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

Abstract

To provide a technology capable of estimating an SOC of a power storage element suitable for use in consideration of charge capacity or discharge capacity of the power storage element.SOLUTION: An estimation device includes: an acquisition unit that acquires a state of a power storage element; and an estimation unit that estimates an SOC of the power storage element satisfying predetermined charge capacity or discharge capacity on the basis of the acquired state of the storage element and information on a conduction pattern given to a model of the power storage element.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Secondary batteries are widely used as power sources for vehicles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and other mobile objects. Technology relating to a charging / discharging device for controlling charging / discharging of secondary batteries has been disclosed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-11531 A Summary of the Invention [Problem to be solved by the invention]

[0004] A charge / discharge device generally controls charging and 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 technique capable of estimating the SOC of an energy storage element suitable for use in consideration of the charging or discharging capacity of the energy storage element. [Means for solving the problem]

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

[0007] According to the present disclosure, it is possible to estimate the SOC of an energy storage element suitable for use by taking into account the charging or discharging capacity of the energy storage element. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a perspective view illustrating a configuration example of a power storage device. [Diagram 2] FIG. [Diagram 3] 1 is a block diagram showing a configuration example of a power storage device including an estimation device; [Figure 4] FIG. 4 is a circuit diagram showing an example of a storage element model. [Diagram 5] 13 is a flowchart illustrating an example of a processing procedure executed by the estimation device. [Figure 6] 10 is a flowchart illustrating an example of a processing procedure executed by the estimation device of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (1) An estimation device according to one embodiment of the present disclosure includes an acquisition unit that acquires a state of a storage element, and an estimation unit that estimates a 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 power storage cell or a power storage unit having a plurality of power storage cells. The "energization pattern information" may include a current value representing the energization pattern and an energization time of the current value. "SOC of a storage element that satisfies a specified charging or discharging capacity" refers to the SOC of a storage element that can be charged or discharged in a specific current pattern without deviating from a specified voltage range, for example, an SOC range defined by an upper and lower limit value of the SOC. Hereinafter, the SOC of a storage element that satisfies a specified charging or discharging capacity is also referred to as a usable SOC range. The usable SOC range refers to an SOC that is suitable for use of the storage element. The estimation unit may use a model of the energy storage element to predict a voltage behavior of the energy storage element when a current is applied in the current application pattern, and estimate an SOC value of the energy storage element based on the predicted voltage behavior of the energy storage element. The estimation unit may identify an SOC value of the energy storage element that can satisfy the predetermined charging capacity or discharging capacity by determining whether the voltage behavior of the energy storage element predicted by the model satisfies the predetermined charging capacity or discharging capacity.

[0011] According to the estimation device described in (1) above, the usable SOC range can be estimated taking into consideration the charging or discharging capacity (charging and discharging capacity) of the storage element. The usable SOC range can be dynamically estimated according to the required charging and discharging capacity, i.e., the expected current pattern. Compared to the case where a fixed usable SOC range is preset, the usable SOC range of the storage element can be flexibly adjusted, increasing the degree of freedom of the SOC.

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

[0013] Conventionally, a charge / discharge control device uses a preset fixed SOC range (for example, SOC 70% to 80%) as the usable SOC range for performing charge / discharge control. In a power storage device including a power storage element, the current SOC of the power storage element is constantly monitored and notified to the charge / discharge control device. The charge / discharge control device performs the above-mentioned charge / discharge control so that the current SOC of the power storage element notified from 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 the power supply performance can be reliably exhibited regardless of the usage state of the power storage element. For this reason, the performance of the power storage element is not fully exhibited. During driving, even though a wider SOC range is actually usable, charge / discharge is controlled within the narrow SOC range. During parking, recharging is performed under a high SOC even though charging is not actually required yet.

[0014] While the above-mentioned charge and discharge control of the storage element is performed, in recent years, a function for estimating the power supply performance (SOF: State Of Function) of the storage element is required to realize an automatic driving function and a safety function in a vehicle. In the storage device, the possibility of charging or discharging (current passing possibility) according to a predetermined current passing pattern is judged at a predetermined interval, and the judgment result is notified to the vehicle. In this case, only the possibility of current passing is judged, and it is not considered what percentage above or below the SOC is necessary for current passing in the actual state of the storage element. In other words, the charge and discharge control of the storage element and the estimation of the SOF are processed 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, the SOC range in which charge / discharge control should be performed can be set broadly. 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 cost and fuel efficiency when 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 functions from being restricted after the vehicle is started due to recharging being too slow, and to prevent the vehicle from being frequently started while parked due to recharging being too fast.

[0016] (2) In the estimation device described above in (1), 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 a time of estimation.

[0017] The "deterioration state" may be the capacity maintenance rate (SOH: State of health) of the storage element, the full charge capacity, or the internal resistance increase rate. The "polarization state" may be the degree of deviation between the theoretical electromotive force of the 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 estimation time, which greatly affect the voltage behavior of the storage element. The estimation time means the present, for example, when the 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 of a discharge pattern provided to the model.

[0020] According to the estimation device described in (3) above, the lower limit of the SOC at which the battery can be discharged in a predetermined discharge pattern can be estimated, so that the discharge control can be optimized. 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 of a charging pattern provided to the model.

[0022] According to the estimation device described in (4) above, since it is possible to estimate the upper limit of the SOC at which charging can be accepted in a predetermined charging pattern, it is possible to optimize charging control. The upper limit of the SOC may be the highest SOC value at which charging can be accepted 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 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 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 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 by the equivalent circuit model including parameters having 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 starting SOC, it is possible to efficiently and accurately search for an SOC value that satisfies a predetermined charge / discharge capacity, thereby reducing the calculation load and calculation time in 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 part 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 among 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 band, and it is expected to have an effect of suppressing deterioration of the storage element.

[0027] (7) In the estimation device described in any one of (1) to (6) above, a temperature estimation unit may be provided 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 greater than a threshold value.

[0028] If the temperature of the storage element is too low, even if the SOC is charged to a predetermined value (e.g., SOC 100%), it may be determined that power cannot be supplied according to a predetermined discharge pattern. In such a case, the estimation device described in (7) above can estimate the temperature of the storage element that can supply power, and therefore can 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 performs charge / discharge control 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 control the charge / discharge of the storage element in accordance with the estimation result.

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

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

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

[0037] (First embodiment) Fig. 1 is a perspective view showing a configuration example of the energy storage device 1, and Fig. 2 is an exploded perspective view of the energy storage device 1. In the following, the configuration example of the energy 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, for example, a battery that is suitably mounted in 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. The estimation device 3 estimates the SOC (usable SOC range) of the storage device 1 that satisfies a predetermined charging capacity or discharging capacity based on the acquired measurement data. The usable SOC range of the storage device 1 is, for example, an SOC range defined by an upper limit value and a lower limit value 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 by 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 by fasteners such as screws, an adhesive, welding, or the like, with the energy storage cell 2, the estimating device 3, and the busbar unit 4 housed therein. A pair of external terminals 13A, 13B having 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. An electrode assembly, an electrolyte, and the like (not shown) are accommodated inside the case 21.

[0045] The electrode body is constructed by stacking a sheet-shaped positive electrode and a sheet-shaped negative electrode with two sheet-shaped separators between them and winding them (vertically or horizontally). The separator is made of a porous resin film. As the porous resin film, a porous resin film made of a resin such as polyethylene (PE) or polypropylene (PP) can be used.

[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, an aluminum alloy, or the like. The positive electrode active material layer includes a positive electrode active material. As the positive electrode active material used in the positive electrode active material layer, a material capable of absorbing and releasing lithium ions can be used. As the positive electrode active material, for example, LiFePO4 can be used. The positive electrode active material layer may further include a conductive assistant, a binder, and the like.

[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 may be the same as that used in conventional lithium ion secondary batteries. For example, an electrolyte containing a supporting salt in an organic solvent may be used. For example, aprotic solvents such as carbonates, esters, and ethers are used as the organic solvent. For example, lithium salts such as LiPF6, LiBF4, and LiClO4 are preferably used as the supporting salt. The electrolyte may contain various additives such as a gas generating agent, a film forming agent, a dispersing agent, and a thickening agent.

[0049] In the embodiment, the storage cell 2 is a battery cell based on a lithium ion secondary battery. Alternatively, the 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 power storage cell 2 is a rectangular battery cell equipped with a wound electrode assembly. Alternatively, the power storage cell 2 may be a cylindrical battery cell or a laminated (pouch) battery cell, or may be a battery cell equipped with a laminated 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 are also 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 orientations of the positive terminals 22 and negative terminals 23 of adjacent storage cells 2 are opposite to each other.

[0053] The estimator 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 bottom surface of the estimator 3 by a fastener 43 such as a screw. The energy storage cell 2 and the estimator 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 having 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 energy storage cell 2 to the negative terminal 23 of the other energy storage cell 2 in 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. An interruption 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 interruption circuit 62, the temperature sensor 63, the current sensor 64, and the voltage sensor 65 are mounted on the circuit board 61.

[0057] The interrupter circuit 62 is a circuit for connecting or interrupting a conductive path between the bus bar 41 connected to the positive terminal 22 of the fourth storage cell 2D and a bus bar 66 connected to the external terminal 13B. The interrupter circuit 62 is formed of a semiconductor switch such as a metal oxide semiconductor field effect transistor (MOSFET). By switching the interrupter circuit 62 from an on state to an off state, it is possible to interrupt the outflow of current from the storage cell 2 to the outside and the inflow of current from the outside to the storage cell 2. Alternatively, the interrupter circuit 62 may be formed of 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 electricity storage device 1. In FIG. 2, the temperature sensor 63 is disposed at a position sufficiently separated from the energized heating element (for example, the interrupter circuit 62, the bus bars 41, 66, the fastener 48, or the like) on the circuit board 61. The temperature data measured by the temperature sensor 63 indicates the ambient temperature of the electricity storage device 1 (the ambient temperature of the electricity storage cell 2). The electricity storage element may further include a temperature sensor 63 disposed near the energized heating element on the circuit board 61 and measuring the temperature of the energized heating element on the circuit board 61. In this case, the temperature of the electricity storage device 1 may be identified based on the ambient temperature of the electricity storage device 1 and the temperature of the energized heating element on the circuit board 61.

[0059] 3 is a block diagram showing a configuration example of an electricity storage device 1 including an estimation device 3. The electricity storage device 1 is connected to a vehicle ECU (Electronic Control Unit) 71, an electric load 72 such as an electric component, 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. While 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 enable the high-voltage system to start. While the vehicle is parked, the power storage device 1 discharges to the vehicle ECU 71 and the electric 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 an example of an external device (charge and 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 by using a plurality of computers, may be realized by a plurality of virtual machines provided in one server, or may be realized by using a cloud server.

[0064] The control unit 31 is an arithmetic circuit including a central processing unit (CPU), a graphics processing unit (GPU), a read only memory (ROM), a random access memory (RAM), 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 include functions such as a timer that measures the elapsed time from when an instruction to start measurement is given to 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 energy storage device 1, and estimation data 322 as data necessary for executing the estimation program 321. The estimation data 322 includes an energy storage element model used in the simulation. The energy storage element model is described by configuration information indicating a circuit configuration, values ​​of each element constituting the energy storage element model, and the like. The storage unit 32 stores configuration information indicating the circuit configuration of the energy storage element model, values ​​of each element constituting the energy storage element model, and the like.

[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 by 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 an interrupter circuit 62, a temperature sensor 63, a current sensor 64, a voltage sensor 65, and the like.

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

[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 / 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 cause the display device to display it.

[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 through 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 following describes the method for estimating the usable SOC range by taking as an example a case where an usable SOC range that satisfies a predetermined discharge capacity based on information on a discharge pattern.

[0075] The power storage device 1 mounted on the moving object is required to exhibit a predetermined discharge capacity for the electric load connected thereto whenever the moving object is started (when discharge is requested). The 12V battery mounted on the 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 electric 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 in 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 is possible according to the discharge pattern based on the estimated result of the 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, which combines a voltage source of the storage cell 2 and circuit elements such as a resistor and a capacitor to simulate the charging and discharging 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 a positive terminal and a 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 RC parallel circuit is not limited to two stages.

[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 for describing 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 according to the SOC, temperature, SOH, etc. The value of the resistance element R0 may be given as a value that changes according to 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 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, R2 and the capacitive elements C1, C2 are given as values ​​that vary depending on the current flow, SOC, temperature, etc. The impedances of the first RC parallel circuit and the second RC parallel circuit are determined by the resistive elements R1, R2 and the capacitive elements C1, C2. If 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 in the first RC parallel circuit is τ1, and the time constant in the second RC parallel circuit is τ2. The time constant τ1 is determined as a value obtained by multiplying the resistance value of the resistive element R1 and the capacitance value of the capacitive element C1 that constitute 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 as a value obtained by multiplying the resistance value of the resistive element R2 and the capacitance value of the capacitive element C2 that constitute 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 making the time constants τ1 and τ2 different, various phenomena that occur in the storage cell 2 can be expressed.

[0082] In the above 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 energy storage device 1 is found by calculating the sum of the terminal voltages V(t) of the energy 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 storage cell 2 are set in advance, for example, based on the results of actual measurement, taking into consideration the relationships between current, voltage, SOC, SOH, temperature, and the like. The estimation device 3 stores a parameter table in which the values ​​of the elements are stored in association with temperature, SOC, SOH, current flow, and the like, as estimation data 322 in the storage unit 32. 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 are also referred to as circuit parameters.

[0086] The estimation device 3 estimates an estimated voltage when discharging in a predetermined discharge pattern using an equivalent circuit model, and judges whether or not current can be passed based on the estimation result. Information on the discharge pattern is specified, for example, from a higher-level device. The information on the discharge pattern may include a current value, 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 given 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 satisfied 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 satisfied 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 satisfied.

[0088] The estimation device 3 uses a certain start SOC value as an initial value and searches for an optimal 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 following flowchart 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, by functioning as an acquisition unit, acquires 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 start 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 start SOC value to be used, and may specify the start SOC according 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 start SOC value to be used can be set based on, for example, the result of actual measurement. Alternatively, the start 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 estimated 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 or not discharging according to the discharge pattern is possible at the start 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 or not discharging is possible by determining whether or not the estimated voltage is equal to or higher than a preset lower limit voltage value.

[0094] If it is determined that discharge is possible at the start SOC value (S15: YES), the control unit 31 reduces the SOC value by a predetermined amount from the start 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 the reduced SOC value does not prohibit discharge, i.e., discharge is possible (S18: NO), the control unit 31 returns the process to step S16, further reduces the SOC value by a predetermined amount from the reduced SOC value, and repeats the same process.

[0097] If it is determined that discharging is not possible with the decreased 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 of the SOC (step S19), and proceeds to step S24.

[0098] If it is determined that discharging is not possible at the start SOC value (S15: NO), the control unit 31 increases the SOC value by a predetermined amount from the start 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] When it is determined that discharge is possible with 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 of SOC (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 preset 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 on the charge pattern to calculate the upper limit of the SOC value that satisfies a predetermined charge capacity based on the charge pattern. The usable SOC range may be indicated by the lower limit of the SOC value that satisfies a predetermined discharge capacity and the upper limit of the SOC value that satisfies a predetermined charge capacity.

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

[0105] The estimation device, the estimation method, and the 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, the SOC suitable for use can be estimated in consideration of the charging capacity or discharging capacity according to the operating status of the power storage device 1.

[0107] Second embodiment 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. In the following, differences from the first embodiment are mainly described, and the same reference numerals are used for the configurations common to the first embodiment, and detailed description thereof is omitted.

[0108] In the process of estimating the lower limit 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 SOC 100%, 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 an equivalent circuit model based on the current temperature, the current SOH, the SOC setting value (e.g., SOC 100%), and the discharge pattern information provided from the upper device so as to correspond to the above simulation conditions (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., discharge is not possible (S33: NO), control unit 31 increases the temperature value of power storage device 1 from the current temperature by a predetermined amount (step S34). The amount of increase in temperature may be set in advance. Based on the increased temperature, the current SOH and SOC settings, and information on the discharge pattern, control unit 31 derives new circuit parameters in the equivalent circuit model to correspond to the new simulation conditions (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] When it is determined that discharging is possible at the increased temperature (S36: YES), the control unit 31 estimates the temperature of the power storage device 1 when it is determined that discharging 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] Based on the minimum temperature received from the estimation device 3, the external device executes temperature increase control, such as driving a heater of the vehicle.

[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 is the starting condition for the process in FIG.

[0120] In the above, the circuit parameters are derived based on the set value of the SOC as a simulation condition, and the propriety of energization is determined. 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 as 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 the scope equivalent to the claims. The sequences shown in each embodiment are not limited, and the order of each process may be changed and multiple processes may be executed in parallel, as long as there is no contradiction. The subject of each process is not limited, and the process of each device may be executed by another device, as long as there is no contradiction.

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

[0123] 1. Energy storage device (energy storage element) 2. Energy storage cell 3 Estimation device 31 Control Unit 32 Storage section 33 Input / output section 34 Communications Department 321 Estimation Program 322 Estimated Data 3A Recording Media

Claims

1. An acquisition unit for acquiring a state of the energy storage element; 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 given to a model of the storage element; An estimation device comprising:

2. 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. The estimation device according to claim 1 .

3. 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 given to the model. The estimation device according to claim 1 or 2.

4. 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 given to the model. The estimation device according to claim 1 or 2.

5. The estimation unit sequentially increases or decreases an SOC value from a starting SOC, and determines whether or not 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 pattern, thereby searching for an upper limit or lower limit value of the SOC of the storage element. The estimation device according to claim 1 or 2.

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

7. and 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 greater than a threshold value. The estimation device according to claim 1 or 2.

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

9. 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. The estimation device according to claim 1 or 2.

10. The present invention is provided with a storage element and an estimation device according to claim 1 or 2. Energy storage device.

11. Obtain the status of the storage element, Based on the acquired state of the storage element and information on a current pattern given to a model of the storage element, an SOC of the storage element that satisfies a predetermined charging capacity or discharging capacity is estimated. Estimation method.

12. Obtain the status of the storage element, Based on the acquired state of the storage element and information on a current pattern given to a model of the storage element, an SOC of the storage element that satisfies a predetermined charging capacity or discharging capacity is estimated. An estimation program for causing a computer to execute the processing.

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