Capacity estimation device and capacity estimation method

Abstract

This capacity estimation device comprises a control unit, wherein the control unit: selects one or plurality of specific banks from among a plurality of banks of a power storage facility in which banks are connected in a plurality and in parallel, each bank comprising power storage elements connected in a plurality and in series and a current control unit that controls the current flowing through the power storage elements connected in a plurality and in series; discharges and / or charges the power storage elements of the selected specific bank to a prescribed charging rate; acquires the voltage and current of the power storage elements of the specific bank while the power storage elements of the specific bank are being discharged and / or charged; and estimates the capacity of the power storage elements of the specific bank on the basis of the acquired voltage and current.

Description

Capacity estimation device and capacity estimation method

[0001] The present invention relates to a capacity estimation device and a capacity estimation method.

[0002] In recent years, the introduction of renewable energy sources such as solar power and wind power has progressed rapidly. However, the amount of power supplied by these renewable energy sources fluctuates depending on the weather and time of day. To address this issue, energy storage systems (ESS) are being utilized. ESSs are also increasingly being used for energy trading.

[0003] Patent Document 1 discloses an ESS that is configured with a module in which a plurality of storage elements are connected in series, and a bank in which a plurality of modules are connected in series.

[0004] Since ESSs are operated for long periods (e.g., about 20 years), it is important to diagnose the deterioration of the energy storage elements. In particular, for energy trading, it is important to estimate how much power can be discharged, i.e., the full charge capacity (FCC) of the energy storage elements.

[0005] Japanese Patent Application Laid-Open No. 2020-20654

[0006] Some storage elements deteriorate in high and low SOC (State Of Charge) regions. For this reason, conventional ESSs have been mainly operated in an intermediate SOC region between high and low SOC regions, and have not been able to improve the accuracy of estimating the full charge capacity of storage elements.

[0007] An object of the present invention is to provide a capacity estimation device and a capacity estimation method that can improve the accuracy of estimating the full charge capacity of a storage element.

[0008] A capacity estimation device according to one aspect of the present invention includes a control unit, which selects one or more specific banks from among a plurality of banks of a storage facility in which a plurality of banks are connected in parallel, each bank including a plurality of series-connected storage elements and a current control unit that controls the current flowing through the plurality of series-connected storage elements, discharges and / or charges the storage elements of the selected specific bank to a predetermined charge rate, acquires the voltage and current of the storage elements of the specific bank while the storage elements of the specific bank are being discharged and / or charged, and estimates the capacity of the storage elements of the specific bank based on the acquired voltage and current.

[0009] According to the capacity estimation device of the above aspect, it is possible to improve the accuracy of estimating the full charge capacity of the storage element.

[0010] 1 is a diagram illustrating an overview of a remote monitoring system. FIG. 2 is a block diagram illustrating the internal configuration of a device included in the remote monitoring system. FIG. 3 is a block diagram illustrating an example configuration of a power storage system. FIG. 4 is a diagram illustrating an example configuration of a domain according to a first embodiment. FIG. 5 is a diagram illustrating an example of a first stage of control of banks in a domain by a server device. FIG. 6 is a diagram illustrating an example of a second stage of control of banks in a domain by a server device. FIG. 7 is a diagram illustrating an example of a third stage of control of banks in a domain by a server device. FIG. 8 is a diagram illustrating an example of the relationship between the number of banks to be shut off and the SOC at the end of discharge of a storage element. FIG. 9 is a diagram illustrating another example of control of banks in a domain by a server device. FIG. 10 is a diagram illustrating the timing of closing (ON) a circuit breaker of a bank. FIG. 11 is a diagram illustrating an example configuration of a domain according to a second embodiment. FIG. 12 is a diagram illustrating a first example of control of banks in a domain by a server device. FIG. 13 is a diagram illustrating a second example of control of banks in a domain by a server device. FIG. 14 is a diagram illustrating an example of capacity estimation using a ΔSOC method. FIG. 15 is a diagram illustrating an example of a partial charge / discharge profile of a storage element. FIG. 16 is a diagram illustrating an example of capacity estimation based on an overall discharge characteristic.

[0011] (1) A capacity estimation device includes a control unit, which selects one or more specific banks from among a plurality of banks of a storage facility in which a plurality of banks are connected in parallel, each bank including a plurality of series-connected storage elements and a current control unit that controls the current flowing through the plurality of series-connected storage elements, discharges and / or charges the storage elements of the selected specific bank to a predetermined charge rate, acquires the voltage and current of the storage elements of the specific bank while the storage elements of the specific bank are being discharged and / or charged, and estimates the capacity of the storage elements of the specific bank based on the acquired voltage and current.

[0012] The energy storage facility includes multiple banks connected in parallel. The bank includes, for example, multiple modules connected in series, and the module includes multiple energy storage elements connected in series. Some of the energy storage elements within a module may be connected in parallel. The current control unit controls the current (discharge current and charge current) flowing through the multiple energy storage elements included in the bank. The current control unit includes, for example, a circuit breaker. The circuit breaker can turn on and off the discharge current flowing from the bank and the charge current flowing to the bank. The current control unit may be a power supply device (for example, a DC / DC converter) that can control the direction of the current flowing to the bank (i.e., whether it is a charge current or a discharge current).

[0013] The power storage facility is connected to the power grid via a power conditioning system (PCS), and the power storage elements of each bank are discharged to supply a predetermined amount of power, as determined by a contract or the like, to the power grid. The power storage facility also charges the power storage elements of each bank to receive the predetermined amount of power, as determined by the contract or the like, from the power grid. The discharging and charging of the power storage elements is performed, for example, once to several times a day. When the power storage elements of all banks of the power storage facility are discharged to supply a predetermined amount of power to the power grid, the charge rate of the power storage elements of the bank is, for example, 30% to 50%. Setting the lower limit of the charge rate of the storage elements during discharge to such an intermediate value can suppress deterioration of the storage elements.

[0014] The degradation state of a storage element can be determined by estimating its full charge capacity. For example, a method of estimating the charge rate based on the open circuit voltage (OCV) when the storage element is charged and discharged is used to estimate the full charge capacity. In this case, the greater the fluctuation range of the charge rate of the storage element from the start to the end of each charge and discharge, the more accurate the estimation of the full charge capacity becomes.

[0015] The control unit selects a specific bank from among the banks in the energy storage facility, discharges and / or charges the storage elements of the selected specific bank to a predetermined charge rate, and estimates the capacity of the storage elements based on the voltage and current of the storage elements while discharging and / or charging. The capacity estimation of the specific bank is performed, for example, once a year. Although the storage elements are discharged and / or charged at a high rate during capacity estimation, degradation of the storage elements does not progress significantly if the frequency is low. The capacity estimation of the storage elements of the specific bank can be performed while the energy storage facility is in operation.

[0016] Compared to discharging (or charging) all the energy storage elements in the bank, the amount of power discharged (or charged) by only the energy storage elements in a specific bank increases, allowing the charge rate at the end of discharge to be lower (or the charge rate at the end of charge to be higher). This increases the range of fluctuation in the charge rate of the energy storage elements from the start to the end of discharge, improving the accuracy of estimating the full charge capacity. Furthermore, it is possible to periodically diagnose and prove that the energy storage elements can actually be discharged to a low charge rate.

[0017] (2) In the capacity estimation device described in (1) above, the current control unit may include a circuit breaker, and the control unit may use the circuit breaker to interrupt current flowing through storage elements of banks other than the specific bank, thereby discharging and / or charging the storage elements of the specific bank to a predetermined charge rate.

[0018] By using a circuit breaker to interrupt the current flowing through the storage elements of banks other than the specified bank, the amount of power discharged and / or charged by the storage elements of the specified bank can be increased, and the fluctuation range of the charge rate of the storage elements of the specified bank can be increased. Circuit breakers are components that are normally provided in banks of energy storage equipment and do not incur any additional costs. Applying this new control method to circuit breakers can improve the accuracy of estimating the full charge capacity.

[0019] (3) In the capacity estimation device described in (1) or (2) above, the control unit may gradually decrease the number of banks selected for discharging and / or gradually increase the number of banks selected for charging.

[0020] In an operation in which a specified amount of power is supplied from an energy storage facility to a power grid periodically (for example, once to several times a day) based on a contract or the like, the number of banks selected for discharge can be gradually reduced. This makes it possible to gradually increase the range of fluctuation in the charge rate of the energy storage elements from the start to the end of discharge while preventing the occurrence of an abnormality in which the voltage of the energy storage elements in a specific bank drops beyond expectations. In the case of charging, the effect of preventing the occurrence of an abnormality in which the voltage of the energy storage elements rises beyond expectations can also be obtained.

[0021] (4) The current control unit may include a DC / DC converter.

[0022] (5) A capacity estimation method includes selecting one or more specific banks from a plurality of banks of a storage facility in which the banks are connected in parallel, the banks each having a plurality of series-connected storage elements and a current control unit that controls the current flowing through the plurality of series-connected storage elements, discharging and / or charging the storage elements of the selected specific bank to a predetermined charge rate, acquiring the voltage and current of the storage elements of the specific bank while the storage elements of the specific bank are being discharged and / or charged, and estimating the capacity of the storage elements of the specific bank based on the acquired voltage and current.

[0023] The present invention will be specifically described with reference to the drawings showing embodiments thereof.

[0024] 1 is a diagram showing an overview of a remote monitoring system 100. The remote monitoring system 100 enables remote access to information relating to the energy storage elements and power supply-related devices included in a mega solar power generation system S, a thermal power generation system F, and a wind power generation system W. A rectifier (a DC power supply device or an AC power supply device) D installed in an uninterruptible power supply (UPS) U, a stabilized power supply system for railways, etc. may also be remotely monitored.

[0025] A power conditioning system (PCS) P and a power storage system 101 are installed in parallel in the mega solar power generation system S, the thermal power generation system F, and the wind power generation system W. The power storage system 101 may be configured by arranging a plurality of containers C, each housing a power storage module group L, in parallel. Alternatively, the power storage module group L and the power conditioner P may be placed inside a building (power storage room). The power storage module group L includes a plurality of power storage elements. The power storage elements are preferably rechargeable, such as secondary batteries such as lead-acid batteries and lithium-ion batteries, or capacitors. Some of the power storage elements may be non-rechargeable primary batteries.

[0026] In the remote monitoring system 100, a communication device 1 (see FIG. 2 ) is mounted on / connected to each of the power storage systems 101 or devices (P, U, D and a management device M described below) in the systems S, F, and W to be monitored. The remote monitoring system 100 includes the communication device 1, a server device 2 as an information processing device that collects information from the communication device 1, a client device 3 for viewing the collected information, and a network N as a communication medium between the devices.

[0027] The communication device 1 may be a terminal device (measurement monitor) that communicates with a battery management unit (BMU) provided in the energy storage element to receive information about the energy storage element, or may be a controller compatible with ECHONET (registered trademark) / ECHONET Lite (registered trademark). The communication device 1 may be an independent device, or may be a network card-type device that can be mounted on a power conditioner P or a power storage module group L. One communication device 1 is provided for each group consisting of multiple power storage modules in order to acquire information about the power storage module group L in the energy storage system 101. A plurality of power conditioners P are connected to enable serial communication, and the communication device 1 is connected to the control unit of any one of the power conditioners P that serves as a representative.

[0028] The server device 2 shown in FIG. 1 includes a web server function, and presents information obtained from the communication device 1 installed in / connected to each device to be monitored in response to access from the client device 3.

[0029] The network N includes a public communication network N1, which is the so-called Internet, and a carrier network N2 that realizes wireless communication according to a predetermined mobile communication standard. The public communication network N1 includes a general optical fiber line, and the network N includes a dedicated line to which the server device 2 is connected. The network N may also include an ECHONET (registered trademark) / ECHONET Lite (registered trademark) compatible network. The carrier network N2 includes a base station BS, and the client device 3 can communicate with the server device 2 from the base station BS via the network N. An access point AP is connected to the public communication network N1, and the client device 3 can send and receive information to and from the server device 2 via the network N from the access point AP.

[0030] In this way, the remote monitoring system 100 uses the communication device 1 mounted on or connected to each device to be monitored, and the server device 2 collects information such as the SOC, SOH (State Of Health), and other status of the energy storage elements in the energy storage system 101, and abnormalities detected in each device. The collected information is presented collectively via the server device 2.

[0031] Fig. 2 is a block diagram showing the internal configuration of the devices included in the remote monitoring system 100. As shown in Fig. 2, the communication device 1 includes a control unit 10, a storage unit 11, a first communication unit 12, and a second communication unit 13. The control unit 10 is a processor that uses a CPU (Central Processing Unit), and controls each component unit to execute processing using built-in memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

[0032] The storage unit 11 uses a non-volatile memory such as a flash memory. The storage unit 11 stores a device program 1P that is read and executed by the control unit 10. The device program 1P includes communication programs conforming to SSH (Secure Shell), SNMP (Simple Network Management Protocol), etc. The storage unit 11 stores information collected by the processing of the control unit 10, event logs, and other information. The information stored in the storage unit 11 can also be read via a communication interface such as a USB, the terminal of which is exposed on the housing of the communication device 1. The device program 1P stored in the storage unit 11 may be a device program 4P stored on the recording medium 4 that has been read and copied to the storage unit 11.

[0033] The first communication unit 12 is a communication interface that realizes communication with the monitored device to which the communication device 1 is connected. The first communication unit 12 uses, for example, a serial communication interface such as RS-232C or RS-485. For example, the power conditioner P includes a control unit having a serial communication function compliant with RS-485, and the first communication unit 12 communicates with the control unit. When the control boards included in the power storage module group L are connected by a Controller Area Network (CAN) bus and communication between the control boards is realized by CAN communication, the first communication unit 12 is a communication interface based on the CAN protocol. The first communication unit 12 may be a communication interface that complies with the ECHONET (registered trademark) / ECHONET Lite (registered trademark) standards.

[0034] The second communication unit 13 is an interface that realizes communication via the network N, and uses a communication interface such as Ethernet (registered trademark) or a wireless communication antenna. The control unit 10 can be connected to the server device 2 for communication via the second communication unit 13. The second communication unit 13 may be a communication interface that complies with the ECHONET (registered trademark) / ECHONET Lite (registered trademark) standards.

[0035] In the communication device 1 configured in this manner, the control unit 10 acquires measurement data for the energy storage elements obtained by the device to which the communication device 1 is connected via the first communication unit 12. The control unit 10 may function as an SNMP agent by reading and executing an SNMP program and responding to an information request from the server device 2.

[0036] The server device 2 uses a server computer and includes a control unit 20, a storage unit 21, and a communication unit 22. In this embodiment, the server device 2 is described as a single server computer, but processing may be distributed among multiple server computers.

[0037] The control unit 20 is a processor using a CPU or a GPU (Graphics Processing Unit), and uses built-in memories such as ROM and RAM to control each component and execute processing. The control unit 20 executes communication and information processing based on a server program 21P stored in the storage unit 21. The server program 21P includes a web server program, and the control unit 20 functions as a web server that provides web pages to the client device 3. Based on the server program 21P, the control unit 20 collects information from the communication device 1 as an SNMP server.

[0038] The storage unit 21 uses a nonvolatile memory such as a hard disk or a flash memory. The above-mentioned server program 21P and data processing program 22P are stored in the storage unit 21. The server program 21P and data processing program 22P stored in the storage unit 21 may be the server program 51P and data processing program 52P stored in the recording medium 5 that have been read and copied to the storage unit 21.

[0039] The storage unit 21 stores measurement data of the power conditioner P and the power storage module group L of the power storage system 101 to be monitored, which data is collected by processing by the control unit 20. The measurement data is associated with identification information (number) that identifies the power storage system 101 or the power conditioner P. The measurement data of the power storage module group L is stored according to a hierarchical structure of domain, bank, module, or cell.

[0040] The storage unit 21 stores a plurality of images for displaying the status of the power storage module group L or devices P, U, D that are the monitoring targets. The plurality of images are stored in the storage unit 21 in association with identification information that identifies the power storage module group L or devices P, U, D that are the monitoring targets. The plurality of images includes an image that represents the power storage module group L or devices P, U, D.

[0041] The communication unit 22 is a communication device that realizes communication connection and transmission and reception of information via the network N. Specifically, the communication unit 22 is a network card compatible with the network N.

[0042] The client device 3 is a computer used by an operator such as a manager or maintenance technician of the power storage system 101 of the power generation systems S, F, and W. The client device 3 may be a desktop or laptop personal computer, or may be a so-called smartphone or tablet communication terminal. The client device 3 includes a control unit 30, a storage unit 31, a communication unit 32, a display unit 33, and an operation unit 34.

[0043] The control unit 30 is a processor using a CPU. The control unit 30 displays a web page provided by the server device 2 on the display unit 33 based on a client program 3P stored in the storage unit 31. The client program 3P is incorporated into a web page provided by the web server function of the server device 2, includes a script temporarily stored in the client device 3, and a web browser program, and is a program for displaying a web-based screen based on the operation of the server device 2.

[0044] The storage unit 31 uses a non-volatile memory such as a hard disk or a flash memory. Various programs including a client program 3P are stored in the storage unit 31. The client program 3P may be a client program 6P stored on the recording medium 6 that has been read and copied to the storage unit 11.

[0045] The communication unit 32 uses a communication device such as a network card for wired communication, a wireless communication device for mobile communication connecting to a base station BS (see FIG. 1 ), or a wireless communication device compatible with connection to an access point AP. The control unit 30 can establish a communication connection or send and receive information to and from the server device 2 via the network N using the communication unit 32.

[0046] The display unit 33 uses a display such as a liquid crystal display or an organic EL (Electro Luminescence) display. The display unit 33 displays an image of a web page provided by the server device 2 through processing based on the client program 3P of the control unit 30. The display unit 33 is preferably a display with a built-in touch panel, but may also be a display without a built-in touch panel.

[0047] The operation unit 34 is a user interface such as a keyboard and pointing device, or a voice input unit, which can input and output data to and from the control unit 30. The operation unit 34 may be a touch panel of the display unit 33, or physical buttons provided on the housing. The operation unit 34 notifies the control unit 30 of operation information by the user.

[0048] In the remote monitoring system 100 configured as described above, the server device 2 periodically acquires various information including the status of the power conditioner P, the power storage module group L (management device M), the uninterruptible power supply U, and the rectifier D from the communication device 1 based on the data processing program 22P, and stores the information in the storage unit 21. The communication device 1 transmits status information for each power storage module group L, linking the parent-child relationships according to the hierarchical structure. The server device 2 creates screen information (display information) that visually represents the status of the system or device to be monitored in accordance with the hierarchical structure of the power storage cells, based on the information acquired from the power storage elements or each power supply-related device using the communication device 1, and transmits the screen information to the client device 3.

[0049] Fig. 3 is a block diagram showing an example of the configuration of the power storage system 101. The power storage module group L may have a hierarchical structure including power storage modules (also referred to as "modules") in which a plurality of power storage elements (also referred to as "power storage cells" or "cells") are connected in series, banks in which a plurality of modules are connected in series, and domains as power storage facilities in which a plurality of banks are connected in parallel. For convenience, Fig. 3 shows only one domain. The power storage system 101 is a large-scale ESS including a plurality of domains.

[0050] The power storage system 101 includes a power conditioner (PCS) P. The power conditioner P supplies power generated by a power generation system such as a solar system to the power storage system 101, and also supplies power stored in the power storage system 101 to other power consumption equipment (loads) or a power grid. The power conditioner P is connected to multiple banks #1-#N in parallel via power lines 42. A switch 43 is provided between the power conditioner P and a branch point of the power lines 42 to the multiple banks. Opening and closing the switch 43 switches on and off the power supply from the power conditioner P to the entire domain. The switch 43 may be provided inside the power conditioner P.

[0051] Each bank is provided with a circuit breaker 41 as a current control unit. The circuit breaker 41 turns on and off the flow of electricity from the branch points of the power lines 42 to the multiple banks to the power storage module group L. The circuit breaker 41 switches between an ON state in which the power lines 42 are connected to the power storage module group L, and an OFF state in which they are not connected. When the power storage module group L of each bank is connected to the power lines 42, charging or discharging, i.e., electricity is passed through each power storage module group L, via the power conditioner P, the switch 43, the power lines 42, and the circuit breaker 41. In FIG. 3 , a circuit breaker 41 is provided for each bank, but multiple banks may be divided into groups and one circuit breaker 41 may be provided for each group.

[0052] In the example of Fig. 3, a management unit (BMU) M is provided for each bank and each domain. When separately describing the management unit M provided for each bank and the management unit M provided for each domain, for ease of explanation, the management unit (BMU) for the bank is indicated by a B and the management unit (D) for the domain is indicated by a D in parentheses. The management unit (BMU) for the bank communicates via serial communication with a control board (CMU: Cell Monitoring Unit) with a communication function that is built into each power storage module. The management unit M operates by receiving power from the power conditioner P or the power storage module group L via a power line 42.

[0053] The management device (B) M is connected to the circuit breaker 41, and the management device (D) M is connected to the switch 43. The management device M controls the circuit breaker 41 and the switch 43, respectively.

[0054] The communication device 1 is connected to the power storage module group L to be monitored via a management device M. As described above, the communication device 1 is connected to the management device M via a serial communication cable by the first communication unit 12. The communication device 1 may be configured integrally with the management device M. The communication device 1 operates by receiving power via a path separate from the power line 42. These multiple communication devices 1 are communicatively connected to transmit and receive information to each other. In the example shown in FIG. 3 , they are connected via a communication bus. The communication bus is, for example, a LAN cable. Alternatively, the communication bus may be a CAN bus, a LAN cable, or an ECHONET Lite (registered trademark) compatible communication medium. The management device (D)M of a domain and the management device (D)M of another domain within the same system may be connected via a separate communication bus, for example, a CAN bus, and may be capable of communicating with each other. The management device M can control the circuit breaker 41 and the switch 43, respectively, based on instructions from the communication device 1.

[0055] The communication device 1 connected to the management device (B) M of each bank has the function of, upon receiving an instruction via the second communication unit 13, causing the battery module group L to perform a specified charge or discharge, and estimating the full charge capacity from the measured voltage and current values ​​measured during that time.

[0056] The domain (power storage facility) is connected to a power grid (such as a power generation grid or a load) via a power conditioner (PCS) P, and the power storage elements of each bank are discharged to supply a predetermined amount of power, as determined by a contract or the like, to the power grid. The power storage elements of each bank are charged to receive the predetermined amount of power, as determined by a contract or the like, from the power grid. The power storage elements are discharged and charged, for example, once to several times a day. When the power storage elements of all banks of the domain are discharged to supply the predetermined amount of power to the power grid, the SOC of the power storage elements of the bank becomes, for example, 30% to 50%.

[0057] Next, a description will be given of a method for controlling the banks in the domain of the power storage system 101 by the server device 2. The server device 2 has a function as a capacity estimation device.

[0058] (First embodiment) FIG. 4 is a diagram showing an example of the configuration of a domain in the first embodiment. A plurality of storage elements 8 are connected in series to form one bank. In the example of FIG. 4, N1 storage elements 8 are connected in series to form a bank. Note that a bank can also be seen as a configuration in which a plurality of modules are connected in series. A domain has a configuration in which a plurality of banks are connected in parallel. In the example of FIG. 4, N2 banks are connected in parallel. A circuit breaker 41 is connected to each bank, and the on / off of the circuit breaker 41 is controlled by a management device (B)M. In addition, the current and voltage of the storage elements 8 are acquired by the management device (B)M.

[0059] The power conditioner (PCS) P includes a bidirectional DC / DC converter and a bidirectional DC / AC converter and is connected to the power grid. When a predetermined amount of power specified in a contract or the like is supplied from the domain to the power grid, the energy storage elements 8 in the domain are discharged, and the power conditioner (PCS) P boosts the bank voltage to a required DC voltage using a DC / DC converter, converts the boosted DC voltage to an AC voltage using a DC / AC converter, and supplies the AC voltage to the power grid. When the domain receives a predetermined amount of power specified in a contract or the like from the power grid, the energy storage elements 8 in the domain are charged. In this case, the power conditioner (PCS) P converts the AC voltage of the power grid to a DC voltage using a DC / AC converter, reduces the converted DC voltage using a DC / DC converter, and supplies the reduced DC voltage to the bank.

[0060] When a specified amount of power is supplied (sold) to the power grid by discharging the energy storage elements 8 of all banks of a domain, the SOC of the energy storage elements of the bank is, for example, 30% to 50%. Setting the lower limit of the SOC of the energy storage elements during discharge to such an intermediate value can suppress deterioration of the energy storage elements. Meanwhile, to estimate the full charge capacity of the energy storage elements 8, for example, a method of estimating the SOC based on the open circuit voltage (OCV) when the energy storage elements 8 are charged and discharged is used. In this case, if the SOC fluctuates from, for example, 100% to 30% from the start to the end of discharge, the SOC fluctuation range (100% to 30%) is narrow. More specifically, the SOC at the end of discharge is not low, making it impossible to accurately estimate the capacity. Below, a method for controlling the banks in a domain to accurately estimate the capacity is described.

[0061] FIG. 5 illustrates an example of a first stage of control of the banks within a domain by the server device 2. When supplying (selling) a contracted amount of power (e.g., 750 kWh) to the power grid, the circuit breaker 41 of one of the N2 banks is opened (off) to prevent the energy storage elements of that bank from discharging. Assume that, at the start of discharge, the energy storage elements 8 of the N2 banks are fully charged using the contracted amount of power. The server device 2 selects specific (N2-1) banks within the domain and discharges the energy storage elements 8 of the selected banks. In this case, the number of banks to be discharged is reduced from N2 to (N2-1), allowing the energy storage elements 8 of the specific banks to be discharged to a lower SOC. The bank control illustrated in FIG. 5 can be performed during actual operation of the domain, so there is no need to stop the operation of the energy storage system 101.

[0062] In the example of Fig. 5, the SOC based on the OCV (open circuit voltage) of the storage element at the end of discharge is, for example, about 25%, which is not a sufficiently low SOC. In this case, the second stage control illustrated in Fig. 6, which will be described later, is performed.

[0063] FIG. 6 illustrates an example of a second stage of control of the banks within a domain by the server device 2. When supplying (selling) a contracted amount of power (e.g., 750 kWh) to the power grid, the circuit breakers 41 of two of the N2 banks are opened (off) to prevent the energy storage elements of those banks from discharging. Assume that, at the start of discharge, the energy storage elements 8 of the N2 banks are fully charged using the contracted amount of power. The server device 2 selects specific (N2-2) banks within the domain and discharges the energy storage elements 8 of the selected banks. In this case, the number of banks to be discharged is reduced from N2 to (N2-2), allowing the energy storage elements 8 of the specific banks to be discharged to a lower SOC. The bank control illustrated in FIG. 6 can be performed during actual operation of the domain, so there is no need to stop the operation of the energy storage system 101.

[0064] In the example of Fig. 6, the SOC based on the OCV (open circuit voltage) of the storage element at the end of discharge is, for example, about 18%, which is not a sufficiently low SOC. In this case, the third stage control illustrated in Fig. 7, which will be described later, is performed.

[0065] FIG. 7 is a diagram illustrating an example of a third stage of control of the banks within a domain by the server device 2. In the third stage, after the first and second stages described above, the number of specific banks is reduced by, for example, increasing the number of circuit breakers 41 that are opened (turned off) when the daily contracted amount of power is supplied (when selling power), thereby selecting specific (N2-n) banks within the domain. The server device 2 selects specific (N2-n) banks within the domain and discharges the energy storage elements 8 of the selected banks. In this case, since the number of banks to be discharged is reduced from N2 to (N2-n), the energy storage elements 8 of the specific banks can be discharged to a lower SOC. The bank control shown in FIG. 7 can be performed during actual operation of the domain, so there is no need to stop the operation of the energy storage system 101.

[0066] 7, the SOC based on the OCV (open circuit voltage) of the storage element at the end of discharge is, for example, about 4%, which is a sufficiently low SOC. Since the SOC of the storage element 8 is low, the server device 2 can estimate the capacity of the storage element 8 of a specific bank. The method of estimating the capacity will be described in detail later.

[0067] As described above, the control unit 20 selects one or more specific banks from among a plurality of banks of a storage facility in which a plurality of banks are connected in parallel, each bank including a plurality of series-connected storage elements and a circuit breaker 41 (current control unit) that controls the current flowing through the plurality of series-connected storage elements, discharges the storage elements of the selected specific bank to a predetermined SOC, acquires the voltage and current of the storage elements of the specific bank while the storage elements of the specific bank are being discharged, and can estimate the capacity of the storage elements of the specific bank based on the acquired voltage and current.

[0068] It is necessary to supply a contracted amount of power (a predetermined amount of power determined by a contract, etc.) to the power grid. By discharging the storage elements 8 of a specific bank, the number of banks used for discharging is reduced, the amount of power discharged from the storage elements 8 of the specific bank is increased, and the SOC at the end of discharging can be lowered. This increases the fluctuation range of the SOC of the storage elements 8 from the start to the end of discharging, i.e., lowers the SOC at the end of discharging, thereby improving the accuracy of estimating the full charge capacity.

[0069] The predetermined SOC may be a value lower than the intermediate value, for example, 0% or more and less than 30%. The predetermined SOC may more preferably be 0% or more and 20% or less. This is because the lower the SOC value, the greater the fluctuation range of the SOC during charging and discharging.

[0070] The current control unit includes a circuit breaker 41, and the control unit 20 may use the circuit breaker 41 to interrupt the current flowing to the storage elements of banks other than the specific bank, thereby discharging the storage elements 8 of the specific bank to a predetermined SOC.

[0071] By interrupting the current flowing through the storage elements 8 of banks other than the specific bank with the circuit breaker 41, the amount of power discharged by the storage elements 8 of the specific bank can be increased. This makes it possible to increase the fluctuation range of the SOC of the storage elements 8 of the specific bank. Furthermore, because the storage elements 8 are discharged to a low SOC, it is possible to periodically diagnose and prove that they can be discharged to the actual low SOC, and to diagnose the health of the storage elements 8.

[0072] The control unit 20 may gradually decrease the number of banks selected for discharging, and may gradually increase the number of banks selected for charging when charging.

[0073] In an operation in which a specified amount of power is supplied from a domain (power storage facility) to a power grid periodically (for example, once to several times a day) based on a contract or the like, the number of banks selected for discharging can be gradually reduced. This prevents an abnormality in which the voltage of the power storage elements 8 in a specific bank drops below an expected level, while gradually increasing the range of fluctuation in the SOC of the power storage elements from the start to the end of discharging. In the case of charging, this also has the effect of preventing an abnormality in which the voltage of the power storage elements rises above an expected level.

[0074] FIG. 8 is a diagram showing an example of the relationship between the number of banks to be shut off and the SOC at the end of discharge of the storage elements 8. In FIG. 8, the vertical axis indicates the number of banks to be shut off among the banks in the domain, and the horizontal axis indicates the SOC at the end of discharge of the storage elements 8 in a specific bank that is not shut off. The chart shown in FIG. 8 is a schematic illustration, and may not actually be a straight line. Furthermore, the example shown in FIG. 8 may vary depending on the number of banks in the domain.

[0075] As shown in FIG. 8 , when the circuit breaker 41 of one bank in a domain is shut off and the storage elements of the remaining specific bank are discharged, it is assumed that the SOC of the storage elements at the end of discharge is 25%. Next, when the number of banks to be shut off is increased, the circuit breakers 41 of two banks are shut off, and the storage elements of the remaining specific bank are discharged, it is assumed that the SOC of the storage elements at the end of discharge is 20%. Furthermore, when the number of banks to be shut off is increased, the circuit breakers 41 of three banks are shut off, and the storage elements of the remaining specific bank are discharged, it is assumed that the SOC of the storage elements at the end of discharge is 16%. The solid lines shown in FIG. 8 are extended to draw dashed lines. The dashed lines allow estimation of the SOC of the storage elements 8 depending on the number of banks to be shut off. In the example of Figure 8, if the circuit breakers 41 of six banks are shut off, it can be estimated that the SOC at the end of discharge of the storage elements 8 of a specific bank will be approximately 5%, and if the circuit breakers 41 of seven banks are shut off, the SOC at the end of discharge of the storage elements 8 of a specific bank will be approximately 2 to 3%.

[0076] As described above, when the control unit 20 discharges the storage elements 8 of a specific bank, it may calculate the SOC at the end of discharge of the storage elements 8 of the specific bank in correspondence with the number of the specific bank, and determine the minimum number of banks to select based on the calculated SOC.

[0077] By associating the number of specific banks with the SOC at the end of discharge of the storage elements, it is possible to estimate how much the number of specific banks should be to lower the SOC at the end of discharge of the storage elements 8, and when selecting specific banks, it is possible to determine a lower limit for the number of specific banks so that the voltage of the storage elements 8 does not reach the discharge end voltage. The discharge end voltage indicates the voltage beyond which the storage elements 8 should not be discharged once the voltage reaches the discharge end voltage during discharge.

[0078] 9 is a diagram showing another example of control of banks in a domain by the server device 2. In the example of FIG. 9, the order of banks to be shut off by the circuit breaker 41 is reversed compared to the examples of FIGS. 5 to 7. That is, when selecting a specific bank, the control unit 20 may give priority to selecting an unselected bank.

[0079] By prioritizing unselected banks, all banks in the domain can be selected, and the capacities of the storage elements 8 in all banks can be estimated.

[0080] Although not shown in the figure, when the control unit 20 has finished discharging a specific bank, it charges the storage elements 8 of the specific bank until the SOC of the storage elements 8 reaches a predetermined value (e.g., 100%), and while the storage elements 8 of the specific bank are being charged, it may acquire the voltage and current of the storage elements 8 of the specific bank and estimate the capacity (fully charged capacity) of the storage elements 8 of the specific bank based on the acquired voltage and current.

[0081] When charging the storage elements 8 of a specific bank, a specified amount of power is received from the power grid, so it is possible to estimate the capacity of the storage elements 8 during actual operation of the domain. In addition, the fluctuation range of the SOC of the storage elements 8 from the start to the end of charging can be increased, thereby improving the accuracy of estimating the capacity (full charge capacity).

[0082] As described above, the server device 2 performs control to open (off) the circuit breakers 41 of banks other than the specific bank in the domain. The open circuit breaker 41 must then be closed (on) at the required timing. When connecting a bank that has been disconnected by the circuit breaker 41, if there is a voltage difference between the voltage of the disconnected bank and the voltage of an undisconnected bank, an overcurrent may flow from the bank with a higher voltage to the bank with a lower voltage. A method for preventing an overcurrent will be described below.

[0083] FIG. 10 shows the timing of closing (turning on) the circuit breaker 41 of the bank. The upper chart shows the timing of charging and discharging. 750 kWh of discharge occurs between time t1 and time t2, and 750 kWh of charge occurs between time t3 and time t4. For example, timing the discharge to coincide with a time when electricity rates are high can increase revenue, while timing the charge to coincide with a time when electricity rates are low can reduce expenses. Similarly, 750 kWh of discharge occurs between time t5 and time t6, 750 kWh of charge occurs between time t7 and time t8, 750 kWh of discharge occurs between time t9 and time t10, and 750 kWh of charge occurs between time t11 and time t12.

[0084] The middle chart shows the SOC of the storage elements 8 of the bank (indicated by B in the figure). At time t1, the SOC of the storage elements 8 of banks 1 to 20 is 100%. At time t2, when discharge ends, the SOC of the storage elements 8 of banks 1 to 20 is 40%. The circuit breakers 41 of banks 1 to 3 are opened at a required time between time t4 and time t5. During the discharge period from time t5 to t6, banks 1 to 3 are shut off and therefore not discharged. Therefore, the SOC of the storage elements 8 of banks 1 to 3 is maintained at 100%. Meanwhile, the storage elements 8 of banks 4 to 20 are discharged. In this case, the number of banks supplying 750 kWh of power is reduced from 20 to 17, so the storage elements of banks 4 to 20 are discharged to a low SOC, and the SOC at time t6 is 30%.

[0085] After time t8, when charging ends, as shown in the bank voltage chart in the lower part, the charging and discharging kWh are the same, so the voltages of banks 1 to 20 all become the same. Closing the circuit breakers 41 for banks 1 to 3 at this timing prevents overcurrent. After closing the circuit breakers 41 for banks 1 to 3, the circuit breakers 41 for banks 1 to 6 are opened. During the discharge period from time t9 to t10, banks 1 to 6 are shut off and therefore do not discharge. Therefore, the SOC of the energy storage elements 8 in banks 1 to 6 is maintained at 100%. Meanwhile, the energy storage elements 8 in banks 7 to 20 are discharged. In this case, the number of banks supplying 750 kWh of power is reduced from 20 to 14, so the energy storage elements in banks 7 to 20 are discharged to an even lower SOC, resulting in an SOC of 5% at time t10.

[0086] After time t12 when charging ends, as shown in the bank voltage chart at the bottom, the charging and discharging kWh remains the same, so the voltages of banks 1 to 20 all become the same. If the circuit breakers 41 of banks 1 to 6 are closed at this timing, the occurrence of overcurrent can be prevented.

[0087] Second Embodiment While the first embodiment described above includes a circuit breaker 41 as a current control unit, the second embodiment includes a DC / DC converter 44 instead of the circuit breaker 41. As in the first embodiment, the mainstream lithium-ion secondary batteries used as energy storage elements 8 are so-called ternary (NMC) lithium-ion secondary batteries, which use nickel (Ni), manganese (Mn), and cobalt (Co) as the cathode material. On the other hand, LFP (lithium iron phosphate battery) is a lithium-ion secondary battery whose cathode material is composed of lithium (Li), iron (Fe), and phosphorus (P). It does not use rare metals such as cobalt and nickel, which are used in ternary batteries, but instead uses iron phosphate, making it inexpensive to manufacture. Because LFPs exhibit little voltage change during charging and discharging, when the energy storage elements 8 of each bank are LFPs, current shunting occurs between the banks due to variations in the internal resistance of the LFPs. To suppress shunting, a DC / DC converter 44 is used instead of the circuit breaker 41.

[0088] FIG. 11 is a diagram showing an example of the configuration of a domain in the second embodiment. A plurality of storage elements 8 are connected in series to form one bank. In the example of FIG. 11, M1 storage elements 8 are connected in series to form a bank. The storage elements 8 are LFPs. The domain has a configuration in which a plurality of banks are connected in parallel. In the example of FIG. 11, M2 banks are connected in parallel. A DC / DC converter 44 is connected to each bank, and the operation of the DC / DC converter 44 is controlled by a management device (B)M. The current and voltage of the storage elements 8 are detected by the management device (B)M.

[0089] The power conditioner (PCS) P includes a bidirectional DC / AC converter and is connected to the power grid. When a predetermined amount of power specified by a contract or the like is supplied from the domain to the power grid, the storage elements 8 in the domain are discharged, the bank voltage is boosted to a required DC voltage by a DC / DC converter 44, the boosted DC voltage is converted to an AC voltage by a DC / AC converter in the power conditioner (PCS) P, and the AC voltage is supplied to the power grid. When a predetermined amount of power specified by a contract or the like is received from the power grid for the domain, the storage elements 8 in the domain are charged. In this case, the power conditioner (PCS) P converts the AC voltage of the power grid to a DC voltage by a DC / AC converter, reduces the converted DC voltage by a DC / DC converter 44, and supplies the reduced DC voltage to the bank.

[0090] When a specified amount of power is supplied (sold) to the power grid by discharging the energy storage elements 8 of all banks of a domain, the SOC of the energy storage elements of the bank is, for example, 30% to 50%. Setting the lower limit of the SOC of the energy storage elements during discharge to such an intermediate value can suppress deterioration of the energy storage elements. Meanwhile, to estimate the full charge capacity of the energy storage elements 8, for example, a method of estimating the SOC based on the open circuit voltage (OCV) when the energy storage elements 8 are charged and discharged is used. In this case, if the SOC fluctuates from, for example, 100% to 30% from the start to the end of discharge, the SOC fluctuation range (100% to 30%) is narrow. More specifically, the SOC at the end of discharge is not low, making it impossible to accurately estimate the capacity. Below, a method for controlling the banks in a domain to accurately estimate the capacity is described.

[0091] FIG. 12 illustrates a first example of the control of banks within a domain by the server device 2. In FIG. 12, multiple energy storage elements within a bank are collectively illustrated as a single bank. As shown in FIG. 12, assume that the domain has 10 banks. Assume also that the capacity of the energy storage element in bank 1 is to be estimated. When receiving the contracted amount of power from the power grid, the DC / DC converters 44 of banks 1 to 10 are controlled to discharge the energy storage elements in bank 1 and charge the energy storage elements in banks 2 to 10. By controlling the DC / DC converter 44 of bank 1, the SOC of the energy storage elements in bank 1 can be set to 0% at the end of discharging. Furthermore, by controlling the DC / DC converters 44 of banks 2 to 10, the SOC of the energy storage elements in banks 2 to 10 can be set to approximately 55% at the end of charging. By setting the SOC to approximately 55%, deterioration of the energy storage elements can be suppressed. The bank control illustrated in FIG. 12 can be performed during actual operation of the domain, so there is no need to stop the operation of the energy storage system 101.

[0092] As described above, the current control unit includes the DC / DC converter 44, and when charging the storage elements of the domain, the control unit 20 may charge the storage elements of the other banks except for a specific bank (bank 1 in the example of Figure 12), and discharge the storage elements of the selected specific bank to a predetermined SOC.

[0093] When a storage element in a specific bank is discharged, the discharge current is used to charge storage elements in other banks. This allows the storage elements in the specific bank to be discharged until they reach a low SOC, thereby increasing the fluctuation range of the SOC of the storage elements from the start to the end of discharge, i.e., lowering the SOC of the storage elements and improving the accuracy of estimating the full charge capacity.

[0094] FIG. 13 is a diagram illustrating a second example of the control of the banks in a domain by the server device 2. When supplying the contracted amount of power to the power grid, the DC / DC converters 44 of banks 1 to 10 are controlled to charge the storage elements of bank 1 and discharge the storage elements of banks 2 to 10. The DC / DC converter 44 of bank 1 is controlled to make the SOC of the storage elements of bank 1 100% at the end of charging. The DC / DC converters 44 of banks 2 to 10 are also controlled to make the SOC of the storage elements of banks 2 to 10 approximately 45% at the end of discharging. By making the SOC approximately 45%, deterioration of the storage elements can be suppressed. The bank control illustrated in FIG. 13 can be performed during actual operation of the domain, so there is no need to stop the operation of the power storage system 101.

[0095] As described above, when discharging the storage elements of a domain, the control unit 20 may discharge the storage elements of other banks except for a specific bank (bank 1 in the example of Figure 13) and charge the storage elements of a selected specific bank.

[0096] When charging a storage element in a specific bank, the charging current is supplied by using the discharge current of the storage element in another bank. The storage element in the specific bank may be charged until its SOC reaches 100%. This increases the fluctuation range of the SOC of the storage element from the start to the end of charging, improving the accuracy of estimating the full charge capacity.

[0097] Next, a method for estimating the capacity of the storage element will be described.

[0098] Fig. 14 is a diagram showing an example of capacity estimation using the ΔSOC method. As shown in Fig. 14A, it is assumed that a storage element (cell) is discharged at a constant current I for a discharge time t. The stable voltage of the storage element immediately before discharge is defined as OCVa (open circuit voltage), and the voltage at which the storage element stabilizes after discharge is completed is defined as OCVb (open circuit voltage). The current and voltage during discharge of the storage element can be determined using data from the actual operation of the energy storage system 101.

[0099] 14B, the SOCa corresponding to the OCVa and the SOCb corresponding to the OCVb can be determined based on the SOC-OCV characteristics of the power storage element. The SOC-OCV characteristics can be stored in the storage unit 21, for example.

[0100] As shown in FIG. 14C , the estimated capacity (Ah) of a storage element can be calculated by the formula: Estimated capacity (Ah) = {(current I × discharge time t) / (SOCa - SOCb)}. The estimated capacity is the full charge capacity of the storage element. The SOH of the storage element can be calculated from the ratio of the estimated full charge capacity to the full charge capacity in the initial state of the storage element. For example, if the initial full charge capacity of the storage element is 50 Ah and the estimated full charge capacity of the storage element is 40 Ah, the SOH of the storage element is {(40 / 50) × 100} = 80%.

[0101] FIG. 15 is a diagram showing an example of a partial charge / discharge profile of a storage element. In FIG. 15, the horizontal axis represents the amount of electricity (Ah), and the vertical axis represents the voltage (V). The amount of electricity can be determined, for example, by current integration. For example, the amount of electricity Q(t) can be calculated using the formula {Q(t) = ΣI(t) × Δt}. A partial charge / discharge profile can be drawn by plotting the amount of electricity and the voltage at the time when the amount of electricity was obtained (the voltage corresponding to the amount of electricity). Data from the actual operation of the storage system 101 can be used for the current and voltage of the charge / discharge of the storage element.

[0102] FIG. 16 is a diagram showing an example of capacity estimation based on the overall discharge characteristic. In FIG. 16, the horizontal axis represents cumulative capacity (Ah), and the vertical axis represents voltage (V). FIG. 16 shows the overall charge / discharge characteristic (reproduced overall discharge curve) estimated based on the partial charge / discharge profile. The overall charge / discharge characteristic reproduces continuous charging / discharging from the upper limit voltage to the lower limit voltage set for the storage element. The full charge capacity (estimated capacity Q) of the storage element can be calculated by subtracting the cumulative capacity corresponding to the upper limit voltage from the cumulative capacity corresponding to the lower limit voltage of the overall discharge curve.

[0103] The method for estimating the overall discharge characteristics based on the partial charge / discharge profile can be the method described in Japanese Patent Application Laid-Open No. 2023-010325.

[0104] There are various methods for estimating the capacity of a storage element, such as the 0% detection method, the 3% detection method, and the 7% detection method (cell voltage drop detection method). For example, the 3% detection method estimates the capacity of the storage element by estimating the cumulative amount of discharge when the voltage of the storage element decreases from 100% to 3% during discharge. Also, the cumulative amount of charge when the voltage of the storage element decreases from 3% to 100% during charge is estimated as the capacity of the storage element. The SOH can be estimated by the degree to which the estimated capacity has decreased compared to the initial capacity. The same applies to the other 0% and 7% detection methods.

[0105] The above-described capacity estimation using the ΔSOC method, capacity estimation based on the overall discharge characteristics, and cell voltage drop detection method improve the accuracy of capacity estimation as the SOC of the storage element becomes low.

[0106] According to the above-described embodiments, since the energy storage element is discharged to a predetermined SOC, the estimation accuracy of the full charge capacity of the energy storage element can be improved regardless of whether the energy storage element is a ternary or iron-based energy storage element. Furthermore, since the frequency of discharging the energy storage element to the predetermined SOC is low (for example, about several times a year), the energy storage element is not deteriorated.

[0107] 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 combination, 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. A format in which multiple claims cite at least one other claim (multi-multi-claim) may also be used. For example, the capacity estimation method may be implemented by a communication device or a management device instead of by the server device 2.

[0108] REFERENCE SIGNS LIST 1 communication device 10 control unit 11 storage unit 12 first communication unit 13 second communication unit 1P device program 2 server device 20 control unit 22P data processing program 2P automatic monitor 3 client device 33 display unit

Claims

1. A capacity estimation device comprising: a control unit, which selects one or more specific banks from among a plurality of banks of an energy storage facility in which the banks are connected in parallel, the banks each having a plurality of series-connected energy storage elements and a current control unit that controls the current flowing through the plurality of series-connected energy storage elements; discharges and / or charges the energy storage elements of the selected specific bank to a predetermined charge rate; acquires the voltage and current of the energy storage elements of the specific bank while the energy storage elements of the specific bank are being discharged and / or charged; and estimates the capacity of the energy storage elements of the specific bank based on the acquired voltage and current.

2. The capacity estimation device according to claim 1, wherein the current control unit includes a circuit breaker, and the control unit uses the circuit breaker to interrupt current flowing through storage elements in banks other than the specific bank, thereby discharging and / or charging the storage elements in the specific bank to a predetermined charge rate.

3. The capacity estimation device according to claim 1 or 2, wherein the control unit gradually decreases the number of banks selected for discharging and / or gradually increases the number of banks selected for charging.

4. The capacity estimation device according to claim 2, wherein the control unit estimates the charge rate of the storage elements of the specific bank at the end of discharge based on the number of other banks to be cut off and the relationship between the number of other banks to be cut off and the charge rate of the storage elements of the specific bank at the end of discharge.

5. The capacity estimation device according to claim 4, wherein the control unit determines a lower limit number of the specific banks to be selected based on the estimated charging rate.

6. The power storage device according to claim 1 or 2, wherein when selecting the specific bank, the control unit preferentially selects an unselected bank.

7. The capacity estimation device according to claim 1 or claim 2, wherein the control unit discharges the specific bank when electricity rates are high and charges the specific bank when electricity rates are low.

8. The capacity estimation device according to claim 2, wherein the control unit turns on the circuit breakers of the other banks when charging of the specific bank is completed and all banks reach the same voltage.

9. The capacity estimation device according to claim 1, wherein the current control unit includes a DC / DC converter.

10. The capacity estimation device according to claim 9, wherein the control unit charges the storage elements of the other banks and discharges the storage elements of the specific bank, or discharges the storage elements of the other banks and charges the storage elements of the specific bank.

11. A capacity estimation device according to claim 1 or 2, comprising a memory unit, wherein the control unit identifies an SOC corresponding to the acquired voltage of the energy storage elements of a specific bank based on the SOC-OCV characteristics of the energy storage elements stored in the memory unit, and estimates the capacity of the energy storage elements of a specific bank based on the acquired current of the energy storage elements of the specific bank and the SOC.

12. The capacity estimation device according to claim 1 or 2, wherein the control unit estimates the SOH based on the estimated capacity of the storage element of the specific bank and the full charge capacity in an initial state.

13. The capacity estimation device according to claim 1 or 2, wherein the control unit estimates the capacity of the storage element of the specific bank based on a partial charge / discharge profile generated by plotting the amount of electricity determined by current integration and the voltage at the time when the amount of electricity was obtained.

14. A method for estimating capacity, comprising: selecting one or more banks from among a plurality of banks of an energy storage system, each of which is connected in parallel, and each bank comprises a plurality of series-connected energy storage elements and a current control unit that controls the current flowing through the plurality of series-connected energy storage elements; discharging and / or charging the energy storage elements of the selected specific bank to a predetermined charge level; acquiring the voltage and current of the energy storage elements of the specific bank while the energy storage elements of the specific bank are being discharged and / or charged; and estimating the capacity of the energy storage elements of the specific bank based on the acquired voltage and current.

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