Power converter, power converter control device, program, and power converter control method

Abstract

A power converter (40, 70, 100) applied to a system (10) provided with a power storage unit (31, 61, 91) comprises: a primary-side circuit (51) having a primary-side terminal pair (41, 42, 71, 72, 101, 102) connected in parallel to the power storage unit; and a secondary-side circuit (52, 152, 252). The secondary-side circuit has a secondary-side terminal pair (43, 44, 73, 74, 103, 104) connected in series to the power storage unit, and is capable of transmitting power to and from the primary-side circuit. The secondary-side circuit has pairs of switch units (QH1, QL1, QH2, QL2, RH1, RL1, RH2, RL2, T1a, T1b, T2a, T2b, UH1, UL1, UH2, UL2, UH3, UU3, UH4, UL4). The pairs of switch units are each connected such that blocking directions thereof, in which the current flow is blocked if the switch units are turned off, are stipulated, and such that the blocking directions are mutually opposite directions.

Description

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

[0001] This application is based on Japanese Application No. 2024-120917, filed on July 26, 2024, the contents of which are incorporated herein by reference.

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

[0003] Conventionally, a power converter applied to a system including a power storage unit has been known. The power converter has a primary circuit and a secondary circuit capable of transmitting power to each other. A primary terminal pair of the primary circuit is connected in parallel to the power storage unit. A secondary terminal pair of the secondary circuit is connected in series to the power storage unit. In this system, for example, a voltage required by the system that is insufficient in the output voltage of the power storage unit is output from the secondary terminal pair of the power converter. This reduces the rated voltage of the power converter, thereby achieving a smaller capacity of the power converter. An example of such a technology is disclosed in Patent Document 1.

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

[0005] The narrow range of voltages that can be output from the secondary terminal pair of the power converter may limit the capacity of the power converter, which may result in an increase in the system size.

[0006] An object of the present disclosure is to provide a power converter, a control device for a power converter, a program, and a control method for a power converter that enable the miniaturization of the system.

[0007] The present disclosure relates to a power converter applied to a system including a power storage unit, comprising: a primary circuit having a primary terminal pair connected in parallel to the power storage unit; and a secondary circuit having a secondary terminal pair connected in series to the power storage unit and capable of transmitting power between the primary circuit and the secondary circuit, wherein the secondary circuit has a pair of switch units, each of which has a predetermined blocking direction in which current flow is blocked when turned off, and which is connected so that the blocking directions are opposite to each other.

[0008] In the above-described system, it is conceivable that the voltage across the secondary-side terminal pair in the secondary-side circuit is a positive voltage and adds a voltage to the output voltage of the power storage unit, or that the voltage across the secondary-side terminal pair is a negative voltage and subtracts a voltage from the output voltage of the power storage unit. In this case, it is conceivable to selectively output either a positive voltage or a negative voltage from the secondary-side terminal pair of the secondary-side circuit, thereby expanding the output voltage range of the power converter. In this regard, the switch used in the secondary-side circuit has a predetermined blocking direction in which current flow is blocked when turned off. If the blocking direction in the secondary-side circuit is constant, only one of the positive voltage and the negative voltage is output from the secondary-side terminal pair, the voltage having a polarity corresponding to the blocking direction and a current-permitting direction in which current flow in the opposite direction to the blocking direction is permitted regardless of whether the switch is on or off. In this case, there is a concern that it may be impossible to selectively output either a positive voltage or a negative voltage from the secondary-side terminal pair of the secondary-side circuit.

[0009] Therefore, in the present disclosure, the secondary circuit has a pair of switch units. The pair of switch units are connected so that their blocking directions are opposite to each other. In this case, it is possible to control the pair of switch units so that the blocking direction and the current-permitting direction of the current flowing through the pair of switch units are interchanged. This makes it possible to select and output either a positive voltage or a negative voltage from the pair of secondary terminals, thereby expanding the range of voltages that can be output from the pair of secondary terminals compared to a comparative example in which the secondary circuit does not have a pair of switch units. This prevents limitations on reducing the capacity of the power converter due to the narrow range of voltages that the power converter can output. As a result, it is possible to achieve a more compact system.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a configuration diagram of a power conversion system according to a first embodiment, Fig. 2 is a diagram showing an example of a power converter, Fig. 3 is a diagram explaining first to fourth quadrant operations, Fig. 4 is a diagram explaining a control method for a bidirectional switch, Fig. 5 is a diagram explaining a control method for a bidirectional switch, Fig. 6 is a diagram showing a path of a current flowing through the power conversion system during first quadrant operation, Fig. 7 is a diagram showing an example of first quadrant operation, Fig. 8 is a diagram showing an example of first quadrant operation, and Fig. 9 is a diagram showing a path of a current flowing through the power conversion system during second quadrant operation. 10 is a diagram showing an example of second quadrant operation, FIG. 11 is a diagram showing an example of second quadrant operation, FIG. 12 is a diagram showing an example of second quadrant operation, FIG. 13 is a diagram showing a path of current flowing in the power conversion system during third quadrant operation, FIG. 14 is a diagram showing an example of third quadrant operation, FIG. 15 is a diagram showing an example of third quadrant operation, FIG. 16 is a diagram showing a path of current flowing in the power conversion system during fourth quadrant operation, and FIG. 17 is a diagram showing an example of fourth quadrant operation. 18 is a diagram showing an example of a fourth-quadrant operation, FIG. 19 is a diagram showing an example of a fourth-quadrant operation, FIG. 20 is a flowchart showing a control procedure performed by a control device, FIG. 21 is a configuration diagram of a power conversion system according to a second embodiment, FIG. 22 is a diagram showing an example of an operation performed by the power conversion system 10, FIG. 23 is a diagram showing an example of an operation performed by the power conversion system 10, FIG. 24 is a diagram showing an example of an operation performed by the power conversion system 10, and FIG. 25 is a diagram showing an example of an operation performed by the power conversion system 10. 26 is a diagram showing an example of an operation performed by the power conversion system 10, FIG. 27 is a diagram showing an example of an operation performed by the power conversion system 10, FIG. 28 is a diagram showing an example of an operation performed by the power conversion system 10, FIG. 29 is a diagram showing an example of an operation performed by the power conversion system 10, FIG. 30 is a diagram showing an example of an operation performed by the power conversion system 10, FIG. 31 is a diagram showing an example of an operation performed by the power conversion system 10, FIG. 32 is a diagram showing an example of an operation performed by the power conversion system 10, and FIG. 33 is a diagram showing an example of an operation performed by the power conversion system 10.34 is a configuration diagram of a power conversion system according to a modification of the second embodiment, FIG. 34 is a flowchart showing the processing procedure of control performed by a control device, FIG. 35 is a flowchart showing the processing procedure of control performed by a control device, FIG. 36 is a flowchart showing the processing procedure of control performed by a control device, FIG. 37 is a flowchart showing the processing procedure of control performed by a control device, FIG. 38 is a diagram showing an example of a power converter, FIG. 39 is a diagram showing an example of a power converter, FIG. 40 is a diagram showing an example of a power converter, and FIG. 41 is a configuration diagram of a power conversion system according to another embodiment.

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

[0012] A first embodiment of a 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.

[0013] FIG. 1 shows a configuration diagram of a power conversion system 10 mounted on a vehicle. The power conversion system 10 includes a storage battery module 30. The storage battery module 30 includes a storage battery 31 (corresponding to a "power storage unit"). The storage battery 31 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, rechargeable secondary batteries such as lithium-ion batteries.

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

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

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

[0017] The storage battery module 30 includes a power converter 40. The power converter 40 is electrically connected to the storage battery 31 and the load 21. Specifically, the power converter 40 includes a primary-side terminal pair consisting of a primary-side positive terminal 41 and a primary-side negative terminal 42, and a secondary-side terminal pair consisting of a secondary-side positive terminal 43 and a secondary-side negative terminal 44. The primary-side positive terminal 41 is electrically connected to the positive side of the storage battery 31. The primary-side negative terminal 42 and the negative side of the storage battery 31 are electrically connected to the inverter 22 via the low-potential-side path 14. In other words, the primary-side terminal pair of the power converter 40 is electrically connected in parallel to the storage battery 31. In this case, the voltage of the storage battery 31 is applied to the primary-side terminal pair of the power converter 40.

[0018] The secondary negative terminal 44 is electrically connected to the positive electrode side of the storage battery 31. The secondary positive terminal 43 of the power converter 40 is electrically connected to the inverter 22 via the high potential side path 13. In other words, the secondary terminal pair of the power converter 40 is electrically connected in series to the storage battery 31 on the positive electrode side of the storage battery 31.

[0019] The power conversion system 10 includes a battery monitoring device 32. The battery monitoring device 32 is provided corresponding to the storage battery 31. For example, the battery monitoring device 32 detects the terminal voltage, current, internal resistance, SOC, etc. of each battery cell that constitutes the storage battery 31, and monitors the state of the storage battery 31. The detected values ​​detected by the battery monitoring device 32 are input to the control device 16 provided in the power conversion system 10.

[0020] The power conversion system 10 includes a voltage sensor 45 and a current sensor 46. The voltage sensor 45 detects a secondary-side terminal voltage Vor applied to a pair of secondary-side terminals of the power converter 40. The polarity of the secondary-side terminal voltage Vor is positive when the potential of the secondary-side positive terminal 43 is higher than the potential of the secondary-side negative terminal 44, and negative when the potential of the secondary-side negative terminal 44 is higher than the potential of the secondary-side positive terminal 43. In other words, the polarity of the secondary-side terminal voltage Vor is positive when it is the same as the output voltage of the storage battery 31, and negative when it is different from the output voltage of the storage battery 31. The current sensor 46 detects a secondary-side current Ior flowing on the secondary side of the power converter 40. The sign of the secondary-side current Ior is positive when a discharging current from the storage battery 31 flows through the secondary-side circuit 52, and negative when a charging current from the storage battery 31 flows through the secondary-side circuit 52. The detected values ​​of the sensors 45 and 46 are input to the control device 16 .

[0021] The control device 16 is an electronic control unit (ECU) that performs various controls of the power conversion system 10 and includes a processor and a storage unit as hardware. In the control device 16, the processor and storage unit are connected to each other via a communication bus. In the power conversion system 10, each on-board device can be controlled by its corresponding ECU. However, for convenience, multiple ECUs are shown as a single control device 16 in FIG. 1 .

[0022] 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 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 20, 34 to 37, which will be described later.

[0023] 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.

[0024] In this embodiment, the control device 16 performs switching control of the power converter 40 based on various input detection values. For example, in the switching control, the control device 16 controls the secondary-side terminal voltage Vor applied to the secondary-side terminal pair.

[0025] The secondary-side terminal voltage Vor of the power converter 40 is the difference voltage between the voltage between each path 13, 14 (specifically, the voltage supplied to the inverter 22) and the voltage Vbat of the storage battery 31. The secondary-side terminal voltage Vor of the power converter 40 is a voltage lower than the rated voltage (e.g., 400 V) of the corresponding storage battery 31. Therefore, the secondary-side rated voltage on the secondary side of the power converter 40 is set lower than the rated voltage of the storage battery 31, e.g., 16 V. This allows the capacity of the power converter 40 to be reduced.

[0026] However, there is a possibility that the capacity of the power converter 40 may be limited due to the narrow range of voltage that can be output from the secondary terminal pair of the power converter 40. In this case, there is a concern that the power conversion system 10 may become large in size.

[0027] Therefore, in this embodiment, the power converter 40 is configured to be able to expand the voltage range that can be output at the secondary-side terminal pairs. Fig. 2 shows an example of the power converter 40. The power converter 40 is an isolated DC-DC converter. The power converter 40 includes a transformer 50, a primary-side circuit 51, a secondary-side circuit 52, a primary-side capacitor 53, and a secondary-side capacitor 54.

[0028] The transformer 50 includes a primary winding 50a and a secondary winding 50b. The primary winding 50a and the secondary winding 50b are wound around a common core, so that the primary winding 50a and the secondary winding 50b are magnetically coupled by the common core.

[0029] The primary circuit 51 is a full-bridge circuit and includes a first conversion switch S1, a second conversion switch S2, a third conversion switch S3, and a fourth conversion switch S4 as primary-side switches. In this embodiment, a voltage-controlled semiconductor switching element, more specifically, an N-channel MOSFET, is used as each of the conversion switches S1 to S4. In this case, the first main terminal of each of the conversion switches S1 to S4 is the drain, and the second main terminal is the source. The first, second, third, and fourth conversion switches S1, S2, S3, and S4 each have body diodes D1, D2, D3, and D4.

[0030] The drain of the first conversion switch S1 and the drain of the third conversion switch S3 are electrically connected to the primary-side positive terminal 41 and the first end of the primary-side capacitor 53. The source of the first conversion switch S1 is electrically connected to the drain of the second conversion switch S2. The source of the third conversion switch S3 is electrically connected to the drain of the fourth conversion switch S4. The source of the second conversion switch S2 and the source of the fourth conversion switch S4 are electrically connected to the primary-side negative terminal 42 and the second end of the primary-side capacitor 53.

[0031] A first end of the primary winding 50a is electrically connected to the source of the first conversion switch S1 and the drain of the second conversion switch S2. A second end of the primary winding 50a is electrically connected to the source of the third conversion switch S3 and the drain of the fourth conversion switch S4. The first to fourth conversion switches S1 to S4 are controlled by the control device 16.

[0032] The secondary circuit 52 is a center-tap circuit and includes a first bidirectional switch Q1, a second bidirectional switch Q2, and a reactor 55. The secondary winding 50b is provided with a center tap. The center tap of the secondary winding 50b is electrically connected to a first end of the reactor 55. A second end of the reactor 55 is electrically connected to the secondary positive terminal 43 and a first end of the secondary capacitor 54. The first end of the secondary winding 50b is electrically connected to the secondary negative terminal 44 and the second end of the secondary capacitor 54 via the first bidirectional switch Q1. The second end of the secondary winding 50b is electrically connected to the secondary negative terminal 44 and the second end of the secondary capacitor 54 via the second bidirectional switch Q2.

[0033] Here, in the power converter 40, the secondary-side terminal voltage Vor may be a positive voltage (hereinafter referred to as a positive voltage) to add a voltage to the output voltage of the storage battery 31, or a negative voltage (hereinafter referred to as a negative voltage) to subtract a voltage from the output voltage of the storage battery 31. In this case, it is conceivable to selectively output either a positive voltage or a negative voltage from the secondary-side terminal pair of the power converter 40, thereby expanding the output voltage range of the power converter 40. In this regard, the switch used in the secondary-side circuit 52 has a blocking direction in which current flow is blocked when turned off and a current-permitting direction in which current flow in the opposite direction to the blocking direction is permitted regardless of whether the switch is on or off. Unlike the present embodiment, if the blocking direction and current-permitting direction in the secondary-side circuit 52 are constant, only one of the positive voltage and the negative voltage, which has a polarity corresponding to the blocking direction and current-permitting direction, is output from the secondary-side terminal pair. In this case, there is a concern that it may be impossible to selectively output either a positive voltage or a negative voltage from the secondary-side terminal pair of the secondary-side circuit 52.

[0034] Each of the bidirectional switches Q1 and Q2 is configured with a pair of switch units. Specifically, the first bidirectional switch Q1 is configured with a pair of switch units, a first positive switch QH1 and a first negative switch QL1. The second bidirectional switch Q2 is configured with a pair of switch units, a second positive switch QH2 and a second negative switch QL2. In this embodiment, voltage-controlled semiconductor switching elements, more specifically, N-channel MOSFETs, are used as the switches QH1, QL1, QH2, and QL2. The switches QH1, QL1, QH2, and QL2 each have a body diode DH1, DL1, DH2, and DL2. In this case, the reverse direction of each of the body diodes DH1, DL1, DH2, and DL2 corresponds to the blocking direction, and the forward direction corresponds to the conducting direction.

[0035] The first positive switch QH1 and the first negative switch QL1 are connected in series so that their blocking directions are opposite to each other. The second positive switch QH2 and the second negative switch QL2 are connected in series so that their blocking directions are opposite to each other. In this embodiment, the sources of the first positive switch QH1 and the first negative switch QL1 are electrically connected to each other. The sources of the second positive switch QH2 and the second negative switch QL2 are electrically connected to each other.

[0036] The drain of the first positive switch QH1 is electrically connected to a first end of the secondary winding 50b. The drain of the second positive switch QH2 is electrically connected to a second end of the secondary winding 50b. The drains of the first negative switch QL1 and the second negative switch QL2 are electrically connected to the secondary negative terminal 44 and the second end of the secondary capacitor 54.

[0037] 1 are arranged in the power converter 40 as shown in Fig. 2. The voltage sensor 45 detects the voltage of the secondary-side capacitor 54 as a secondary-side terminal voltage Vor. The current sensor 46 detects the current flowing between the second end of the reactor 55 and the first end of the secondary-side capacitor 54 as a secondary-side current Ior.

[0038] In this embodiment, the secondary circuit 52 includes first and second bidirectional switches Q1 and Q2. The switches QH1, QL1, QH2, and QL2 constituting each bidirectional switch Q1 and Q2 are connected so that their blocking directions are opposite to each other. In this case, the switches QH1, QL1, QH2, and QL2 can be controlled so that the blocking direction and the conducting direction of the current flowing through each bidirectional switch Q1 and Q2 are reversed. This allows the secondary terminal pair to selectively output either a positive voltage or a negative voltage. This expands the range of voltages that can be output from the secondary terminal pair compared to a comparative example in which the secondary circuit does not include the bidirectional switches Q1 and Q2. This prevents limitations on the capacity of the power converter 40 due to the narrow output voltage range of the power converter 40. As a result, the power conversion system 10 can be made more compact.

[0039] The switching control performed by the control device 16 will be described in detail below.

[0040] The control device 16 sets a secondary-side command voltage Vo* and a secondary-side command current Io* based on the input secondary-side terminal voltage Vor, secondary-side current Ior, voltage Vbat of the storage battery 31, and current Ibat of the storage battery 31. The secondary-side command voltage Vo* is a command value for the secondary-side terminal voltage Vor of the power converter 40. The secondary-side command current Io* is a command value for the secondary-side current Ior of the power converter 40.

[0041] In controlling the switching of the power converter 40, the control device 16 performs one of first to fourth quadrant operations determined according to the secondary-side terminal voltage Vor and the charge / discharge current of the storage battery 31. As shown in FIG. 3 , the first quadrant operation is an operation in which the storage battery 31 is discharged while the secondary-side terminal voltage Vor is a positive voltage. The second quadrant operation is an operation in which the storage battery 31 is discharged while the secondary-side terminal voltage Vor is a negative voltage. The third quadrant operation is an operation in which the storage battery 31 is charged while the secondary-side terminal voltage Vor is a negative voltage. The fourth quadrant operation is an operation in which the storage battery 31 is charged while the secondary-side terminal voltage Vor is a positive voltage.

[0042] The control device 16 includes a setting unit 16a and a control unit 16b as components for performing first to fourth quadrant operations. The setting unit 16a sets a secondary command voltage Vo* and a secondary command current Io* based on the input secondary terminal voltage Vor, secondary current Ior, voltage Vbat of the storage battery 31, and current Ibat of the storage battery 31. The secondary command voltage Vo* is a command value for the secondary terminal voltage Vor of the power converter 40. The secondary command current Io* is a command value for the current flowing on the secondary side of the power converter 40.

[0043] The setting unit 16a sets one of the positive-side switches QH1, QH2 and the negative-side switches QL1, QL2 as a fixed-on switch and sets the other as a control switch based on the polarity of the set secondary-side command voltage Vo*. The fixed-on switch is a switch that is fixed to on. The control switch is a switch that performs switching control (specifically, PWM control).

[0044] The setting unit 16a determines the polarity of the set secondary-side command voltage Vo*. As shown in FIG. 4 , if the setting unit 16a determines that the set secondary-side command voltage Vo* is a positive voltage, it sets the negative-side switches QL1 and QL2 as fixed-on switches and sets the positive-side switches QH1 and QH2 as control switches. In this case, the blocking direction of the bidirectional switches Q1 and Q2 is set to the charging direction of the storage battery 31. The charging direction is the direction in which a charging current for the storage battery 31 flows in the secondary-side circuit 52. The conducting direction of the bidirectional switches Q1 and Q2 is set to the discharging direction of the storage battery 31. The discharging direction is the direction in which a discharging current for the storage battery 31 flows in the secondary-side circuit 52.

[0045] On the other hand, as shown in Fig. 5, when the setting unit 16a determines that the set secondary-side command voltage Vo1* is a negative voltage, it sets the positive-side switches QH1, QH2 as fixed-on switches and sets the negative-side switches QL1, QL2 as control switches. In this case, the blocking direction of the bidirectional switches Q1, Q2 is set to the discharging direction of the storage battery 31. The conducting direction of the bidirectional switches Q1, Q2 is set to the charging direction of the storage battery 31.

[0046] The control unit 16b performs switching control of the control switch and the conversion switches S1 to S4 so as to transfer power from either the primary side circuit 51 or the secondary side circuit 52 to the other. Specifically, when the setting unit 16a determines that the secondary side command voltage Vo* of the power converter 40 is a positive voltage, the control unit 16b performs either a first quadrant operation in which power is transferred from the primary side circuit 51 to the secondary side circuit 52, or a fourth quadrant operation in which power is transferred from the secondary side circuit 52 to the primary side circuit 51. When the setting unit 16a determines that the secondary side command voltage Vo* of the power converter 40 is a negative voltage, the control unit 16b performs either a second quadrant operation in which power is transferred from the secondary side circuit 52 to the primary side circuit 51, or a third quadrant operation in which power is transferred from the primary side circuit 51 to the secondary side circuit 52. The first to fourth quadrant operations will be described in order below.

[0047] 6 shows a current path when first-quadrant operation is performed in the power converter 40. When first-quadrant operation is performed, the control unit 16b controls the switching of the primary circuit 51 and the secondary circuit 52 so as to transmit power P from the primary circuit 51 to the secondary circuit 52 while the negative switches QL1 and QL2 are fixed on. In this case, a current flows through the secondary circuit 52 so as to discharge the storage battery 31. Specifically, a battery current Ia is output from the positive side of the storage battery 31 and flows to the load 21 via the secondary circuit 52. A converter current Ib is output from the positive side of the storage battery 31 and input to the primary circuit 51.

[0048] In this embodiment, when the power converter 40 performs first-quadrant operation, the control unit 16b controls the switching of the primary circuit 51 and the secondary circuit 52 so as to step down the voltage input to the primary circuit 51 and apply the stepped-down voltage to the secondary terminal pair. For example, the control unit 16b alternately performs the operations shown in FIGS. 7 and 8 as first-quadrant operation. Note that, hereinafter, when the potential of the first terminal of the primary winding 50a and the secondary winding 50b is higher than the second terminal, the polarity of the voltage of each winding 50a, 50b is positive. When the potential of the second terminal of each winding 50a, 50b is higher than the first terminal, the polarity of the voltage of each winding 50a, 50b is negative.

[0049] As shown in Fig. 7, the control unit 16b turns on the first and fourth conversion switches S1 and S4 and the first and second negative switches QL1 and QL2, and turns off the second and third conversion switches S2 and S3 and the first and second positive switches QH1 and QH2. In this case, in the primary circuit 51, the converter current Ib flows through the primary positive terminal 41, the first conversion switch S1, the primary winding 50a, the fourth conversion switch S4, and the primary negative terminal 42 in this order. As a result, a positive voltage is applied to the primary winding 50a. A positive voltage is induced in the secondary winding 50b.

[0050] 7, in the secondary circuit 52, the battery current Ia flows in the following order: the secondary negative terminal 44, the second negative switch QL2, the body diode DH2 of the second positive switch QH2, the secondary winding 50b, the reactor 55, and the secondary positive terminal 43. As a result, a positive voltage is applied to the secondary capacitor 54.

[0051] As shown in Fig. 8, the control unit 16b turns on the second and third conversion switches S2 and S3 and the first and second negative switches QL1 and QL2, and turns off the first and fourth conversion switches S1 and S4 and the first and second positive switches QH1 and QH2. In this case, in the primary circuit 51, the converter current Ib flows through the primary positive terminal 41, the third conversion switch S3, the primary winding 50a, the second conversion switch S2, and the primary negative terminal 42 in this order. As a result, a negative voltage is applied to the primary winding 50a. A negative voltage is induced in the secondary winding 50b.

[0052] 8, in the secondary circuit 52, the battery current Ia flows in the following order: the secondary negative terminal 44, the first negative switch QL1, the body diode DH1 of the first positive switch QH1, the secondary winding 50b, the reactor 55, and the secondary positive terminal 43. As a result, a positive voltage is applied to the secondary capacitor 54.

[0053] In the first quadrant operation described above, power P is transmitted from the primary circuit 51 to the secondary circuit 52 while the charging direction of the storage battery 31 is blocked in the secondary circuit 52. In this case, current flowing in the charging direction in the secondary circuit 52 is blocked. This causes a positive voltage to be applied to the secondary capacitor 54, and the storage battery 31 is discharged. Therefore, it is possible to realize an operation in which the storage battery 31 is discharged while the secondary terminal voltage Vor of the power converter 40 is kept positive.

[0054] 7, a positive voltage is induced in the secondary winding 50b, but the first positive switch QH1 and the body diode DH1, which are turned off, prevent current from flowing from the first end of the secondary winding 50b to the secondary negative terminal 44. Also, during the operation shown in Fig. 8, a negative voltage is induced in the secondary winding 50b, but the second positive switch QH2 and the body diode DH2, which are turned off, prevent current from flowing from the second end of the secondary winding 50b to the secondary negative terminal 44. Therefore, as described with reference to Figs. 6 to 8, the battery current Ia and the converter current Ib flow in the discharge direction of the storage battery 31, and a positive voltage is applied to the secondary capacitor 54.

[0055] Unlike the present embodiment, in a comparative example in which the secondary circuit 52 includes only the negative switches QL1 and QL2 among the switches QH1, QH2, QL1, and QL2, a positive voltage cannot be applied to the secondary capacitor 54. This is because, in the secondary circuit 52, if the blocking direction is the discharging direction of the storage battery 31 and the current-carrying direction is fixed to the charging direction of the storage battery 31, the discharge current of the secondary capacitor 54 to which a positive voltage is applied cannot be blocked.

[0056] 9 shows a current path when second-quadrant operation is performed in the power converter 40. When second-quadrant operation is performed, the control unit 16b controls the switching of the primary-side circuit 51 and the secondary-side circuit 52 so that power P is transmitted from the secondary-side circuit 52 to the primary-side circuit 51 while the positive-side switches QH1 and QH2 are fixed on. In this case, a current flows through the secondary-side circuit 52 so that the storage battery 31 is discharged. Specifically, a battery current Ia is output from the positive side of the storage battery 31 and input to the secondary-side circuit 52. A converter current Ib is output from the primary-side circuit 51 and input to the secondary-side circuit 52. The battery current Ia and converter current Ib input to the secondary-side circuit 52 flow to the positive side of the load 21.

[0057] In the present embodiment, when the control unit 16b performs second-quadrant operation in the power converter 40, the control unit 16b controls the switching of the primary-side circuit 51 and the secondary-side circuit 52 so as to boost the voltage input to the secondary-side circuit 52 and apply the boosted voltage to the primary-side terminal pair. For example, the control unit 16b performs the operations shown in Figs. 10, 11, and 12 as second-quadrant operation.

[0058] 10 , the control unit 16b turns off the first to fourth conversion switches S1 to S4 and turns on the first and second positive switches QH1 and QH2 and the first and second negative switches QL1 and QL2. In this case, the battery current Ia flows through two current paths in the secondary circuit 52 so that a negative voltage is applied to the secondary capacitor 54. In the first current path, the current flows through the secondary negative terminal 44, the first negative switch QL1, the first positive switch QH1, the secondary winding 50b, the reactor 55, and the secondary positive terminal 43 in this order. In the second current path, the current flows through the secondary negative terminal 44, the second negative switch QL2, the second positive switch QH2, the secondary winding 50b, the reactor 55, and the secondary positive terminal 43 in this order. As a result, magnetic energy is stored in the reactor 55. During the operation shown in FIG. 10, power is not basically transmitted from the secondary circuit 52 to the primary circuit 51, and no current flows through the primary circuit 51.

[0059] As shown in Fig. 11, the control unit 16b turns off the first to fourth conversion switches S1 to S4 and the first negative switch QL1, and turns on the first and second positive switches QH1 and QH2 and the second negative switch QL2. In this case, in the secondary circuit 52, the battery current Ia and the converter current Ib flow in the following order: the secondary negative terminal 44, the second negative switch QL2, the second positive switch QH2, the secondary winding 50b, the reactor 55, and the secondary positive terminal 43. As a result, a negative voltage is applied to the secondary winding 50b. A negative voltage is induced in the primary winding 50a.

[0060] 11 , in the primary circuit 51, a converter current Ib flows in the following order: the primary negative terminal 42, the body diode D2 of the second conversion switch S2, the primary winding 50a, the body diode D3 of the third conversion switch S3, and the primary positive terminal 41. The converter current Ib output from the primary circuit 51 is input to the secondary circuit 52. During the operation of FIG. 11 , a negative voltage is applied to the secondary capacitor 54.

[0061] 12, the control unit 16b turns off the first to fourth conversion switches S1 to S4 and the second negative switch QL2, and turns on the first and second positive switches QH1 and QH2 and the first negative switch QL1. In this case, in the secondary circuit 52, the battery current Ia and the converter current Ib flow through a path including the secondary negative terminal 44, the first negative switch QL1, the first positive switch QH1, the secondary winding 50b, the reactor 55, and the secondary positive terminal 43. As a result, a positive voltage is applied to the secondary winding 50b. A positive voltage is induced in the primary winding 50a.

[0062] 12, in the primary circuit 51, a converter current Ib flows through a path including the primary negative terminal 42, the body diode D4 of the fourth conversion switch S4, the primary winding 50a, the body diode D1 of the first conversion switch S1, and the primary positive terminal 41. The converter current Ib output from the primary circuit 51 is input to the secondary circuit 52. During the operation shown in FIG. 12, a negative voltage is applied to the secondary capacitor 54.

[0063] The control unit 16b alternately repeats the operations shown in FIGS. 10 and 11 and the operations shown in FIGS. 10 and 12 as second quadrant operations.

[0064] In the second quadrant operation described above, power P is transmitted from the secondary circuit 52 to the primary circuit 51 while the discharge direction of the storage battery 31 is blocked in the secondary circuit 52. In this case, the current flowing in the discharge direction of the storage battery 31 is controlled in the secondary circuit 52, and power P is transmitted to the primary circuit 51. As a result, it is possible to realize an operation in which the storage battery 31 is discharged while the secondary terminal voltage Vor of the power converter 40 is set to a negative voltage.

[0065] 11 , the first negative switch QL1 and the body diode DL1 are turned off, blocking current flow in a direction that applies a positive voltage to the secondary winding 50b. This allows a negative voltage to be applied to the secondary winding 50b, and power P can be transmitted from the secondary circuit 52 to the primary circuit 51. Also, during the operation shown in FIG. 12 , the second negative switch QL2 and the body diode DL2 are turned off, blocking current flow in a direction that applies a negative voltage to the secondary winding 50b. This allows a positive voltage to be applied to the secondary winding 50b, and power P can be transmitted from the secondary circuit 52 to the primary circuit 51.

[0066] Unlike the present embodiment, in a comparative example in which the secondary circuit 52 includes only the positive switches QH1 and QH2 among the switches QH1, QH2, QL1, and QL2, power cannot be transmitted from the secondary circuit 52 to the primary circuit 51. This is because, in the secondary circuit 52, if the blocking direction is the charging direction of the storage battery 31 and the current-permitting direction is constant, i.e., the discharging direction of the storage battery 31, the current flowing in the discharging direction of the storage battery 31 cannot be controlled in the secondary circuit 52 by switching control of the positive switches QH1 and QH2.

[0067] 13 shows the current paths when third-quadrant operation is performed in the power converter 40. When third-quadrant operation is performed, the control unit 16b controls the switching of the primary-side circuit 51 and the secondary-side circuit 52 so as to transmit power P from the primary-side circuit 51 to the secondary-side circuit 52 while the positive-side switches QH1 and QH2 are fixed on. In this case, a current flows through the secondary-side circuit 52 so as to charge the storage battery 31. More specifically, the battery current Ia and the converter current Ib are input from the positive side of the load 21 to the secondary-side circuit 52. The battery current Ia input to the secondary-side circuit 52 flows to the positive side of the storage battery 31. The converter current Ib is input to the primary-side circuit 51.

[0068] In the present embodiment, when the control unit 16b performs the third quadrant operation in the power converter 40, the control unit 16b performs switching control of the primary side circuit 51 and the secondary side circuit 52 so as to step down the voltage input to the primary side circuit 51 and apply the stepped-down voltage to the secondary side terminal pair. For example, the control unit 16b alternately and repeatedly executes the operations shown in Fig. 14 and Fig. 15 as the third quadrant operation.

[0069] As shown in Fig. 14, the control unit 16b turns on the first and fourth conversion switches S1 and S4 and the first and second positive switches QH1 and QH2, and turns off the second and third conversion switches S2 and S3 and the first and second negative switches QL1 and QL2. In this case, in the primary circuit 51, the converter current Ib flows through the primary positive terminal 41, the first conversion switch S1, the primary winding 50a, the fourth conversion switch S4, and the primary negative terminal 42 in this order. As a result, a positive voltage is applied to the primary winding 50a. A positive voltage is induced in the secondary winding 50b.

[0070] 14 , in the secondary circuit 52, the battery current Ia and the converter current Ib flow in this order through the secondary positive terminal 43, the reactor 55, the secondary winding 50b, the first positive switch QH1, the body diode DL1 of the first negative switch QL1, and the secondary negative terminal 44. As a result, a negative voltage is applied to the secondary capacitor 54.

[0071] As shown in Fig. 15, the control unit 16b turns on the second and third conversion switches S2 and S3 and the first and second positive switches QH1 and QH2, and turns off the first and fourth conversion switches S1 and S4 and the first and second negative switches QL1 and QL2. In this case, in the primary circuit 51, the converter current Ib flows through the primary positive terminal 41, the third conversion switch S3, the primary winding 50a, the second conversion switch S2, and the primary negative terminal 42 in this order. As a result, a negative voltage is applied to the primary winding 50a. A negative voltage is induced in the secondary winding 50b.

[0072] 15 , in the secondary circuit 52, the battery current Ia and the converter current Ib flow in this order through the secondary positive terminal 43, the reactor 55, the secondary winding 50b, the second positive switch QH2, the body diode DL2 of the second negative switch QL2, and the secondary negative terminal 44. As a result, a negative voltage is applied to the secondary capacitor 54.

[0073] In the third quadrant operation described above, power P is transmitted from the primary circuit 51 to the secondary circuit 52 while the discharge direction of the storage battery 31 is blocked in the secondary circuit 52. In this case, current flowing in the discharge direction in the secondary circuit 52 is blocked. This causes a negative voltage to be applied to the secondary capacitor 54, and the storage battery 31 is charged. As a result, it is possible to realize an operation in which the storage battery 31 is charged while the secondary terminal voltage Vor of the power converter 40 is kept negative.

[0074] 14, a positive voltage is induced in the secondary winding 50b, but the second negative switch QL2 and the body diode DL2, which are turned off, prevent current from flowing from the secondary negative terminal 44 to the second end of the secondary winding 50b. Also, during the operation shown in Fig. 15, a negative voltage is induced in the secondary winding 50b, but the first negative switch QL1 and the body diode DL1, which are turned off, prevent current from flowing from the secondary negative terminal 44 to the first end of the secondary winding 50b. Therefore, as described with reference to Figs. 13 to 15, the battery current Ia and the converter current Ib flow in the charging direction of the storage battery 31, and a negative voltage is applied to the secondary capacitor 54.

[0075] Unlike the present embodiment, in a comparative example in which the secondary circuit 52 includes only the positive switches QH1 and QH2 among the switches QH1, QH2, QL1, and QL2, a negative voltage cannot be applied to the secondary capacitor 54. This is because, in the secondary circuit 52, if the blocking direction is the charging direction of the storage battery 31 and the current-carrying direction is a fixed direction that is the discharging direction of the storage battery 31, the discharge current of the secondary capacitor 54 to which a negative voltage is applied cannot be blocked.

[0076] 16 shows a current path when fourth-quadrant operation is performed in the power converter 40. When fourth-quadrant operation is performed, the control unit 16b controls the switching of the primary-side circuit 51 and the secondary-side circuit 52 so that power P is transmitted from the secondary-side circuit 52 to the primary-side circuit 51 while the negative-side switches QL1 and QL2 are fixed on. In this case, a current flows through the secondary-side circuit 52 so that the storage battery 31 is charged. Specifically, a battery current Ia is output from the positive side of the load 21 and input to the secondary-side circuit 52. The power input to the secondary-side circuit 52 is transmitted to the primary-side circuit 51, and a converter current Ib is output from the primary-side circuit 51. The battery current Ia and the converter current Ib flow to the positive side of the storage battery 31.

[0077] In the present embodiment, when the power converter 40 performs the fourth quadrant operation, the control unit 16b controls the switching of the primary circuit 51 and the secondary circuit 52 so as to boost the voltage input to the secondary circuit 52 and apply the boosted voltage to the primary terminal pair. For example, the control unit 16b performs the operations shown in Figs. 17, 18, and 19 as the fourth quadrant operation.

[0078] 17 , the control unit 16b turns off the first to fourth conversion switches S1 to S4 and turns on the first and second positive switches QH1 and QH2 and the first and second negative switches QL1 and QL2. In this case, the battery current Ia flows through two current paths in the secondary circuit 52 so that a positive voltage is applied to the secondary capacitor 54. In the first current path, the current flows through the secondary positive terminal 43, the reactor 55, the secondary winding 50b, the first positive switch QH1, the first negative switch QL1, and the secondary negative terminal 44 in this order. In the second current path, the current flows through the secondary positive terminal 43, the reactor 55, the secondary winding 50b, the second positive switch QH2, the second negative switch QL2, and the secondary negative terminal 44 in this order. 17, power is not basically transmitted from the secondary circuit 52 to the primary circuit 51, and no current flows through the primary circuit 51.

[0079] 18, the control unit 16b turns off the first to fourth conversion switches S1 to S4 and the first positive switch QH1, and turns on the second positive switch QH2 and the first and second negative switches QL1 and QL2. In this case, in the secondary circuit 52, the battery current Ia flows in the following order: secondary positive terminal 43, reactor 55, secondary winding 50b, second positive switch QH2, second negative switch QL2, and secondary negative terminal 44. As a result, a positive voltage is applied to the secondary winding 50b. A positive voltage is induced in the primary winding 50a.

[0080] 18, in the primary circuit 51, a converter current Ib flows in the following order: the primary negative terminal 42, the body diode D4 of the fourth conversion switch S4, the primary winding 50a, the body diode D1 of the first conversion switch S1, and the primary positive terminal 41. The converter current Ib output from the primary circuit 51 is input to the positive side of the storage battery 31. During the operation shown in FIG. 18, a positive voltage is applied to the secondary capacitor 54.

[0081] 19, the control unit 16b turns off the first to fourth conversion switches S1 to S4 and the second positive switch QH2, and turns on the first positive switch QH1 and the first and second negative switches QL1 and QL2. In this case, in the secondary circuit 52, the battery current Ia flows in the following order: secondary positive terminal 43, reactor 55, secondary winding 50b, first positive switch QH1, first negative switch QL1, and secondary negative terminal 44. As a result, a negative voltage is applied to the secondary winding 50b. A negative voltage is induced in the primary winding 50a.

[0082] 19, in the primary circuit 51, a converter current Ib flows in the following order: the primary negative terminal 42, the body diode D2 of the second conversion switch S2, the primary winding 50a, the body diode D3 of the third conversion switch S3, and the primary positive terminal 41. The converter current Ib output from the primary circuit 51 is input to the positive side of the storage battery 31. During the operation shown in FIG. 19, a positive voltage is applied to the secondary capacitor 54.

[0083] The control unit 16b alternately performs the operations shown in FIGS. 17 and 18 and the operations shown in FIGS. 17 and 19 as the fourth quadrant operations.

[0084] In the fourth quadrant operation described above, power P is transmitted from the secondary circuit 52 to the primary circuit 51 while the charging direction of the storage battery 31 is blocked in the secondary circuit 52. In this case, the current flowing in the charging direction of the storage battery 31 is controlled in the secondary circuit 52, and power P is transmitted to the primary circuit 51. As a result, it is possible to realize an operation in which the storage battery 31 is charged while the secondary terminal voltage Vor of the power converter 40 is set to a positive voltage.

[0085] 18, the first positive switch QH1 and body diode DH1, which are turned off, prevent a current from flowing in a direction that would apply a negative voltage to the secondary winding 50b. This allows a positive voltage to be applied to the secondary winding 50b, and power P can be transmitted to the primary circuit 51. Furthermore, during the operation shown in FIG. 19, the second positive switch QH2 and body diode DH2, which are turned off, prevent a current from flowing in a direction that would apply a positive voltage to the secondary winding 50b. This allows a negative voltage to be applied to the secondary winding 50b, and power P can be transmitted to the primary circuit 51.

[0086] Unlike the present embodiment, in a comparative example in which the secondary circuit 52 includes only the negative switches QL1 and QL2 among the switches QH1, QH2, QL1, and QL2, power cannot be transmitted from the secondary circuit 52 to the primary circuit 51. This is because, in the secondary circuit 52, if the blocking direction is the discharging direction of the storage battery 31 and the current-permitting direction is fixed as the charging direction of the storage battery 31, the current in the charging direction of the storage battery 31 cannot be controlled by switching control of the negative switches QL1 and QL2.

[0087] 20 shows an example of a control procedure executed by the control device 16. This control is repeatedly executed at predetermined intervals.

[0088] In step S10, the setting unit 16a acquires the secondary-side terminal voltage Vor, the secondary-side current Ior, the voltage Vbat of the storage battery 31, and the current Ibat of the storage battery 31. The secondary-side terminal voltage Vor can be a detected value of the voltage sensor 45. The secondary-side current Ior can be a detected value of the current sensor 46. The voltage Vbat and current Ibat of the storage battery 31 can be values ​​calculated based on the detected values ​​of the battery monitoring device 32.

[0089] In step S11, the setting unit 16a sets the secondary command voltage Vo* and the secondary command current Io* based on the acquired secondary terminal voltage Vor, secondary current Ior, voltage Vbat of the storage battery 31, and current Ibat of the storage battery 31.

[0090] In step S12, the setting unit 16a determines whether the set secondary-side command voltage Vo* is a positive voltage. In step S13, the setting unit 16a determines whether the set secondary-side command voltage Vo* is a negative voltage. If the determination in step S12 is affirmative, the processes of steps S14 and S15 are performed. If the determination in step S12 is negative and the determination in step S13 is affirmative, the processes of steps S16 and S17 are performed. If the determinations in steps S12 and S13 are negative, the process of step S18 is performed.

[0091] In step S14, the setting unit 16a sets the negative switches QL1 and QL2 as fixed-on switches, and sets the positive switches QH1 and QH2 as control switches. In step S15, the control unit 16b performs first-quadrant operation or fourth-quadrant operation as switching control. In this embodiment, if the set secondary-side command current Io* is a positive value, first-quadrant operation is performed. If the set secondary-side command current Io* is a negative value, fourth-quadrant operation is performed.

[0092] In step S16, the setting unit 16a sets the positive switches QH1 and QH2 as fixed-on switches, and sets the negative switches QL1 and QL2 as control switches. In step S17, the control unit 16b performs second-quadrant operation or third-quadrant operation as switching control. In this embodiment, when the set secondary-side command current Io* is a positive value, the second-quadrant operation is performed. When the set secondary-side command current Io* is a negative value, the third-quadrant operation is performed.

[0093] In step S18, the control unit 16b stops the operation of the power converter 40. For example, the operation is stopped with the first to fourth conversion switches S1 to S4 fixed off and the first and second positive-side switches QH1 and QH2 and the first and second negative-side switches QL1 and QL2 fixed on. Note that instead of stopping the operation of the power converter 40 with the switches QH1, QH2, QL1, and QL2 fixed on, the operation of the power converter 40 may be stopped with only the positive-side switches QH1 and QH2 fixed on among the switches QH1, QH2, QL1, and QL2. In this case, a current in the charging direction is allowed to flow through the secondary-side circuit 52. Alternatively, the operation of the power converter 40 may be stopped with only the negative-side switches QL1 and QL2 fixed on among the switches QH1, QH2, QL1, and QL2. In this case, a current in the discharging direction is allowed to flow through the secondary-side circuit 52.

[0094] In this embodiment, based on the polarity of the secondary-side command voltage Vo*, one of the positive-side switches QH1, QH2 and the negative-side switches QL1, QL2 is set as a fixed-on switch, and the other is set as a control switch. Switching control is performed between the set control switch and the first to fourth conversion switches S1 to S4. More specifically, when the negative-side switches QL1, QL2 are set as fixed-on switches and the positive-side switches QH1, QH2 are set as control switches, first-quadrant operation or fourth-quadrant operation is performed. As a result, the secondary-side terminal voltage Vor is controlled to a positive voltage. When the positive-side switches QH1, QH2 are set as fixed-on switches and the negative-side switches QL1, QL2 are set as control switches, second-quadrant operation or third-quadrant operation is performed. As a result, the secondary-side terminal voltage Vor is controlled to a negative voltage. Therefore, in the power converter 40, it is possible to select the polarity of the voltage to be output as the secondary side terminal voltage Vor, and appropriately perform switching control to output a voltage of the selected polarity.

[0095] 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. 21 , a power conversion system 10 includes three modules: a first storage battery module 30, a second storage battery module 60, and a third storage battery module 90. The first storage battery module 30 has the same configuration as the storage battery module 30 described above in Fig. 1 , and includes a storage battery 31 and a power converter 40.

[0096] Like the first storage battery module 30, the second storage battery module 60 and the third storage battery module 90 include storage batteries 61, 91 and power converters 70, 100. Hereinafter, the storage battery 31 and power converter 40 of the first storage battery module 30 will be referred to as the "first storage battery 31" and the "first power converter 40," the storage battery 61 and power converter 70 of the second storage battery module 60 will be referred to as the "second storage battery 61" and the "second power converter 70," and the storage battery 91 and power converter 100 of the third storage battery module 90 will be referred to as the "third storage battery 91" and the "third power converter 100."

[0097] 1 , the first power converter 40 includes a primary terminal pair consisting of a primary positive terminal 41 and a primary negative terminal 42, and a secondary terminal pair consisting of a secondary positive terminal 43 and a secondary negative terminal 44. The second power converter 70 includes a primary terminal pair consisting of a primary positive terminal 71 and a primary negative terminal 72, and a secondary terminal pair consisting of a secondary positive terminal 73 and a secondary negative terminal 74. The third power converter 100 includes a primary terminal pair consisting of a primary positive terminal 101 and a primary negative terminal 102, and a secondary terminal pair consisting of a secondary positive terminal 103 and a secondary negative terminal 104. In each storage battery module 30, 60, 90, the connection relationship between each terminal 41 to 44, 71 to 74, 101 to 104 of the corresponding power converter 40, 70, 100, the corresponding storage battery 31, 61, 91, and the load 21 is the same as in the case of the storage battery module 30 described above in Figure 1, so detailed explanation will be omitted.

[0098] Each of the power converters 40, 70, and 100 includes a transformer, a primary circuit, a secondary circuit, a primary capacitor, and a secondary capacitor. The primary circuit 51 of each of the power converters 40, 70, and 100 is a full-bridge circuit. The secondary circuit of each of the power converters 40, 70, and 100 is a center-tap circuit and includes a first bidirectional switch, a second bidirectional switch, and a reactor. The circuit configuration of each of the power converters 40, 70, and 100 is the same as that of the first embodiment, so detailed description thereof will be omitted.

[0099] In this embodiment, the battery monitoring devices 32, 62, 92 are provided corresponding to the respective storage batteries 31, 61, 91. For example, the first battery monitoring device 32 detects the terminal voltage, current, internal resistance, SOC, etc. of each battery cell constituting the first storage battery 31, and monitors the state of the first storage battery 31. The second battery monitoring device 62 monitors the state of the second storage battery 61, similar to the first battery monitoring device 32. The third battery monitoring device 92 monitors the state of the third storage battery 91, similar to the first battery monitoring device 32. The detected values ​​detected by the respective battery monitoring devices 32, 62, 92 are input to the control device 16 provided in the power conversion system 10.

[0100] Voltage sensors 45, 75, 105 and current sensors 46, 76, 106 are provided corresponding to each storage battery module 30, 60, 90. The first, second, and third voltage sensors 45, 75, 105 detect secondary-side terminal voltages Vo1r, Vo2r, and Vo3r of the corresponding power converters 40, 70, and 100. The first, second, and third current sensors 46, 76, and 106 detect secondary-side currents Io1r, Io2r, and Io3r flowing through the secondary sides of the corresponding power converters 40, 70, and 100. The detected values ​​of each sensor 45, 46, 75, 76, 105, and 106 are input to the control device 16.

[0101] Based on the various detected values ​​input, the control device 16 performs switching control of the power converters 40, 70, and 100. In this embodiment, as in the first embodiment, the capacity of each of the power converters 40, 70, and 100 can be reduced.

[0102] Specifically, the secondary-side terminal voltages Vo1r, Vo2r, and Vo3r applied to the secondary-side terminal pairs of each power converter 40, 70, and 100 are the differential voltages between the voltages across each path 13 and 14 and the voltages Vbat1, Vbat2, and Vbat3 of the corresponding storage batteries 31, 61, and 91. Therefore, the rated secondary voltage on the secondary side of each power converter 40, 70, and 100 can be set to a voltage (e.g., 16 V) lower than the rated voltage (e.g., 400 V) of the corresponding storage battery 31, 61, and 91. This allows the capacity of each power converter 40, 70, and 100 to be reduced.

[0103] The control device 16 controls the switching of each of the power converters 40, 70, and 100. Specifically, the control device 16 causes each of the power converters 40, 70, and 100 to perform one of the first to fourth quadrant operations. Each of the power converters 40, 70, and 100 can perform one of the first to fourth quadrant operations in the same manner as described in the first embodiment.

[0104] In this embodiment, the control described above with reference to FIG. 20 is executed with the following modifications.

[0105] In step S10, the setting unit 16a acquires the secondary terminal voltages Vo1r, Vo2r, Vo3r, the secondary currents Io1r, Io2r, Io3r, the voltages Vbat1, Vbat2, Vbat3 and currents Ibat1, Ibat2, Ibat3 of the storage batteries 31, 61, 91.

[0106] In step S11, the setting unit 16a sets the secondary command voltages Vo1*, Vo2*, Vo3* and secondary command currents Io1*, Io2*, Io3* of each power converter 40, 70, 100 based on the acquired secondary terminal voltages Vo1r, Vo2r, Vo3r, each secondary current Io1r, Io2r, Io3r, and the voltages Vbat1, Vbat2, Vbat3 and currents Ibat1, Ibat2, Ibat3 of each storage battery 31, 61, 91.

[0107] In this embodiment, the setting unit 16a and the control unit 16b perform the processes of steps S12 to S18 for each of the first power converter 40, the second power converter 70, and the third power converter 100. That is, in steps S12 and S13, the setting unit 16a determines whether the polarity of each of the secondary-side command voltages Vo1*, Vo2*, and Vo3* is positive or negative. Depending on the determination results of steps S12 and S13, the setting unit 16a performs any one of the processes of steps S14 and S15, steps S16 and S17, and step S18 for each of the first power converter 40, the second power converter 70, and the third power converter 100.

[0108] 22 to 32 show an example of the operation of the power conversion system 10. In FIGS. 22 to 31, a charger 25 serving as the load 21 is electrically connected to the power conversion system 10, and power is transmitted between the charger 25 and the first and second storage battery modules 30, 60. The charger 25 is, for example, a stationary charger provided outside the vehicle. In addition, in FIGS. 22 to 32, a situation is assumed in which the voltage Vbat1 of the first storage battery 31 is higher than the voltage Vbat2 of the second storage battery 61. For example, a situation is assumed in which the voltage Vbat1 of the first storage battery 31 is 400 V, and the voltage Vbat2 of the second storage battery 61 is 390 V.

[0109] 22 to 26, the control device 16 causes the first and second power converters 40, 70 to operate in the third quadrant or the fourth quadrant when the first storage battery 31 and the second storage battery 61 are charged by the charger 25. In this case, as shown in FIGS. 25 and 26, the control device 16 may stop the operation of the first power converter 40 or the second power converter 70.

[0110] In FIG. 22 , the control device 16 causes the first and second power converters 40 and 70 to operate in the fourth quadrant. In this case, the secondary-side terminal voltages Vo1r and Vo2r are added to the voltages Vbat1 and Vbat2 of the first and second storage batteries 31 and 61, respectively, to charge the storage batteries 31 and 61. In FIG. 23 , the control device 16 causes the first and second power converters 40 and 70 to operate in the third quadrant. In this case, the secondary-side terminal voltages Vo1r and Vo2r are subtracted from the voltages Vbat1 and Vbat2 of the first and second storage batteries 31 and 61, respectively, to charge the storage batteries 31 and 61. By performing the operations shown in FIGS. 22 and 23 , the secondary-side terminal voltages Vo1r and Vo2r are controlled while the charger 25 charges the storage batteries 31 and 61. This makes it possible to control the charging currents Ic1 and Ic2 flowing from the charger 25 to the storage batteries 31 and 61. Therefore, the charger 25 can appropriately charge the storage batteries 31 and 61.

[0111] 24 , the control device 16 causes the first power converter 40 to operate in the third quadrant and the second power converter 70 to operate in the fourth quadrant. In this case, the secondary-side terminal voltages Vo1r and Vo2r can be controlled so that the output voltage of the first storage battery module 30 and the output voltage of the second storage battery module 60 approach each other. Therefore, compared to the operations described in FIGS. 22 and 23 , the amount of voltage adjustment on the secondary side of each power converter 40 and 70 can be reduced, and the storage batteries 31 and 61 can be charged by the charger 25.

[0112] In FIG. 25 , the control device 16 stops the operation of the first power converter 40 and causes the second power converter 70 to perform fourth-quadrant operation. In this case, the control device 16 turns off the first to fourth conversion switches in the first power converter 40 and turns on at least the first and second positive-side switches among the first and second positive-side switches and the first and second negative-side switches. Also, in FIG. 26 , the control device 16 causes the first power converter 40 to perform third-quadrant operation and stops the operation of the second power converter 70. In this case, the control device 16 turns off the first to fourth conversion switches in the second power converter 70 and turns on at least the first and second positive-side switches among the first and second positive-side switches and the first and second negative-side switches. The operations shown in FIGS. 25 and 26 can prevent unnecessary switching control from being performed in the first power converter 40 or the second power converter 70. As a result, the occurrence of power loss in the power conversion system 10 can be suppressed while the charger 25 charges the storage batteries 31 and 61 .

[0113] 27 to 31, when discharging the first storage battery 31 and charging the second storage battery 61, the control device 16 causes the first power converter 40 to perform first-quadrant operation or second-quadrant operation, and causes the second power converter 70 to perform third-quadrant operation or fourth-quadrant operation. In this case, as shown in FIGS. 30 and 31, the control device 16 may stop the operation of the first power converter 40 or the second power converter 70.

[0114] In Fig. 27 , the control device 16 causes the first power converter 40 to perform first-quadrant operation and the second power converter 70 to perform fourth-quadrant operation. In this case, secondary-side terminal voltages Vo1r and Vo2r are added to the voltages Vbat1 and Vbat2 of the first and second storage batteries 31 and 61, respectively, and a current flows from the first storage battery 31 to the second storage battery 61. In Fig. 28 , the control device 16 causes the first power converter 40 to perform second-quadrant operation and the second power converter 70 to perform third-quadrant operation. In this case, secondary-side terminal voltages Vo1r and Vo2r are subtracted from the voltages Vbat1 and Vbat2 of the first and second storage batteries 31 and 61, respectively, and a current flows from the first storage battery 31 to the second storage battery 61. 27 and 28 are performed, and the secondary-side terminal voltages Vo1r and Vo2r are controlled while a current flows from the first storage battery 31 to the second storage battery 61. This makes it possible to control the inter-battery current I12 flowing from the first storage battery 31 to the second storage battery 61 and the charging current Ic2 flowing from the charger 25 to the second storage battery 61. Therefore, while the second storage battery 61 is being charged by the charger 25, it is possible to adjust the amount of charge (e.g., SOC) of the first storage battery 31 and the amount of charge of the second storage battery 61.

[0115] In Fig. 29 , the control device 16 causes the first power converter 40 to operate in the first quadrant and the second power converter 70 to operate in the third quadrant. In this case, the control device 16 can control the secondary-side terminal voltages Vo1r and Vo2r so that the output voltages of the first storage battery module 30 and the second storage battery module 60 deviate from each other. This allows the inter-battery current I12 and the charging current Ic2 to be increased compared to the operations described in Figs. 27 and 28 . This allows the amount of power stored in the first storage battery 31 and the amount of power stored in the second storage battery 61 to be quickly adjusted.

[0116] In FIG. 30 , the control device 16 stops the operation of the first power converter 40 and causes the second power converter 70 to perform fourth-quadrant operation. In this case, the control device 16 turns off the first to fourth conversion switches in the first power converter 40 and turns on at least the first and second negative-side switches among the first and second positive-side switches and the first and second negative-side switches. Also, in FIG. 31 , the control device 16 causes the first power converter 40 to perform second-quadrant operation and stops the operation of the second power converter 70. The operations shown in FIGS. 30 and 31 can prevent unnecessary switching control from being performed in the first power converter 40 or the second power converter 70. As a result, the amount of electricity stored in each storage battery 31, 61 can be adjusted while suppressing power loss in the power conversion system 10. As a result, the amount of electricity stored in the first storage battery 31 and the amount of electricity stored in the second storage battery 61 can be adjusted while suppressing power loss in the power conversion system 10.

[0117] 32 assumes a situation in which power is exchanged between the first and second storage battery modules 30, 60 in order to raise the temperature of each storage battery 31, 61 or measure the impedance of each storage battery 31, 61. The control device 16 alternately repeats an operation A of transmitting power from the second storage battery 61 to the first storage battery 31 and an operation B of transmitting power from the first storage battery 31 to the second storage battery 61.

[0118] As operation A, the control device 16 causes the first power converter 40 to perform third-quadrant operation or fourth-quadrant operation, and causes the second power converter 70 to perform first-quadrant operation or second-quadrant operation. Alternatively, as operation A, the control device 16 may stop the operation of at least one of the first power converter 40 and the second power converter 70. During the period in which operation A is performed, an inter-battery current I21 flows from the second storage battery 61 to the first storage battery 31.

[0119] As operation B, the control device 16 causes the first power converter 40 to perform first-quadrant operation or second-quadrant operation, and causes the second power converter 70 to perform third-quadrant operation or fourth-quadrant operation. Alternatively, as operation B, the control device 16 may stop the operation of at least one of the first power converter 40 and the second power converter 70. During the period in which operation B is performed, an inter-battery current I12 flows from the first storage battery 31 to the second storage battery 61.

[0120] By alternately repeating the above-described operations A and B, an AC current flows between the storage batteries 31 and 61. This makes it possible to increase the temperature of the storage batteries 31 and 61 or measure the impedance of the storage batteries 31 and 61.

[0121] In this embodiment, the power conversion system 10 includes multiple storage batteries 31, 61, and 91. Power converters 40, 70, and 100 are provided corresponding to the storage batteries 31, 61, and 91. The secondary circuits of the power converters 40, 70, and 100 include first and second bidirectional switches. In this case, either a positive voltage or a negative voltage can be selectively output from the secondary terminal pairs of the power converters 40, 70, and 100. Therefore, in the power conversion system 10 including the multiple storage batteries 31, 61, and 91, various operations can be performed to appropriately connect the storage batteries 31, 61, and 91 in parallel. For example, the operations described above with reference to FIGS. 22 to 32 can be performed.

[0122] <Modification of the Second Embodiment> In the power conversion system 10, instead of providing a power converter for each of the three storage batteries 31, 61, and 91, a power converter may be provided for each of two of the storage batteries 31, 61, and 91. For example, as shown in FIG. 33 , the first and second storage battery modules 30 and 60 may include first and second power converters 40 and 70, respectively, and the third storage battery module 90 may not include a power converter. In this case, the first and second storage batteries 31 and 61 correspond to the “target power storage unit,” and the third storage battery 91 corresponds to the “non-target power storage unit.” In this embodiment, the number of power converters can be reduced compared to when a power converter is provided for each of the storage batteries 31, 61, and 91, thereby enabling the power conversion system 10 to be appropriately downsized.

[0123] 33 in which only a positive voltage or a negative voltage can be output from the secondary-side terminal pairs of the first and second power converters 40, 70, there is a possibility that the configuration of the power conversion system 10 will be limited. Specifically, in the comparative example in which only a positive voltage can be output from the secondary-side terminal pairs of the first and second power converters 40, 70, there is a possibility that the first and second storage batteries 31, 61 will be limited to storage batteries with a lower voltage than the third storage battery 91.

[0124] In this embodiment, the power converters provided corresponding to some of the multiple storage batteries can selectively output either a positive voltage or a negative voltage from their secondary-side terminal pairs. For example, in Fig. 33, the first and second power converters 40 and 70 can selectively output either a positive voltage or a negative voltage from their secondary-side terminal pairs, thereby enabling appropriate parallel connection of the storage batteries 31, 61, and 91 regardless of the voltage of the third storage battery 91. This prevents the configuration of the power conversion system 10 from being restricted, while enabling the power conversion system 10 to be appropriately downsized.

[0125] In the power conversion system 10 , the power converter may be provided corresponding to any one of the three storage batteries 31 , 61 , and 91 .

[0126] The power conversion system may include two or four or more storage batteries. In this case, it is sufficient that the power converter is provided corresponding to at least one of the two or four or more storage batteries. For the case of two storage batteries described above with reference to FIG. 33 , the power conversion system 10 may include only the first and second storage battery modules 30, 60, or only the first and third storage battery modules 30, 90, among the storage battery modules 30, 60, 90.

[0127] The control device 16 may perform the switching control of the power converters 40, 70, and 100 as follows.

[0128] Fig. 34 shows an example of a control processing procedure executed by the control device 16. In Fig. 34, the same processes as those explained in Fig. 20 are denoted by the same step numbers for convenience.

[0129] In step S20, the setting unit 16a acquires the secondary-side terminal voltages Vo1r, Vo2r, and Vo3r, the secondary-side currents Io1r, Io2r, and Io3r, and the voltages Vbat1, Vbat2, and Vbat3 and currents Ibat1, Ibat2, and Ibat3 of the storage batteries 31, 61, and 91. The secondary-side terminal voltages Vo1r, Vo2r, and Vo3r can be detected by the corresponding voltage sensors 45, 75, and 105. The secondary-side currents Io1r, Io2r, and Io3r can be detected by the corresponding current sensors 46, 76, and 106. The voltages Vbat1, Vbat2, and Vbat3 and currents Ibat1, Ibat2, and Ibat3 of the storage batteries 31, 61, and 91 can be calculated based on the detected values ​​of the corresponding battery monitoring devices 32, 62, and 92.

[0130] In step S21, the setting unit 16a selects a low-voltage battery (corresponding to a "low-voltage storage unit") from among the storage batteries 31, 61, and 91 that has a lower output voltage than the other storage batteries. For example, among the storage batteries 31, 61, and 91, the battery with the lowest acquired voltages Vbat1, Vbat2, and Vbat3 is selected as the low-voltage battery. Also, among the storage batteries 31, 61, and 91, the battery other than the battery with the highest acquired voltages Vbat1, Vbat2, and Vbat3 is selected as the low-voltage battery.

[0131] In step S22, the setting unit 16a sets the secondary command voltage Vox* of the power converter corresponding to the selected low-voltage storage battery to a positive value. The setting unit 16a also sets the secondary command current Iox* of the power converter corresponding to the selected low-voltage storage battery. After the processing of step S22, the process proceeds to step S14.

[0132] By executing the control of FIG. 34, for example, the operation of the second power converter 70 described above with reference to FIGS.

[0133] In this embodiment, a low-voltage battery is selected from the batteries 31, 61, and 91. In the power converter corresponding to the selected low-voltage battery, the negative-side switches QL1 and QL2 are set as fixed-on switches, and the positive-side switches QH1 and QH2 are set as control switches. This makes it possible to control the secondary-side terminal voltage Voxr of the power converter corresponding to the low-voltage battery to a positive voltage, thereby achieving control suitable for increasing the charge / discharge power of the low-voltage battery.

[0134] Fig. 35 shows an example of a control processing procedure executed by the control device 16. In Fig. 35, the same processes as those explained in Figs. 20 and 34 are denoted by the same step numbers for convenience.

[0135] In step S31, the setting unit 16a selects a high-voltage battery (corresponding to a "high-voltage storage unit") that has a higher output voltage than the other batteries from among the batteries 31, 61, and 91. For example, among the batteries 31, 61, and 91, the battery with the highest acquired voltages Vbat1, Vbat2, and Vbat3 is selected as the high-voltage battery. Also, among the batteries 31, 61, and 91, a battery other than the battery with the lowest acquired voltages Vbat1, Vbat2, and Vbat3 is selected as the high-voltage battery.

[0136] In step S32, the setting unit 16a sets the secondary command voltage Voy* of the power converter corresponding to the selected high-voltage battery to a negative value. The setting unit 16a also sets the secondary command current Ioy* of the power converter corresponding to the selected high-voltage battery. After the processing of step S32, the process proceeds to step S16.

[0137] By executing the control of FIG. 35, for example, the operation of the first power converter 40 described above with reference to FIGS.

[0138] In this embodiment, a high-voltage battery is selected from the storage batteries 31, 61, and 91. In the power converter corresponding to the selected high-voltage battery, the positive-side switches QH1 and QH2 are set as fixed-on switches, and the negative-side switches QL1 and QL2 are set as control switches. In this case, the secondary-side terminal voltage Voyr of the power converter corresponding to the high-voltage battery is controlled to a negative voltage. This reduces the output voltage of the power conversion system 10, and reduces the secondary-side terminal voltages of the power converters 40, 70, and 100. Therefore, it is possible to achieve control suitable for connecting the storage batteries 31, 61, and 91 in parallel while preventing overvoltage from being applied to the secondary-side terminal pairs of the power converters 40, 70, and 100.

[0139] 36 and 37 show an example of a control processing procedure executed by the control device 16. In Fig. 36 and 37, the same processes as those explained in Fig. 20, 34, and 35 are denoted by the same step numbers for convenience.

[0140] First, the control shown in Fig. 36 will be described. After the process of step S20 in Fig. 36, the process proceeds to step S41. In step S41, the setting unit 16a selects the low-voltage storage battery having the lowest acquired voltages Vbat1, Vbat2, and Vbat3 from among the storage batteries 31, 61, and 91. After the process of step S41, the process proceeds to step S22.

[0141] After the process of step S22, the process proceeds to step S42. In step S42, the setting unit 16a determines whether the secondary-side command voltage Vox* of the power converter corresponding to the selected low-voltage storage battery exceeds a positive upper limit voltage. The upper limit voltage is determined according to the secondary-side rated voltage of each power converter 40, 70, 100, and is set to a value between 80% and 90% or between 90% and 100% of the secondary-side rated voltage, for example.

[0142] If the determination in step S42 is negative, the process proceeds to step S43. In step S43, the setting unit 16a sets the logic of flag F to L. Flag F is a signal for determining whether it has been determined that the secondary-side command voltage Vox* exceeds the upper limit voltage. After the process in step S43, the process proceeds to step S14.

[0143] If the determination in step S42 is affirmative, the process proceeds to step S44. In step S44, the setting unit 16a sets the logic of flag F to H. After the process in step S44, the process proceeds to step S14.

[0144] Next, the control shown in Fig. 37 will be described. After the process of step S20 in Fig. 37, the process proceeds to step S51. In step S51, the setting unit 16a selects the high-voltage storage battery having the highest acquired voltages Vbat1, Vbat2, Vbat3 from among the storage batteries 31, 61, 91. After the process of step S51, the process proceeds to step S52.

[0145] In step S52, the setting unit 16a determines whether the logic of flag F is H. If the determination in step S52 is negative, the process proceeds to step S53. On the other hand, if the determination in step S52 is positive, the process proceeds to step S54.

[0146] In step S53, the setting unit 16a sets the secondary command voltage Voy* of the power converter corresponding to the selected high-voltage battery to a positive value. The setting unit 16a also sets the secondary command current Ioy* of the power converter corresponding to the selected high-voltage battery. After the processing of step S53, the process proceeds to step S14.

[0147] In step S53, the setting unit 16a may set the secondary-side command voltage Voy* of the power converter corresponding to the selected high-voltage storage battery to 0. In this case, after the processing of step S53, the process proceeds to step S18.

[0148] In step S54, the setting unit 16a sets the secondary command voltage Voy* of the power converter corresponding to the selected high-voltage battery to a negative value. The setting unit 16a also sets the secondary command current Ioy* of the power converter corresponding to the selected high-voltage battery. After the processing of step S54, the process proceeds to step S16.

[0149] In this embodiment, the low-voltage battery with the lowest output voltage and the high-voltage battery with the highest output voltage are selected from the storage batteries 31, 61, and 91. In the power converter corresponding to the selected low-voltage battery, the negative-side switches QL1 and QL2 are set as fixed-on switches, and the positive-side switches QH1 and QH2 are set as control switches. In this case, the secondary-side terminal voltage Voxr of the power converter corresponding to the low-voltage battery is controlled to a positive voltage. To increase the charging and discharging power of the storage batteries 31, 61, and 91, it is desirable to control the secondary-side terminal voltage Voyr of the power converter corresponding to the high-voltage battery to a positive voltage. On the other hand, for example, when the voltage difference between the low-voltage battery and the high-voltage battery is large, there is a concern that an overvoltage may be applied to the secondary-side terminal pair of the power converter corresponding to the low-voltage battery. In this case, it is desirable to control the secondary-side terminal voltage Voyr of the power converter corresponding to the high-voltage battery to a negative voltage.

[0150] Therefore, it is determined whether the secondary-side command voltage Vox* of the power converter corresponding to the selected low-voltage battery exceeds the upper limit voltage. If it is determined that the secondary-side command voltage Vox* of the power converter corresponding to the selected low-voltage battery exceeds the upper limit voltage, the positive-side switches QH1, QH2 of the power converter corresponding to the selected high-voltage battery are set as fixed-on switches, and the negative-side switches QL1, QL2 are set as control switches. In this case, the secondary-side terminal voltage Voyr of the power converter corresponding to the high-voltage battery is controlled to a negative voltage. This makes it possible to prevent an overvoltage from being applied to the secondary-side terminal pair of each power converter corresponding to the low-voltage battery during switching control.

[0151] If it is determined that the secondary-side command voltage Vox* of the power converter corresponding to the selected low-voltage battery does not exceed the upper limit voltage, the negative-side switches QL1 and QL2 of the power converter corresponding to the selected high-voltage battery are set as fixed-on switches, and the positive-side switches QH1 and QH2 are set as control switches. In this case, the secondary-side terminal voltage Voyr of the power converter corresponding to the high-voltage battery is controlled to a positive voltage. This allows for switching control that is suitable for increasing the charge / discharge power of each of the batteries 31, 61, and 91.

[0152] In other words, in this embodiment, the polarity of the secondary-side terminal voltage Voyr of the power converter corresponding to the selected low-voltage storage battery is appropriately controlled depending on whether the secondary-side command voltage Vox* of the power converter corresponding to the selected low-voltage storage battery exceeds the upper limit voltage. This makes it possible to achieve switching control that is suitable for increasing the charge / discharge power of each storage battery 31, 61, 91 while suppressing the application of an overvoltage to the secondary-side terminal pair of each power converter corresponding to the low-voltage storage battery.

[0153] Other Embodiments The above-described embodiments may be modified as follows.

[0154] The pair of switch parts constituting the bidirectional switch are not limited to the first positive switch QH1 and the first negative switch QL1, and the second positive switch QH2 and the second negative switch QL2, whose sources are electrically connected to each other.

[0155] For example, the switch may be a pair of switches whose drains are electrically connected to each other. In this case, the source of the first positive switch may be electrically connected to a first end of the secondary winding 50b. The source of the second positive switch may be electrically connected to a second end of the secondary winding 50b. The sources of the first and second negative switches may be electrically connected to the secondary negative terminal 44 and the second end of the secondary capacitor 54.

[0156] In the present embodiment, when the setting unit 16a determines that the acquired secondary-side command voltage Vo* is a positive voltage, it sets the first and second positive-side switches as fixed-on switches and the first and second negative-side switches as control switches. In other words, when the setting unit 16a determines that the acquired secondary-side command voltage Vo* is a positive voltage, it sets, as fixed-on switches, the switches of a pair of switch units constituting the bidirectional switch, the cathodes of the corresponding body diodes of which are provided on the secondary-side negative terminal 44 side.

[0157] When the setting unit 16a determines that the acquired secondary-side command voltage Vo* is a negative voltage, it sets the first and second negative-side switches as fixed-on switches and the first and second positive-side switches as control switches. In other words, when the setting unit 16a determines that the acquired secondary-side command voltage Vo* is a negative voltage, it sets, as fixed-on switches, the switches of a pair of switch units constituting the bidirectional switch, whose corresponding body diodes have cathodes on the secondary-side positive terminal 43 side.

[0158] The pair of switch units constituting the bidirectional switch is not limited to a positive switch and a negative switch connected in series so that their blocking directions are opposite to each other.

[0159] For example, as shown in Fig. 38, reverse-blocking IGBTs (RB-IGBTs) may be used as the first and second bidirectional switches R1 and R2. In this case, pairs of switch units RH1, RL1, RH2, and RL2 constituting the first and second bidirectional switches R1 and R2 are connected in anti-parallel. Each of the pair of switch units RH1, RL1, RH2, and RL2 has a predetermined blocking direction, and the switch units are connected so that the blocking directions are opposite to each other.

[0160] In this embodiment, when the setting unit 16a determines that the acquired secondary-side command voltage Vo* is a positive voltage, it sets one of the pair of switches RH1, RL1, RH2, and RL2 (the fixed-on switch) as a fixed-on switch and the other of the switches RH1, RH2 as a control switch. In this case, the conduction direction of the fixed-on switches RL1 and RL2 corresponds to the current-permitted direction. On the other hand, when the setting unit 16a determines that the acquired secondary-side command voltage Vo* is a negative voltage, it sets one of the pair of switches RH1, RL1, RH2, and RL2 (the fixed-on switch) as a fixed-on switch and the other of the switches RL1 and RL2 as a control switch. In this case, the conduction direction of the fixed-on switches RH1 and RH2 corresponds to the current-permitted direction.

[0161] The secondary circuit of the power converter is not limited to the center tap circuit described above in Fig. 2. For example, as shown in Fig. 39, the secondary circuit 152 of the power converter 140 may be a center tap circuit including a first bidirectional switch T1 and a second bidirectional switch T2. In this embodiment, N-channel MOSFETs are used as pairs of switches T1a, T1b, T2a, and T1b that constitute the first and second bidirectional switches T1 and T2. The switches T1a, T1b, T2a, and T1b each have a body diode D1a, D1b, D2a, and D2b.

[0162] The sources of the pair of switch units T1a, T1b, T2a, T1b constituting the first and second bidirectional switches T1, T2 are electrically connected to each other. The drain of one of the pair of switch units T1a, T1b constituting the first bidirectional switch T1 (specifically, the switch T1a) is electrically connected to a first end of the secondary winding 50b. The drain of the other of the pair of switch units T1a, T1b constituting the first bidirectional switch T1 (specifically, the switch T1b) is electrically connected to a first end of the reactor 55. The drain of one of the pair of switch units T2a, T2b constituting the second bidirectional switch T2 (specifically, the switch T2a) is electrically connected to a second end of the secondary winding 50b. The drain of the other of the pair of switch units T2a, T2b constituting the second bidirectional switch T2 (specifically, the switch T2b) is electrically connected to a first end of the reactor 55. The center tap of the secondary winding 50 b is electrically connected to the secondary negative terminal 44 and the second end of the secondary capacitor 54 .

[0163] In this embodiment, when the setting unit 16a determines that the acquired secondary-side command voltage Vo* is a positive voltage, it sets one switch T1a, T2a of the pair of switch units T1a, T1b, T2a, T1b as a fixed-on switch and sets the other switch T1b, T2b as a control switch. In this case, the blocking direction of each of the bidirectional switches T1, T2 is set to the charging direction of the storage battery 31. The conducting direction of each of the bidirectional switches T1, T2 is set to the discharging direction of the storage battery 31.

[0164] Furthermore, when the setting unit 16a determines that the acquired secondary-side command voltage Vo* is a negative voltage, it sets one switch T1b, T2b of the pair of switch units T1a, T1b, T2a, T1b as a fixed-on switch and sets the other switch T1a, T2a as a control switch. In this case, the blocking direction of each of the bidirectional switches T1, T2 is set to the discharging direction of the storage battery 31. The conducting direction of each of the bidirectional switches T1, T2 is set to the charging direction of the storage battery 31.

[0165] The secondary circuit of the power converter is not limited to a center-tap circuit. For example, as shown in FIG. 40 , the secondary circuit 252 of the power converter 240 may be a current-fed circuit including first, second, third, and fourth bidirectional switches U1, U2, U3, and U4. In this embodiment, N-channel MOSFETs are used as pairs of switch units UH1, UL1, UH2, UL2, UH3, UL3, UH4, and UL4 that constitute the bidirectional switches U1, U2, U3, and U4. Each of the switches UH1, UL1, UH2, UL2, UH3, UL3, UH4, and UL4 has a body diode DH1, DL1, DH2, DL2, DH3, DL3, DH4, and DL4.

[0166] The sources of a pair of switch sections UH1, UL1, UH2, UL2, UH3, UL3, UH4, and UL4 constituting each of the bidirectional switches U1, U2, U3, and U4 are electrically connected to each other. The drains of the positive switches UH1 and UH3 constituting the first and third bidirectional switches U1 and U3 are electrically connected to a first end of the reactor 55. The drain of the negative switch UL1 constituting the first bidirectional switch U1 and the drain of the positive switch UH2 constituting the second bidirectional switch U2 are electrically connected to a first end of the secondary winding 50b. The drain of the negative switch UL3 constituting the third bidirectional switch U3 and the drain of the positive switch UH4 constituting the fourth bidirectional switch U4 are electrically connected to a second end of the secondary winding 50b. The drains of the negative switches UL2 and UL4 constituting the second and fourth bidirectional switches U2 and U4 are electrically connected to the second end of the secondary capacitor 54 and the secondary negative terminal 44.

[0167] In the present embodiment, when the setting unit 16a determines that the acquired secondary-side command voltage Vo* is a positive voltage, it sets the negative-side switches UL1, UL2, UL3, and UL4 of the pair of switch units UH1, UL1, UH2, UL2, UH3, UL3, UH4, and UL4 as fixed-on switches and the positive-side switches UH1, UH2, UH3, and UH4 as control switches. On the other hand, when the setting unit 16a determines that the acquired secondary-side command voltage Vo* is a negative voltage, it sets the positive-side switches UH1, UH2, UH3, and UH4 of the pair of switch units UH1, UL1, UH2, UL2, UH3, UL3, UH4, and UL4 as fixed-on switches and the negative-side switches UL1, UL2, UL3, and UL4 as control switches.

[0168] 41 , the power conversion system 10 may be configured to be able to switch the electrical connection relationships of the storage battery modules 30, 60, and 90. The power conversion system 10 may include first, second, and third high-potential-side switches 301 a, 302 a, and 303 a, and first, second, and third low-potential-side switches 301 b, 302 b, and 303 b. Each of the switches 301 a, 302 a, 303 a, 301 b, 302 b, and 303 b is a relay or a semiconductor switching element.

[0169] The first high potential side switch 301a is provided in the high potential side path 13 closer to the first storage battery module 30 than the connection point with the second storage battery module 60. The first low potential side switch 301b is provided in the low potential side path 14 closer to the first storage battery module 30 than the connection point with the second storage battery module 60, and on the lower potential side than the connection point with the primary side negative terminal 42 of the first power converter 40.

[0170] The second high-potential-side switch 302a is provided in a path that electrically connects the secondary-side positive terminal 73 of the second power converter 70 and the high-potential-side path 13. The second low-potential-side switch 302b is provided in a path that electrically connects the negative terminal of the second storage battery 61 and the low-potential-side path 14, on the lower-potential side of the connection point with the primary-side negative terminal 72 of the second power converter 70.

[0171] The third high-potential-side switch 303a is provided in a path electrically connecting the secondary-side positive terminal 103 of the third power converter 100 and the high-potential-side path 13. The third low-potential-side switch 303b is provided in a path electrically connecting the negative terminal of the third storage battery 91 and the low-potential-side path 14, on the lower potential side of the connection point with the primary-side negative terminal 102 of the third power converter 100.

[0172] The power conversion system 10 may include a first connection path 304 and a second connection path 305. A first end of the first connection path 304 is electrically connected to a portion of the low potential side path 14 between the negative terminal of the first storage battery 31 and the first low potential side switch 301b. A second end of the first connection path 304 is electrically connected to a portion of the path that electrically connects the secondary side positive terminal 73 of the second power converter 70 and the high potential side path 13 between the secondary side positive terminal 73 and the second high potential side switch 302a.

[0173] A first end of the second connection path 305 is electrically connected between the negative terminal of the second storage battery 61 and the second low-potential-side switch 302b in the path that electrically connects the negative terminal of the second storage battery 61 and the low-potential-side path 14. A second end of the second connection path 305 is electrically connected between the secondary-side positive terminal 103 and the third high-potential-side switch 303a in the path that electrically connects the secondary-side positive terminal 103 of the third power converter 100 and the high-potential-side path 13.

[0174] The power conversion system 10 includes a first connection switch 306 and a second connection switch 307. Each of the connection switches 306, 307 is a relay or a semiconductor switching element. The first connection switch 306 is provided on the first connection path 304. The second connection switch 307 is provided on the second connection path 305.

[0175] The control device 16 may switch the electrical connection relationship between the load 21 and the storage battery modules 30, 60, and 90 by controlling the switches 301a, 302a, 303a, 301b, 302b, 303b, 306, and 307. For example, the control device 16 may turn on the switches 301a, 302a, 303a, 301b, 302b, and 303b and turn off the connection switches 306 and 307. In this case, the storage battery modules 30, 60, and 90 are electrically connected in parallel to the load 21. Alternatively, for example, the control device 16 may turn on the switches 301a, 303b, 306, and 307 and turn off the switches 301b, 302a, 302b, and 303a. In this case, the storage battery modules 30, 60, and 90 are electrically connected in series to the load 21.

[0176] In this embodiment, when each storage battery module 30, 60, 90 is electrically connected in parallel to the load 21, the control device 16 can cause each power converter 40, 70, 100 to perform first to fourth quadrant operation, as in the above embodiments.

[0177] The secondary terminal pair of the power converter may be electrically connected in series to the storage battery at the negative terminal side of the storage battery instead of the positive terminal side of the storage battery. In this case, the positive terminal side of the storage battery is electrically connected to the inverter 22 via the high-potential side path 13. The secondary positive terminal of the power converter is electrically connected to the negative terminal side of the storage battery. The secondary negative terminal of the power converter is electrically connected to the inverter 22 via the low-potential side path 14.

[0178] The setting unit 16a may set only one of the secondary command voltage and the secondary command current, instead of setting both the secondary command voltage and the secondary command current. Even in this case, it is possible to execute the processes described above with reference to FIGS.

[0179] Taking the first embodiment as an example, in step S11 of FIG. 20 , only the secondary-side command voltage Vo* out of the secondary-side command voltage Vo* and the secondary-side command current Io* may be set based on the acquired secondary-side terminal voltage Vor. In step S15, the control unit 16b may perform first-quadrant operation if the acquired secondary-side current Ior is a positive value. In step S17, the control unit 16b may perform second-quadrant operation if the acquired secondary-side current Ior is a positive value. In step S17, the control unit 16b may perform third-quadrant operation if the acquired secondary-side current Ior is a negative value. In addition, in step S22 in the previous Figures 34 and 36, step S32 in the previous Figure 35, and steps S53 and S54 in the previous Figure 37, only the secondary side command voltage Vo* of the secondary side command voltage Vo* and the secondary side command current Io* may be set based on the acquired secondary side terminal voltage Vor.

[0180] In step S11 of FIG. 20 , the setting unit 16a may set only the secondary-side command current of the secondary-side command voltage and the secondary-side command current based on the acquired secondary-side current. In step S12, the setting unit 16a may determine whether the acquired secondary-side terminal voltage is a positive voltage. In step S13, the setting unit 16a may determine whether the acquired secondary-side terminal voltage is a negative voltage. Note that, in steps S22 of FIGS. 34 and 36 , step S32 of FIG. 35 , and steps S53 and S54 of FIG. 37 , only the secondary-side command current of the secondary-side command voltage and the secondary-side command current may be set based on the acquired secondary-side current. Furthermore, in step S42 of FIG. 36 , instead of the secondary-side command voltage Vox*, it may be determined whether the secondary-side terminal voltage of the power converter corresponding to the low-voltage storage battery exceeds the upper limit voltage. The processing of step S42 does not have to be performed.

[0181] In step S10 in Fig. 20 , only the secondary terminal voltage and the secondary current may be acquired from among the secondary terminal voltage, the secondary current, the voltage of the storage battery 31, and the current of the storage battery 31. Also, instead of acquiring the secondary current, the current of the storage battery 31 may be acquired. Even in this case, it is possible to execute the control described in Fig. 20 .

[0182] 7 and 8, the control unit 16b may sequentially perform four patterns of operation, including the following two operations (j) and (k), as first-quadrant operation. Operation (j) is an operation in which the first and third switches S1 and S3 are turned on and the second and fourth switches S2 and S4 are turned off. Operation (k) is an operation in which the second and fourth switches S2 and S4 are turned on and the first and third switches S1 and S3 are turned off.

[0183] The control unit 16b may sequentially perform, as the third quadrant operation, four patterns of operation including the above-described operations (j) and (k) in addition to the operations shown in FIGS. 14 and 15 .

[0184] The switches constituting the power converter, such as the first to fourth conversion switches and the bidirectional switch, are not limited to N-channel MOSFETs and may be, for example, IGBTs. In this case, the first main terminal of each switch is the collector, and the second main terminal is the emitter. A freewheel diode is connected in antiparallel to each switch. In this embodiment, each of the pair of switch units is an IGBT and a freewheel diode.

[0185] The power storage unit included in each power storage module is not limited to a storage battery, but may be, for example, a large-capacity electric double layer capacitor, or both a storage battery and an electric double layer capacitor. The power storage unit may also be a fuel cell.

[0186] The power conversion system does not have to be configured as a storage battery module in which a storage battery, a power converter, and the like are integrated into a single package.

[0187] 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.

[0188] 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.

[0189] The following describes characteristic configurations extracted from the above-described embodiments. [Configuration 1] A power converter (40, 70, 100) applied to a system (10) including a power storage unit (31, 61, 91), comprising: a primary circuit (51) having a pair of primary terminals (41, 42, 71, 72, 101, 102) connected in parallel to the power storage unit; and a secondary circuit (52, 152, 252) having a pair of secondary terminals (43, 44, 73, 74, 103, 104) connected in series to the power storage unit, and capable of transmitting power between the primary circuit and the primary circuit, wherein the secondary circuit has a pair of switch units (QH1, QL1, QH2, QL2, RH1, RL1, RH2, RL2, T1a, T1b, T2a, T2b, UH1, UL1, UH2, UL2, UH3, UL3, UH4, UL4), a power converter according to configuration 1, wherein each of the pair of switch units has a predetermined blocking direction in which current flow is blocked when the switch unit is turned off, and the pair of switch units are connected in series so that the blocking directions are opposite to each other. [Configuration 2] The power converter according to configuration 1, wherein each of the pair of switch units has a predetermined current-carrying direction in which current flow is allowed in the opposite direction to the blocking direction regardless of whether the switch unit is on or off, in addition to the blocking direction, and the pair of switch units are connected in series so that the blocking directions are opposite to each other. [Configuration 3] The power converter according to configuration 1 or 2, wherein the system includes a plurality of the power storage units, and the power converter is provided corresponding to the plurality of power storage units, one of the secondary-side terminal pairs is connected to a positive or negative side of the corresponding power storage unit, and the other of the secondary-side terminal pair is connected to one of the external terminal pairs (11, 12) of the system, and the positive or negative side of the plurality of power storage units that is not connected to the secondary-side terminal pair is connected to the external terminal pair that is not connected to the secondary-side terminal pair.[Configuration 4] The power converter according to Configuration 1 or 2, wherein the storage unit is a target storage unit, and the system includes a non-target storage unit in addition to the target storage unit, one of the secondary-side terminal pair is connected to a positive electrode side or a negative electrode side of the target storage unit, and the other of the secondary-side terminal pair is connected to one of the external terminal pairs (11, 12) of the system, and one of the positive electrode side or the negative electrode side of the target storage unit that is not connected to the secondary-side terminal pair is connected to the other of the external terminal pair that is not connected to the secondary-side terminal pair, and the positive electrode side of the non-target storage unit is connected to the positive electrode side of the external terminal pair, and the negative electrode side of the non-target storage unit is connected to the negative electrode side of the external terminal pair. [Configuration 5] A control device (16) for a power converter (40, 70, 100), wherein the power converter is the power converter according to any one of configurations 1 to 4, and the control device for a power converter includes: a setting unit (16a) that sets one of the pair of switch units to a fixed-on switch that is fixed to on, and sets the other of the pair of switch units to a control switch that performs switching control, based on the polarity of the voltage of the secondary-side terminal pair; and a control unit (16b) that performs switching control of the control switch and a primary-side switch included in the primary-side circuit, so as to transfer power from one of the primary-side circuit and the secondary-side circuit to the other.[Configuration 6] A control device (16) for a power converter (40, 70, 100), wherein the power converter is the power converter according to Configuration 3, and includes: a setting unit (16a) that sets, in each of the plurality of power converters, one of the pair of switch units as a fixed-on switch that is fixed to on, and sets the other of the pair of switch units as a control switch that performs switching control, based on the polarity of the voltage of the secondary-side terminal pair; and a control unit (16b) that performs switching control of the control switch and a primary-side switch included in the primary-side circuit, in each of the plurality of power converters, so as to transfer power from one of the primary-side circuit and the secondary-side circuit to the other, wherein the setting unit selects a low-voltage power storage unit having the lowest output voltage from among the plurality of power storage units, and determines whether or not the voltage of the secondary-side terminal pair exceeds an upper limit voltage of the same polarity as the output voltage of the low-voltage power storage unit, in the power converter corresponding to the selected low-voltage power storage unit, a control device for a power converter, the control device setting the fixed-on switch and the control switch in the power converter corresponding to the selected low-voltage storage unit so that the direction in which a charging current of the low-voltage storage unit flows to the secondary-side circuit is the blocking direction; selecting a high-voltage storage unit having the highest output voltage among the plurality of storage units; when it is determined that the upper limit voltage is not exceeded, setting the fixed-on switch and the control switch in the power converter corresponding to the selected high-voltage storage unit so that the direction in which a charging current of the low-voltage storage unit flows to the secondary-side circuit is the blocking direction; and when it is determined that the upper limit voltage is exceeded, setting the fixed-on switch and the control switch in the power converter corresponding to the selected high-voltage storage unit so that the direction in which a discharging current of the high-voltage storage unit flows to the secondary-side circuit is the blocking direction.[Configuration 7] A control device (16) for a power converter (40, 70, 100), wherein the power converter is the power converter according to Configuration 3, comprising: a setting unit (16a) that sets, in each of the plurality of power converters, one of the pair of switch units as a fixed-on switch that is fixed to on, and sets the other of the pair of switch units as a control switch that performs switching control, based on the polarity of the voltage of the secondary-side terminal pair; and a control unit (16b) that performs switching control of the control switch and a primary-side switch included in the primary-side circuit, in each of the plurality of power converters, so as to transfer power from one of the primary-side circuit and the secondary-side circuit to the other, wherein the setting unit selects, from the plurality of power storage units, a low-voltage power storage unit having an output voltage lower than those of the other power storage units, and sets the fixed-on switch and the control switch in the power converter corresponding to the selected low-voltage power storage unit so that a direction in which a charging current of the low-voltage power storage unit flows to the secondary-side circuit is the blocking direction. [Configuration 8] A control device (16) for a power converter (40, 70, 100), wherein the power converter is the power converter according to Configuration 3, and includes: a setting unit (16a) that sets, in each of the plurality of power converters, one of the pair of switch units as a fixed-on switch that is fixed to on, and sets the other of the pair of switch units as a control switch that performs switching control, based on the polarity of the voltage of the secondary-side terminal pair; and a control unit (16b) that performs switching control of the control switch and a primary-side switch included in the primary-side circuit, in each of the plurality of power converters, so as to transfer power from one of the primary-side circuit and the secondary-side circuit to the other, wherein the setting unit selects, from the plurality of power storage units, a high-voltage power storage unit having a higher output voltage than the other power storage units, and sets the fixed-on switch and the control switch in the power converter corresponding to the selected high-voltage power storage unit so that a direction in which a discharge current of the high-voltage power storage unit flows to the secondary-side circuit is the blocking direction.[Configuration 9] The control device for a power converter according to any one of configurations 5 to 8, wherein the setting unit sets the fixed-on switch and the control switch such that a direction in which a charging current of the power storage unit flows to the secondary-side circuit is the blocking direction when the polarity of the voltage of the secondary-side terminal pair is the same as the polarity of the output voltage of the power storage unit, and the control unit performs the switching control so as to transfer power from the primary-side circuit to the secondary-side circuit. [Configuration 10] The control device for a power converter according to any one of configurations 5 to 9, wherein the setting unit sets the fixed-on switch and the control switch such that a direction in which a discharging current of the power storage unit flows to the secondary-side circuit is the blocking direction when the polarity of the voltage of the secondary-side terminal pair is different from the polarity of the output voltage of the power storage unit, and the control unit performs the switching control so as to transfer power from the secondary-side circuit to the primary-side circuit. [Configuration 11] The control device for a power converter according to any one of configurations 5 to 10, wherein the setting unit sets the fixed-on switch and the control switch so that a direction in which a discharging current of the power storage unit flows to the secondary-side circuit is the blocking direction when the polarity of the voltage of the secondary-side terminal pair is different from the polarity of the output voltage of the power storage unit, and the control unit performs the switching control so as to transfer power from the primary-side circuit to the secondary-side circuit. [Configuration 12] The control device for a power converter according to any one of configurations 5 to 11, wherein the setting unit sets the fixed-on switch and the control switch so that a direction in which a charging current of the power storage unit flows to the secondary-side circuit is the blocking direction when the polarity of the voltage of the secondary-side terminal pair is the same as the polarity of the output voltage of the power storage unit, and the control unit performs the switching control so as to transfer power from the secondary-side circuit to the primary-side circuit.

[0190] 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 converter (40, 70, 100) applied to a system (10) having a power storage unit (31, 61, 91), comprising: a primary circuit (51) having a pair of primary terminals (41, 42, 71, 72, 101, 102) connected in parallel to the power storage unit; and a secondary circuit (52, 152, 252) having a pair of secondary terminals (43, 44, 73, 74, 103, 104) connected in series to the power storage unit, and capable of transmitting power between the primary circuit and the secondary circuit, wherein the secondary circuit has a pair of switch units (QH1, QL1, QH2, QL2, RH1, RL1, RH2, RL2, T1a, T1b, T2a, T2b, UH1, UL1, UH2, UL2, UH3, UL3, UH4, UL4), A power converter in which each of the pair of switch units has a predetermined blocking direction in which current flow is blocked when the switch units are turned off, and the switch units are connected so that the blocking directions are opposite to each other.

2. A power converter as described in claim 1, wherein each of the pair of switch sections is defined, in addition to the blocking direction, with a current-carrying allowable direction in which current is allowed to flow in the opposite direction to the blocking direction regardless of whether the switch section is on or off, and the pair of switch sections are connected in series so that the blocking directions are opposite to each other.

3. The power converter according to claim 1, wherein the system comprises a plurality of the power storage units, the power converter is provided corresponding to the plurality of power storage units, one of the secondary side terminal pair is connected to the positive or negative side of the corresponding power storage unit, the other of the secondary side terminal pair is connected to one of the external terminal pairs (11, 12) of the system, and the positive or negative side of the plurality of power storage units that is not connected to the secondary side terminal pair is connected to the external terminal pair that is not connected to the secondary side terminal pair.

4. The power converter according to claim 1, wherein the storage unit is a target storage unit, the system includes an untargeted storage unit in addition to the target storage unit, one of the secondary-side terminal pair is connected to the positive or negative side of the target storage unit, and the other of the secondary-side terminal pair is connected to one of the external terminal pairs (11, 12) of the system, the positive or negative side of the target storage unit that is not connected to the secondary-side terminal pair is connected to the external terminal pair that is not connected to the secondary-side terminal pair, and the positive side of the untargeted storage unit is connected to the positive side of the external terminal pair, and the negative side of the untargeted storage unit is connected to the negative side of the external terminal pair.

5. A control device (16) for a power converter (40, 70, 100), wherein the power converter is a power converter as defined in any one of claims 1 to 4, and comprises: a setting unit (16a) that sets one of the pair of switch units to a fixed-on switch that is fixed to on, and sets the other of the pair of switch units to a control switch that performs switching control, based on the polarity of the voltage of the secondary-side terminal pair; and a control unit (16b) that performs switching control of the control switch and the primary-side switch of the primary-side circuit so as to transmit power from one of the primary-side circuit and the secondary-side circuit to the other.

6. A control device (16) for a power converter (40, 70, 100), wherein the power converter is the power converter according to claim 3, and comprises: a setting unit (16a) that sets one of the pair of switch units to a fixed-on switch that is fixed to on and sets the other of the pair of switch units to a control switch that performs switching control, based on the polarity of the voltage of the secondary-side terminal pair, in each of the plurality of power converters; and a control unit (16b) that performs switching control of the control switch and the primary-side switch of the primary-side circuit so as to transfer power from one of the primary-side circuit and the secondary-side circuit to the other, in each of the plurality of power converters, wherein the setting unit selects a low-voltage power storage unit having the lowest output voltage from the plurality of power storage units, and determines whether or not the voltage of the secondary-side terminal pair exceeds an upper limit voltage of the same polarity as the output voltage of the low-voltage power storage unit, in the power converter corresponding to the selected low-voltage power storage unit, a control device for a power converter, the control device setting the fixed-on switch and the control switch in the power converter corresponding to the selected low-voltage storage unit so that the direction in which a charging current of the low-voltage storage unit flows to the secondary-side circuit is the blocking direction; selecting a high-voltage storage unit having the highest output voltage among the plurality of storage units; when it is determined that the upper limit voltage is not exceeded, setting the fixed-on switch and the control switch in the power converter corresponding to the selected high-voltage storage unit so that the direction in which a charging current of the low-voltage storage unit flows to the secondary-side circuit is the blocking direction; and when it is determined that the upper limit voltage is exceeded, setting the fixed-on switch and the control switch in the power converter corresponding to the selected high-voltage storage unit so that the direction in which a discharging current of the high-voltage storage unit flows to the secondary-side circuit is the blocking direction.

7. A control device (16) for a power converter (40, 70, 100), wherein the power converter is the power converter defined in claim 3, and comprises: a setting unit (16a) that sets, in each of the plurality of power converters, one of the pair of switch units as a fixed-on switch that is fixed to on, and sets the other of the pair of switch units as a control switch that performs switching control, based on the polarity of the voltage of the secondary-side terminal pair; and a control unit (16b) that performs switching control of the control switch and the primary-side switch of the primary-side circuit so as to transfer power from one of the primary-side circuit and the secondary-side circuit to the other of the plurality of power converters, wherein the setting unit selects, from the plurality of power storage units, a low-voltage power storage unit having an output voltage lower than the other power storage units, and sets the fixed-on switch and the control switch in the power converter corresponding to the selected low-voltage power storage unit so that the direction in which a charging current of the low-voltage power storage unit flows to the secondary-side circuit is the blocked direction.

8. A control device (16) for a power converter (40, 70, 100), wherein the power converter is the power converter as defined in claim 3, comprising: a setting unit (16a) that sets, in each of the plurality of power converters, one of the pair of switch units as a fixed-on switch that is fixed to on, and sets the other of the pair of switch units as a control switch that performs switching control, based on the polarity of the voltage of the secondary-side terminal pair; and a control unit (16b) that performs switching control of the control switch and the primary-side switch of the primary-side circuit so as to transfer power from one of the primary-side circuit and the secondary-side circuit to the other of the plurality of power converters, wherein the setting unit selects, from the plurality of power storage units, a high-voltage power storage unit having a higher output voltage than the other power storage units, and sets the fixed-on switch and the control switch in the power converter corresponding to the selected high-voltage power storage unit so that the direction in which a discharge current of the high-voltage power storage unit flows to the secondary-side circuit is the blocked direction.

9. The control device for a power converter according to claim 5, wherein the setting unit sets the fixed-on switch and the control switch so that the direction in which the charging current of the storage unit flows into the secondary circuit is the blocked direction when the polarity of the voltage of the secondary side terminal pair is the same polarity as the output voltage of the storage unit, and the control unit performs the switching control so as to transfer power from the primary side circuit to the secondary side circuit.

10. The control device for a power converter according to claim 5, wherein the setting unit sets the fixed-on switch and the control switch so that the direction in which the discharge current of the storage unit flows into the secondary circuit is the blocked direction when the polarity of the voltage of the secondary side terminal pair is different from the polarity of the output voltage of the storage unit, and the control unit performs the switching control so as to transfer power from the secondary circuit to the primary circuit.

11. The control device for a power converter according to claim 5, wherein the setting unit sets the fixed-on switch and the control switch so that the direction in which the discharge current of the storage unit flows into the secondary circuit is the blocking direction when the polarity of the voltage of the secondary side terminal pair is different from the polarity of the output voltage of the storage unit, and the control unit performs the switching control so as to transfer power from the primary side circuit to the secondary side circuit.

12. The control device for a power converter according to claim 5, wherein the setting unit sets the fixed-on switch and the control switch so that the direction in which the charging current of the storage unit flows into the secondary circuit is the blocked direction when the polarity of the voltage of the secondary side terminal pair is the same polarity as the output voltage of the storage unit, and the control unit performs the switching control so as to transfer power from the secondary circuit to the primary circuit.

13. A program applied to a system (10) including a power storage unit (31, 61, 91) and a power converter (40, 70, 100), wherein the power converter includes: a primary circuit (51) having a pair of primary terminals (41, 42, 71, 72, 101, 102) connected in parallel to the power storage unit; and a secondary circuit (52, 152, 252) having a pair of secondary terminals (43, 44, 73, 74, 103, 104) connected in series to the power storage unit and capable of transmitting power between the primary circuit and the power storage unit; the secondary-side circuit has a pair of switch units (QH1, QL1, QH2, QL2, RH1, RL1, RH2, RL2, T1a, T1b, T2a, T2b, UH1, UL1, UH2, UL2, UH3, UL3, UH4, UL4), each of the pair of switch units has a predetermined blocking direction in which current flow is blocked when turned off, and the switch units are connected so that the blocking directions are opposite to each other, and the program causes a computer (16) to execute processes including: a setting process of setting one of the pair of switch units as a fixed-on switch that is fixed to on, and setting the other of the pair of switch units as a control switch that performs switching control, based on the polarity of the voltage of the secondary-side terminal pair; and a control process of performing switching control of the control switch and a primary-side switch included in the primary-side circuit, so as to transfer power from one of the primary-side circuit and the secondary-side circuit to the other.

14. A control method for a power converter applied to a system (10) including a power storage unit (31, 61, 91) and a power converter (40, 70, 100), wherein the power converter includes: a primary circuit (51) having a pair of primary terminals (41, 42, 71, 72, 101, 102) connected in parallel to the power storage unit; and a secondary circuit (52, 152, 252) having a pair of secondary terminals (43, 44, 73, 74, 103, 104) connected in series to the power storage unit and capable of transmitting power between the primary circuit and the power storage unit; the secondary-side circuit has a pair of switch units (QH1, QL1, QH2, QL2, RH1, RL1, RH2, RL2, T1a, T1b, T2a, T2b, UH1, UL1, UH2, UL2, UH3, UL3, UH4, UL4), each of the pair of switch units has a predetermined blocking direction in which current flow is blocked when turned off, and the switch units are connected so that the blocking directions are opposite to each other, a setting step of setting one of the pair of switch units as a fixed-on switch that is fixed to on, and setting the other of the pair of switch units as a control switch that performs switching control, based on the polarity of a voltage of the secondary-side terminal pair, and a control step of performing switching control of the control switch and a primary-side switch included in the primary-side circuit, so as to transfer power from one of the primary-side circuit and the secondary-side circuit to the other.

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