Battery system

Abstract

The objective of this invention is to achieve high-precision, time-independent equalization even when at least one of the state of charge (SOC) of a single cell in a battery is in a plateau region, with minimal power waste. In a series of battery packs connected in parallel, a specific battery pack includes: a battery consisting of multiple single cells having plateau and non-plateau regions on their charge-discharge curves connected in series; and an equalization unit that equalizes the SOC of each single cell. At a predetermined equalization time for a specific battery pack, the PCU controlling the power exchange between battery packs and the BEV-ECU of the equalization unit control the PCU to exchange power with other battery packs, thereby enabling the single cells of the specific battery pack to reach a non-plateau region of charge (step S113). After each single cell in the specific battery pack reaches a non-plateau region, the equalization unit controls the equalization unit to equalize the SOC of each single cell (step S123).

Description

Technical Field

[0001] This invention relates to a battery system, and more particularly to a battery system capable of charging and discharging electricity. Background Technology

[0002] Lithium iron phosphate (LFP) batteries are secondary batteries with a plateau region of cell voltage variation that is flat in relation to changes in SOC in their State of Charge (SOC) - Open Circuit Voltage (OCV) characteristics. Conventionally, there are techniques that utilize two variation points in the plateau region of the LFP battery to perform SOC equalization of the cells in a battery pack using LFP batteries as cell units (for example, see paragraph 0042 of Patent Document 1).

[0003] Patent Document 1: Japanese Patent No. 6032473 Summary of the Invention

[0004] However, in the plateau region, the change in cell voltage in response to changes in SOC is small, so equalizing SOC in the plateau region is not easy.

[0005] The present invention was made to solve the above-mentioned problems, and its object is to provide a battery system that can perform equalization with high precision and without time constraints in a manner that minimizes power waste, even when at least one of the battery cells contained in the battery pack is in a plateau region of SOC.

[0006] The battery system of this invention is a system consisting of multiple battery packs capable of charging and discharging electricity connected in parallel. A specific battery pack includes: a battery bank, which is formed by multiple battery cells having plateau regions and non-plateau regions on a charge-discharge curve connected in series; and an equalization circuit that equalizes the state of charge (SOC) of each battery cell. The battery system includes: a switching circuit that facilitates power exchange between battery packs; and a processor that controls the switching circuit and the equalization circuit. The processor performs the following processing: at a predetermined equalization time for a specific battery pack, it controls the switching circuit to facilitate power exchange with other battery packs, so that the battery cells of the specific battery pack reach the non-plateau region of charge; and after each battery cell of the specific battery pack reaches the non-plateau region, it controls the equalization circuit to equalize the SOC of each battery cell.

[0007] According to this structure, power is exchanged with other battery packs in a manner where the battery cells of a specific battery pack, which are being equalized, are in a non-platform region of charge, and equalization is performed in the non-platform region. As a result, a battery system can be provided that can perform equalization with high precision and without time constraints in a manner that minimizes power waste, even when at least one of the battery cells contained in the battery pack is in a plateau region of SOC.

[0008] The processor can perform the following processing: when it is not possible to exchange power between other battery packs and a specific battery pack, use external power to make the battery cells of the specific battery pack charge the non-platform area.

[0009] According to this structure, even when power exchange between other battery packs and a specific battery pack is not possible, the battery cells of a specific battery pack can be equalized in non-platform areas.

[0010] The processor can perform the following processing: control the voltage of the power supplied to the battery pack to not exceed the sum of the allowable voltages of the battery cells during charging.

[0011] According to this structure, even if there are battery cells that become fully charged and discharge during the equalization process, the voltage of the power supplied to the battery pack can be kept below the sum of the allowable voltages of the charging battery cells other than the discharging battery cells.

[0012] Invention Effects

[0013] According to the present invention, a battery system can be provided that can perform equalization with high precision and without time constraints in a manner that minimizes power waste, even when at least one of the state of charge (SOC) of the battery cells included in the battery pack is in a plateau region. Attached Figure Description

[0014] Figure 1 This is a schematic diagram showing the structure of the electrical system according to an embodiment of the present invention.

[0015] Figure 2 This is a schematic diagram showing the structure of the battery module in this embodiment.

[0016] Figure 3 This is a diagram illustrating an example of a battery according to an embodiment of the present invention.

[0017] Figure 4 This is a flowchart illustrating the process of equalization control in this implementation.

[0018] Figure 5 This is a graph showing the SOC-OCV curve of a single cell in this embodiment. Detailed Implementation

[0019] Hereinafter, embodiments and variations according to the present invention will be described with reference to the accompanying drawings. In the following description, the same reference numerals are used to denote the same parts and components. Their names and functions are also the same. Therefore, detailed descriptions of these will not be repeated. Furthermore, the embodiments and variations described below can be selectively combined as appropriate.

[0020] Figure 1 This is a schematic diagram showing the structure of the electrical system 1 according to an embodiment of the present invention. (See reference) Figure 1 Thick solid lines represent high-voltage power lines, thin solid lines represent low-voltage (12V) power lines, and thin dashed lines represent digital or analog signal lines. Electrical System 1 is a system that utilizes the high-voltage battery and peripheral equipment mounted in the vehicle as a stationary battery. Electrical System 1 includes: a generator 22; a power conditioner (hereinafter referred to as "Power Conditioning System: PCS") 23; a switchboard 30; electrical loads 33; an uninterruptible power supply (hereinafter referred to as "Uninterruptible Power Supply: UPS") 34; a step-down transformer 35; a 12V battery 36; battery modules 10AA to 10CD; relays 11AA to 11CD, 12A to 12C, 31, 32; an energy management system (hereinafter referred to as "Energy Management System: EMS") 100; an interface (IF) - electronic control unit (ECU) 200; and a BEV-ECU 300. The BEV-ECU300 is the ECU for the flow control of battery electric vehicles (BEVs).

[0021] The power generation device 22 is, for example, a solar power generation device, a wind power generation device, an emergency self-generating device, a fuel cell, or a combined heat and power (CHP) system, which is capable of generating electricity and can be installed at the demand side. A CHP system is a system that uses a diesel engine, gas engine, gas turbine, or fuel cell to generate electricity and uses the exhaust heat to supply hot water or heating / cooling systems. The power generation device 22 outputs the generated DC power to the PCS 23.

[0022] Power system 21 is a system that integrates power generation equipment, transformer equipment, transmission equipment, and distribution equipment for supplying electricity to demanders. Power system 21 supplies AC power to PCS23.

[0023] Battery modules 10AA to 10CD (hereinafter, representatively also referred to as "battery module 10") are modules capable of charging and discharging electricity, as described later. Figure 2 As explained in the description. In this embodiment, the battery modules 10AA to 10CD use a high-voltage battery mounted in an electric vehicle.

[0024] Relays 11AA to 11CD, 12A to 12C, 31, and 32 switch the circuit between on (connected) and off (disconnected) states based on control signals from a control device. Hereinafter, relays 11AA to 11CD are typically also referred to as "relay 11". Hereinafter, relays 12A to 12C are typically also referred to as "relay 12".

[0025] The distribution panel 30 charges the battery modules 10AA to 10CD via relays 12A to 12C and 11AA to 11CD using DC power received from the PCS23. Additionally, the distribution panel 30 supplies DC power discharged from the battery modules 10AA to 10CD to the PCS23.

[0026] PCS23 converts the DC power supplied from battery modules 10AA to 10CD via distribution panel 30 into AC power of a specified voltage. The converted AC power, along with AC power from power system 21, is then supplied via relays 31 and 32 to electrical loads 33 and UPS 34, and other electrical equipment located on the demand side. PCS23 also converts AC power from power system 21 into DC power of a specified voltage and DC power from generator 22 into DC power of a specified voltage, supplying the converted DC power to battery modules 10AA to 10CD via distribution panel 30.

[0027] Electrical load 33 includes, for example, electrical equipment that consumes electricity and such as air conditioning and lighting equipment installed on the demand side.

[0028] UPS34 is a device that continues to supply power even when power is interrupted due to power outages or other reasons. UPS34 converts and stores the AC power supplied from the distribution panel 30. When the power supply from the power system 21 supplied by the distribution panel 30 is interrupted, it converts the stored DC power back to AC power and supplies it to other electrical equipment via the distribution panel 30. Furthermore, UPS34 outputs the stored DC power to the step-down transformer 35.

[0029] EMS100, also known as xEMS, is a system for the demand side to properly monitor and manage energy usage. EMS100 includes Home EMS (HEMS), Building EMS (BEMS), and Factory EMS (FEMS). EMS100 is equipped with a processor and memory.

[0030] The IF-ECU200 is a device that controls communication between ECUs and with external devices, and it has a processor and memory.

[0031] The BEV-ECU 300 is a device that controls the drive system and battery module 10 of an electric vehicle. It includes a central processing unit (CPU) 301 as a processor and a memory 302. The memory 302 includes, for example, read-only memory (ROM) and random access memory (RAM). The BEV-ECU 300 is commonly used in electric vehicles. Furthermore, in... Figure 1 In the diagram, the dashed line representing the flow of control signals from the BEV-ECU300 is only connected to battery modules 10AA to 10AD, but in reality, it is also connected to other devices such as battery modules 10BA to 10CD and relays 11 and 12.

[0032] The step-down transformer 35 reduces the voltage of the DC power supplied from the UPS 34 to 12V to charge the 12V battery 36. The 12V battery 36 stores the 12V DC power from the step-down transformer 35 and outputs the stored 12V DC power as 12V to the operating electrical equipment (e.g., IF-ECU 200, BEV-ECU 300, the internal control device of the battery module 10 described later, namely BEVECU 110, battery ECUs 121A to 121C, MGECUs 131A to 131C).

[0033] Figure 2 This is a schematic diagram showing the structure of the battery module 10 according to this embodiment. (See reference) Figure 2 Two thick solid lines represent high-voltage DC power lines, and thin dashed lines represent signal lines for digital or analog signals. The battery module 10 includes a battery pack 120A to 120C (hereinafter, representatively also referred to as "battery pack 120"), a power control unit (PCU) 130A to 130C, a terminal block 140, a sub-relay 150, and a BEVECU 110.

[0034] Battery packs 120A to 120C each include battery ECUs 121A to 121C (hereinafter, representatively also referred to as "battery ECU 121"), batteries 122A to 122C (hereinafter, representatively also referred to as "battery 122"), and system main relays (SMRs) 123A to 123C (hereinafter, representatively also referred to as "SMR 123"). In this embodiment, battery packs 120A to 120C utilize high-voltage batteries mounted in electric vehicles. Therefore, since battery packs 120A to 120C are used in electric vehicles, the degradation degree of battery packs 120A to 120C is prone to differ. As a result, even when battery packs 120A to 120C are used similarly, differences in the way the state of charge (SOC) of battery packs 120A to 120C changes are likely to occur, and deviations in SOC are likely to occur.

[0035] Batteries 122A to 122C include battery packs consisting of multiple battery cells connected in series and sensor types. The sensor types include voltage sensors for detecting the voltage of each battery cell, current sensors for detecting the current flowing through the battery pack, and temperature sensors for detecting the temperature of various parts of the battery pack. Alternatively, batteries 122A to 122C may also include single cells consisting of a single battery cell instead of battery packs.

[0036] SMR123A to 123C, based on control signals from battery ECU121A to 121C, set the circuit for power exchange between batteries 122A to 122C and external devices to either a connected or disconnected state.

[0037] Battery ECUs 121A to 121C each have a processor and a memory, controlling the overall battery packs 120A to 120C. Battery ECUs 121A to 121C perform the following processing: processing sensor-type detection signals from batteries 122A to 122C; controlling the charging and discharging of batteries 122A to 122C by controlling SMRs 123A to 123C; and calculating the charge level or SOC of batteries 122A to 122C using known methods.

[0038] PCUs 130A to 130C each include MGECUs 131A to 131C, converters 132A to 132C, and inverters 133A to 133C. In this embodiment, PCUs 130A to 130C are PCUs used for traction and regeneration of the motor generator (MG) mounted on the electric vehicle and controlling the electric vehicle.

[0039] Converters 132A to 132C respectively convert the voltage of batteries 122A to 122C in battery packs 120A to 120C between the voltage of electrical equipment connected to the distribution panel 30.

[0040] When inverters 133A to 133C are installed in electric vehicles, they perform power conversion between DC power from converters 132A to 132C and AC power from the outside, but in this electrical system 1, power conversion is not performed.

[0041] Each of the MGECUs 131A to 131C has a processor and a memory. The MGECUs 131A to 131C control converters 132A to 132C to convert DC power from battery packs 120A to 120C into DC power of a specified voltage and output it to terminal block 140, or to convert DC power from terminal block 140 into DC power of the voltage of battery packs 120A to 120C and output it to battery packs 120A to 120C.

[0042] Terminal block 140 has terminals for connecting PCU130A to 130C and sub-relay 150, and electrically connecting PCU130A to 130C and sub-relay 150.

[0043] The sub-relay 150 sets the circuit for exchanging power between the terminal block 140 of the battery module 10 and external electrical equipment to a connected state or a disconnected state, based on the control signal from the BEVECU 110.

[0044] The BEVECU110 has a processor and memory, and controls the entire battery module 10 according to instructions from an external ECU. The BEVECU110 controls the power exchange between the battery packs 120A to 120C and external electrical devices via the PCUs 130A to 130C.

[0045] Figure 3 This is a diagram illustrating an example of the battery 122 in this embodiment. (See reference) Figure 3 The battery 122 includes a battery 124, an equalization unit (equalization circuit) 126, and a monitoring unit 127. The battery ECU 121 includes a CPU 1211 and a memory 1212. The battery ECU 121 controls the battery 122 based on signals received from the monitoring unit 127, signals from various sensors, mappings and programs stored in the memory 1212, and other information.

[0046] Battery 124 is a rechargeable DC power source (secondary battery), and is a battery pack composed of multiple (n) individual cells (battery units) 125A to 125N stacked together, for example, a battery pack composed of cells connected in series. The individual cells 125A to 125N can be, for example, lithium-ion batteries. In this embodiment, LFP batteries using lithium iron phosphate as the positive electrode active material are used as the individual cells 125A to 125N.

[0047] The monitoring unit 127 includes a voltage detection unit 128, a current sensor, and a temperature sensor. The voltage detection unit 128 detects the voltage VB (voltage between the terminals of each individual battery 125A to 125N) of the individual cells 125A to 125N. The current sensor detects the input / output current IB to the battery 124 (individual cells 125A to 125N). The temperature sensor detects the temperature TB of each individual battery 125A to 125N. Each detection unit outputs the detection result to the battery ECU 121.

[0048] The equalization unit 126 is assembled as an equalization circuit into the voltage detection unit 128 of the monitoring unit 127. In the battery 124, multiple (n) individual cells 125A to 125N (representatively also called "single cell 125") are connected in series. The voltage detection unit 128 detects the voltage of the individual cells 125A to 125N via multiple voltage detection lines L1, branch lines L11, and branch lines L12. The first voltage detection line L1 is connected to the positive terminal of the individual cell 125A. Furthermore, the second to (n+1)th voltage detection lines L1 are connected between adjacent individual cells 125A to 125N, to the negative terminal of one individual cell and the positive terminal of another individual cell.

[0049] A fuse F and a ferrite bead Cb are installed on the voltage detection line L1. The fuse F blows when an overcurrent occurs, protecting the circuit. The ferrite bead Cb reduces the stress applied when a surge voltage is applied instantaneously.

[0050] A Zener diode D is connected in parallel with each of the individual cells 125A to 125N via an adjacent voltage detection line L1. The cathode of the Zener diode D is connected to the positive terminal of the corresponding individual cell, and the anode is connected to the negative terminal of the corresponding individual cell. If an overvoltage is applied to the voltage detection unit 128 from the cell 124 (single cell 125), current flows through the Zener diode D, protecting the voltage detection unit 128 from damage by the overvoltage.

[0051] The voltage detection line L1 branches into branch line L11 and branch line L12 on the monitoring unit 127 side of the Zener diode D. Branch line L11 is connected to comparator 129 via switch So, and branch line L12 is connected to comparator 129 via switch Sh. Switches So and Sh can be, for example, metal-oxide-semiconductor (MOS) relays. Furthermore, branch line L11, which branches from the voltage detection line L1 connected to the positive terminal of the single cell 125A located on the positive output terminal side of battery 124, is not connected to comparator 129. And the voltage detection line L1, which connects to the negative terminal of the single cell 125N located on the negative output terminal side of battery 124, does not have branch line L12.

[0052] A resistor R1 is installed on branch line L12. A capacitor (flying capacitor) C is installed between branch line L12, which connects to the positive terminal of each individual cell, and branch line L11, which connects to the negative terminal. In branch line L12, capacitor C is connected between resistor R1 and switch Sh, forming an RC low-pass filter. Capacitor C is connected in parallel with the corresponding individual cells 125A to 125N, respectively. The charge of the corresponding individual cells 125A to 125N is charged into capacitor C, and the voltage value of capacitor C is equal to the voltage value of the corresponding individual cells 125A to 125N.

[0053] By turning on (closing) the switches Sh and So corresponding to specific individual cells 125A to 125N, comparator 129 outputs the voltage (cell voltage) VB of the specific individual cells 125A to 125N. Therefore, by sequentially turning on the switches Sh and So corresponding to each individual cell 125A to 125N, monitoring unit 127 can use voltage detection unit 128 to detect the voltage VB of each individual cell 125A to 125N. Furthermore, by turning on (closing) the switch Sh for individual cell 125A and the switch So connected to the negative terminal of individual cell 125N, the voltage Vb of battery 124 can be detected.

[0054] The equalization unit 126 consists of a discharge resistor Rd disposed on branch line L11 and a switch S1 that switches between on (closed) and off (open) states between adjacent branch lines L11. Switch S1 switches between ON (closed) and OFF (open) states by receiving a control signal from the battery ECU 121. Figure 3In the diagram, the dashed arrow indicates the current flow during equalization control to eliminate the uneven SOC of individual cells 125. It shows the case where the SOC of individual cell 125B is high, and discharge from individual cell 125B is performed, thus equalization control is executed. When the SOC of individual cell 125B is high, the switch S1 corresponding to individual cell 125B is turned on (closed). If switch S1 corresponding to individual cell 125B is turned on (closed), as shown by the dashed arrow, the current discharging from individual cell 125B is consumed by the two discharge resistors Rd, the SOC of individual cell 125B decreases, and SOC equalization is performed. In this way, equalization is performed among the individual cells 125 of battery 124 (the battery pack).

[0055] Previously, there was a technique that utilized two points of variation in the platform region of the LFP battery to perform SOC equalization of the battery cells (i.e., single cells 125) of the battery pack (i.e., battery 124) using LFP batteries as battery cells.

[0056] However, in the plateau region, the change in cell voltage in response to changes in SOC is small, so equalizing SOC in the plateau region is not easy.

[0057] Therefore, in the battery module 10 formed by multiple battery packs 120 connected in parallel, a specific battery pack 120X among the multiple battery packs 120 includes: a battery 124, which is formed by multiple single cells 125 connected in series with plateau regions and non-plateau regions on the charge-discharge curve; and an equalization unit 126, which equalizes the SOC of each single cell 125. The battery module includes: a PCU 130, a circuit for exchanging power between the battery packs 120; and processors (battery ECU 121, MGECU 131, BEVECU 110, BEV-ECU 300) that control the PCU 130 and the equalization unit 126. The processor performs the following processing: at a predetermined equalization time for a specific battery pack 120X, it controls the PCU 130 to enable power exchange with other battery packs 120, thereby making the charge level of each individual cell 125 of the specific battery pack 120X a non-platform region; and after each individual cell 125 of the specific battery pack 120X becomes a non-platform region, it controls the equalization unit 126 to equalize the SOC of each individual cell 125.

[0058] Thus, by exchanging power with other battery packs 120 in a manner where the individual cells 125 of the battery 124 of a specific battery pack 120X containing the equalization object are in a non-platform region of charge, equalization is performed in the non-platform region. As a result, even when at least one SOC of the individual cells 125 contained in the battery 124 is in a plateau region, equalization can be performed with high precision and without time constraints in a manner that minimizes power waste.

[0059] Figure 4 This is a flowchart illustrating the equalization control process in this embodiment. (See reference) Figure 4 The equalization control process is invoked and executed by the CPU301 of the BEV-ECU300 from the host computer at regular intervals.

[0060] The CPU 301 of the BEV-ECU 300 determines whether there is a battery pack 120 in any battery module 10 whose equalization flag value is "0" (step S111). The equalization flag is a flag related to the equalization of the battery pack 120. When the equalization flag value is "0", it means that equalization has not been performed in the battery pack 120. When the equalization flag value is "1", it means that power is being supplied to the battery pack 120 from outside, such as other battery packs 120, but equalization has not yet been performed. When the equalization flag value is "0", it means that power is being supplied to the battery pack 120 from outside, such as other battery packs 120, and equalization has been performed.

[0061] If a battery pack 120 is determined to have an equalization flag value of "0" ("Yes" in step S111), the CPU 301 determines whether there is a battery pack 120 among those with an equalization flag value of "0" where the equalization conditions are met (step S112). The equalization conditions for a battery pack 120 being met can be, for example, the following: The number of days elapsed since the last equalization operation of the battery pack 120 is a predetermined number of days (e.g., 3 days) or more. The cumulative value of the charging or discharging power of the battery pack 120 is a predetermined value or more. The maximum SOC difference between the individual cells 125 contained in the battery 122 of the battery pack 120 is a predetermined value or more. The dispersion or standard deviation of the individual cells 125 contained in the battery 122 of the battery pack 120 is a predetermined value or more.

[0062] If it is determined that there is a battery pack 120 where the equalization condition is met ("Yes" in step S112), the CPU 301 begins to draw power from external sources such as other battery packs 120 to transfer the SOC of the battery pack 120 that meets the equalization condition to the equalization area (step S113). The source of the power draw can be other battery packs 120 within the same battery module 10, other battery modules 10 connected to the same distribution panel 30, or the power system 21 or the power generation device 22.

[0063] For example, when drawing power from another battery pack 120 within the same battery module 10, the CPU 301 of the BEV-ECU 300 operates as follows: The CPU 301 sends instructions via the BEVECU 110 of the battery module 10 to the MGECU 131 of the PCU 130 of the battery pack 120 to control the converter 132 and inverter 133, in order to receive power from the source to the battery pack 120. The CPU 301 sends instructions to the MGECU 131 of the PCU 130 of the battery pack 120 to control the converter 132 and inverter 133, in order to supply power from the battery pack 120 to the destination.

[0064] Furthermore, when drawing power from other battery modules 10, the CPU 301 of the BEV-ECU 300 operates as follows: The CPU 301 controls the relays 11 and 12 of the power drawing path to switch to the connected state. The CPU 301 sends instructions to the MGECU 131 of the PCU 130 of the battery pack 120 via the BEVECU 110 of the battery module 10 to control the converter 132 and inverter 133, so as to receive power supply to the battery pack 120 from the drawing source. The CPU 301 sends control instructions to the BEVECU 110 of the battery module 10 to switch the sub-relay 150 of the battery module 10 to the connected state. The CPU 301 sends control instructions to the BEVECU 110 of the battery module 10 of the drawing source to switch the sub-relay 150 of the battery module 10 to the connected state. CPU301 sends instructions to control converter 132 and inverter 133 via BEVECU110 of battery module 10 to MGECU131 of PCU130 of battery pack 120 of battery module 10, so as to supply power from battery pack 120 to the destination.

[0065] Furthermore, the CPU301 of the BEV-ECU controls the converter 132 and inverter 133 of the source or destination of the power supply to ensure that the voltage of the power supplied to the battery 124 does not exceed the sum of the allowable voltages of the individual cells 125 during the charging of the battery 124.

[0066] After step S113, CPU301 sets the equalization flag of the battery pack 120 that has started to accept power transfer to "1" (step S114).

[0067] If it is determined that there is no battery pack 120 with an equalization flag value of "0" ("No" in step S111), or if it is determined that there is no battery pack 120 for which the equalization condition is met ("No" in step S112), or after step S114, the CPU 301 determines whether there is a battery pack 120 with an equalization flag value of "1" (step S121). If it is determined that there is a battery pack 120 with an equalization flag value of "1" ("Yes" in step S121), the CPU 301 determines whether the equalization start condition of the battery pack 120 is met (step S122).

[0068] Figure 5 This is a graph showing the SOC-OCV curve of a single cell 125 according to this embodiment. (Reference) Figure 5 The vertical axis of this graph represents OCV (unit: V), and the horizontal axis represents SOC (unit: %). The solid line graph represents the SOC-OCV curve of a single cell 125 of the LFP battery used in this embodiment. The dashed line graph represents the SOC-OCV curve of a single cell of a ternary lithium battery, which has been used historically. The SOC-OCV curve of the LFP battery includes three parts. Part 1 is the section where OCV increases sharply as SOC increases from 0% to a%. Part 2 is the section where OCV increases slowly as SOC increases from a% to f% (referred to as the "plateau region"). Part 3 is the section where OCV increases sharply as SOC increases from f% to 100%. Because the increase or decrease in OCV accompanying the change in SOC is large in Parts 1 and 3, it is easy to use this as an opportunity to equalize the SOC of the multiple single cells 125 included in battery 124.

[0069] return Figure 4 The equalization start condition for the battery pack 120 in step S122 is met, for example, as follows: The SOC of any one or a specified number of individual cells 125 in the battery pack 120 reaches f%. The average SOC of the individual cells 125 in the battery pack 120 reaches f%. The SOC of all individual cells 125 in the battery pack 120 reaches f%.

[0070] If the equalization start condition for the battery pack 120 is determined to be met ("Yes" in step S122), the CPU 301 sends an instruction to the battery ECU 121 to start equalization control within the battery pack 120 to be equalized (step S123). Based on the instruction from the BEV-ECU 300, the battery ECU 121 maintains the specified SOC by sequentially interrupting the switching S1 of the equalization unit 126 corresponding to each individual battery 125 whose SOC reaches f% or higher (e.g., 100%). This equalizes the SOC of all individual batteries 125 to the specified percentage. However, the method for equalization control of the battery pack 120 is not limited to the above method and can be other methods. After step S123, the CPU 301 sets the equalization flag of the battery pack 120 to "2" (step S124).

[0071] If it is determined that there is no battery pack 120 with an equalization flag value of "1" ("No" in step S121), if it is determined that there is no battery pack 120 with an equalization start condition ("No" in step S122), or after step S124, the CPU 301 determines whether there is a battery pack 120 with an equalization flag value of "2" (step S131). If it is determined that there is a battery pack 120 with an equalization flag value of "2" ("Yes" in step S131), the CPU 301 determines whether the equalization end condition of the battery pack 120 is met (step S132). The equalization end condition being met can be, for example, the following: The SOC of all individual cells 125 contained in the battery pack 120 becomes a specified percentage (e.g., 100%). The dispersion or standard deviation of the SOC of all individual cells 125 contained in the battery pack 120 is less than a specified value.

[0072] If the equalization termination condition of the battery pack 120 is determined to be met ("Yes" in step S132), the CPU 301 sends a command to the battery ECU 121 to terminate the equalization control (step S133). The CPU 301 sends a command to the control unit of the power transfer source and the power transfer destination to terminate the power transfer (step S134). The CPU 301 sets the equalization flag of the battery pack 120 to "0" (step S135).

[0073] If it is determined that there is no battery pack 120 with the equalization flag set to "2" ("No" in step S131), or if it is determined that there is no battery pack 120 with the equalization termination condition met ("No" in step S132), or after step S135, the CPU 301 returns the executed process to the upper-level processing of the calling source of the equalization control process.

[0074] [Variation Example]

[0075] (1) In the foregoing embodiments, such as Figure 3 As shown, all batteries 122 in the battery pack 120 included in the battery module 10 are LFP batteries. However, this is not a limitation; some or all of the batteries 122 in the battery pack 120 may be batteries different from LFP batteries, such as ternary lithium batteries. See again... Figure 5 Unlike LFP batteries, ternary lithium batteries do not exhibit the aforementioned plateau region in their SOC-OCV curves. Therefore, regarding the 125 single-cell ternary lithium battery... Figure 4 The equalization termination condition specified in step S132 is not limited to the range of SOC in Part 3, and can be any SOC.

[0076] (2) In the foregoing embodiments, there is no particular limitation on the time period for performing equalization control. However, it is not limited to this; the time period for performing equalization control may also be a period of time when the power input / output of electrical system 1 is low. In this way, the impact on availability can be minimized.

[0077] (3) In the foregoing embodiments, such as Figure 4 As shown, the equalization control processing is performed by the CPU 301 of the BEV-ECU 300. However, it is not limited to this; the equalization control processing can also be performed by other control units (e.g., battery ECU 121, MGECU 131, BEVECU 110). Multiple control units can also cooperate to perform the equalization control processing.

[0078] (4) The foregoing implementation method can be understood as Figure 1 The invention relates to the control device for the electrical system 1 shown, or the electrical system 1 such as the BEV-ECU 300. Furthermore, the control device of the electrical system 1 can perform... Figure 4 The invention of the control method or control program shown.

[0079] [Summarize]

[0080] (1) such as Figure 1 and Figure 2 As shown, the electrical system 1, which is the battery system, is a system consisting of multiple battery packs 120 connected in parallel, capable of charging and discharging. For example... Figure 2 , Figure 3 and Figure 5 As shown, a specific battery pack 120X among the multiple battery packs 120 includes: a battery 124, which is a group of batteries consisting of multiple battery cells, i.e., single cells 125, connected in series on a charge-discharge curve having plateau regions and non-plateau regions; and an equalization unit 126, which equalizes the SOC of each single cell 125. Figures 1 to 3As shown, the electrical system 1 includes: a PCU 130, a circuit for exchanging power between battery packs 120; and a BEV-ECU 300, a processor for controlling the PCU 130 and the equalization unit 126. Figure 4 As shown, the BEV-ECU300 performs the following processing: at a predetermined equalization time for a specific battery pack 120X, the PCU130 is controlled to enable power exchange with other battery packs 120, thereby making the charge level of each individual cell 125 of the specific battery pack 120X reach the non-platform region (e.g., step S113). After each individual cell 125 of the specific battery pack 120X reaches the non-platform region, the equalization unit 126 is controlled to equalize the SOC of each individual cell 125 (e.g., step S123).

[0081] Thus, by exchanging power with other battery packs 120 in a manner where the individual cells 125 of the battery 124 of a specific battery pack 120X containing the equalization object are in a non-platform region of charge, equalization is performed in the non-platform region. As a result, even when at least one SOC of the individual cells 125 contained in the battery 124 is in a plateau region, equalization can be performed with high precision and without time constraints in a manner that minimizes power waste.

[0082] (2) such as Figure 4 As shown in step S113, when the BEV-ECU300 is unable to exchange power for a specific battery pack 120X with other battery packs 120, it can use external power (e.g., power system 21, generator 22) to make the individual battery 125 of the specific battery pack 120X a charge in the non-platform area.

[0083] Therefore, even when it is not possible to exchange power of a specific battery pack 120X with other battery packs 120, it is possible to equalize the power of individual cells 125 of a specific battery pack 120X in non-platform areas.

[0084] (3) such as Figure 4 As shown in step S113, the BEV-ECU300 can control the voltage of the power supplied to the battery 124 so as not to exceed the total allowable voltage of the single battery 125 during charging.

[0085] Therefore, even if a single cell 125 is fully charged and discharged midway through the equalization process, the voltage of the power supplied to the battery 124 can be kept within the total allowable voltage of the single cells 125 that are charging, excluding the single cells 125 that are discharging.

[0086] It should be considered that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention is not shown in the description of the above embodiments, but is indicated by the technical solutions, and is intended to include all modifications within the meaning and scope equivalent to the technical solutions.

[0087] Symbol Explanation

[0088] 1-Electrical system; 10, 10AA~10CD-Battery modules; 11, 11AA~11CD; 12, 12A~12C; 31, 32-Relays; 21-Power system; 22-Generator; 23-PCS; 30-Distribution panel; 33-Electrical load; 34-UPS; 35-Step-down transformer; 36-12V battery; 100-EMS; 110-BEVECU; 120, 120A~120C-Battery pack; 120X-Specific battery pack; 121, 121A~121C-Battery ECU; 122, 122A~122C-Battery; 123, 123A~123C-SMR; 124-Battery; 125, 125A~125N-Single battery; 1 26 - Equalization unit, 127 - Monitoring unit, 128 - Voltage detection unit, 129 - Comparator, 130, 130A~130C - PCU, 131, 131A~131C - MGECU, 132, 132A~132C - Converter, 133, 133A~133C - Inverter, 140 - Terminal block, 150 - Sub-relay, 200 - IF-ECU, 300 - BEV-ECU, 301, 1211 - CPU, 302, 1212 - Memory, C - Capacitor, Cb - Chip bead, D - Zener diode, F - Fuse, L1 - Voltage detection line, L11, L12 - Branch lines, R1 - Resistor, Rd - Discharge resistor, S1, Sh, So - Switch.

Claims

1. A battery system comprising multiple battery packs capable of charging and discharging electricity connected in parallel, characterized in that, Specific battery packs among multiple battery packs include: A battery pack is composed of multiple battery cells connected in series, each having a plateau region and a non-plateau region on its charge-discharge curve; and An equalization circuit equalizes the state of charge (SOC) of each battery cell. The battery system includes: A fusion circuit that facilitates the exchange of power between the battery packs; and The processor controls the fusion circuit and the equalization circuit. The processor performs the following processing: At a predetermined equalization time for the specific battery pack, the fusion circuit is controlled to enable power exchange with other battery packs, so that the battery cells of the specific battery pack become the charging amount in the non-platform region. and After each battery cell in the specific battery pack becomes a non-platform region, the equalization circuit is controlled to equalize the SOC of each battery cell.

2. The battery system according to claim 1, characterized in that, The processor performs the following processing: when it is not possible to exchange power between other battery packs and the specific battery pack, it uses external power to make the battery cells of the specific battery pack charge the non-platform area.

3. The battery system according to claim 1 or 2, characterized in that, The processor performs the following processing: controlling the voltage of the power supplied to the battery pack to not exceed the total allowable voltage of the battery cells during charging.

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