is turned on, the plurality of power storage units are connected in parallel via the positive electrode path, the negative electrode path and the power converter, When the series connection switch is turned on and the parallel connection switch is turned off, the plurality of power storage units are connected in series via the series connection path, and the power converter is configured such that when the plurality of power storage units are connected in series, the secondary side terminal pair and each of the power storage units are electrically isolated.

[0008] In the above-described system, when the series connection switch is turned off and the parallel connection switch is turned on, the plurality of power storage units are connected in parallel via the positive electrode path, the negative electrode path, and the power converter. In this case, the power converter is used to control the voltages of the secondary-side terminal pairs connected in series to the power storage units.

[0009] On the other hand, when the series connection switch is turned on and the parallel connection switch is turned off, the plurality of power storage units are connected in series via the series connection path, thereby enabling the voltage of each series-connected body of power storage units to be output.

[0010] Here, when multiple power storage units are connected in series, the operation of the power converter may be unnecessary. However, unlike the present disclosure, in a configuration in which the current path of the series-connected body of each power storage unit includes a path connecting the secondary terminal pairs of the power converter and the power storage units in series, unnecessary current may flow in the power converter. This may cause conduction loss in the power converter, which may increase power loss in the system.

[0011] Therefore, in the present disclosure, a power converter is provided corresponding to at least one specific power storage unit among the multiple power storage units. A secondary-side terminal pair of the power converter is connected in series to the specific power storage unit. The power converter is provided so that, when the multiple power storage units are connected in series, the secondary-side terminal pair is electrically isolated from each power storage unit. This makes it possible to prevent current flowing through the series-connected units of the power storage units from flowing to the power converter, thereby suppressing conduction loss in the power converter. This makes it possible to reduce power loss in the system.

[0012] 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 the first embodiment; Figure 2 is a diagram showing an example of a power converter; Figure 3 is a diagram showing the operation of a comparative example; Figure 4 is a diagram showing the path of a current flowing in the power conversion system; Figure 5 is a diagram showing the path of a current flowing in the power conversion system; Figure 6 is a diagram showing an example of operation when a low-voltage charger is electrically connected to the power conversion system; Figure 7 is a flowchart showing the control processing procedure performed by the control device; Figure 8 is a configuration diagram of a power conversion system according to a modified example of the first embodiment; Figure 9 is a configuration diagram of a power conversion system according to a modified example of the first embodiment; Figure 10 is a configuration diagram of a power conversion system according to a modified example of the first embodiment; Figure 11 is a configuration diagram of a power conversion system according to a modified example of the first embodiment;

[0013] 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.

[0014] A first embodiment of a power conversion device according to the present disclosure will now be described with reference to the drawings. In this embodiment, the power conversion device constitutes a power conversion system mounted on an electrically powered vehicle such as an electric vehicle or a hybrid vehicle.

[0015] FIG. 1 shows a configuration diagram of a power conversion system 10. The power conversion system 10 includes a plurality of storage battery modules, and in this embodiment, includes two modules: a first storage battery module 30 and a second storage battery module 40. Each storage battery module 30, 40 includes a storage battery 31, 41 (corresponding to a "power storage unit"). Each storage battery 31, 41 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.

[0016] A high-voltage load 20 powered by the storage batteries 31, 41 is electrically connected to each storage battery module 30, 40. In this embodiment, the high-voltage load 20 includes an inverter 21 and a rotating electric machine 22. The inverter 21 includes three phases of series-connected upper-arm switches SH and lower-arm switches SL. Each switch SH, SL is a voltage-controlled semiconductor switching element, more specifically, an IGBT. In this case, the high-potential terminal of each switch SH, SL is the collector, and the low-potential terminal is the emitter. Freewheel diodes DH, DL are connected in antiparallel to each switch SH, SL.

[0017] The positive electrode side of each battery module 30, 40 is electrically connected to the collector of the corresponding upper arm switch SH via a high potential side path 11 such as a bus bar. The negative electrode side of each battery module 30, 40 is electrically connected to the emitter of the corresponding lower arm switch SL via a low potential side path 12 such as a bus bar.

[0018] The rotating electric machine 22 has armature windings 23 electrically connected to the upper arm switches SH and the lower arm switches SL for each phase. The inverter 21 controls the current flowing through the windings 23 for each phase. The rotating electric machine 22 is an on-vehicle main motor, and a rotor of the rotating electric machine 22 is capable of transmitting power to the drive wheels of the vehicle. The rotating electric machine 22 is, for example, a permanent magnet synchronous machine.

[0019] Each storage battery module 30, 40 includes a power converter 32, 42 and a drive circuit 33, 43. Hereinafter, the storage battery 31, the power converter 32, and the drive circuit 33 of the first storage battery module 30 may be referred to as the "first storage battery 31," the "first power converter 32," and the "first drive circuit 33," and the storage battery 41, the power converter 42, and the drive circuit 43 of the second storage battery module 40 may be referred to as the "second storage battery 41," the "second power converter 42," and the "second drive circuit 43."

[0020] The first power converter 32 includes a primary terminal pair consisting of a primary positive terminal 32a and a primary negative terminal 32b, and a secondary terminal pair consisting of a secondary positive terminal 32c and a secondary negative terminal 32d. The second power converter 42 includes a primary terminal pair consisting of a primary positive terminal 42a and a primary negative terminal 42b, and a secondary terminal pair consisting of a secondary positive terminal 42c and a secondary negative terminal 42d.

[0021] The primary terminal pair of each power converter 32, 42 is electrically connected in parallel to the corresponding storage battery 31, 41. Specifically, the primary positive terminal 32a of the first power converter 32 is electrically connected to the positive electrode side of the first storage battery 31. The primary negative terminal 32b of the first power converter 32 is electrically connected to the negative electrode side of the first storage battery 31. The primary positive terminal 42a of the second power converter 42 is electrically connected to the positive electrode side of the second storage battery 41. The primary negative terminal 42b of the second power converter 42 is electrically connected to the negative electrode side of the second storage battery 41. In this case, the voltage of the corresponding storage battery 31, 41 is applied to the primary terminal pair of each power converter 32, 42.

[0022] The secondary terminal pairs of each power converter 32, 42 are connected in series to the corresponding storage batteries 31, 41. The connection relationship between the secondary terminal pairs of each power converter 32, 42 and the corresponding storage batteries 31, 42 will be described later. In this embodiment, each storage battery 31, 41 corresponds to a "specific power storage unit."

[0023] In each storage battery module 30, 40, the secondary-side terminal voltages Vo1, Vo2 applied to the secondary-side terminal pair of the power converter 32, 42 are the differential voltages between the voltages across each path 11, 12 and the voltages Vb1, Vb2 of the corresponding storage batteries 31, 41. In this case, a voltage lower than the rated voltage (e.g., 400 V) of the corresponding storage batteries 31, 41 is applied to the secondary-side terminal pair of each power converter 32, 42. Therefore, the rated secondary voltage on the secondary side of each power converter 32, 42 can be set lower than the rated voltage of the corresponding storage battery 31, 41, thereby enabling the miniaturization of each power converter 32, 42.

[0024] FIG. 2 shows an example of a first power converter 32. The first power converter 32 is a center-tap isolated DC-DC converter. The first power converter 32 includes primary-side switches S1 to S4, secondary-side switches Q1a and Q2a, a primary-side capacitor 34, a secondary-side capacitor 35, a transformer 36, and a reactor 37. In this embodiment, voltage-controlled semiconductor switching elements, more specifically, N-channel MOSFETs, are used as the primary-side switches S1 to S4 and the secondary-side switches Q1a and Q2a. In this case, the high-potential terminal of each of the switches S1 to S4, Q1a, and Q2a is the drain, and the low-potential terminal is the source. Each of the switches S1 to S4, Q1a, and Q2a also has a body diode.

[0025] The first power converter 32 includes primary-side switches, namely, a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4. The drain of the first switch S1 and the drain of the third switch S3 are electrically connected to the primary-side positive terminal 32a and a first end of the primary-side capacitor 34. The source of the first switch S1 is connected to the drain of the second switch S2. The source of the third switch S3 is connected to the drain of the fourth switch S4. The source of the second switch S2 and the source of the fourth switch S4 are electrically connected to the primary-side negative terminal 32b and a second end of the primary-side capacitor 34.

[0026] The transformer 36 includes a primary winding 36a and a secondary winding 36b, which are wound around a common core. As a result, the primary winding 36a and the secondary winding 36b are magnetically coupled by the common core. When the potential at the first end of the primary winding 36a becomes higher relative to the second end, an induced voltage is generated such that the potential at the first end of the secondary winding 36b becomes higher than the second end. On the other hand, when the potential at the second end of the primary winding 36a becomes higher relative to the first end, an induced voltage is generated such that the potential at the second end of the secondary winding 36b becomes higher than the first end.

[0027] A first end of the primary winding 36a is electrically connected to the source of the first switch S1 and the drain of the second switch S2, and a second end of the primary winding 36a is electrically connected to the source of the third switch S3 and the drain of the fourth switch S4.

[0028] The first power converter 32 includes two secondary switches Q1a and Q2a. The source of the secondary switch Q1a is electrically connected to a first end of the secondary winding 36b, and the source of the other secondary switch Q2a is electrically connected to a second end of the secondary winding 36b. The drains of the secondary switches Q1a and Q2a are electrically connected to a first end of a reactor 37. The second end of the reactor 37 is electrically connected to the secondary positive terminal 32c and the first end of the secondary capacitor 35. The center tap of the secondary winding 36b is electrically connected to the secondary negative terminal 32d and the second end of the secondary capacitor 35.

[0029] The second power converter 42 is a center-tapped isolated DC-DC converter, and includes a primary-side switch, a secondary-side switch, a primary-side capacitor, a secondary-side capacitor, a transformer, and a reactor, similar to the first power converter 32. In this embodiment, the first power converter 32 and the second power converter 42 are basically configured the same, and therefore a detailed description of the second power converter 42 will be omitted.

[0030] Returning to the explanation of Fig. 1, a drive command is input to each drive circuit 33, 43 from the control device 16 provided in the power conversion system 10. The drive command consists of an on command and an off command for the primary-side switches and secondary-side switches of the power converters 32, 42. Based on the input drive command, each drive circuit 33, 43 turns on and off the primary-side switches and secondary-side switches of the corresponding power converter 32, 42.

[0031] The power conversion system 10 includes a series connection path 60 and a series connection switch 61. The series connection path 60 is a path that connects the first storage battery 31 and the second storage battery 41 in series. In this embodiment, a first end of the series connection path 60 is electrically connected to the positive electrode side of the first storage battery 31. A second end of the series connection path 60 is electrically connected to the negative electrode side of the second storage battery 41. In this case, in the series connection of the storage batteries 31, 41, the first storage battery 31 is on the low potential side and corresponds to the "low potential storage unit." In addition, in the series connection of the storage batteries 31, 41, the second storage battery 41 is on the high potential side and corresponds to the "high potential storage unit."

[0032] The series connection switch 61 is provided in the series connection path 60. The series connection switch 61 is a mechanical relay or a semiconductor switching element. When the series connection switch 61 is turned off, it blocks bidirectional current flow, and when turned on, it allows bidirectional current flow. The series connection switch 61 is controlled by the control device 16 included in the power conversion system 10.

[0033] The power conversion system 10 includes a parallel connection switch for each of the first and second storage battery modules 30, 40. Specifically, the power conversion system 10 includes a first parallel connection switch 62a and a second parallel connection switch 62b. Each of the parallel connection switches 62a, 62b is a mechanical relay or a semiconductor switching element. When turned off, each of the parallel connection switches 62a, 62b blocks bidirectional current flow, and when turned on, each of the parallel connection switches 62a, 62b allows bidirectional current flow. Each of the parallel connection switches 62a, 62b is controlled by the control device 16.

[0034] The first parallel connection switch 62a is provided corresponding to the first storage battery module 30, and is provided on a path electrically connecting the first storage battery 31 to each of the paths 11 and 12. The second parallel connection switch 62b is provided corresponding to the second storage battery module 40, and is provided on a path electrically connecting the second storage battery 41 to each of the paths 11 and 12.

[0035] The power conversion system 10 includes a high-potential-side connection switch 70H and a low-potential-side connection switch 70L. Each of the switches 70H and 70L is a mechanical relay or a semiconductor switching element. When turned off, each of the switches 70H and 70L blocks bidirectional current flow, and when turned on, each of the switches 70H and 70L allows bidirectional current flow. Each of the switches 70H and 70L is controlled by the control device 16.

[0036] Each of the connection switches 70H, 70L is a switch for electrically connecting or disconnecting the external charger and the power conversion system 10. Each of the connection switches 70H, 70L is provided in a path electrically connecting the external charger and the power conversion system 10. For example, in FIG. 1 , the high-potential-side connection switch 70H is provided in the high-potential-side path 11 on the side opposite the connection point with the positive electrode of the first storage battery module 30 from the connection point with the positive electrode of the second storage battery module 40. Furthermore, the low-potential-side connection switch 70L is provided in the low-potential-side path 12 on the side opposite the connection point with the negative electrode of the second storage battery module 40 from the connection point with the negative electrode of the first storage battery module 30. In this case, the external charger is electrically connected to each of the storage battery modules 30, 40 via each of the paths 11, 12 and the connection switches 70H, 70L.

[0037] The power conversion system 10 includes a power supply voltage sensor 80, a power supply current sensor 81, and module current sensors 82a and 82b. The power supply voltage sensor 80 detects the power supply voltage, which is the voltage between the paths 11 and 12. The power supply current sensor 81 detects the power supply current, which is the current flowing on the DC side of the inverter 21. In this embodiment, the power supply current sensor 81 is provided in the low potential side path 12, closer to the connection point with the emitter of the lower arm switch SL of each phase than to the connection point with the negative electrode side of the first storage battery module 30.

[0038] The module current sensors 82a, 82b are provided corresponding to the storage battery modules 30, 40, and detect module current, which is current flowing through each storage battery module 30, 40. In this embodiment, the module current sensor 82a of the first storage battery module 30 is provided on the negative electrode side of the first storage battery 31 in the path electrically connecting the first storage battery 31 to each of the paths 11, 12. The module current sensor 82b of the second storage battery module 40 is provided on the negative electrode side of the second storage battery 41 in the path electrically connecting the second storage battery 41 to each of the paths 11, 12. The detected values ​​of the sensors 80, 81, 82a, 82b are input to the control device 16.

[0039] The power conversion system 10 includes primary-side voltage sensors 83a and 83b, primary-side current sensors 84a and 84b, secondary-side voltage sensors 85a and 85b, and secondary-side current sensors 86a and 86b. The sensors 83a, 84a, 85a, and 86a are provided in the first power converter 32. The sensors 83b, 84b, 85b, and 86b are provided in the second power converter 42. The detected values ​​of the sensors 83a to 86a and 83b to 86b are input to the control device 16.

[0040] 2 , the primary-side voltage sensor 83a detects the voltage of the primary-side capacitor 34. The primary-side current sensor 84a detects the current flowing on the primary side of the first power converter 32. In this embodiment, the primary-side current sensor 84a detects the current flowing between the drains of the first and third switches S1, S3 and the first end of the primary-side capacitor 34.

[0041] The secondary-side voltage sensor 85a detects the voltage of the secondary-side capacitor 35. The secondary-side current sensor 86a detects the current flowing on the secondary side of the first power converter 32. In the present embodiment, the secondary-side current sensor 86a detects the current flowing between the drain of each of the secondary-side switches Q1a, Q2a and the first end of the reactor 37.

[0042] The control device 16 is an electronic control unit (ECU) that performs various controls and includes a processor and a storage unit as hardware. Each of the on-board devices shown in FIG. 1 , such as the power converters 32 and 42, the switches 61, 62a, 62b, 70H, and 70L, and the inverter 21, can be controlled by an ECU corresponding to the on-board device. However, for convenience, multiple ECUs are shown as a single control device 16 in FIG. 1 .

[0043] The memory unit of the control device 16 includes a memory and a storage as hardware. The memory is a storage device for storing data used in the processing of the control device 16. The memory provides the processor of the control device 16 with a working area for temporary use when the processor performs processing, for example. The memory includes, for example, a ROM or a RAM. The storage is a storage device for storing various programs and data to be read and executed by the processor, and is a non-transitory tangible storage medium. The storage includes, for example, an HDD or a flash memory. The storage stores program information and the like for processing, such as those shown in Figures 7 and 13, which will be described later.

[0044] For example, program information stored in a non-transient physical recording medium is installed in the storage unit of the control device 16. The recording medium is, for example, a USB memory, a CD-ROM, or a DVD. Also, for example, program information transmitted via a communication network, such as over the air (OTA), is installed in the storage unit.

[0045] The control device 16 controls the switches 61, 62a, and 62b to switch the electrical connection relationship of the storage battery modules 30 and 40. Specifically, when connecting the storage battery modules 30 and 40 in parallel, the control device 16 turns off the series connection switch 61 and turns on the parallel connection switches 62a and 62b. This enables the power conversion system 10 to output voltages from the storage batteries 31 and 41. In this case, the control device 16 controls the switching of the power converters 32 and 42 to adjust the output voltages of the storage battery modules 30 and 40. Note that the control device 16 may use at least one of the detection values ​​of the sensors 80, 81, 82a, 82b, 83a, 83b, 84a, 84b, 85a, 85b, 86a, and 86b to control the switching of the power converters 32 and 42.

[0046] On the other hand, when the storage battery modules 30, 40 are connected in series, the control device 16 turns on the series connection switch 61 and turns off the parallel connection switches 62 a, 62 b, thereby enabling the power conversion system 10 to output the voltage of the series-connected body of the storage batteries 31, 41.

[0047] When the storage battery modules 30, 40 are connected in series, the operation of the power converters 32, 42 may be unnecessary. However, unnecessary current may flow through the power converters 32, 42, causing conduction loss in the power converters 32, 42. In this case, there is a concern that power loss may increase in the power conversion system 10.

[0048] Specifically, the description will be given with reference to the configuration of a comparative example that is different from this embodiment.

[0049] 3 , the power conversion system 10 includes a first storage battery module 130 and a second storage battery module 140. The first parallel connection switch 162a is provided on a path electrically connecting the first storage battery 31 to the paths 11 and 12 in the first storage battery module 130, the path being on a higher potential side than the secondary-side positive terminal 132c of the first power converter 132. A first end of the series connection path 160 is electrically connected between the secondary-side positive terminal 132c and the first parallel connection switch 162a on the path electrically connecting the first storage battery 31 to the paths 11 and 12.

[0050] The second parallel connection switch 162b is provided on the lower potential side of the negative terminal of the second storage battery 41 in the path electrically connecting the second storage battery 41 to each of the paths 11 and 12 in the second storage battery module 140. The second end of the series connection path 160 is electrically connected between the second storage battery 41 and the second parallel connection switch 162b in the path electrically connecting the second storage battery 41 to each of the paths 11 and 12.

[0051] In the comparative example described above, the first storage battery module 130 and the second storage battery module 140 are connected in series by turning on the series connection switch 61 and turning off the first parallel connection switch 162a and the second parallel connection switch 162b.

[0052] However, in the comparative example, the positive terminal of the first storage battery 31 and the first end of the series connection path 160 are electrically connected via the secondary-side terminal pair of the first power converter 132. In this case, components on the secondary side of the first power converter 132 are included in the current path of the series connection of the storage batteries 31, 41.

[0053] In the comparative example, the secondary terminal pair of the second power converter 142 is electrically connected in series to the second storage battery 41 on the positive electrode side of the second storage battery 41. In this case, components on the secondary side of the second power converter 142 are included in the current path of the series-connected body of the storage batteries 31, 41.

[0054] The components on the secondary side of each power converter 132, 142 include components with resistance components, such as switches, diodes, reactors, and transformer windings. Therefore, in the configuration of the comparative example described above, conduction loss may occur in each power converter 132, 142 due to current flowing through the components on the secondary side of each power converter 132, 142. In this case, there is a concern that power loss may increase in the power conversion system 10.

[0055] Therefore, in this embodiment, the power converters 32, 42 are provided in the power conversion system 10 so that, when the storage battery modules 30, 40 are connected in series, the secondary terminal pairs of the power converters 32, 42 are electrically disconnected from the storage batteries 31, 41. The following describes in detail the characteristic configuration for suppressing conduction loss in the power converters 32, 42.

[0056] 1 , in this embodiment, the secondary side terminal pair of the first power converter 32 is electrically connected in series to the first storage battery 31 on the positive electrode side of the first storage battery 31. The secondary side terminal pair of the second power converter 42 is electrically connected in series to the second storage battery 41 on the negative electrode side of the second storage battery 41.

[0057] Specifically, each of the storage battery modules 30, 40 includes a first module path 63a, 63b, a second module path 64a, 64b, and a third module path 65a, 65b.

[0058] In the first storage battery module 30, a first end of the first module path 63a is electrically connected to the secondary-side positive terminal 32c of the first power converter 32, and a second end of the first module path 63a is electrically connected to the high-potential-side path 11. A first end of the second module path 64a is electrically connected to the secondary-side negative terminal 32d of the first power converter 32, and a first end of the second module path 64a is electrically connected to the positive terminal of the first storage battery 31. A first end of the third module path 65a is electrically connected to the negative terminal of the first storage battery 31, and a second end of the third module path 65a is electrically connected to the low-potential-side path 12.

[0059] A first end of the series connection path 60 is electrically connected to the second module path 64a. The first parallel connection switch 62a is provided on the second module path 64a on a higher potential side than the connection point with the series connection path 60. In this case, when the first parallel connection switch 62a is turned off, the first storage battery 31 and the series connection path 60 are electrically disconnected from the secondary-side terminal pair of the first power converter 32.

[0060] In the second storage battery module 40, a first end of the first module path 63b is electrically connected to the secondary-side positive terminal 42c of the second power converter 42, and a second end of the first module path 63b is electrically connected to the negative terminal of the second storage battery 41. A first end of the second module path 64b is electrically connected to the secondary-side negative terminal 42d of the second power converter 42, and a second end of the second module path 64b is electrically connected to the low-potential-side path 12. A first end of the third module path 65b is electrically connected to the high-potential-side path 11, and a second end of the third module path 65b is electrically connected to the positive terminal of the second storage battery 41.

[0061] A second end of the series connection path 60 is electrically connected to the first module path 63b. The second parallel connection switch 62b is provided on the first module path 63b on a side of the first module path 63b that is at a lower potential than the connection point with the series connection path 60. In this case, when the second parallel connection switch 62b is turned off, the series connection path 60 and the second storage battery 41 are electrically disconnected from the secondary-side terminal pair of the second power converter 42.

[0062] In this embodiment, the high-potential side path 11, the first and second module paths 63a and 64a of the first storage battery module 30, and the third module path 65b of the second storage battery module 40 correspond to the "positive electrode path." The low-potential side path 12, the third module path 65a of the first storage battery module 30, and the first and second module paths 63b and 64b of the second storage battery module 40 correspond to the "negative electrode path." The paths 11, 12, 63a to 65a, and 63b to 65b, the power converters 32 and 42, the series connection path 60, the series connection switch 61, and the parallel connection switches 62a and 62b correspond to the "power conversion device."

[0063] 4 and 5 show paths of current flowing through the power conversion system 10 when the storage battery modules 30, 40 are connected in series. Fig. 4 shows an example of paths of current flowing through the power conversion system 10 when the storage batteries 31, 41 are discharged. Fig. 5 shows an example of paths of current flowing through the power conversion system 10 when the storage batteries 31, 41 are charged.

[0064] In Figure 4, when each storage battery module 30, 40 is connected in series, a situation is assumed in which each storage battery 31, 41 is discharged and current is passed from the power conversion system 10 to the rotating electric machine 22 to power the rotating electric machine 22.

[0065] In FIG. 5 , when the storage battery modules 30, 40 are connected in series, a situation in which the storage batteries 31, 41 are charged by an external charger electrically connected to the power conversion system 10 is assumed. The external charger is, for example, a stationary charger provided outside the vehicle. In this example, a high-voltage charger 90, which is an external charger, is electrically connected to the storage battery modules 30, 40 via the connection switches 70H, 70L. The charging voltage of the high-voltage charger 90 is higher than the sum of the voltages Vb1, Vb2 (specifically, rated voltages) of the storage batteries 31, 41. When the external charger is electrically connected to the power conversion system 10, the control device 16 turns on the connection switches 70H, 70L to charge the storage batteries 31, 41.

[0066] When the storage battery modules 30, 40 are connected in series, the high-potential side path 11, the low-potential side path 12, the series connection path 60, and the third module paths 65 a, 65 b of each storage battery module 30, 40 form a current path for the series-connected body of each storage battery 31, 41. A current flows through the current path for the series-connected body of each storage battery 31, 41 when each storage battery 31, 41 is discharged or charged.

[0067] In this embodiment, turning off the parallel connection switches 62a, 62b electrically disconnects the secondary terminal pairs of the power converters 32, 42 from the storage batteries 31, 41. This prevents the current flowing through the current paths of the series-connected bodies of the storage batteries 31, 41 from flowing to the power converters 32, 42. This prevents conduction loss in the power converters 32, 42. As a result, power loss in the power conversion system 10 can be reduced.

[0068] Next, the control performed by the control device 16 will be described.

[0069] Returning to the explanation of FIG. 1 , the control device 16 includes a determination unit 16a, a connection control unit 16b, and a switching control unit 16c. The determination unit 16a determines whether the storage battery modules 30, 40 should be connected in parallel or in series, based on a request to the power conversion system 10. Here, in addition to the high-voltage charger 90 described above, an external charger electrically connected to the power conversion system 10 also includes a low-voltage charger 91. The charging voltage of the low-voltage charger 91 is lower than the sum of the voltages Vb1, Vb2 of the storage batteries 31, 41, but higher than the voltages Vb1, Vb2 of the storage batteries 31, 41.

[0070] In this embodiment, when a high-voltage charger 90 is electrically connected to the power conversion system 10, a request is made to the power conversion system 10 to connect the storage battery modules 30, 40 in series. Also, when a low-voltage charger 91 is electrically connected to the power conversion system 10, a request is made to the power conversion system 10 to connect the storage battery modules 30, 40 in parallel.

[0071] The determination unit 16a determines that the storage battery modules 30, 40 should be connected in series when the high-voltage charger 90 is electrically connected to the power conversion system 10. On the other hand, the determination unit 16a determines that the storage battery modules 30, 40 should be connected in parallel when the low-voltage charger 91 is electrically connected to the power conversion system 10. For example, the determination unit 16a can determine whether the external charger is the high-voltage charger 90 or the low-voltage charger 91 based on information received from the external charger electrically connected to the power conversion system 10.

[0072] The connection control unit 16b controls the series connection switch 61 and the parallel connection switches 62a, 62b to place the storage battery modules 30, 40 in either a parallel connection state or a series connection state based on the determination result of the determination unit 16a. Specifically, when the determination unit 16a determines that the storage battery modules 30, 40 should be placed in a series connection state, the connection control unit 16b turns on the series connection switch 61 and turns off the parallel connection switches 62a, 62b. When the determination unit 16a determines that the storage battery modules 30, 40 should be placed in a parallel connection state, the connection control unit 16b turns off the series connection switch 61 and turns on the parallel connection switches 62a, 62b.

[0073] When the storage battery modules 30, 40 are connected in parallel, the switching control unit 16c performs switching control to adjust the voltage difference between the storage batteries 31, 41. In this embodiment, the switching control unit 16c causes the power converters 32, 42 to perform a voltage adjustment operation to adjust the output voltage of the storage battery module 30, 40 with a lower storage battery voltage closer to the output voltage of the storage battery module 30, 40 with a higher storage battery voltage. This prevents the charging current from the low-voltage charger 91 from being biased toward the storage battery module 30, 40 with the lower storage battery voltage. This allows the storage battery modules 30, 40 to be appropriately connected in parallel. Note that the switching control unit 16c may use at least one of the detection values ​​of the sensors 80, 81, 82a, 82b, 83a, 83b, 84a, 84b, 85a, 85b, 86a, and 86b to cause the power converters 32, 42 to perform the voltage adjustment operation.

[0074] In this embodiment, the switching control unit 16c selects the power converter that performs the above-described voltage adjustment operation based on the voltages Vb1 and Vb2 of the storage batteries 31 and 41. The switching control unit 16c can use the detection values ​​of the primary-side voltage sensors 83a and 83b as the voltages Vb1 and Vb2 of the storage batteries 31 and 41.

[0075] More specifically, when the storage battery modules 30, 40 are connected in parallel, the switching control unit 16c determines whether the voltage Vb2 of the second storage battery 41 is higher than the voltage Vb1 of the first storage battery 31. When the switching control unit 16c determines that the voltage Vb2 of the second storage battery 41 is higher than the voltage Vb1 of the first storage battery 31, the switching control unit 16c performs a voltage adjustment operation in the first power converter 32 and stops the voltage adjustment operation of the second power converter 42. On the other hand, when the switching control unit 16c determines that the voltage Vb2 of the second storage battery 41 is equal to or lower than the voltage Vb1 of the first storage battery 31, the switching control unit 16c stops the voltage adjustment operation of the first power converter 32 and performs a voltage adjustment operation in the second power converter 42.

[0076] FIG. 6 shows an example of operation when the voltage Vb2 of the second storage battery 41 is determined to be higher than the voltage Vb1 of the first storage battery 31 when the storage batteries 31, 41 are being charged by the low-voltage charger 91.

[0077] The switching control unit 16c outputs an OFF command as a drive command Sg1b to the primary-side switch of the second power converter 42, and outputs an ON command as a drive command Sg2b to the secondary-side switch of the second power converter 42. In this case, the voltage adjustment operation of the second power converter 42 is stopped with the primary-side switch fixed OFF and the secondary-side switch fixed ON. As a result, the secondary-side terminal voltage Vo2 of the second power converter 42 is set to a value near 0 V. The ON command is output to the secondary-side switch of the second power converter 42 so that charging current from the low-voltage charger 91 flows to the second storage battery module 40.

[0078] The switching control unit 16c outputs switching commands consisting of ON commands and OFF commands as a drive command Sg1a for the primary-side switches S1 to S4 of the first power converter 32 and a drive command Sg2a for the secondary-side switches Q1a, Q2a of the first power converter 32. In this case, the switching control unit 16c outputs drive commands for the switches S1 to S4, Q1a, Q2a of the first power converter 32 so as to bring the output voltage of the first storage battery module 30 closer to the output voltage of the second storage battery module 40 (here, the voltage Vb2 of the second storage battery 41).

[0079] For example, when the voltage Vb1 of the first storage battery 31 is 390 V and the voltage Vb2 of the second storage battery 41 is 400 V, the switching control unit 16c outputs a switching command to each switch S1 to S4, Q1a, and Q2a of the first power converter 32 so as to control the secondary terminal voltage Vo1 of the first power converter 32 to 10 V.

[0080] 7 shows a control procedure performed by the control device 16. This control is executed by the processor of the control device 16 when, for example, an external charger is electrically connected to the power conversion system 10.

[0081] In step S10, the determination unit 16a determines whether to connect the battery modules 30, 40 in parallel. In this embodiment, if the low-voltage charger 91 is electrically connected to the power conversion system 10, a positive determination is made in step S10. On the other hand, if the high-voltage charger 90 is electrically connected to the power conversion system 10, a negative determination is made in step S10.

[0082] If the determination in step S10 is negative, the process proceeds to step S11. In step S11, the connection control unit 16b turns on the series connection switch 61 and turns off the parallel connection switches 62a and 62b. This connects the storage battery modules 30 and 40 in series.

[0083] In this embodiment, when the storage battery modules 30, 40 are connected in series, the voltage adjustment operation of each power converter 32, 42 is stopped. For example, the voltage adjustment operation is stopped when the switches of each power converter 32, 42 are fixed to the off state.

[0084] If the determination in step S10 is affirmative, the process proceeds to step S12. In step S12, the connection control unit 16b turns off the series connection switch 61 and turns on the parallel connection switches 62a and 62b. This connects the storage battery modules 30 and 40 in parallel.

[0085] In step S13, the switching control unit 16c selects a power converter that performs voltage adjustment operation based on the voltages Vb1 and Vb2 of the storage batteries 31 and 41. Specifically, the switching control unit 16c determines whether the voltage Vb2 of the second storage battery 41 is higher than the voltage Vb1 of the first storage battery 31.

[0086] If the determination in step S13 is affirmative, the first power converter 32 is selected as the power converter that will perform the voltage adjustment operation, and the process proceeds to step S14. In step S14, the switching control unit 16c performs the voltage adjustment operation of the first power converter 32 and stops the voltage adjustment operation of the second power converter 42.

[0087] If the determination in step S13 is negative, the second power converter 42 is selected as the power converter that will perform the voltage adjustment operation, and the process proceeds to step S15. In step S15, the switching control unit 16c stops the voltage adjustment operation of the first power converter 32 and performs the voltage adjustment operation of the second power converter 42.

[0088] According to this embodiment, the storage battery modules 30, 40 are connected in parallel or in series in response to demands on the power conversion system 10. When the storage battery modules 30, 40 are connected in parallel, switching control of the power converters 32, 42 is performed to adjust the voltage difference between the storage batteries 31, 41. This allows the storage battery modules 30, 40 to be appropriately connected in parallel. This allows the power converters 32, 42 to operate appropriately in response to demands on the power conversion system 10.

[0089] The power converter that performs the voltage adjustment operation is selected based on the voltages Vb1, Vb2 of the storage batteries 31, 41. In this embodiment, the power converter corresponding to the storage battery 31, 41 with the lower voltage performs the voltage adjustment operation, and the power converter corresponding to the storage battery 31, 41 with the higher voltage stops the voltage adjustment operation. This makes it possible to prevent unnecessary switching control from being performed, and realizes a configuration that is suitable for reducing power loss in the power conversion system 10.

[0090] <Modification of the First Embodiment> Only one of the storage battery modules 30, 40 may include a power converter. For example, in FIG. 8 , the first storage battery module 30 includes the first power converter 32, and the second storage battery module 40 does not include a power converter. In the second storage battery module 40, the second end of the first module path 63b is electrically connected to the low-potential-side path 12 instead of the secondary-side positive terminal 42c of the second power converter 42. In the above-described configuration, of the storage batteries 31, 41, only the first storage battery 31 corresponds to the "specific power storage unit."

[0091] In this embodiment, the output voltage of the first storage battery module 30 is the sum of the voltage Vb1 of the first storage battery 31 and the secondary-side terminal voltage Vo1 of the first power converter 32, and the output voltage of the second storage battery module 40 is the voltage Vb2 of the second storage battery 41. In this regard, the voltage Vb1 of the first storage battery 31 may be lower than the voltage Vb2 of the second storage battery 41. As a result, when the storage battery modules 30, 40 are connected in parallel, adding the secondary-side terminal voltage Vo1 to the voltage Vb1 of the first storage battery 31 makes it possible to adjust the balance with the voltage Vb2 of the second storage battery 41. The following four situations, for example, are possible as situations in which the voltage Vb1 of the first storage battery 31 becomes lower than the voltage Vb2 of the second storage battery 41.

[0092] The first situation is when the battery cells constituting the first storage battery 31 have a lower rated voltage than the battery cells constituting the second storage battery 41 .

[0093] The second situation is when the number of battery cells constituting the first storage battery 31 is smaller than the number of battery cells constituting the second storage battery 41 .

[0094] The third situation is when a storage battery that is more deteriorated than the second storage battery 41 is used as the first storage battery 31 .

[0095] The fourth situation is when, as the power conversion system 10 is used, each storage battery 31, 41 is affected by temperature and degree of deterioration (e.g., SOH), and the voltage Vb1 of the first storage battery 31 becomes lower than the voltage Vb2 (or SOC) of the second storage battery 41.

[0096] In this embodiment, the process may proceed to step S14 after the process of step S12 in Fig. 7, and in step S14, the voltage adjustment operation of the first power converter 32 may be performed. Also, the processes of steps S13 and S15 may not be performed.

[0097] 8, it is also possible for the first storage battery module 30 to not include a power converter, and for the second storage battery module 40 to include a second power converter 42. In this case, of the storage batteries 31, 41, only the second storage battery 41 corresponds to the "specific power storage unit."

[0098] The power conversion system 10 may include three or more storage battery modules. In Fig. 9 , the power conversion system 10 includes a third storage battery module 50 in addition to the first and second storage battery modules 30, 40. The third storage battery module 50 has the same configuration as the second storage battery module 40. Note that the high-voltage load 20 is not shown in Fig. 9 .

[0099] Specifically, the third storage battery module 50 includes a third storage battery 51, a third power converter 52, and a third drive circuit 53. The third storage battery 51 is, for example, a battery pack configured as a series connection of battery cells serving as single cells. The third power converter 52 may be the center-tapped isolated DC-DC converter described above in FIG. 2 . In the third power converter 52, a primary-side positive terminal 52a is electrically connected to the positive side of the third storage battery 51, and a primary-side negative terminal 52b is electrically connected to the negative side of the third storage battery 51. The secondary-side terminal pair of the third power converter 52 is connected in series to the third storage battery 51 on the negative side of the third storage battery 51. In this embodiment, each of the storage batteries 31, 41, and 51 corresponds to a "specific power storage unit."

[0100] A drive command is input to the third drive circuit 53 from the control device 16. The third drive circuit 53 turns on and off the primary-side switch and the secondary-side switch of the third power converter 52 based on the input drive command.

[0101] The third storage battery module 50 includes a first module path 63c, a second module path 64c, and a third module path 65c. In the third storage battery module 50, a first end of the first module path 63c is electrically connected to a secondary-side positive terminal 52c of the third power converter 52, and a second end of the first module path 63c is electrically connected to a negative terminal of the third storage battery 51. A first end of the second module path 64c is electrically connected to a secondary-side negative terminal 52d of the third power converter 52, and a second end of the second module path 64c is electrically connected to the low-potential-side path 12. A first end of the third module path 65c is electrically connected to the high-potential-side path 11, and a second end of the third module path 65c is electrically connected to a positive terminal of the third storage battery 51.

[0102] The power conversion system 10 includes a first series connection path 60a, a second series connection path 60b, a first series connection switch 61a, and a second series connection switch 61b instead of the series connection path 60 and the series connection switch 61. The first series connection path 60a is a path that connects the first storage battery 31 and the third storage battery 51 in series. The first series connection switch 61a is provided in the first series connection path 60a. The second series connection path 60b is a path that connects the second storage battery 41 and the third storage battery 51 in series. The second series connection switch 61b is provided in the second series connection path 60b.

[0103] More specifically, a first end of the first series connection path 60a is electrically connected to the second module path 64a of the first storage battery module 30. A first parallel connection switch 62a is provided in the second module path 64a of the first storage battery module 30 on a side with a higher potential than the connection point with the first series connection path 60a. A second end of the first series connection path 60a is electrically connected to the first module path 63c of the third storage battery module 50. A first end of the second series connection path 60b is electrically connected to the third module path 65c of the third storage battery module 50. A second end of the second series connection path 60b is electrically connected to the first module path 63b of the second storage battery module 40. A second parallel connection switch 62b is provided in the first module path 63b of the second storage battery module 40 on a side with a lower potential than the connection point with the second series connection path 60b.

[0104] In this embodiment, the high-potential side path 11, the first and second module paths 63a and 64a of the first storage battery module 30, the third module path 65b of the second storage battery module 40, and the third module path 65c of the third storage battery module 50 correspond to the "positive electrode path." The low-potential side path 12, the third module path 65a of the first storage battery module 30, the first and second module paths 63b and 64b of the second storage battery module 40, and the first and second module paths 63c and 64c of the third storage battery module 50 correspond to the "negative electrode path."

[0105] The power conversion system 10 includes a third parallel connection switch 62c and a fourth parallel connection switch 62d. The third and fourth parallel connection switches 62c and 62d are provided corresponding to the third storage battery module 50. The third and fourth parallel connection switches 62c and 62d are mechanical relays or semiconductor switching elements. The third and fourth parallel connection switches 62c and 62d are controlled by the control device 16.

[0106] In the present embodiment, the third parallel connection switch 62c is provided on the first module path 63c of the third storage battery module 50 on the lower potential side of the connection point with the first series connection path 60a. The fourth parallel connection switch 62d is provided on the third module path 65c of the third storage battery module 50 on the higher potential side of the connection point with the second series connection path 60b.

[0107] When connecting the storage battery modules 30, 40, 50 in parallel, the control device 16 turns off the series connection switches 61 a, 61 b ​​and turns on the parallel connection switches 62 a, 62 b, 62 c, 62 d. When connecting the storage battery modules 30, 40, 50 in series, the control device 16 turns on the series connection switches 61 a, 61 b ​​and turns off the parallel connection switches 62 a, 62 b, 62 c, 62 d.

[0108] When the storage battery modules 30, 40, 50 are connected in series, the high-potential side path 11, the low-potential side path 12, the series connection paths 60a, 60b, and the third module paths 65a, 65b of the first and second storage battery modules 30, 40 form current paths for the series-connected bodies of the storage batteries 31, 41, 51. In this embodiment, the third storage battery 51 corresponds to the "intermediate power storage unit."

[0109] The power conversion system 10 includes three storage batteries 31, 41, and 51, and a third power converter 52 is provided corresponding to the third storage battery 51. In this case, when the third parallel connection switch 62c in the third storage battery module 50 is turned off, the third storage battery 51 and the series connection paths 60a and 60b are electrically disconnected from the secondary-side terminal pair of the third power converter 52. This prevents current flowing through the current paths of the series-connected body of the storage batteries 31, 41, and 51 from flowing to the first and second power converters 32, 42, and the third power converter 52. As a result, conduction loss in the power converters 32, 42, and 52 can be reduced.

[0110] In this embodiment, when the storage battery modules 30, 40, 50 are connected in parallel, the control device 16 may select a power converter to perform voltage regulation based on the voltages Vb1, Vb2, Vb3 of the storage batteries 31, 41, 51. For example, the control device 16 may perform voltage regulation in the power converters corresponding to the storage batteries other than the one with the highest voltage among the storage batteries 31, 41, 51, and stop voltage regulation in the power converter corresponding to the storage battery with the highest voltage. Even in this case, unnecessary switching control can be prevented from being performed.

[0111] In the third storage battery module 50, the secondary-side terminal pair of the third power converter 52 may be connected in series to the third storage battery 51 on the positive side of the third storage battery 51 instead of on the negative side of the third storage battery 51. Even in this case, by configuring the third storage battery module 50 in the same manner as the first storage battery module 30 described above in FIG. 1 , for example, it is possible to realize a configuration in which the secondary-side terminal pair of the third power converter 52 is electrically isolated from each of the storage batteries 31, 41, 51.

[0112] In a power conversion system including three or more storage battery modules, at least one of the storage battery modules may include a power converter.

[0113] 10 , in a power conversion system including three storage battery modules 30, 40, and 50, the first and second storage battery modules 30 and 40 may not include a power converter, and the third storage battery module 50 may include a third power converter 52. In this case, the third storage battery 51 corresponds to the “specific power storage unit.”

[0114] In the first storage battery module 30, a first end of the second module path 64a is electrically connected to the high-potential-side path 11 instead of the secondary-side negative terminal 32d of the first power converter 32. The second storage battery module 40 has the same configuration as that described above with reference to FIG.

[0115] In this embodiment, the voltage Vb3 of the third storage battery 51 may be set lower than the voltages Vb1 and Vb2 of the first and second storage batteries 31 and 41. As a result, when the storage battery modules 30, 40, and 50 are connected in parallel, the secondary-side terminal voltage Vo3 is added to the voltage Vb3 of the third storage battery 51, thereby making it possible to adjust the balance with the voltages Vb1 and Vb2 of the first and second storage batteries 31 and 41.

[0116] 10 , the configuration is not limited to the configuration described in Fig. 10 , and it is also possible for the first storage battery module 30 to be equipped with the first power converter 32, and the second and third storage battery modules 40, 50 to be equipped with no power converters. It is also possible for the second storage battery module 40 to be equipped with the second power converter 42, and the first and third storage battery modules 30, 50 to be equipped with no power converters. In other words, it is also possible for only one of the storage battery modules 30, 40, 50 to be equipped with a power converter, and the remaining storage battery modules 30, 40, 50 to be equipped with no power converters.

[0117] It is also possible to configure the storage battery modules 30, 40, 50 so that only one of them does not have a power converter, and the remaining storage battery modules 30, 40, 50 have power converters.

[0118] The secondary side terminal pair of the first power converter 32 may be electrically connected in series to the first storage battery 31 at the negative electrode side of the first storage battery 31 instead of at the positive electrode side of the first storage battery 31. The secondary side terminal pair of the second power converter 42 may be electrically connected in series to the second storage battery 41 at the positive electrode side of the second storage battery 41 instead of at the negative electrode side of the second storage battery 41. Even in the above-mentioned case, it is possible to realize a configuration in which the secondary side terminal pairs of the power converters 32, 42 are electrically isolated from the storage batteries 31, 41.

[0119] 11 shows an example of a configuration in which, when the storage battery modules 30, 40 are connected in series, each storage battery 31, 41 can be electrically disconnected from a secondary-side terminal pair of the second power converter 242. In the second power converter 242, the secondary-side terminal pair is electrically connected in series to the second storage battery 41 on the positive electrode side of the second storage battery 41.

[0120] In the second storage battery module 40, a first end of the first module path 263b is electrically connected to the secondary-side positive terminal 242c of the second power converter 242, and a second end of the first module path 263b is electrically connected to the high-potential-side path 11. A first end of the second module path 264b is electrically connected to the secondary-side negative terminal 242d of the second power converter 242, and a second end of the second module path 264b is electrically connected to the positive terminal of the second storage battery 41. A first end of the third module path 265b is electrically connected to the negative terminal of the second storage battery 41, and a second end of the third module path 265b is electrically connected to the low-potential-side path 12.

[0121] A second end of the series connection path 60 is electrically connected to the third module path 265b of the second storage battery module 40. A second parallel connection switch 262b is provided on the second module path 264b.

[0122] The second storage battery module 40 includes a fourth module path 266b, a first additional switch 267b, and a second additional switch 268b. A first end of the fourth module path 266b is electrically connected to the second module path 264b on the lower potential side than the second parallel-connection switch 262b. A second end of the fourth module path 266b is electrically connected to the high-potential-side path 11.

[0123] In this embodiment, the high-potential side path 11, the first and second module paths 63a and 64a of the first storage battery module 30, and the first and second module paths 263b and 264b of the second storage battery module 40 correspond to the "positive electrode path." The low-potential side path 12, the third module path 65a of the first storage battery module 30, and the third module path 265b of the second storage battery module 40 correspond to the "negative electrode path."

[0124] Each of the additional switches 267b and 268b is a mechanical relay or a semiconductor switching element. When turned off, each of the additional switches 267b and 268b blocks bidirectional current flow, and when turned on, each of the additional switches 267b and 268b allows bidirectional current flow. Each of the additional switches 267b and 268b is controlled by the control device 16.

[0125] The additional switches 267b, 268b are switches additionally provided in the power conversion system 10 to switch the electrical connection relationship of the storage battery modules 30, 40. The first additional switch 267b is provided in the fourth module path 266b. The second additional switch 268b is provided in the third module path 265b of the second storage battery module 40, on the lower potential side of the connection point with the series connection path 60.

[0126] When connecting the storage battery modules 30, 40 in parallel, the control device 16 turns off the series connection switch 61 and the first additional switch 267b and turns on the parallel connection switches 62a, 262b and the second additional switch 268b. When connecting the storage battery modules 30, 40 in series, the control device 16 turns on the series connection switch 61 and the first additional switch 267b and turns off the parallel connection switches 62a, 262b and the second additional switch 268b.

[0127] When the storage battery modules 30, 40 are connected in series, the high-potential side path 11, the low-potential side path 12, the series connection path 60, the third module path 65a and the fourth module path 266b of the first storage battery module 30 form the current paths of the series connection of the storage batteries 31, 41.

[0128] In this embodiment as well, it is possible to realize a configuration in which, when the storage battery modules 30, 40 are connected in series, the storage batteries 31, 41 are electrically isolated from the secondary-side terminal pairs of the second power converter 242. However, in this embodiment, a fourth module path 266b and additional switches 267b, 268b are added to the power conversion system 10.

[0129] In this regard, in the first embodiment, the secondary-side terminal pair of the first power converter 32 is electrically connected in series to the first storage battery 31 via the first and second module paths 63 a, 64 a of the first storage battery module 30. Also, the secondary-side terminal pair of the second power converter 42 is electrically connected in series to the second storage battery 41 on the negative electrode side of the second storage battery 41 via the first and second module paths 63 b, 64 b of the second storage battery module 40.

[0130] That is, in the first embodiment, the secondary-side terminal pairs of each power converter 32, 42 are connected in series to the corresponding storage batteries 31, 41 via first and second module paths 63a, 64a, 63b, 64b, which do not form the current paths for the series-connected storage batteries 31, 41. In this case, when the storage battery modules 30, 40 are connected in series, the existing third module paths 65a, 65b are used as the current paths for the series-connected storage batteries 31, 41. Furthermore, the parallel connection switches 62a, 62b are used to switch the electrical connection relationship of the storage battery modules 30, 40 and to electrically connect or disconnect the secondary-side terminal pairs of the power converter and the storage batteries. This makes it possible to prevent components such as electrical wiring and switches for forming the current paths for the series-connected storage batteries 31, 41 from being added to the power conversion system 10. Therefore, when the storage battery modules 30, 40 are connected in series, a configuration can be preferably realized in which the storage batteries 31, 41 and the secondary terminal pairs of the power converters 32, 42 are electrically isolated from each other.

[0131] In a configuration in which the secondary-side terminal pair of the first power converter is electrically connected in series to the first storage battery 31 on the negative electrode side of the first storage battery 31, a fourth module path and an additional switch may be added, as described above with reference to Fig. 11. Even in this case, it is possible to realize a configuration in which each storage battery 31, 41 and the secondary-side terminal pair of the first power converter are electrically isolated from each other.

[0132] The first parallel connection switch 62a may be provided in the first module path 63a of the first storage battery module 30 instead of the second module path 64a of the first storage battery module 30. Furthermore, the second parallel connection switch 62b may be provided in the second module path 64b of the second storage battery module 40 instead of the first module path 63b of the second storage battery module 40.

[0133] When the storage battery modules 30, 40 are connected in parallel, the switching control unit 16c does not necessarily perform voltage adjustment operation in one of the power converters 32, 42. When the storage battery modules 30, 40 are connected in parallel, the switching control unit 16c may perform switching control in both of the power converters 32, 42 to adjust the output voltage of each storage battery module 30, 40.

[0134] For example, when the storage battery modules 30, 40 are connected in parallel, the switching control unit 16c may adjust the output voltage of each storage battery module 30, 40 so that the storage amounts (e.g., SOC) of the storage batteries 31, 41 are the same. Furthermore, when the storage battery modules 30, 40 are connected in parallel, the switching control unit 16c may adjust the output voltage of each storage battery module 30, 40 so that the SOC of one of the storage batteries 31, 41 deviates from the other. The switching control unit 16c may use the storage amounts of the storage batteries 31, 41 calculated based on at least one of the detection values ​​of the module current sensors 82a, 82b and the detection values ​​of the primary-side voltage sensors 83a, 83b for the above-described switching control.

[0135] Second Embodiment A second embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, as shown in Fig. 12, a power conversion system 10 includes a low-voltage load 100. The low-voltage load 100 is an on-board auxiliary device, a control device, or the like that operates when supplied with a voltage (e.g., 12 V) lower than the voltages Vb1 and Vb2 of the storage batteries 31 and 41.

[0136] The power conversion system 10 includes a first auxiliary path 101, a second auxiliary path 102, a third auxiliary path 103, and a fourth auxiliary path 104. A first end of the first auxiliary path 101 is electrically connected to the secondary-side positive terminal 32c of the first power converter 32. A second end of the first auxiliary path 101 is electrically connected to the positive side of the low-voltage load 100. A first end of the second auxiliary path 102 is electrically connected to the secondary-side negative terminal 32d of the first power converter 32. A second end of the second auxiliary path 102 is electrically connected to the negative side of the low-voltage load 100.

[0137] A first end of the third auxiliary path 103 is electrically connected to the secondary-side positive terminal 42 c of the second power converter 42. A second end of the third auxiliary path 103 is electrically connected to the positive side of the low-voltage load 100. A first end of the fourth auxiliary path 104 is electrically connected to the secondary-side negative terminal 42 d of the second power converter 42. A second end of the fourth auxiliary path 104 is electrically connected to the negative side of the low-voltage load 100.

[0138] The power conversion system 10 includes a first auxiliary switch 111, a second auxiliary switch 112, a third auxiliary switch 113, and a fourth auxiliary switch 114. Each of the switches 111 to 114 is a mechanical relay or a semiconductor switching element. When turned off, each of the switches 111 to 114 blocks bidirectional current flow, and when turned on, each of the switches 111 to 114 allows bidirectional current flow. Each of the switches 111 to 114 is controlled by a control device 16.

[0139] Each of the auxiliary switches 111 to 114 is provided in a corresponding auxiliary path 101 to 104. Specifically, the first auxiliary switch 111 is provided in the first auxiliary path 101. The second auxiliary switch 112 is provided in the second auxiliary path 102. The third auxiliary switch 113 is provided in the third auxiliary path 103. The fourth auxiliary switch 114 is provided in the fourth auxiliary path 104.

[0140] In this embodiment, the power conversion system 10 includes two module switches for each of the first and second storage battery modules 30, 40. The first storage battery module 30 includes a first module switch 362a and a second module switch 362b. The second storage battery module 40 includes a third module switch 362c and a fourth module switch 362d. Each of the switches 362a, 362b, 362c, and 362d is a mechanical relay or a semiconductor switching element. When turned off, each of the switches 362a, 362b, 362c, and 362d blocks bidirectional current flow, and when turned on, each of the switches 362a, 362b, 362c, and 362d allows bidirectional current flow. Each of the switches 362a, 362b, 362c, and 362d is controlled by the control device 16.

[0141] The first module switch 362a is provided on the second module path 64a of the first storage battery module 30. The second module switch 362b is provided on the first module path 63a of the first storage battery module 30. The third module switch 362c is provided on the first module path 63b of the second storage battery module 40. The fourth module switch 362d is provided on the second module path 64b of the second storage battery module 40. In this embodiment, the module switches 362a, 362b, 362c, and 362d correspond to "parallel connection switches."

[0142] The power conversion system 10 includes a first bypass path 401, a second bypass path 402, a first bypass switch 403, and a second bypass switch 404. A first end of the first bypass path 401 is electrically connected to a part of the first module path 63a of the first storage battery module 30 that is on the higher potential side than the second module switch 362b. A second end of the first bypass path 401 is electrically connected to a part of the second module path 64a of the first storage battery module 30 between the first storage battery 31 and the first module switch 362a. The first bypass switch 403 is provided on the first bypass path 401.

[0143] A first end of the second bypass path 402 is electrically connected to the first module path 63b of the second storage battery module 40 between the second storage battery 41 and the third module switch 362c. A second end of the second bypass path 402 is electrically connected to the second module path 64b of the second storage battery module 40 on the lower potential side than the fourth module switch 362d. A second bypass switch 404 is provided on the second bypass path 402.

[0144] Each of the bypass switches 403 and 404 is a mechanical relay or a semiconductor switching element. When turned off, each of the bypass switches 403 and 404 blocks bidirectional current flow, and when turned on, each of the bypass switches 403 and 404 allows bidirectional current flow. Each of the bypass switches 403 and 404 is controlled by the control device 16.

[0145] In the above-described configuration, when the first and second auxiliary switches 111, 112 are turned on, the secondary terminal pair of the first power converter 32 is electrically connected to the low-voltage load 100. In this case, it is possible to supply power from the first power converter 32 to the low-voltage load 100. Furthermore, when the third and fourth auxiliary switches 113, 114 are turned on, the secondary terminal pair of the second power converter 42 is electrically connected to the low-voltage load 100. In this case, it is possible to supply power from the second power converter 42 to the low-voltage load 100.

[0146] In this embodiment, the storage battery modules 30, 40 are connected in series by turning off the module switches 362a, 362b, 362c, 362d and the bypass switches 403, 404 and by turning on the series connection switch 61. The storage battery modules 30, 40 are connected in parallel by turning on the module switches 362a, 362b, 362c, 362d and by turning off the series connection switch 61 and the bypass switches 403, 404.

[0147] In the first storage battery module 30, turning off the first and second module switches 362a, 362b electrically insulates the low-voltage load 100 from high-voltage side components such as the first storage battery 31 and the high-voltage load 20. In the second storage battery module 40, turning off the third and fourth module switches 362c, 362d electrically insulates the low-voltage load 100 from high-voltage side components such as the second storage battery 41 and the high-voltage load 20.

[0148] That is, in this embodiment, the module switches 362a, 362b, 362c, and 362d are used to switch the electrical connection relationship between the storage battery modules 30 and 40, and also to ensure electrical insulation between the low-voltage load 100 and the high-voltage side components. Therefore, it is possible to realize a configuration that can supply power to the low-voltage load 100 while suppressing an increase in the number of components in the power conversion system 10.

[0149] When the storage battery modules 30, 40 are connected in parallel, the switching control unit 16c may cause one of the power converters 32, 42, other than the regulating power converter performing the voltage regulation operation, to perform a power supply operation. The power supply operation is switching control for supplying power to the low-voltage load 100. Note that the switching control unit 16c may use at least one of the detection values ​​of the secondary-side voltage sensors 85a, 85b and the detection values ​​of the secondary-side current sensors 86a, 86b to cause the power converters 32, 42 to perform the power supply operation.

[0150] In this embodiment, the switching control unit 16c acquires the required power Pt of the low-voltage load 100. When the acquired required power Pt is higher than a predetermined lower limit specified value PL, the switching control unit 16c causes the power converter that is not performing the voltage adjustment operation to perform the power supply operation.

[0151] When the storage battery modules 30, 40 are connected in series, the switching control unit 16c may cause the power converters 32, 42 to perform power supply operations. In the present embodiment, the switching control unit 16c changes the number of power converters that perform power supply operations based on the acquired required power Pt.

[0152] Specifically, when the acquired required power Pt is higher than a predetermined high load specified value PA, the switching control unit 16c performs power supply operation in both of the power converters 32, 42. When the acquired required power Pt is equal to or lower than the high load specified value PA and higher than the low load specified value PB, the switching control unit 16c performs power supply operation in only one of the power converters 32, 42. Here, the low load specified value PB is a value smaller than the high load specified value PA. When the acquired required power Pt is equal to or lower than the low load specified value PB, the switching control unit 16c stops the power supply operation in both of the power converters 32, 42. Note that the low load specified value PB and the lower limit specified value PL may be the same value.

[0153] Fig. 13 shows the procedure of the control performed by the control device 16. This control is executed by the processor of the control device 16 when an external charger is electrically connected to the power conversion system 10. In Fig. 13, the processes of steps S10 and S13 to S15 are the same as those described above in Fig. 7.

[0154] If the determination in step S10 is affirmative, the process proceeds to step S21. In step S21, the connection control unit 16b turns off the series connection switch 61, the first to fourth auxiliary switches 111 to 114, and the bypass switches 403 and 404, and turns on the first to fourth module switches 362a, 362b, 362c, and 362d. This connects the storage battery modules 30 and 40 in parallel. Furthermore, because the first to fourth auxiliary switches 111 to 114 are turned off, electrical insulation between the low-voltage load 100 and the high-voltage side components can be ensured.

[0155] After the process of step S14, the process proceeds to step S22. In step S22, the switching control unit 16c acquires the required power Pt of the low-voltage load 100. Then, it is determined whether the acquired required power Pt is higher than the lower limit specified value PL.

[0156] If the determination in step S22 is affirmative, the process proceeds to step S23. In step S23, the switching control unit 16c performs processing to cause the second power converter 42 to supply power. Specifically, the switching control unit 16c performs processing to turn off the third and fourth module switches 362c, 362d, turn on the second bypass switch 404, and turn on the third and fourth auxiliary switches 113, 114 as processing to cause the second power converter 42 to supply power. By turning off the third and fourth module switches 362c, 362d, the secondary-side terminal pair of the second power converter 42 is electrically disconnected from the second storage battery 41 and the low-potential-side path 12. By turning on the second bypass switch 404, the parallel connection state of the storage battery modules 30, 40 continues. By turning on the third and fourth auxiliary switches 113 and 114, the second power converter 42 is enabled to supply power to the low-voltage load 100.

[0157] For example, the switching control unit 16c performs a process of turning off the third and fourth module switches 362c and 362d and a process of turning on the second bypass switch 404 as a process of causing the second power converter 42 to perform a power supply operation. Thereafter, the switching control unit 16c performs a process of turning on the third and fourth auxiliary switches 113 and 114.

[0158] Furthermore, for example, the switching control unit 16c performs a process of turning off the third and fourth module switches 362c and 362d as a process of causing the second power converter 42 to perform a power supply operation. Thereafter, the switching control unit 16c performs a process of turning on the third and fourth auxiliary equipment switches 113 and 114 prior to performing a process of turning on the second bypass switch 404.

[0159] By performing the above-described process for causing the second power converter 42 to perform a power supply operation, it is possible to ensure electrical insulation between the low-voltage load 100 and the high-voltage side components, while making it possible to perform a power supply operation to the second power converter 42. In this case, the first power converter 32 performs a voltage adjustment operation, and the second power converter 42 performs a power supply operation.

[0160] On the other hand, if a negative determination is made in step S22, the control ends with the voltage adjustment operation and power supply operation of the second power converter 42 stopped.

[0161] After the process of step S15, the process proceeds to step S24. The process of step S24 is the same as the process of step S22. If the determination in step S24 is affirmative, the process proceeds to step S25. In step S25, the switching control unit 16c performs a process for causing the first power converter 32 to perform a power supply operation. Specifically, the switching control unit 16c performs the process for causing the first power converter 32 to perform a power supply operation by turning off the first and second module switches 362a and 362b, turning on the first bypass switch 403, and turning on the first and second auxiliary switches 111 and 112. By turning off the first and second module switches 362a and 362b, the secondary-side terminal pair of the first power converter 32 is electrically disconnected from the first storage battery 31 and the high-potential-side path 11. By turning on the first bypass switch 403, the parallel connection state of the storage battery modules 30, 40 continues. When the first and second auxiliary switches 111 and 112 are turned on, the first power converter 32 is placed in a state where it can supply electric power to the low-voltage load 100 .

[0162] For example, the switching control unit 16c performs a process of turning off the first and second module switches 362a and 362b and a process of turning on the first bypass switch 403 as a process of causing the first power converter 32 to perform a power supply operation. Thereafter, the switching control unit 16c performs a process of turning on the first and second auxiliary switches 111 and 112.

[0163] Furthermore, for example, the switching control unit 16c performs a process of turning off the first and second module switches 362a and 362b as a process of causing the first power converter 32 to perform a power supply operation. Thereafter, the switching control unit 16c performs a process of turning on the first and second auxiliary switches 111 and 112 prior to performing a process of turning on the first bypass switch 403.

[0164] By performing the above-described process for causing the first power converter 32 to perform a power supply operation, it is possible to ensure electrical insulation between the low-voltage load 100 and the high-voltage side components, while making it possible to perform a power supply operation to the first power converter 32. In this case, the first power converter 32 performs a power supply operation, and the second power converter 42 performs a voltage adjustment operation.

[0165] On the other hand, if a negative determination is made in step S24, the control ends with the voltage adjustment operation and power supply operation of the first power converter 32 stopped.

[0166] If the determination in step S10 is negative, the process proceeds to step S20. In step S20, the connection control unit 16b turns on the series connection switch 61 and the first to fourth auxiliary switches 111 to 114, and turns off the first to fourth module switches 362a, 362b, 362c, and 362d and the bypass switches 403 and 404. This connects the storage battery modules 30 and 40 in series. Furthermore, a state is established in which power can be supplied from the power converters 32 and 42 to the low-voltage load 100 while ensuring electrical insulation between the low-voltage load 100 and the high-voltage side components.

[0167] After the processing of step S20, the process proceeds to step S26. In step S26, the switching control unit 16c acquires the required power Pt of the low-voltage load 100. Then, it is determined whether the acquired required power Pt is higher than the high-load specified value PA. If the determination in step S26 is negative, the process proceeds to step S27. In step S27, it is determined whether the acquired required power Pt is higher than the low-load specified value PB. If the determination in step S27 is negative, the voltage adjustment operation and power supply operation of each power converter 32, 42 are stopped, and this control is terminated.

[0168] If the determination in step S26 is affirmative, the process proceeds to step S28. In step S28, the switching control unit 16c causes both of the power converters 32 and 42 to perform power supply operations.

[0169] If the determination in step S27 is affirmative, the process proceeds to step S29. In step S29, the switching control unit 16c causes one of the power converters 32 and 42 to perform a power supply operation.

[0170] According to the present embodiment described above in detail, the following effects can be obtained.

[0171] According to this embodiment, when the storage battery modules 30, 40 are connected in parallel, one of the power converters 32, 42 that is not used for voltage adjustment can be used to supply power to the low-voltage load 100. Furthermore, when the storage battery modules 30, 40 are connected in series, each of the power converters 32, 42 can be used to supply power to the low-voltage load 100. By using each of the power converters 32, 42 to supply power to the low-voltage load 100, an increase in the number of power converters provided in the power conversion system 10 can be suppressed. Therefore, the power conversion system 10 can be made more compact.

[0172] When the storage battery modules 30, 40 are connected in parallel and the power required by the low-voltage load 100 (Pt) is higher than the lower limit specified value PL, one of the power converters 32, 42 that is not used for voltage regulation performs a power supply operation. This allows the low-voltage load 100 to operate appropriately. Specifically, this can prevent the low-voltage load 100 from experiencing a power failure and prevent the storage capacity of the low-voltage battery that is the power source for the low-voltage load 100 from decreasing excessively.

[0173] With the battery modules 30, 40 connected in series, when the power requirement Pt of the low-voltage load 100 is low, the number of power converters performing the power supply operation is reduced compared to when the power requirement Pt is high. This prevents unnecessary switching control from being performed when supplying power to the low-voltage load 100, and allows the low-voltage load 100 to operate appropriately.

[0174] Other Embodiments The above-described embodiments may be modified as follows.

[0175] 7, the determination unit 16a may determine that the storage battery modules 30, 40 are to be connected in series when a request to operate the high-voltage load 20 is made. On the other hand, when the determination unit 16a does not make a request to operate the high-voltage load 20, the determination unit 16a may maintain the current connection state of the storage battery modules 30, 40.

[0176] In step S10, the determination unit 16a may determine that the storage battery modules 30, 40 are to be connected in parallel when a request to operate the high-voltage load 20 is made. On the other hand, the determination unit 16a may maintain the current connection state of the storage battery modules 30, 40 when a request to operate the high-voltage load 20 is not made.

[0177] In this embodiment, the control described above with reference to FIG. 7 may be repeatedly executed by the processor of the control device 16 at a predetermined control period.

[0178] In step S10 in Fig. 7 , the determination unit 16a may determine that the storage battery modules 30, 40 are to be connected in parallel when a request for power exchange between the storage batteries 31, 41 is made. The determination unit 16a may maintain the current connection state of the storage battery modules 30, 40 when a request for power exchange between the storage batteries 31, 41 is not made. In this embodiment, too, the control described in Fig. 7 may be repeatedly executed by the processor of the control device 16 at a predetermined control period.

[0179] The power conversion system 10 may be capable of supplying power to a power supply target unit outside the vehicle. When the power supply target unit is a grid power supply, external power supply is also called V2G (Vehicle to Grid). When the power supply target unit is an electrical device in a building such as a residence, external power supply is also called V2H (Vehicle to Home).

[0180] 7 , the determination unit 16a may determine that the storage battery modules 30, 40 are to be connected in series when a request to supply power to the power supply target is made. Alternatively, in step S10, the determination unit 16a may determine that the storage battery modules 30, 40 are to be connected in parallel when power is to be supplied to the power supply target. In this embodiment, the control described in FIG. 7 may be executed by the processor of the control device 16 when the power supply target is electrically connected to the power conversion system 10.

[0181] The switching control unit 16c may output an OFF command as a drive command to the secondary-side switch of the power converter for which voltage adjustment operation is stopped, instead of outputting an ON command as a drive command. In this case, the voltage adjustment operation of the power converter is stopped with the secondary-side switch fixed OFF. As a result, the secondary-side terminal voltage of the power converter is set to a value close to 0 V. Note that in the storage battery module of the power converter for which voltage adjustment operation is stopped, a current flows due to conduction of the body diode of the secondary-side switch fixed OFF, and therefore the storage battery may be in a discharged state.

[0182] As the power converter, it is possible to use the one shown in Fig. 14 instead of the one described in Fig. 2. Fig. 14 shows an example of a first power converter 32. In Fig. 14, the configuration of the primary side of the first power converter 32 is the same as that shown in Fig. 2, and therefore detailed description thereof will be omitted.

[0183] The first power converter 32 includes two secondary-side switches Q1b, Q2b and a reactor 37. In this embodiment, each of the secondary-side switches Q1b, Q2b is a voltage-controlled semiconductor switching element, more specifically, an N-channel MOSFET. Each of the secondary-side switches Q1b, Q2b has a body diode.

[0184] A first end of the secondary winding 36b is electrically connected to the drain of the secondary switch Q1b. A second end of the secondary winding 36b is electrically connected to the drain of the secondary switch Q2b. The sources of the secondary switches Q1b and Q2b are electrically connected to the secondary negative terminal 32d and the second end of the secondary capacitor 35. A center tap provided in the secondary winding 36b is electrically connected to a first end of the reactor 37.

[0185] The power converter may be a converter other than the center-tapped isolated DC-DC converter described in Figures 2 and 14. Figure 15 shows an example of a first power converter 32. In Figure 15, the configuration of the primary side of the first power converter 32 is the same as that shown in Figure 2, and therefore a detailed description thereof will be omitted.

[0186] The first power converter 32 includes fifth to eighth switches S5 to S8. In this embodiment, voltage-controlled semiconductor switching elements, more specifically, N-channel MOSFETs, are used as the fifth to eighth switches S5 to S8. In this case, the high-potential side terminals of the fifth to eighth switches S5 to S8 are drains, and the low-potential side terminals are sources. Each of the switches S5 to S8 has a body diode.

[0187] The drain of the fifth switch S5 and the drain of the seventh switch S7 are electrically connected to the secondary-side positive terminal 32c and the first end of the secondary-side capacitor 35. 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 32d and the second end of the secondary-side capacitor 35.

[0188] A first end of the secondary winding 36b is electrically connected to the source of the seventh switch S7 and the drain of the eighth switch S8, and a second end of the secondary winding 36b is electrically connected to the source of the fifth switch S5 and the drain of the sixth switch S6.

[0189] It should be noted that the isolated DC-DC converters described with reference to FIGS. 14 and 15 may be employed in the second power converters 42, 242 and the third power converter 52 described in the above embodiments.

[0190] The power converter is not limited to those described with reference to FIGS. 2, 14, and 15, and may be a non-isolated DC-DC converter such as a resonant DC-DC converter or a buck converter.

[0191] In the second embodiment, the processes of steps S22 and S23 in Fig. 13 do not have to be performed. In this case, the power conversion system 10 does not have to include the second bypass path 402 and the second bypass switch 404.

[0192] 13. In this case, the power conversion system 10 does not need to include the first bypass path 401 and the first bypass switch 403.

[0193] In the second embodiment, as described in the modified example of the first embodiment, each configuration can be changed.

[0194] The power conversion system does not have to be configured as a storage battery module in which a storage battery, a power converter, switches, etc. are integrated into a single package.

[0195] The high-voltage load electrically connected to the power conversion system 10 is not limited to the inverter 21 and the rotating electrical machine 22, but may be a DC-DC converter, an electric heater, or the like.

[0196] The power storage unit is not limited to a storage battery, but may be, for example, a large-capacity electric double layer capacitor, or a unit including both a storage battery and an electric double layer capacitor. The power storage unit may also be a fuel cell.

[0197] 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.

[0198] 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.

[0199] The following describes characteristic configurations extracted from the above-described embodiments. [Configuration 1] A power conversion device applied to a system (10) including a plurality of power storage units (31, 41, 51), comprising: a positive electrode path (11, 63a, 64a, 65b, 65c, 263b, 264b) connecting positive electrode sides of the plurality of power storage units; a negative electrode path (12, 63b, 63c, 64b, 64c, 65a, 265b) connecting negative electrode sides of the plurality of power storage units; a parallel connection switch (62a, 62b, 62c, 62d, 262b, 362a, 362b, 362c, 362d) provided in at least one of the positive electrode path and the negative electrode path for each of the plurality of power storage units; a series connection path (60, 60a, 60b) connecting the plurality of power storage units in series; and a series connection switch (61, 61a, 61b) provided in the series connection path. a power converter (32, 42, 52, 242) provided corresponding to at least one specific power storage unit (31, 41, 51) among the plurality of power storage units, and having a primary-side terminal pair and a secondary-side terminal pair, wherein the primary-side terminal pair of the power converter is connected in parallel to the specific power storage unit, and the secondary-side terminal pair of the power converter is connected in series to the specific power storage unit, and when the series connection switch is turned off and the parallel connection switch is turned on, the plurality of power storage units are connected in parallel via the positive electrode path, the negative electrode path, and the power converter, and when the series connection switch is turned on and the parallel connection switch is turned off, the plurality of power storage units are connected in series via the series connection path, and the power converter is provided such that when the plurality of power storage units are connected in series, the secondary-side terminal pair and the plurality of power storage units are electrically isolated from each other. [Configuration 2] The power conversion device according to Configuration 1, wherein the specific storage unit is a low-potential storage unit (31) having the lowest potential in a series connection of a plurality of the storage units, and the secondary-side terminal pair of the power converter (32) is connected in series to the specific storage unit via a positive electrode side of the specific storage unit in the positive electrode path.[Configuration 3] The power conversion device according to Configuration 1 or 2, wherein the specific storage unit is a highest potential storage unit (41) on the highest potential side in a series connection of a plurality of the storage units, and the secondary-side terminal pair of the power converter (42) is connected in series to the specific storage unit via a negative electrode side of the specific storage unit in the negative electrode path. [Configuration 4] The power conversion device according to any one of Configurations 1 to 3, wherein the system includes at least three storage units, and the specific storage unit is an intermediate storage unit (51) connected between a low-potential storage unit (31) on the lowest potential side and a high-potential storage unit (41) on the highest potential side in the series connection of the storage units, and the secondary-side terminal pair of the power converter (52) is connected in series to the specific storage unit via either a negative electrode side of the specific storage unit in the negative electrode path or a positive electrode side of the specific storage unit in the positive electrode path. [Configuration 5] The power conversion device according to any one of configurations 2 to 4, wherein the plurality of power storage units are connected to a high-voltage load (20) via the positive electrode path and the negative electrode path, the secondary terminal pair of the power converter is connectable in parallel to a low-voltage load (100) that operates when supplied with a voltage lower than a voltage of the power storage units, and the parallel connection switches (362a, 362b, 362c, 362d) are provided in: a path (63b, 64a) among the positive electrode path and the negative electrode path that connects one of the secondary terminal pair of the power converter and the specific power storage unit, and a path (63a, 64b) among the positive electrode path and the negative electrode path that connects the other of the secondary terminal pair of the power converter and the high-voltage load. [Configuration 6] The power conversion device according to any one of configurations 1 to 4, comprising: a determination unit (16a) that determines whether the plurality of power storage units should be connected in parallel or in series, based on a request for the system; a connection control unit (16b) that controls the series connection switches and the parallel connection switches so as to set the plurality of power storage units in either a parallel connection state or a series connection state, based on a determination result of the determination unit; and a switching control unit (16c) that performs switching control of the power converter to adjust a voltage difference between the plurality of power storage units when the plurality of power storage units are connected in parallel.[Configuration 7] The power conversion device according to Configuration 6, wherein the specific power storage unit is at least two of the multiple power storage units, and the switching control unit selects the power converter that performs the switching control based on voltages of the multiple power storage units. [Configuration 8] The power conversion device according to Configuration 6 or 7, wherein the specific power storage unit is at least two of the multiple power storage units, secondary-side terminal pairs of each of the power converters are connectable in parallel to a load (100), and when the multiple power storage units are connected in parallel, the switching control unit performs the switching control to adjust a potential difference between the multiple power storage units in a regulation power converter that is the power converter corresponding to the specific power storage unit that has a lower voltage than the other power storage units among the multiple power storage units, and performs the switching control to supply power to the load in a power converter other than the regulation power converter among the power converters. [Configuration 9] The power conversion device according to any one of Configurations 6 to 8, wherein secondary-side terminal pairs of each of the power converters are connectable in parallel to a load (100), and the switching control unit performs the switching control to supply power to the load in a power converter of the power converters having secondary-side terminal pairs connected in parallel to the load when a plurality of the power storage units are connected in series. [Configuration 10] The power conversion device according to Configuration 9, wherein the specific power storage units are at least two of the plurality of power storage units, and the switching control unit reduces the number of power converters that perform the switching control to supply power to the load when the power required by the load is low compared to when the power required is high when the plurality of power storage units are connected in series.

[0200] 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 power conversion device applied to a system (10) having a plurality of power storage units (31, 41, 51), comprising: a positive electrode path (11, 63a, 64a, 65b, 65c, 263b, 264b) connecting the positive electrode sides of the plurality of power storage units; a negative electrode path (12, 63b, 63c, 64b, 64c, 65a, 265b) connecting the negative electrode sides of the plurality of power storage units; a parallel connection switch (62a, 62b, 62c, 62d, 262b, 362a, 362b, 362c, 362d) provided in at least one of the positive electrode path and the negative electrode path for each of the plurality of power storage units; a series connection path (60, 60a, 60b) connecting the plurality of power storage units in series; and a series connection switch (61, 61a, 61b) provided in the series connection path. a power converter (32, 42, 52, 242) provided corresponding to at least one specific power storage unit (31, 41, 51) among the plurality of power storage units, and having a primary-side terminal pair and a secondary-side terminal pair, wherein the primary-side terminal pair of the power converter is connected in parallel to the specific power storage unit, and the secondary-side terminal pair of the power converter is connected in series to the specific power storage unit, and when the series connection switch is turned off and the parallel connection switch is turned on, the plurality of power storage units are connected in parallel via the positive electrode path, the negative electrode path, and the power converter, and when the series connection switch is turned on and the parallel connection switch is turned off, the plurality of power storage units are connected in series via the series connection path, and the power converter is provided such that when the plurality of power storage units are connected in series, the secondary-side terminal pair and the plurality of power storage units are electrically isolated from each other.

2. The power conversion device according to claim 1, wherein the specific storage unit is a low-potential storage unit (31) having the lowest potential in a series connection of a plurality of the storage units, and the secondary-side terminal pair of the power converter (32) is connected in series to the specific storage unit via the positive electrode side of the specific storage unit in the positive electrode path.

3. The power conversion device according to claim 1, wherein the specific storage unit is a high-potential storage unit (41) having the highest potential in a series connection of a plurality of the storage units, and the secondary-side terminal pair of the power converter (42) is connected in series to the specific storage unit via the negative electrode side of the specific storage unit in the negative electrode path.

4. The power conversion device according to claim 1, wherein the system includes at least three of the storage units, the specific storage unit being an intermediate storage unit (51) connected between a low-potential storage unit (31) on the lowest potential side and a high-potential storage unit (41) on the highest potential side in a series connection of the storage units, and the secondary terminal pair of the power converter (52) is connected in series to the specific storage unit via either the negative electrode side of the specific storage unit in the negative electrode path or the positive electrode side of the specific storage unit in the positive electrode path.

5. The power conversion device according to any one of claims 2 to 4, wherein the plurality of power storage units are connected to a high-voltage load (20) via the positive electrode path and the negative electrode path, the secondary terminal pair of the power converter is connectable in parallel to a low-voltage load (100) that operates when supplied with a voltage lower than that of the power storage units, and the parallel connection switches (362a, 362b, 362c, 362d) are provided in: a path (63b, 64a) of the positive electrode path and the negative electrode path that connects one of the secondary terminal pair of the power converter and the specific power storage unit; and a path (63a, 64b) of the positive electrode path and the negative electrode path that connects the other of the secondary terminal pair of the power converter and the high-voltage load.

6. The power conversion device according to any one of claims 1 to 4, comprising: a determination unit (16a) that determines whether the plurality of power storage units should be connected in parallel or in series based on a request for the system; a connection control unit (16b) that controls the series connection switch and the parallel connection switch so as to set the plurality of power storage units in either a parallel connection state or a series connection state based on a determination result of the determination unit; and a switching control unit (16c) that performs switching control of the power converter to adjust a voltage difference between the plurality of power storage units when the plurality of power storage units are connected in parallel.

7. The power conversion device according to claim 6, wherein the specific storage units are at least two of the plurality of storage units, and the switching control unit selects the power converter that performs the switching control based on the voltages of the plurality of storage units.

8. The power conversion device according to claim 6, wherein the specific storage unit is at least two of the multiple storage units, the secondary-side terminal pairs of each of the power converters are connectable in parallel to a load (100), and when the multiple storage units are connected in parallel, the switching control unit performs the switching control to adjust the potential difference between the multiple storage units in an adjustment power converter that is the power converter corresponding to the specific storage unit having a lower voltage than the other storage units among the multiple storage units, and performs the switching control to supply power to the load in a power converter other than the adjustment power converter among the power converters.

9. The power conversion device according to claim 6, wherein the secondary terminal pairs of each of the power converters are connectable in parallel to a load (100), and when a plurality of the power storage units are connected in series, the switching control unit performs the switching control for supplying power to the load in a power converter of each of the power converters in which the secondary terminal pairs are connected in parallel to the load.

10. The power conversion device according to claim 9, wherein the specific storage unit is at least two of the plurality of storage units, and the switching control unit reduces the number of power converters that perform the switching control for supplying power to the load when the required power of the load is low compared to when the required power is high in a state where the plurality of storage units are connected in series.

11. A control program for a power conversion device applied to a system (10) having a plurality of power storage units (31, 41, 51), wherein the power conversion device comprises: a positive electrode path (11, 63a, 64a, 65b, 65c, 263b, 264b) connecting the positive electrode sides of the plurality of power storage units; a negative electrode path (12, 63b, 63c, 64b, 64c, 65a, 265b) connecting the negative electrode sides of the plurality of power storage units; a parallel connection switch (62a, 62b, 62c, 62d, 262b, 362a, 362b, 362c, 362d) provided in at least one of the positive electrode path and the negative electrode path for each of the plurality of power storage units; and a series connection path (60, 60a, 60b) connecting the plurality of power storage units in series. a series connection switch (61, 61a, 61b) provided in the series connection path; and a power converter (32, 42, 52, 53) provided in correspondence with at least one specific power storage unit (31, 41, 51) among the plurality of power storage units, the power converter having a primary side terminal pair and a secondary side terminal pair.242), wherein the primary side terminal pair of the power converter is connected in parallel to the specific power storage unit, the secondary side terminal pair of the power converter is connected in series to the specific power storage unit, a plurality of the power storage units are connected in parallel via the positive electrode path, the negative electrode path and the power converter when the series connection switch is turned off and the parallel connection switch is turned on, a plurality of the power storage units are connected in series via the series connection path when the series connection switch is turned on and the parallel connection switch is turned off, and the power converter is provided such that when the plurality of the power storage units are connected in series, the secondary side terminal pair and the plurality of the power storage units are electrically isolated, and a computer (16) is provided with a determination process for determining whether the plurality of the power storage units should be connected in parallel or in series, based on a request to the system; a connection control process for controlling the series connection switch and the parallel connection switch so as to set the plurality of power storage units to either a parallel-connected state or a series-connected state based on a determination result of the determination process; and a switching control process for performing switching control of the power converter to adjust a voltage difference between the plurality of power storage units when the plurality of power storage units are connected in parallel.

12. A control method for a power conversion device applied to a system (10) having a plurality of power storage units (31, 41, 51), the power conversion device comprising: a positive electrode path (11, 63a, 64a, 65b, 65c, 263b, 264b) connecting the positive electrode sides of the plurality of power storage units; a negative electrode path (12, 63b, 63c, 64b, 64c, 65a, 265b) connecting the negative electrode sides of the plurality of power storage units; a parallel connection switch (62a, 62b, 62c, 62d, 262b, 362a, 362b, 362c, 362d) provided in at least one of the positive electrode path and the negative electrode path for each of the plurality of power storage units; and a series connection path (60, 60a, 60b) connecting the plurality of power storage units in series. a series connection switch (61, 61a, 61b) provided in the series connection path; and a power converter (32, 42, 52, 53) provided in correspondence with at least one specific power storage unit (31, 41, 51) among the plurality of power storage units, the power converter having a primary side terminal pair and a secondary side terminal pair.242), wherein the primary side terminal pair of the power converter is connected in parallel to the specific power storage unit, and the secondary side terminal pair of the power converter is connected in series to the specific power storage unit, and when the series connection switch is turned off and the parallel connection switch is turned on, a plurality of the power storage units are connected in parallel via the positive electrode path, the negative electrode path and the power converter, and when the series connection switch is turned on and the parallel connection switch is turned off, a plurality of the power storage units are connected in series via the series connection path, and the power converter is provided such that when the plurality of power storage units are connected in series, the secondary side terminal pair and the plurality of power storage units are electrically isolated, based on a request for the system, a determination step of determining whether the plurality of power storage units should be connected in a parallel connection state or a series connection state, and a connection control step of controlling the series connection switch and the parallel connection switch based on a determination result of the determination step to set the plurality of power storage units to either a state in which the plurality of power storage units are connected in parallel or a state in which the plurality of power storage units are connected in series. A control method for a power conversion device, comprising: a switching control step of performing switching control of the power converter to adjust a voltage difference between the plurality of power storage units when the plurality of power storage units are connected in parallel.

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