Power supply system and control program

Abstract

To provide a power supply system that includes a storage battery and a conversion circuit and reduces loss during power supply.SOLUTION: A power supply system (10) includes a storage battery (31, 61), and a conversion circuit (40, 70) that converts power input from the storage battery to a primary terminal pair (41, 42, 71, 72) by driving a switching element, and outputs the converted power from a secondary terminal pair (47, 48, 77, 78). A cathode and an anode of the storage battery are connected to the primary terminal pair of the conversion circuit, and the storage battery is connected in series to the secondary terminal pair of the conversion circuit. The power supply system includes a connection maintenance circuit (49, 79) that maintains the secondary terminal pair in a connected state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power supply system. [Background technology]

[0002] For example, there is a storage battery management system that includes multiple storage batteries and a converter that controls the charge / discharge current of each storage battery (see Patent Document 1). The storage battery management system described in Patent Document 1 aims to improve the efficiency of the entire system by distributing a total current command value for the multiple storage batteries to each converter according to the state of charge (SOC) of the storage batteries, the output voltage of the storage batteries, the total charge / discharge power amount of the storage batteries, the temperature characteristics of the storage batteries, and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-207790 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the storage battery management system described in Patent Document 1, in order to output power from the storage batteries, the converter (conversion circuit) connected to each storage battery must be switched on and off. Therefore, even in situations where it is not necessary to step up or down the voltage of the storage batteries when outputting power from the storage batteries, switching loss occurs in the converter, and there is still room for improvement in terms of increasing the efficiency of the system.

[0005] The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to reduce losses during power supply in a power supply system including a storage battery and a conversion circuit. [Means for solving the problem]

[0006] The first means for solving the above problem is A power supply system (10, 210) including a storage battery (31, 61, 91) and a conversion circuit (40, 70, 100) that converts power input from the storage battery to a pair of primary terminals (41, 42, 71, 72) by driving switching elements (43-46, 54, 55, 143-146) and outputs the converted power from a pair of secondary terminals (47, 48, 77, 78), a positive electrode and a negative electrode of the storage battery are respectively connected to the primary terminal pair of the conversion circuit, and the storage battery is connected in series to the secondary terminal pair of the conversion circuit; The secondary side terminal pair is connected to the connection maintaining circuit (36, 37, 49, 66, 67, 79, 96, 97).

[0007] According to the above configuration, the power supply system includes a storage battery and a conversion circuit that converts power input from the storage battery to a primary terminal pair by driving a switching element and outputs the power from a secondary terminal pair. Therefore, the power supply system can convert the power input from the storage battery to the primary terminal pair by driving a switching element in the conversion circuit and output the power from the secondary terminal pair. When converting power by the conversion circuit, switching losses (turn-on loss and turn-off loss) of the switching elements occur. The switching losses are losses that occur with the switching drive (turn-on drive and turn-off drive) of the switching elements.

[0008] Here, the positive and negative electrodes of the storage battery are connected to the primary terminal pair of the conversion circuit, respectively, and the storage battery is connected in series to the secondary terminal pair of the conversion circuit. With this configuration, the sum of the output voltage Vb of the storage battery and the output voltage Vo of the conversion circuit becomes the output voltage Vm of the storage battery module. Therefore, compared to a storage battery module in which a storage battery is connected in parallel to the secondary terminal pair of the conversion circuit, the output voltage Vo required of the conversion circuit when the output voltage Vm is required of the storage battery module can be reduced. Therefore, the rated voltage of the conversion circuit can be reduced, and the rated capacity of the conversion circuit can be reduced, thereby making it possible to miniaturize the conversion circuit.

[0009] Furthermore, the power supply system includes a connection maintenance circuit that maintains the secondary terminal pair in a connected state. Therefore, in a situation where it is not necessary to boost the voltage higher than the voltage of the storage battery when outputting power from the storage battery, the secondary terminal pair connected in series to the storage battery is maintained in a connected state by the connection maintenance circuit (hereinafter referred to as "conduction mode"), so that power can be directly output from the storage battery. Therefore, power can be output without continuous switching drive (turn-on drive and turn-off drive) of the switching element for power conversion, and switching loss of the switching element can be suppressed. As a result, the efficiency of the power supply system can be increased.

[0010] In the second means, the connection maintenance circuit is configured by a secondary circuit (49, 79) of the conversion circuit connected to the secondary terminal pair, and maintains the secondary terminal pair in a connected state by the secondary circuit via a secondary switching element (54, 55) that is the switching element included in the secondary circuit. With this configuration, it is not necessary to add a new circuit as a connection maintenance circuit to the power supply system, and the secondary circuit of the conversion circuit can be used as the connection maintenance circuit. Furthermore, the main loss in the conduction mode can be limited to the conduction loss of the secondary switching element of the conversion circuit, or the conduction loss of the anti-parallel diode included in the secondary switching element. Note that the conduction loss is a loss that occurs due to conduction to a switching element, a diode, etc.

[0011] In a third means, the connection maintaining circuit includes a bypass circuit (36, 66, 96) that bypasses the conversion circuit and connects the secondary side terminal pair, and a bypass switch (37, 67, 97) that disconnects and connects the bypass circuit, and the secondary side terminal pair is maintained in a connected state by the bypass switch. With this configuration, power can be directly output from the storage battery by maintaining the bypass circuit in a connected state by the bypass switch. Then, the main loss in the conduction mode can be limited to the conduction loss of the bypass switch. For this reason, for example, by adopting a switch with a smaller conduction loss than the secondary side switching element of the conversion circuit as the bypass switch, the loss when outputting power from the storage battery can be further suppressed.

[0012] In the fourth means, a storage battery module (30, 60, 90) is formed by the storage battery, the conversion circuit, and the connection maintenance circuit, and the storage battery module is connected to a power supply bus (11, 12).The storage battery module is provided with a control unit (16b) that executes a conduction mode in which the connection maintenance circuit of the storage battery module maintains the secondary side terminal pair in a connected state, on condition that the difference between a bus voltage that is the voltage of the power supply bus and an output voltage of the storage battery of the storage battery module is smaller than a voltage threshold.

[0013] According to the above configuration, a storage battery module is configured by the storage battery, the conversion circuit, and the connection maintenance circuit, and the storage battery module is connected to a power supply bus. Therefore, power can be supplied from the storage battery module to the power supply bus. Note that the power supply bus is a power path (common power path) shared to connect multiple circuits, devices, and equipment in a power supply system and exchange power between them.

[0014] The control unit executes a conduction mode in which the connection maintenance circuit of the storage battery module maintains the secondary side terminal pair in a connected state, on condition that the difference between the bus voltage, which is the voltage of the power supply bus, and the output voltage of the storage battery of the storage battery module is smaller than a voltage threshold. Therefore, when the difference between the bus voltage and the output voltage of the storage battery is smaller than the voltage threshold, i.e., when it is not necessary to boost the voltage higher than the voltage of the storage battery when outputting power from the storage battery module, the control unit can execute the conduction mode to directly output power from the storage battery. On the other hand, when the difference between the bus voltage and the output voltage of the storage battery is not smaller than the voltage threshold, i.e., when it is necessary to boost the output voltage of the storage battery module (to boost it higher than the voltage of the storage battery) when outputting power from the storage battery module, the control unit can refrain from executing the conduction mode.

[0015] When the battery module is outputting power to the power supply bus, the output voltage of the battery module is equal to the output voltage of the battery even if the output voltage of the battery module is not boosted by the conversion circuit. Therefore, when the battery module is outputting power to the power supply bus, the bus voltage is always equal to or higher than the output voltage of the battery in the battery module.

[0016] A fifth means includes a plurality of the storage battery modules, the plurality of the storage battery modules being connected in parallel to the power supply bus, and the control unit selects the storage battery module having the highest output voltage of the storage battery as the storage battery module to be placed into the conduction mode among the plurality of the storage battery modules.

[0017] According to the above configuration, the power supply system includes a plurality of the storage battery modules, and the plurality of the storage battery modules are connected in parallel to the power supply bus. Therefore, power can be supplied from the plurality of the storage battery modules to the power supply bus. The control unit selects a storage battery module having the highest output voltage of the storage battery as the storage battery module to be placed in the conduction mode among the plurality of the storage battery modules. Therefore, when the conduction mode is executed to directly output power from the storage battery, the bus voltage can be kept as high as possible.

[0018] A sixth means includes a plurality of the storage battery modules, the plurality of the storage battery modules being connected in parallel to the power supply bus, and the control unit selects the storage battery module to be placed in the conduction mode from among the plurality of the storage battery modules, starting from the storage battery module having the higher output voltage of the storage battery.

[0019] According to the above configuration, the control unit selects the storage battery module to be set to the conduction mode from among the plurality of storage battery modules in order from the storage battery module having the higher output voltage of the storage battery, thereby making it possible to supply power from a greater number of storage batteries to the power supply bus while suppressing a drop in bus voltage when the conduction mode is executed to directly output power from the storage batteries.

[0020] In a seventh aspect, the control unit adjusts the output voltage of the conversion circuit in a storage battery module in which the difference between the bus voltage and the output voltage of the storage battery in the storage battery module is not smaller than the voltage threshold so that the difference between the bus voltage and the output voltage of the storage battery module is smaller than the voltage threshold. With this configuration, in a storage battery module in which the difference between the bus voltage and the output voltage of the storage battery in the storage battery module is not smaller than the voltage threshold, the output voltage of the storage battery module can be increased by adjusting the output voltage of the conversion circuit in the storage battery module. Therefore, power can be supplied to the power supply bus even from a storage battery module whose output voltage of the storage battery is low.

[0021] An eighth means includes a plurality of the storage battery modules, the plurality of the storage battery modules being connected in parallel to the power supply bus, and the control unit selects the storage battery module to be placed in the conduction mode and adjusts the state of the storage battery of the selected storage battery module so that the difference between the bus voltage and the output voltage of the storage battery of the selected storage battery module is maintained smaller than the voltage threshold.

[0022] According to the above configuration, the control unit selects the storage battery module to be put into the conduction mode. Therefore, power can be directly output from the storage battery of the selected storage battery module on condition that the difference between the bus voltage and the output voltage of the storage battery of the selected storage battery module is smaller than a voltage threshold. Furthermore, the control unit adjusts the state of the storage battery of the selected storage battery module so as to maintain a state in which the difference between the bus voltage and the output voltage of the storage battery of the selected storage battery module is smaller than the voltage threshold. Therefore, the conduction mode can be continued while maintaining the output voltage of the storage battery of the selected storage battery module.

[0023] A ninth means includes a plurality of the storage battery modules, the plurality of storage battery modules being connected in parallel to the power supply bus, and when any of the storage battery modules is in the conduction mode, the control unit places the storage battery module that is not in the conduction mode in the conduction mode, on condition that the difference between the output voltage of the storage battery of the storage battery module in the conduction mode and the output voltage of the storage battery of the storage battery module that is not in the conduction mode is smaller than the voltage threshold value.

[0024] When any of the storage battery modules is in the conduction mode, the output voltage of the storage battery of the storage battery module in the conduction mode is equal to the bus voltage. According to the above configuration, when it is not necessary to boost the voltage higher than the voltage of the storage battery when outputting power from the storage battery of the storage battery module not in the conduction mode, the storage battery module not in the conduction mode can be set to the conduction mode to directly output power from the storage battery.

[0025] In the tenth means, when the difference between the output voltage of the storage battery of the storage battery module in the conduction mode and the output voltage of the storage battery of the storage battery module not in the conduction mode is not smaller than the voltage threshold, the control unit charges the storage battery of the storage battery module not in the conduction mode from the storage battery of the storage battery module in the conduction mode. With this configuration, the charge amount of the storage battery of the storage battery module in the conduction mode can be reduced to lower the output voltage, and the charge amount of the storage battery of the storage battery module not in the conduction mode can be increased to raise the output voltage. Therefore, the difference between the output voltage of the storage battery of the storage battery module in the conduction mode and the output voltage of the storage battery of the storage battery module not in the conduction mode can be reduced, making it easier to put the storage battery module not in the conduction mode into the conduction mode.

[0026] In an eleventh means, the control unit charges the storage battery of the storage battery module that is not in the conduction mode from the storage battery of the storage battery module that is in the conduction mode by lowering the output voltage of the conversion circuit of the storage battery module that is not in the conduction mode below the current output voltage.

[0027] According to the above configuration, by lowering the output voltage of the conversion circuit of the storage battery module not in the conduction mode below the current output voltage, the output voltage of the storage battery module not in the conduction mode can be lowered below the output voltage of the storage battery of the storage battery module in the conduction mode. Therefore, the storage battery of the storage battery module not in the conduction mode can be charged from the storage battery of the storage battery module in the conduction mode.

[0028] The twelfth measure is: a storage battery module (30, 60, 90) including a storage battery (31, 61, 91) and a conversion circuit (40, 70, 100) that converts power input from the storage battery to a pair of primary side terminals (41, 42, 71, 72) by driving switching elements (43-46, 54, 55, 143-146) and outputs the power from a pair of secondary side terminals (47, 48, 77, 78), is connected to a power supply bus (11, 12), a positive electrode and a negative electrode of the storage battery are respectively connected to the pair of primary side terminals of the conversion circuit, the storage battery is connected in series to the pair of secondary side terminals of the conversion circuit, and a connection maintaining circuit (36, 37, 49, 66, 67, 79) that maintains the pair of secondary side terminals in a connected state, A computer (16) is caused to execute a conduction mode in which the connection maintenance circuit of the storage battery module maintains the secondary side terminal pair in a connected state, on condition that the difference between a bus voltage, which is the voltage of the power supply bus, and an output voltage of the storage battery of the storage battery module is smaller than a voltage threshold.

[0029] According to the above configuration, by causing a computer to execute a control program applied to the power supply system, it is possible to achieve the same advantageous effects as those of the fourth aspect. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a circuit diagram of a power supply system according to a first embodiment. [Diagram 2] FIG. 4 is a circuit diagram showing an example of a conversion circuit. [Diagram 3] 5 is a flowchart showing a procedure for executing a conduction mode in the first embodiment. [Figure 4] FIG. 4 is a circuit diagram showing a state in which the first storage battery module of the first embodiment is in a conduction mode. [Diagram 5] 4 is a circuit diagram showing a state in which a first storage battery module and a second storage battery module of the first embodiment are in a conduction mode. FIG. [Figure 6] 4 is a circuit diagram showing a state in which a first storage battery module, a second storage battery module, and a third storage battery module of the first embodiment are in a conduction mode. FIG. [Figure 7] FIG. 4 is a diagram showing losses generated in the storage battery modules of a comparative example and the first embodiment. [Figure 8] FIG. 11 is a circuit diagram of a power supply system according to a second embodiment. [Figure 9] 10 is a flowchart showing a procedure for executing a conduction mode in a second embodiment. [Figure 10] FIG. 11 is a circuit diagram showing a state in which a first storage battery module according to a second embodiment is in a conduction mode. [Figure 11] FIG. 11 is a circuit diagram showing a state in which a first storage battery module and a second storage battery module according to a second embodiment are in a conduction mode. [Figure 12] FIG. 11 is a circuit diagram showing a state in which a first storage battery module, a second storage battery module, and a third storage battery module of a second embodiment are in a conduction mode. [Figure 13] FIG. 13 is a diagram showing generated losses in a comparative example and a second embodiment. [Figure 14] FIG. 11 is a circuit diagram of another modified example of the power supply system. [Figure 15]FIG. 11 is a circuit diagram of another modified example of the power supply system. [Figure 16] FIG. 13 is a circuit diagram of a modified example of the conversion circuit. [Figure 17] FIG. 13 is a circuit diagram of another modified example of the conversion circuit. [Figure 18] FIG. 11 is a circuit diagram of a modified example of the storage battery module. [Figure 19] FIG. 11 is a circuit diagram of another modified example of the storage battery module. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] (First embodiment) Hereinafter, a first embodiment embodied in a power supply system for supplying power to a load will be described with reference to the drawings.

[0032] 1, power supply system 10 includes buses 11 and 12 (power supply buses), a first storage battery module 30, a second storage battery module 60, a voltage sensor 13, a current sensor 19, an ECU (Electronic Control Unit) 16, etc. The positive side of the buses is referred to as bus 11, and the negative side of the buses is referred to as bus 12. Bus 12 is grounded.

[0033] A first storage battery module 30 (storage battery module), a second storage battery module 60 (storage battery module), a load 21, and a voltage sensor 13 are connected in parallel to the buses 11 and 12. The storage battery modules 30 and 60 input and output power to the buses 11 and 12. The load 21 inputs power from the buses 11 and 12, or inputs and outputs power to the buses 11 and 12. The voltage sensor 13 detects a bus voltage Vbus, which is a voltage between the buses 12 and 11. The current sensor 19 detects a current flowing through the bus 12 (load 21).

[0034] The load 21 is, for example, a combination of an inverter and a motor generator (MG) (motor unit with inverter), an electric heater, a DC-DC converter, or the like. The motor generator (MG) drives, for example, an electric vehicle by power supplied from the inverter, and generates electric power by a rotational force applied from the electric vehicle. The inverter converts electric power between the buses 11, 12 and the MG. The electric heater generates heat by a high voltage supplied from the buses 11, 12, for example, and warms the interior of the vehicle and the battery. The DC-DC converter converts, for example, DC power supplied from the buses 11, 12 and supplies DC power, or converts DC power supplied from a solar panel or the like and supplies DC power to the buses 11, 12. The load 21 may be a single load or a plurality of loads.

[0035] The first storage battery module 30 includes a first storage battery 31, a first current sensor 33, a first drive circuit 35, a first conversion circuit 40, relays 40a, 40b, etc. The first storage battery 31 (storage battery) is a high-voltage secondary battery, such as a lithium-ion battery or a nickel-metal hydride battery, and may be of any type. The first current sensor 33 (current sensor) detects a current flowing through the first storage battery 31. A detection value by the first current sensor 33 is input to the ECU 16 and is used, for example, to calculate the state of charge (SOC) of the first storage battery 31. The first drive circuit 35 (drive circuit) drives a switching element (described later) included in the first conversion circuit 40 to turn on and off. The first drive circuit 35 is controlled by the ECU 16. The relays 40a, 40b connect and disconnect the storage battery module 30 to and from the buses 11, 12, respectively. The first storage battery 31 (storage battery) may be a secondary battery that is not a high voltage battery.

[0036] The first conversion circuit 40 (conversion circuit) includes a primary side positive terminal 41 and a negative terminal 42, which are a primary side terminal pair, and a secondary side positive terminal 47 and a negative terminal 48, which are a secondary side terminal pair. The negative electrode of the first storage battery 31 is connected to the bus 12. The primary side positive terminal 41 is connected to the positive electrode of the first storage battery 31, and the primary side negative terminal 42 is connected to the negative electrode of the first storage battery 31. In addition, the secondary side negative terminal 48 is connected to the positive electrode of the first storage battery 31. The secondary side positive terminal 47 is connected to the bus 11. That is, the positive electrode and the negative electrode of the first storage battery 31 are connected to the primary side terminal pair 41, 42 of the first conversion circuit 40, respectively, and the first storage battery 31 is connected in series to the secondary side terminal pair 47, 48 of the first conversion circuit 40. The first conversion circuit 40 converts the power input from the first storage battery 31 to the primary side terminal pair 41, 42 and outputs it from the secondary side terminal pair 47, 48. A secondary side circuit 49 provided in the first conversion circuit 40 will be described later. The first conversion circuit 40 is a bidirectional conversion circuit that can also convert the power input to the secondary side terminal pair 47, 48 and output it from the primary side terminal pair 41, 42.

[0037] The second storage battery module 60 has a similar configuration to the first storage battery module 30, and includes a second storage battery 61 (storage battery), a second current sensor 63 (current sensor), a second drive circuit 65 (drive circuit), a second conversion circuit 70, relays 70a, 70b, etc. The second conversion circuit 70 (conversion circuit) has a similar configuration to the first conversion circuit 40, and includes a primary side positive terminal 71 and a negative terminal 72, which are a primary side terminal pair, and a secondary side positive terminal 77 and a negative terminal 78, which are a secondary side terminal pair. Since the connection manner of these is also similar to that of the first storage battery module 30, the above description of the first storage battery module 30 is used. A secondary side circuit 79 included in the second conversion circuit 70 will be described later. Although the first storage battery module 30 and the second storage battery module 60 have configurations having similar functions, the ratings and withstand voltages of the respective configurations may be different from each other.

[0038] FIG. 2 shows an example of the first conversion circuit 40. The first conversion circuit 40 is a well-known center-tapped insulated DC-DC converter. The first conversion circuit 40 includes a primary circuit and a secondary circuit 49. The first conversion circuit 40 includes switching elements 43 to 46, 54, and 55, smoothing capacitors 50 and 57, a transformer 53, a reactor 56, voltage sensors 51 and 59, and current sensors 52 and 58. The switching elements 43 to 46, 54, and 55 are, for example, FETs and IGBTs (Insulated Gate Bipolar Transistors). The switching elements 43 to 46 form a full bridge circuit. A connection point between the switching element 43 and the switching element 44 and a connection point between the switching element 45 and the switching element 46 are connected to both ends of the primary coil of the transformer 53, respectively. The switching elements 54 and 55 are connected between both ends of the secondary coil of the transformer 53 and the reactor 56, respectively. The voltage sensor 51 detects the voltage between the negative terminal 42 and the positive terminal 41 on the primary side, that is, the output voltage Vb of the first storage battery 31 (the input voltage Vi of the first conversion circuit 40). The current sensor 52 detects the input current Ii which is a current input to the primary side circuit. The voltage sensor 59 detects the voltage between the negative terminal 48 and the positive terminal 47 on the secondary side, that is, the output voltage Vo of the first conversion circuit 40. The current sensor 58 detects the current flowing through the reactor 56, that is, the output current Io of the first conversion circuit 40. The detection values ​​of the voltage sensors 51, 59 and the current sensors 52, 58 are input to the ECU 16. The secondary side circuit 49 (connection maintaining circuit) includes the secondary side coil of the transformer 53, the switching elements 54, 55, the reactor 56, and paths connecting these to the secondary side terminal pair 47, 48.

[0039] The ECU 16 (control device) is configured as a microcomputer (computer) including, for example, a CPU, a ROM, a RAM, an input / output interface, etc. The ECU 16 controls the states of the relays 40a, 40b, 70a, 70b and the state of the load 21. The ECU 16 executes a control program applied to the power supply system 10, thereby realizing the functions of a bus voltage setting unit 16a, a control unit 16b, etc.

[0040] The bus voltage setting unit 16a sets a bus voltage request value Vbus*, which is a voltage that is requested to be supplied from the buses 11 and 12 to the load 21. The bus voltage setting unit 16a sets the bus voltage request value Vbus* based on the state of the load 21.

[0041] The control unit 16b controls the output voltages Vo1 and Vo2 of the conversion circuits 40 and 70 so that the output voltages Vm1 and Vm2 of the storage battery modules 30 and 60 become the bus voltage request value Vbus* (approach the bus voltage request value Vbus*). For example, the control unit 16b controls the switching elements 43-46, 54, and 55 based on the detection values ​​of the voltage sensors 51 and 59 and the current sensors 52 and 58 to control the first output voltage Vo1 of the first conversion circuit 40 to the first output voltage request value Vo1*. In detail, the first output voltage request value Vo1* is set to a voltage obtained by subtracting the first output voltage Vb1 of the first storage battery 31 from the bus voltage request value Vbus* (Vo1*=Vbus*-Vb1). Similarly, the control unit 16b controls the second output voltage Vo2 of the second conversion circuit 70 to the second output voltage request value Vo2*. Specifically, the second output voltage request value Vo2* is set to a voltage obtained by subtracting the second output voltage Vb2 of the second storage battery 61 from the bus voltage request value Vbus* (Vo2*=Vbus*−Vb2).

[0042] In addition, when power is being output from the storage battery module 30(60) to the buses 11 and 12, even if the conversion circuit 40(70) does not boost the output voltage Vm1(Vm2) of the storage battery 31(61) higher than the output voltage Vb1(Vb2), the output voltage Vm1(Vm2) of the storage battery module 30(60) becomes equal to the output voltage Vb1(Vb2) of the storage battery 31(61). Therefore, when power is being output from the storage battery module 30(60) to the buses 11 and 12, the bus voltage Vbus is always equal to or higher than the output voltage Vb1(Vb2) of the storage battery 31(61) of the storage battery module 30(60).

[0043] Depending on the bus voltage request value Vbus* and the charge amount of the storage batteries 31, 61, the bus voltage Vbus and the output voltages Vb1, Vb2 of the storage batteries 31, 61 may become close to each other, and a situation may arise in which it is not necessary to boost the output voltages Vm1, Vm2 of the storage battery modules 30, 60 by the conversion circuits 40, 70 when outputting power from the storage battery modules 30, 60. In this case, if the switching elements 43-46, 54, 55 of the conversion circuits 40, 70 are continuously switched to output power from the storage battery modules 30, 60, turn-on losses and turn-off losses (switching losses) of the switching elements 43-46, 54, 55, as well as conduction losses occur.

[0044] Therefore, in this embodiment, the control unit 16b (ECU 16) executes a conduction mode in which the secondary side terminal pair 47, 48 (77, 78) is maintained in a connected state by the secondary side circuit 49 (79) of the storage battery module 30 (60) on the condition that the difference between the bus voltage Vbus and the output voltage Vb1 (Vb2) of the storage battery 31 (61) of the storage battery module 30 (60) is smaller than the voltage threshold Vx. In more detail, the switching elements 54, 55 (secondary side switching elements) included in the secondary side circuit 49 (79) are maintained in an on state, thereby maintaining the secondary side positive terminal 47 (77) and negative terminal 48 (78), which are the secondary side terminal pair, in a connected state. At this time, all of the switching elements 43 to 46 on the primary side of the conversion circuit (40, 70) of the storage battery module 30 (60) are maintained in an off state.

[0045] 3 is a flowchart showing a procedure for executing the conduction mode. This series of processes is executed by the control unit 16b of the ECU 16 in a state in which the conversion circuits 40, 70 of the storage battery modules 30, 60 are driven to output power to the buses 11, 12. Note that three or more storage battery modules may be connected in parallel to the buses 11, 12.

[0046] First, among the storage battery modules that have not yet been selected by the process of S10, the storage battery module with the highest storage battery output voltage Vb is selected (S10). When this series of processes starts, all storage battery modules have not yet been selected. If there is no storage battery module that has not yet been selected (if all storage battery modules have been selected), this series of processes ends (END).

[0047] Next, it is determined whether the difference (Vbus-Vb) between the bus voltage Vbus and the output voltage Vb of the storage battery of the selected storage battery module is smaller than the voltage threshold Vx (S11). The bus voltage Vbus is detected by the voltage sensor 13. The voltage threshold Vx is, for example, a value at which the bus voltage Vbus and the output voltage Vb of the storage battery can be considered to be equal (almost equal), and is a value at which inrush current and circulating current can be suppressed from flowing in a plurality of storage battery modules. In this determination, if it is determined that the difference (Vbus-Vb) between the bus voltage Vbus and the output voltage Vb of the storage battery of the selected storage battery module is smaller than the voltage threshold Vx (S11: YES), all of the switching elements 54, 55 on the secondary side of the conversion circuit of the selected storage battery module are maintained in the ON state (S12). At this time, all of the switching elements 43 to 46 on the primary side of the conversion circuit of the selected storage battery module are maintained in the OFF state.

[0048] Next, it is determined whether the bus voltage Vbus is lower than the bus voltage request value Vbus* (S13). If it is determined that the bus voltage Vbus is lower than the bus voltage request value Vbus* (S13: YES), this series of processes is terminated (END). On the other hand, if it is determined that the bus voltage Vbus is not lower than the bus voltage request value Vbus* (S13: NO), the process is executed again from S10. That is, the storage battery module to be placed in the conductive mode among the multiple storage battery modules is selected in order starting from the storage battery module with the highest output voltage.

[0049] Furthermore, if it is determined in the process of S11 that the difference (Vbus-Vb) between the bus voltage Vbus and the output voltage Vb of the storage battery of the selected storage battery module is not smaller than the voltage threshold Vx (S11: NO), the output voltage Vo of the conversion circuit of the selected storage battery module is adjusted so that the difference (Vbus-Vm) between the bus voltage Vbus and the output voltage Vm of the selected storage battery module becomes smaller than the voltage threshold Vx (S14). Then, the process is executed again from S10.

[0050] 4 to 6 show a state in which the conduction mode is executed in the power supply system 10 including the first storage battery module 30, the second storage battery module 60, and the third storage battery module 90. The output voltages Vm1 (Vb1+Vo1), Vm2 (Vb2+Vo2), and Vm3 (Vb3+Vo3) of the storage battery modules 30, 60, and 90 are all equal to the bus voltage Vbus.

[0051] 4, the difference between the bus voltage Vbus and the first output voltage Vb1 of the first storage battery 31 is smaller than the voltage threshold Vx, the difference between the bus voltage Vbus and the second output voltage Vb2 of the second storage battery 61 is equal to or greater than the voltage threshold Vx, and the difference between the bus voltage Vbus and the third output voltage Vb3 of the third storage battery 91 is equal to or greater than the voltage threshold Vx. In this case, the first storage battery module 30 is in the conductive mode, and the storage battery modules 60 and 90 are performing boost operations by the conversion circuits 70 and 100, respectively. As a result, switching loss is reduced in the first conversion circuit 40 of the first storage battery module 30.

[0052] 5, the difference between the bus voltage Vbus and the first output voltage Vb1 of the first storage battery 31 is smaller than the voltage threshold Vx, the difference between the bus voltage Vbus and the second output voltage Vb2 of the second storage battery 61 is smaller than the voltage threshold Vx, and the difference between the bus voltage Vbus and the third output voltage Vb3 of the third storage battery 91 is equal to or larger than the voltage threshold Vx. In this case, the storage battery modules 30, 60 are in the conduction mode, and the third storage battery module 90 performs a boost operation by the third conversion circuit 100. As a result, switching losses are reduced in the conversion circuits 40, 70 of the storage battery modules 30, 60, respectively.

[0053] 6, the difference between the bus voltage Vbus and the first output voltage Vb1 of the first storage battery 31 is smaller than the voltage threshold Vx, the difference between the bus voltage Vbus and the second output voltage Vb2 of the second storage battery 61 is smaller than the voltage threshold Vx, and the difference between the bus voltage Vbus and the third output voltage Vb3 of the third storage battery 91 is smaller than the voltage threshold Vx. In this case, the storage battery modules 30, 60, and 90 are in the conductive mode. Therefore, the switching losses are reduced in the conversion circuits 40, 70, and 100 of the storage battery modules 30, 60, and 90, respectively.

[0054] FIG. 7 is a diagram showing losses in the storage battery modules of the comparative example and the present embodiment. The comparative example shows losses when, for example, in the first storage battery module 30, the switching elements 43-46, 54, 55 of the first conversion circuit 40 are turned on and off to output the first output voltage Vm1. Turn-on losses and turn-off losses occur in the switching elements 43-46, 54, 55, and conduction losses occur in the switching elements 43-46, 54, 55. The present embodiment shows losses when, for example, the first storage battery module 30 is in a conduction mode to output the first output voltage Vm1. In the present embodiment, the turn-on losses and turn-off losses of the switching elements 43-46, 54, 55 can be reduced, and only the conduction losses of the switching elements 54, 55 occur. As a result, the losses in the comparative example can be reduced by 3 / 4, and the losses that occur are 1 / 4 of the losses in the comparative example.

[0055] The present embodiment described above in detail has the following advantages.

[0056] The positive and negative electrodes of the storage batteries 31, 61 are connected to the primary terminal pairs 41, 42, 71, 72 of the conversion circuits 40, 70, respectively, and the storage batteries 31, 61 are connected in series to the secondary terminal pairs 47, 48, 77, 78 of the conversion circuits 40, 70, respectively. With this configuration, the output voltages Vm1, Vm2 of the storage battery modules 30, 60 are the sums of the output voltages Vb1, Vb2 of the storage batteries 31, 61 and the output voltages Vo1, Vo2 of the conversion circuits 40, 70, respectively. Therefore, compared to a storage battery module in which the storage batteries 31, 61 are connected in parallel to the secondary terminal pairs 47, 48, 77, 78 of the conversion circuits 40, 70, respectively, it is possible to reduce the output voltages Vo1, Vo2 required of the conversion circuits 40, 70 when the output voltages Vm1, Vm2 are required of the storage battery modules 30, 60, respectively. Therefore, the rated voltage of the conversion circuits 40, 70 can be lowered, and therefore the rated capacity of the conversion circuits 40, 70 can be reduced, allowing the conversion circuits 40, 70 to be made smaller.

[0057] The power supply system 10 includes a connection maintaining circuit (secondary circuit 49, 79) that maintains the secondary terminal pairs 47, 48, 77, 78 in a connected state. Therefore, in a situation where it is not necessary to boost the voltage higher than the voltage of the storage batteries 31, 61 when outputting power from the storage batteries 31, 61, a conduction mode is executed in which the secondary terminal pairs 47, 48, 77, 78 connected in series to the storage batteries 31, 61, respectively, are maintained in a connected state by the connection maintaining circuit, so that power can be directly output from the storage batteries 31, 61. Therefore, power can be output without continuous switching drive (turn-on drive and turn-off drive) of the switching elements 43-46, 54, 55 for power conversion, and switching loss of the switching elements 43-46, 54, 55 can be suppressed. As a result, the power supply system 10 can be made highly efficient.

[0058] The connection maintenance circuit is configured by the secondary circuit 49 of the first conversion circuit 40 connected to the secondary terminal pairs 47, 48, respectively, and maintains the secondary terminal pairs 47, 48 in a connected state by the secondary circuit 49 via the secondary switching elements 54, 55 included in the secondary circuit 49. The connection maintenance circuit is also configured by the secondary circuit 79 of the second conversion circuit 70 connected to the secondary terminal pairs 77, 78, and maintains the secondary terminal pairs 77, 78 in a connected state by maintaining the secondary switching elements 54, 55 included in the secondary circuit 79 in an on state. With this configuration, there is no need to add a new circuit as a connection maintenance circuit to the power supply system 10, and the secondary circuits 49, 79 of the conversion circuits 40, 70 can be used as the connection maintenance circuit. Furthermore, the main loss in the conduction mode can be the conduction loss of the secondary-side switching elements 54, 55 of the conversion circuits 40, 70 alone, or the conduction loss of the anti-parallel diodes included in the secondary-side switching elements 54, 55 alone.

[0059] The control unit 16b executes a conduction mode in which the secondary side terminal pairs 47, 48, 77, 78 are maintained in a connected state by the secondary side circuits 49, 79 of the storage battery modules 30, 60, 90, on the condition that the difference between the bus voltage Vbus, which is the voltage of the buses 11, 12, and the output voltages Vb1, Vb2, Vb3 of the storage batteries 31, 61, 91 of the storage battery modules 30, 60, 90 is smaller than the voltage threshold Vx. Therefore, when the difference between the bus voltage Vbus and the output voltages Vb1, Vb2, Vb3 of the storage batteries 31, 61, 91 is smaller than the voltage threshold Vx, i.e., when it is not necessary to boost the voltage higher than the voltage of the storage batteries 31, 61, 91 when outputting power from the storage battery modules 30, 60, 90, the conduction mode is executed, so that power can be directly output from the storage batteries 31, 61, 91. On the other hand, if the difference between the bus voltage Vbus and the output voltages Vb1, Vb2, Vb3 of the storage batteries 31, 61, 91 is not smaller than the voltage threshold Vx, i.e., if it is necessary to boost the voltage higher than the voltage of the storage batteries 31, 61, 91 when outputting power from the storage battery modules 30, 60, 90, the conduction mode can be prevented from being executed.

[0060] The power supply system 10 includes a plurality of storage battery modules 30, 60, 90, which are connected in parallel to the buses 11, 12. This allows power to be supplied from the plurality of storage battery modules 30, 60, 90 to the buses 11, 12. The control unit 16b then selects the storage battery module with the highest output voltage of the storage batteries 31, 61, 91 as the storage battery module to be placed in the conduction mode among the plurality of storage battery modules 30, 60, 90. This allows the bus voltage Vbus to be kept as high as possible when the conduction mode is executed to directly output power from the storage batteries.

[0061] The control unit 16b selects the storage battery module to be placed in the conduction mode from among the multiple storage battery modules 30, 60, 90 in order from the storage battery module with the higher output voltage of the storage batteries 31, 61, 91. Therefore, when the conduction mode is executed to directly output power from the storage batteries, a drop in the bus voltage Vbus is suppressed, and power can be supplied to the buses 11, 12 from a greater number of storage batteries.

[0062] The control unit 16b adjusts the output voltages Vo1, Vo2, Vo3 of the conversion circuits 40, 70, 100 so that the difference between the bus voltage Vbus and the output voltages Vb1, Vb2, Vb3 of the storage batteries 31, 61, 91 of the storage battery modules 30, 60, 90 is smaller than the voltage threshold Vx. With this configuration, in a storage battery module where the difference between the bus voltage Vbus and the output voltages Vb1, Vb2, Vb3 of the storage batteries 31, 61, 91 of the storage battery modules 30, 60, 90 is not smaller than the voltage threshold Vx, the output voltage of the storage battery module can be increased by adjusting the output voltage of the conversion circuit of the storage battery module. Therefore, power can be supplied to the buses 11, 12 even from storage battery modules where the output voltage of the storage batteries 31, 61, 91 is low.

[0063] The above-mentioned advantageous effects can be achieved by causing the ECU 16 (computer) to execute the conduction mode of the control program applied to the power supply system 10.

[0064] Second embodiment The second embodiment will be described below, focusing on the differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be repeated.

[0065] As shown in FIGS. 8 and 10, in this embodiment, the storage battery modules 30, 60, and 90 include bypasses 36, 66, and 96 and bypass relays 37, 67, and 97, respectively, as connection maintaining circuits.

[0066] For example, the bypass 36 (detour circuit) bypasses the first conversion circuit 40 and connects the positive terminal 47 and the negative terminal 48 on the secondary side, which are a secondary side terminal pair. The bypass 36 is provided with a bypass relay 37. The bypass relay 37 (detour circuit switch) is a relay with a smaller conduction loss than the switching elements 54, 55 of the first conversion circuit 40, and is formed of, for example, an SJ-MOSFET (Super Junction - Metal Oxide Semiconductor Field Effect Transistor). The bypass relay 37 is controlled by the control unit 16b to cut off and connect the bypass 36. In the first storage battery module 30, the bypass relay 37 is maintained in an on state (connected state) to maintain the positive terminal 47 and the negative terminal 48 on the secondary side in a connected state. That is, in a state in which the bypass 36 is connected by the bypass relay 37, the first storage battery 31 is connected to the buses 11, 12 via the bypass 36 without via the first conversion circuit 40. Note that the bypass relay 37 may be another semiconductor relay whose conduction loss is equal to or less than the conduction loss of the switching elements 54, 55. The bypass relay 37 is not limited to a semiconductor relay, and may be a mechanical relay whose conduction loss is equal to or less than the conduction loss of the switching elements 54, 55. The same applies to the bypasses 66, 96 (bypass circuits) and the bypass relays 67, 97 (bypass circuit switches).

[0067] The control unit 16b (ECU 16) executes a conduction mode in which the secondary side terminal pair 47, 48 (77, 78) is maintained in a connected state by the bypass 36 (66) and the bypass relay 37 (67) of the storage battery module 30 (60), for example, on the condition that the difference between the bus voltage Vbus and the output voltage Vb1 (Vb2) of the storage battery 31 (61) of the storage battery module 30 (60) is smaller than the voltage threshold Vx. In more detail, the bypass relay 37 (67) is maintained in an on state, thereby maintaining the secondary side positive terminal 47 (77) and negative terminal 48 (78), which are the secondary side terminal pair, in a connected state. At this time, all of the switching elements 43 to 46, 54, 55 of the conversion circuit 40 (70) of the storage battery module 30 (60) are maintained in an off state.

[0068] Fig. 9 is a flowchart showing a procedure for executing the conduction mode. This series of processes is executed by the control unit 16b of the ECU 16 in a state in which the conversion circuits 40, 70, 100 of the storage battery modules 30, 60, 90 are driven to output power to the buses 11, 12. In the process of the flowchart of Fig. 9, the process of S12 in the flowchart of Fig. 3 is changed to the process of S22, and the other processes are the same as those in the flowchart of Fig. 3. The same processes as those in the flowchart of Fig. 3 are denoted by the same step numbers S and the explanation thereof is incorporated herein.

[0069] In the process of S22, the bypass relay of the selected storage battery module is maintained in the ON state (S22), while all of the switching elements 43 to 46, 54, and 55 of the conversion circuit of the selected storage battery module are maintained in the OFF state.

[0070] 10 to 12 show a state in which the conduction mode is executed in a case where the power supply system 10 includes a first storage battery module 30, a second storage battery module 60, and a third storage battery module 90. The output voltages Vm1 (Vb1+Vo1), Vm2 (Vb2+Vo2), and Vm3 (Vb3+Vo3) of the storage battery modules 30, 60, and 90 are all equal to the bus voltage Vbus.

[0071] 10, the difference between the bus voltage Vbus and the first output voltage Vb1 of the first storage battery 31 is smaller than the voltage threshold Vx, the difference between the bus voltage Vbus and the second output voltage Vb2 of the second storage battery 61 is equal to or greater than the voltage threshold Vx, and the difference between the bus voltage Vbus and the third output voltage Vb3 of the third storage battery 91 is equal to or greater than the voltage threshold Vx. In this case, the bypass relay 37 of the first storage battery module 30 is turned on, and the conversion circuits 70 and 100 of the storage battery modules 60 and 90 are performing boost operations, respectively. For this reason, switching loss and conduction loss are reduced in the first conversion circuit 40 of the first storage battery module 30. Note that conduction loss occurs in the bypass relay 37.

[0072] 11, the difference between the bus voltage Vbus and the first output voltage Vb1 of the first storage battery 31 is smaller than the voltage threshold Vx, the difference between the bus voltage Vbus and the second output voltage Vb2 of the second storage battery 61 is smaller than the voltage threshold Vx, and the difference between the bus voltage Vbus and the third output voltage Vb3 of the third storage battery 91 is equal to or larger than the voltage threshold Vx. In this case, the bypass relays 37, 67 of the storage battery modules 30, 60 are turned on, and the third storage battery module 90 performs a boost operation by the third conversion circuit 100. Therefore, the switching loss and the conduction loss are reduced in the conversion circuits 40, 70 of the storage battery modules 30, 60, respectively. Note that conduction loss occurs in the bypass relays 37, 67.

[0073] 12, the difference between the bus voltage Vbus and the first output voltage Vb1 of the first storage battery 31 is smaller than the voltage threshold Vx, the difference between the bus voltage Vbus and the second output voltage Vb2 of the second storage battery 61 is smaller than the voltage threshold Vx, and the difference between the bus voltage Vbus and the third output voltage Vb3 of the third storage battery 91 is smaller than the voltage threshold Vx. In this case, the bypass relays 37, 67, and 97 of the storage battery modules 30, 60, and 90 are turned on. Therefore, the switching loss and the conduction loss are reduced in the conversion circuits 40, 70, and 100 of the storage battery modules 30, 60, and 90, respectively. Note that the conduction loss occurs in the bypass relays 37, 67, and 97.

[0074] FIG. 13 is a diagram showing losses in the storage battery modules of the comparative example and the present embodiment. The comparative example shows losses when, for example, in the first storage battery module 30, the switching elements 43-46, 54, 55 of the first conversion circuit 40 are turned on and off to output the first output voltage Vm1. Turn-on losses and turn-off losses occur in the switching elements 43-46, 54, 55, and conduction losses occur in the switching elements 43-46, 54, 55. The present embodiment shows losses when, for example, the bypass relay 37 of the first storage battery module 30 is turned on to output the first output voltage Vm1. In the present embodiment, the turn-on losses, turn-off losses, and conduction losses of the switching elements 43-46, 54, 55 can be reduced. And, the conduction loss of the bypass relay 37 occurs, which is smaller than the conduction loss of the switching elements 54, 55. As a result, the loss of the comparative example can be reduced by 4 / 5, and the generated loss is 1 / 5 of the loss of the comparative example.

[0075] In addition to the same advantages as the first embodiment, this embodiment has the following advantages.

[0076] By keeping the bypass relay 37, 67, 97 of the bypass 36, 66, 96 in the on state, i.e., by keeping the bypass 36, 66, 96 connected by the bypass relay 37, 67, 97, it is possible to directly output power from the storage battery 31, 61, 91. In addition, the main loss in the conduction mode can be the conduction loss of the bypass relay 37, 67, 97.

[0077] The bypass relay 37, 67, 97 is a relay having a smaller conduction loss than the switching elements 54, 55 on the secondary side of the conversion circuit 40, 70, 100, so that the loss when outputting power from the storage battery 31, 61, 91 can be further reduced.

[0078] When the control unit 16b executes the conduction mode to maintain the bypass relays 37, 67, 97 in the on state (connected state), the control unit 16b may maintain the switching elements 54, 55 on the secondary side of the conversion circuits 40, 70, 100 in the on state (connected state). With this configuration, the conduction loss of the storage battery modules 30, 60, 90 can be further reduced.

[0079] The first and second embodiments can be modified as follows: The same parts as those in the first and second embodiments are denoted by the same reference numerals and the description thereof will be incorporated herein.

[0080] The control unit 16b may select a storage battery module to be placed in the conduction mode, and adjust the charge amount (state) of the storage battery of the selected storage battery module so that the difference between the bus voltage Vbus and the output voltage Vb of the storage battery of the selected storage battery module is maintained smaller than the voltage threshold Vx. In this case, the storage battery module to be selected and placed in the conduction mode is not limited to the storage battery module with the highest storage battery output voltage Vb, as long as the difference between the bus voltage Vbus and the output voltage Vb of the storage battery of the storage battery module is smaller than the voltage threshold Vx. As an example of a mode (configuration) for adjusting the charge amount (SOC) of the storage battery of the selected storage battery module, the storage battery of the selected storage battery module may be charged from the storage battery of an unselected storage battery module.

[0081] According to the above configuration, the control unit 16b selects a storage battery module to be put into the conduction mode. Therefore, it is possible to directly output power from the storage battery of the selected storage battery module on condition that the difference between the bus voltage Vbus and the output voltage Vb of the storage battery of the selected storage battery module is smaller than the voltage threshold Vx. Furthermore, the control unit 16b adjusts the charge amount of the storage battery of the selected storage battery module so that the difference between the bus voltage Vbus and the output voltage Vb of the storage battery of the selected storage battery module is maintained to be smaller than the voltage threshold Vx. Therefore, it is possible to continue the conduction mode while maintaining the output voltage Vb of the storage battery of the selected storage battery module.

[0082] When any of the storage battery modules is in the conduction mode, the control unit 16b may set the storage battery module that is not in the conduction mode to the conduction mode on the condition that the difference between the output voltage Vb of the storage battery of the storage battery module in the conduction mode and the output voltage Vb of the storage battery of the storage battery module that is not in the conduction mode is smaller than the voltage threshold value Vx. In a state where the storage battery module is in the conduction mode, the output voltage Vb of the storage battery of the storage battery module in the conduction mode and the bus voltage Vbus are the same. Therefore, the output voltage Vb of the storage battery of the storage battery module in the conduction mode may be compared with the output voltage Vb of the storage battery of the storage battery module that is not in the conduction mode to determine whether or not to execute the conduction mode. According to the above configuration, when it is not necessary to boost the voltage higher than the voltage of the storage battery when outputting power from the storage battery of the storage battery module that is not in the conduction mode, the storage battery module that is not in the conduction mode can be set to the conduction mode to directly output power from the storage battery.

[0083] Furthermore, when the difference between the output voltage Vb of the storage battery of the storage battery module in the conduction mode and the output voltage Vb of the storage battery of the storage battery module not in the conduction mode is not smaller than the voltage threshold Vx, the control unit 16b may charge the storage battery of the storage battery module not in the conduction mode from the storage battery of the storage battery module in the conduction mode. Specifically, the control unit 16b charges the storage battery of the storage battery module not in the conduction mode from the storage battery of the storage battery module in the conduction mode by lowering the output voltage Vo of the conversion circuit of the storage battery module not in the conduction mode to a value lower than the current output voltage Vo. According to the above configuration, the charge amount of the storage battery of the storage battery module in the conduction mode can be reduced to lower the output voltage Vb, and the charge amount of the storage battery of the storage battery module not in the conduction mode can be increased to raise the output voltage Vb. Therefore, the difference between the output voltage Vb of the storage battery of the storage battery module in the conduction mode and the output voltage Vb of the storage battery of the storage battery module not in the conduction mode can be reduced, making it easier to put the storage battery module not in the conduction mode into the conduction mode. In addition, the difference between the output voltage Vb of the storage battery of the storage battery module in the conduction mode and the output voltage Vb of the storage battery of the storage battery module not in the conduction mode can also be reduced by stopping the output of power from the storage battery module that is not in the conduction mode.

[0084] By the bus voltage setting unit 16a lowering the bus voltage request value Vbus* below the current bus voltage request value Vbus*, the difference between the bus voltage Vbus and the output voltage Vb of the storage battery of the storage battery module can also be made smaller than the voltage threshold Vx.

[0085] The load 21 may be, for example, a combination of an inverter and a motor generator (MG) (motor unit with inverter), and two or more of these may be connected in parallel to the buses 11 and 12. In this case, the number of storage battery modules connected to the buses 11 and 12 may be increased as the number of motor units with inverter increases.

[0086] As shown in FIG. 14, the load 28 may be connected in parallel to the second storage battery 61 (storage battery) of the second storage battery module 60 (storage battery module). In this case, the charge amount of the second storage battery 61 can be reduced by supplying power from the second storage battery 61 to the load 28. This makes it easier to reduce the second output voltage Vb2 of the second storage battery 61 of the second storage battery module 60 to a value lower than the first output voltage Vb1 of the first storage battery 31 of the first storage battery module 30. This makes it easier to perform control to add the second output voltage Vo2 of the second conversion circuit 70 to the second output voltage Vb2 of the second storage battery 61 of the second storage battery module 60, and makes it easier to adjust the second output voltage Vm2 of the second storage battery module 60 to the bus voltage request value Vbus*. 15, the power supply system 210 may include a path 211 that connects a connection point N7 between the third conversion circuit 100 of the third storage battery module 90 and the relay 90a, and a connection point N8 between the first storage battery 31 of the first storage battery module 30 and the relay 40b. Furthermore, the power supply system 210 may include a path 213 that connects a connection point N9 between the first conversion circuit 40 of the first storage battery module 30 and the relay 40a, and a connection point N10 between the second storage battery 61 of the second storage battery module 60 and the relay 70b. The path 211 is provided with a relay 212 (switch) that disconnects and connects the path 211. The path 213 is provided with a relay 214 (switch) that disconnects and connects the path 213. The relays 212 and 214 are controlled by the ECU 16. The paths 211 and 213 and the relays 212 and 214 form a switching circuit. That is, the power supply system 210 may include three or more storage battery modules (a plurality of storage battery modules), and the switching circuit may switch the three or more storage battery modules between series connection and parallel connection with the buses 11 and 12. As shown in Fig. 16, in the first conversion circuit 40 (conversion circuit), the switching elements 54, 55 in Fig. 2 may be connected between the transformer 53 and the negative terminal 48. With such a configuration, it is possible to achieve the same effects as the first conversion circuit 40 in Fig. 2. The same is true for the second conversion circuit 70 and the third conversion circuit 100, etc. (conversion circuits).

[0087] 17, the first conversion circuit 40 (conversion circuit) may be a well-known isolated DC-DC converter including a non-center-tapped transformer 153 and a secondary full-bridge circuit composed of switching elements 143 to 146. The switching elements 143 to 146 are, for example, FETs and IGBTs (Insulated Gate Bipolar Transistors). The switching elements 143 to 146 are controlled by the ECU 16. The same applies to the second conversion circuit 70 and the third conversion circuit 100 (conversion circuit).

[0088] A resonant DC-DC converter may be used as the first conversion circuit 40 (conversion circuit). A non-isolated DC-DC converter such as a buck converter may be used as the first conversion circuit 40 (conversion circuit). The same applies to the second conversion circuit 70 and the third conversion circuit 100 (conversion circuit).

[0089] The storage battery modules 30, 60 may be configured as shown in FIG. 18. That is, the positive electrode of the first storage battery 31 is connected to the bus 11. The positive electrode of the first storage battery 31 is connected to the positive terminal 41 of the primary side of the first conversion circuit 40, and the negative electrode of the first storage battery 31 is connected to the negative terminal of the first storage battery 31. The positive terminal 47 of the secondary side of the first conversion circuit 40 is connected to the negative terminal of the first storage battery 31. The negative terminal 48 of the secondary side of the first conversion circuit 40 is connected to the bus 12. In this case, the positive and negative electrodes of the first storage battery 31 are connected to the primary terminal pair 41, 42 of the first conversion circuit 40, respectively, and the first storage battery 31 is connected in series to the secondary terminal pair 47, 48 of the first conversion circuit 40. With such a configuration, the same effects as those of the first embodiment can be achieved. The same applies to the second storage battery module 60, the third storage battery module 90, etc. (storage battery modules).

[0090] 19, in addition to the configuration of FIG. 18, the first storage battery module 30 may include a bypass 36 and a bypass relay 37, and the second storage battery module 60 may include a bypass 66 and a bypass relay 67. In this case as well, when the bypass 36 (66) is connected by the bypass relay 37 (67), the storage battery 31 (61) is connected to the buses 11, 12 via the bypass 36 (66) without via the conversion circuit 40 (70). With such a configuration, it is possible to achieve the same effects as those of the second embodiment.

[0091] At least one of the functions of the bus voltage setting unit 16a and the control unit 16b of the ECU 16 can be realized by, for example, a power control ECU (Electronic Control Unit) that controls the power of the electric vehicle, or a vehicle control ECU (host ECU) that controls the electric vehicle in an integrated manner. In addition, when the power supply system 10 is used as, for example, a stationary power source, the functions of the bus voltage setting unit 16a and the control unit 16b of the ECU 16 can be realized by a stationary power source control ECU (control device) that controls the stationary power source.

[0092] The ECU 16 and the method described herein may be implemented by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions (instructions) embodied in a computer program. Alternatively, the ECU 16 and the method described herein may be implemented by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the ECU 16 and the method described herein may be implemented by one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. Also, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by the computer.

[0093] The above-described embodiments and modifications may be combined to the extent possible. [Explanation of symbols]

[0094] 10...power supply system, 30...first storage battery module, 31...first storage battery, 36...bypass, 37...bypass relay, 40...first conversion circuit, 41...positive terminal (primary side terminal pair), 42...negative terminal (primary side terminal pair), 43...switching element, 44...switching element, 45...switching element, 46...switching element, 47...positive terminal (secondary side terminal pair), 48...negative terminal (secondary side terminal pair), 49...secondary side circuit , 54...switching element, 55...switching element, 60...second storage battery module, 61...second storage battery, 66...bypass, 67...bypass relay, 70...second conversion circuit, 71...positive terminal (primary side terminal pair), 72...negative terminal (primary side terminal pair), 77...positive terminal (secondary side terminal pair), 78...negative terminal (secondary side terminal pair), 79...secondary side circuit, 90...third storage battery module, 91...third storage battery, 100...third conversion circuit.

Claims

1. A power supply system (10, 210) including a storage battery (31, 61, 91) and a conversion circuit (40, 70, 100) that converts power input from the storage battery to a primary side terminal pair (41, 42, 71, 72) by driving switching elements (43-46, 54, 55, 143-146) and outputs the converted power from a secondary side terminal pair (47, 48, 77, 78), a positive electrode and a negative electrode of the storage battery are respectively connected to the primary terminal pair of the conversion circuit, and the storage battery is connected in series to the secondary terminal pair of the conversion circuit; A power supply system including a connection maintaining circuit (36, 37, 49, 66, 67, 79, 96, 97) that maintains the secondary side terminal pairs in a connected state.

2. 2. The power supply system according to claim 1, wherein the connection maintaining circuit is configured by a secondary circuit (49, 79) of the conversion circuit connected to the secondary terminal pair, and maintains the secondary terminal pair in a connected state by the secondary circuit via a secondary switching element (54, 55) that is the switching element included in the secondary circuit.

3. 2. The power supply system according to claim 1, wherein the connection maintenance circuit includes a bypass circuit (36, 66, 96) that bypasses the conversion circuit and connects the secondary terminal pair, and a bypass switch (37, 67, 97) that interrupts and connects the bypass circuit, and the secondary terminal pair is maintained in a connected state by the bypass switch.

4. The storage battery, the conversion circuit, and the connection maintenance circuit constitute a storage battery module (30, 60, 90), The battery module is connected to a power supply bus (11, 12), The power supply system according to any one of claims 1 to 3, further comprising a control unit (16b) that executes a conduction mode in which the connection maintenance circuit of the storage battery module maintains the secondary side terminal pair in a connected state, on condition that a difference between a bus voltage that is the voltage of the power supply bus and an output voltage of the storage battery of the storage battery module is smaller than a voltage threshold value.

5. A storage battery module according to the present invention includes: A plurality of the battery modules are connected in parallel to the power supply bus; The power supply system according to claim 4 , wherein the control unit selects, as the storage battery module to be placed in the conduction mode from among the plurality of storage battery modules, a storage battery module having a highest output voltage of the storage battery.

6. A storage battery module according to the present invention includes: A plurality of the battery modules are connected in parallel to the power supply bus; The power supply system according to claim 4 , wherein the control unit selects, as the storage battery module to be placed in the conduction mode from among the plurality of storage battery modules, the storage battery module having the highest output voltage.

7. 7. The power supply system according to claim 6, wherein the control unit adjusts the output voltage of the conversion circuit in a storage battery module in which a difference between the bus voltage and the output voltage of the storage battery of the storage battery module is not smaller than the voltage threshold so that the difference between the bus voltage and the output voltage of the storage battery module becomes smaller than the voltage threshold.

8. A storage battery module according to the present invention includes: A plurality of the battery modules are connected in parallel to the power supply bus; 5. The power supply system according to claim 4, wherein the control unit selects the storage battery module to be placed in the conduction mode and adjusts the state of the storage battery of the selected storage battery module so that a difference between the bus voltage and an output voltage of the storage battery of the selected storage battery module is maintained smaller than the voltage threshold.

9. A storage battery module according to the present invention includes: A plurality of the battery modules are connected in parallel to the power supply bus; 5. The power supply system according to claim 4, wherein when any of the storage battery modules is in the conduction mode, the control unit places the storage battery module that is not in the conduction mode in the conduction mode, on condition that a difference between an output voltage of the storage battery of the storage battery module in the conduction mode and an output voltage of the storage battery of the storage battery module that is not in the conduction mode is smaller than the voltage threshold value.

10. 10. The power supply system according to claim 9, wherein the control unit charges the storage battery of the storage battery module that is not in the conduction mode from the storage battery of the storage battery module that is in the conduction mode when a difference between an output voltage of the storage battery of the storage battery module that is in the conduction mode and an output voltage of the storage battery of the storage battery module that is not in the conduction mode is not smaller than the voltage threshold value.

11. 11. The power supply system according to claim 10, wherein the control unit charges the storage battery of the storage battery module that is not in the conduction mode from the storage battery of the storage battery module that is in the conduction mode by lowering the output voltage of the conversion circuit of the storage battery module that is not in the conduction mode below a current output voltage.

12. a storage battery module (30, 60, 90) including a storage battery (31, 61, 91) and a conversion circuit (40, 70, 100) that converts power input from the storage battery to a primary side terminal pair (41, 42, 71, 72) by driving switching elements (43-46, 54, 55, 143-146) and outputs the power from a secondary side terminal pair (47, 48, 77, 78), is connected to a power supply bus (11, 12), positive and negative electrodes of the storage battery are respectively connected to the primary side terminal pair of the conversion circuit, the storage battery is connected in series to the secondary side terminal pair of the conversion circuit, and the power supply system (10, 210) includes a connection maintaining circuit (36, 37, 49, 66, 67, 79) that maintains the secondary side terminal pair in a connected state, A control program that causes a computer (16) to execute a conduction mode in which the connection maintenance circuit of the storage battery module maintains the secondary side terminal pair in a connected state, on condition that a difference between a bus voltage, which is the voltage of the power supply bus, and an output voltage of the storage battery of the storage battery module is smaller than a voltage threshold.

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