Stationary energy storage system

Abstract

To provide a stationary power storage system capable of performing energy management with high accuracy using a power storage device.SOLUTION: A stationary power storage system comprises a plurality of power storage devices connected in parallel with each other, a relay and a current sensor provided for each of the plurality of power storage devices, and a control device that controls a current value of each of the power storage devices. The control device is configured to select, from among the plurality of power storage devices, a predetermined number of power storage devices as learning targets and select one or more power storage devices other than the learning targets as control targets used for energy management (S31). The control device is configured to interrupt current by the relays corresponding to the learning targets (S23), acquire output values from the current sensors corresponding to the learning targets (S26), and correct detection errors of the current sensors corresponding to the learning targets on the basis of the acquired output values (S27).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a stationary power storage system.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2012-113856 (Patent Document 1) discloses a vehicle including a battery pack in which a plurality of battery stacks are connected in parallel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the vehicle described in Patent Document 1 above, a system main relay (SMR) is provided for each of a plurality of battery stacks (power storage devices). In such a vehicle, in order to control the current value for each battery stack, it is conceivable to provide a current sensor for each of the battery stacks connected in parallel. In order to perform current control with high accuracy, it is desirable to perform output correction (for example, offset correction) of each current sensor while checking the output value when no current is flowing through each current sensor. In a vehicle, for example, when the start switch is turned off at the end of travel, it is considered that the SMR corresponding to each battery stack becomes in an open state and no current flows through each battery stack. For this reason, the vehicle may be able to acquire the output value when no current is flowing through each current sensor after the end of travel. Note that the start switch of a vehicle is generally referred to as a "power switch" or an "ignition switch" or the like.

[0005] However, in stationary energy storage systems that use energy storage devices for energy management, it is required that the energy storage devices be kept energized for energy management purposes. When the energy storage devices are disconnected, they cannot be used for energy management. Therefore, in the case of the above-mentioned stationary energy storage systems, there is a problem that the output correction of the current sensor installed in the energy storage device becomes insufficient, and the accuracy of the current control of the energy storage device tends to decrease.

[0006] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide a stationary energy storage system that can perform energy management with high precision using an energy storage device. [Means for solving the problem]

[0007] A stationary energy storage system according to one embodiment of the present disclosure comprises a plurality of energy storage devices, a current sensor provided in each of the plurality of energy storage devices, and a control device that controls the current value of each of the plurality of energy storage devices. Each of the plurality of energy storage devices is configured to be switchable between energizing and shutting off according to a command from the control device. The control device selects an energy storage device from the plurality of energy storage devices to be used for energy management, shuts off the current to the energy storage devices that were not selected, controls the current value of the selected energy storage device for energy management, and, while energy management is being performed, obtains the output value of the current sensor corresponding to the energy storage device that was not selected when no current is flowing. [Effects of the Invention]

[0008] This disclosure makes it possible to provide a stationary energy storage system that can perform energy management with high precision using energy storage devices. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows a schematic configuration of the energy management system according to the embodiment of the disclosure. [Figure 2] This is a flowchart showing an energy management method according to an embodiment of the present disclosure. [Figure 3] This diagram illustrates an example of energy management required by a server that manages the power grid. [Figure 4] This figure shows a modified version of the energy management method shown in Figure 2. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described in detail 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.

[0011] Figure 1 is a diagram showing a schematic configuration of an energy management system according to an embodiment of the present disclosure. Referring to Figure 1, the energy management system according to this embodiment comprises a power storage system 100 and a server 200 (EM server) and performs energy management of a power grid PG. Server 200 is configured to communicate with a server 300 (TSO server) that manages the power grid PG. "EM" stands for Energy Management. "TSO" stands for Transmission System Operator. A power grid PG is a power network constructed by power plants and transmission and distribution equipment. Server 300 is equipped with a processor and memory device and monitors the status of the power grid PG (e.g., supply and demand balance and frequency) and requests energy management from Server 200. This maintains the power grid PG in a state where it can stably supply high-quality power. A power grid PG is, for example, an AC grid provided by a power company.

[0012] The energy storage system 100 comprises a DC / AC conversion circuit 10, N SMRs 21-1 to 21-N (referred to as "SMR21" unless otherwise specified), N DC / DC conversion circuits 22-1 to 22-N (referred to as "DC / DC conversion circuit 22" unless otherwise specified), and N battery packs 23-1 to 23-N (referred to as "battery pack 23" unless otherwise specified). "SMR" stands for System Main Relay. SMR21, DC / DC conversion circuit 22, and battery pack 23 correspond to examples of "relay," "power conversion circuit," and "energy storage device" as described herein, respectively. The energy storage system 100 is controlled by a server 200. N is, for example, about 50. However, N may be any natural number greater than or equal to 2, and may be greater than or equal to 100. The energy storage system 100 may further include a leakage current detector (for example, a circuit breaker that automatically cuts off the current when it detects a leakage current), which is not shown.

[0013] The battery packs 23-1 to 23-N are connected in parallel to each other. Each of the battery packs 23-1 to 23-N is equipped with an SMR 21-1 to 21-N and a DC / DC conversion circuit 22-1 to 22-N. Each of the battery packs 23-1 to 23-N is configured to switch between energized and disconnected according to a command from the server 200. Current can flow through the energized battery pack 23. On the other hand, no current flows through the disconnected battery pack 23. In this embodiment, the SMR 21 is configured to switch between energized and disconnected the corresponding battery pack 23 according to a command from the server 200. The SMR 21 is provided in the circuit connecting the DC / AC conversion circuit 10 and the DC / DC conversion circuit 22. The SMR 21 is, for example, an electromagnetic mechanical relay. The circuit is switched between disconnected and connected by opening and closing the SMR 21.

[0014] The DC / AC conversion circuit 10 is configured to output AC power to the power grid PG according to a command from the server 200. The DC / AC conversion circuit 10 is also configured to convert the AC power input from the power grid PG into DC power and output it to each of the DC / DC conversion circuits 22-1 to 22-N. The DC / DC conversion circuit 22 is configured to transform the output voltage of the corresponding battery pack 23 according to a command from the server 200. The DC / DC conversion circuit 22 is also configured to transform the DC power input from the DC / AC conversion circuit 10 and output it to the corresponding battery pack 23 according to a command from the server 200.

[0015] More specifically, when DC power is input from the battery pack 23 to the corresponding DC / DC conversion circuit 22, the DC / DC conversion circuit 22 outputs DC power to the DC / AC conversion circuit 10 according to the command from the server 200. The DC / AC conversion circuit 10 then outputs AC power to the power grid PG according to the command from the server 200 (reverse power flow). On the other hand, when AC power is input from the power grid PG to the DC / AC conversion circuit 10 (forward power flow), the DC / AC conversion circuit 10 outputs DC power to each of the DC / DC conversion circuits 22-1 to 22-N according to the command from the server 200. Each of the DC / DC conversion circuits 22-1 to 22-N then outputs DC power to the corresponding battery pack 23 according to the command from the server 200. The output power of each DC / DC conversion circuit may be the same or different. The server 200 may determine the output power of each DC / DC conversion circuit to match the corresponding battery pack 23.

[0016] The server 200 comprises a processor 210 and a storage device 220. An example of the processor 210 is a CPU (Central Processing Unit). The storage device 220 is configured to store stored information. The battery packs 23-1 to 23-N included in the energy storage system 100 are registered in the server 200. The storage device 220 stores information about each battery pack (e.g., specifications, control information, and sensor information), distinguished by the battery pack identification information (battery ID). The control information includes information for the server 200 to individually control the SMR 21 and DC / DC conversion circuit 22 corresponding to each battery pack. The sensor information includes a correction coefficient for the sensor output.

[0017] The battery pack 23 includes a battery 231, a battery ECU (Electronic Control Unit) 232, a current sensor 233a for detecting the current flowing through the battery 231, a voltage sensor 233b for detecting the voltage of the battery 231, and a temperature sensor 233c for detecting the temperature of the battery 231. The detection results from each sensor are input to the battery ECU 232. The battery ECU 232 includes a processor and memory device (not shown) and records the detection results from each sensor in the memory device, linked to the detection time. The battery ECU 232 also calculates the State of Charge (SOC) of the battery 231 from the detection results from each sensor and records the SOC of the battery 231 in the memory device, linked to the time. SOC represents the remaining charge, for example, as the ratio of the current charge to the charge when fully charged. The battery ECU 232 outputs the data recorded in the memory device to the server 200 in response to a request from the server 200.

[0018] The battery ECU 232 controls the SMR 21 and the DC / DC conversion circuit 22 respectively according to commands from the server 200. The battery ECU 232 converts the commands from the server 200 into control signals for the SMR 21 and the DC / DC conversion circuit 22 respectively. The server 200 controls the SMR 21-1 to 21-N and the DC / DC conversion circuits 22-1 to 22-N respectively via the battery ECU 232.

[0019] The battery 231 may be a single secondary battery or a battery pack formed by electrically connecting a plurality of secondary batteries. The battery packs 23-1 to 23-N may include the same type of secondary batteries as each other or may include different types of secondary batteries from each other. Examples of secondary batteries include lithium-ion batteries and nickel-metal hydride batteries. The secondary battery may be any of a liquid secondary battery, a semi-solid secondary battery, and a all-solid-state secondary battery.

[0020] The battery pack 23 corresponds to a stationary power storage device. A battery pack (including a drive battery and a battery ECU) used in an electric vehicle may be reused as the battery pack 23. Also, an inverter and a DC / DC converter used in an electric vehicle may be reused as the DC / AC conversion circuit 10 and the DC / DC conversion circuit 22, respectively. The power storage system 100 functions as a stationary ESS (Energy Storage System). In this embodiment, the server 200 and the battery ECU 232 function as the "control device" according to the present disclosure.

[0021] By the way, in order for the server 200 to perform current control of each of the battery packs 23-1 to 23-N with high accuracy, it is desirable for the server 200 to perform output correction (for example, offset correction) of each current sensor while checking the output value when no current is flowing through each current sensor 233a of the battery packs 23-1 to 23-N. However, in a stationary power storage system, it is required to keep the power storage device in an energized state for energy management. A power storage device in a cut-off state cannot be used for energy management. For this reason, there is a problem that the output correction of the current sensor provided in the power storage device becomes insufficient and the accuracy of the current control of the power storage device tends to decrease.

[0022] Therefore, in this embodiment, while the server 200 is executing energy management, it obtains an output value (hereinafter referred to as "zero output value") when no current is flowing through the current sensor 233a corresponding to the battery pack 23 that is not used for energy management, and performs output correction (correction of detection error) of the current sensor 233a based on the obtained zero output value. Thereby, it becomes possible to perform energy management with high accuracy using the battery pack 23. Further, the server 200 controls the power storage system 100 so that energy management of the power grid PG in response to a request from the server 300 that manages the power grid PG is executed. The server 200 constantly accepts requests from the server 300.

[0023] FIG. 2 is a flowchart showing the energy management method according to this embodiment. "S" in the flowchart means a step.

[0024] Referring to FIG. 2, the server 300 periodically executes the processing flow of S11 to S12. In S11, the server 300 detects the state of the power grid PG (for example, supply-demand situation and frequency). In subsequent S12, the server 300 requests the server 200 to perform energy management for improving the state of the power grid PG. Specifically, the server 300 transmits an EM request signal to the server 200. The EM request signal indicates the content of the requested energy management (for example, charging power, discharging power, charging energy amount, or discharging energy amount). When the processing of S12 is executed, the processing returns to the first step (S11).

[0025] Server 200 initiates the processing flow S21-S27 each time it receives an EM request signal from Server 300. In S21, Server 200 determines whether the input / output capability requested by the EM request signal is lower than the input / output capability of the energy storage system 100. Specifically, if the charging power or discharging power requested by the EM request signal is a value that the energy storage system 100 can charge or discharge even if at least one of the battery packs 23-1 to 23-N is turned off, S21 determines YES and the process proceeds to S22. If the charging power or discharging power requested by the EM request signal is a value that the energy storage system 100 cannot achieve unless all of the battery packs 23-1 to 23-N are energized, or if the energy storage system 100 cannot achieve even if all of the battery packs are energized, S21 determines NO and the process proceeds to S24. In S24, Server 200 energizes all of the battery packs 23-1 to 23-N. Specifically, server 200 connects all SMR21-1 to 21-N. Then, the process proceeds to S25.

[0026] In S22, the server 200 selects one or more battery packs (hereinafter referred to as "EM-controlled targets") from among the battery packs 23-1 to 23-N to be used for energy management. The server 200 determines the EM-controlled targets so that the energy storage system 100 can charge or discharge the charging power or discharging power requested by the EM request signal. The server 200 may also select the number of battery packs (EM-controlled targets) required for energy management, prioritizing those with the shortest elapsed time since the most recent learning (output correction) of the current sensor 233a. Furthermore, if the EM request signal requests a charging power amount or a discharging power amount, the server 200 may determine the number of battery packs to be included in the EM-controlled targets based on the requested charging power amount or discharging power amount. If there is a variation in SOC among the battery packs 23-1 to 23-N, the server 200 may select the number of battery packs (EM-controlled targets) required for energy management based on the SOC of each battery pack.

[0027] Figure 3 illustrates an example of energy management required by server 300. Hereafter, requests for charging power or discharging power will be referred to as "power requests," and requests for charging energy or discharging energy will be referred to as "energy requests."

[0028] A power request may also be an energy management request to suppress fluctuations in the power output from power plants in the power grid PG. Power plants may include naturally fluctuating power sources whose output varies depending on weather conditions. Server 200 may receive a power request from Server 300 to bring the actual power output L12 in the power grid PG closer to the target value L11. An energy request may also be an energy management request to adjust the supply and demand balance of the power grid PG. Server 200 may receive an energy request from Server 300 to match the power demand L21 and power supply L22 of the power grid PG.

[0029] Battery packs 23-1 to 23-N may include a first battery pack (first energy storage device) containing an output-type battery (first battery) and a second battery pack (second energy storage device) containing a capacity-type battery (second battery). The first and second battery packs may each include a battery pack (battery 231) in which multiple output-type batteries and multiple capacity-type batteries are electrically connected. The rated output (W) of the output-type battery is greater than the rated output (W) of the capacity-type battery. The rated output corresponds to the maximum discharge power indicated by the battery manufacturer. The capacity (Wh) of the capacity-type battery is greater than the capacity (Wh) of the output-type battery. The battery capacity corresponds to the amount of electricity stored in a fully charged battery. The power density of the output-type battery may be higher than the power density of the capacity-type battery. The energy density of the capacity-type battery may be higher than the energy density of the output-type battery. In Figure 3, line L1 shows the change (slope) in the output power (W) and capacity (Wh) of the energy storage system 100 when the number of energized output-type batteries is increased or decreased. Line L2 shows the change (slope) in the output power (W) and capacity (Wh) of the energy storage system 100 when the number of energized capacity-type batteries is increased or decreased.

[0030] When server 200 receives only an energy request, it prioritizes selecting the capacity-type battery (second battery pack) over the output-type battery (first battery pack) as the target for EM control, and when it receives only a power request, it prioritizes selecting the output-type battery (first battery pack) over the capacity-type battery (second battery pack) as the target for EM control. Furthermore, as shown in Figure 3, when server 200 receives both an energy request with a required Wh of X and a power request with a required W of Y, it selects the target for EM control in such a way that the energy storage system 100 has the input / output capability to meet both of these energy and power requests.

[0031] The server 200 can individually adjust the output voltage of each battery pack included in the EM-controlled system using the DC / DC conversion circuit 22 (power conversion circuit) of each battery pack. Therefore, the server 200 can equalize the output voltage of each battery pack included in the EM-controlled system by individually adjusting the output voltage of multiple types of energy storage devices (battery packs 23-1 to 23-N) with different battery types using the DC / DC conversion circuit 22. Such an energy storage system 100 makes it easy to use multiple types of batteries. According to the configuration shown in Figure 1, for example, it becomes easier to realize a stationary energy storage system that performs energy management with high precision using used batteries.

[0032] Referring again to Figure 2, in S23, the server 200 energizes each battery pack included in the EM-controlled targets (each battery pack selected in S22) and cuts off the current to each battery pack not selected in S22 (hereinafter referred to as "learning targets"). Specifically, the server 200 connects (closes) the SMR21 corresponding to the EM-controlled targets and disconnects (opens) the SMR21 corresponding to the learning targets.

[0033] In S25, the server 200 performs energy management as requested by the server 300 using each battery pack that was energized in S23 or S24. Specifically, the server 200 controls the current value of each energized battery pack for energy management purposes based on the values ​​detected by the current sensor 233a of each energized battery pack. If a correction coefficient is set for the output of the current sensor 233a, the server 200 detects the current value of the battery pack 23 (battery 231) based on the output value of the current sensor 233a corrected by the correction coefficient. While performing energy management, the server 200 may perform SOC equalization in each energized battery pack.

[0034] In the following S26, the server 200 learns the detection error of the current sensor 233a of each battery pack included in the learning target. Specifically, the server 200 obtains a zero output value (output value when no current is flowing) for the current sensor 233a of each battery pack included in the learning target, and records the error (detection error) of the zero output value compared to the correct sensor output value in the storage device 220.

[0035] In the following S27, the server 200 performs output correction (detection error correction) on the current sensors 233a of each battery pack included in the learning target so that the detection error acquired in S26 is reduced. For example, when no current is flowing through the battery 231 of battery pack 23 (learning target), the server 200 performs output correction so that the output value (detection value) of the current sensor 233a corresponding to the battery 231 shows 0A. The output correction may also be offset correction. The server 200 may determine a correction coefficient for the output of the current sensor 233a based on the zero output value. Once the processing in S27 is executed, the processing flow from S21 to S27 is completed.

[0036] As described above, the energy management method according to this embodiment includes the processes shown in Figure 2. Each process is executed by one or more processors executing programs stored in one or more memories. However, these processes may be executed by hardware (electronic circuits) instead of software.

[0037] The stationary energy storage system according to this embodiment comprises a plurality of energy storage devices (battery packs 23-1 to 23-N), a current sensor 233a provided on each of the plurality of energy storage devices, and a control device (server 200 and battery ECU 232) that controls the current value of each of the plurality of energy storage devices. Each of the plurality of energy storage devices is configured to switch between energizing and shutting off according to a command from the control device. The control device selects an energy storage device to be used for energy management from among the plurality of energy storage devices (S22), shuts off the current of the energy storage devices that were not selected (S23), controls the current value of the selected energy storage device for energy management (S25), and, while energy management is being performed, obtains the output value of the current sensor corresponding to the energy storage device that was not selected when no current is flowing (S26).

[0038] According to the above configuration, energy management can be performed using the selected energy storage device. Furthermore, during energy management, the output value of the current sensor corresponding to the unselected energy storage device can be obtained when no current is flowing. This makes it possible to correct the output of the current sensor (correct the detection error) based on the output value of the current sensor when no current is flowing. In this way, the above stationary energy storage system can perform energy management with high accuracy using the energy storage device.

[0039] In this embodiment of the stationary energy storage system, the control device (server 200 and battery ECU 232) interrupts the current using a relay (SMR21) corresponding to the learning target (the energy storage device that was not selected) during the execution of energy management (S23), and corrects the detection error of the current sensor 233a corresponding to the learning target based on the zero output value (the output value of the current sensor 233a when no current is flowing) (S27). With this configuration, it becomes possible to select any energy storage device (EM control target) from among multiple energy storage devices and appropriately interrupt the current of the unselected energy storage devices (learning targets) using the relay. However, the server 200 may also put the battery pack 23 into an interrupted state (a state in which no current flows) by controlling the DC / DC conversion circuit 22 instead of the SMR21.

[0040] In the stationary energy storage system according to this embodiment, the control device (server 200 and battery ECU 232) starts the processing flow S21 to S27 each time it receives an EM request signal (S12) from the server 300. As a result, the processing flow S21 to S27 is repeatedly executed. Therefore, energy management is continuously performed by the processing in S25. While energy management is being performed, the control device repeatedly performs the selection of an energy storage device (S22). Therefore, the control device can change the EM controlled target (energy storage device used for energy management) in response to a request from the server 300. While energy management is being performed, the control device sequentially cuts off the current of each of the multiple energy storage devices (S23) and acquires the output value of the current sensor 233a of the learning target (energy storage device whose current has been cut off) (S26). This makes it possible to sequentially correct the output of each current sensor in the battery packs 23-1 to 23-N (correction of detection error).

[0041] The processing flow shown in Figure 2 can be modified as needed. For example, the order of processing may be changed or unnecessary steps may be omitted depending on the purpose. Also, the content of any of the processes may be changed. Figure 4 shows a modified example of the energy management method shown in Figure 2. Servers 200 and 300 may each execute the processing shown in Figure 4 instead of the processing shown in Figure 2. In the modified example shown in Figure 4, server 200 periodically executes the processing flow of S31, S32, S21A and S23-S27 (hereinafter referred to as the "S31 flow").

[0042] In S31, the server 200 determines the EM control targets and learning targets. From battery packs 23-1 to 23-N, a predetermined number of battery packs are selected as learning targets, and the battery packs not selected as learning targets are selected as EM control targets. In other words, in this modified example as well, the battery packs 23 that were not selected as EM control targets correspond to the learning targets. The predetermined number (the number of battery packs 23 included in the learning targets) may be one or multiple.

[0043] In this modified example, the S31 flow is executed periodically. Therefore, the selection of the EM control target and the learning target (S31) is performed repeatedly. The server 200 may change the learning target each time selection (S31) is made so that learning is performed for all current sensors 233a of battery packs 23-1 to 23-N during the execution of energy management. The server 200 may select the battery packs 23 to be learned in the order of battery packs 23-1, 23-2, 23-3, ..., 23-N.

[0044] In the following S32, the server 200 determines the maximum charging power and maximum discharging power of the energy storage system 100 based on the input / output capabilities of the EM-controlled system. The server 200 may also further determine the maximum charging energy and maximum discharging energy of the energy storage system 100 based on the State of Charge (SOC) of the energy storage system 100. Each of the obtained maximum charging power, maximum discharging power, maximum charging energy, and maximum discharging energy corresponds to the input / output capabilities of the energy storage system 100. The server 200 then transmits a signal indicating the input / output capabilities of the energy storage system 100 (hereinafter referred to as the "system signal") to the server 300. Subsequently, in S21A, the server 200 determines whether or not it has received an EM request signal from the server 300 (see S12A described later), and does not proceed with processing until an EM request signal is received.

[0045] Server 300 initiates the S11, S12A processing flow each time it receives a system signal from Server 200. In S11, Server 300 performs the same processing as in S11 in Figure 2. In the subsequent S12A, Server 300 requests Server 200 to perform Energy Management (EM) to improve the state of the power grid PG, based on the detection result of S11 and the input / output properties indicated by the system signal received from Server 200, which Server 200 is capable of performing. Specifically, Server 300 sends an EM request signal to Server 200 indicating the content of the requested EM. Once the processing in S12A is executed, the S11, S12A processing flow ends.

[0046] When server 200 receives an EM request signal from server 300 (YES in S21A), processing proceeds to S23. The processing from S23 onward is the same as S23-S27 in Figure 2, so the explanation will not be repeated. However, in this modified example, once the processing in S27 is executed, the process returns to the first step (S31).

[0047] The stationary energy storage system according to the above modified example also enables highly accurate energy management using the energy storage device (battery pack 23). Furthermore, the control device (server 200 and battery ECU 232) according to the above modified example repeatedly selects an energy storage device (S31) while energy management is being performed. Therefore, the control device can change the EM control target and the learning target in response to a request from the server 300. While energy management is being performed, the control device sequentially cuts off the current to each of the multiple energy storage devices (S23) and acquires the output value of the current sensor 233a of the learning target (energy storage device whose current has been cut off) (S26). This makes it possible to sequentially correct the output of each current sensor in battery packs 23-1 to 23-N (correction of detection error).

[0048] The configuration of the energy storage device (battery pack) is not limited to the configuration shown in Figure 1. For example, the battery ECU 232 may be omitted. The server 200 may directly control the SMR 21 and the DC / DC conversion circuit 22 without going through the battery ECU 232. The power grid PG is not limited to a large AC grid, but may be a microgrid or a DC grid. In the case where the power grid PG is a DC grid, the DC / AC conversion circuit 10 may be omitted. Instead of EM (Energy Management) for the power grid, other EMs (e.g., EM for off-grid buildings, or EM for adjustment power auctioned on the electricity market) may be implemented.

[0049] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention 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]

[0050] 10 DC / AC conversion circuits, 21, 21-1~21-N SMR, 22, 22-1~22-N DC / DC conversion circuits, 23, 23-1~23-N battery packs, 100 energy storage systems, 200 servers, 210 processors, 220 memory devices, 231 batteries, 232 battery ECUs, 233a current sensors, 300 servers, PG power systems.

Claims

1. Multiple energy storage devices connected in parallel to each other, Each of the aforementioned multiple energy storage devices is provided with a relay and a current sensor, A stationary energy storage system comprising a control device that controls the current value of each of the plurality of energy storage devices, The control device is configured to select a predetermined number of energy storage devices from among the plurality of energy storage devices as learning targets, and to select one or more of the energy storage devices other than the learning targets as control targets to be used for energy management. The control device is The current is interrupted by the relay corresponding to the learning target, and the output value of the current sensor corresponding to the learning target is obtained. A stationary energy storage system configured to correct the detection error of the current sensor corresponding to the learning target based on the acquired output value.

2. The stationary energy storage system according to claim 1, wherein the control device is configured to preferentially select as the control target an energy storage device in which the elapsed time since the most recent correction of the detection error of the corresponding current sensor has been short.

3. The stationary energy storage system is A power conversion circuit provided in each of the plurality of energy storage devices, which transforms the output voltage of the energy storage device in accordance with a command from the control device. Furthermore, The stationary energy storage system according to claim 1, wherein the plurality of energy storage devices include a first energy storage device including a first battery and a second energy storage device including a second battery of a different type from the first battery.

4. The control device is configured to repeatedly perform the selection of the learning target and the control target, The stationary energy storage system according to any one of claims 1 to 3, wherein the control device is configured to change the learning target each time it is selected so that the detection error correction is performed sequentially for the current sensors of the plurality of energy storage devices.

5. The stationary energy storage system is configured to perform energy management of the power grid in response to requests from a server that manages the power grid. The stationary energy storage system according to any one of claims 1 to 3, wherein the control device is configured to constantly accept the request from the server.

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