Power supply control device and power supply system

Abstract

Power supply control device (30) to be used in a power supply system comprising: a variety of electricity storage devices (12, 13); and a switching unit comprising a plurality of switching devices (21 to 25) provided at electrical paths leading to the electricity storage devices, and configured to switch a state of the plurality of electricity storage devices between a parallel state in which the plurality of electricity storage devices are connected in parallel to each other and a series state in which the plurality of electricity storage devices are connected in series to each other, wherein the plurality of electricity storage devices comprises a first electricity storage device (12) whose positive side is connected to a low-voltage load (14) in a low-voltage system in the series connection state, and a second electricity storage device (13) whose positive side is connected to a high-voltage load (15, 16) in a high-voltage system in the series connection state, and the power supply control device comprises: a capacity procurement unit configured to procure the respective remaining electrical capacities of the multitude of electricity storage facilities; and a current control unit configured, in a case where the state of the plurality of electricity storage devices is the parallel-connected state, to i) control charging and discharging currents for each of the electricity storage devices by adjusting resistance values ​​of variable resistance units present in the electrical paths leading to the electricity storage devices, based on the remaining electrical capacities of the electricity storage devices procured by the capacity procurement unit, such that a difference between the remaining electrical capacity of the first electricity storage device and a remaining electrical capacity of the second electricity storage device becomes a desired amount, and ii) adjust the resistance values ​​of the variable resistance units such thatthat the remaining electrical capacity of the first electricity storage device is greater than the remaining electrical capacity of the second electricity storage device.

Description

Cross-reference to related registration

[0001] The present application is based on the earlier Japanese patent application number 2016-134005 (JP 2018 -7 479 A), which was filed on 6 July 2016, the description of which is incorporated by reference. [Technical field]

[0002] The present disclosure relates to a power supply control device to be used in a power supply system comprising a plurality of electricity storage devices, and to the power supply system. [Background of the invention]

[0003] A conventional technology for switching the state of a power supply device comprising a plurality of batteries between a state in which the plurality of batteries are connected in parallel and a state in which the plurality of batteries are connected in series, corresponding to a power machine operating state, is known (see, for example, Patent Document 1). Specifically, in a power machine automatic starting system, while a power machine is in operation, the state of the respective batteries is changed to a state in which the batteries are connected in parallel by using a relay as a connection switching device, with the respective batteries being charged by a generator.Furthermore, upon restarting after the engine has been automatically stopped, the state of the individual batteries is switched to a series-connected state using a relay, supplying power to a starting device or starter motor. With the configuration described above, a smooth engine start is then achieved and battery degradation is prevented. [Citation list][Patent publication]

[0004] [PTL 1] JP 2003-155968 A [Summary of the invention]

[0005] In a system that allows switching between a parallel and a series connection of the multitude of batteries, as described above, a difference in the resistance values ​​of the power supply paths between the batteries arises because the switching devices, such as relays and switches, are provided on the respective power supply paths leading to the multitude of batteries, and because there is a difference in the number of relays and switches on the power supply paths between a series and a parallel connection state. Consequently, a difference in the charging and discharging currents flowing through the respective batteries occurs, resulting in a variation in the remaining electrical capacity (state of charge or SOC) between the respective batteries.Then, if the state of charge (SOC) varies between the respective batteries, charging is limited due to a battery with a higher SOC during charging, and discharging is limited due to a battery with a lower SOC during discharging, causing inconvenience that the application areas of the respective batteries cannot be used to a sufficient extent.

[0006] The present disclosure has been made in view of the problems described above, and is mainly directed to the provision of a power supply control device that can suppress a variation in the capacities of the respective electricity storage devices and thus makes it possible to carry out suitable charging and discharging of the respective electricity storage devices, and a power supply system.

[0007] A power supply control device according to the present disclosure is used in a power supply system comprising a plurality of electricity storage devices and a switching unit comprising a plurality of switching devices provided at electrical paths leading to the electricity storage devices, and configured to switch a state of the plurality of electricity storage devices between a state in which the plurality of electricity storage devices are connected in parallel and a state in which the plurality of electricity storage devices are connected in series, wherein the plurality of electricity storage devices comprises a first electricity storage device, the positive side of which is connected to a low-voltage load in a low-voltage system in the series-connected state, and a second electricity storage device.whose positive side is connected to a high-voltage load in a high-voltage system in the series-connected state. The power supply control device then comprises a capacity procurement unit configured to procure the respective remaining electrical capacities of the plurality of electricity storage devices, and a current control unit configured, in a case where one state of the plurality of electricity storage devices is the parallel-connected state, to control charging and discharging currents for each of the electricity storage devices by adjusting resistance values ​​of variable resistance units present in electrical paths leading to the respective electricity storage devices, based on the remaining electrical capacities of the electricity storage devices procured by the capacity procurement unit.so that the difference between the remaining electrical capacity of the first electricity storage device and the remaining electrical capacity of the second electricity storage device becomes a desired amount.

[0008] In the power supply system comprising the multitude of electricity storage devices whose state can be switched between series and parallel connection, and in which the positive side of the first electricity storage device is connected to the low-voltage load in the low-voltage system in the series connection, and the positive side of the second electricity storage device is connected to the high-voltage load in the high-voltage system in the series connection, it can be taken into account that magnitudes of discharge currents between the first electricity storage device and the second electricity storage device are different in the series connection, which increases the difference in the remaining electrical capacities (SOCs).

[0009] With regard to this point, in the configuration described above, when the state of the multitude of electricity storage devices is the parallel circuit state, the charging and discharging currents for each of the electricity storage devices are controlled by adjusting the resistance values ​​of the variable resistance units present in the electrical paths leading to the respective electricity storage devices, based on the remaining electrical capacities of the respective batteries, so that the difference between the remaining electrical capacity of the first electricity storage device and the remaining electrical capacity of the second electricity storage device becomes a desired amount.In this case, when the respective electricity storage devices are connected in parallel, a desired amount of the difference in the remaining electrical capacitances is intentionally provided between the first and second electricity storage devices in anticipation that the state of each device will subsequently switch to the series connection state. This prevents the difference in the remaining electrical capacitances between the respective electricity storage devices from increasing excessively, even when power is supplied to the respective electrical loads in the low-voltage and high-voltage systems in the series connection state.As a result, even in the case where the state of the respective electricity storage device is switched between the series circuit state and the parallel circuit state, it is possible to manage the remaining electrical capacities of the respective electricity storage devices in a suitable manner.

[0010] It should be noted that a configuration in which the state of the plurality of electricity storage devices (for example, lithium-ion batteries) is switched between the series state and the parallel state need only be a configuration that has two or more electricity storage devices whose state can be switched between the series state and the parallel state, and includes, for example, a configuration in which, in a power supply system comprising three or more electricity storage devices, the state of at least two electricity storage devices among the electricity storage devices is switched between the series state and the parallel state.

[0011] The remaining electrical capacities of the electricity storage devices may be those that specify a quantity of electricity remaining from a full electrical capacity that can be stored in the electricity storage device, or those that specify a quantity of electricity remaining in an available region of the electricity storage device excluding a detection error, a redundantly used region, a margin for degradation, or the like. [Brief description of the drawings]

[0012] The aforementioned and further tasks, features and advantages of the present disclosure will become clearer from the detailed description below with reference to the accompanying drawing. It shows: Fig. 1 an electrical circuit diagram illustrating a power supply system according to a first embodiment; Fig. 2 a diagram illustrating a specific configuration of a switch; Fig. 3(a) a diagram illustrating a state in which the respective lithium-ion batteries are connected in parallel, and Fig. 3(b) a diagram illustrating a state in which the respective lithium-ion batteries are connected in series; Fig. 4(a) a diagram illustrating current flow during parallel charging, and Fig. 4(b) a diagram illustrating the current flow during a parallel circuit discharge; Fig. 5 a diagram illustrating current flow during series circuit discharge; Fig. 6 a time sequence diagram illustrating a transition of SOC1 and SOC2 of the respective lithium-ion batteries during a parallel discharge and a series discharge; Fig. 7 a diagram illustrating a relationship between a gate voltage and a drain-source resistance; Fig. 8 a flowchart illustrating a processing procedure for controlling a connection state and charging and discharging currents of the lithium-ion batteries; Fig. 9. A flowchart that shows a processing procedure following... Fig. 8 illustrates; Fig. 10 a diagram illustrating a relationship between a difference in SOCs and a switch resistance value; Fig. 11 an electrical circuit diagram illustrating a power supply system in a second embodiment; Fig. 12 a diagram illustrating a state in which the respective lithium-ion batteries are connected in series; Fig. 13 a flowchart illustrating a processing procedure for controlling a connection state and charging and discharging currents of the lithium-ion batteries according to the second embodiment; Fig. 14 a flowchart that shows a processing procedure following Fig. 13 illustrates; Fig. 15 a flowchart illustrating a processing procedure for controlling a connection state and charging and discharging currents of the lithium-ion batteries according to a third embodiment; Fig. 16 a flowchart that shows a processing procedure following Fig. 15 illustrated; Fig. 17 a diagram illustrating a relationship between a difference in connection voltages ΔV and a switch resistance value; and Fig. 18 a diagram illustrating a relationship between the difference in connection voltages ΔV, a battery temperature and a switch resistance value. [Description of the embodiment examples](First embodiment example)

[0013] Exemplary embodiments of the present disclosure are described below with reference to the drawing. In the present exemplary embodiment, a vehicle-internal power supply device is embodied, which supplies power to various equipment components of a vehicle that is powered by an internal combustion engine as a drive source. Furthermore, the present power supply system is a so-called dual power supply system, comprising a first electrical storage device, which includes a lead-acid battery, and a second electrical storage device, which includes a plurality of lithium-ion batteries, as electrical storage devices.

[0014] As it is in Fig. As illustrated in Figure 1, the present power supply system comprises a lead-acid battery 11 and two lithium-ion batteries 12 and 13, wherein power can be supplied from the respective batteries 11 to 13 to various types of electrical loads 14 and 15 and a rotating electric machine 16. Furthermore, the respective batteries 11 to 13 can be charged by the rotating electric machine 16.

[0015] The lead-acid battery 11 is a well-known multi-purpose battery. Meanwhile, the lithium-ion batteries 12 and 13 are high-density batteries that exhibit lower power loss during charging and discharging, and higher output density and energy density than the lead-acid battery 11. The lithium-ion batteries 12 and 13 are preferably batteries that have a higher energy efficiency during charging and discharging than the lead-acid battery 11. Furthermore, the lithium-ion batteries 12 and 13 are configured as composite batteries, each comprising a plurality of individual cells.

[0016] The nominal voltages of these batteries 11 to 13 are all the same and, for example, 12V.

[0017] While a detailed description using the drawing is omitted, the two lithium-ion batteries 12 and 13 are housed in a storage enclosure and configured as an integrated battery unit U. The battery unit U has two output terminals, P1 and P2. The lead-acid battery 11 and the electrical load 14 are connected to output terminal P1, and the electrical load 15 and the rotating electric machine 16 are connected to output terminal P2.

[0018] The electrical load 14, connected to output terminal P1, is a 12V system load powered by a 12V supply from the lead-acid battery 11 or the lithium-ion batteries 12 and 13. The electrical load 14 comprises a constant-voltage load, which requires that the voltage of the supplied power be constant or stable, i.e., fluctuate within at least a predetermined range, and a typical electrical load that differs from the constant-voltage load. The constant-voltage load is a protected load, meaning it does not tolerate a power supply failure. Specific examples of constant-voltage loads include a navigation device, an audio device, a measuring instrument, and various types of ECUs, such as a power machine ECU.In this case, by suppressing fluctuations in the voltage of the supplied power, the occurrence of unnecessary resets or similar issues in the aforementioned devices is prevented, thus enabling stable operation. Furthermore, specific examples of typical electrical loads include lamps, such as headlights, windshield wipers, and electric pumps.

[0019] Furthermore, the electrical load 15 is a high-voltage system load for which a large control force is required temporarily, for example, when driving a vehicle; that is, a high power requirement may be imposed. Specific examples of high-voltage system loads can include an electric power steering device. It should be noted that the electrical load 14 connected to output terminal P1 corresponds to a low-voltage electrical load, whereas the electrical load 15 and the rotating electric machine 16 connected to output terminal P2 correspond to high-voltage electrical loads.

[0020] A rotating shaft of the rotating electric machine 16 is driven by a power machine output shaft (not illustrated) coupled by a belt or the like, wherein, as the rotating shaft of the rotating electric machine 16 rotates due to a rotation of the power machine output shaft, the power machine output shaft rotates due to a rotation of the rotating shaft of the rotating electric machine 16. The rotating electric machine 16 is a motor-generator (MG), comprising a power generation function for generating power (regeneration) by rotating the power machine output shaft and an axle shaft, and a power drive function for providing rotational force to the power machine output shaft.The rotating electric machine 16 is configured such that a power generation current during power generation and a torque during power drive are adjusted by an inverter as a power conversion device, which is provided integrally or separately. A power machine start or torque assistance is performed by a drive of the rotating electric machine 16. The rotating electric machine 16 is an electrical load with respect to the power added to the power machine output shaft and is also a high-power / high-current load in comparison to the electrical load 14.

[0021] A switch 17 is provided between the electrical load 15 and the rotating electric machine 16, wherein the respective batteries 11 to 13 and the rotating electric machine 16 are electrically connected to or disconnected from the electrical load 15 by the switch 17, which is turned on or off.

[0022] An electrical configuration of the battery unit U is described next. In the present embodiment, the state of the two lithium-ion batteries 12 and 13 can be switched between a parallel connection state and a series connection state, and this point is described in detail.

[0023] In battery unit U, switches 21 and 22 are connected in series with an electrical path L1 between output terminals P1 and P2. It should be noted that electrical path L1 is also part of a power supply path that connects electrical loads 14 and 15 and the rotating electric machine to the lead-acid battery 11 in the present system. A positive terminal of lithium-ion battery 12 is connected to a first point N1 between switches 21 and 22, and a positive terminal of lithium-ion battery 13 is connected to a second point N2 between switch 22 and output terminal P2. Furthermore, switches 23 and 24 are each connected between the negative terminals of lithium-ion batteries 12 and 13, respectively, and ground or an earth connection.Furthermore, the first point N1 is connected to a third point N3 between the negative terminal of the lithium-ion batteries 13 and the switch 24, with a switch 25 being provided along this connection path. Switches 21 to 25 correspond to "switching units".

[0024] The switches 21 to 25 described above are configured with semiconductor switching elements, such as MOSFETs, IGBTs, and bipolar transistors. In the present embodiment, each of the switches 21 to 25 is configured with a MOSFET, and the states of the switches 21 to 25 are switched between ON and OFF according to the application of a predetermined gate voltage.

[0025] It should be noted that, as it says in Fig. As illustrated in Figure 2, each of the switches 21 to 25 preferably comprises a pair of MOSFETs, the MOSFETs preferably being connected in series such that the parasitic diodes of the MOSFETs in each pair face in opposite directions. Due to the parasitic diodes facing in opposite directions, when the respective switches 21 to 25 are off, any current flowing through a path where the switch is present is completely interrupted. However, the respective switches 21 to 25 can employ any configuration using the semiconductor switching elements, for example, a configuration in which the parasitic diodes of the MOSFETs are not arranged to face in opposite directions.

[0026] By switching the states of these respective switches 21 to 25 between ON and OFF as appropriate, the state can be changed between a state in which the respective lithium-ion batteries 12 and 13 are connected in parallel and a state in which the respective lithium-ion batteries 12 and 13 are connected in series.

[0027] Fig. Figure 3(a) illustrates the state in which the respective lithium-ion batteries 12 and 13 are connected in parallel, and Fig. Figure 3(b) illustrates the state in which the respective lithium-ion batteries 12 and 13 are connected in series. Fig. Figure 3 illustrates only switches in an ON state among switches 21 to 25, omitting an illustration of switches in an OFF state for the sake of clarity. The power supply path shown in Fig. 3(a) is illustrated as a “parallel power supply path”, where the power supply path shown in Fig. Figure 3(b) illustrates a “series power supply path”. It should be noted that switch 17 is off in a parallel state and is turned on in a series state as required.

[0028] In Fig. 3(a) Switches 21 to 24 are switched on under the respective switches 21 to 25, with switch 25 being switched off, in which state the lithium-ion batteries 12 and 13 are in parallel. In this case, the output voltages of the output terminals P1 and P2 are essentially 12V. In the parallel state, the lead-acid battery 11 and the lithium-ion batteries 12 and 13 are connected in parallel to the electrical load 14 on the P1 side, with the lead-acid battery 11 and the lithium-ion batteries 12 and 13 being connected in parallel to the rotating electric machine 16 on the P2 side. In the parallel state, at an intermediate position (the first point N1) on a path connecting the positive electrodes of the respective lithium-ion batteries 12 and 13, a connection is made.

[0029] Furthermore, in Fig. 3(b) Under the respective switches 21 to 25, switches 21, 23 and 25 are switched on, while switches 22 and 24 are switched off, wherein in this state the lithium-ion batteries 12 and 13 are connected in series. In this case, the output voltage of output terminal P1 is essentially 12V, and the output voltage of output terminal P2 is essentially 24V. In a series connection state, the lead-acid battery 11 and the lithium-ion battery 12 are connected in parallel with the electrical load 14 on the P1 side. Furthermore, the lithium-ion batteries 12 and 13 are connected in series with the rotating electric machine 16 on the P2 side. In the series connection state, the rotating electric machine 16 is connected at a position (the second point N2) on the positive side of the battery 13 on the side of the higher voltage under the respective lithium-ion batteries 12 and 13.

[0030] The rotating electric machine 16 can operate in 12 V power mode, with a power supply voltage of 12 V, and in 24 V power mode, with a power supply voltage of 24 V. The rotating electric machine 13 is driven at 12 V in a state where the lithium-ion batteries 12 and 13 are connected in parallel, and the rotating electric machine 16 is driven at 24 V in a state where the lithium-ion batteries 12 and 13 are connected in series. The electrical load 15, connected to output terminal P2, is driven at 24 V in a state where the lithium-ion batteries 12 and 13 are connected in series.

[0031] Furthermore, it includes Fig. 1. The battery unit U includes a control unit 30, which forms a battery control device. The control unit 30 switches the states of the respective switches 21 to 25 in the battery unit U between ON and OFF (open and closed). In this case, the control unit 30 controls the ON and OFF of the respective switches 21 to 25 based on the vehicle's driving state and the energy storage states of the respective batteries 11 to 13. This allows for selective charging and discharging using the lead-acid battery 11 and the lithium-ion batteries 12 and 13. A charging and discharging control system based on the energy storage states of the respective batteries 11 and 12 is briefly described.It should be noted that, while an illustration has been omitted, a voltage sensor, which detects a connection voltage for each battery, and a current sensor, which detects a power supply current for each battery, are provided for each of the lithium-ion batteries 12 and 13, with detection results from the respective sensors being output to the control unit 30.

[0032] The control unit 30 sequentially acquires values ​​for the connection voltages of the lead-acid battery 11 and the lithium-ion batteries 12 and 13, and it sequentially acquires power supply currents of the lead-acid battery 11 and the lithium-ion batteries 12 and 13. Then, based on these acquired values, the control unit 30 calculates OCVs (open circuit voltages) and SOCs (states of charge) of the lead-acid battery 11 and the lithium-ion batteries 12 and 13, controlling the charging and discharging amounts of the lithium-ion batteries 12 and 13 in such a way that the OCVs and the SOCs are maintained within a predetermined operating range.

[0033] Furthermore, after the main power supply of a vehicle is switched on, the state of the respective lithium-ion batteries 12 and 13 in the battery unit U is generally changed to a parallel connection state. However, in response to a load control request at output terminal P2 and a request for high-voltage power generation from the rotating electric machine 16, the state of the respective lithium-ion batteries 12 and 13 is switched to a series connection state. In this case, the control unit 30 performs a control operation to switch the state of the lithium-ion batteries 12 and 13 from the parallel connection state to the series connection state, based, for example, on a control request from the electric power steering device (the electric load 15) and a torque support request from the rotating electric machine 16.

[0034] The ECU 40 is connected to the control unit 30. The control unit 30 and the ECU 40 are connected via a communication network, such as a CAN bus, to enable communication and the sharing of various types of data stored in the control unit 30 and the ECU 40. The ECU 40 is an electronic control device that performs an idle stop control function for the vehicle. Idle stop control, as is commonly known, is a control system for automatically stopping a motor when predetermined automatic stop conditions are met and for restarting the motor when predetermined restart conditions are met in an automatically stopped state. In the vehicle, the motor is started by the rotating electric motor 16 during an automatic restart by the idle stop control.

[0035] A parallel charging process, in which charging is carried out by the rotating electric machine 16 in a state in which the lithium-ion batteries 12 and 13 are connected in parallel, and a parallel discharging process, in which discharging to the electrical load 14 is carried out in a state in which the lithium-ion batteries 12 and 13 are connected in parallel, are described next. Fig. 4(a) illustrates a current flow during parallel charging, wherein Fig. Figure 4(b) illustrates a current flow during a parallel circuit discharge.

[0036] During parallel charging in Fig. 4(a) A power generation current is output by the rotating electric machine 16, charging the lead-acid battery 11 and the respective lithium-ion batteries 12 and 13, and supplying power to the electrical load 14 with the power generation current. At this time, there are switches 22 and 23 in the battery unit U on a charging path of the lithium-ion battery 12, whereby a charging current Iin 1 flows corresponding to path resistances that include switches 22 and 23. Furthermore, there is a switch 24 on a charging path to the lithium-ion battery 13, whereby a charging current Iin 2 flows corresponding to path resistances that include switch 24. When the charging currents Iin 1 and Iin 2 are compared, Iin 1 ≠ Iin 2, whereby, in particular, it is assumed from a difference in the path resistances that “Iin 1 < Iin 2”.

[0037] Furthermore, during a parallel circuit discharge in Fig. 4(b) Power is supplied from the respective lithium-ion batteries 12 and 13 to the electrical load 14. At this time, there are switches 21 and 23 in the discharge path from the lithium-ion battery 12 to the electrical load 14, whereby a discharge current Iout 1 flows corresponding to path resistances that include switches 21 and 23. Furthermore, there are switches 21, 22, and 23 in a discharge path from the lithium-ion battery 13 to the electrical load 14, whereby a discharge current Iout 2 flows corresponding to path resistances that include switches 21, 22, and 24. When the discharge currents Iout 1 and Iout 2 are compared, Iout 1 ≠ Iout 2, whereby, in particular, it is assumed from a difference in the path resistances that “Iout 1 > Iout 2”.

[0038] As described above, in a state where the respective lithium-ion batteries 12 and 13 are connected in parallel, the magnitudes of the currents flowing through the respective batteries 12 and 13 are different. Consequently, it is feared that the states of charge (SOCs) of the respective lithium-ion batteries 12 and 13 will vary. This point is further described. Since in the parallel charging state described above, according to Fig. 4(a) “Iin 1 < Iin 2” from the difference in the path resistances applies and in the parallel discharge state described above according to Fig. 4(b) “Iout 1 > Iout 2” from the difference in the path resistances applies, while from a difference regarding currents it is assumed that the lithium-ion battery 13 has a higher SOC than the lithium-ion battery 12, when the state is the series connection state (see Fig. 3(b)) takes into account that the difference in the SOCs between the respective batteries 12 and 13 will increase.

[0039] That is, as it says in Fig. As illustrated in Figure 5, in a series discharge state, while lithium-ion battery 13 discharges to the electrical load 15 and the rotating electric machine 16 as one discharge destination, lithium-ion battery 12 also discharges to the electrical load 14 as an additional discharge destination, in addition to the electrical load 15 and the rotating electric machine 16. Consequently, the discharge current Iout 1 of lithium-ion battery 12 becomes greater than the discharge current Iout 2 of lithium-ion battery 13, further increasing the difference in the states of charge (SOC) between the respective batteries 12 and 13. When the SOCs vary between the respective lithium-ion batteries 12 and 13, the resulting inconvenience is that the operating ranges of the respective batteries 12 and 13 cannot be fully utilized.

[0040] It should be noted that in the present embodiment, the positive terminal of the lithium-ion battery 12 is connected in series with the electrical load 14, which is a low-voltage load, and the lithium-ion battery 12 corresponds to a "first electricity storage device". Furthermore, the positive terminal of the lithium-ion battery 13 is connected in series with the electrical load 15 and the rotating electric machine 16, which are high-voltage loads, and the lithium-ion battery 13 corresponds to a "second electricity storage device".

[0041] Consequently, in the present embodiment, the states of charge (SOCs) of the respective lithium-ion batteries 12 and 13 are each provided, wherein, in the case where the lithium-ion batteries 12 and 13 are in a parallel connection state, charging and discharging currents for each battery 12 and 13 are controlled by adjusting the resistance values ​​of the respective switches, such that a predetermined difference between the SOCs of the respective batteries 12 and 13 occurs. In this case, in a state where the respective lithium-ion batteries 12 and 13 are connected in parallel, a desired difference in the SOCs of the respective batteries 12 and 13 is intentionally provided in anticipation of the subsequent switch from the parallel connection state to the series connection state.This prevents the difference in the state of charge (SOC) between the respective lithium-ion batteries 12 and 13 from increasing excessively, even when power is supplied to both the low-voltage load (12V system load) and the high-voltage load (24V system load) in the series connection state. It should be noted that the control unit 30 corresponds to a "capacity procurement unit" and a "current control unit".

[0042] Current control of the respective batteries 12 and 13 during parallel discharge and series discharge of the lithium-ion batteries 12 and 13 is described below. This involves a change in the state of charge (SOC) of the respective lithium-ion batteries 12 and 13 in the case where the state changes from the parallel discharge state ( Fig. 4(b)) on the series discharge state ( Fig. 5) passes, specifically using Fig. 6 described. It should be noted that in Fig. 6. SOC 1 and SOC 2 respectively indicate the state of charge (SOC) of the lithium-ion batteries 12 and 13, where resistors R1 and R2 respectively indicate the resistance values ​​of switches 23 and 24. Furthermore, when SOC 1 and SOC 2 are transitioned, solid lines indicate a change in the SOCs when a desired difference is intentionally introduced between SOC 1 and SOC 2 in the present embodiment, while dashed lines indicate a change in the SOCs when SOC 1 and SOC 2 are made equal for comparison. SOC 1 and SOC 2 are each shown in an upper and a lower diagram.

[0043] In Fig. 6. A parallel discharge is performed for a period of time up to time t1, followed by a series discharge after time t1. In the case where the states of charge (SOCs) of the respective lithium-ion batteries 12 and 13 are equalized during a parallel discharge, as indicated by the dashed lines, both SOC 1 and SOC 2 are "A" at time t1. Then, after the state has switched from the parallel to the series state at time t1, as described above, "Iout 1 > Iout 2" by a difference in the discharge targets or setpoints of the respective batteries 12 and 13, resulting in a difference in the decrease rates of SOC 1 and SOC 2. Consequently, the SOC of lithium-ion battery 12 reaches a lower limit earlier than the SOC of lithium-ion battery 13 (t2 in the diagram).

[0044] Meanwhile, in the present embodiment, a difference in the state of charge (SOC) of the respective lithium-ion batteries 12 and 13 is provided during parallel discharge, such that "SOC 1 > SOC 2". Consequently, SOC 1 and SOC 2 transition as indicated by the solid lines, with SOC 1 and SOC 2 becoming B1 and B2 respectively at time t1 (B1 > B2). Then, after the state has switched from the parallel to the series state at time t1, even if "Iout 1 > Iout 2" is a difference in the discharge targets of the respective batteries 12 and 13, it is possible to prevent SOC 1 of lithium-ion battery 12 from reaching its lower limit earlier than SOC 2 of lithium-ion battery 13 (t3 in the drawing).

[0045] For comparison, while during a parallel circuit discharge in Fig. 4(b) a difference between discharge currents Iout 1 and Iout 2 of the respective lithium-ion batteries 12 and 13 is caused by a difference in switches in discharge paths, during series discharge in Fig. 5 a difference between the discharge currents Iout 1 and Iout 2 of the respective lithium-ion batteries 12 and 13 is caused by a difference in charge targets or charge setpoints of the respective batteries 12 and 13, taking into account that the difference between the discharge currents becomes larger in the latter case (during series discharge).

[0046] As a configuration to provide a difference in the state of charge (SOC) of the respective lithium-ion batteries 12 and 13 during parallel discharge, the discharge currents of the respective batteries 12 and 13 are controlled by making the resistance value of the energy supply path of the lithium-ion battery 12 relatively larger than the resistance value of the energy supply path of the lithium-ion battery 13. More precisely, in Fig. 4(b) The discharge current Iout 1 of the lithium-ion battery 12 is reduced by increasing the resistance value R1 of the switch 23, which is provided in the power supply path of the lithium-ion battery 12. In this case, the resistance value R1 of the switch 23, and thus the path resistance value on the side of the lithium-ion battery 12, is changed by adjusting a drain-source resistance by changing the gate voltage Vg using a relationship between the gate voltage Vg and the drain-source resistance, which is given in Fig. 7 illustrates how it is controlled. Fig. 7 defines the relationship in which the drain-source resistance increases by decreasing the gate voltage Vg, based on the resistance value Rmin in a normal ON state, where the switch resistance value (drain-source resistance) is variably adjusted to be greater than Rmin.

[0047] By increasing the resistance value R1 of switch 23, the discharge current Iout 1 flowing through the lithium-ion battery 12 is reduced, thus encouraging a state of charge (SOC) of 1 to be greater than SOC 2. This makes it possible to delay the point at which the SOC 1 of the lithium-ion battery 12 reaches its lower limit after the state has been switched from the parallel to the series connection state, thereby suppressing the discomfort of prematurely limiting the discharge of battery unit U.

[0048] In the present embodiment, a predetermined difference in the state of charge (SOC) of the respective lithium-ion batteries 12 and 13 is provided in the parallel-connected charging state, as described above. In this case, the charging currents of the respective batteries 12 and 13 are controlled by making the resistance value of the energy supply path of the lithium-ion battery 13 relatively larger than the resistance value of the energy supply path of the lithium-ion battery 12. More precisely, in Fig. 4(a) by increasing the resistance value R2 of switch 24, which is provided at the power supply path of the lithium-ion battery 13, the charging current Iin 2 of the lithium-ion battery 13 is decreased. In this case, the resistance value R2 of switch 24, and thus the path resistance value on the side of the lithium-ion battery 13, is changed by adjusting the drain-source resistance by adjusting the gate voltage Vg using the relationship in Fig. 7 is controlled.

[0049] By increasing the resistance value R2 of switch 24, the charging current Iin 2 flowing through the lithium-ion battery 13 is reduced, thus ensuring that "SOC 1 > SOC 2". This makes it possible, under the condition that power is supplied to the respective loads, to delay the point at which SOC 1 of the lithium-ion battery 12 reaches its lower limit after the state has switched from the charging to the discharging state, thereby also suppressing the discomfort of prematurely limiting the discharge of battery unit U.

[0050] Fig. 8 and Fig. Figure 9 shows flowcharts illustrating a processing procedure for controlling a circuit state and charging and discharging currents of the respective lithium-ion batteries 12 and 13, wherein the present processing is repeatedly performed by the control unit 30 at predetermined intervals.

[0051] In Fig. In step S11, the state of charge (SOC) of the respective lithium-ion batteries 12 and 13 is obtained. In the subsequent step S12, the difference in the SOCs between the respective lithium-ion batteries 12 and 13 is calculated. Then, in step S13, the power supply current values ​​of the respective lithium-ion batteries 12 and 13 are obtained. In step S14, it is determined whether the battery unit U is in a state of charge or not. If the battery unit U is in a state of charge, processing proceeds to step S15. If the battery unit U is not in a state of charge but in a state of discharge, processing proceeds to step S31. Fig. 9. It should be noted that in step S14, if the power output of the rotating electric machine 16 is greater than the power input from a load, the battery unit U is determined to be in the charging state, while if the power input from the load is greater than the power output of the rotating electric machine 16, the battery unit U is determined to be in the discharging state. However, whether the battery unit U is in the charging state is determined according to whether the rotating electric machine 16 is in a power output state or not.

[0052] In step S15, it is determined whether the state of the respective lithium-ion batteries 12 and 13 is a parallel state or not. If the state of the respective lithium-ion batteries 12 and 13 is a parallel state, processing proceeds to the subsequent step S16. In step S16, it is determined whether a request to switch the state of the lithium-ion batteries 12 and 13 from the parallel state to the series state occurs. If the switching request does not occur, processing proceeds to step S17, where processing to control the power supply currents for each of the lithium-ion batteries 12 and 13 is carried out by a separate processing step from S17 to S20.

[0053] For details, in step S17 the control states (power supply states) of the respective electrical loads 14 and 15 are recorded, whereby in the subsequent step S18 a setpoint for the difference in the state of charge (SOC) between the respective lithium-ion batteries 12 and 13 is set based on the load control states. Specifically, in step S17 it is recorded whether the respective electrical loads 14 and 15 are in a control-ON state or a control-OFF state. Then, when the electrical load 14 on the output terminal P1 side is in the control-ON state under the electrical loads 14 and 15, in step S18 the setpoint of the difference in the SOCs is set such that the SOCs of the respective lithium-ion batteries 12 and 13 become such that “SOC 1 > SOC 2” is expected to be “Iout 1 > Iout 2” in the parallel discharge state.At this time, the setpoint of the difference in the states of charge (SOCs) is preferably adjusted based on the required power of the electrical load 14. For example, if the required power of the electrical load 14 increases, the setpoint of the difference in the SOCs is increased. Furthermore, at this time, the setpoint SOCs of the respective lithium-ion batteries 12 and 13 are preferably adjusted based on the total required power of the respective electrical loads 14 and 15, with, for example, the setpoint SOCs being increased if the total required power is greater.

[0054] It should be noted that if each of the respective electrical loads 14 and 15 comprises a plurality of loads, the setpoint of the difference in the SOCs is preferably set based on which of the plurality of loads is in the control state. For example, assuming a case in which only one element consisting of a headlight and a windshield wiper is controlled as the electrical load 14, and a case in which both are controlled, the setpoint of the difference in the SOCs in the case in which both are controlled is preferably set higher than the setpoint of the difference in the SOCs in the case in which only one of them is controlled. However, in steps S17 and S18, it is also possible to set a predetermined value, defined in advance, as the setpoint of the difference in the SOCs, which realizes "SOC 1 > SOC 2".

[0055] In the subsequent step S19, when adjusting the path resistance value, it is determined whether the power supply current flowing through the target path, for which the resistance value is to be adjusted, is less than a predetermined value. Here, it is determined whether the power supply current (Iin 2 in) Fig. 4(a)), which flows through the energy supply path of battery 13 from the lithium-ion batteries 12 and 13, is less than the predetermined value or not. If the determination result in step S19 is YES, processing proceeds to the subsequent step S20, whereas if the determination result in step S19 is NO, the current processing is terminated without any processing being carried out.

[0056] In step S20, the resistance value of switch 24, which is to be adjusted, is adjusted. At this time, the gate voltage is controlled based on the setpoint of the difference in the SOCs, with the resistance value of switch 24 being changed towards the point where the resistance value is higher in an ON state. For example, the switch resistance value is adjusted according to the difference in the SOCs using a relationship in Fig. 10 set. Fig. Section 10 defines the relationship in which the switch resistance value increases as the difference in the SOCs increases. Furthermore, it is determined accordingly. Fig. 10 The switch resistance value is set according to the power supply current value of the lithium-ion battery 13. Specifically, the switch resistance value is set to a smaller value when the power supply current value is higher, taking into account that energy loss across a resistor increases with higher power supply current. This also corrects the resistance value to be correspondingly smaller if the switch resistance value is greater than Rmin, corresponding to the difference in the states of charge (SOCs) when the power supply current value increases. It should be noted that it is preferable to set an upper limit for the switch resistance value. The control unit 30 adjusts the switch resistance value by means of digital / analog control or PWM control (processing in step S36, described below, is performed in a similar manner).

[0057] By adjusting the resistance value of switch 24 in step S20, the path resistance value of lithium-ion battery 13 becomes greater than the path resistance value of lithium-ion battery 12, resulting in the charging currents of the respective lithium-ion batteries 12 and 13 being controlled individually.

[0058] Furthermore, if step S16 determines that a state change from parallel to series is required, processing proceeds to step S21, where it is determined whether the difference in the states of charge (SOCs) between the respective lithium-ion batteries 12 and 13 matches the target value. Specifically, it is determined whether the actual difference in the SOCs falls within a predetermined range defined based on the target value. The predetermined range is specified with an upper and a lower limit. Then, if the difference in the SOCs matches the target value, processing proceeds to step S22, where the state is changed from parallel to series.Furthermore, if the difference in the SOCs does not match the target value, processing proceeds to step S17, performing the resistance adjustment processing described above (steps S17 to S20).

[0059] Furthermore, if step S15 determines that the state is not the parallel state but the series state, processing proceeds to step S23, where it is determined whether a request to switch the state of lithium-ion batteries 12 and 13 from the series state to the parallel state occurs. If the switching request occurs, processing proceeds to step S24, where the state is switched from the series state to the parallel state. If the switching request does not occur, processing terminates without any further processing taking place.

[0060] Meanwhile, in the case where it is determined in step S14 that the state is not the charging state but the discharging state, in step S31 in Fig. Step 9 determines whether the state of the respective lithium-ion batteries 12 and 13 is the parallel state. If so, processing proceeds to the subsequent step S32. Step S32 determines whether a request to switch the state of the lithium-ion batteries 12 and 13 from the parallel to the series state occurs. If the switching request does not occur, processing proceeds to step S33, where processing to adjust the resistance values ​​in the power supply paths of the respective lithium-ion batteries 12 and 13 is performed by processing from step S33 to S36.

[0061] For details, in step S33, the control states (power supply states) of the respective electrical loads 14 and 15 are recorded. In the subsequent step S34, the setpoint for the difference in the states of charge (SOC) between the respective lithium-ion batteries 12 and 13 is set based on the control states of the loads. The processing in steps S33 and S34 is similar to the processing in steps S17 and S18 described above, except that if the electrical load 14 is in a control-ON state, the setpoint for the difference in the SOCs is set such that the SOCs of the respective lithium-ion batteries 12 and 13 become such that "SOC 1 > SOC 2". However, different values ​​can be set as the setpoint for the difference in the SOCs between a situation during parallel charging and a situation during parallel discharging.Furthermore, in steps S33 and S34 it is also possible to set a predetermined value, defined in advance, as the target value of the difference in the SOCs, which realizes “SOC 1 > SOC 2”.

[0062] In the subsequent step S35, when adjusting the path resistance value, it is determined whether the power supply current flowing through the target path, for which the resistance value is to be adjusted, is less than a predetermined value. This determines whether the power supply current (Iout 1 in Fig. 4(b)), which flows through the energy supply path of battery 12 from the lithium-ion batteries 12 and 13, is less than the predetermined value or not. If the determination result in step S35 is YES, processing proceeds to the subsequent step S36, whereas if the determination result in step S35 is NO, the present processing is terminated without any processing being carried out.

[0063] In step S36, the resistance value of switch 23, which is to be adjusted, is adjusted. At this time, the gate voltage is controlled based on the setpoint of the difference in the SOCs, whereby the resistance value of switch 23 is changed towards the point where the resistance value is higher in an ON state. The switch resistance value is preferably set in a manner similar to that described above in step S20, wherein the relationship in Fig. 10 is used.

[0064] By adjusting the resistance value of switch 23 in step S36, the path resistance value of lithium-ion battery 12 becomes greater than the path resistance value of lithium-ion battery 13, resulting in the discharge currents of the respective lithium-ion batteries 12 and 13 being individually controlled.

[0065] Furthermore, if step S32 determines that a state change from parallel to series is required, processing proceeds to step S37, where it is determined whether the difference in the states of charge (SOCs) between the respective lithium-ion batteries 12 and 13 matches the target value. Specifically, it is determined whether the actual difference in the SOCs falls within a predetermined range defined based on the target value. If the difference in the SOCs matches the target value, processing proceeds to step S38, where the state is changed from parallel to series.Furthermore, if the difference in the SOCs does not match the target value, processing proceeds to step S33, where the resistance adjustment processing described above is performed (steps S33 to S36).

[0066] Furthermore, if step S31 determines that the state is not the parallel state but the series state, processing proceeds to step S39, where it is determined whether a request to switch the state of lithium-ion batteries 12 and 13 from the series state to the parallel state occurs. If the switching request occurs, processing proceeds to step S39, where the state is switched from the series state to the parallel state. If the switching request does not occur, the current processing is terminated without any further processing taking place.

[0067] According to the present embodiment, which has been described in detail above, the excellent effects mentioned below can be obtained.

[0068] With the configuration described above, when the respective lithium-ion batteries 12 and 13 are in parallel, the charging and discharging currents are controlled by adjusting the switch resistance values ​​in the power supply paths of the respective batteries based on their states of charge (SOCs) such that a desired difference in the SOCs between the respective batteries 12 and 13 occurs. In this case, a desired difference in the SOCs is intentionally provided in the parallel state in anticipation that the state will subsequently switch to the series state.This makes it possible to prevent the difference in the state of charge (SOC) between the respective lithium-ion batteries 12 and 13 from increasing excessively, even when power is supplied to the respective electrical loads 14 to 16 in the low-voltage system and in the high-voltage system in the series connection state. As a result, it is also possible to manage the SOCs of the respective lithium-ion batteries 12 and 13 appropriately when the state of the respective lithium-ion batteries 12 and 13 is switched between the series and parallel connection states.

[0069] In the series connection state, it is taken into account that, because the discharge current of lithium-ion battery 12 (the energy storage device on the low-voltage load side) is greater than the discharge current of lithium-ion battery 13 (the energy storage device on the high-voltage load side), the state of charge (SOC) of lithium-ion battery 12 decreases earlier than the SOC of lithium-ion battery 13. Considering this, a configuration is used in which the switch resistance values ​​are adjusted such that SOC 1 of lithium-ion battery 12 is greater than SOC 2 of lithium-ion battery 13 when the system is in the parallel connection state, even when power is supplied to the respective electrical loads in the series connection state. This prevents the difference in the SOCs between the respective lithium-ion batteries 12 and 13 from increasing excessively.

[0070] Furthermore, because the state of charge (SOC) of the lithium-ion battery 12, which is likely to be over-discharged, is made relatively larger, the concern that the lithium-ion battery 12 will be over-discharged is suppressed. That is, the usable range of the SOC becomes a value close to a lower limit, thus limiting the discharge of the battery unit U. Consequently, it is possible to make most of the SOCs from the upper to the lower limit for the respective lithium-ion batteries 12 and 13, thereby increasing the range of actual SOC usage.

[0071] A configuration is used in which, when the system is in parallel and power is supplied to the low-voltage load, the discharge currents of the respective lithium-ion batteries 12 and 13 are controlled by making the resistance value of switch 23 on the power supply path of lithium-ion battery 12 relatively larger than the resistance value of switch 24 on the power supply path of lithium-ion battery 13. In this case, by causing battery 13 on the high-voltage load side to preferably discharge in the parallel state, it is possible to reduce the decrease in the state of charge (SOC) of battery 12 on the low-voltage load side. This makes it possible to provide a desired difference in the states of charge between the respective lithium-ion batteries 12 and 13.

[0072] A configuration is used in which, when the system is in parallel and the rotating electric machine 16 is generating power, the charging currents of the respective lithium-ion batteries 12 and 13 are controlled by making the resistance value of switch 24 on the power supply path of lithium-ion battery 13 relatively larger than the resistance value of switch 23 on the power supply path of lithium-ion battery 12. In this case, by causing battery 12 on the low-voltage load side to preferably undergo charging in the parallel state, it is possible to reduce the increase in the state of charge (SOC) of battery 13 on the high-voltage load side. This makes it possible to provide the desired difference in the states of charge between the lithium-ion batteries 12 and 13.

[0073] A configuration is used in which the setpoint for the difference in state of charge (SOC) between the respective lithium-ion batteries 12 and 13 is adjusted based on the control state of the electrical load 14, which is a low-voltage load. The switch resistance value is adjusted such that, in the case of a parallel connection, the difference in SOC between the respective lithium-ion batteries 12 and 13 becomes the setpoint. In this case, even if the required power of the electrical load 14 changes, it is possible to provide the desired difference in SOC between the respective lithium-ion batteries 12 and 13.

[0074] A configuration is used in which, if the path resistance values ​​of the power supply paths leading to the respective lithium-ion batteries 12 and 13 are changed, the resistance values ​​of switches 23 and 24, provided on the negative terminal sides of the respective batteries 12 and 13, are increased. That is, a configuration is used in which the resistance values ​​are higher than the resistance values ​​(minimum resistance values ​​Rmin) in a fully ON state of the respective switches 23 and 24. In this case, it is possible to prevent the charging and discharging currents from becoming excessively large, thus protecting the respective lithium-ion batteries 12 and 13.Furthermore, provided that switches 23 and 24 are configured with semiconductor switching elements, such as MOSFETs, it is possible to easily adjust resistances by controlling the gate voltages of the semiconductor switching elements.

[0075] Since a configuration is used in which the resistance value of the switch, for which the resistance value is to be changed, is set based on the charging and discharging currents of the respective lithium-ion batteries 12 and 13, it is possible to control the adjustment of the resistance values ​​while taking into account energy loss caused by increasing the resistance values. In this case, if the charging and discharging currents of the respective lithium-ion batteries 12 and 13 are relatively large, the resistance values ​​are made smaller, while the resistance values ​​are made larger corresponding to a decrease in the charging and discharging currents. This makes it possible to minimize energy loss through the switch resistances.

[0076] A configuration is used in which, when the respective lithium-ion batteries 12 and 13 are in parallel, the charging and discharging currents for each are controlled by adjusting the resistance values ​​of switches 21 to 25 to switch the respective batteries 12 and 13 between series and parallel operation. In this case, by controlling the charging and discharging currents for each battery 12 and 13 using the ON resistances at the respective switches 21 to 25, it is possible to manage the state of charge (SOC) of the respective lithium-ion batteries 12 and 13 as desired without complicating the configuration.

[0077] Since switches 21 to 25 are configured with semiconductor switching elements, it is possible to easily adjust the charging and discharging currents for each of the lithium-ion batteries 12 and 13 by controlling the gate voltages or the like of the MOSFETs.

[0078] By using semiconductor switching elements as switches 21 to 25, it is possible to construct a system with higher operational reliability than in the case where a contact-point switching scheme switch (a so-called mechanical switch) is used. Furthermore, since the resistance value of the semiconductor switching element can be made lower than that of the mechanical switch, it is possible to reduce losses in the power supply path.

[0079] A configuration is used in which a pair of MOSFETs is used as each of the switches 21 to 25, with the switches 21 to 25 connected in series so that the parasitic diodes of the respective MOSFETs face in opposite directions. This makes it possible to preferentially suppress currents flowing through the power supply paths when the respective switches 21 to 25 are turned off.

[0080] A configuration is used in which gate voltages for switches 21 to 25 are controlled by a digital / analog controller or a PWM controller, and the resistance values ​​for these switches need to be adjusted. This allows for easy adjustment of the resistance values ​​as desired. Since current loss is theoretically zero in the PWM controller when the duty cycle is OFF, a highly efficient system can be implemented.

[0081] Furthermore, by controlling the path resistance values ​​using the switch for switching the state between the series and parallel states, which is provided as a basic function of the battery unit U, and the control unit 30, which performs a switching control, it is possible to implement processing to adjust the resistance values ​​as desired without adding any elements or the like to the basic configuration of the unit.

[0082] A configuration is used in which, if the difference in the state of charge (SOC) between the respective lithium-ion batteries 12 and 13 is determined to be less than a predetermined value, the state of the respective lithium-ion batteries 12 and 13 is allowed to transition from the parallel to the series connection state. In this case, if the difference in the SOC between the respective lithium-ion batteries 12 and 13 does not fall within a predetermined range, the resistance values ​​in the parallel connection state are continuously adjusted, and if the difference in the SOC falls within the predetermined range, the state is caused to transition from the parallel to the series connection state.Consequently, it is prevented that the difference in the SOCs becomes too small or too large, making it possible to suppress the occurrence of discomfort due to the difference in the SOCs after the state has transitioned to the series connection state. (Second example)

[0083] A second embodiment is described below, primarily with regard to a difference from the first embodiment described above. In this embodiment, a configuration comprising three lithium-ion batteries is used, and it is possible to switch the state of the three lithium-ion batteries between a parallel connection and a series connection. It should be noted that it is equally possible to use a configuration comprising four or more lithium-ion batteries.

[0084] In Fig. 11 includes the battery unit U as a difference to Fig. 1 Three lithium-ion batteries B1, B2, and B3, wherein a circuit for switching a connection is added with the addition of the lithium-ion battery. The battery unit U comprises switches 51 to 56, which are configured with semiconductor switching elements. The state of the respective lithium-ion batteries B1 to B3 can be switched between a parallel connection state and a series connection state by the respective switches 51 to 56, which are turned on and off.

[0085] Fig. Figure 12 illustrates a state in which the respective lithium-ion batteries B1 to B3 are in the power supply system in Fig. 11 are connected in series. It should be noted that in Fig. Figure 12 shows an illustration of switches 52 and 55 in an OFF state. In the series circuit state, the output voltage of output terminal P1 is approximately 12 V, and the output voltage of output terminal P2 is approximately 24 V.

[0086] In the battery unit U of the present embodiment, the positive terminals of the lithium-ion batteries B1 and B2 are connected in series to the electrical load 14, which is a low-voltage load, wherein the lithium-ion batteries B1 and B2 correspond to a "first electricity storage device". Furthermore, a positive terminal of the lithium-ion battery B3 is connected in series to the electrical load 15 and the rotating electric machine 16, which are high-voltage loads, wherein the lithium-ion battery B3 corresponds to a "second electricity storage device".

[0087] In the present embodiment, the control unit 30 then procures the respective states of charge (SOCs) of the respective lithium-ion batteries B1 to B3. When the respective batteries B1 to B3 are in parallel, the control unit regulates the charging and discharging currents for each battery by adjusting the resistance values ​​of the respective switches such that a predetermined difference in the SOCs occurs between the side of batteries B1 and B2 and the side of battery B3. In this case, when the respective lithium-ion batteries B1 to B3 are connected in parallel, a difference in the SOCs of the respective batteries B1 to B3 is intentionally provided in anticipation of a subsequent switch from the parallel to the series connection state.This prevents the difference in the SOCs of the respective lithium-ion batteries B1 to B3 from increasing excessively, even when power is supplied to the low-voltage load (12V system load) and the high-voltage load (24V system load) in the series connection state.

[0088] For comparison purposes, it is also possible to perform a processing operation on the lithium-ion batteries B1 and B2, which are always in parallel, to equalize their states of charge (SOC). In this case, when discharging the respective lithium-ion batteries B1 and B2, the discharge current is preferably limited by increasing the resistance value of the switch on the battery with the lower SOC, specifically switches 53 and 54.

[0089] Fig. 13 and Fig. Figure 14 shows flowcharts illustrating a processing procedure for controlling the connection state and the charging and discharging currents of the respective lithium-ion batteries 12 and 13, wherein the present processing is repeatedly executed by the control unit 30 at predetermined intervals. The present processing is performed instead of the processing described above in Fig. 8 and Fig. 9 executed, whereby a description is simplified in a suitable manner, while the same number of steps are assigned to a common processing operation.

[0090] In Fig. 13 is considered a difference to the processing in Fig. 8 and Fig. 9. Step S51 is executed in the case where the batteries are being charged, the state is in parallel, and there is no request to switch to series (steps S14, S15: YES and S16: NO), whereby processing is performed in step S51. In step S51, it is determined whether all lithium-ion batteries B1 to B3 have been placed in a charging state or not. That is, it is determined by mutual self-balancing between the respective lithium-ion batteries B1 to B3 whether batteries in a charging state and batteries in a discharging state are mixed or not. At this time, it would be better to determine whether the respective lithium-ion batteries B1 to B3 are in a charging state or not based on the directions of the power supply currents.If the determination result in step S51 is YES, the processing proceeds to the subsequent step S20, whereas if the determination result in step S51 is NO, the current processing is terminated without any processing being carried out.

[0091] It should be noted that the processing in step S51 is to determine whether a discharge current flows through one of the lithium-ion batteries B1 to B3 from another battery in a state where the rotating electric machine 16 is generating power. If the result of the determination in step S51 is NO, that is, if it is determined that a discharge current flows through one of the batteries even though it is in a power-generating state (a state where the battery unit U is being charged), the state is determined to be self-balancing, and the present processing is terminated without any further processing. This eliminates the need for an adjustment of the switch resistance values ​​(step S20).

[0092] Meanwhile, in Fig. 14 as a difference to the processing in Fig. 8 and Fig. 9. In the case where the batteries are discharged, the state is in parallel, and there is no requirement to switch to series (step S14: NO, S31: YES, and S32: NO), processing is performed in step S52. Step S52 determines whether all lithium-ion batteries B1 to B3 are in a discharge state. That is, it determines whether batteries in a charge state and batteries in a discharge state are mixed by mutual self-balancing among the respective lithium-ion batteries B1 to B3. At this time, it would be better to determine whether the respective lithium-ion batteries B1 to B3 are in a charge state based on the directions of their energy supply paths.If the determination result in step S52 is YES, the processing proceeds to the subsequent step S36, whereas if the determination result in step S52 is NO, the current processing is terminated without any processing being carried out.

[0093] It should be noted that the processing in step S52 is to determine whether a charging current flows through one of the lithium-ion batteries B1 to B3 from another battery in a state where the rotating electric machine 16 is not generating power. If the result of the determination in step S52 is NO, that is, if it is determined that a charging current is flowing through one of the batteries even though it is in a non-power-generating state (a state where the battery unit U is discharging), the state is determined to be self-balancing, and the current processing is terminated without any further processing. This eliminates the need for an adjustment of the switch resistance values ​​(step S36).

[0094] In the event that a discharge current flows through one of the respective lithium-ion batteries B1 to B3, even though the system is in a power generation state (i.e., in the event that a discharge current flows due to self-balancing between the batteries), it is preferable to prioritize discharging. Furthermore, in the event that a charging current flows through one of the respective lithium-ion batteries B1 to B3, even though the system is in a non-power generation state (i.e., in the event that a charging current flows due to self-balancing between the batteries), it is preferable to prioritize charging.Regarding this point, a configuration is used in which the switch resistance values ​​are adjusted under the condition that all of the respective lithium-ion batteries B1 to B3 are in a state consisting of a charge and a discharge state. This makes it possible to suppress a blocking of current flow through self-balancing.

[0095] In the case where a discharge current flows through a self-balancing system in the power-generating state, it is possible to induce self-discharging by preventing the path resistance value for the discharging lithium-ion battery from increasing (i.e., by keeping the path resistance value low), which is suitable for resolving variations in the state of charge (SOC). Furthermore, in the case where a charging current flows through a self-balancing system in the non-power-generating state, it is possible to induce self-balancing by preventing the path resistance value for the charging lithium-ion battery from increasing (i.e., by keeping the path resistance value low), which is suitable for resolving variations in the SOC. (Third embodiment)

[0096] A third embodiment will be described next, primarily with regard to a difference from the first embodiment described above. In the present embodiment, a case is described in which the system is Fig. 1. While in the embodiments described above a difference in the SOCs is provided positively to the respective energy storage devices of the battery unit U, if the difference in the SOCs is too large, there is a concern that an overcurrent will occur due to self-adjustment of capacities between the energy storage devices. A current for self-adjustment of capacities, which is a current flowing according to the difference in the SOCs between the lithium-ion batteries 12 and 13 and the path resistance value, is defined, for example, as "I = difference in output voltages between batteries x path resistance value". In this case, there is a concern that a large current will flow between the batteries, which would negatively affect the switches and the batteries in the power supply paths.

[0097] Consequently, in the present embodiment, a parameter is obtained that interacts with the magnitude of a current flowing between the respective lithium-ion batteries 12 and 13, and current suppression is appropriately controlled based on this parameter. Here, electricity storage state parameters, which specify the states of the respective lithium-ion batteries 12 and 13, are obtained as the parameter that interacts with the current between the respective lithium-ion batteries 12 and 13, and the switch resistance value of the switch 22, which is present between the batteries 12 and 13 in the parallel connection state, or of the switch 25, which is present between the batteries 12 and 13 in the series connection state, is adjusted based on the electricity storage state parameters.

[0098] The state-of-charge parameters for the electricity storage system include, for example, at least one of the connection voltages, the state-of-charge (SOC) values, and the charging and discharging currents of the respective lithium-ion batteries 12 and 13. Furthermore, the temperatures of the respective lithium-ion batteries 12 and 13 are preferably also obtained.

[0099] A resistance value control in the parallel circuit state and a resistance value control in the series circuit state, which are carried out by the control unit 30, are described.

[0100] In the parallel circuit state, in a situation where the energy supply paths that are in Fig. As illustrated in Figure 3(a), where battery unit U is formed and a difference in the state of charge (SOC) occurs between the respective lithium-ion batteries 12 and 13, the control unit 30 anticipates an overcurrent flow between them. Consequently, the control unit 30 adjusts the resistance value of switch 22, which is present in an intermediate position between the respective batteries 12 and 13 in the parallel-connected state of the power supply path, to a higher value based on the state of charge parameters of the respective lithium-ion batteries 12 and 13 in order to suppress an overcurrent. At this time, the control unit 30 adjusts the resistance value of switch 22 to a desired value by obtaining a difference ΔV in the terminal voltages between the respective lithium-ion batteries 12 and 13 and performing regulation based on ΔV.More precisely, the control unit 30 controls the resistance value of switch 22 by controlling the gate voltage of switch 22. This increases the resistance value of switch 22 in an ON state, thereby reducing the current between the batteries. This control system feeds the current between the batteries back and regulates it to a desired value.

[0101] It should be noted that it is also possible to determine whether a situation exists in which an overcurrent flows, using the SOCs and the charging and discharging currents of the respective lithium-ion batteries 12 and 13 as the electricity storage state parameters, and in a situation in which an overcurrent flows, to control the resistance value of the switch 22 on the basis of the SOCs and the charging and discharging currents of the respective lithium-ion batteries 12 and 13.

[0102] Furthermore, in the series circuit state, when the energy supply paths that are in Fig. As illustrated in Figure 3(b), where battery unit U is formed and a high power supply voltage is generated by both lithium-ion batteries 12 and 13, there is a concern that an overcurrent will flow on the power supply path between these batteries 12 and 13 and the electrical load 15 or the rotating electrical machine 16. In fact, there is a concern that an overcurrent will flow through smoothing capacitors provided at the electrical load 15 and the rotating electrical machine 16. Consequently, the control unit 30 adjusts the resistance value of the switch 25, which is present in an intermediate position between the respective batteries 12 and 13 in the power supply path in the series-connected state, based on the electricity storage state parameters of the respective lithium-ion batteries 12 and 13, in order to suppress an overcurrent.At this time, the control unit 30 adjusts the resistance of switch 25 to a desired value by obtaining a series-connected power supply voltage (composite voltage Vhi) from the sum of the terminal voltages of the respective lithium-ion batteries 12 and 13 and performing a regulation based on Vhi. More precisely, the resistance of switch 25 is controlled by adjusting the gate voltage of switch 25. This increases the resistance of switch 25 in an ON state, thereby reducing the current between the batteries. This control mechanism feeds the current between the batteries back in and regulates it to a desired value.

[0103] Fig. 15 and Fig. Figure 16 shows flowcharts illustrating a processing procedure for controlling the connection state and the charging and discharging currents of the respective lithium-ion batteries 12 and 13, wherein the present processing is repeatedly executed by the control unit 30 at predetermined intervals. The present processing is performed instead of the processing described above in Fig. 8 and Fig. 9 executed, whereby a description is simplified in a suitable manner, while the same number of steps are assigned to a common processing operation.

[0104] In Fig. In step S61, after the state-of-charge (SOC) values ​​of the respective lithium-ion batteries 12 and 13 have been obtained and a difference in the SOC values ​​has been calculated (steps S11 and S12), the electricity storage state parameters are obtained. In the present embodiment, at least one parameter from the charging and discharging currents, the connection voltage, and the SOC, which are recorded for each of the lithium-ion batteries 12 and 13, is obtained as the electricity storage state parameters.

[0105] Then, if the batteries are being charged and the state is in parallel, and there is no request to switch to series (steps S14, S15: YES, S16: NO), in step S17 the control states (power supply states) of the respective electrical loads 14 and 15 are recorded. In the subsequent step S18, a setpoint for the difference in the state of charge (SOC) between the respective lithium-ion batteries 12 and 13 is set based on the control states of the loads. At this time, if the electrical load 14 is in a control-ON state on the output terminal P1 side, the setpoint for the difference in the SOCs is adjusted so that the SOCs of the respective lithium-ion batteries 12 and 13 become such that "SOC 1 > SOC 2".

[0106] Then, in step S20, the resistance value of switch 24, for which the resistance value is to be adjusted, i.e., switch 24, which is provided on the side of the lithium-ion battery in the power supply path, is adjusted on the basis of the target value of the difference in the SOCs.

[0107] In the subsequent step S62, the current flowing between the lithium-ion batteries 12 and 13 is fed back and controlled to a desired value based on the electricity storage state parameters of the respective lithium-ion batteries 12 and 13. Specifically, the control unit 30 calculates a difference ΔV of the terminal voltages using the terminal voltages of the respective lithium-ion batteries 12 and 13 as the electricity storage state parameters. Then, the control unit 30 determines an adjustment resistance value of the switch 22 based on the difference ΔV of the terminal voltages using a relationship in Fig. 17. Fig. Section 17 defines the relationship in which the adjustment resistance value of switch 22 increases as the difference ΔV of the terminal voltages increases. A larger adjustment resistance value is set for the resistance value (minimum value Rmin) of switch 22 in a fully ON state.

[0108] The adjustment resistance value of switch 22 can be determined using a relationship in Fig. 18 will be determined. Fig. Section 18 defines a relationship between the ΔV of the terminal voltages of the respective lithium-ion batteries 12 and 13, a battery temperature, and the adjustment resistance value of switch 22. In this case, the adjustment resistance value of switch 22 is set based on the respective parameters described above. It should be noted that the battery temperature can be the temperature of at least one of the lithium-ion batteries 12 and 13. If the temperatures of both batteries 12 and 13 are obtained, an average value of these temperatures can be used as the battery temperature.

[0109] Furthermore, if the batteries are set to a series charging state and no request to switch to a parallel state occurs (step S14: YES, S15 and S23: NO), in step S63 the current flowing between the lithium-ion batteries 12 and 13 is fed back and controlled to a desired value based on the electricity storage state parameters of the respective lithium-ion batteries 12 and 13. Specifically, the control unit 30 calculates a composite voltage Vhi of the lithium-ion batteries 12 and 13 in the series state (i.e., a voltage value of the output terminal P2), using the terminal voltages of the respective lithium-ion batteries 12 and 13 as the electricity storage state parameters.Then the control unit 30 determines an adjustment resistance value of the switch 25 based on the voltage Vhi using the relationship in . Fig. 17 (which indicates Vhi on a horizontal axis). Fig. 17 defines the relationship in which the adjustment resistance value of switch 25 increases when the voltage Vhi increases.

[0110] The adjustment resistance value of switch 25 can be determined using the relationship in Fig. 18 (which specifies Vhi on a horizontal axis) can be determined. Fig. Section 18 defines the relationship between the voltage Vhi, the battery temperature, and the adjustment resistance value of switch 25. In this case, the adjustment resistance value of switch 25 is set based on the respective parameters described above.

[0111] Meanwhile, in the case where the batteries are discharged and in the parallel circuit state, and no request occurs to switch the state to the series circuit state (step S14: NO, S31: YES, S32: NO), in step S33 in Fig. Sixteen control states (power supply states) of the respective electrical loads 14 and 15 are recorded, whereby in the subsequent step S34 a setpoint for the difference in the states of charge (SOCs) between the respective lithium-ion batteries 12 and 13 is set based on the control states of the loads. At this time, when the electrical load 14 is in a control-ON state on the output terminal P1 side, the setpoint for the difference in the SOCs is adjusted such that the SOCs of the respective lithium-ion batteries 12 and 13 become such that "SOC 1 > SOC 2".

[0112] Then, in step S36, the resistance value of switch 23, for which the resistance value is to be adjusted, i.e., switch 23, which is provided on the side of the lithium-ion battery 12 in the power supply path, is adjusted on the basis of the target value of the difference in the SOCs.

[0113] In the subsequent step S64, the current flowing between the lithium-ion batteries 12 and 13 is fed back and controlled to a desired value based on the electricity storage state parameters of the respective lithium-ion batteries 12 and 13. Specifically, the control unit 30 determines an adjustment resistance value of the switch 22 based on a difference ΔV between the terminal voltages of the respective lithium-ion batteries 12 and 13 and the battery temperature, using the relationship in Fig. 17 or Fig. 18.

[0114] Furthermore, if the batteries are in a series discharge state and there is no requirement to switch to a parallel state (steps S14, S31, and S39: NO), in step S65 the current flowing between lithium-ion batteries 12 and 13 is fed back and controlled to a desired value based on the electricity storage state parameters of the respective lithium-ion batteries 12 and 13. Specifically, the control unit 30 determines an adjustment resistance value of the switch 25 based on a composite voltage Vhi of the respective lithium-ion batteries 12 and 13 and the battery temperature using the relationship in Fig. 17 or Fig. 18.

[0115] According to the present embodiment, as described in detail above, the following excellent effects can be obtained in addition to the effects mentioned above.

[0116] In the case where the difference in the states of charge (SOCs) of the respective electricity storage devices is positively supplied, if the difference in the SOCs is too large, an overcurrent is feared to occur due to self-adjustment of capacitances between the electricity storage devices. With regard to this point, in the configuration described above, the electricity storage state parameters, which specify the states of the plurality of lithium-ion batteries 12 and 13, are obtained, whereby the resistance values ​​of the switches 22 and 25, which are present between the batteries 12 and 13 in the parallel or series connection state, are adjusted based on the electricity storage state parameters.In such a case, it is possible to control the current flowing on the power supply path in the parallel or series connection state—that is, the current or similar flowing between the lithium-ion batteries 12 and 13—in such a way as to prevent an overcurrent between the batteries, even if a difference in state of charge (SOC) occurs between the respective batteries. As a result, it is possible to achieve suitable use of the respective lithium-ion batteries 12 and 13. Since it is possible to achieve suitable use of the respective lithium-ion batteries 12 and 13, it is also possible to suppress deterioration and damage to the respective batteries 12 and 13, the semiconductor switching elements forming the switches 21 to 25, cable strands, or the like.

[0117] When the state of the lithium-ion batteries 12 and 13 is switched from the series connection state to the parallel connection state, it is taken into account that an overcurrent will occur in connection with the switchover. With regard to this point, since the resistance value of switch 22 in the parallel power supply path is adjusted based on the electricity storage state parameters in the parallel connection state, it is possible to suppress the occurrence of an overcurrent appropriately.

[0118] When the state of the lithium-ion batteries 12 and 13 is switched from the parallel to the series connection state, it is feared that an instantaneous current (load surge current) will occur once the switch to the series connection state is complete. However, since the resistance value of switch 25 in the series power supply path is adjusted based on the electricity storage state parameters in the series connection state, it is possible to appropriately suppress any overcurrent.

[0119] A configuration is used in which at least one of the charging and discharging currents, the connection voltages, and the state of charge (SOC) of the respective lithium-ion batteries 12 and 13 is obtained as the electricity storage state parameter, with the switch resistance value being adjusted based on the obtained data. In this case, it is possible to implement suitable control according to the actual electricity storage states of the respective lithium-ion batteries 12 and 13.

[0120] A configuration is used in which the temperatures of the respective lithium-ion batteries 12 and 13 are obtained, with the switch resistance value being adjusted based on the obtained data. In this case, by implementing control while taking the battery temperatures into account, it is possible to implement a configuration that is more suitable for protecting the respective batteries 12 and 13. The battery temperatures are parameters that differ from electrical parameters, such as the charging and discharging currents, the terminal voltages, and the state of charge (SOC), and can be obtained at any given time, regardless of whether the batteries are connected in series or parallel. The states of the respective lithium-ion batteries 12 and 13 can then be appropriately monitored using these battery temperatures. (Other examples)

[0121] The embodiments described above can be modified, for example, as described below.

[0122] While the embodiments described above employ a configuration in which, when the multiple lithium-ion batteries are connected in parallel, the charging and discharging currents of each individual lithium-ion battery are controlled by increasing the switch resistance values, it is equally possible to modify this configuration and employ one in which the charging and discharging currents of each lithium-ion battery are controlled individually by decreasing the switch resistance values. For example, if the switch resistance value (initial resistance value) is not a minimum value when the switch is normally ON, the switch resistance value is decreased.

[0123] It is also possible to use a configuration in which devices other than lithium-ion batteries can be used as a variety of electricity storage devices. For example, it is also possible to use a configuration consisting of a configuration in which batteries other than lithium-ion batteries are used as the variety of electricity storage devices, a configuration in which batteries and capacitors are used, and a configuration in which a variety of capacitors are used.

[0124] While the embodiments described above employ a configuration in which charging and discharging currents for each of the lithium-ion batteries are individually controlled by adjusting a resistance value when switching on a switch to change the state of the multitude of lithium-ion batteries between a series connection state and a parallel connection state, it is equally possible to change this configuration.For example, it is also possible to use a configuration in which another switch, formed with a semiconductor switching element that is different from the switch for switching a state between a series circuit state and a parallel circuit state, is provided in the power supply path of the battery unit U, whereby the charging and discharging currents for each of the lithium-ion batteries are individually controlled by adjusting an ON resistance value of the other switch.

[0125] It is also possible to use a variable resistor, which is different from the semiconductor switching element, as a variable resistor unit.

[0126] It is also possible to use a configuration in which the maximum energy storage capacities of the respective lithium-ion batteries 12 and 13 in battery unit U are differentiated. For example, the nominal voltage of lithium-ion battery 12 (the first energy storage device) and the nominal voltage of lithium-ion battery 13 (the second energy storage device) are set to different levels. This makes it possible to essentially equalize the available energy storage capacities even if a difference in the state of charge (SOC) of the respective lithium-ion batteries 12 and 13 is intentionally provided. Consequently, it is possible to implement a power supply system that is easy to use while maintaining a difference in the SOCs between the respective lithium-ion batteries 12 and 13.

[0127] In a configuration where the SOC1 of lithium-ion battery 12 is made larger than the SOC2 of lithium-ion battery 13 in the parallel connection state of lithium-ion batteries 12 and 13, it is also possible to make a maximum amount of electricity that can be stored in lithium-ion battery 12 greater than a maximum amount of electricity that can be stored in lithium-ion battery 13.

[0128] Since a configuration is used in which the maximum energy storage capacity of lithium-ion battery 12 is greater than the maximum energy storage capacity of lithium-ion battery 13, it is possible, even if the state of charge (SOC1) of lithium-ion battery 12 becomes greater than the state of charge (SOC2) of lithium-ion battery 13, to make the available energy storage capacities essentially equal. Consequently, it is possible to implement a power supply system that is easy to use while providing a difference in the states of charge (SOC) between the respective lithium-ion batteries 12 and 13.

[0129] While the present revelation has been described with reference to the examples, it is not limited to the examples and structures. The present revelation includes various modified examples and modifications within a range of equivalence. Additionally, various combinations, forms, and other combinations and forms comprising only one element, or more or fewer elements, fall within the scope of the present revelation.

Claims

[1] Power supply control device (30) to be used in a power supply system comprising: a variety of electricity storage devices (12, 13); and a switching unit comprising a plurality of switching devices (21 to 25) provided at electrical paths leading to the electricity storage devices, and configured to switch a state of the plurality of electricity storage devices between a parallel state in which the plurality of electricity storage devices are connected in parallel to each other and a series state in which the plurality of electricity storage devices are connected in series to each other, wherein the plurality of electricity storage devices comprises a first electricity storage device (12) whose positive side is connected to a low-voltage load (14) in a low-voltage system in the series connection state, and a second electricity storage device (13) whose positive side is connected to a high-voltage load (15, 16) in a high-voltage system in the series connection state, and the power supply control device comprises: a capacity procurement unit configured to procure the respective remaining electrical capacities of the multitude of electricity storage facilities; and a current control unit configured, in a case where the state of the plurality of electricity storage devices is the parallel-connected state, to i) control charging and discharging currents for each of the electricity storage devices by adjusting resistance values ​​of variable resistance units present in the electrical paths leading to the electricity storage devices, based on the remaining electrical capacities of the electricity storage devices procured by the capacity procurement unit, such that a difference between the remaining electrical capacity of the first electricity storage device and a remaining electrical capacity of the second electricity storage device becomes a desired amount, and ii) adjust the resistance values ​​of the variable resistance units such thatthat the remaining electrical capacity of the first electricity storage device is greater than the remaining electrical capacity of the second electricity storage device. [2] Power supply control device according to claim 1, wherein in the case where the state of the plurality of electricity storage devices is the parallel connection state and power is supplied to the low-voltage load, the current control unit controls discharge currents of the electricity storage devices by making a resistance value at an energy supply path of the first electricity storage device relatively greater than a resistance value at the energy supply path of the second electricity storage device. [3] Power supply control device according to claim 1 or 2, which is to be used in a power supply system comprising a power generating device (16) configured to supply generated power to the plurality of electricity storage devices, wherein, in the case where the state of the plurality of electricity storage devices is the parallel circuit state and the power generating device is generating power, the current control unit controls charging currents of the electricity storage devices by making the resistance value in the power supply path of the second electricity storage device relatively larger than the resistance value in the power supply path of the first electricity storage device. [4] Power supply control device according to one of claims 1 to 3, comprising: a state determination unit configured to determine that all of the multitude of electricity storage devices are in the same state, consisting of a charging state and a discharging state, wherein the current control unit adjusts the resistance values ​​of the variable resistance units under the condition that it is determined that all of the multitude of electricity storage devices are in a state of charge and discharge. [5] Power supply control device (30) to be used in a power supply system comprising: a variety of electricity storage devices (12, 13); and a switching unit comprising a plurality of switching devices (21 to 25) provided at electrical paths leading to the electricity storage devices, and configured to switch a state of the plurality of electricity storage devices between a parallel state in which the plurality of electricity storage devices are connected in parallel to each other and a series state in which the plurality of electricity storage devices are connected in series to each other, wherein the plurality of electricity storage devices comprises a first electricity storage device (12) whose positive side is connected to a low-voltage load (14) in a low-voltage system in the series connection state, and a second electricity storage device (13) whose positive side is connected to a high-voltage load (15, 16) in a high-voltage system in the series connection state, and the power supply control device comprises: a capacity procurement unit configured to procure the respective remaining electrical capacities of the multitude of electricity storage facilities; and A current control unit configured to control charging and discharging currents for each of the electricity storage devices in a case where the state of the plurality of electricity storage devices is the parallel-connected state, by adjusting resistance values ​​of variable resistor units present in the electrical paths leading to the electricity storage devices, based on the remaining electrical capacities of the electricity storage devices procured by the capacity procurement unit, such that a difference between the remaining electrical capacity of the first electricity storage device and a remaining electrical capacity of the second electricity storage device becomes a desired amount, and a state determination unit configured to determine that all of the multitude of electricity storage devices are in the same state, consisting of a charging state and a discharging state, wherein the current control unit adjusts the resistance values ​​of the variable resistance units under the condition that it is determined that all of the multitude of electricity storage devices are in a state of charge and discharge. [6] Power supply control device according to any one of claims 1 to 5, comprising: a setpoint setting unit configured to set a setpoint of the difference between the remaining electrical capacity of the first electricity storage device and the remaining electrical capacity of the second electricity storage device based on a control state of the low-voltage load, wherein, in the case where the state of the plurality of electricity storage devices is the parallel circuit state, the current control unit controls the charging and discharging currents for each of the electricity storage devices by adjusting the resistance values ​​of the variable resistance units such that the difference between the remaining electrical capacity of the first electricity storage device and the remaining electrical capacity of the second electricity storage device becomes the setpoint. [7] Power supply control device according to any one of claims 1 to 6, wherein the current control unit controls the charging and discharging currents of the electricity storage devices by changing the resistance values ​​of the variable resistance units to larger values ​​in a state in which the plurality of electricity storage devices is connected in parallel. [8] Power supply control device according to any one of claims 1 to 7, comprising: a power procurement unit configured to procure the charging and discharging currents of the multitude of electricity storage devices, wherein the current control unit sets the resistance values ​​of the variable resistance units based on the charging and discharging currents flowing through the multitude of electricity storage devices. [9] Power supply control device according to any one of claims 1 to 8, comprising: a parameter procurement unit that is configured to procure electricity storage state parameters that have an interaction with magnitudes of currents flowing through power supply paths that include a path between the plurality of electricity storage devices in the parallel state or in the series state, as parameters that specify the states of the plurality of electricity storage devices; and a resistance control unit configured to adjust a resistance value of a variable resistance unit (22) located between the plurality of electricity storage devices in the power supply path in the parallel state or a resistance value of a variable resistance unit (25) located between the plurality of electricity storage devices in the power supply path in the series state. [10] Power supply control device according to claim 9, wherein the switching unit switches a state of the plurality of electricity storage devices between the series connection state and the parallel connection state in response to a switching request, and The resistance control unit adjusts the resistance values ​​based on the electricity storage state parameters after the state of the multitude of electricity storage devices has been switched from the series connection state to the parallel connection state in response to the switching request. [11] Power supply control device according to claim 9 or 10, wherein the switching unit switches the state of the plurality of electricity storage devices between the series connection state and the parallel connection state in response to the switching request, and The resistance control unit adjusts the resistance values ​​based on the electricity storage state parameters after the state of the multitude of electricity storage devices has been switched from the parallel circuit state to the series circuit state in response to the switching request. [12] Power supply control device according to one of claims 9 to 11, wherein the parameter procurement unit procures at least one of the charging and discharging currents, connection voltages and remaining electrical capacitances of at least one of the plurality of electricity storage devices as the electricity storage state parameters, and The resistance control unit adjusts the resistance values ​​based on a procurement result by the parameter procurement unit. [13] Power supply control device according to any one of claims 9 to 12, wherein the parameter procurement unit procures a temperature of at least one of the plurality of electricity storage devices as the electricity storage state parameters, and The resistance control unit adjusts the resistance values ​​based on a procurement result by the parameter procurement unit. [14] Power supply control device according to any one of claims 1 to 13, wherein the variable resistor units are configured with semiconductor switching elements and The current control unit adjusts the resistance values ​​of the semiconductor switching elements in an ON state. [15] Power supply control device according to any one of claims 1 to 13, wherein, in the case where the state of the plurality of electricity storage devices is the parallel circuit state, the current control unit controls the charging and discharging currents for each of the electricity storage devices by adjusting the resistance values ​​of the switching devices using the switching devices as the variable resistance units. [16] Power supply control device according to claim 15, wherein the switching devices are configured with semiconductor switching elements and The current control unit adjusts the resistance values ​​of the semiconductor switching elements in an ON state. [17] Power supply control device according to claim 14 or 16, wherein the current control unit adjusts the resistance values ​​of the semiconductor switching elements by means of a digital / analog control or a PWM control. [18] Power supply control device according to any one of claims 1 to 17, comprising: a determination unit configured to determine whether a difference in the remaining electrical capacities of the multitude of electricity storage devices falls within a predetermined range or not; and a switching control unit that is configured, in a case where it is determined that the difference in the remaining electrical capacities of the plurality of electricity storage devices falls within the predetermined range, allows a transition of the state of the plurality of electricity storage devices from the parallel state to the series state. [19] Power supply system with: the plurality of electricity storage devices (12, 13), wherein the plurality of electricity storage devices comprises a first electricity storage device (12) whose positive side is connected to a low-voltage load (14) in a low-voltage system in the series-connected state, and a second electricity storage device (13) whose positive side is connected to a high-voltage load (15, 16) in a high-voltage system in the series-connected state; a switching unit comprising a plurality of switching devices (21 to 25) provided at electrical paths leading to the electricity storage devices, and configured to switch a state of the plurality of electricity storage devices between a parallel state in which the plurality of electricity storage devices are connected in parallel to each other and a series state in which the plurality of electricity storage devices are connected in series to each other, and the power supply control device according to any one of claims 1 to 18. [20] Power supply system according to claim 19, wherein the maximum amounts of electricity that may be stored in the first electricity storage device and in the second electricity storage device are different from each other. [21] Power supply system according to claim 19, wherein, in a case where the state of the plurality of electricity storage devices is the parallel circuit state, the current control unit adjusts the resistance values ​​of the variable resistance units such that a remaining electrical capacity of the first electricity storage device becomes greater than a remaining electrical capacity of the second electricity storage device, and the maximum amount of electricity that may be stored in the first electricity storage device is greater than the maximum amount of electricity that may be stored in the second electricity storage device. [22] Power supply system equipped with a large number of electricity storage devices (12, 13); a switching unit comprising a plurality of switching devices (21 to 25) provided at electrical paths leading to the electricity storage devices, and configured to switch a state of the plurality of electricity storage devices between a parallel state in which the plurality of electricity storage devices are connected in parallel to each other and a series state in which the plurality of electricity storage devices are connected in series to each other, and a power supply control device (30), wherein the plurality of electricity storage devices comprises a first electricity storage device (12) whose positive side is connected to a low-voltage load (14) in a low-voltage system in the series connection state, and a second electricity storage device (13) whose positive side is connected to a high-voltage load (15, 16) in a high-voltage system in the series connection state; the power supply control device (30) comprises: a capacity procurement unit configured to procure the respective remaining electrical capacities of the multitude of electricity storage facilities; and A current control unit configured to control charging and discharging currents for each of the electricity storage devices in a case where the state of the plurality of electricity storage devices is the parallel circuit state, by adjusting resistance values ​​of variable resistor units present in the electrical paths leading to the electricity storage devices, based on the remaining electrical capacities of the electricity storage devices procured by the capacity procurement unit, such that a difference between the remaining electrical capacity of the first electricity storage device and a remaining electrical capacity of the second electricity storage device becomes a desired amount. The current control unit adjusts the resistance values ​​of the variable resistance units such that the remaining electrical capacity of the first electricity storage device becomes greater than the remaining electrical capacity of the second electricity storage device, and the maximum amount of electricity that may be stored in the first electricity storage device is greater than the maximum amount of electricity that may be stored in the second electricity storage device.

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