Estimation method, estimation apparatus, and computer program

Abstract

This estimation method involves: acquiring measurement data including the voltage of a power storage element and the current flowing in the power storage element; estimating, on the basis of the acquired measurement data and by applying a state estimator, a parameter related to a polarization component of an equivalent circuit model including an RC parallel circuit; and estimating the voltage of a polarization component of the power storage element at a specific time point by using the estimated parameter.

Description

Estimation method, estimation device, and computer program

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

[0002] The state of a storage element is determined using an equivalent circuit model. The battery energy prediction device disclosed in Patent Document 1 calculates a predicted voltage, which is the terminal voltage of a secondary battery assuming that a required power is continuously output from the secondary battery for a specified time period based on the equivalent circuit model. The battery energy prediction device predicts the remaining energy of the secondary battery based on relationship information between the charging rate, temperature, and predicted voltage, which is obtained by inputting the current charging rate and current temperature of the secondary battery. The relationship information is corrected to match the predicted voltage calculated based on the predicted voltage.

[0003] Japanese Patent Application Laid-Open No. 2016-173281

[0004] The technique of Patent Document 1 does not improve the accuracy of predictive calculations using an equivalent circuit model.

[0005] An object of the present disclosure is to provide a technology that can improve the accuracy of calculations using an equivalent circuit model.

[0006] An estimation method according to one aspect of the present disclosure acquires measurement data including a voltage of a storage element and a current flowing through the storage element, applies a state estimator to estimate parameters related to a polarization component of an equivalent circuit model including an RC parallel circuit based on the acquired measurement data, and estimates the voltage of the polarization component of the storage element at a specific time using the estimated parameters.

[0007] According to the present disclosure, the accuracy of calculations using an equivalent circuit model can be improved.

[0008] 1 is a block diagram showing a configuration example of an estimation system; FIG. 2 is a block diagram showing a configuration example of an estimation device of a first embodiment; FIG. 3 is a circuit diagram showing a configuration example of an equivalent circuit model; FIG. 4 is a flowchart showing an example of a processing procedure executed by the estimation device; FIG. 5 is a functional block diagram of the estimation device of the first embodiment; FIG. 6 is a flowchart showing an example of a processing procedure executed by the estimation device of a second embodiment; FIG. 7 is a functional block diagram of the estimation device of the second embodiment; FIG. 8 is a diagram showing an overview of a solar power generation system;

[0009] An outline of an embodiment will be described below. (1) An estimation method according to one aspect of the present disclosure (a) acquires measurement data including a voltage of a storage element and a current flowing through the storage element, and, based on the acquired measurement data, applies a state estimator to estimate parameters related to a polarization component of an equivalent circuit model including an RC parallel circuit, and (b) estimates the voltage of the polarization component of the storage element at a specific time using the estimated parameters. Here, the "specific time" may be a future time or the present time. The "state estimator" may be a Kalman filter or other state estimators (e.g., a Lehenberger observer, a particle filter, an H∞ filter, or a sliding mode observer).

[0010] According to the estimation method described in (1) above, in step (a), a state estimator is used to sequentially estimate parameters related to the polarization components based on the measured values ​​of the storage elements, and in step (b), the temporal change in the voltage of the polarization components in the equivalent circuit model is determined (see FIG. 5 ). By using parameters updated by feeding back the current voltage values ​​acquired in step (a) in the calculation of the voltage change of the polarization components using the equivalent circuit model, any model errors can be compensated for, thereby improving the accuracy of the calculation using the equivalent circuit model.

[0011] It is expected that energy storage elements will be used continuously for periods of several decades. During this time, the energy storage elements will deteriorate over time and their usage conditions will change. Even with an equivalent circuit model constructed with high accuracy, it is difficult to guarantee accuracy over the entire usage period, and there is a high possibility that model errors will occur in response to changes in the state of the energy storage elements. In order to improve the accuracy of calculations using an equivalent circuit model, a mechanism for compensating for model errors is important. With the above configuration, calculations can be performed using an equivalent circuit model taking into account measurement data without changing the equivalent circuit model itself. Even if there is a model error, the error can be compensated for and the state of the energy storage element can be accurately estimated.

[0012] (2) In the estimation method described in (1) above, the charging capacity, discharging capacity, or capacity degradation degree of the storage element may be estimated by applying the estimated voltage of the polarization component to the equivalent circuit model.

[0013] According to the estimation method described in (2) above, it is possible to estimate the charging or discharging capacity (hereinafter also referred to as charging or discharging capacity) of a storage element, as well as the degree of capacity degradation. Estimating the charging or discharging capacity corresponds to estimating the short-term voltage characteristics or power characteristics (SOF: State Of Function) of the storage element. In recent years, a function to estimate SOF has been required, for example, to realize autonomous driving functions and safety functions in vehicles. According to the above configuration, it is possible to accurately estimate the charging or discharging capacity based on the voltage of the polarization component appropriately estimated using an equivalent circuit model. Since the measured voltage can be reflected in the estimation of the charging or discharging capacity, the reliability of the estimation of the charging or discharging capacity is improved.

[0014] (3) In the estimation method described in (1) or (2) above, the parameter may be a parameter representing a voltage of a polarization component in the equivalent circuit model.

[0015] According to the estimation method described in (3) above, parameters that are difficult to measure can be estimated by a state estimator such as a Kalman filter. For example, by applying a Kalman filter to estimate the voltage of the polarization component and measuring other parameters included in the differential equation in advance through experiments or the like, the calculation load when estimating the voltage of the polarization component of the storage element can be reduced and immediacy can be improved.

[0016] (4) In the estimation method described in any one of (1) to (3) above, the storage element may include a plurality of modules each having a plurality of storage cells connected in series, the modules being connected in parallel, and the voltage of the polarization component may be calculated for a portion (representative) of the storage cells in each module.

[0017] According to the estimation method described in (4) above, the calculation cost can be reduced compared to when calculations are performed for each cell. In a system including a plurality of energy storage cells 20, an increase in the amount of calculations corresponding to an increase in the number of cells can be suppressed. The system dependency of the amount of calculations can be reduced, and versatility can be improved.

[0018] (5) In the estimation method described in (4) above, the measurement data may be acquired including the highest or lowest voltage among the voltages of each storage cell in each module and the lowest temperature among the temperatures related to each storage cell, and the voltage of the polarization component may be calculated for one of the storage cells in each module based on the acquired measurement data.

[0019] According to the estimation method described in (5) above, the measurement value for each module is selected so that the estimated voltage value leans toward the safe side, thereby further improving the reliability of the estimation result.

[0020] (6) An estimation device according to an aspect of the present disclosure includes an acquisition unit that acquires measurement data including a voltage of an energy storage element and a current flowing through the energy storage element, a first estimation unit that applies a state estimator to estimate parameters related to a polarization component of an equivalent circuit model including an RC parallel circuit based on the acquired measurement data, and a second estimation unit that estimates a voltage of the polarization component of the energy storage element at a specific time using the estimated parameters. (7) A computer program according to an aspect of the present disclosure causes a computer to execute processes of acquiring measurement data including a voltage of an energy storage element and a current flowing through the energy storage element, estimating parameters related to a polarization component of an equivalent circuit model including an RC parallel circuit based on the acquired measurement data using a state estimator, and estimating a voltage of the polarization component of the energy storage element at a specific time using the estimated parameters.

[0021] The following embodiments will be described later. (8) A charge / discharge system comprising: a power storage element; the estimation device according to (6) above; and a charging device that receives information based on an estimation result by the estimation device. (9) The charge / discharge system according to (8) above, comprising: a power conditioner that charges and discharges the power storage element as the charging device. (10) The charge / discharge system according to (9) above, comprising: a renewable energy power generation device connected to the power conditioner. (11) A power storage device comprising: a power storage element; and the estimation device according to (6) above.

[0022] The present disclosure will be specifically described with reference to the drawings showing embodiments thereof.

[0023] First Embodiment Fig. 1 is a block diagram showing an example of the configuration of an estimation system. The estimation system of this embodiment is applied to vehicles such as electric vehicles (EVs) and hybrid electric vehicles (HEVs). The estimation system includes an estimation device 1 and a power storage device 2.

[0024] The estimation device 1 is, for example, a battery management system (BMS) and is configured as a circuit board unit on which a current sensor 41, a voltage sensor 42, a temperature sensor 43, etc., which will be described later, are mounted. The estimation device 1 estimates the charge / discharge capacity of the power storage device 2 based on measurement data of the power storage device 2.

[0025] The power storage device 2 includes a plurality of rechargeable power storage cells 20, such as secondary batteries, such as lead-acid batteries or lithium-ion batteries, or capacitors. The power storage device 2 of this embodiment is configured by connecting a plurality of modules (or banks) 21, each of which has a plurality of power storage cells 20 connected in series, in parallel. The power storage device 2 is an example of a power storage element. Alternatively, the number of modules (or banks) 21 of the power storage device 2 may be one. The power storage element may be a single power storage cell 20.

[0026] A load 3 is connected to terminals 2a and 2b of the power storage device 2. The power storage device 2 supplies DC power to the load 3 connected between the terminals 2a and 2b. A charging device 30 is also connected to the terminals 2a and 2b of the power storage device 2. The power storage device 2 stores power by receiving DC power from the charging device 30 connected between the terminals 2a and 2b. The charging device 30 includes a charging circuit 30b and a control unit 30a that controls the charging circuit 30b. The control unit 30a includes a CPU, a memory, an input / output interface, a communication interface (none of which are shown), etc. The control unit 30a controls the magnitude of the charging current via the charging circuit 30b based on a current command value or a current limit value received from the estimation device 1.

[0027] The power storage device 2 includes a plurality of current sensors 41, a plurality of voltage sensors 42, and a plurality of temperature sensors 43. For example, one current sensor 41, one voltage sensor 42, and one temperature sensor 43 are provided for each module 21. The voltage sensor 42 and / or the temperature sensor 43 may be provided for each power storage cell 20.

[0028] Each current sensor 41 is connected in series to the module 21 (each storage cell 20) and measures the current flowing through the module 21 (each storage cell 20). Each voltage sensor 42 is connected to both ends of each storage cell 20 and measures the terminal voltage of each storage cell 20. Each temperature sensor 43 is provided near the module 21 (each storage cell 20) and detects the temperature of the module 21 (each storage cell 20). Each current sensor 41, each voltage sensor 42, and each temperature sensor 43 is connected to the estimation device 1 and outputs a measurement signal indicating the measurement result to the estimation device 1. In FIG. 1 , connection lines between some of the sensors and the estimation device 1 are omitted.

[0029] In the embodiment, the estimation device 1 is mounted inside the power storage device 2. Alternatively, the estimation device 1 may be installed remotely from the power storage device 2. The estimation device 1 may be a computer such as a server device, a terminal device, or a vehicle ECU that is connected to the outside of the power storage device 2. In this case, measurement data measured regarding the power storage device 2 may be transmitted to the server device or the like via communication.

[0030] 2 is a block diagram showing an example configuration of the estimation device 1. The estimation device 1 is a computer and includes a control unit 11, a storage unit 12, an input / output unit 13, and a communication unit 14. The estimation device 1 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.

[0031] The control unit 11 is an arithmetic circuit including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The CPU included in the control unit 11 executes various computer programs stored in the ROM and the storage unit 12, and controls the operation of each of the hardware components described above, thereby causing the entire device to function as the estimation device of the present disclosure. The control unit 11 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 stop measurement is given, a counter that counts numbers, and a clock that outputs date and time information.

[0032] The storage unit 12 is a non-volatile storage device such as a flash memory. The storage unit 12 stores programs and data referenced by the control unit 11. The computer programs stored in the storage unit 12 include a program 121 for estimating information related to estimation of the charge / discharge capacity of the power storage device 2. The data stored in the storage unit 12 includes equivalent circuit model information 122 used in the estimation process by the program 121. The storage unit 12 may further store measurement data of the power storage device 2.

[0033] The equivalent circuit model information 122 includes information related to an equivalent circuit model of the power storage device 2. The equivalent circuit model is a model for simulating the power storage device 2 using an electric circuit. The equivalent circuit model information 122 includes configuration information indicating the circuit configuration and parameters (circuit parameters) related to the circuit elements of the equivalent circuit model.

[0034] The computer program (computer program product) stored in the storage unit 12 may be provided by a non-transitory storage medium M on which the computer program is readably recorded. The storage medium M is a portable memory such as a CD-ROM, a USB memory, or an SD (Secure Digital) card. The control unit 11 reads the desired computer program from the storage medium M using a reading device (not shown) and stores the read computer program in the storage unit 12. Alternatively, the computer program may be provided via communications. The program 111 can be deployed to be executed on a single computer, or on multiple computers located at one site, or distributed across multiple sites and interconnected by a communications network.

[0035] The input / output unit 13 includes an input / output interface for connecting an external device. A current sensor 41, a voltage sensor 42, and a temperature sensor 43 are connected to the input / output unit 13 via wired or wireless connections. The control unit 11 acquires the current measured by the current sensor 41, the voltage measured by the voltage sensor 42, and the temperature measured by the temperature sensor 43 via the input / output unit 13. Alternatively, the control unit 11 may acquire various measurement values ​​by communication via the communication unit 14, which will be described later.

[0036] A display device such as a liquid crystal display device may be connected to the input / output unit 13. The control unit 11 may output the estimated result of the charge / discharge capacity via the input / output unit 13 and display it on the display device.

[0037] The communication unit 14 includes a communication interface for communicating with a vehicle ECU (not shown) or other external devices. The control unit 11 transmits and receives various data, including the estimated charge / discharge capacity, to and from the vehicle ECU or other external devices via the communication unit 14.

[0038] In the estimation method of the present embodiment, a Kalman filter is applied to an equivalent circuit model of the power storage device 2 to estimate parameters representing the voltage of the polarization component of the equivalent circuit model (hereinafter also referred to as polarization voltage). The obtained parameters are applied to the equivalent circuit model, and the behavior of the power storage device 2 is predicted using the equivalent circuit model, thereby estimating the charge / discharge performance of the power storage device 2.

[0039] Fig. 3 is a circuit diagram showing an example of the configuration of the equivalent circuit model 5. The equivalent circuit model 5 combines a voltage source for the storage cell 20 with circuit elements such as a resistor and a capacitor, and simulates the charge and discharge behavior of the storage cell 20. The equivalent circuit model 5 shown as an example in Fig. 3 includes a constant voltage source, a DC resistor, and an RC parallel circuit. The RC parallel circuit includes a first RC parallel circuit and a second RC parallel circuit connected in series.

[0040] The constant voltage source is configured by an ideal power supply and simulates the open circuit voltage (OCV), which is the voltage of the storage cell 20 in an unloaded state. The OCV is given as a function of the SOC (State of Charge), temperature, etc. of the storage cell 20. The OCV is defined in advance for each SOC based on, for example, actual measurement data from a battery test.

[0041] The DC resistor includes a resistive element R0 and simulates the ohmic resistance of the energy storage cell 20. The two RC parallel circuits simulate the transient polarization characteristics of the energy storage cell 20. The first RC parallel circuit includes a resistive element R1 and a capacitive element C1 connected in parallel. The second RC parallel circuit includes a resistive element R2 and a capacitive element C2 connected in parallel. The values ​​of the resistive elements R0, R1, and R2 and the capacitive elements C1 and C2 (hereinafter also referred to as circuit parameters) are defined in advance based on, for example, actual measurement data from a battery test. The circuit parameters may be set as values ​​that vary depending on the SOC, temperature, etc. of the energy storage cell 20. The estimation device 1 stores the set circuit parameters in the equivalent circuit model information 122 in association with the temperature, SOC, etc.

[0042] In the above-described equivalent circuit model 5, the terminal voltage V of the storage cell 20 at the time when the time t has elapsed is cell can be expressed by the following formula (1).

[0043]

[0044] In equation (1), I is the current, u(t) is the polarization voltage (voltage drop) generated in the first RC parallel circuit, and u(t) is the polarization voltage (voltage drop) generated in the second RC parallel circuit. The current value I is positive in the case of charging and negative in the case of discharging.

[0045] 3 shows an equivalent circuit model 5 including two RC parallel circuits. Alternatively, the number of RC parallel circuits in the equivalent circuit model 5 may be one or three or more. The equivalent circuit model 5 may be configured to include only a resistive element R instead of the RC parallel circuits.

[0046] The estimation device 1 acquires current measurement data of the current, voltage, and temperature of the power storage device 2, and estimates the polarization voltages u1 and u2 by applying a Kalman filter to the equivalent circuit model 5. The estimated polarization voltages u1 and u2 are used as initial values, and a differential equation that represents the change over time in the polarization voltages u1 and u2 is solved to estimate the charge / discharge capacity of the power storage device 2.

[0047] The charge / discharge capacity is expressed, for example, by a current that can be input / output to / from the power storage device 2. The current that can be input / output to / from the power storage device 2 means a current that will not cause a predicted voltage of the power storage device 2 t seconds from now, when a current is continuously flowed for t seconds from the present time, to exceed or fall below a predetermined voltage value. The estimation device 1 transmits the estimated input / output current to the charging device 30 as a current command value or a current limit value.

[0048] 4 is a flowchart showing an example of a processing procedure executed by the estimation device 1. The processing in each of the following flowcharts may be executed by the control unit 11 in accordance with a program 121 stored in the storage unit 12 of the estimation device 1, or may be realized by a dedicated hardware circuit (e.g., an FPGA or an ASIC) provided in the control unit 11, or may be realized by a combination thereof. The estimation device 1 repeatedly executes the following processing at predetermined estimation intervals, for example. The following description will be given taking as an example a case where charging capacity, i.e., a current that can be input to the power storage device 2, is estimated.

[0049] The control unit 11 of the estimation device 1 acquires measurement data including the current, voltage, and temperature of the power storage cell 20 measured by the current sensor 41, voltage sensor 42, and temperature sensor 43 (step S11). The control unit 11 functions as an acquisition unit. The measurement data is acquired for each power storage cell 20 included in the power storage device 2. The current and temperature may be acquired for each module 21. If the current temperature of the power storage cell 20 is not taken into consideration in the processing described below, the temperature does not need to be acquired.

[0050] The control unit 11 applies a Kalman filter to the equivalent circuit model 5 based on the acquired current measurement data to estimate the polarization voltages u and u and the SOC of the equivalent circuit model 5 (step S12). The control unit 11 functions as a first estimation unit (see step (a) in FIG. 5). The Kalman filter may be an extended Kalman filter.

[0051] The control unit 11 performs an estimation calculation using an extended Kalman filter on a state equation in which the polarization voltages u and u and the SOC of the storage cell 20 are state variables, and an observation equation based on current measurement data, to update the polarization voltages u and u and the SOC. In the extended Kalman filter calculation, the equivalent circuit model 5 is used to estimate the terminal voltages V corresponding to the measured values ​​of the current. cell The predicted terminal voltage V cell The state variables are corrected to minimize the error between the measured voltage and the polarization voltage u1, u2, and SOC after applying the extended Kalman filter. 10 , u 20 Also written as SOC0.

[0052] The control unit 11 calculates the estimated polarization voltage u 10 , u 20 The control unit 11 estimates the polarization voltages u(t) and u(t) after t seconds have elapsed by solving a differential equation that represents the temporal changes in the polarization voltages u and u in the equivalent circuit model 5 of the storage cell 20 using these as initial values ​​(step S13).

[0053] In the equivalent circuit model 5 of FIG. 3, the polarization voltage u of the RC parallel circuit ncan be expressed by the differential equation of the following formula (2).

[0054]

[0055] In equation (2), i is the current and C n is a capacitance element, and R n is a resistive element, and the subscript n is 1 or 2. Considering the safety of the control, C n , R n may be intentionally set to a value larger than that of the actual storage cell. This allows the SOF when no current is applied to be evaluated to be smaller, and after current application starts, the SOF value can be gradually increased by feeding back the actual voltage of the storage cell.

[0056] By applying the Kalman filter to the initial value expressed by the following equation (3) and solving the differential equation (2), the polarization voltage u after t seconds has elapsed is obtained. n The following equation (4) representing (t) is derived.

[0057]

[0058]

[0059] The control unit 11 estimates the current that can be input to the power storage cell 20 based on the estimated polarization voltage u(t) and polarization voltage u(t) (step S14). In step S14, the control unit 11 estimates the current that can be input to the power storage cell 20 based on the estimated time point, and calculates the current that can be input to the power storage cell 20 based on the preset reference voltage V target Determine the current i that can be passed without exceeding

[0060] In the equivalent circuit model 5 of FIG. 3, the predicted voltage of the storage cell 20 after Tp seconds when the storage cell 20 is charged with a current i for Tp seconds from the estimation time point is set as a reference voltage V target Then, the following equation (5) is derived.

[0061]

[0062] By substituting equation (4) into equation (5) and solving for the current i, the predicted voltage of the storage cell 20 after Tp seconds is calculated as the reference voltage V targetThe value of current i that is equal to is calculated. Current i means the maximum current value that can be input and accepted within the operating voltage range. In equations (4) and (5), the OCV can be calculated from the SOC estimated by applying a Kalman filter based on the SOC-OCV characteristics. The circuit parameters can be calculated from the SOC and the current temperature based on the correspondence between the circuit parameters stored in the equivalent circuit model information 122 and the temperature, SOC, etc. The temperature can be calculated using the measured value of the temperature sensor 43.

[0063] Reference voltage V as an estimation condition for current i target , and the energization time Tp may be provided from a higher-level device (e.g., a vehicle ECU), or may be obtained by receiving input from a user. target is the upper limit voltage during charging. target may be a constant such as an upper limit voltage specific to the storage cell 20, or may be defined in the form of a linear function taking into account a safety margin.

[0064] The control unit 11 executes the estimation process of steps S12 to S14 described above for all the storage cells 20 provided in the power storage device 2 to obtain an estimated value of the current i of each storage cell 20 (see step (b) in Figure 5).

[0065] The control unit 11 compares the estimated current i of each storage cell 20 for each module 21, thereby obtaining the current i of the rate-limiting cell among the storage cells 20 constituting the same module 21 (step S15). In the case of charging, the rate-limiting cell is the storage cell 20 with the smallest current i in the module 21, that is, the smallest value of the current i in the module 21 is obtained.

[0066] The control unit 11 estimates the current that can be input to the power storage device 2 by summing up the currents i of the rate-limiting cells in each module 21 that have been acquired (step S16). The control unit 11 may omit step S16 and estimate only the current that can be input to each module.

[0067] The control unit 11 outputs information based on the estimation result through the input / output unit 13 (step S17), and ends the series of processes. The information based on the estimation result includes, for example, the minimum current i in each module, an estimated value of the current that can be input to the power storage device 2, etc. The control unit 11 transmits the information based on the estimation result through the communication unit 14 to the charging device 30, and may also transmit it to the vehicle ECU or an external device.

[0068] In the above processing, the control unit 11 may update the circuit parameters of the resistors R1 and R2 and the capacitors C1 and C2 in equation (4) based on an estimation calculation using an extended Kalman filter.

[0069] The above describes the case where the charging capacity is estimated. Similarly, the discharging capacity can be estimated using the above-mentioned method. When estimating the discharging capacity, the reference voltage V target is the lower limit voltage. When estimating the discharge capacity, the reference voltage V is applied for a predetermined current application time Tp seconds. target The control unit 11 obtains the dischargeable current i so that it does not fall below . In estimating the discharge capacity, the rate-limiting cell in each module 21 is the energy storage cell 20 with the largest current i (the smallest absolute value of the current i) in the module 21. The control unit 11 obtains the largest current i among the estimated currents i of the energy storage cells 20 for each module 21, and sums up the obtained maximum currents i for each module 21, thereby estimating the current that the energy storage device 2 can output.

[0070] In the above description, the charging capacity is estimated as the current that can be input or output. Alternatively, the power that can be input or output may be estimated. The charging / discharging capacity may be estimated by estimating something other than the current or power that can be input or output. For example, it may be estimated whether charging or discharging is possible using a predetermined current conduction pattern defined by the current value and current conduction time of pulse current. In this case, the estimation device 1 may use the above-described formula (5) to calculate a predicted voltage of the power storage device 2 when current is supplied using the predetermined current conduction pattern, and determine whether the calculated predicted voltage deviates from a predetermined reference voltage range.

[0071] The above-described estimation method can be applied to various calculations using an equivalent circuit model other than estimation of charge / discharge capacity. Because the polarization voltage for each polarization element can be calculated accurately based on the estimation method, the accuracy of various calculations using an equivalent circuit model can be improved. For example, the accuracy of calculations of the degree of capacity degradation, capacity maintenance rate (SOH: State of health), and internal resistance can be improved.

[0072] According to this embodiment, it is possible to accurately estimate the voltage fluctuation (increase or decrease) of the polarization component in the equivalent circuit model by taking into account current measurement data. The estimated voltage fluctuation can be used to accurately estimate the charge / discharge performance of the power storage device 2, thereby enabling the power storage device 2 to achieve maximum charge / discharge performance with high reliability. That is, the power storage device 2 can be charged in a short time (at high speed) while suppressing deterioration of the power storage device 2 and preventing the occurrence of abnormal events such as electrodeposition, allowing the power storage device 2 to exhibit high charge acceptance performance. Furthermore, it is possible to continue discharging from the power storage device 2 to a load for a long period of time while preventing a power failure, thereby enabling the realization of autonomous driving functions and safety functions in a vehicle.

[0073] Second Embodiment In a second embodiment, the estimation process is executed for only one storage cell 20 in a module 21. The following mainly describes the above-mentioned differences.

[0074] In the case where a plurality of energy storage cells 20 are provided in a module 21, the estimation device 1 of the second embodiment executes the estimation process described in the first embodiment for only one energy storage cell 20. The current i obtained by the estimation process for one energy storage cell 20 is used as an estimated value of the current i of each module 21.

[0075] 6 is a flowchart showing an example of a processing procedure executed by the estimation device 1 of the second embodiment. The same steps as those in FIG. 4 are assigned the same step numbers, and detailed descriptions thereof will be omitted.

[0076] The control unit 11 of the estimation device 1 acquires measurement data for each module 21, including a representative current, a representative voltage, and a representative temperature that represent the module 21 (step S21). The representative current, the representative voltage, and the representative temperature are each selected from the measurement data of each energy storage cell 20 in the module 21 so as to maximize the safety of the target calculation result.

[0077] When estimating the charging capacity, the representative voltage and the representative temperature may be the maximum voltage and the minimum temperature in the module 21. When estimating the discharging capacity, the representative voltage and the representative temperature may be the minimum voltage and the minimum temperature in the module 21. Whether estimating the charging capacity or the discharging capacity, the current flowing in the same module 21 is considered to be the same value for all the storage cells 20, and therefore the representative current may be a measurement value of the current sensor 41 corresponding to each module 21.

[0078] The representative current, the representative voltage, and the representative temperature may be obtained by acquiring current measurement data of each energy storage cell 20 as needed and extracting measurement values ​​that satisfy predetermined requirements from the acquired measurement data. Alternatively, a representative energy storage cell 20 having the lowest or highest voltage and the lowest temperature in the module 21 may be identified in advance, and measurement data of the identified representative energy storage cell 20 may be selectively acquired. The representative energy storage cell 20 may be identified by, for example, analyzing measurement data of each energy storage cell 20 collected during a predetermined operation period, or may be identified based on the installation environment, such as the arrangement of each energy storage cell 20 in the energy storage device 2.

[0079] The control unit 11 executes the same processes as steps S12 to S14 in the first embodiment. The control unit 11 estimates the polarization voltages u(t) and u(t) using the polarization voltages u and u as initial values, to which the Kalman filter is applied, based on the acquired measurement data including the representative current, representative voltage, and representative temperature of the module 21. The control unit 11 calculates the current i that can be input to the energy storage cell 20 for each module based on the estimation results (see FIG. 7).

[0080] The control unit 11 executes the same processes as steps S16 to S17. The control unit 11 estimates the current that can be input to the power storage device 2 by summing the currents i of the acquired modules 21, and outputs the estimation result.

[0081] According to this embodiment, the calculation load of the estimation process can be reduced, and the system dependency of the amount of calculation can be reduced, which is particularly suitable for an estimation system or a charge / discharge system including a large number of series-connected power storage cells 20.

[0082] The estimation method, estimation device, and computer program can also be applied to mobile objects other than vehicles, and may be applied to aircraft, flying vehicles, HAPS (High Altitude Platform Stations), drones, and other flying objects, as well as to ships, submarines, and stationary power storage devices. A power storage device (stationary power storage device) 2 and a charging device 30 may be applied to the solar power generation system shown in FIG. 8 . The solar power generation device P converts sunlight into electricity and outputs it. Instead of the solar power generation device P, a power generation device using other renewable energy sources, such as wind power (renewable energy power generation device) may be used. The form of the power generation device is not limited.

[0083] The power storage device 2 may have a plurality of lithium-ion batteries (power storage cells 20). The charging device 30 may be a power conditioner. The charging device 20 is connected to the solar power generation device P, the power storage device 2, the load 3, and the power grid 70 via power lines or the like. The charging device 30 converts direct current (DC) generated by the solar power generation device P into alternating current (AC). The charging device 30 outputs the converted AC to a power load 3, such as a household electrical appliance or a facility motor (power load). The charging device 30 also supplies power received from the power grid 70 to the power storage device 2. The power storage device 2 receives power from the solar power generation device P or the power grid 70 via the charging device 30 and stores the received power. The power storage device 2 discharges power to the power grid 70 or the load 3 via the charging device 30. An estimation device 1 (see FIG. 1 ) mounted on the power storage device 2 estimates the current or power that can be charged to and / or discharged from the power storage device 2 based on equation (5), and outputs the estimation result to a charging device 30. A charging / discharging system including such a power storage device 2 and a charging device 30 (power conditioner) can estimate the charging / discharging capacity or the degree of capacity degradation of the power storage element, and can achieve the maximum charging / discharging performance of the power storage device 2 with high reliability. The charging / discharging system is suitable for an energy storage system (ESS) that is operated for a long period of time (e.g., 20 years).

[0084] The estimation method, estimation device, and computer program may be applied to an electric storage device 2 for industrial electric vehicles such as forklifts, automatic guided vehicles (AGVs), and electric carts. For example, the electric storage device 2 for a forklift may have a configuration similar to that shown in FIG. 1 , and a motor for driving the vehicle or a hydraulic cylinder for moving the fork up and down may be connected as the load 3. A charging device 30 may be used that charges the electric storage device 2 (plurality of lithium-ion batteries) via a wired or wireless connection from outside the forklift. Such a forklift can charge the electric storage device 2 in a short time (at high speed) while suppressing deterioration of the electric storage device 2 and preventing the occurrence of abnormal events such as electrodeposition. Furthermore, it is possible to continue discharging the electric storage device 2 to the load for a long time while preventing a power failure.

[0085] 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.

[0086] 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.

[0087] REFERENCE SIGNS LIST 1 Estimation device 11 Control unit 12 Storage unit 13 Input / output unit 14 Communication unit 121 Program 122 Equivalent circuit model information M Recording medium 2 Energy storage device (energy storage element) 20 Energy storage cell 21 Module 5 Equivalent circuit model

Claims

1. An estimation method comprising: acquiring measurement data including the voltage of a storage element and the current flowing through the storage element; estimating parameters related to the polarization component of an equivalent circuit model including an RC parallel circuit using a state estimator based on the acquired measurement data; and estimating the voltage of the polarization component of the storage element at a specific time using the estimated parameters.

2. The estimation method according to claim 1, wherein the charging capacity, discharging capacity, or capacity degradation of the storage element is estimated by applying the estimated voltage of the polarization component to the equivalent circuit model.

3. The estimation method according to claim 1 or 2, wherein the parameter is a parameter representing a voltage of a polarization component in the equivalent circuit model.

4. The estimation method according to claim 1 or 2, wherein the energy storage element comprises a plurality of modules each having a plurality of energy storage cells connected in series, the modules being connected in parallel, and the voltage of the polarization component is determined for some of the energy storage cells in each module.

5. The estimation method according to claim 4, further comprising: acquiring the measurement data including the maximum or minimum voltage among the voltages of each storage cell in each module and the minimum temperature among the temperatures related to each storage cell; and determining the voltage of the polarization component for one storage cell in each module based on the acquired measurement data.

6. An estimation device comprising: an acquisition unit that acquires measurement data including the voltage of a storage element and the current flowing through the storage element; a first estimation unit that applies a state estimator to estimate parameters related to polarization components of an equivalent circuit model including an RC parallel circuit based on the acquired measurement data; and a second estimation unit that uses the estimated parameters to estimate the voltage of the polarization component of the storage element at a specific time.

7. A computer program for causing a computer to execute the following process: acquiring measurement data including the voltage of a storage element and the current flowing through the storage element; estimating parameters related to the polarization component of an equivalent circuit model including an RC parallel circuit using a state estimator based on the acquired measurement data; and estimating the voltage of the polarization component of the storage element at a specific time using the estimated parameters.

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