Stationary energy storage system

Abstract

This invention provides a stationary energy storage system that can reduce the frequency of system maintenance by controlling the usage load of multiple energy storage devices in the stationary energy storage system according to the lifespan of the equipment. [Solution] The stationary energy storage system 100 comprises a first energy storage device 110 and a second energy storage device 120 electrically connected to a power grid PG, and a system control unit 20 that controls a plurality of energy storage devices 104. The first energy storage device 110 has a first battery 113, and the second energy storage device 120 has a second battery 123. The system control unit 20 obtains the first state of overheating (SOH) of the first battery 113 and the second state of overheating (SOH) of the second battery 123, and if the SOH of the first battery is higher than the SOH of the second battery, it distributes a higher charge / discharge current to the first battery 113 than to the second battery 123.

Description

Technical Field

[0006] , ,

[0001] This disclosure relates to a stationary energy storage system.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2020-170364 (Patent Document 1) discloses a stationary energy storage system that predicts the power demand of the entire power system based on past power demands, past power performance, immediate demands, weather, etc., and assigns the necessary power supply and demand adjustment power to a plurality of storage batteries.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the stationary energy storage system disclosed in Japanese Unexamined Patent Application Publication No. 2020-170364, for example, a power storage device that was used in an electric vehicle is reused as the stationary power source of the stationary energy storage system. Each of the plurality of power storage devices has a different degree of battery deterioration. As a result, the maintenance frequency due to the equipment life of the power storage device increases, and there is a risk that the opportunity loss of utilizing the power storage device in the stationary energy storage system increases.

[0005] This disclosure has been made to solve the above problems, and an object thereof is to provide a stationary energy storage system capable of suppressing the maintenance frequency of the system by controlling the usage load of a plurality of power storage devices in the stationary energy storage system according to the equipment life.

Means for Solving the Problems

[0006] A stationary energy storage system according to the first aspect of this disclosure comprises a first energy storage device and a second energy storage device electrically connected to a power grid, and a system control unit that controls the first energy storage device and the second energy storage device, wherein the first energy storage device has a first battery and the second energy storage device has a second battery, and the system control unit acquires the first state of health (SOH) of the first battery and the second state of health (SOH) of the second battery, and when the SOH of the first battery is higher than the SOH of the second battery, it distributes a higher charge / discharge current to the first battery than to the second battery.

[0007] A stationary energy storage system according to the second aspect of this disclosure comprises a first energy storage device and a second energy storage device electrically connected to a power grid, and a system control unit that controls the first energy storage device and the second energy storage device, wherein the first energy storage device has a first battery and the second energy storage device has a second battery, and the system control unit obtains the first state of health (SOH) of the first battery and the second state of health (SOH) of the second battery, and when the SOH of the first battery is lower than the SOH of the second battery, it distributes a larger charge / discharge current to the first battery than to the second battery.

[0008] A stationary energy storage system according to the third aspect of this disclosure comprises a first energy storage device and a second energy storage device electrically connected to a power grid, and a system control unit that controls the first energy storage device and the second energy storage device. The first energy storage device has a first battery and a first fuse electrically connected to the first battery, and the second energy storage device has a second battery and a second fuse electrically connected to the second battery. The system control unit acquires a first integrated charge / discharge current value for the first battery and a second integrated charge / discharge current value for the second battery, and when the first integrated charge / discharge current value is greater than the second integrated charge / discharge current value, it distributes a larger charge / discharge current to the first battery than to the second battery.

[0009] A stationary energy storage system according to the fourth aspect of this disclosure comprises a first energy storage device and a second energy storage device electrically connected to a power grid, and a system control unit that controls the first energy storage device and the second energy storage device. The first energy storage device has a first battery and a first fuse electrically connected to the first battery, and the second energy storage device has a second battery and a second fuse electrically connected to the second battery. The system control unit acquires a first integrated charge / discharge current value for the first battery and a second integrated charge / discharge current value for the second battery, and when the first integrated charge / discharge current value is less than the second integrated charge / discharge current value, it distributes a larger charge / discharge current to the first battery than to the second battery.

[0010] A stationary energy storage system according to the fifth aspect of this disclosure comprises an energy storage device electrically connected to a power grid and a system control unit that controls the energy storage device, wherein the energy storage device has a battery and a fuse electrically connected to the battery, and the system control unit acquires the integrated charge / discharge current value of the battery, and if the integrated charge / discharge current value exceeds the fuse replacement threshold, distributes a charge / discharge current to the battery that is less than or equal to a current that does not affect the lifespan of the fuse. [Effects of the Invention]

[0011] According to the stationary energy storage system described herein, the frequency of system maintenance can be reduced by controlling the usage load of multiple energy storage devices in the stationary energy storage system according to the lifespan of the equipment. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of an energy management system according to an embodiment of the present disclosure. [Figure 2] This is a control flow diagram of an energy management system according to an embodiment of the present disclosure. [Figure 3] This figure shows an example of the distribution of charging current in an energy management system according to an embodiment of the present disclosure. [Figure 4] This is a control flow diagram of an energy management system according to Modification 1 of the embodiment of the present disclosure. [Modes for carrying out the invention]

[0013] Embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their descriptions will not be repeated. <Overall configuration of the energy management system> Figure 1 is a diagram showing the schematic configuration of an energy management system according to the embodiment of this disclosure. The energy management system 1 comprises a power grid PG, a TSO (Transmission System Operator) server 10, an EM (Energy Management) server 20, and a stationary energy storage system 100.

[0014] A power grid (PG) is a power network constructed by power plants and transmission and distribution facilities. The TSO server 10 is a server managed by the power grid administrator. The TSO server 10 has a processor and memory (not shown) and monitors the status of the power grid (e.g., supply and demand balance and frequency), and requests energy management from the EM server 20. This ensures that the power grid is maintained in a state where it can supply high-quality power stably and regularly. A power grid (PG) is, for example, an AC grid provided by a power company.

[0015] The EM server 20 is, for example, a server managed by an aggregator. An aggregator is an electric utility that provides energy management services by bundling multiple power adjustment resources, such as regions or designated facilities. The EM server 20 includes a processor 21 and a storage device 22. An example of the processor 21 is a CPU (Central Processing Unit). The storage device 22 is configured to store the stored information. The storage device 22 stores information for each of the multiple energy storage devices 104 (e.g., specifications, control information, and sensor information), distinguished by the identification information (battery ID) of the energy storage device 104. The control information includes information for the EM server 20 to individually control the DC / DC conversion circuit of each of the multiple energy storage devices 104.

[0016] The stationary energy storage system 100 is, for example, a system that manages battery resources under the jurisdiction of an aggregator that manages the EM server 20. The stationary energy storage system 100 includes a PCU 101, a circuit breaker 102, a circuit breaker 103, and a plurality of energy storage devices 104.

[0017] The PCU 101 is configured to communicate with the EM server 20 and includes a DC / AC conversion circuit (not shown). The DC / AC conversion circuit is configured to convert the DC power supplied from the multiple energy storage devices 104 into AC power and output it to the power grid PG, according to commands from the EM server 20. Alternatively, the DC / AC conversion circuit is configured to convert the AC power input from the power grid PG into DC power and output it to each of the multiple energy storage devices 104.

[0018] The multiple energy storage devices 104 include a first energy storage device 110, a second energy storage device 120, a third energy storage device 130, and a fourth energy storage device 140. Since the first energy storage device 110, the second energy storage device 120, the third energy storage device 130, and the fourth energy storage device 140 have substantially the same configuration, the following description will mainly focus on the first energy storage device 110.

[0019] The first power storage device is, for example, a reused power storage device that was mounted on an electric vehicle. The first power storage device 110 has, for example, a battery pack 111, a SMR (System Main Relay) 116, a DC / DC conversion circuit 117, and a JB (Junction Box) 118.

[0020] The battery pack 111 has a power storage stack 112, a monitoring unit 114, and a battery ECU 115. The power storage stack 112 has a plurality of power storage cells 113. The plurality of power storage cells 113 are electrically connected in series. The power storage cell 113 is a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery.

[0021] The monitoring unit 114 has detection sensors that detect the electrical characteristic information of each of the plurality of power storage cells 113. The electrical characteristic information is, for example, information on the temperature Tb, current Ib, and voltage Vb of each of the plurality of power storage cells 113. The monitoring unit 114 outputs the acquired electrical characteristic information to the ECU 30. The monitoring unit 114 also functions as a BMS (Battery Management System) that has a SOC (State Of Charge) estimation function for estimating the SOC based on the acquired electrical characteristic information of each of the plurality of power storage cells 113, a SOH (State of Health) estimation function for estimating the SOH of each of the plurality of power storage cells 113, and a communication function. The electrical characteristic information also includes the SOC and SOH of each of the plurality of power storage cells 113 estimated by the monitoring unit 114. Note that SOH is an index indicating the degree of battery degradation, and is represented by the ratio of the initial full charge capacity of the battery to the actual full charge capacity. The closer the SOH is to 0%, the more advanced the battery degradation is.

[0022] The battery ECU 115 is formed to be communicable with the EM server 20. The battery ECU 115 is formed to be controllable with respect to the SMR 116 and the DC / DC conversion circuit 117 based on an instruction from the EM server 20. The battery ECU 115 acquires electrical characteristic information from the monitoring unit 114. The acquired electrical characteristic information is stored in a storage unit (not shown) that the battery ECU 115 has.

[0023] The SMR116 is positioned between the electrically connected battery pack 111 and PCU 101. When the SMR116 is closed (ON) (i.e., in a conductive state) in response to a control signal from the battery ECU 115, power can be exchanged between the battery pack 111 and PCU 101. On the other hand, when the SMR116 is opened (OFF) (i.e., in a disconnected state) in response to a control signal from the ECU 30, the electrical connection between the battery pack 111 and PCU 101 is interrupted.

[0024] The DC / DC conversion circuit 117 is, for example, a repurposed energy storage device that was installed in an electric vehicle. The DC / DC conversion circuit 117 is located between the electrically connected SMR 116 and PCU 101. The DC / DC conversion circuit 117 is configured to transform the output voltage of the energy storage stack 112 and output it to the PCU 101 according to commands from the EM server 20. The DC / DC conversion circuit 117 is also configured to transform the DC power input from the PCU 101 and output it to the energy storage stack 112 according to commands from the EM server 20.

[0025] JB118 is positioned between the electrically connected DC / DC conversion circuit 117 and the PCU 101. JB118 incorporates various components, such as relays and fuses (not shown), and is configured to electrically connect these components.

[0026] The second energy storage device 120, like the first energy storage device 110, includes a battery pack 121, an SMR 126, a DC / DC conversion circuit 127, and a JB 128. The battery pack 121 includes an energy storage stack 122, a monitoring unit 124, and a battery ECU 125. The energy storage stack 122 has a plurality of energy storage cells 123.

[0027] In the above embodiment, the EM server 20 is an example of the "system control unit" of this disclosure. The energy storage cell 113 is an example of the "first battery" of this disclosure. The energy storage cell 123 is an example of the "second battery" of this disclosure. The fuse built into JB118 is an example of the "first fuse" of this disclosure. The fuse built into JB128 is an example of the "second fuse" of this disclosure.

[0028] The stationary energy storage system 100 in the energy management system 1 of the above embodiment includes a PCS 101 and a plurality of energy storage devices 104. The PCS 101 has a DC / AC conversion circuit (not shown). The DC / AC conversion circuit converts the DC power supplied from the plurality of energy storage devices 104 into AC current in response to a command from the EM server 20 and outputs it to the power grid PG (reverse power flow). On the other hand, the DC / AC conversion circuit converts the AC power supplied from the power grid PG into DC current in response to a command from the EM server 20 and outputs it to the plurality of energy storage devices 104 (forward power flow). The stationary energy storage system 100 provides power supply and demand adjustment capabilities to the power grid PG. <Control flow of an energy management system> Next, the control flow of the energy management system 1 will be explained with reference to Figure 2. The control flow shown in Figure 2 illustrates an example in which the first energy storage device 110 and the second energy storage device 120 in the stationary energy storage system 100 perform the power supply and demand adjustment function in the energy management system 1.

[0029] In step S10 shown in Figure 2, the TSO server 10 detects the status of the power grid PG. The status of the power grid PG includes the actual situation of power supply and demand, and the trend in the amount of power generated and supplied. Depending on the status of the power grid PG, the TSO server 10 determines that energy management is necessary. After that, the processing of the TSO server 10 proceeds to step S15.

[0030] In step S15, the TSO server 10 requests energy management from the EM server 20. Subsequently, the TSO server 10 terminates processing of the energy management system.

[0031] In step S20, the EM server 20 checks whether it has received an energy management request signal from the TSO server 10. If it has received an energy management request signal (Yes in step S20), the EM server 20 proceeds to step S25. If it has not received an energy management request signal (No in step S20), the EM server 20 processes step S20 again.

[0032] In step S25, the EM server 20 requests the battery ECU 115 and battery ECU 125 to transmit electrical characteristic information. The EM server 20 then proceeds to step S40.

[0033] In step S30, the battery ECU 115 checks whether it has received a request to transmit electrical characteristic information. If it has received a request to transmit electrical characteristic information (Yes in step S30), the battery ECU 115 proceeds to step S31. If it has not received a request to transmit electrical characteristic information (No in step S30), the battery ECU 115 processes step S30 again.

[0034] In step S31, the battery ECU 115 transmits electrical characteristic information, such as SOH and SOC, for each of the multiple energy storage cells 113 to the EM server 20. After that, the battery ECU 115 proceeds to step S60.

[0035] In step S35, the battery ECU 125 checks whether it has received a request to transmit electrical characteristic information. If it has received a request to transmit electrical characteristic information (Yes in step S35), the battery ECU 125 proceeds to step S36. If it has not received a request to transmit electrical characteristic information (No in step S35), the battery ECU 125 processes step S35 again.

[0036] In step S36, the battery ECU 125 transmits electrical characteristic information, such as SOH and SOC, for each of the multiple energy storage cells 123 to the EM server 20. After that, the battery ECU 125 proceeds to step S65.

[0037] In step S40, the EM server 20 checks whether it has received electrical characteristic information from both the battery ECU 115 and the battery ECU 125. If it has received electrical characteristic information (Yes in step S40), the EM server 20 proceeds to step S45. If it has not received electrical characteristic information (No in step S40), the EM server 20 processes step S40 again.

[0038] In step S45, the EM server 20 obtains the State of Health (SOH) of multiple energy storage cells 113 and multiple energy storage cells 123 from the acquired electrical characteristic information. After that, the EM server 20 proceeds to step S50.

[0039] In step S50, the EM server 20 determines the distribution ratio of charge and discharge current between energy storage cell 113 and energy storage cell 123. More specifically, the EM server 20 determines the distribution ratio for distributing the charge current supplied from the power grid PG to energy storage cell 113 and energy storage cell 123, or the distribution ratio for the discharge current supplied to the power grid PG, which is handled by energy storage cell 113 and energy storage cell 123. The distribution ratio of charge and discharge current is determined based on the State of Health (SOH) of the multiple energy storage cells 113 and the multiple energy storage cells 123. For example, if the SOH of the multiple energy storage cells 113 is higher than the SOH of the multiple energy storage cells 123, the EM server 20 distributes a larger charge and discharge current to energy storage cell 113 than to energy storage cell 123. Here, the SOH of the multiple energy storage cells 113 may be determined by the SOH of a specific energy storage cell 113 among the multiple energy storage cells 113, or by the average value of the SOH of the multiple energy storage cells 113. The same applies to the State of Health (SOH) of multiple energy storage cells 123. Furthermore, the distribution ratio of the charge and discharge current to be allocated to energy storage cells 113 and 123 is, for example, the ratio of the SOH of multiple energy storage cells 113 to the SOH of multiple energy storage cells 123. After determining the distribution ratio of the charge and discharge current, the EM server 20 proceeds to the process in step S55.

[0040] The State of Health (SOH) of energy storage cell 113 is an example of the "first SOH" in this disclosure. The SOH of energy storage cell 123 is an example of the "second SOH" in this disclosure.

[0041] In step S55, the EM server 20 transmits current control signals to the battery ECU 115 and battery ECU 125. The current control signals are signals for controlling the battery ECU 115 and battery ECU 125 based on the distribution ratio determined in step S50, and include information on the current flowing through the energy storage cell 113 and energy storage cell 123. After that, the EM server 20 terminates processing of the energy management system 1.

[0042] In step S60, the battery ECU 115 checks whether it has received a current control signal from the EM server 20. If it has received a current control signal (Yes in step S60), the battery ECU 115 proceeds to step S61. If it has not received a current control signal (No in step S60), the battery ECU 115 processes step S60 again.

[0043] In step S61, the battery ECU 115 starts current control based on the current control signal sent to the battery ECU 115 from the EM server 20. More specifically, the battery ECU 115 instructs the DC / DC conversion circuit 117 to control the current supplied from the PCU 101 to the energy storage cell 113 to a current determined by the current control signal. Alternatively, the battery ECU 115 instructs the DC / DC conversion circuit 117 to control the current supplied from the energy storage cell 113 to the PCU 101 to a current determined by the current control signal. After that, the battery ECU 115 terminates processing by the energy management system 1.

[0044] In step S65, the battery ECU 125 checks whether it has received a current control signal from the EM server 20. If it has received a current control signal (Yes in step S65), the battery ECU 125 proceeds to step S66. If it has not received a current control signal (No in step S65), the battery ECU 125 processes step S65 again.

[0045] In step S66, the battery ECU 125 starts current control based on the current control signal sent to the battery ECU 125 from the EM server 20. More specifically, the battery ECU 125 instructs the DC / DC conversion circuit 127 to control the current supplied from the PCU 101 to the energy storage cell 123 to the current specified by the current control signal. Alternatively, the battery ECU 125 instructs the DC / DC conversion circuit 127 to control the current supplied from the energy storage cell 123 to the PCU 101 to the current specified by the current control signal. After that, the battery ECU 125 terminates processing by the energy management system 1.

[0046] In embodiments of this disclosure, the control flow shown in Figure 2 illustrates an example in which the first energy storage device 110 and the second energy storage device 120 in the stationary energy storage system 100 perform the power supply and demand adjustment function in the energy management system 1, but this disclosure is not limited thereto. The number of energy storage devices 104 that perform the power supply and demand adjustment function in the energy management system 1 is not limited. <Example of charging current distribution> Figure 3 shows an example of distributing the charging current supplied from the PCU 101 to each of the multiple energy storage devices 104. Note that the example of distributing the discharge current is substantially the same as in Figure 3, so the explanation of the example in which each of the multiple energy storage devices 104 shares the discharge current is omitted. In Figure 3, the first energy storage device 110, the second energy storage device 120, the third energy storage device 130, and the fourth energy storage device 140 perform the power supply and demand adjustment function in the stationary energy storage system 100. Figure 3 shows the charging current flowing through each energy storage cell in the multiple energy storage devices 104 when the total charging current supplied from the PCU 101 to the multiple energy storage devices 104 is 130A. In Figure 3, the SOH of the multiple energy storage cells 113 in the first energy storage device 110 is 80%. The SOH of the multiple energy storage cells 123 in the second energy storage device 120 is 60%. The state of health (SOH) of the multiple energy cells in the third energy storage device 130 is 60%. The state of health (SOH) of the multiple energy cells in the fourth energy storage device 140 is also 60%. Similar to the process shown in step S50 of Figure 2, the EM server 20 distributes the total charging current 130A according to the ratio of the SOH of each energy cell in the multiple energy storage devices 104. Specifically, the EM server 20 controls the battery ECU to supply 40A to the energy cell 113 of the first energy storage device 110, and 30A to each of the energy cells in the second energy storage device 120, the third energy storage device 130, and the fourth energy storage device 140.

[0047] In the embodiment shown in Figure 2, the EM server 20 compares the State of Health (SOH) of multiple energy storage cells 113 with the SOH of multiple energy storage cells 123. When the SOH of multiple energy storage cells 113 is higher than that of multiple energy storage cells 123, the EM server 20 controls the battery ECUs 115 and 125 to distribute a higher charge / discharge current to energy storage cells 113 than to energy storage cells 123. In this way, the EM server 20 controls the battery ECUs of multiple energy storage devices 104 of the stationary energy storage system 100 according to the SOH, thereby delaying the maintenance timing of energy storage devices that have deteriorated energy storage cells. This makes it possible to synchronize the maintenance timing of multiple energy storage devices 104 and suppress sporadic maintenance of energy storage devices. Consequently, the maintenance frequency of the stationary energy storage system 100 can be reduced.

[0048] In the above embodiment, the EM server 20 is shown to distribute a larger charge / discharge current to the energy storage cells 113 than to the energy storage cells 123 when the SOH of the energy storage cells 113 is higher than the SOH of the energy storage cells 123. However, the disclosure is not limited to this. For example, the EM server 20 may distribute a larger charge / discharge current to the energy storage cells 113 than to the energy storage cells 123 when the SOH of the energy storage cells 113 is lower than the SOH of the energy storage cells 123. This further ensures the lifespan of energy storage cells with a margin in SOH. Consequently, the maintenance frequency of the stationary energy storage system 100 can be reduced. <Example 1> In the embodiment shown in Figure 2, the EM server 20 distributes the charge and discharge current to the multiple energy storage devices 104 according to the State of Health (SOH) of the multiple energy storage cells of the multiple energy storage devices 104, but the disclosure is not limited thereto. For example, the EM server 20 may distribute the charge and discharge current to the multiple energy storage devices 104 according to the integrated value of the charge and discharge current that has flowed through the fuses built into the JBs of the multiple energy storage devices 104.

[0049] In Modification 1, the battery ECU 115 further performs a charge / discharge current integration process, which integrates the charge / discharge currents acquired from the monitoring unit 114 at predetermined time intervals. The charge / discharge current integration value obtained by the processing of the battery ECU 115 is called the first charge / discharge current integration value. The battery ECU 115 stores the information of the first charge / discharge current integration value in a storage unit (not shown) that the battery ECU 115 has. The same applies to the battery ECU 125. That is, the battery ECU 125 stores the information of the acquired second charge / discharge current integration value in a storage unit (not shown) that the battery ECU 125 has. <Control flow of the energy management system according to modified example 1> Figure 4 shows the control flow of the energy management according to Modification 1. Steps S10 to S30 and S35 shown in Figure 4 are the same as the steps shown in Figure 2, so their explanation is omitted.

[0050] In step S31A, the battery ECU 115 transmits electrical characteristic information to the EM server 20. In the modified example 1, the electrical characteristic information further includes information on the first charge / discharge current integrated value. After that, the processing of the battery ECU 115 proceeds to step S60.

[0051] In step S36A, the battery ECU 125 transmits electrical characteristic information to the EM server 20. In the modified example 1, the electrical characteristic information further includes information on the second charge / discharge current integrated value. After that, the processing of the battery ECU 125 proceeds to step S65.

[0052] Step S40 is identical to Step S40 shown in Figure 2, so its explanation will be omitted.

[0053] In step S45A, the EM server 20 obtains the first charge / discharge current integrated value and the second charge / discharge current integrated value included in the acquired electrical characteristic information. After that, the EM server 20 proceeds to step S50A.

[0054] In step S50A, the EM server 20 determines the distribution ratio of charge and discharge current between energy storage cells 113 and 123. More specifically, the EM server 20 determines the distribution ratio for distributing the charge current supplied from the power grid PG to energy storage cells 113 and 123, or the distribution ratio for the discharge current supplied to the power grid PG, which is handled by energy storage cells 113 and 123. The distribution ratio of charge and discharge current is determined based on the first integrated charge and discharge current value and the second integrated charge and discharge current value. For example, if the first integrated charge and discharge current value is greater than the second integrated charge and discharge current value, the EM server 20 distributes a larger charge and discharge current to energy storage cell 113 than to energy storage cell 123. The distribution ratio of charge and discharge current to be distributed between energy storage cells 113 and 123 is, for example, the ratio of the first integrated charge and discharge current value to the second integrated charge and discharge current value. After determining the distribution ratio of the charge and discharge currents, the EM server 20 proceeds to step S55.

[0055] The processes from step S55 to step S66 are identical to those shown in Figure 2, so their explanation will be omitted.

[0056] In the embodiment according to Modification 1 shown in Figure 4, the EM server 20 determines the charge and discharge currents flowing to the energy storage cells 113 and 123 based on the first charge and discharge current integrated value and the second charge and discharge current integrated value. The charge and discharge current integrated value loaded onto the fuse built into the JB118 of the first energy storage device 110 is equal to the first charge and discharge current integrated value. The same applies to the fuse built into the JB128 of the second energy storage device 120. For example, if the first charge and discharge current integrated value is greater than the second charge and discharge current integrated value, the EM server 20 distributes a larger charge and discharge current to the energy storage cell 113 than to the energy storage cell 123. This further ensures the lifespan of the fuse built into the JB, which has a margin in the charge and discharge current integrated value. Generally, fuses have a defined energizing lifespan when the rated current is continuously flowing through them. Here, the value obtained by multiplying the rated current by the energizing lifespan is defined as the rated current integrated value. When the cumulative charge and discharge current value of the fuse reaches the rated current value, the fuse will experience fatigue rupture and require replacement. By suppressing the current flowing through the fuse, the cumulative charge and discharge current value of the fuse can be suppressed. Consequently, by ensuring the lifespan of the fuse, the maintenance frequency of the stationary energy storage system 100 can be reduced.

[0057] In the above embodiment, an example was shown in which the EM server 20 distributes a larger charge / discharge current to the energy storage cell 113 than to the energy storage cell 123 when the integrated value of the first charge / discharge current is greater than the integrated value of the second charge / discharge current. However, the disclosure is not limited to this example.

[0058] Firstly, if the integrated value of the first charge-discharge current is less than the integrated value of the second charge-discharge current, the EM server 20 may distribute a larger charge-discharge current to the energy storage cell 113 than to the energy storage cell 123. This allows the maintenance timing of deteriorated fuses to be delayed. This makes it possible to synchronize the replacement timing of fuses in each of the multiple energy storage devices 104, and prevents the sporadic occurrence of fuse replacement times in the energy storage devices. In turn, it is possible to reduce the maintenance frequency of the stationary energy storage system 100.

[0059] Secondly, if the EM server 20's cumulative charge / discharge current value exceeds the fuse replacement threshold, it may distribute a charge / discharge current to the energy storage cells of the energy storage device 104 having a fuse that is less than or equal to a current that does not substantially affect the fuse's lifespan. The replacement threshold is any cumulative charge / discharge current value that is less than or equal to the rated charge / discharge current value. A current that does not substantially affect the fuse's lifespan is, for example, 10% or less of the fuse's rated current. This reduces the frequency of maintenance of the stationary energy storage system 100 related to fuse replacement.

[0060] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0061] 1 Energy management system, 10 TSO server, 20 EM server, 21 Processor, 22 Memory device, 100 Stationary energy storage system, 101 PCU, 102 Circuit breaker, 103 Circuit breaker, 104 Energy storage device, 110 First energy storage device, 111 Battery pack, 112 Energy storage stack, 113 Energy storage cell, 114 Monitoring unit, 115 Battery ECU, 116 SMR, 117 DC / DC conversion circuit, 120 Second energy storage device, 121 Battery pack, 122 Energy storage stack, 123 Energy storage cell, 124 Monitoring unit, 125 Battery ECU, 126 SMR, 127 DC / DC conversion circuit, 130 Third energy storage device, 140 Fourth energy storage device.

Claims

1. A first energy storage device and a second energy storage device are electrically connected to the power grid. The system comprises a first energy storage device and a system control unit that controls the second energy storage device, The first energy storage device has a first battery, The second energy storage device has a second battery, The system control unit acquires the first state of overheating (SOH) of the first battery and the second state of overheating (SOH) of the second battery, and if the first SOH is higher than the second SOH, it distributes a higher charge / discharge current to the first battery than to the second battery, in a stationary energy storage system.

2. A first energy storage device and a second energy storage device are electrically connected to the power grid. The system comprises a first energy storage device and a system control unit that controls the second energy storage device, The first energy storage device has a first battery, The second energy storage device has a second battery, The system control unit acquires the first state of overheardiness (SOH) of the first battery and the second state of overheardiness (SOH) of the second battery, and when the first SOH is lower than the second SOH, it distributes a larger charge / discharge current to the first battery than to the second battery, in a stationary energy storage system.

3. A first energy storage device and a second energy storage device are electrically connected to the power grid. The system comprises a first energy storage device and a system control unit that controls the second energy storage device, The first energy storage device comprises a first battery and a first fuse electrically connected to the first battery. The second energy storage device comprises a second battery and a second fuse electrically connected to the second battery. The system control unit acquires a first integrated charge / discharge current value for the first battery and a second integrated charge / discharge current value for the second battery, and when the first integrated charge / discharge current value is greater than the second integrated charge / discharge current value, it distributes a larger charge / discharge current to the first battery than to the second battery, in a stationary energy storage system.

4. A first energy storage device and a second energy storage device are electrically connected to the power grid. The system comprises a first energy storage device and a system control unit that controls the second energy storage device, The first energy storage device comprises a first battery and a first fuse electrically connected to the first battery. The second energy storage device comprises a second battery and a second fuse electrically connected to the second battery. The system control unit acquires a first integrated charge / discharge current value for the first battery and a second integrated charge / discharge current value for the second battery, and when the first integrated charge / discharge current value is less than the second integrated charge / discharge current value, it distributes a larger charge / discharge current to the first battery than to the second battery, in a stationary energy storage system.

5. A power storage device electrically connected to the power grid, The system includes a system control unit that controls the aforementioned energy storage device, The energy storage device comprises a battery and a fuse electrically connected to the battery. A stationary energy storage system comprising: a system control unit that acquires the integrated charge and discharge current value of the battery, and, if the integrated charge and discharge current value exceeds the fuse replacement threshold, distributes a charge and discharge current to the battery that is less than or equal to a current that does not affect the lifespan of the fuse.

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