Estimation device, power storage device, estimation method, and estimation program

Abstract

This estimation device comprises: an acquisition unit that acquires the state of a power storage element; and an estimation unit that, on the basis of the acquired state of the power storage element and information of an energization pattern applied to a model of the power storage element, estimates the state of charge of the power storage element which satisfies a prescribed charging capacity or discharging capacity.

Description

Estimation device, power storage device, estimation method, and estimation program

[0001] The present invention relates to an estimation device, a power storage device, an estimation method, and an estimation program.

[0002] Secondary batteries are widely used as power sources for vehicles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), as well as other mobile objects. Techniques relating to charging and discharging devices for controlling the charging and discharging of secondary batteries have been disclosed (for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-11531

[0004] Generally, a charging / discharging device controls charging / discharging so that the SOC of a secondary battery falls within a preset usable SOC range. Conventionally, the setting of the usable SOC range does not take into account the charging or discharging capacity of the storage element.

[0005] An object of the present disclosure is to provide a technology capable of estimating the SOC of a storage element suitable for use in consideration of the charge capacity or discharge capacity of the storage element.

[0006] An estimation device according to one aspect of the present disclosure includes an acquisition unit that acquires the state of a storage element, and an estimation unit that estimates the SOC of the storage element that satisfies a predetermined charging capacity or discharging capacity based on the acquired state of the storage element and information on a current pattern provided to a model of the storage element.

[0007] According to the present disclosure, the SOC of an energy storage element suitable for use can be estimated by taking into account the charge capacity or discharge capacity of the energy storage element.

[0008] Fig. 1 is a perspective view showing a configuration example of a power storage device; Fig. 2 is an exploded perspective view of a power storage device; Fig. 3 is a block diagram showing a configuration example of a power storage device including an estimation device; Fig. 4 is a circuit diagram showing an example of a power storage element model; Fig. 5 is a flowchart showing an example of a processing procedure executed by the estimation device; Fig. 6 is a flowchart showing an example of a processing procedure executed by the estimation device of a second embodiment;

[0009] (1) An estimation device according to one aspect of the present disclosure includes an acquisition unit that acquires the state of a storage element, and an estimation unit that estimates an SOC of the storage element that satisfies a predetermined charging capacity or discharging capacity based on the acquired state of the storage element and information on a current pattern provided to a model of the storage element.

[0010] Here, the "energy storage element" may be a energy storage cell or a energy storage unit having a plurality of energy storage cells. The "energy conduction pattern information" may include a current value representing the energy conduction pattern and a current conduction time for that current value. The "SOC of the energy storage element satisfying a predetermined charging or discharging capacity" refers to the SOC of the energy storage element that can be charged or discharged in a specific energy conduction pattern without deviating from a predetermined voltage range, e.g., an SOC range defined by an upper and lower SOC limit. Hereinafter, the SOC of the energy storage element satisfying a predetermined charging or discharging capacity will also be referred to as a usable SOC range. The usable SOC range refers to an SOC suitable for use of the energy storage element. The estimation unit may use a model of the energy storage element to predict the voltage behavior of the energy storage element when energized in the energy conduction pattern, and estimate the SOC value of the energy storage element based on the predicted voltage behavior of the energy storage element. The estimation unit may identify the SOC value of the storage element that can satisfy the specified charging capacity or discharging capacity by determining whether the voltage behavior of the storage element predicted by the model satisfies the specified charging capacity or discharging capacity.

[0011] According to the estimation device described in (1) above, it is possible to estimate the usable SOC range by taking into account the charge capacity or discharge capacity (charge / discharge capacity) of the storage element. The usable SOC range can be dynamically estimated according to the required charge / discharge capacity, i.e., the expected current pattern. Compared to a case where a fixed usable SOC range is set in advance, the usable SOC range of the storage element can be flexibly adjusted, increasing the degree of freedom of the SOC.

[0012] As an example, a case will be described in which the energy storage element is a low-voltage battery mounted on a vehicle. A charge / discharge control device mounted on the vehicle controls charging / discharging of the energy storage element while the vehicle is running so that the SOC of the energy storage element is within a specific SOC range. Also, while the vehicle is parked, the energy storage element is charged using the vehicle's high-voltage system or alternator when the specific SOC is reached so that the energy storage element can maintain an SOC that allows the energy storage element to exhibit a predetermined power supply performance.

[0013] Conventionally, charge / discharge control devices use a preset fixed SOC range (e.g., SOC 70% to 80%) as the usable SOC range for charge / discharge control. A power storage device equipped with a power storage element constantly monitors the current SOC of the power storage element and notifies the charge / discharge control device. The charge / discharge control device performs the above-described charge / discharge control so that the current SOC of the power storage element notified by the power storage device falls within the usable SOC range. When the usable SOC range is set in advance, a relatively narrow SOC range is set so that power supply performance can be reliably demonstrated regardless of the usage state of the power storage element. As a result, the performance of the power storage element is not fully demonstrated. While driving, charge / discharge is controlled within a narrow SOC range, even though a wider SOC range is actually usable. While parking, recharging occurs at a high SOC, even though charging is not actually required yet.

[0014] While the above-described charge / discharge control of the storage element is being performed, in recent years, a function for estimating the power supply performance (SOF: State Of Function) of the storage element has been required to realize autonomous driving functions and safety functions in vehicles. The storage device determines at predetermined intervals whether charging or discharging according to a predetermined current conduction pattern (whether or not current can be passed) and notifies the vehicle of the determination result. In this case, only whether current can be passed is determined, and the SOC percentage above or below which current can be passed in the actual state of the storage element is not taken into consideration. In other words, the charge / discharge control of the storage element and the SOF estimation are performed independently.

[0015] According to the above configuration, the usable SOC range can be estimated taking into account the charge / discharge capacity of the storage element. By dynamically estimating the usable SOC range taking into account the charge / discharge capacity of the storage element, a wide SOC range can be set for charge / discharge control. The charge / discharge performance of the storage element can be fully utilized, the degree of freedom in energy management can be increased, and the power consumption and fuel economy of charging from the charging system can be improved. In charging, compared to when the SOC at which recharging is performed is preset as a fixed value, it is possible to prevent vehicle function limitations after vehicle startup due to recharging being too slow, and to prevent frequent vehicle startup while parked due to recharging being too fast.

[0016] (2) In the estimation device described in (1) above, the state of the storage element may include at least one of a deterioration state, a temperature, and a polarization state of the storage element at the time of estimation.

[0017] The "deterioration state" may be the capacity maintenance rate (SOH: State of health) of the energy storage element, the full charge capacity, or the rate of increase in internal resistance. The "polarization state" may be the degree of deviation between the theoretical electromotive force of the energy storage element and the actual operating voltage.

[0018] According to the estimation device described in (2) above, it is possible to accurately estimate the usable SOC range by taking into account the deterioration state and temperature of the storage element at the time of estimation, which greatly affect the voltage behavior of the storage element. The estimation time means the present, for example, when estimation is performed in real time.

[0019] (3) In the estimation device described in (1) or (2) above, the SOC of the storage element may include a lower limit value of the SOC of the storage element that satisfies a predetermined discharge capacity estimated based on information on a discharge pattern provided to the model.

[0020] According to the estimation device described in (3) above, it is possible to estimate the lower limit of the SOC at which the battery can be discharged in a predetermined discharge pattern, thereby optimizing discharge control. The lower limit of the SOC may be the lowest SOC at which the battery can be discharged without falling below a predetermined threshold voltage.

[0021] (4) In the estimation device described in any one of (1) to (3) above, the SOC of the storage element may include an upper limit value of the SOC of the storage element that satisfies a predetermined charging capacity estimated based on information on a charging pattern provided to the model.

[0022] According to the estimation device described in (4) above, it is possible to estimate the upper limit of the SOC that can accept charging in a predetermined charging pattern, thereby optimizing charging control. The upper limit of the SOC may be the highest SOC value that can accept charging without exceeding a predetermined threshold voltage.

[0023] (5) In the estimation device described in any one of (1) to (4) above, the estimation unit may search for an upper or lower limit value of the SOC of the storage element by sequentially increasing or decreasing the SOC value from a starting SOC, and determining whether the voltage behavior of the storage element predicted by the model satisfies the predetermined charging capacity or discharging capacity based on the SOC value of the storage element after the increase or decrease, the state of the storage element, and information on the current flow pattern.

[0024] For example, when searching for an SOC value that satisfies a predetermined charge / discharge capacity by predicting voltage behavior using an equivalent circuit model as a model of a storage element, the parameters of the equivalent circuit model have SOC dependency. Finding an SOC value such that the predicted voltage using the equivalent circuit model including parameters that have SOC dependency becomes the threshold voltage requires complex calculations. According to the estimation device described in (5) above, by sequentially changing the SOC value from the initial SOC, an SOC value that satisfies the predetermined charge / discharge capacity can be efficiently and accurately searched for, thereby reducing the computational load and computation time required for estimating the SOC value.

[0025] (6) In the estimation device according to any one of (1) to (5) above, the estimation unit may derive a recommended SOC based on the estimated SOC of the power storage element.

[0026] According to the estimation device described in (6) above, a recommended SOC that is recommended for use can be set according to the estimated usable SOC range. The recommended SOC may be, for example, a portion of the estimated usable SOC range, or may be a value obtained by adding a predetermined required SOC to the estimated usable SOC range. For example, by setting a relatively low SOC range within the estimated SOC range as the recommended SOC range, it is possible to prevent the storage element from being repeatedly used in a high SOC range, and it is expected that the degradation of the storage element will be suppressed.

[0027] (7) In the estimation device described in any one of (1) to (6) above, a temperature estimation unit may be provided that, when the estimated lower limit value of the SOC of the storage element is equal to or greater than a threshold value, estimates the temperature of the storage element that satisfies a predetermined discharge capacity.

[0028] If the temperature of the storage element is too low, it may be determined that power cannot be supplied according to a predetermined discharge pattern even if the storage element is charged until the SOC reaches a predetermined value (for example, SOC 100%). In such a case, the estimation device described in (7) above can estimate the temperature of the storage element that can supply power, thereby making it possible to preferably perform temperature increase control of the storage element.

[0029] (8) The estimation device according to any one of (1) to (7) above may further include an output unit that outputs the estimated SOC of the power storage element to an external device.

[0030] According to the estimation device described in (8) above, the estimation result can be reliably notified to an external device.

[0031] (9) The estimation device according to any one of (1) to (8) above may further include an output unit that outputs the estimated SOC of the storage element to an external device that controls charging and discharging of the storage element.

[0032] According to the estimation device described in (9) above, the estimation result can be reliably notified to an external device that performs charge / discharge control, and the external device can suitably perform charge / discharge control of the storage element in accordance with the estimation result.

[0033] (10) A power storage device according to one aspect of the present disclosure includes a power storage element and the estimation device according to any one of (1) to (9) above.

[0034] (11) An estimation method according to one aspect of the present disclosure acquires the state of a storage element, and estimates the SOC of the storage element that satisfies a predetermined charging capacity or discharging capacity based on the acquired state of the storage element and information on a current pattern provided to a model of the storage element.

[0035] (12) An estimation program according to one aspect of the present disclosure acquires the state of a storage element, and causes a computer to execute a process of estimating the SOC of the storage element that satisfies a predetermined charging capacity or discharging capacity based on the acquired state of the storage element and information on a current pattern provided to a model of the storage element.

[0036] Hereinafter, the present disclosure will be specifically described with reference to the drawings showing embodiments thereof.

[0037] (First embodiment) Fig. 1 is a perspective view showing a configuration example of a power storage device 1, and Fig. 2 is an exploded perspective view of the power storage device 1. Below, the configuration example of the power storage device 1 will be described with reference to the "front-rear," "left-right," and "up-down" directions shown in the drawings.

[0038] The power storage device 1 is a battery that is suitable for installation in, for example, an engine vehicle, an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc. The power storage device 1 is, for example, a 12 volt (V) battery or a 48 V battery.

[0039] The energy storage device 1 includes a plurality of energy storage cells 2, an estimation device 3, and a busbar unit 4. The energy storage device 1 is an example of an energy storage element. The energy storage cells 2, the estimation device 3, and the busbar unit 4 are housed inside a housing case 10. The energy storage cells 2 are, for example, battery cells formed of lithium-ion secondary batteries.

[0040] In an embodiment, the storage element is a storage unit having a plurality of storage cells 2. Alternatively, the storage element may be a single storage cell 2.

[0041] The estimation device 3 is, for example, a battery management system (BMS). The estimation device 3 acquires measurement data including the voltages of the storage cells 2 and the storage device 1, the current flowing through the storage cells 2, and the temperature related to the storage device 1. Based on the acquired measurement data, the estimation device 3 estimates the SOC (usable SOC range) of the storage device 1 that satisfies a predetermined charging capacity or discharging capacity. The usable SOC range of the storage device 1 is, for example, an SOC range defined by an upper limit and a lower limit of the SOC value.

[0042] In the embodiment, the estimation device 3 is mounted inside the power storage device 1. Alternatively, the estimation device 3 may be installed remotely from the power storage device 1. The estimation device 3 may be a computer such as a server device, a terminal device, or a vehicle ECU connected to the outside of the power storage device 1. In this case, measurement data measured regarding the power storage device 1 may be transmitted to the server device or the like via communication.

[0043] The storage case 10 is made of synthetic resin. The storage case 10 includes a case body 11 with an open top and a cover 12 that covers the opening of the case body 11. The case body 11 and the cover 12 are fixed in a liquid-tight manner using fasteners such as screws, adhesive, welding, or the like, with the energy storage cells 2, the estimation device 3, and the busbar unit 4 housed inside. A pair of external terminals 13A and 13B with opposite polarities are provided on one side of the storage case 10.

[0044] The storage cell 2 includes a hollow rectangular parallelepiped case 21. A positive terminal 22 and a negative terminal 23 of the storage cell 2 are provided on the upper surface of the case 21. The case 21 accommodates an electrode assembly, an electrolyte, and the like (not shown).

[0045] The electrode assembly is constructed by stacking a sheet-shaped positive electrode and a sheet-shaped negative electrode with two sheet-shaped separators in between and winding them (vertical or horizontal). The separators are formed of a porous resin film. Examples of the porous resin film include a porous resin film made of a resin such as polyethylene (PE) or polypropylene (PP).

[0046] The positive electrode is an electrode plate in which a positive electrode active material layer is formed on the surface of a long strip-shaped positive electrode substrate made of, for example, aluminum or an aluminum alloy. The positive electrode active material layer contains a positive electrode active material. The positive electrode active material used in the positive electrode active material layer can be a material capable of absorbing and releasing lithium ions. An example of the positive electrode active material is LiFePO4. The positive electrode active material layer may further contain a conductive additive, a binder, etc.

[0047] The negative electrode is an electrode plate in which a negative electrode active material layer is formed on the surface of a long strip-shaped negative electrode substrate made of, for example, copper or a copper alloy. The negative electrode active material layer contains a negative electrode active material. The negative electrode active material can be a material capable of absorbing and releasing lithium ions. Examples of the negative electrode active material include graphite, hard carbon, and soft carbon. The negative electrode active material layer may further contain a binder, a thickener, and the like.

[0048] The electrolyte can be the same as that used in conventional lithium-ion secondary batteries. For example, an electrolyte containing a supporting salt in an organic solvent can be used. As the organic solvent, for example, an aprotic solvent such as carbonates, esters, or ethers can be used. As the supporting salt, for example, a lithium salt such as LiPF6, LiBF4, or LiClO4 can be suitably used. The electrolyte may contain various additives such as a gas generating agent, a film-forming agent, a dispersant, or a thickener.

[0049] In the embodiment, the power storage cell 2 is a battery cell based on a lithium ion secondary battery. Alternatively, the power storage cell 2 may be a battery cell based on an all-solid-state battery, a lead battery, a redox flow battery, a zinc-air battery, an alkaline manganese battery, a lithium-sulfur battery, a sodium-sulfur battery, a silver-zinc oxide battery, a nickel-metal hydride battery, a molten salt thermal battery, or the like, or may be a capacitor.

[0050] In the embodiment, the energy storage cell 2 is a rectangular battery cell with a wound electrode assembly. Alternatively, the energy storage cell 2 may be a cylindrical battery cell, a laminated (pouch) battery cell, or a battery cell with a stacked electrode assembly.

[0051] In the embodiment, the number of storage cells 2 housed in the case body 11 is four. Alternatively, the number of storage cells 2 housed in the case body 11 may be one or more and less than four, or may be more than four. In the following description, the storage cells 2 will also be referred to as a first storage cell 2A, a second storage cell 2B, a third storage cell 2C, and a fourth storage cell 2D, in that order from the front side of the case body 11.

[0052] As shown in FIG. 2, each storage cell 2 is housed in the case body 11 such that the positive terminals 22 and negative terminals 23 of adjacent storage cells 2 face in opposite directions.

[0053] The estimating device 3 is disposed on the terminal surface of the energy storage cell 2 via a busbar unit 4. The busbar unit 4 includes a plurality of busbars 41 and a resin busbar frame 42 that holds these busbars 41. Each busbar 41 is connected to the underside of the estimating device 3 by a fastener 43 such as a screw. The energy storage cell 2 and the estimating device 3 are connected via the busbar 41.

[0054] The bus bar 41 constitutes a charge / discharge path for the energy storage cells 2. The bus bar 41 is made of metal, and is formed of a material with excellent electrical conductivity and high thermal conductivity, such as aluminum, an aluminum alloy, copper, a copper alloy, or stainless steel. The bus bar 41 electrically connects the positive terminal 22 of one of the energy storage cells 2 to the negative terminal 23 of the other of the adjacent energy storage cells 2. The bus bar 41 also connects the negative terminal 23 of the first energy storage cell 2A to one external terminal 13A, and also connects the positive terminal 22 of the fourth energy storage cell 2D to the other external terminal 13B.

[0055] 1 and 2, a configuration has been described in which four storage cells 2 are connected in series by the bus bar 41. Alternatively, some or all of the storage cells 2 may be connected in parallel.

[0056] The estimation device 3 includes a flat circuit board 61. A shutoff circuit 62, a temperature sensor 63, a current sensor 64, a voltage sensor 65 (see FIG. 3 ), and the like are mounted on the upper surface of the circuit board 61. The estimation device 3 may be configured as a circuit board unit in which the shutoff circuit 62, the temperature sensor 63, the current sensor 64, and the voltage sensor 65 are mounted on the circuit board 61.

[0057] The interrupting circuit 62 is a circuit for connecting or disconnecting a conductive path between the bus bar 41 connected to the positive terminal 22 of the fourth storage cell 2D and the bus bar 66 connected to the external terminal 13B. The interrupting circuit 62 is configured by a semiconductor switch such as a metal oxide semiconductor field effect transistor (MOSFET). By switching the interrupting circuit 62 from an on state to an off state, it is possible to block current from flowing out from the storage cell 2 to the outside and current from flowing in from the outside to the storage cell 2. Alternatively, the interrupting circuit 62 may be configured by a relay switch.

[0058] The temperature sensor 63 is, for example, a thermistor, a thermocouple, or the like. The temperature sensor 63 measures the temperature related to the energy storage device 1. In FIG. 2 , the temperature sensor 63 is disposed at a position sufficiently separated from the energized heating elements (e.g., the interrupter circuit 62, the bus bars 41 and 66, the fasteners 48, etc.) on the circuit board 61. The temperature data measured by the temperature sensor 63 represents the ambient temperature of the energy storage device 1 (the ambient temperature of the energy storage cells 2). The energy storage element may further include a temperature sensor 63 disposed near the energized heating elements on the circuit board 61 and measuring the temperature of the energized heating elements on the circuit board 61. In this case, the temperature of the energy storage device 1 may be determined based on the ambient temperature of the energy storage device 1 and the temperature of the energized heating elements on the circuit board 61.

[0059] 3 is a block diagram showing an example of the configuration of the power storage device 1 including the estimation device 3. The power storage device 1 is connected to a vehicle ECU (Electronic Control Unit) 71, an electrical load 72 such as electrical equipment, and an alternator (not shown) via external terminals 13A and 13B.

[0060] If the vehicle is an engine vehicle, while the engine is running, if the amount of power generated by the alternator is greater than the amount of power consumed by the electrical load 72, the electrical storage device 1 is charged by the alternator. If the amount of power generated by the alternator is less than the amount of power consumed by the electrical load 72, the electrical storage device 1 discharges to make up for the shortfall. When the vehicle is parked, the alternator stops generating power, so the electrical storage device 1 is not charged and only discharges to the vehicle ECU 71 and the electrical load 72.

[0061] When the vehicle can start traveling using a high-voltage system (driving power storage device) instead of an internal combustion engine, the power storage device 1 supplies power to start the high-voltage system. While the vehicle is parked, the power storage device 1 discharges power to the vehicle ECU 71 and the electrical load 72, and can also be charged by the high-voltage system.

[0062] The vehicle ECU 71 is a vehicle control unit that controls the vehicle. The vehicle ECU 71 controls the electric load 72. The vehicle ECU 71 controls the charge or discharge amount of the power storage device 1 by controlling the electric load 72 based on the estimation result of the usable SOC range received from the estimation device 3. The vehicle ECU 71 is an example of a higher-level device, and is an example of an external device (charge / discharge control device) that controls the charge and discharge of the power storage device 1.

[0063] The estimation device 3 is a computer and includes a control unit 31, a storage unit 32, an input / output unit 33, and a communication unit 34. In this embodiment, the estimation device 3 is realized by a circuit board, but alternatively, the estimation device 3 may be configured to perform distributed processing using multiple computers, may be realized by multiple virtual machines provided in a single server, or may be realized using a cloud server.

[0064] The control unit 31 is an arithmetic circuit including a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The CPU or GPU included in the control unit 31 executes various computer programs stored in the ROM or the storage unit 32, and controls the operation of each of the above-mentioned hardware components. The control unit 31 may also include functions such as a timer that measures the elapsed time from when an instruction to start measurement is given until when an instruction to end measurement is given, a counter that counts numbers, and a clock that outputs date and time information.

[0065] The storage unit 32 includes a non-volatile storage device such as a flash memory, a hard disk drive, etc. The storage unit 32 stores various computer programs and data referenced by the control unit 31. The storage unit 32 may be an external storage device connected to the estimation device 3.

[0066] The storage unit 32 of this embodiment stores an estimation program 321 for causing a computer to execute processing related to estimation of the usable SOC range of the power storage device 1, and estimation data 322 as data necessary for executing the estimation program 321. The estimation data 322 includes a power storage element model used in the simulation. The power storage element model is described by configuration information indicating the circuit configuration and values ​​of each element constituting the power storage element model. The storage unit 32 stores the configuration information indicating the circuit configuration of the power storage element model and values ​​of each element constituting the power storage element model.

[0067] A computer program (computer program product) including the estimation program 321 may be provided by a non-transitory recording medium 3A on which the computer program is readably recorded. The recording medium 3A is, for example, a portable memory such as a magnetic disk, an optical disk, or a semiconductor memory. The control unit 31 reads a desired computer program from the recording medium 3A using a reading device (not shown) and stores the read computer program in the storage unit 32. Alternatively, the computer program may be provided via communication. The estimation program 321 may be a single computer program or may be composed of multiple computer programs, and may be executed on a single computer or multiple computers interconnected by a communication network.

[0068] The input / output unit 33 includes an input / output interface for connecting to an external device, and is connected to a cutoff circuit 62, a temperature sensor 63, a current sensor 64, a voltage sensor 65, and the like.

[0069] The control unit 31 switches the interruption circuit 62 between an on state and an off state by outputting a control signal to the interruption circuit 62 via the input / output unit 33. The control unit 31 also acquires, via the input / output unit 33, temperature data measured by the temperature sensor 63, current data measured by the current sensor 64, and voltage data measured by the voltage sensor 65 as needed.

[0070] The current sensor 64 is, for example, a shunt resistor, and is connected in series to the storage cell 2. The current sensor 64 measures the current flowing through the storage cell 2 in a time series manner based on the voltage across the storage cell 2. Discharging and charging can be determined from the polarity (positive or negative) of the voltage across the cells. Alternatively, the current sensor 64 may be a magnetic sensor.

[0071] The voltage sensor 65 is connected in parallel to each storage cell 2. The voltage sensor 65 is connected to both ends of each storage cell 2, and measures the terminal voltage of each storage cell 2 in time series. The control unit 31 acquires data on the voltage of each storage cell 2 measured by the voltage sensor 65 and the total voltage of the storage device 1 via the input / output unit 33.

[0072] A display device such as a liquid crystal display device may be connected to the input / output unit 33. The control unit 31 may output the estimation result of the usable SOC range via the input / output unit 33 and display it on the display device.

[0073] The communication unit 34 includes a communication interface that realizes communication with an external device. The control unit 31 transmits and receives various data, including the estimation result of the usable SOC range, to and from the external device via the communication unit 34. The external device that is communicatively connected via the communication unit 34 may be the vehicle ECU 71.

[0074] The following describes a method for estimating the usable SOC range by the estimation device 3. The method for estimating the usable SOC range will be described below using an example in which an usable SOC range that satisfies a predetermined discharge capacity is obtained based on information about a discharge pattern.

[0075] The power storage device 1 mounted on a mobile object is required to exhibit a predetermined discharge capacity for the electrical load connected thereto whenever the mobile object is started (when a discharge is requested). The 12V battery mounted on a vehicle is required to maintain a voltage equal to or higher than a threshold value (e.g., 9V) even when discharging for a predetermined time (t seconds) at a discharge current specified by a higher-level device according to the power consumption of the on-board electrical load 72.

[0076] The discharge capacity of the energy storage device 1 is not always constant, but changes depending on the operating conditions of the energy storage device 1, such as the temperature, the SOH of the energy storage cells 2, the current, etc. The estimation device 3 determines a usable SOC range according to the operating conditions by simulating the voltage behavior of the energy storage device 1 when discharging according to a predetermined discharge pattern using a storage element model. The estimation device 3 sequentially estimates the voltage behavior of the energy storage device 1 by changing the SOC given to the storage element model, and determines whether or not discharging according to the discharge pattern is possible based on the estimated voltage behavior, thereby obtaining an optimal value of the usable SOC range that satisfies the predetermined discharge capacity.

[0077] Fig. 4 is a circuit diagram showing an example of a storage element model. The storage element model shown in Fig. 4 is an equivalent circuit model that combines a voltage source for the storage cell 2 and circuit elements such as a resistor and a capacitor to simulate the charge and discharge behavior of the storage cell 2. The equivalent circuit model includes, for example, a constant voltage source, a DC resistor, and an RC parallel circuit connected in series between the positive terminal and the negative terminal. Fig. 4 shows an equivalent circuit model in which two RC parallel circuits, a first RC parallel circuit and a second RC parallel circuit, are connected in series, but the number of RC parallel circuits is not limited to two.

[0078] The constant voltage source is a voltage source that outputs a DC voltage. The voltage output by the constant voltage source is the open circuit voltage (OCV) of the storage cell 2 and is denoted as Vo(t). The open circuit voltage Vo(t) is given as a function of the SOC, temperature, SOH, etc. of the storage cell 2.

[0079] The DC resistor is used to describe the DC resistance component (DC impedance) of the storage cell 2 and includes a resistance element R0. The value of the resistance element R0 is given as a value that changes depending on the SOC, temperature, SOH, etc. The value of the resistance element R0 may also be given as a value that changes depending on the current flow. Once the value of the resistance element R0 is determined, it is possible to calculate the voltage generated in the DC resistor when a current I(t) flows through the equivalent circuit model. The voltage generated in the DC resistor is defined as the DC resistance voltage Vz0(t).

[0080] The two RC parallel circuits are circuit elements for describing the transient polarization characteristics of the energy storage cell 2. The first RC parallel circuit is composed of a resistive element R1 and a capacitive element C1 connected in parallel. The second RC parallel circuit is composed of a resistive element R2 and a capacitive element C2 connected in parallel. The values ​​of the resistive elements R1 and R2 and the capacitive elements C1 and C2 are given as values ​​that vary depending on the current flow, SOC, temperature, etc. The resistive elements R1 and R2 and the capacitive elements C1 and C2 determine the impedances of the first RC parallel circuit and the second RC parallel circuit. Once the impedances of the first RC parallel circuit and the second RC parallel circuit are determined, it is possible to calculate the voltages (polarization voltages) generated in the first RC parallel circuit and the second RC parallel circuit when a current I(t) flows through the equivalent circuit model. The polarization voltage is the sum of the polarization voltage Vz1(t) generated in the first RC parallel circuit and the polarization voltage Vz2(t) generated in the second RC parallel circuit.

[0081] Here, the time constant of the first RC parallel circuit is τ1, and the time constant of the second RC parallel circuit is τ2. The time constant τ1 is determined by multiplying the resistance value of the resistive element R1 and the capacitance value of the capacitive element C1 in the first RC parallel circuit. The time constant τ1 is reflected in the time change of the polarization voltage Vz1(t) generated in the first RC parallel circuit. Similarly, the time constant τ2 is determined by multiplying the resistance value of the resistive element R2 and the capacitance value of the capacitive element C2 in the second RC parallel circuit. The time constant τ2 is reflected in the time change of the polarization voltage Vz2(t) generated in the second RC parallel circuit. By varying the time constants τ1 and τ2, various phenomena occurring within the energy storage cell 2 can be represented.

[0082] In the above-described equivalent circuit model, the terminal voltage V(t) between the positive and negative terminals of the storage cell 2 after a time t has elapsed can be expressed by the following equation (1) using the DC resistance voltage Vz0(t), the polarization voltage Vz1(t), the polarization voltage Vz2(t), and the open-circuit voltage Vo(t).

[0083] V(t)=Vo(t)+Vz0(t)+Vz1(t)+Vz2(t)...(1)

[0084] The estimated voltage of the storage device 1 is determined by calculating the sum of the terminal voltages V(t) of the storage cells 2 obtained by the formula (1).

[0085] The values ​​of the elements R0, R1, R2, C1, and C2 constituting the equivalent circuit model of the energy storage cell 2 are set in advance, for example, based on the results of actual measurements and taking into consideration the relationships between current, voltage, SOC, SOH, temperature, and the like. The estimation device 3 stores a parameter table in the storage unit 32 as estimation data 322, which stores the values ​​of the elements in association with temperature, SOC, SOH, current flow, and the like. The estimation data 322 stored in the estimation device 3 may also include a profile (SOC-OCV characteristics) showing the relationship between SOC and OCV in association with temperature and SOH. Hereinafter, the OCV and the values ​​of the elements R0, R1, R2, C1, and C2 in the equivalent circuit model will also be referred to as circuit parameters.

[0086] The estimation device 3 estimates the estimated voltage when discharging according to a predetermined discharge pattern using an equivalent circuit model, and determines whether or not current can be passed based on the estimation result. Information about the discharge pattern is specified, for example, by a higher-level device. The information about the discharge pattern may include a current value, a current passing time, and an operating voltage range related to the discharge pattern. The operating voltage range is the lower limit voltage of the storage device 1 during discharging, and is the upper limit voltage of the storage device 1 during charging.

[0087] In determining whether or not current can be passed, it is determined whether or not the estimated voltage of the storage device 1 due to discharge in a predetermined discharge pattern is equal to or greater than a preset lower limit voltage value. If the estimated voltage value after discharge in the discharge pattern is equal to or greater than the lower limit voltage value, it can be determined that the discharge capacity after current is met and discharge is possible. If the estimated voltage value after discharge is less than the lower limit voltage value, it can be determined that the discharge capacity after current is not met and discharge is not possible. Whether or not current can be passed corresponds to whether or not a predetermined charge capacity or discharge capacity is met.

[0088] The estimation device 3 uses a certain starting SOC value as an initial value and searches for an optimum value for the lower limit of the SOC that defines the usable SOC range.

[0089] 5 is a flowchart showing an example of a processing procedure executed by the estimation device 3. The processing in the flowchart below is executed by the control unit 31 in accordance with a computer program 3P stored in the storage unit 32 of the estimation device 3.

[0090] The control unit 31 of the estimation device 3 functions as an acquisition unit to acquire measurement data including the current temperature, current, and voltage of the power storage device 1 (step S11). The control unit 31 acquires the current SOH of the power storage device 1, which is calculated based on the acquired measurement data (step S12).

[0091] The control unit 31 determines the starting SOC value (step S13). The control unit 31 may store in advance in the storage unit 32 a correspondence relationship between the SOH and / or temperature and the starting SOC value to be used, and may specify the starting SOC corresponding to the current SOH and / or temperature of the power storage device 1 based on the correspondence relationship. The correspondence relationship between the SOH and / or temperature and the starting SOC value to be used can be set based on, for example, actual measurement results. Alternatively, the starting SOC value may be selected arbitrarily.

[0092] The control unit 31 derives circuit parameters in the equivalent circuit model based on the determined starting SOC value, the current temperature and SOH, and the information on the discharge pattern provided from the higher-level device (step S14). The control unit 31 obtains the circuit parameters so as to correspond to the information on the SOC value, temperature, SOH, and discharge pattern as the simulation conditions, for example, by referring to the parameter table and SOC-OCV characteristics of the estimation data 322.

[0093] The control unit 31 applies the derived circuit parameters and predicts the voltage behavior of the storage device 1 when discharging according to the discharge pattern using an equivalent circuit model, thereby determining whether discharging according to the discharge pattern is possible at the starting SOC value (step S15). The control unit 31 estimates the estimated voltage of the storage device 1 by substituting the derived circuit parameters into the above formula (1), and determines whether discharging is possible by determining whether the estimated voltage is equal to or greater than a preset lower limit voltage value.

[0094] If it is determined that discharge is possible at the starting SOC value (YES in S15), the control unit 31 reduces the SOC value by a predetermined amount from the starting SOC value (step S16). The amount of reduction in the SOC value may be set in advance. The control unit 31 derives new circuit parameters in the equivalent circuit model based on the reduced SOC value, the current temperature and SOH, and the discharge pattern information so as to correspond to the new simulation conditions (step S17).

[0095] The control unit 31 applies the derived new circuit parameters and predicts the voltage behavior of the storage device 1 when discharging according to the discharge pattern using an equivalent circuit model, thereby determining whether discharging according to the discharge pattern is impossible with the reduced SOC value (step S18).

[0096] If it is determined that discharging is not impossible with the reduced SOC value, i.e., that discharging is possible (S18: NO), the control unit 31 returns the processing to step S16, further reduces the SOC value by a predetermined amount from the reduced SOC value, and repeats the same processing.

[0097] If it is determined that discharging is not possible at the reduced SOC value (S18: YES), the control unit 31 estimates the SOC value immediately before it is determined that discharging is not possible as the lower limit value of the SOC (step S19), and proceeds to step S24.

[0098] If it is determined that discharge is not possible at the starting SOC value (NO in S15), the control unit 31 increases the SOC value by a predetermined amount from the starting SOC value (step S20). The increase in the SOC value may be preset. The control unit 31 derives new circuit parameters in the equivalent circuit model based on the increased SOC value, the current temperature and SOH, and the discharge pattern information so as to correspond to the new simulation conditions (step S21).

[0099] The control unit 31 applies the derived new circuit parameters and predicts the voltage behavior of the storage device 1 when discharging according to the discharge pattern using an equivalent circuit model, thereby determining whether discharging according to the discharge pattern is possible with the increased SOC value (step S22).

[0100] If it is determined that discharge is not possible with the increased SOC value, i.e., that discharge is not possible (S22: NO), the control unit 31 returns the process to step S20, further increases the SOC value by a predetermined amount from the increased SOC value, and repeats the same process.

[0101] If it is determined that discharge is possible at the increased SOC value (S22: YES), the control unit 31 estimates the SOC value at which it is determined that discharge is possible as the lower limit SOC value (step S23), and the process proceeds to step S24. The control unit 31 may perform the processes from step S13 to step S24 by functioning as an estimation unit.

[0102] The control unit 31 outputs the usable SOC range indicated by the estimated SOC lower limit value and a predetermined SOC upper limit value (e.g., SOC 80%) to an external device (e.g., vehicle ECU 71) (step S24), and ends the series of processes.

[0103] In the above, an example has been described in which only the lower limit of the SOC value that satisfies a predetermined discharge capacity based on the discharge pattern is dynamically calculated as the usable SOC range, but the upper limit of the SOC value can also be calculated in a similar manner. The estimation device 3 may replace the discharge pattern in the above description with a charge pattern and perform similar processing for the charge pattern to calculate the upper limit of the SOC value that satisfies the predetermined charge capacity based on the charge pattern. The usable SOC range may be represented by a lower limit of the SOC value that satisfies the predetermined discharge capacity and an upper limit of the SOC value that satisfies the predetermined charge capacity.

[0104] In step S24, the estimation device 3 may derive a recommended SOC range based on the lower and upper limits of the SOC and output the derived recommended SOC range to an external device. The estimation device 3 may derive the recommended SOC range by, for example, adding or subtracting an SOC corresponding to a predetermined required power to or from the calculated lower and / or upper limits of the SOC, thereby setting the new lower and / or upper limits as the recommended SOC range. The estimation device 3 may set the lower limit of the recommended SOC range to a value that is greater than the estimated lower limit of the SOC by an SOC corresponding to the required power during parking. The estimation device 3 may derive the recommended SOC range as a partial range of the estimated usable SOC range, limited to a specific SOC range. For example, setting the recommended SOC range to an SOC of 50% or less can encourage use of the power storage device 1 in a low SOC range.

[0105] The estimation device, estimation method, and estimation program may be applied to applications other than vehicles, and may be applied to flying bodies such as aircraft, flying vehicles, and HAPS (High Altitude Platform Stations), as well as to ships and submarines. The power storage device 1 may be a high-voltage battery.

[0106] According to this embodiment, it is possible to estimate an SOC suitable for use in consideration of the charging capacity or discharging capacity according to the operating status of the power storage device 1 .

[0107] In the second embodiment, when the estimated lower limit value of the SOC is equal to or greater than a threshold value, a temperature that satisfies a predetermined discharge capacity is estimated. The following mainly describes differences from the first embodiment, and the same reference numerals are used to designate components that are common to the first embodiment, and detailed descriptions thereof will be omitted.

[0108] In the process of estimating the lower limit value of SOC described in the first embodiment, it may be determined that discharging is not possible even if the SOC value, which is a simulation condition, is increased to 100% SOC, depending on the current temperature environment of the storage device 1. In the second embodiment, in such a case, it is estimated to what degree the temperature of the storage device 1 needs to be increased to enable discharging according to a predetermined discharge pattern.

[0109] 6 is a flowchart showing an example of a processing procedure executed by the estimation device 3 of the second embodiment. The control unit 31 of the estimation device 3 starts the following processing after executing, for example, step S20 of the first embodiment.

[0110] The control unit 31 of the estimation device 3 determines whether the increased SOC value has reached 100% (step S31). If it is determined that the increased SOC value has not reached 100% (S31: NO), the control unit 31 ends the process.

[0111] If it is determined that the increased SOC value has reached 100% (S31: YES), the control unit 31 derives circuit parameters of the equivalent circuit model to correspond to the above simulation conditions based on the current temperature, the current SOH, the set SOC value (e.g., SOC 100%), and information on the discharge pattern provided from the higher-level device (step S32).

[0112] The control unit 31 applies the derived circuit parameters and predicts the voltage behavior of the storage device 1 when discharging according to the discharge pattern using an equivalent circuit model, thereby determining whether discharging according to the discharge pattern is possible at the current temperature (step S33).

[0113] If it is determined that discharge is possible at the current temperature (S33: YES), the control unit 31 ends the process.

[0114] If it is determined that discharge is not possible at the current temperature, i.e., that discharge is not possible (S33: NO), the control unit 31 increases the temperature value of the power storage device 1 by a predetermined amount from the current temperature (step S34). The amount of temperature increase may be set in advance. The control unit 31 derives new circuit parameters in the equivalent circuit model to correspond to the new simulation conditions based on the increased temperature, the current set values ​​of SOH and SOC, and information on the discharge pattern (step S35).

[0115] The control unit 31 applies the derived new circuit parameters and predicts the voltage behavior of the storage device 1 when discharging according to the discharge pattern using an equivalent circuit model, thereby determining whether discharging according to the discharge pattern is possible at the increased temperature (step S36).

[0116] If it is determined that discharge is not possible at the increased temperature, i.e., that discharge is not possible (S36: NO), the control unit 31 returns the process to step S34, further increases the temperature value by a predetermined amount from the increased temperature, and repeats the same process.

[0117] If it is determined that discharge is possible at the increased temperature (YES in S36), the control unit 31 estimates the temperature of the power storage device 1 when it is determined that discharge is possible as the minimum temperature (step S37). The control unit 31 outputs the estimated minimum temperature to an external device (e.g., the vehicle ECU 71) (step S38), and ends the series of processes.

[0118] The external device executes temperature increase control, such as driving a heater in the vehicle, based on the minimum temperature received from the estimation device 3.

[0119] In step S31, the estimation device 3 may determine whether the increased SOC value is equal to or greater than a preset threshold value. That is, the SOC that serves as the starting condition for the process in FIG. 6 is not limited to 100%.

[0120] In the above, the circuit parameters are derived based on the set value of the SOC as a simulation condition to determine whether or not to energize. Alternatively, the circuit parameters may be derived based on the current SOC of the power storage device 1.

[0121] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the scope of the claims and equivalents thereto. The sequences shown in each embodiment are not limited, and within the scope of no contradiction, each processing step may be executed in a different order, or multiple processes may be executed in parallel. The entity that performs each process is not limited, and within the scope of no contradiction, the process of each device may be executed by another device.

[0122] The matters described in each embodiment can be combined with each other. Furthermore, the independent claims and dependent claims described in the claims can be combined with each other in any and all combinations, regardless of the reference format. Furthermore, the claims use a format in which a claim references two or more other claims (multiple claim format), but this is not limited to this. A multiple claim (multi-multi claim) that references at least one other multiple claim may also be used.

[0123] REFERENCE SIGNS LIST 1 Energy storage device (energy storage element) 2 Energy storage cell 3 Estimation device 31 Control unit 32 Storage unit 33 Input / output unit 34 Communication unit 321 Estimation program 322 Estimation data 3A Recording medium

Claims

1. An estimation device comprising: an acquisition unit that acquires a state of a storage element; and an estimation unit that estimates an SOC of the storage element that satisfies a specified charging capacity or discharging capacity based on the acquired state of the storage element and information on a current pattern provided to a model of the storage element.

2. The estimation device according to claim 1, wherein the state of the storage element includes at least one of a deterioration state, a temperature, and a polarization state of the storage element at the time of estimation.

3. The estimation device according to claim 1 or 2, wherein the SOC of the storage element includes a lower limit value of the SOC of the storage element that satisfies a predetermined discharge capacity estimated based on information of a discharge pattern provided to the model.

4. The estimation device according to claim 1 or 2, wherein the SOC of the storage element includes an upper limit value of the SOC of the storage element that satisfies a predetermined charging capacity estimated based on information of a charging pattern provided to the model.

5. The estimation device according to claim 1 or claim 2, wherein the estimation unit searches for an upper or lower limit value of the SOC of the storage element by sequentially increasing or decreasing an SOC value from a starting SOC, and determining whether or not the voltage behavior of the storage element predicted by the model satisfies the specified charging or discharging capacity based on the SOC value of the storage element after the increase or decrease, the state of the storage element, and information on the current pattern.

6. The estimation device according to claim 1 or 2, wherein the estimation unit derives a recommended SOC based on the estimated SOC of the storage element.

7. The estimation device according to claim 1 or 2, further comprising a temperature estimation unit that estimates a temperature of the storage element that satisfies a predetermined discharge capacity when the estimated lower limit value of the SOC of the storage element is equal to or higher than a threshold value.

8. The estimation device according to claim 1 or 2, further comprising an output unit that outputs the estimated SOC of the storage element to an external device.

9. The estimation device according to claim 1 or 2, further comprising an output unit that outputs the estimated SOC of the storage element to an external device that controls charging and discharging of the storage element.

10. A power storage device comprising a power storage element and the estimation device according to claim 1 or 2.

11. An estimation method comprising: acquiring a state of a storage element; and estimating an SOC of the storage element that satisfies a predetermined charging or discharging capacity based on the acquired state of the storage element and information on a current pattern provided to a model of the storage element.

12. An estimation program for causing a computer to execute a process of acquiring the state of a storage element, and estimating the SOC of the storage element that satisfies a predetermined charging capacity or discharging capacity based on the acquired state of the storage element and information on a current pattern given to a model of the storage element.

Images