WO2025173451A1 - Estimation method, estimation apparatus, and computer program - Google Patents

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

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

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 when it is assumed that the required power continues to be output from the secondary battery over a period of time from the present until a specified time has elapsed, based on an equivalent circuit model. The battery energy prediction device inputs the current charging rate and current temperature of the secondary battery and predicts the remaining energy of the secondary battery based on relationship information between the charging rate, temperature, and predicted voltage, which is corrected to match the deviation between the calculated predicted voltage and the predicted voltage derived from the relationship information.

Japanese Patent Application Laid-Open No. 2016-173281

The technology in Patent Document 1 does not improve the accuracy of predictive calculations using equivalent circuit models.

The purpose of this disclosure is to provide technology that can improve the accuracy of calculations using equivalent circuit models.

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

This disclosure makes it possible to improve the accuracy of calculations using equivalent circuit models.

FIG. 1 is a block diagram illustrating an example of the configuration of an estimation system. FIG. 1 is a block diagram illustrating an example of the configuration of an estimation device according to a first embodiment. FIG. 2 is a circuit diagram showing an example of the configuration of an equivalent circuit model. 10 is a flowchart illustrating an example of a processing procedure executed by the estimation device. FIG. 1 is a functional block diagram of an estimation device according to a first embodiment. 10 is a flowchart illustrating an example of a processing procedure executed by an estimation device according to a second embodiment. FIG. 10 is a functional block diagram of an estimation device according to a second embodiment. FIG. 1 is a diagram illustrating an overview of a solar power generation system.

An outline of the embodiment will be described below.
(1) An estimation method according to one aspect of the present disclosure includes: (a) acquiring measurement data including a voltage of a storage element and a current flowing through the storage element; applying 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 (b) using the estimated parameters to estimate the voltage of the polarization component of the storage element at a specific time.
Here, the "specific time" may be a time in the future or the current time.
The "state estimator" may be a Kalman filter or another state estimator (for example, a Lehenberger observer, a particle filter, an H∞ filter, or a sliding mode observer).

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 component based on the measured values of the storage element, and in step (b), the temporal change in the voltage of the polarization component in the equivalent circuit model is determined (see Figure 5). By using parameters updated by feeding back the current voltage value obtained in step (a) when calculating the voltage change of the polarization component using the equivalent circuit model, any model errors can be compensated for, thereby improving the accuracy of calculations using the equivalent circuit model.

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 that is 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. 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 that takes measurement data into account, without changing the equivalent circuit model itself. Even if there is model error, the error can be compensated for and the state of the energy storage element can be accurately estimated.

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

The estimation method described in (2) above makes it possible to estimate the charge or discharge capacity (hereinafter also referred to as charge/discharge capacity) of a storage element, as well as the degree of capacity degradation. Estimating charge/discharge capacity is equivalent to estimating the short-term voltage characteristics and power characteristics (SOF: State Of Function) of a storage element. In recent years, there has been a demand for a function to estimate SOF, for example, to realize autonomous driving functions and safety functions in vehicles. With the above configuration, charge/discharge capacity can be estimated with high accuracy based on the voltage of the polarization component that is appropriately estimated using an equivalent circuit model. As the measured voltage can be reflected in the charge/discharge capacity estimation, the reliability of the charge/discharge capacity estimation is improved.

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

The estimation method described in (3) above allows parameters that are difficult to measure to be estimated using 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, etc., the computational load when estimating the voltage of the polarization component of the storage element can be reduced and immediacy can be improved.

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

The estimation method described in (4) above reduces calculation costs compared to performing calculations for each cell. In a system equipped with multiple energy storage cells 20, the amount of calculations can be prevented from increasing in response to an increase in the number of cells. This reduces the system dependency of the amount of calculations, improving versatility.

(5) In the estimation method described in (4) above, the measurement data may be acquired 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 the voltage of the polarization component for one storage cell in each module may be calculated based on the acquired measurement data.

The estimation method described in (5) above selects the measured values for each module so that the estimated voltage value leans toward the safe side, further improving the reliability of the estimation results.

(6) An estimation device according to one aspect of the present disclosure includes an acquisition unit that acquires measurement data including a voltage of a storage element and a current flowing through the 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 uses the estimated parameters to estimate a voltage of the polarization component of the storage element at a specific time.
(7) A computer program according to one aspect of the present disclosure causes a computer to perform a process of acquiring measurement data including a voltage of a storage element and a current flowing through the storage element, applying a state estimator based on the acquired measurement data to estimate parameters related to a polarization component of an equivalent circuit model including an RC parallel circuit, and using the estimated parameters to estimate the voltage of the polarization component of the storage element at a specific time.

The following embodiments will be described later.
(8) A charging/discharging system including: a storage element; the estimation device according to (6) above; and a charging device that receives information based on the estimation result by the estimation device.
(9) The charging/discharging system according to (8) above, further comprising a power conditioner as the charging device for charging/discharging the storage element.
(10) The charging/discharging system according to (9) above, further comprising a renewable energy power generation device connected to the power conditioner.
(11) A power storage device including a power storage element and the estimation device described in (6) above.

This disclosure will be specifically described with reference to drawings showing embodiments thereof.

(First embodiment)
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), hybrid electric vehicles (HEVs), etc. The estimation system includes an estimation device 1 and a power storage device 2.

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.

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

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 terminals 2a and 2b. A charging device 30 is also connected to 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 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, 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 the current command value or current limit value received from the estimation device 1.

The energy storage device 2 includes multiple current sensors 41, multiple voltage sensors 42, and multiple temperature sensors 43. For example, one current sensor 41, one voltage sensor 42, and one temperature sensor 43 are provided for each module 21. A voltage sensor 42 and/or a temperature sensor 43 may also be provided for each energy storage cell 20.

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 Figure 1, the connection lines between some of the sensors and the estimation device 1 are not shown.

In this 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, terminal device, or vehicle ECU 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, etc., via communication.

Figure 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 memory 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 installed on a single server, or may be realized using a cloud server.

The control unit 11 is an arithmetic circuit equipped with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. The CPU equipped in the control unit 11 executes various computer programs stored in the ROM and 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 have 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.

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

The equivalent circuit model information 122 includes information relating to the 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) relating to the circuit elements of the equivalent circuit model.

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, USB memory, or 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.

The input/output unit 13 has an input/output interface for connecting to 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 via communication via the communication unit 14, which will be described later.

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 charge/discharge capacity results via the input/output unit 13 and display them on the display device.

The communication unit 14 includes a communication interface that enables communication with a vehicle ECU (not shown) or other external devices. The control unit 11 transmits and receives various data, including estimated charging and discharging capacity, to and from the vehicle ECU or other external devices via the communication unit 14.

In the estimation method of this 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.

Figure 3 is a circuit diagram showing an example configuration of equivalent circuit model 5. Equivalent circuit model 5 combines the voltage source of the storage cell 20 with circuit elements such as resistors and capacitors to simulate the charge and discharge behavior of the storage cell 20. The equivalent circuit model 5 shown as an example in Figure 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.

The constant voltage source is composed of 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) of the storage cell 20, temperature, etc. The OCV is defined in advance for each SOC based on, for example, actual measurement data from a battery test.

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.

In the above-described equivalent circuit model 5, the terminal voltage V _cell of the storage cell 20 after the time t has elapsed can be expressed by the following formula (1).

In equation (1), I is the current, _u1 (t) is the polarization voltage (voltage drop) generated in the first RC parallel circuit, and _u2 (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.

FIG. 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 an RC parallel circuit.

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 temporal change in the polarization voltages _u1 and _u2 is solved to estimate the charge/discharge capacity of the power storage device 2.

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, when a current is continuously flowed for t seconds from the present time, causes a predicted voltage of the power storage device 2 t seconds from now to not 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.

Figure 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 the program 121 stored in the memory unit 12 of the estimation device 1, or may be implemented by a dedicated hardware circuit (e.g., FPGA or ASIC) provided in the control unit 11, or may be implemented by a combination of these. The estimation device 1 repeatedly executes the following processing at predetermined estimation intervals, for example. The following describes an example of estimating the charging capacity, i.e., the current that can be input to the power storage device 2.

The control unit 11 of the estimation device 1 acquires measurement data including the current, voltage, and temperature of the current 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 storage cell 20 included in the energy storage device 2. The current and temperature may be acquired on a module 21 basis. If the current temperature of the storage cell 20 is not taken into consideration in the processing described below, the temperature does not need to be acquired.

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 _u1 and _u2 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.

The control unit 11 updates the polarization voltages _u1 , _u2 and SOC by performing an estimation calculation applying an extended Kalman filter to a state equation with the polarization voltages _u1 , _u2 and SOC of the storage cells 20 as state variables and an observation equation based on current measurement data. In the extended Kalman filter calculation, the terminal voltage _Vcell corresponding to the measured value of current is predicted using the equivalent circuit model 5, and the state variables are corrected to minimize the error between the predicted terminal voltage _Vcell and the measured value of voltage. The polarization voltages _u1 , _u2 and SOC after application of the extended Kalman filter are also referred to as polarization voltages _u10 , _u20 and SOC0 _, respectively.

The control unit 11 estimates the polarization voltages u1 _(t) and _u2 (t) after t seconds have elapsed by solving differential equations that represent the temporal changes in the polarization voltages _u1 and _u2 in the equivalent circuit model 5 of the storage cell 20 using the estimated polarization voltages _u10 and _u20 as initial values (step S13). The control unit 11 functions as a second estimation unit.

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

In equation (2), i is a current, _Cn is a capacitance element, _Rn is a resistance element, and the subscript n is 1 or 2.
In consideration of the safety of the control, _Cn and _Rn may be set to values intentionally larger than those of the actual storage cells. 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 cells.

By applying the Kalman filter to the initial value expressed by the following equation (3) and solving the differential equation of equation (2), the following equation (4) is derived, which represents the polarization voltage u _n (t) after t seconds have elapsed.

Based on the estimated polarization voltages _u1 (t) and _u2 (t), the control unit 11 estimates the current that can be input to the energy storage cell 20 (step S14). In step S14, the control unit 11 determines the current i that can be applied to the energy storage cell 20 for a predetermined current application time Tp seconds, using the estimated time point as a reference, so that the current i does not exceed a predetermined reference voltage _Vtarget .

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

By substituting equation (4) into equation (5) and solving for the current i, the value of the current i at which the predicted voltage of the power storage cell 20 after Tp seconds will be equal to the reference voltage V _target is calculated. The current i refers to the maximum current value that can be input within the operating voltage range. In equations (4) and (5), the OCV can be calculated from the SOC ₀ estimated by applying a Kalman filter based on the SOC-OCV characteristics. The circuit parameters can be calculated from the SOC ₀ 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 a value measured by the temperature sensor 43.

The reference voltage V _target and the current application time Tp as the estimation conditions for the current i may be provided, for example, from a higher-level device (e.g., a vehicle ECU) or may be acquired by receiving input from a user. The reference voltage V _target is an upper limit voltage during charging. The reference voltage V _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.

The control unit 11 performs the estimation process of steps S12 to S14 described above for all 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).

The control unit 11 compares the estimated current i of each storage cell 20 for each module 21 to obtain 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 in the module 21 with the smallest current i, i.e., the smallest value of current i in the module 21 is obtained.

The control unit 11 estimates the current that can be input to the power storage device 2 by summing 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.

The control unit 11 outputs information based on the estimation results via the input/output unit 13 (step S17), and ends the series of processes. The information based on the estimation results 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 results via the communication unit 14 to the charging device 30, and may also transmit it to the vehicle ECU or an external device.

In the above process, the control unit 11 may update the circuit parameters of the resistors R ₁ and R ₂ and the capacitors C ₁ and C ₂ in equation (4) based on an estimation calculation using an extended Kalman filter.

The above describes the case where charging capacity is estimated. Similarly, discharging capacity can also be estimated using the above-mentioned method. When discharging capacity is estimated, the reference voltage V _target is a lower limit voltage. When discharging capacity is estimated, a dischargeable current i is calculated so that the voltage does not fall below the reference voltage V _target for a preset current flow time Tp seconds. In estimating discharging 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 the obtained maximum currents i for each module 21 to estimate the current that can be output by the energy storage device 2.

In the above, 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 also 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 pattern defined by the current value and current duration of pulse current. In this case, the estimation device 1 may use the above-mentioned equation (5) to determine the predicted voltage of the power storage device 2 when current is applied using the predetermined current pattern, and determine whether the determined predicted voltage deviates from a predetermined reference voltage range.

The estimation method described above can be applied to various calculations using equivalent circuit models other than estimating 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 equivalent circuit models can be improved. For example, the accuracy of calculations of capacity degradation, capacity maintenance rate (SOH: State of health), and internal resistance can be improved.

According to this embodiment, the voltage fluctuation (increase or decrease) of the polarization component in the equivalent circuit model can be estimated with high accuracy 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 achieving maximum charge/discharge performance with high reliability from the power storage device 2. In other words, the power storage device 2 can be charged in a short time (at high speed) while suppressing deterioration in 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, discharge from the power storage device 2 to a load can be continued for a long period of time while preventing power loss (power fail), enabling autonomous driving functions and safety functions to be realized in vehicles.

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

In the second embodiment, when multiple storage cells 20 are provided in a module 21, the estimation device 1 performs the estimation process described in the first embodiment for only one storage cell 20. The current i obtained by the estimation process for one storage cell 20 is used as the estimated value of the current i for each module 21.

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

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 storage cell 20 within the module 21 so as to maximize the safety of the target calculation results.

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

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

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 ₁ (t) and u ₂ (t) using the polarization voltages u 1 and u ₂ to which a Kalman filter is applied as initial values, 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 storage cell 20 for each module based on the estimation results (see FIG. 7).

The control unit 11 executes the same processing 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 current i of each module 21 that has been acquired, and outputs the estimation result.

This embodiment reduces the computational load of the estimation process and reduces the system dependency of the amount of calculation. It is particularly suitable for estimation systems and charge/discharge systems that include a large number of series-connected energy storage cells 20.

The estimation method, estimation device, and computer program can also be applied to mobile objects other than vehicles, and may be applied to flying objects such as aircraft, flying vehicles, HAPS (High Altitude Platform Station), drones, ships, submarines, and stationary energy 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 electric power and outputs it. Instead of the solar power generation device P, a power generation device using other renewable energy such as wind power (renewable energy power generation device) may be used. The form of the power generation device is not limited.

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.
The estimation device 1 (see Figure 1) installed in the storage device 2 estimates the current or power that can be charged to and/or discharged from the storage device 2 based on equation (5), and outputs the estimation result to the charging device 30.
A charge/discharge system including such an energy storage device 2 and a charging device 30 (power conditioner) can estimate the charge/discharge capacity or the degree of capacity degradation of the energy storage element, and can reliably achieve maximum charge/discharge performance by the energy storage device 2. The charge/discharge system is suitable for an energy storage system (ESS) that is operated for a long period of time (e.g., 20 years).

The estimation method, estimation device, and computer program may be applied to an electricity storage device 2 for industrial electric vehicles such as forklifts, AGVs (Automatic Guided Vehicles), and electric carts.
1 , a motor for driving the vehicle or a hydraulic cylinder for moving the forks up and down may be connected as the load 3. A charging device 30 may be used that charges the power storage device 2 (plurality of lithium ion batteries) from outside the forklift in a wired or wireless manner.
Such a forklift can charge the electricity storage device 2 in a short time (at high speed) while suppressing deterioration of the electricity storage device 2 and preventing the occurrence of abnormal events such as electrodeposition in the electricity storage device 2. In addition, it can continue discharging electricity from the electricity storage device 2 to a load for a long time while preventing a power failure.

The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. 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 within a range consistent with the present invention, and multiple processes may be executed in parallel. The entity that performs each process is not limited, and the process of each device may be executed by another device within a range consistent with the present invention.

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 citation format. Furthermore, the claims use a format in which a claim cites two or more other claims (multi-claim format), but this is not limited to this. They may also be written in a format in which multiple claims cite at least one other claim (multi-multi-claim format).

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 Power storage device (power storage element)
20 Storage cell 21 Module 5 Equivalent circuit model

Claims (7)

Acquire measurement data including a voltage of a storage element and a current flowing through the storage element;
estimating parameters related to polarization components of an equivalent circuit model including an RC parallel circuit by applying a state estimator based on the acquired measurement data;
The estimation method estimates a voltage of a polarization component of the storage element at a specific time using the estimated parameters. The estimation method according to claim 1 , wherein the charging capacity, discharging capacity, or capacity degradation degree of the storage element is estimated by applying the estimated voltage of the polarization component to the equivalent circuit model. 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. The energy storage element includes a plurality of modules each having a plurality of energy storage cells connected in series,
Each module is connected in parallel,
The estimation method according to claim 1 or 2, further comprising determining the voltage of the polarization component for some of the storage cells in each module. acquiring the measurement data including a maximum voltage or a minimum voltage among the voltages of the storage cells in each module and a minimum temperature among the temperatures related to the storage cells;
The estimation method according to claim 4 , further comprising: determining a voltage of the polarization component for one of the storage cells in each module based on the acquired measurement data. an acquisition unit that acquires measurement data including a voltage of a storage element and a current flowing through the storage element;
a first estimation unit that estimates parameters related to polarization components of an equivalent circuit model including an RC parallel circuit by applying a state estimator based on the acquired measurement data;
and a second estimation unit that estimates a voltage of a polarization component of the storage element at a specific time using the estimated parameter. Acquire measurement data including a voltage of a storage element and a current flowing through the storage element;
estimating parameters related to polarization components of an equivalent circuit model including an RC parallel circuit by applying a state estimator based on the acquired measurement data;
A computer program for causing a computer to execute a process of estimating a voltage of a polarization component of the storage element at a specific time using the estimated parameters.