State of charge estimation device, state of charge estimation system and state of charge estimation program

Abstract

A state-of-charge estimation device (50) comprises: a storage unit (51) that stores the charging and discharging history of a storage battery (31); a charge and discharge determination unit (52) that determines, based on the charging and discharging history stored in the storage unit, whether the storage battery is in a charged or discharged state; a charge and discharge control unit (53) that discharges the storage battery by a predetermined amount when the charge and discharge determination unit determines that the storage battery is in a charged state, and charges the storage battery by a predetermined amount when the charge and discharge determination unit determines that the storage battery is in a discharged state; an open-circuit voltage reference unit (54) that obtains the open-circuit voltage of the storage battery after the charge and discharge control unit has charged or discharged the storage battery;and a state-of-charge estimation unit (55) which refers to a charging and discharging curve which specifies the relationship between the open-circuit voltage of the storage battery and the state of charge of the storage battery, in order to estimate the state of charge of the storage battery from the open-circuit voltage referenced by the open-circuit voltage reference unit.

Description

[Cross-reference to related applications]

[0001] This application is based on Japanese patent application No. 2023-074306, filed on April 28, 2023, the description of which is hereby incorporated by reference. [Technical field]

[0002] The present disclosure relates to a state-of-charge estimation device for estimating the state of charge of a storage battery, a state-of-charge estimation system and a state-of-charge estimation program. [State of the art]

[0003] Conventional methods are known for estimating the state of charge (SOC) of a storage battery based on its open-circuit voltage (OCV). These methods include one based on the difference between the charging curve (i.e., the OCV-SOC curve observed during charging) and the discharging curve (i.e., the OCV-SOC curve observed during discharging), which is the hysteresis characteristic of the storage battery. For example, a technique is provided to estimate the SOC from the OCV based on the charging curve after each charge. Such a technique may be described, for example, in patent specification 1. [Citation list][Patent specification]

[0004] PTL 1: JP 2020-38146 A SUMMARY OF THE INVENTION

[0005] These methods revealed an error in the OCV (Open Circuit Value) between high and low C (capacity) rates during charging and discharging. This trend is particularly pronounced in LFP (Lithium Iron Phosphate) batteries. Estimating the SOC (State of Charge) based on OCV values ​​containing this error can lead to reduced accuracy.

[0006] Storage batteries used in electric vehicles require high performance characteristics (high-current charging and discharging). For example, fast charging with a fast charger requires a higher C-rate than standard charging with typical chargers installed in homes and similar environments. This means that such a storage battery is likely to experience a larger open-circuit voltage (OCV) error caused by the different C-rates. Consequently, a larger state-of-charge (SOC) error is also likely, so fast charging may not complete properly if controlled based on the SOC.

[0007] The present disclosure was made in consideration of these circumstances. A main objective of the disclosure is to provide a state-of-charge estimation device, a state-of-charge estimation system, and a state-of-charge estimation program that can achieve higher accuracy in determining the state of charge of a storage battery.

[0008] A first means of solving the aforementioned problem is a state-of-charge estimator that estimates the state of charge of a storage battery. The state-of-charge estimator comprises: a storage unit that stores a charge and discharge history of the storage battery; a charge and discharge determination unit that, based on the charge and discharge history stored in the storage unit, determines whether the storage battery is in a charged or discharged state; a charge and discharge control unit that discharges the storage battery by a predetermined amount when the charge and discharge determination unit determines that the storage battery is in a charged state, and charges the storage battery by a predetermined amount when the charge and discharge determination unit determines that the storage battery is in a discharged state.an open-circuit voltage reference unit that references the open-circuit voltage of the storage battery after the charge and discharge control unit has charged or discharged the storage battery; and a state-of-charge estimation unit that refers to a charge and discharge curve that specifies a relationship between the open-circuit voltage of the storage battery and the state of charge of the storage battery in order to estimate the state of charge of the storage battery from the open-circuit voltage referenced by the open-circuit voltage reference unit.

[0009] This prevents errors in the open-circuit voltage caused by differences in the operating conditions of a storage battery, resulting in higher accuracy in determining the state of charge of the storage battery.

[0010] A second means of solving the aforementioned problem is a state-of-charge estimation system comprising a first storage battery and a second storage battery, which estimates the states of charge of the first and second storage batteries. The state-of-charge estimation system includes: a storage unit that stores the charge and discharge history of each of the storage batteries; a charge and discharge determination unit that, based on the charge and discharge history stored in the storage unit, determines whether each of the storage batteries is in a charged or discharged state; and a charge and discharge control unit that discharges the storage battery determined by the charge and discharge determination unit to be in a charged state and charges the storage battery determined by the charge and discharge determination unit to be in a discharged state.An open-circuit voltage reference unit, which references the open-circuit voltage of each of the storage batteries after the charge and discharge control unit has charged or discharged each of the storage batteries; and a state-of-charge estimation unit, which refers to a charge and discharge curve that specifies a relationship between the open-circuit voltage of the storage battery and the state of charge of the storage battery, in order to estimate the state of charge of each of the storage batteries from the open-circuit voltage of the corresponding storage battery as referenced by the open-circuit voltage reference unit. The charge and discharge control unit charges and discharges each of the storage batteries by facilitating an energy exchange between the first storage battery and the second storage battery.

[0011] This allows errors in the open-circuit voltage caused by differences in the operating conditions of a storage battery to be suppressed, resulting in higher accuracy in determining the state of charge of the storage battery.

[0012] A third means of solving the aforementioned problem is a state-of-charge estimation program that causes a state-of-charge estimation device to perform the following: a memory process to store the charge and discharge history of the storage battery; a charge and discharge determination process to determine whether the storage battery is being charged or discharged, based on the charge and discharge history stored by the memory process; a charge and discharge control process to discharge the storage battery when the charge and discharge determination process determines that the storage battery is being charged, and to charge the storage battery when the charge and discharge determination process determines that the storage battery is being discharged; an open-circuit voltage reference process to reference the open-circuit voltage of the storage battery after the charge and discharge control has charged or discharged the storage battery;and a state-of-charge estimation process for referencing a charge and discharge curve that specifies the relationship between the open-circuit voltage of the storage battery and the state of charge of the storage battery, in order to estimate the state of charge of the storage battery from the open-circuit voltage obtained through the open-circuit voltage sensing process.

[0013] This allows errors in the open-circuit voltage caused by differences in the operating conditions of a storage battery to be suppressed, resulting in higher accuracy in determining the state of charge of the storage battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The aforementioned and other objectives, features and advantages of the present disclosure will become clearer from the detailed description below with reference to the accompanying drawings, in which the following applies: Fig. Figure 1 is a configuration diagram of a power supply system according to a first embodiment; Fig. 2(a) is a representation showing errors in OCV after loading, and Fig. 2(b) is a representation showing errors in OCV after unloading. Fig. Figure 3 is a representation showing OCV-SOC curves. Fig. Figure 4 is a flowchart of a memory process. Fig. Figure 5 is a flowchart of a process for estimating SOC. Fig. Figure 6 is a time diagram showing the charging and discharging times. Fig. Figure 7 is a representation of an energy supply system according to a modification; Fig. Figure 8 is a representation of an energy supply system according to a modification; and Fig. Figure 9 is a flowchart of a processed memory process according to a modification. [Description of the implementation examples]

[0015] A first embodiment of a state-of-charge estimation device, a state-of-charge estimation system, and a state-of-charge estimation program according to the present disclosure will now be described with reference to the drawings. In the embodiments and modifications described below, identical or equivalent components in the drawings are designated with the same reference numerals, and the description of the components designated with the same reference numerals is included by reference. A power supply system 100, which serves as a state-of-charge estimation system according to the present embodiment, is installed in mobility systems that include electrified vehicles such as electric vehicles and hybrid vehicles, electric aircraft, and electric ships. The present embodiment assumes an installation in electrified vehicles.

[0016] As in Fig. As shown in Figure 1, the power supply system 100 comprises a motor 10, an inverter 20, and a battery pack 30. The motor 10 is a three-phase synchronous motor and includes star-connected U-, V-, and W-phase armature windings 11 and a rotor (not shown). The armature windings 11 of each phase are spaced 120 electrical degrees apart from the others. The motor 10 can, for example, be a permanent magnet synchronous motor. The rotor can transmit power to the vehicle's drive wheels. The motor 10 thus serves as a torque source for propelling the vehicle.

[0017] Inverter 20 comprises three-phase series-connected bodies, each having an upper switch SWH and a lower switch SWL. An upper arm diode DH, which is a freewheeling diode, is connected antiparallel to the upper switch SWH, while a lower arm diode DL, which is also a freewheeling diode, is connected antiparallel to the lower switch SWL. Hereinafter, the upper arm switch SWH and the lower arm switch SWL are sometimes referred to as switches SWH and SWL. In the present embodiment, each of the switches SWH and SWL is a semiconductor switching element, for example, an insulated-gate bipolar transistor (IGBT).

[0018] Inverter 20 includes a smoothing capacitor 21. The high-potential terminal of the smoothing capacitor 21 is connected to a positive busbar H1. The low-voltage terminal of the smoothing capacitor 21 is connected to a negative busbar L1. Note that the smoothing capacitor 21 can be installed outside of inverter 20.

[0019] In each phase, the connection point between the low-voltage terminal of the upper switch SWH or the emitter and the high-voltage terminal of the lower switch SWL or the collector is connected via a conductive element 23, for example a busbar, to a first end of the corresponding armature winding 11. The armature windings 11 in the respective phases have second ends that are connected to each other at a neutral point.

[0020] The collector of the upper switch SWH in each phase is connected to the positive busbar H1. The emitter of the lower switch SWL in each phase is connected to the negative busbar L1. The battery pack 30 is connected to the inverter 20 via the positive busbar H1 and the negative busbar L1.

[0021] The battery pack 30 of the power supply system 100 comprises a first storage battery 31 and a second storage battery 32. The storage batteries 31 and 32 each serve as a power source to drive the rotation of the rotor of the motor 10. Each of the storage batteries 31 and 32 is a composite battery configured as a series connection of individual battery cells. The positive terminal of the first storage battery 31 is connected to the positive busbar H1, and the negative terminal of the second storage battery 32 is connected to the negative busbar L1. The battery cells that make up an assembly have terminal voltages (e.g., nominal voltages) that are set to the same value. The battery cells can be, for example, secondary cells such as lithium-ion cells. The storage batteries 31 and 32 can have either the same or different terminal voltages (e.g., nominal voltages).

[0022] Each of the storage batteries 31 and 32 can be charged by an external battery charging device 40, which is installed outside the vehicle. The external battery charging device 40 can be, for example, a stationary battery charger. The external battery charging device 40 can be either a standard charger or a fast charger. The positive terminal of the external battery charging device 40 is connected to one end of a positive charging path 43, and the other end of the charging path 43 is connected to the positive bus H1. The negative terminal of the external battery charging device 40 is connected to one end of a negative charging path 44, and the other end of the charging path 44 is connected to the negative bus L1.

[0023] Battery pack 30 of power supply system 100 includes a positive main switch SMRH, which electrically connects or disconnects the positive busbar H1, which connects the first storage battery 31 and the inverter 20. The positive switch SMRH is installed on the positive busbar H1. Battery pack 30 of power supply system 100 also includes a negative switch SMRL, which electrically connects or disconnects the negative busbar L1, which connects the second storage battery 32 and the inverter 20. The positive charging path 43 in power supply system 100 includes a high-voltage charging switch DCRH, which electrically connects or disconnects the positive charging path 43. The negative charging path 44 in power supply system 100 includes a low-voltage charging switch DCRL, which electrically connects or disconnects the negative charging path 44.The positive main switch SMRH, the negative main switch SMRL, the high voltage charging switch DCRH and the low voltage charging switch DCRL are sometimes referred to as the switches SMRH, SMRL, DCRH and DCRL.

[0024] In the present embodiment, each of the switches SMRH, SMRL, DCRH, and DCRL is a mechanical relay. In the off state, each of the switches SMRH, SMRL, DCRH, and DCRL blocks current flow in both directions. In the on state, the switch allows current flow in both directions. Each of the switches SMRH, SMRL, DCRH, and DCRL can be not only a mechanical relay but also, for example, a semiconductor switching element.

[0025] The battery pack 30 of the power supply system 100 comprises a first switch SW1, a second switch SW2, a third switch SW3, and a fourth switch SW4 as switches for changing the connection states of the first storage battery 31 and the second storage battery 32. Hereinafter, the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4 are sometimes referred to as switches SW1 to SW4.

[0026] In the present embodiment, switches SW1 to SW4 are mechanical relays. In the off state, switches SW1 to SW4 block current flow in both directions. In the on state, the switches allow current flow in both directions. Switches SW1 to SW4 can be not only mechanical relays, but also, for example, semiconductor switching elements.

[0027] The first switch SW1 is installed in a first current path 24, which connects the negative terminal of the first storage battery 31 and the positive terminal of the second storage battery 32. When the first switch SW1 is open, the negative terminal of the first storage battery 31 and the positive terminal of the second storage battery 32 are electrically connected. Conversely, when the first switch SW1 is open, the negative terminal of the first storage battery 31 and the positive terminal of the second storage battery 32 are electrically disconnected.

[0028] The second switch SW2 is installed in a second current path 25, which connects the negative terminal of the first storage battery 31 and the negative busbar L1. When the second switch SW2 is open, the negative terminal of the first storage battery 31 and the negative busbar L1 are electrically connected. Conversely, when the second switch SW2 is open, the negative terminal of the first storage battery 31 and the negative busbar L1 are electrically disconnected.

[0029] The third switch SW3 and the fourth switch SW4 are installed in a third current path 26, which connects the portion of the first current path 24 from the first switch SW1 to the second storage battery 32 and the neutral point of the armature windings s 11. The third switch SW3 is installed closer to the second storage battery 32, while the fourth switch SW4 is installed closer to the neutral point. When the third switch SW3 and the fourth switch SW4 are open, the neutral point of the armature windings 11 and the positive terminal of the second storage battery 32 are electrically connected. Conversely, when either the third switch SW3 or the fourth switch SW4 is open, the neutral point of the armature windings 11 and the positive terminal of the second storage battery 32 are electrically disconnected.

[0030] The power supply system 100 includes a neutral point capacitor 22. The high-potential terminal of the neutral point capacitor 22 is connected to a neutral point (more precisely, a point on the third current path 26 between the third switch SW3 and the fourth switch SW4). The low-voltage terminal of the neutral point capacitor 22 is connected to the negative busbar L1.

[0031] The energy supply system 100 includes various sensors. As in Fig. As shown in Figure 1, a first current sensor A11 is installed on the current path between the positive main switch SMRH and the first storage battery 31 to measure the current flowing through it. This sensor can be installed at any point on the current path as long as it can measure the current flowing through the first storage battery 31.

[0032] Furthermore, a second current sensor A12 is installed on the first current path 24 between the first switch SW1 and the second storage battery 32 (more precisely, between the connection point with the third current path 26 and the positive terminal of the second storage battery 32) to measure the current flowing through the second storage battery 32. This sensor can be installed at any point along the current path as long as it can measure the current flowing through the second storage battery 32. Additionally, a first voltage sensor V11 is installed to measure the open-circuit voltage (OCV) of the first storage battery 31, and a second voltage sensor V12 is installed to measure the OCV of the second storage battery 32.

[0033] It should be noted that the inverter 20 may be contained within the battery pack 30. Some or all switches SMRH, SMRL, and SW1 to SW4 may be installed outside the battery pack 30.

[0034] The power supply system 100 includes a control device 50 as a state-of-charge estimation device. The control device 50 is essentially a microcomputer, and the microcomputer includes a CPU, RAM, ROM, and other components. The functions provided by the control device 50 can be provided by software recorded on a tangible storage device and a computer for executing the software, by software alone, by hardware alone, or by a combination of both. For example, if provided by an electronic circuit, which is hardware, the microcomputer can be an analog circuit or a digital circuit with a large number of logic circuits.The microcomputer executes programs stored in a non-volatile physical storage medium, such as memory within the microcomputer itself. Examples of these programs include those for the processing described later, which are stored in the... Fig. 3 and Fig. Figure 4 and other figures illustrate this. When a program is executed, the corresponding process (the processing) is implemented. The memory can be, for example, non-volatile memory. Programs stored in memory can be updated via a communication network such as an over-the-air (OTA) network or the internet.

[0035] The control device 50 receives information (acquisition values) from various sensors. These sensors include, for example, the first current sensor A11, the second current sensor A12, the first voltage sensor V11, and the second voltage sensor V12, which have been described above. Although not shown, other examples of the various sensors include a rotation angle sensor, which detects the rotation angle (electrical angle) of the rotor, and a phase current sensor, which detects the phase current flowing through the armature windings 11 in each phase.

[0036] The control device 50 executes various processes according to the programs based on information such as the measured values ​​received from the various sensors. Examples of the various processes to be executed include a process for controlling the inverter 20. In particular, the control device 50 controls switches such as the SWH and SWL switches contained in the inverter 20 to feed back the controlled variable of the motor 10, based on measured values ​​from each sensor, so that it corresponds to the setpoint. The controlled variable can be, for example, the torque. In each phase, the upper switch SWH and the lower switch SWL are alternately switched on. This feedback control transmits the rotational force of the rotor to the drive wheels and propels the vehicle.

[0037] To charge the first storage battery 31 and the second storage battery 32 when the external battery charger 40 is connected, the control device 50 controls the on / off state of each of the switches SMRH, SMRL, DCRH, DCRL, and SW1 to SW4, as well as the switches SWH and SWL contained in the inverter 20. For example, if the external battery charger 40 is a fast charger, the control device 50 connects the first storage battery 31 and the second storage battery 32 in series to enable fast charging. In some cases, the control device 50 connects the first storage battery 31 and the second storage battery 32 in parallel via the neutral point of the motor 10 to charge them.In these cases, the control device 50 can use the inverter 20 and the armature windings 11 of the motor 10 as a voltage converter (DC-DC converter) and increase (or decrease) the charging voltage from the external battery charging device 40 for charging.

[0038] The control device 50 also receives the OCV of each of the storage batteries 31 and 32 and estimates the state of charge (SOC) of each of the storage batteries 31 and 32 based on the OCV according to a state of charge estimation program.

[0039] The OCV and SOC of each of the storage batteries 31 and 32 can differ depending on the operating conditions of the storage batteries 31 and 32. More specifically, the torque required for the motor 10 can vary significantly depending on the vehicle's driving conditions. Furthermore, the storage batteries 31 and 32 can be charged with either a fast charger or a standard charger. Therefore, the storage batteries 31 and 32 used in the vehicle can be subject to large fluctuations in the charging or discharging rate, i.e., the C-rate (the ratio of the charging / discharging current to the battery capacity).

[0040] As in Fig. As shown in 2(a), our investigations have shown that the OCV can vary depending on the C-rate, even if the SOC represents the same value X% (e.g., 50%) immediately after charging. Fig. 2. The OCV at high C-rates is indicated by a solid line, while the OCV at low C-rates is indicated by a dashed line. Similarly, our investigations have shown that the OCV can vary depending on the C-rate, even if the SOC, immediately after discharge, represents the same value Y% (e.g., 50%) as in Fig. 2(b) is shown. It is obvious that the SOC cannot be accurately estimated based on OCV values, which contain an error.

[0041] In particular, it is known that the OCV-SOC curve (charge and discharge curve) for the storage batteries 31 and 32 has a plateau region in which the curve temporarily flattens out, as shown in Fig. Figure 3 illustrates this. If the SOC is estimated in such a plateau area, a small OCV error can lead to a significant SOC error.

[0042] As in Fig. As shown in Figure 3, the OCV-SOC curve C11, which represents a charging curve during the charging process, does not match the OCV-SOC curve C13, which represents a discharging curve during the discharging process. This means that the storage batteries 31 and 32 exhibit hysteresis characteristics. Therefore, the SOC must also be estimated based on the hysteresis characteristics of each of the storage batteries 31 and 32.

[0043] The following describes the various functions of the control device 50 and the various processes performed by the control device 50 to estimate the state of charge (SOC) of each of the storage batteries 31 and 32 from the operating voltage (OCV) of each of the storage batteries 31 and 32. The various functions related to estimating the state of charge are performed by the microcomputer of the control device 50, which executes the program (state of charge estimation program) stored, for example, in the memory of the control device 50.

[0044] As in Fig. As shown in Figure 1, examples of the various functions related to SOC estimation include functions as a storage unit 51, charge and discharge determination unit 52, charge and discharge control unit 53, open-circuit voltage reference unit 54, and state-of-charge estimation unit 55. The various functions are described in detail below.

[0045] First, the storage unit 51 is described. The storage unit 51 stores the charging and discharging history of the storage batteries 31 and 32. The charging and discharging history reflects the charging and discharging trends of the storage batteries 31 and 32. For example, over the period from the previous state of charge (SOC) estimate to the present time, the integrated current value, which is calculated by integrating the current flowing into or out of each of the storage batteries 31 and 32, can be stored as the corresponding charging and discharging history.

[0046] A method for storing the charging and discharging history in the present embodiment is now described with reference to Fig. As described in section 4, the control device 50, which serves as a storage unit 51, performs a storage operation at predetermined intervals. The storage operation is performed for each of the storage batteries 31 and 32. Although the storage operation for the first storage battery 31 is mainly described below, the same applies to the storage operation for the second storage battery 32.

[0047] When the storage process is started, the control device 50 determines how in Fig. Figure 4 shows whether the current value of the first storage battery 31 has remained continuously greater than or equal to a first threshold value Th1 during a predetermined time (step S11). The current value is represented as a positive value (+) when current flows into the first storage battery 31 (i.e., during charging), while the current value is represented as a negative value (-) when current flows out of the first storage battery 31 (i.e., during discharging). The predetermined time can be arbitrary; for example, it could be the storage process execution interval. The first threshold value Th1 is any positive value.

[0048] This means that in step S11, it is determined that the battery has been charged by at least the amount represented by the absolute value of the first threshold Th1 multiplied by the predetermined time. If the result of the determination is positive, the control device 50 increments (adds 1 to) a charge and discharge counter stored in the memory of the control device 50 (step S12). The storage process is then terminated.

[0049] If the result of the determination in step S11 is negative, the control device 50 determines whether the current value of the first storage battery 31 has remained continuously less than or equal to a second threshold value Th2 for a predetermined time (step S13). The second threshold value Th2 is any negative value. That is, in step S13, it is determined that the battery has been discharged by at least the amount represented by the absolute value of the second threshold value Th2 multiplied by the predetermined time. If the result of the determination is positive, the control device 50 decrements the charge and discharge counter (subtracts 1 from it) (step S14). The storage process is then terminated.

[0050] If, however, the result of the determination in step S13 is negative, i.e., it cannot be determined that either charging or discharging has occurred, the control device 50 decides to retain the value of the charge and discharge counter (step S15) and terminates the storage process.

[0051] The charge and discharge determination unit 52 uses the charge and discharge history obtained from the storage unit 51 to determine whether the storage batteries 31 and 32 are in a charged or discharged state. For example, the charge and discharge determination unit 52 can determine that the battery is in a charged state if the integrated current value is within the charge range, reflecting a tendency to recharge. The charge and discharge determination unit 52 can determine that the battery is in a discharged state if the integrated current value is within the discharge range, reflecting a tendency to recharge. The charge and discharge determination unit 52 can determine that the charge / discharge status is unknown if the integrated current value is outside both the charge and discharge ranges.

[0052] In the present embodiment, the charge and discharge determination unit 52 determines that the battery is in a charged state when the charge and discharge counter stored in the storage unit 51 indicates a first determination value J1 or higher, representing the charging range. Conversely, if the charge and discharge counter indicates a second determination value J2 or lower, representing the discharging range, the charge and discharge determination unit 52 determines that the battery is in a discharged state. If the charge and discharge counter indicates a value higher than the second determination value J2 and lower than the first determination value J1, the charge / discharge status is determined to be unknown.

[0053] When the charge and discharge determination unit 52 determines that the first storage battery 31 is in a charged state, the charge and discharge control unit 53 discharges the first storage battery 31. In this case, the control device 50 discharges the first storage battery 31 to reduce the SOC by a predetermined amount (e.g. 5.0%).

[0054] If, however, it is determined that the first storage battery 31 is in a discharged state, the charge and discharge control unit 53 charges the first storage battery 31. In this case, the control device 50 charges the first storage battery 31 to increase the state of charge (SOC) by a predetermined amount (e.g., 2.5%).

[0055] The charging and discharging rates can be different or the same, as in the present embodiment. The charging and discharging rate (C-rate) is predetermined, and in this embodiment, charging or discharging is performed at a low rate. The charging and discharging current and the C-rate are defined based on experiments, thus effectively reducing OCV errors.

[0056] In this embodiment, the charging and discharging unit 52 charges and discharges the first storage battery 31 by enabling energy exchange between the first storage battery 31 and the second storage battery 32. Specifically, the control device 50, which serves as the charging and discharging unit 52, switches on switches SMRH and SW2 to SW4 and controls the inverter 20 to convert (increase) the voltage of the second storage battery 32. As a result, the discharged power of the second storage battery 32 is supplied to the first storage battery 31, thereby charging the first storage battery 31. Similarly, the control device 50 switches on switches SMRH and SW2 to SW4 and controls the inverter 20 to convert the voltage of the first storage battery 31.As a result, the discharged power of the first storage battery 31 is supplied to the second storage battery 32, thereby charging the second storage battery 32.

[0057] In the present embodiment, the first storage battery 31 is charged and discharged by an energy exchange between the first storage battery 31 and the second storage battery 32. However, any other method can be used as long as charging and discharging can be carried out. For example, the first storage battery 31 can be discharged by supplying current to a predetermined electrical load connected to the first storage battery 31. The first storage battery 31 can be charged via the external battery charging device 40 and an electric generator (e.g., the motor 10) connected to the first storage battery 31.

[0058] The open-circuit voltage reference unit 54 obtains the open-circuit voltage (OCV) of the first storage battery 31 after it has been charged or discharged by the charge and discharge control unit 53. For example, the open-circuit voltage reference unit 54 switches off switches SW1 to SW4 to put the first storage battery 31 into an open-circuit state and obtains the open-circuit voltage of the first storage battery 31 from the first voltage sensor V11.

[0059] The state of charge estimation unit 55 refers to the OCV-SOC curve (charge and discharge curve) which indicates the relationship between the OCV of the first storage battery 31 and the SOC of the first storage battery 31, and estimates the SOC of the first storage battery 31 from the OCV of the first storage battery 31 which was obtained from the open-circuit voltage reference unit 54.

[0060] In the present embodiment, three OCV-SOC curves are prepared, as shown in Fig. Figure 3 shows that the OCV-SOC curve C11 is generated during charging, the OCV-SOC curve C12 is generated in the idle state (complete idle state), and the OCV-SOC curve C13 is generated during discharging. The OCV-SOC curve C11 is a charging curve that can be achieved by the SOC as a result of continuous charging from a defined lower limit to a defined upper limit at a predetermined current rate (C-rate). The OCV-SOC curve C12 is a curve that can be achieved by the SOC as a result of self-discharging from a defined upper limit to a defined lower limit. The OCV-SOC curve C13 is a discharging curve that can be achieved by the SOC as a result of continuous discharging from a defined upper limit to a defined lower limit at a predetermined current rate (C-rate).The OCV-SOC curves are identified through simulations and experiments and pre-stored, for example, in the memory of the control device 50.

[0061] The control device 50, which serves as the state-of-charge estimation unit 55, reads the OCV-SOC curve C11 during the charging process when the charge and discharge determination unit 52 determines that the first storage battery 31 is in a charged state. The control device 50 then refers to the OCV-SOC curve C11 to estimate the SOC of the first storage battery 31 from the OCV of the first storage battery 31, which was obtained from the open-circuit voltage reference unit 54.

[0062] The control device 50, which serves as the state-of-charge estimation unit 55, reads the OCV-SOC curve C13 during discharge when the charge and discharge determination unit 52 determines that the first storage battery 31 is in a discharged state. The control device 50 then refers to the OCV-SOC curve C13 to estimate the state of charge of the first storage battery 31 from the OCV of the first storage battery 31 as referenced by the open-circuit voltage reference unit 54.

[0063] The control device 50 reads the OCV-SOC curve C12 in the idle state when the charge / discharge determination unit 52 determines that the charge / discharge status is unknown, i.e., the first storage battery 31 is neither charged nor discharged. The control device 50 then refers to the OCV-SOC curve C12 to estimate the SOC of the first storage battery 31 from the OCV of the first storage battery 31 referenced by the open-circuit voltage reference unit 54.

[0064] Next, with reference to Fig. Section 5 describes a SOC estimation process for estimating the state of charge (SOC). The SOC estimation process is executed by the control device 50 after a SOC estimation command signal has been input from a higher-level control device and the charging or discharging of the first storage battery 31 is complete. The SOC estimation supply signal is output at a predetermined time, for example, when the vehicle stops.

[0065] When the SOC estimation process is started, the control device 50 determines, as shown in Fig. Figure 5 shows whether the charge and discharge counter stored in memory by the storage unit 51 indicates the first determined value J1 or higher, which represents the charging range (step S101).

[0066] If the result of the determination is positive, the control device 50 discharges the first storage battery 31 to reduce the SOC by a predetermined amount (approximately 5.0%) (step S102). After the first storage battery 31 has been discharged, the control device 50 obtains the OCV of the first storage battery 31 from the first voltage sensor V11 (step S103).

[0067] During the charging process, the control device 50 refers to the OCV-SOC curve C11 to estimate the SOC of the first storage battery 31 from the OCV of the first storage battery 31 obtained in step S103 (step S104). The SOC estimation process is then terminated.

[0068] If, however, the result of the determination in step S101 is negative, the control device 50 determines whether the charge and discharge counter stored in memory by the storage unit 51 indicates the second determined value J2 or less, which represents the discharge range (step S105). If the result of the determination is positive, the control device 50 charges the first storage battery 31 to increase the state of charge (SOC) by a predetermined amount (approximately 2.5%) (step S106). After the first storage battery 31 has been charged, the control device 50 obtains the open-circuit voltage (OCV) of the first storage battery 31 from the first voltage sensor V11 (step S107).

[0069] During discharge, the control device 50 refers to the OCV-SOC curve C13 to estimate the SOC of the first storage battery 31 from the OCV of the first storage battery 31 obtained in step S107 (step S108). The SOC estimation process is then terminated.

[0070] If, however, the result of the determination in step S105 is negative, the control device 50 charges the first storage battery 31 to increase the state of charge (SOC) by a predetermined amount and then discharges the first storage battery 31 to decrease the SOC by a predetermined amount (step S109). In step S109, it is desirable that the charge and discharge amounts are equal, but these amounts can also be different. It should be noted that the control device 50 can first discharge the first storage battery 31 to decrease the SOC by a predetermined amount and then charge the first storage battery 31 to increase the SOC by a predetermined amount.

[0071] After charging and discharging the first storage battery 31, the control device 50 obtains the OCV of the first storage battery 31 from the first voltage sensor V11 (step S110). The control device 50 then refers to the OCV-SOC curve C12 in the idle state to estimate the SOC of the first storage battery 31 from the OCV of the first storage battery 31 obtained in step S110 (step S111). The SOC estimation process is then terminated.

[0072] The processing in steps S101 and S105 corresponds to charge and discharge determination, and the control device 50 functions as a charge and discharge determination unit 52 by performing the processing. The processing in steps S102, S106, and S109 corresponds to charge and discharge control, and the control device 50 functions as a charge and discharge control unit 53 by performing the processing. The processing in steps S103, S107, and S110 corresponds to the detection of the open-circuit voltage, and the control device 50 functions as an open-circuit voltage reference unit 54 by performing the processing. The processing in steps S104, S108, and S111 corresponds to the processing for estimating the state of charge, and the control device 50 functions as a state-of-charge estimation unit 55 by performing the processing.

[0073] The SOC estimation process is described with reference to the [document / document / etc.]. Fig. 6 concrete examples are described. Fig. Figure 6(a) shows the charging and discharging currents for the first storage battery 31. Fig. 6(b) shows fluctuations in the charge and discharge counter value, and Fig. Figure 6(c) shows the results of the charging and discharging determination. Fig. 6(c) the positive (upper) level indicates that the battery is in a charged state, and the negative (lower) level indicates that the battery is in a discharged state. Fig. Figure 6(d) shows an OCV reference request flag that is turned on (set to a high level) when the SOC estimation process is started and turned off (set to a low level) when the OCV is referenced. Fig. 6(e) shows a charge and discharge termination flag which is turned off (set to a low level) when the first storage battery 31 is being charged or discharged, and turned on (set to a high level) when the first storage battery 31 is not being charged or discharged. Fig. Figure 6(f) shows a correction control flag that is turned on (set to a high level) when the load and discharge control for OCV error suppression is requested, and turned off (set to a low level) when the load and discharge control is completed. The load and discharge control for OCV error suppression is associated, for example, with the processing in steps S102, S106, and S109. Fig. 6(g) shows an OCV capture flag that is turned on (set to a high level) during the period from the beginning to the end of the OCV capture process (steps S103, S107 and S110).

[0074] As in the Fig. 6(a) and Fig. As shown in Figure 6(b), the charge and discharge counter increases and decreases according to the charge and discharge current value of the first storage battery 31 from time T1 to time T10. For example, from time T2 to time T4 and from time T7 to time T9, the current value of the first storage battery 31 remains greater than or equal to the first threshold Th1, so the charge and discharge counter increments at fixed time intervals. Similarly, from time T5 to T6, the current value of the first storage battery 31 remains less than or equal to the second threshold Th2, so the charge and discharge count decreases at fixed time intervals. From time T1 to T2, T4 to T5, T6 to T7, and T9 to T10, the current value of the first storage battery 31 is greater than the second threshold Th2 and less than the first threshold Th1, and thus the charge and discharge counter value is maintained.

[0075] As in Fig. As shown in Figure 6(b), the charge and discharge counter value at time T3 and thereafter is greater than or equal to the first determined value J1. Thus, the charge and discharge determination results at time T3 and thereafter, as shown in Figure 6(b), provide the following information: Fig. Figure 6(c) shows that the battery is in a charged state.

[0076] As in Fig. As shown in Figure 6(d), the OCV reference request flag is turned on when a SOC estimation command signal is entered at time T8. However, as shown in the Fig. 6(a) and Fig. As shown in Figure 6(e), the SOC estimation process enters a standby state without being started because the battery is being charged and discharged (the charge and discharge termination flag is not turned on).

[0077] When, at time T10, the charging and discharging of the first storage battery 31 is complete and the charge / discharge termination flag is turned on, the SOC estimation process is started. The correction control flag is turned on accordingly. At time T11, when a predetermined time has elapsed since the charge / discharge termination flag and the correction control flag were turned on, the charge / discharge control is performed to suppress OCV errors. In this state, as described in Fig. 6(c) shows that, since it is determined that the battery is in a charged state, the battery is discharged to suppress OCV errors (times T11 to T12). Then, at times T13 to T14, processing is carried out to obtain the OCV. After the OCV has been obtained, the SOC is estimated.

[0078] Next, the effects achieved through processing will be described. As in Fig. As shown in Figure 2(a), even if the SOC represents the same X% immediately after charging, fluctuations in the C-rate can lead to an error in the OCV. However, the OCV error is minimized by discharging the battery to reduce the SOC by a predetermined amount (in Figure 2(a)). Fig. 2(a) by shifting to the left). In this way, the OCV error due to differences in the C-rate can be minimized.

[0079] As in Fig. As shown in Figure 2(a), it was found that even if the first storage battery 31 is determined to be in a charged state, the OCV error can also be reduced by charging the first storage battery 31 to increase the SOC by a predetermined amount (shift to the right). However, as shown in Fig. As shown in 2(a), charging (shift to the right) is less effective at correcting errors compared to discharging (shift to the left) and requires a larger charging current.

[0080] Therefore, in the present embodiment, when the first storage battery 31 is determined to be in a charged state, it is discharged to reduce the state of charge (SOC) by a predetermined amount. This approach can shorten the time required to correct open circuit voltage (OCV) errors and also minimize SOC fluctuations caused by error correction (or error reduction; the same applies below).

[0081] As in Fig. As shown in Figure 2(b), even if the SOC represents the same value Y% immediately after discharge, fluctuations in the C-rate can lead to an error in the OCV. However, the OCV error is minimized by charging the battery to increase the SOC by a predetermined amount. In this way, the OCV error due to differences in the C-rate can be minimized.

[0082] As in Fig. As shown in Figure 2(b), it was found that even if the first storage battery 31 is determined to be in a discharged state, the OCV error can also be reduced by discharging the first storage battery 31 to decrease the SOC by a predetermined amount. However, as shown in Figure 2(b), Fig. As shown in Figure 2(b), discharging is less effective at correcting errors compared to charging and requires a larger discharge current.

[0083] Therefore, in the present embodiment, the first storage battery 31, when determined to be in a discharged state, is charged to increase the state of charge (SOC) by a predetermined amount. This approach can reduce the time required to correct open circuit voltage (OCV) errors and also minimize SOC fluctuations caused by error reduction.

[0084] The effects of the energy supply system 100 in the first embodiment are described below. Although the effects observed when measuring the first storage battery 31 are mainly described below, the same effects can also be observed when measuring the second storage battery 32.

[0085] The control device 50 discharges the first storage battery 31 when it is determined to be in a charged state, and charges it when it is determined to be in a discharged state, after which it obtains and determines the OCV (Open Circuit Value) of the first storage battery 31. This approach can minimize the OCV error caused by differences in the C-rate of the oxygen. Since the OCV error can be reduced, the SOC (State of Charge) error estimated based on the OCV can also be reduced.

[0086] The charge and discharge history is an integrated current value calculated by integrating the current flowing into or out of the first storage battery 31. Specifically, the integrated current value is determined by adding 1 to the charge and discharge counter during a charge with a predetermined quantity and subtracting 1 from the charge and discharge counter during a discharge with a predetermined quantity.

[0087] The control device 50 determines that the battery is in a charged state when the integrated current value is within the charging range that reflects a post-charging tendency or trend, and determines that the battery is in a discharged state when the integrated current value is within the discharge range that reflects a post-discharge trend or tendency. Specifically, when the charge and discharge counter indicates the first determination value J1 or higher, the control device 50 determines that the battery is in a charged state. When the charge and discharge counter indicates the second determination value J2 or lower, the control device 50 determines that the battery is in a discharged state.This allows the usage status of the first storage battery 31 to be accurately determined, as the determination can be based on the charging and discharging history over a specific period of time.

[0088] If the control device 50 cannot determine whether the battery is in a charged or discharged state based on the charge and discharge history, i.e., if the result of the determination in step S105 is negative, as specified in step S109, the first storage battery 31 is first charged and then discharged, or the first storage battery 31 is first discharged and then charged. This approach can minimize the OCV error associated with the C-rate, even if the state of the first storage battery 31 is unknown.

[0089] As can be seen from the comparison of the Fig. 2(a) and Fig. 2(b) as can be seen, unloading after loading ( Fig. 2(a)) less effective at correcting OCV errors than loading after unloading ( Fig. 2(b)). The control device 50 therefore determines different amounts of current for discharging the storage battery when it is in a charged state and for discharging the storage battery when it is in a discharged state. In particular, as specified in steps S102 and S105, the control device 50 discharges the battery to reduce the state of charge (SOC) by approximately 5.0% when it is determined that the battery is in a charged state and charges the battery to increase the SOC by approximately 2.5% when it is determined that the battery is in a discharged state. This approach can reduce the amount of charging current and the charging time required to correct the open-circuit voltage (OCV) error in step S105.

[0090] If it is determined that the first storage battery 31 is in a charged state (the result of the determination in step S101 is positive), the control device 50 refers to the OCV-SOC curve C11 during the charging process to estimate the SOC (step S104). If it is determined that the first storage battery 31 is in a discharged state (the result of the determination in step S105 is positive), the control device 50 refers to the OCV-SOC curve C13 during discharge to estimate the SOC (step S108). If the operating state of the first storage battery 31 is determined to be unknown (the results of the determination in steps S101 and S105 are negative), the control device 50 refers to the OCV-SOC curve C12 in the idle state to estimate the SOC (step S111).This approach makes it possible to estimate the SOC based on the influence of the hysteresis characteristic of the first storage battery 31 during charging and discharging and to suppress SOC errors. (Modifications)

[0091] The following describes modifications in which part of the design of the energy supply system 100 in the above embodiment is modified.

[0092] In the preceding embodiment, the degree of OCV error varies depending on the integrated current value. Therefore, in steps S102 and S105, the control device 50 can determine the charge and discharge currents based on the integrated current value. That is, if the integrated current value is large, the control device 50 can increase the charge and discharge currents. If the integrated current value is small, the control device 50 can decrease the charge and discharge currents. For example, if the absolute value of the charge and discharge counter, which indicates the integrated current value, is large, the control device 50 can increase the charge and discharge currents compared to the case where the absolute value is small.

[0093] In the preceding embodiment, the OCV-SOC curve (charge and discharge curve) varies due to the hysteresis characteristics of the storage batteries 31 and 32, depending on the operating conditions of the storage batteries 31 and 32, i.e., the amounts by which the batteries were charged and discharged. Thus, four or more OCV-SOC curves can be generated and linked to integrated current values, and the associated OCV-SOC curves can be identified by the corresponding integrated current values.

[0094] For example, if four or more OCV-SOC curves are stored in conjunction with charge and discharge curves indicating the integrated current value, the control device 50 can use the charge and discharge counter value indicating the integrated current value in steps S104, S108 and S111 to identify the corresponding OCV-SOC curve and estimate the SOC based on the identified charge and discharge curve.

[0095] - In the above embodiment, either the storage battery 31 or the storage battery 32 can be used, or three or more storage batteries can be used. As in Fig. As shown in Figure 7, the motor 10 and the inverter 20 can be replaced by DC-DC converters 121 and 122 for voltage conversion. As shown in Figure 7. Fig. As shown in Figure 8, the storage batteries 31 and 32 can be connected in parallel with the inverter 20 without using the motor 10.

[0096] In the storage process of the above embodiment, the results are accumulated. However, the battery status can be determined based on the most recent result. In particular, the result in Fig. The storage process shown in 9 will be adopted. The process is described in detail below. At the start of the process shown in Fig.In the storage process shown in Figure 9, according to a modification, the control device 50 determines whether the current value of the first storage battery 31 has remained continuously greater than or equal to the first threshold value Th1 for a predetermined time (step S21). That is, in step S21, it is determined whether the battery has been charged by the amount of current represented by the absolute value of the first threshold value Th1 multiplied by the predetermined time. If the result of the determination is positive, the control device 50 sets a value indicating that the battery is in a charged state (e.g., 1) on the charge and discharge counter stored in the memory of the control device 50 (step S22). The storage process is then terminated.

[0097] If the result of the determination in step S21 is negative, the control device 50 determines whether the current value of the first storage battery 31 has remained continuously less than or equal to the second threshold value Th2 for a predetermined time (step S23). That is, in step S23, it is determined whether the battery has been discharged by the amount of current represented by the absolute value of the second threshold value Th2 multiplied by the predetermined time. If the result of the determination is positive, the control device 50 sets a value indicating that the battery is in a discharged state (e.g., -1) on the charge and discharge counter (step S24). The storage process is then terminated.

[0098] If, however, the result of the determination in step S23 is negative, i.e., if it cannot be determined whether charging or discharging has occurred, the control device 50 sets a value indicating that the battery status is unknown (e.g., zero) in the charge and discharge counter (step S25) and terminates the storage process. In the SOC estimation process, the value of the charge and discharge counter is used to determine whether the battery status is charged, discharged, or unknown, and the determination result is used for charge and discharge control and OCV-SOC curve identification. This approach makes it possible to store the charge and discharge history through simple control.

[0099] - In the above embodiment, the integrated current value can be measured by a known method and used as a charging and discharging history.

[0100] The control unit and control method described in this disclosure can be implemented by a special-purpose computer comprising a memory and a processor programmed to execute one or more functions embodied by computer programs. Alternatively, the control unit and control method described in this disclosure can be implemented by a special-purpose computer comprising a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and control method described in this disclosure can also be implemented by one or more special-purpose computers comprising a combination of a memory and a processor programmed to execute one or more functions, and a processor with one or more hardware logic circuits.Computer programs can be stored in a non-volatile, tangible, computer-readable storage medium as instructions executed by a computer.

[0101] The following describes characteristic configurations extracted from the exemplary embodiments described above. [Configuration 1]

[0102] A state-of-charge estimating device (50) for estimating the state of charge of a storage battery, wherein the state-of-charge estimating device comprises: a storage unit (51) that stores the charging and discharging history of the storage battery; a charge and discharge determination unit (52) which determines, on the basis of the charge and discharge history stored in the storage unit, whether the storage battery is in a charged state or in a discharged state; a charging and discharging control unit (53) that discharges the storage battery by a predetermined amount when the charging and discharging determination unit determines that the storage battery is in a charged state, and charges the storage battery by a predetermined amount when the charging and discharging determination unit determines that the storage battery is in a discharged state; an open-circuit voltage reference unit (54) which obtains the open-circuit voltage of the storage battery after the charge and discharge control unit has charged or discharged the storage battery; and a state-of-charge estimation unit (55) which refers to a charging and discharging curve which specifies the relationship between the open-circuit voltage of the storage battery and the state of charge of the storage battery in order to estimate the state of charge of the storage battery from the open-circuit voltage referenced by the open-circuit voltage reference unit. [Configuration 2]

[0103] The charge state estimation device according to configuration 1, wherein The charging and discharging history is an integrated current value calculated by integrating a current flowing into or out of the storage battery, and The charge and discharge determination unit determines that the battery is in a charged state when the integrated current value is within a charge range that reflects a recharge tendency, and determines that the battery is in a discharged state when the integrated current value is within a discharge range that reflects a recharge tendency. [Configuration 3]

[0104] The charge state estimation device according to configuration 2, wherein The charging and discharging control unit determines the amounts of charging and discharging current based on the integrated current value. [Configuration 4]

[0105] The charge state estimation device according to configuration 2, wherein Each integrated current value is pre-associated with the corresponding charging and discharging curve and The state-of-charge estimation unit identifies the corresponding charging and discharging curve based on the associated integrated current value and estimates the state of charge based on the identified charging and discharging curve. [Configuration 5]

[0106] The charge state estimation device according to one of configurations 1 to 4, wherein If the charge and discharge determination unit cannot determine whether the battery is in a charged or discharged state based on the charge and discharge history, the charge and discharge control unit first charges the storage battery and then discharges the storage battery by a predetermined amount, or first discharges the storage battery and then charges the storage battery by a predetermined amount. [Configuration 6]

[0107] The charge state estimation device according to one of configurations 1 to 5, wherein The charging and discharging control unit determines different amounts of current for discharging the storage battery when it is in a charged state and for discharging the storage battery when it is in a charged state. [Configuration 7]

[0108] The charge state estimation device according to one of configurations 1 to 6, wherein When the charge and discharge determination unit determines that the storage battery is in a charged state, the state-of-charge estimation unit refers to the charge curve, which indicates the relationship between the open-circuit voltage and the state of charge during the charging process, to estimate the state of charge; when the charge and discharge determination unit determines that the storage battery is in a discharged state, the state-of-charge estimation unit refers to the discharge curve, which indicates the relationship between the open-circuit voltage and the state of charge during the discharge process, to estimate the state of charge. [Configuration 8]

[0109] A state-of-charge estimation system (100) comprising a first storage battery and a second storage battery and estimating the states of charge of the first storage battery and the second storage battery, wherein the state-of-charge estimation system has: a storage unit (51) configured to store a charge and discharge history of each storage battery; a charge and discharge determination unit (52) configured to determine, for each of the storage batteries, whether each of the storage batteries is in a charged state or in a discharged state, based on the charge and discharge history stored in the storage unit; a charging and discharging control unit (53) configured to discharge the storage battery identified by the charging and discharging determination unit as being in a charged state, and to charge the storage battery identified by the charging and discharging determination unit as being in a discharged state; an open-circuit voltage reference unit (54) configured to obtain an open-circuit voltage from each of the storage batteries after the charge and discharge control unit has charged or discharged each of the storage batteries; and a state-of-charge estimation unit (55) configured to reference a charge and discharge curve which specifies a relationship between the open-circuit voltage of the storage battery and the state of charge of the storage battery, in order to estimate the state of charge of each of the storage batteries from the open-circuit voltage of the corresponding storage battery referenced by the open-circuit voltage reference unit, wherein the charging and discharging control unit charges and discharges each of the storage batteries by allowing an energy exchange between the first storage battery and the second storage battery. [Configuration 9]

[0110] A state-of-charge estimation program that causes a state-of-charge estimation device (50) to perform the following for estimating the state of charge of a storage battery: a storage process for saving a charging and discharging history of the storage battery; a charge and discharge determination process to determine whether the storage battery is being charged or discharged, based on the charge and discharge history stored by the storage process; a charge and discharge control process for discharging the storage battery when the charge and discharge determination process determines that the storage battery is being charged, and for charging the storage battery when the charge and discharge determination process determines that the storage battery is being discharged; an open-circuit voltage reference process for obtaining an open-circuit voltage from the storage battery after the charge and discharge control process has charged or discharged the storage battery; and a state-of-charge estimation process to refer to a charging and discharging curve that specifies a relationship between the open-circuit voltage of the storage battery and the state of charge of the storage battery, in order to estimate the state of charge of the storage battery from the open-circuit voltage obtained through the open-circuit voltage sensing process.

[0111] Although the present disclosure has been described according to exemplary embodiments, it is understood that the disclosure is not limited to the embodiments or structures described above. The disclosure includes various modifications and changes that fall within the scope of equivalence. Furthermore, various combinations and forms, as well as other combinations and forms to which one, more than one, or fewer than one element has been added, also fall within the scope and the basic concept of the present disclosure. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2023-074306

[0001] JP 2020-38146 A

[0004]

Claims

[1] State-of-charge estimation device (50) for estimating the state of charge of a storage battery, the state-of-charge estimation device comprising: a storage unit (51) configured to store a charging and discharging history of the storage battery; a charge and discharge determination unit (52) configured to determine, based on the charge and discharge history stored in the storage unit, whether the storage battery is in a charged state or in a discharged state; a charge and discharge control unit (53) configured to discharge the storage battery by a predetermined amount when the charge and discharge determination unit determines that the storage battery is in a charged state, and to charge the storage battery by a predetermined amount when the charge and discharge determination unit determines that the storage battery is in a discharged state; an open-circuit voltage reference unit (54) configured to obtain an open-circuit voltage of the storage battery after the charge and discharge control unit has charged or discharged the storage battery; and a state-of-charge estimation unit (55) configured to reference a charge and discharge curve which specifies a relationship between the open-circuit voltage of the storage battery and the state of charge of the storage battery, in order to estimate the state of charge of the storage battery from the open-circuit voltage referenced by the open-circuit voltage reference unit. [2] Charge state estimation device according to claim 1, wherein The charging and discharging history is an integrated current value calculated by integrating a current flowing into or out of the storage battery, and The charge and discharge determination unit determines that the battery is in a charged state when the integrated current value is within a charge range that reflects a recharge tendency, and determines that the battery is in a discharged state when the integrated current value is within a discharge range that reflects a recharge tendency. [3] State of charge estimation device according to claim 2, wherein the charging and discharging control unit determines quantities of charging and discharging currents based on the integrated current value. [4] Charge state estimation device according to claim 2, wherein Each integrated current value is pre-associated with a corresponding charging and discharging curve, and The state-of-charge estimation unit identifies the corresponding charging and discharging curve from the associated integrated current value and estimates the state of charge based on the identified charging and discharging curve. [5] State-of-charge estimation device according to any one of claims 1 to 4, wherein if the charge and discharge determination unit fails to determine from the charge and discharge history whether the battery is in a charged or discharged state, the charge and discharge control unit first charges the storage battery and then discharges the storage battery by a predetermined amount or first discharges the storage battery and then charges the storage battery by a predetermined amount. [6] State of charge estimation device according to any one of claims 1 to 4, wherein the charging and discharging control unit determines different amounts of current for discharging the storage battery which has been determined to be in a charged state, and for discharging the storage battery which has been determined to be in a charged state. [7] State-of-charge estimation device according to any one of claims 1 to 3, wherein when the charge and discharge determination unit determines that the storage battery is in a charged state, the state-of-charge estimation unit refers to a charge curve which specifies a relationship between the open-circuit voltage and the state of charge during the charging process in order to estimate the state of charge, whereas when the charge and discharge determination unit determines that the storage battery is in a discharged state, the state-of-charge estimation unit refers to a discharge curve which specifies a relationship between the open-circuit voltage and the state of charge during the discharge process in order to estimate the state of charge. [8] State-of-charge estimation system (100) comprising a first storage battery and a second storage battery and estimating the states of charge of the first storage battery and the second storage battery, wherein the state-of-charge estimation system includes: a storage unit (51) configured to store a charge and discharge history of each storage battery; a charge and discharge determination unit (52) configured to determine, for each of the storage batteries, whether each of the storage batteries is in a charged state or in a discharged state, based on the charge and discharge history stored in the storage unit; a charging and discharging control unit (53) configured to discharge the storage battery identified by the charging and discharging determination unit as being in a charged state, and to charge the storage battery identified by the charging and discharging determination unit as being in a discharged state; an open-circuit voltage reference unit (54) configured to obtain an open-circuit voltage from each of the storage batteries after the charge and discharge control unit has charged or discharged each of the storage batteries; and a state-of-charge estimation unit (55) configured to reference a charge and discharge curve which specifies a relationship between the open-circuit voltage of the storage battery and the state of charge of the storage battery, in order to estimate the state of charge of each of the storage batteries from the open-circuit voltage of the corresponding storage battery referenced by the open-circuit voltage reference unit, wherein the charging and discharging control unit charges and discharges each of the storage batteries by allowing an energy exchange between the first storage battery and the second storage battery. [9] State-of-charge estimation program which causes a state-of-charge estimation device (50) to perform the following for estimating the state of charge of a storage battery: a storage process for saving a charging and discharging history of the storage battery; a charge and discharge determination process to determine whether the storage battery is being charged or discharged, based on the charge and discharge history stored by the storage process; a charge and discharge control process for discharging the storage battery when the charge and discharge determination process determines that the storage battery is being charged, and for charging the storage battery when the charge and discharge determination process determines that the storage battery is being discharged; an open-circuit voltage reference process for obtaining an open-circuit voltage from the storage battery after the charge and discharge control process has charged or discharged the storage battery; and a state-of-charge estimation process to refer to a charging and discharging curve that specifies a relationship between the open-circuit voltage of the storage battery and the state of charge of the storage battery, in order to estimate the state of charge of the storage battery from the open-circuit voltage obtained through the open-circuit voltage sensing process.

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