Power supply system and method for controlling the power supply system

Abstract

To provide a power system including multiple assembled batteries connected in parallel capable of charging all assembled batteries to full charge while executing equalization control on a fully charged assembled battery.SOLUTION: A power system P includes multiple battery units Bu connected in parallel. The battery unit Bu includes a battery pack 1 and a converter 2. A control unit 3 controls the converter 2 to charge the battery unit Bu (battery pack 1) until the same is fully charged. When the battery unit Bu (battery pack 1) is fully charged, the control unit executes equalization control for equalizing the voltage between cells in the battery pack 1 (assembled battery).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a power supply system and a control method for the power supply system, and more particularly to a power supply system in which a plurality of battery units, each including a battery pack and a converter, are connected in parallel, and a control method for the power supply system. [Background technology]

[0002] JP 2014-103804 A (Patent Document 1) discloses a technology for equalizing the voltages of multiple battery packs in a battery system in which multiple battery packs are connected in parallel. In addition, JP 2020-60581 A (Patent Document 2) discloses the existence of a battery whose OCV (Open Circuit Voltage)-SOC (State Of Charge) characteristics show a flat region (voltage plateau region) over a wide range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-103804 A [Patent Document 2] JP 2020-60581 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to eliminate the variation in SOC of the cells that constitute a battery pack, an equalization control that equalizes the voltage of the cells is known. In the case of a battery having a voltage plateau region in the OCV-SOC characteristics as disclosed in Patent Document 2, even if the equalization control of the cells is performed in the voltage plateau region, the SOC cannot be accurately estimated in the voltage plateau region, so the variation in SOC may not be effectively eliminated. For this reason, in the case of a battery having a voltage plateau region in the OCV-SOC characteristics, it is useful to charge the battery until it is fully charged and perform the equalization control on the battery in the fully charged state.

[0005] However, in a power supply system in which a plurality of assembled batteries are connected in parallel to a power conversion device as in Patent Document 1, it is not possible to fully charge all of the assembled batteries due to differences in internal resistance among the assembled batteries, etc.

[0006] An object of the present disclosure is to enable, in a power supply system consisting of a plurality of battery packs connected in parallel, to charge all of the battery packs until they are fully charged, and to perform equalization control on the battery packs that are in a fully charged state. [Means for solving the problem]

[0007] The power supply system disclosed herein is a power supply system that charges and discharges between an external system. The power supply system includes a battery unit including a battery pack and a converter, and a control device that controls the battery unit, and the battery units are connected in parallel. The control device is configured to control the converter to charge the battery pack until it is fully charged, and to execute equalization control to equalize the voltages of the cells of the battery pack that has been fully charged.

[0008] According to this configuration, the battery unit is composed of a battery pack and a converter. A power supply system is formed by connecting a plurality of battery units in parallel. Since the battery unit is composed of a battery pack and a converter, the charging and discharging of the battery pack can be controlled by the converter, and by controlling the converter, it is possible to charge the battery pack until it is fully charged. A control device that controls the battery unit controls the converter to charge the battery pack until it is fully charged, and executes equalization control to equalize the voltages of the cells of the battery pack that has been fully charged. This makes it possible to charge the battery pack until it is fully charged, and execute equalization control to equalize the voltages of the cells of the battery pack in the fully charged state.

[0009] If the battery pack is charged to full charge every time a predetermined period has elapsed since the battery pack was last fully charged, the cells of the battery pack can be equalized at appropriate intervals by setting the predetermined period. The predetermined period may be set, for example, according to the variation in the self-discharge amount of the cells and the variation in the impedance of the voltage detection circuit, and may be, for example, 30 days.

[0010] In particular, when the battery pack is made up of multiple iron phosphate lithium-ion battery cells connected in series, a plateau voltage region exists in the OCV-SOC characteristics, so it is effective to charge the battery pack until it is fully charged and equalize the voltages of the cells in the battery pack when it is fully charged.

[0011] The control method disclosed herein is a method for controlling a power supply system in which a plurality of battery units, each including a battery pack and a converter, are connected in parallel and charge / discharge between the battery pack and an external system. The control method includes a step of controlling the converter to charge the battery pack until it is fully charged, and a step of executing equalization control to equalize the voltages of the cells of the battery pack that has been fully charged.

[0012] According to this control method, the converter is controlled to charge the assembled battery until it is fully charged, and when the assembled battery is in the fully charged state, equalization control can be executed to equalize the voltages of the cells in the assembled battery. Effect of the Invention

[0013] According to the present disclosure, in a power supply system consisting of a plurality of battery packs connected in parallel, it is possible to charge all of the battery packs until they are fully charged, and to execute equalization control on the battery packs that are in a fully charged state. [Brief description of the drawings]

[0014] [Figure 1] 1 is a diagram showing an overall configuration of a power supply system according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a diagram illustrating an example of an electric vehicle. [Diagram 3]FIG. 4 is a diagram illustrating an example of an equalization circuit included in the monitoring unit. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a control device of a power supply system. [Diagram 5] 4 is a flowchart showing an example of an equalization control process executed in the control device. [Figure 6] FIG. 13 is a diagram illustrating a control device of a power supply system according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0016] Fig. 1 is a diagram showing the overall configuration of a power supply system P of this embodiment. The power supply system P includes a power supply subunit Su including three battery packs 1 and a converter 2, and a control device 3. In this embodiment, the power supply subunit Su is a battery pack and a PCU (Power Control Unit) mounted on an electric vehicle that have been converted for use in the power supply system P. An example of the configuration of an electric vehicle equipped with a battery pack and a PCU will be described.

[0017] Fig. 2 is a diagram illustrating an example of an electric vehicle. In Fig. 2, the electric vehicle V is a hybrid vehicle that uses both a rotating electric machine and an engine to drive the vehicle. The electric vehicle V includes a battery pack 1, a PCU 20, an engine 30, motor generators MG1 and MG2 as rotating electric machines, a power split mechanism 40, and drive wheels 50.

[0018] The battery pack 1 includes a battery 10 and a system main relay (SMR) 11. The battery 10 is an assembled battery in which single cells, such as secondary batteries such as nickel-metal hydride batteries and lithium-ion batteries, are electrically connected in series. The output terminals (positive terminal, negative terminal) of the battery pack 1 are connected to a battery connection terminal 25 of the PCU 20. When the SMR 11 is closed, the battery 10 and the PCU 20 are connected, and when the SMR 11 is opened, the connection between the battery 10 and the PCU 20 is cut off. The battery pack 1 is provided with a monitoring unit 15, which detects the voltage VB of the battery 10, the input / output current IB of the battery 10, the temperature of the battery 10, and the like.

[0019] The PCU 20 includes a boost converter 21, an inverter 22, and an inverter 23. The boost converter 21 boosts the battery voltage VB input from the battery pack 1 and outputs it to the inverter 22 and the inverter 23. The inverter 22 converts the DC power boosted by the boost converter 21 into three-phase AC power, and drives the motor generator MG1 to start the engine 30, for example. The inverter 22 also converts AC power generated by the motor generator MG1 using the power transmitted from the engine 30 into DC power and returns it to the boost converter 21. At this time, the boost converter 21 is controlled to operate as a step-down circuit. The inverter 23 converts the DC power output from the boost converter 21 into three-phase AC power and outputs it to the motor generator MG2.

[0020] The power split mechanism 40 is a mechanism that is connected to the engine 30 and the motor generators MG1, MG2 and distributes power therebetween. A planetary gear mechanism can be used as the power split mechanism 40, and for example, the engine 30 is connected to a planetary carrier, the motor generator MG1 is connected to a sun gear, and the motor generator MG2 is connected to a ring gear. The rotor of the motor generator MG2 (and the rotating shaft of the ring gear of the power split mechanism 40) is connected to the drive wheels 50 via a reduction gear, a differential gear, and a drive shaft (not shown).

[0021] The boost converter 21 of the PCU 20 includes a reactor and switching elements Q1a, Q1b, Q2a, and Q2b. The switching elements Q1a to Q2b are, for example, IGBT (Insulated Gate Bipolar Transistor) elements, and include diodes connected in anti-parallel to each IGBT element. The switching elements Q1a and Q1b are provided in parallel, and the switching elements Q2a and Q2b are provided in parallel, with the switching elements Q1a and Q1b driven by the same drive signal, and the switching elements Q2a and Q2b driven by the same drive signal.

[0022] Inverter 22 is a three-phase inverter and includes a U-phase arm made up of switching elements Q3 and Q4 connected in series between positive electrode line Pl and negative electrode line Nl, a V-phase arm made up of switching elements Q5 and Q6 connected in series between positive electrode line Pl and negative electrode line Nl, and a W-phase arm made up of switching elements Q7 and Q8 connected in series between positive electrode line Pl and negative electrode line Nl. Similar to switching element Q1a, switching elements Q3 to Q8 are switching elements including diodes connected in anti-parallel to IGBT elements.

[0023] The midpoint of the arm of each phase is connected to the coil of each phase of motor generator MG1 via MG1 connection terminal 26. Motor generator MG1 is a three-phase permanent magnet synchronous motor, and may be, for example, an IPM (Interior Permanent Magnet) synchronous motor.

[0024] The inverter 23 is a three-phase inverter similar to the inverter 22, except that the switching elements of the arms of each phase are arranged in parallel. Switching elements Q9a and Q9b correspond to switching element Q3, and switching elements Q10a and Q10b correspond to switching element Q4, forming a U-phase arm. Switching elements Q11a and Q11b correspond to switching element Q5, and switching elements Q12a and Q12b correspond to switching element Q6, forming a V-phase arm. Switching elements Q13a and Q13b correspond to switching element Q7, and switching elements Q14a and Q14b correspond to switching element Q8, forming a W-phase arm.

[0025] The midpoint of the arm of each phase is connected to the coil of each phase of motor generator MG2 via MG2 connection terminal 27. Motor generator MG2 may also be an IPM synchronous motor.

[0026] The electric vehicle V includes, as control devices, a hybrid ECU (Electronic Control Unit) (HV-ECU) 200, a motor generator ECU (MG-ECU) 210, a battery ECU (BT-ECU) 220, and an engine ECU (EG-ECU) 230. Each ECU includes a CPU (Central Processing Unit), a memory, and a buffer (none of which are shown).

[0027] The monitoring unit 15 includes a voltage detection circuit VB for detecting the voltage (battery voltage) VB and cell voltage (single cell voltage) Vb of the battery 10, a current sensor IB for detecting an input / output current IB, etc. The monitoring unit 15 also includes an equalization circuit for equalizing the voltages of the single cells of the battery 10, as described later. The BT-ECU 220 calculates the SOC of the battery 10 based on the voltage VB and the input / output current IB detected by the monitoring unit 15, and transmits the SOC to the HV-ECU 200.

[0028] For the purpose of driving control of electric vehicle V, HV-ECU 200 sets target engine rotation speed Ne, target engine torque Te, command torque Tm1 for motor generator MG1, and command torque Tm2 for motor generator MG2.

[0029] The MG-ECU 210 performs PWM (Pulse Width Modulation) control on each switching element of the inverter 22 so that the command torque Tm1 is output from the motor generator MG1. The MG-ECU 210 also performs PWM control on each switching element of the inverter 23 so that the command torque Tm2 is output from the motor generator MG2.

[0030] The EG-ECU 230 controls the engine 30 so that the engine 30 is operated at a target engine speed Ne and a target engine torque Te.

[0031] 3 is a diagram showing an example of an equalization circuit EQ provided in the monitoring unit 15. In the battery 10, a plurality of single batteries (cells) 101-10M are connected in series. A voltage detection circuit VB detects the voltages of the single batteries 101-10M via a plurality of voltage detection lines L1, a branch line L11, and a branch line L12. A fuse F and chip beads Cb are provided in the voltage detection line L1 for circuit protection and the like, and the voltage detection circuit VB is protected from overvoltage by a Zener diode D provided in parallel with the single batteries 101-10M.

[0032] The voltage detection line L1 branches into a branch line L11 and a branch line L12 on the monitoring unit 15 side of the Zener diode D. The branch line L11 is connected to the comparator 21a via a switch So, and the branch line L12 is connected to the comparator 21a via a switch Sh. The switches So and Sh may be, for example, photo MOS (Metal Oxide Semiconductor) relays.

[0033] A resistor R1 is provided on the branch line L12. A capacitor (flying capacitor) C is provided between the branch line L12 connected to the positive terminal of each cell and the branch line L11 connected to the negative terminal. This allows the monitoring unit 20 to detect the cell voltage Vb of each cell 101-10M using the voltage detection circuit VB by the flying capacitor method, by sequentially turning on the switches Sh and So corresponding to each cell 101-10M. In addition, by turning on (closing) the switch Sh of the cell 101 and the switch So connected to the negative terminal of the cell 10M, the voltage VB of the battery 10 can be detected.

[0034] The equalization circuit EQ is composed of a discharge resistor Rd provided in the branch line L11 and a switch S1 that connects (closes) / disconnects (opens) between adjacent branch lines L11. The switch S1 switches between ON (closed) and OFF (open) upon receiving a control signal from the BT-ECU 220. When the cell voltage Vb of the cell 102 is higher than the cell reference voltage, the switch S1 corresponding to the cell 102 is turned ON (closed). Then, as shown by the dashed-dotted arrow, the current discharged from the cell 102 is consumed by the discharge resistors Rd, Rd, the cell voltage Vb of the cell 102 drops, and the cell voltages are equalized. In this manner, the battery cells of the battery 10 (battery pack) are equalized.

[0035] Referring again to FIG. 1, in the power supply system P, the battery pack 1 and the converter 2 are repurposed battery packs 1 and PCU 20 mounted on an electric vehicle V. The positive terminals of the output terminals of the three battery packs 1 (1-1-1, 1-1-2, 1-1-3) are connected to an MG2 connection terminal 27 to which the midpoints of the phase arms (U-phase arm, V-phase arm, W-phase arm) of an inverter 23 (three-phase inverter) of the PCU 20 are connected, via a coil (inductor) 5. The power line between the positive terminal of the battery pack 1 and the coil 5 is connected to the negative terminal of the output terminal of the battery pack 1, via a capacitor 6. The negative terminal of the battery pack 1 is connected to the negative line Nl of the PCU 20 by a power line Nl1. For convenience, the monitoring unit 15 is partially omitted in FIG. 1.

[0036] 1, switching elements Q4, Q5, and Q7 of inverter 22 of PCU 20 are short-circuited. In MG1 connection terminal 26 to which the midpoints of the arms of each phase of inverter 22 are connected, a terminal to which the U-phase arm is connected is connected to the negative terminal of battery connection terminal 25 by power line Nl2. The negative terminal of battery connection terminal 25 is connected to negative terminal 28b of power supply subunit Su. In MG1 connection terminal 26, a terminal to which the V-phase arm and W-phase arm are connected is connected to positive terminal 28a of power supply subunit Su by power line Pl1.

[0037] In this way, by connecting each phase arm of the inverter 23 of the PCU 20 to the battery pack 1, shorting some of the switching elements of the inverter 22, and connecting the MG1 connection terminal 26 to the positive terminal 28a and negative terminal 28b of the power supply subunit Su, the PCU 20 is converted into a converter 2 that controls the voltage of the battery pack 1 (battery 10) connected to each phase arm of the inverter 23.

[0038] In FIG. 1, the battery pack 1 or the battery 10 included in the battery pack 1 corresponds to an example of the "battery pack" of the present disclosure. A chopper circuit consisting of each phase arm, a coil 5, and a capacitor 6 corresponding to one battery pack 1 (connected to one battery pack 1) corresponds to the "converter" of the present disclosure. In FIG. 1, for convenience, three converters are collectively labeled with the reference symbol 2. A configuration including the battery pack 1 and one converter 2 corresponds to the "battery unit" of the present disclosure. For example, in FIG. 1, the battery pack 1-1-1, the U-phase arm (switching elements Q9a, Q9b, Q10a, Q10b), the coil 5 connected to the midpoint of the U-phase arm, and the capacitor 6 provided in the power line between the positive terminal of the battery pack 1-1-1 and the coil 5 correspond to the "battery unit" of the present disclosure. In the description of the present embodiment, the battery units are denoted by the reference symbol Bu without distinguishing between the battery units.

[0039] The power supply subunit Su is composed of three battery units Bu including a converter 2 that is a repurposed PCU 20. In the power supply subunit Su, the battery units Bu are connected in parallel. The power supply system P includes a plurality of power supply subunits Su, and each power supply subunit Su is connected in parallel to the PCS 100. In this embodiment, the power supply subunit Su includes n (n is a positive integer) power supply subunits Su, and may include, for example, 20 power supply subunits Su. Three battery units Bu (battery packs 1) are connected in parallel to the power supply subunit Su, and in the power supply system P including 20 power supply subunits Su, 60 battery units Bu (battery packs 1) are connected in parallel. In FIG. 1, n in the symbol Su-n indicates that it is the n-th power supply subunit Su. n in the symbols 1-n-1, 1-n-2, and 1-n-3 indicates the battery pack 1 included in the n-th power supply subunit Su.

[0040] The positive terminal 28a of each power supply subunit Su is connected via a positive line PL to an input / output terminal of the PCS 100. The negative terminal 28b of each power supply subunit Su is connected via a negative line NL to an input / output terminal of the PCS 100.

[0041] The PCS100 is connected to a power system P, a power grid PG, a photovoltaic power generation device 650, and a load (electrical load) 300. The power system PG is, for example, a commercial power source formed from a power plant or a power transmission network. The PCS100 includes a power conversion device, and supplies power generated by the photovoltaic power generation device 650 to the load 300 and performs reverse power flow. The PCS100 converts AC power of the power system PG to DC power and charges the power system P (battery unit Bu). The PCS100 converts discharge power (output power) of the power system P (battery unit Bu) to AC power and supplies it to the load 300 and performs reverse power flow. The load 300 may be a household load (home appliance) or an electrical load in an office or factory.

[0042] 4 is a diagram showing an example of the configuration of the control device 3 of the power supply system P. The control device 3 utilizes the HV-ECU 200, the MG-ECU 210, and the BT-ECU 220 of the electric vehicle V. The H / HV-ECU 220a, and the HV-ECU(1) 220a-1 to the HV-ECU(3) 220a-3 utilize the HV-ECU 200. The MG-ECU 210a utilizes the MG-ECU 210. The BT-ECU 220a1 to the BT-ECU 220a-3 utilize the BT-ECU 220.

[0043] In FIG. 4, the PCS-ECU 500 is a control device that controls the PCS 100, and outputs a power command RP that is a required value of power output from the power supply system P (battery unit Bu) or a required value of power input to the power supply system P, and a voltage command RV that is a command value of the voltage output from the power supply system P. An interface ECU (I / F-ECU) 600 connects the PCS-ECU 500 and a control device 3 (H / HV-ECU 200a), and performs matching between the communication protocol of the PCS-ECU 500 and the communication protocol of the control device 3. The H / HV-ECU 200a outputs a command to control the battery unit Bu based on the power command RP, the voltage command RV, and the like received from the PCS-ECU 500. The H / HV-ECU 200a also outputs a command for charging control of the battery unit Bu (battery 10).

[0044] The sub-control device 3a1 is a control device that controls the power supply subunit Su, which is composed of the MG-ECU 210a, the HV-ECU(1) 220a-1 to the HV-ECU(3) 220a-3, and the BT-ECU 220a1 to the BT-ECU 220a-3. In Fig. 4, the sub-control device 3a1-1 is a control device that controls the power supply subunit Su-1 in Fig. 1, and a sub-control device 3a1 is provided for each power supply subunit Su. In other words, the control device 3a has n sub-control devices 3a1, namely, the sub-control device 3a1-1 to the sub-control device 3a1-n.

[0045] 4, the BT-ECU(1) 220a-1 monitors the voltage VB, input / output current IB, temperature, etc. of the battery 10 of the battery pack 1-1-1 of the power supply subunit Su-1, and executes equalization control of the battery pack 1-1-1. The BT-ECU(2) 220a-2 and the HV-ECU(3) 200a-3 perform similar processing on the battery packs 1-1-2 and 1-1-3. The MG-ECU 210a controls the converter 2 (drives the switching elements of each phase arm of the inverter 23) based on a command from the H / HV-ECU 200a.

[0046] Sub-controllers 3a1-2 to 3a1-n also perform the same processing as sub-controller 3a1-1 with respect to power supply subunits Su-2 to Su-n.

[0047] In this embodiment, the battery pack 1 (battery 10) is a battery pack made of lithium ion batteries, and is made up of multiple types of lithium ion batteries. One type of lithium ion battery may be an iron phosphate lithium ion battery (LFP battery). Other types of lithium ion batteries may be ternary lithium ion batteries, manganese lithium ion batteries, NCA lithium ion batteries, etc.

[0048] FIG. 5 is a flowchart showing an example of the equalization control process executed by the control device 3. This flowchart is repeatedly processed at predetermined time intervals while the power supply system P is in operation. In step (hereinafter, step is abbreviated as "S") 10, the H / HV-ECU 200a judges whether or not there is a battery unit Bu (battery 10) for which a predetermined period α has elapsed since the battery unit Bu was last fully charged. The predetermined period α may be set, for example, according to the variation in the self-discharge amount of the single battery (cell) or the variation in the impedance of the voltage detection circuit VB, and may be, for example, 30 days. Alternatively, it may be judged that the predetermined period α has elapsed when the operating time of the battery unit Bu (battery 10) exceeds 1000 hours since the battery unit Bu was last fully charged.

[0049] If there is no battery unit Bu for which the predetermined period α has elapsed since the previous full charge, a negative determination is made in S10 and the routine ends. If there is a battery unit Bu for which the predetermined period α has elapsed since the previous full charge, a positive determination is made in S10 and the routine proceeds to S12.

[0050] In S12, the converter 2 of the battery unit Bu for which the predetermined period α has elapsed (hereinafter, the battery unit Bu is also referred to as the target battery unit Bu) is controlled to charge the battery pack 1 (battery 10) of the target battery unit Bu. The target battery unit Bu may be charged by power supplied from the power system PG, or may be charged by power supplied from another battery unit Bu.

[0051] Next, in S14, it is determined whether the target battery unit Bu is fully charged. The charging of the target battery unit Bu in S12 is CV (Constant Voltage) charging, at least when it is close to full charge. For example, CCCV (Constant Current, Constant Voltage) charging is performed, charging at a constant current until the battery 10 reaches a predetermined voltage, and when the voltage VB of the battery 10 reaches a specified value, charging at a constant voltage is performed. In S14, when the charging current during CV charging becomes equal to or lower than a set value, it is determined that the battery is fully charged. Note that CV charging is not limited to CCCV charging, and CV charging may be performed from the start of charging, or CPCV (Constant Power, Constant Voltage) charging may be performed.

[0052] When the charging current falls below the set value and it is determined in S14 that all the target battery units Bu are fully charged (positive determination), the process proceeds to S16. If all the target battery units Bu are not fully charged, a negative determination is made in S14, the process returns to S12, and charging is continued until all the target battery units Bu are fully charged.

[0053] In S16, the control device 3 (BT-ECU(1) 220a-1 to BT-ECU(3) 220a-3) judges whether or not to execute cell equalization of the batteries 10 included in each of the target battery units Bu that are fully charged. In the following, the battery 10 included in the target battery unit Bu is also referred to as the "target battery." For example, when the deviation between the maximum and minimum values ​​of the cell voltage Vb of the target battery is equal to or greater than a set value, it is judged that cell equalization of the target battery is required (positive judgment), and the process proceeds to S18. When the deviation between the maximum and minimum values ​​of the cell voltage Vb of the target battery is less than the set value, it is judged that cell equalization of the target battery is not required (negative judgment), and when it is judged that cell equalization of all the target batteries is not required, the current routine is terminated.

[0054] In S18, equalization control between the battery cells of the target battery is executed. For example, the converter 2 of the battery unit Bu of the target battery determined to require equalization is stopped (the switching elements of each phase arm are turned off). Then, the average value of the cell voltage Vb calculated excluding the maximum and minimum values ​​of the cell voltage Vb of the target battery is set as the cell reference voltage, and discharge is performed from the single battery showing a cell voltage higher than the cell reference voltage (current is consumed by the discharge resistors Rd, Rd), thereby executing the equalization control between the cells of the target battery. When the equalization control between the cells of all the target batteries determined to require equalization is completed, the current routine is terminated.

[0055] According to this embodiment, the battery unit Bu is composed of a battery 10 (battery pack) and a converter 2. A plurality of battery units Bu are connected in parallel to constitute a power supply system P. Since the battery unit Bu is composed of the battery 10 and the converter 2, each battery unit Bu (battery 10) can be charged to full charge by controlling the converter 2. The control device 3 executes equalization control to equalize the voltages of the cells of the battery 10 (battery pack) that has been fully charged (S18). This allows the battery 10 to be charged to full charge, and in the fully charged state, equalization control can be executed to equalize the voltages of the cells of the battery 10.

[0056] The battery pack 1 (battery 10) of this embodiment is composed of multiple types of lithium ion batteries, including LFP batteries. In particular, when the battery 10 is composed of an LFP battery, the battery 10 is fully charged and the voltages of the cells of the battery 10 are equalized in the fully charged state, so that the cell voltages can be equalized in the voltage gradient region, not the voltage plateau region, of the OCV-SOC characteristics, and the SOC variations between the cells can be effectively eliminated.

[0057] According to the above embodiment, the converter 2 of the battery unit Bu is a repurposed inverter 23 (three-phase inverter) included in the PCU 20 of the electric vehicle V. In addition, the battery pack 1 of the electric vehicle V is used as the battery pack 1 of the battery unit Bu. This makes it possible to promote the reuse of batteries and PCUs that are collected when the electric vehicle V is replaced or dismantled.

[0058] (Modification) 6 is a diagram showing an overall configuration of a power supply system Pa in a modified example. In the above embodiment, an example has been described in which PCU 20 including boost converter 21, inverter 22, and inverter 23 is diverted to converter 2 of power supply system P. In the above embodiment, in particular, inverter 23 having switching elements provided in parallel is used as the switching element of converter 2 in order to enable the passage of large power. However, some PCUs mounted on electric vehicles are provided with one inverter, and some PCUs are not provided with a boost converter.

[0059] The power supply system Pa in the modified example is a PCU equipped with only one inverter, or a circuit in which the inverter portion is extracted from the PCU and used as the converter 2A of the power supply system Pa.

[0060] In FIG. 6, the converter 2A is a repurposed inverter (three-phase inverter) of a PCU mounted on an electric vehicle. In FIG. 6, SR1 and SR2 of the battery pack 1 are system main relays (SMR). As in the above embodiment, the positive terminals of the output terminals of the three battery packs 1 (1-1-1, 1-1-2, 1-1-3) are connected to the midpoints of the phase arms (U-phase arm 2A1, V-phase arm 2A2, W-phase arm 2A3) of the three-phase inverter of the PCU via coils (inductors) 5. The power line between the positive terminal of the battery pack 1 and the coil 5 is connected to the negative terminal of the output terminal of the battery pack 1 via a capacitor 6. The upper arms of the phase arms (U-phase arm 2A1, V-phase arm 2A2, W-phase arm 2A3) of the three-phase inverter are connected to a positive line PL and are connected to the input / output terminals of the PCS 100. The lower arms of each phase arm (U-phase arm 2A1, V-phase arm 2A2, W-phase arm 2A3) of the three-phase inverter are connected to a negative line NL and connected to an input / output terminal of the PCS 100. The negative terminal of the battery pack 1 is connected to the negative line NL. Note that the monitoring unit 15 is not shown in the figure.

[0061] In the above embodiment and modified example, a power supply system in which a three-phase inverter is converted into a converter has been described. However, the converter constituting the battery unit Bu does not have to be a three-phase inverter, and each battery unit Bu may be provided with an independent chopper circuit (converter).

[0062] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0063] 1 battery pack, 2, 2A converter, 3 control device, 5 coil (inductor), 6 capacitor, 10 battery, 11 SMR, 15 monitoring unit, 20 PCU, 21 boost converter, 22, 23 inverter, 25 battery connection terminal, 26 MG1 connection terminal, 27 MG2 connection terminal, 28a positive terminal, 28b negative terminal, 30 engine, 40 power split mechanism, 50 drive wheel, 100 PCS, 200 HV-ECU, 210 MEG-ECU, 220 BT-ECU 230 EG-ECU, 300 load, 500 PCS-ECU, 600 I / F-ECU, 650 solar power generation device, Bu battery unit, MG1 motor generator, MG2 motor generator, Su power supply sub-unit, P, Pa power supply system, PG power system, V electric vehicle.

Claims

1. A power supply system that charges and discharges between an external system, a battery unit including a battery pack and a converter; A control device that controls the battery unit, A plurality of the battery units are connected in parallel, the converter is a converted three-phase inverter, and the battery pack is connected to each phase arm of the three-phase inverter; The control device includes: Controlling the converter so as to charge the assembled battery until it is fully charged; The power supply system is configured to execute an equalization control for equalizing the voltages of the cells of the battery pack that have been fully charged.

2. 2 . The power supply system according to claim 1 , wherein the control device controls the converter so as to charge the battery pack until it is fully charged every time a predetermined period of time has elapsed since the battery pack was previously fully charged.

3. 3. The power supply system according to claim 1, wherein the battery pack comprises a plurality of lithium ion iron phosphate batteries connected in series.

4. A control method for a power supply system in which a plurality of battery units, each including a battery pack and a converter, are connected in parallel and charge / discharge between the battery units and an external system, the control method comprising the steps of: the converter is a converted three-phase inverter, and the battery pack is connected to each phase arm of the three-phase inverter; The control method includes: controlling the converter to charge the battery pack until it is fully charged; executing an equalization control for equalizing the voltages of the cells of the battery pack that has been fully charged; A method for controlling a power supply system, comprising:

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