Power storage system and control method of charging and discharging

Abstract

Provided are: a plurality of power converters; a plurality of power storage elements that are charged and discharged via the plurality of power converters; a connection circuit that connects, via a first path, power storage elements selected as maintenance targets among the plurality of power storage elements to one power converter and connects other power storage elements to other power converters via a second path different from the first path; and a control device that performs maintenance via the first path while sequentially switching the power storage elements selected as the maintenance targets and performs charging and discharging of the other power storage elements via the second path.

Description

Technical Field

[0001] This invention relates to an energy storage system and a method for controlling charging and discharging. Background Technology

[0002] The use of energy storage elements is expanding in large-scale energy storage systems that store electricity generated from renewable energy sources or existing power generation systems.

[0003] In the application of energy storage components, maintenance measures, including regular inspections such as degradation diagnosis, must be taken. Patent Document 1 discloses a system that enables maintenance personnel to easily obtain the status data of the energy storage device by going to the location where the equipment containing the energy storage component is installed and using a terminal device carried by the maintenance personnel.

[0004] During regular inspections by maintenance personnel, a status check is conducted, including visual verification. A report is prepared based on the status data of the energy storage components obtained from the terminal device and the status check at the installation location.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6402925 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, large-scale ESS (Energy Storage System) systems contain a huge number of energy storage components, so it is impractical to shut down the system for maintenance and inspection and have maintenance personnel perform maintenance and inspection on the large number of energy storage components.

[0010] The purpose of this invention is to provide an energy storage system and a charging and discharging control method that can automatically perform maintenance without stopping the system.

[0011] Methods for solving problems

[0012] One aspect of the present invention relates to an energy storage system comprising: a plurality of power converters; a plurality of energy storage elements, which are charged and discharged via the plurality of power converters; a connection circuit that connects an energy storage element selected as the object of maintenance from the plurality of energy storage elements to a power converter via a first path, and connects other energy storage elements to other power converters via a second path different from the first path; and a control device that sequentially switches the energy storage element selected as the object of maintenance while performing maintenance via the first path, and performing charging and discharging of other energy storage elements via the second path.

[0013] In a charging and discharging control method according to one aspect of the present invention, a storage element to be maintained is sequentially selected from a plurality of storage elements that are charged and discharged via a plurality of power converters. The selected storage element is connected to one of the plurality of power converters via a first path, and other storage elements are connected to other power converters via a second path different from the first path. Maintenance of the selected storage element is performed via the first path, and charging and discharging of the other storage elements are performed via the second path.

[0014] Invention Effects

[0015] The above method enables automatic maintenance without stopping the system. Attached Figure Description

[0016] Figure 1 This is a schematic illustration illustrating an example of the installation of an energy storage system according to the implementation method.

[0017] Figure 2 This is a circuit diagram illustrating an example of the structure of an energy storage system.

[0018] Figure 3 This is a schematic diagram showing the connection status when charging and discharging without maintenance.

[0019] Figure 4 This is a schematic diagram showing the connection status during maintenance and charging / discharging.

[0020] Figure 5 This is a schematic diagram showing the connection status during maintenance and charging / discharging.

[0021] Figure 6 This is a schematic diagram showing the connection status during maintenance and charging / discharging.

[0022] Figure 7 This is a flowchart illustrating the control process in Implementation 1.

[0023] Figure 8This is a flowchart illustrating the control process in Implementation Method 2.

[0024] Figure 9 This is a flowchart illustrating the control process in Implementation Method 3.

[0025] Figure 10 This is a schematic diagram showing an example of the installation of the energy storage system in Embodiment 4.

[0026] Figure 11 This is a schematic diagram showing an example of the installation of the energy storage system in Embodiment 5. Detailed Implementation

[0027] (1) The energy storage system disclosed herein comprises: a plurality of power converters; a plurality of energy storage elements, which are charged and discharged via the plurality of power converters; a connection circuit that connects an energy storage element selected as the object of maintenance from the plurality of energy storage elements to a power converter via a first path, and connects other energy storage elements to other power converters via a second path different from the first path; and a control device that sequentially switches the energy storage element selected as the object of maintenance while performing maintenance via the first path and performing charging and discharging of other energy storage elements via the second path.

[0028] The energy storage system described in (1) above is installed alongside power generation equipment such as solar power generation equipment and wind power generation equipment to store electricity provided by the power generation equipment and provide the stored electricity to the load. The energy storage system has multiple power converters and energy storage elements. The power converter is, for example, a power conditioner (PCS: Power Conditioning System) that converts the DC power provided by the power generation equipment into a specified amount of DC power, and charges the energy storage elements with the converted DC power. The power converter converts the DC power discharged from the energy storage elements into AC power and provides the converted AC power to the load. Energy storage elements include rechargeable and dischargeable battery cells such as lead-acid batteries, lithium-ion batteries, and capacitors. Energy storage elements can also be modules formed by connecting multiple energy storage elements in series, battery banks formed by connecting modules in series, or battery domains formed by connecting multiple battery banks in parallel.

[0029] The energy storage system performs maintenance on multiple energy storage elements while sequentially switching the energy storage elements to be maintained. The energy storage element selected for maintenance is connected to a power converter via a first path, and the other energy storage elements are connected to other power converters via a second path. In the energy storage system described above (1), since the maintenance path (first path) and the charging / discharging path (second path) can be different, maintenance on each energy storage element can be performed without interrupting the original function (charging / discharging function) of the energy storage system.

[0030] The energy storage device selected for maintenance can be one or more. In the latter case, maintenance is performed on multiple selected energy storage devices simultaneously, and the remaining energy storage devices are used for charging and discharging.

[0031] In the energy storage system described in (1) above, maintenance can be automated, eliminating the need for maintenance personnel to travel to the location of the energy storage system. Data indicating the status of the energy storage devices during maintenance can be obtained remotely without visiting the location and analyzed. Visual inspection of the energy storage components by maintenance personnel is unnecessary, reducing human error.

[0032] (2) In the energy storage system described in (1) above, the plurality of energy storage elements may include reused energy storage elements.

[0033] It is known that energy storage components gradually deteriorate due to repeated charging and discharging. Depending on the cause of deterioration, there are cases where, although they are not suitable for high-current applications, they are fine for low-current applications and can be reused for a different purpose. For example, for energy storage components whose deterioration is due to increased resistance and no decrease in charge carriers, it is believed that the amount of electricity that can be stored has not decreased since manufacturing. Such energy storage components can be reused for storing electricity generated by power generation equipment such as solar power generation equipment and wind power generation equipment. In the energy storage system described above (2), by incorporating reused energy storage components during system manufacturing or maintenance, the reused energy storage components can be effectively utilized.

[0034] (3) In the energy storage system described in (2) above, the control device may control the connection circuit to connect the reused energy storage element to the power converter via the first path and perform maintenance via the first path in order to maintain the reused energy storage element before the first charge and discharge of the reused energy storage element in the energy storage system.

[0035] In the energy storage system described in (3) above, when a reused energy storage element is installed in the energy storage system, it is maintained separately from other energy storage elements. If there are no problems, it is connected to other energy storage elements for charging and discharging, thus avoiding the risk of failure. Since new energy storage elements are inspected before leaving the factory, prior inspection before installation into the energy storage system is generally not required. On the other hand, when a reused energy storage element is installed in the energy storage system, prior inspection to verify the performance of the energy storage element is usually performed. In contrast, in the energy storage system described in (3) above, since the energy storage system itself functions as an inspection device, prior inspection is no longer required even if the energy storage element installed in the system is a reused product.

[0036] (4) In the energy storage system described in (2) above, the control device may control the connection circuit to connect the reused energy storage element to the power converter via the first path and charge the reused energy storage element via the first path in order to charge the reused energy storage element before connecting it to other energy storage elements.

[0037] In the energy storage system described in (4) above, when a reused energy storage element is installed in the energy storage system, it can be charged separately from other energy storage elements. Therefore, the voltage can be made consistent before connecting it to other energy storage elements, preventing large currents from flowing into the reused energy storage element. In the energy storage system described in (4) above, when the voltage of the reused energy storage element is high, it can be discharged separately from other energy storage elements. Although the voltage of the new energy storage element is usually known in advance, the voltage of the reused energy storage element is usually unknown. When the voltage of the reused energy storage element is high, it can be discharged separately from other energy storage elements in order to make its voltage consistent with the voltage of other energy storage elements already installed in the energy storage system.

[0038] (5) In any of the energy storage systems described in (1) to (4) above, the maintenance may also include a capacity test on the selected energy storage element.

[0039] In the energy storage system described in (5) above, a capacity test is performed as a maintenance procedure for the energy storage system. The capacity test is a test as follows: the energy storage element is discharged until its remaining capacity is defined as zero voltage, and then charged with a constant current from that state until it is defined as a fully charged voltage, thereby measuring the capacity. Since capacity measurement takes time, it is preferable to perform the capacity test automatically using the method disclosed herein. As a maintenance procedure for the energy storage system, it is possible to check whether a short circuit has occurred in the module containing the energy storage element, battery pack, etc., or whether an internal short circuit has occurred within the energy storage element itself. Alternatively, as a maintenance procedure for the energy storage system, it is also possible to check whether the communication between the energy storage system and the outside world is normal.

[0040] (6) In the charging and discharging control method of this disclosure, the energy storage element to be maintained is sequentially selected from a plurality of energy storage elements that are charged and discharged via a plurality of power converters, the selected energy storage element is connected to one of the plurality of power converters via a first path, and other energy storage elements are connected to other power converters via a second path different from the first path, maintenance of the selected energy storage element is performed via the first path, and charging and discharging of other energy storage elements is performed via the second path.

[0041] In the charging and discharging control method described in (6) above, maintenance is performed automatically by switching between the maintenance path (first path) and the charging and discharging path (second path), so maintenance personnel no longer need to go to the location where the energy storage system is installed. Since data indicating the status of the energy storage device during maintenance can be obtained and analyzed remotely, there is no need for maintenance personnel to visually confirm the energy storage components, thus reducing human error.

[0042] Hereinafter, the present invention will be specifically described based on the accompanying drawings illustrating its embodiments.

[0043] (Implementation Method 1)

[0044] Figure 1 This is a schematic diagram illustrating an example of the configuration of the energy storage system 1 according to the embodiment. The energy storage system 1 according to the embodiment includes multiple power converters 11 and multiple energy storage elements 12 that are charged and discharged via the multiple power converters 11 (see reference). Figure 2 The power converter 11 and the energy storage element 12 of the energy storage system 1 are integrated into the interior of a container, for example. Alternatively, the energy storage system 1 may be configured to have multiple containers that individually house each power converter 11 and multiple containers that individually house each energy storage element 12.

[0045] The energy storage system 1 is installed alongside power generation equipment such as solar power (PV) and wind power (WT). The energy storage system 1 converts the power supplied by the power generation equipment into a specified amount of direct current (DC) power via a power converter 11. This converted DC power then charges the energy storage element 12, thereby storing electricity. The energy storage system 1 also converts the DC power discharged from the energy storage element 12 into alternating current (AC) power via the power converter 11, supplying the AC power to the load PC. The power source and destination for the energy storage system 1 can also be the power system PS.

[0046] The energy storage system 1 is communicatively connected to the management server 2 and the user server 3 via the communication network NW. The management server 2 is used by the administrators of the energy storage system 1. The user server 3 is used by users, aggregators, etc. The communication network NW is a general communication network such as the Internet. Alternatively, the communication network NW can also be a dedicated line.

[0047] Management server 2 communicates with user server 3 via communication network NW to obtain information related to power demand. This information includes, for example, the amount of electricity to be supplied to the load PC (the amount of power requested in each time period). Management server 2 also communicates with energy storage system 1 via communication network NW to obtain information related to the operational status of energy storage system 1. This information includes, for example, the current status of energy storage element 12, the time progression of SOC (State of Charge) and SOH (State of Health), the history of charging and discharging operations, and the history of maintenance operations. Management server 2 can also notify user server 3 of the information obtained from energy storage system 1. Based on the information obtained from energy storage system 1 and user server 3, management server 2 can also predict future power supply (load) or provide charging / discharging switching instructions and maintenance start instructions to energy storage system 1.

[0048] Figure 2 This is a circuit diagram illustrating a structural example of an energy storage system 1. The energy storage system 1 includes multiple power converters 11 and multiple energy storage elements 12 that are charged and discharged via the power converters 11. Each power converter 11 has the following functions: converting power supplied from a power generation device into a specified amount of direct current (DC) power and outputting it to the energy storage elements 12; and converting DC power discharged from the energy storage elements 12 into alternating current (AC) power and outputting it to an external source (e.g., a load PC). The power converter 11 is also referred to as a PCS (Power Conditioning System).

[0049] The energy storage element 12 is a battery bank composed of multiple battery cells connected in series. The battery cells are, for example, lithium-ion rechargeable batteries. Alternatively, the battery cells can be based on solid-state batteries, lead-acid batteries, redox flow batteries, zinc-air batteries, alkaline manganese batteries, lithium-sulfur batteries, sodium-sulfur batteries, silver-zinc oxide batteries, nickel-metal hydride batteries, molten salt thermal batteries, etc., or they can be capacitors. Alternatively, the energy storage element 12 can be a single battery cell or a module composed of multiple battery cells connected in series. The energy storage element 12 can also be a battery domain composed of multiple battery banks connected in parallel.

[0050] In the embodiment, the structure of the energy storage system 1, which includes three power converters 11 and three energy storage elements 12, will be described. Hereinafter, each power converter 11 will be referred to as power converter 11A to 11C, and each energy storage element 12 will be referred to as energy storage element 12A to 12C.

[0051] In addition to the power converter 11 and the energy storage element 12, the energy storage system 1 also includes a control unit 10, a connection circuit L, and BMU (Battery Management Unit) 13A~13C.

[0052] The control unit 10 is a control device used to control the operation of the energy storage system 1. The control unit 10 includes, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The CPU of the control unit 10 reads and executes a computer program stored in the ROM to control charging and discharging operations, maintenance operations, etc., in the energy storage system 1. Data generated during the execution of the computer program and data obtained from external sources are temporarily stored in the RAM.

[0053] The control unit 10 may also have a communication interface. The communication interface of the control unit 10 includes an internal communication interface for communicating with the power converter 11 and BMUs 13A-13C, or for outputting control signals to open and close various switches SW1, SW2, SW1A-SW1C, and SW2A-SW2C. The communication interface of the control unit 10 may also have an external communication interface for communicating with the management server 2 and the user server 3 via the communication network NW.

[0054] The control unit 10 may also include a clock that outputs date and time information, a timer that measures elapsed time, and a counter that counts quantities.

[0055] The connection circuit L is a circuit that connects the power converter 11 and the energy storage element 12. The connection circuit L includes a maintenance path L1 (first path) and a charging / discharging path L2 (second path). Path L1 is equipped with a switch SW1, and switches SW1A to SW1C, which are controlled by the control unit 10. Path L2 is equipped with a switch SW2, and switches SW2A to SW2C, which are also controlled by the control unit 10. In one example, these switches SW1, SW2, SW1A to SW1C, and SW2A to SW2C are relay switches. Alternatively, they may be semiconductor switches.

[0056] BMU13A~13C are management devices provided for each energy storage element 12A~12C. BMU13A~13C monitors the status of each energy storage element 12A~12C and notifies the control unit 10 of the data obtained from the energy storage elements 12A~12C.

[0057] The energy storage system 1 involved in the implementation method controls the opening and closing of each switch SW1, SW2, SW1A~SW1C, SW2A~SW2C through the control unit 10, thereby switching between the path when charging and discharging without maintenance and the path when charging and discharging while maintaining maintenance.

[0058] Figure 3 This is a schematic diagram showing the connection status during charging and discharging without maintenance. Figure 3 For simplicity, only the connection relationship between the power converter 11 and the energy storage element 12 is shown. When charging and discharging without maintenance of the energy storage element 12, the control unit 10 opens switches SW1, SW1A~SW1C of path L1 and closes switches SW2, SW2A~SW2C of path L2. In this connection state, when charging the energy storage element 12, the power supplied from the generator is converted into a specified amount of DC power by the power converter 11 and output to the energy storage element 12 via path L2. The energy storage element 12 is charged by the DC power supplied via path L2.

[0059] Figure 3 An example of charging the energy storage element 12 is shown, but the same applies to discharging from the energy storage element 12. In the case of discharging from the energy storage element 12, the DC power output from the energy storage element 12 is input to the power converter 11 via path L2, and after being converted into AC power by the power converter 11, it is supplied to the load PC that is being delivered to its destination.

[0060] Figures 4-6 This is a schematic diagram illustrating the connection status during maintenance and charging / discharging. Figure 4 ~in Figure 6 For simplicity, only the connection relationship between the power converter 11 and the energy storage element 12 is shown in the diagram. Figure 4 The diagram illustrates a connection state where energy storage element 12A is maintained while energy storage elements 12B and 12C are charged and discharged simultaneously. In this state, control unit 10 closes switches SW1 and SW1A on path L1 and opens switches SW1B and SW1C. Furthermore, control unit 10 opens switches SW2 and SW2A on path L2 and closes switches SW2B and SW2C. In this connection state, only energy storage element 12A is connected to power converter 11A via path L1, while the remaining energy storage elements 12B and 12C are connected to power converter 11B and 11C via path L2, which is different from path L1. Control unit 10 can maintain energy storage element 12A using path L1 while charging and discharging energy storage elements 12B and 12C using path L2.

[0061] As a maintenance function, the control unit 10 performs a capacity test on the energy storage element 12A, for example. Specifically, the control unit 10 discharges the battery until the remaining capacity is defined as zero, and then charges the energy storage element 12A with a constant current until it reaches the voltage defined as a full charge, thereby measuring the capacity. If the current full charge capacity relative to the initial full charge capacity (SOH) of the energy storage element 12A is lower than a set value (e.g., 50%), the control unit 10 may also output an alert to the management server 2, prompting the replacement of the energy storage element 12A with a new energy storage element.

[0062] Figure 5The diagram illustrates a connection state where energy storage element 12B is maintained while energy storage elements 12A and 12C are charged and discharged. In this state, control unit 10 closes switches SW1 and SW1B on path L1 and opens switches SW1A and SW1C. Then, control unit 10 opens switches SW2 and SW2B on path L2 and closes switches SW2A and SW2C. In this connection state, only energy storage element 12B is connected to power converter 11A via path L1, while the remaining energy storage elements 12A and 12C are connected to power converter 11B and 11C via path L2, which is different from path L1. Control unit 10 can maintain energy storage element 12B using path L1 while simultaneously charging and discharging energy storage elements 12A and 12C using path L1. The maintenance of energy storage element 12B is the same as the maintenance of energy storage element 12A.

[0063] Figure 6 The diagram illustrates a connection state where energy storage element 12C is maintained while energy storage elements 12A and 12B are charged and discharged simultaneously. In this state, control unit 10 closes switches SW1 and SW1C on path L1 and opens switches SW1A and SW1B. Then, control unit 10 opens switches SW2 and SW2C on path L2 and closes switches SW2A and SW2B. In this connection state, only energy storage element 12C is connected to power converter 11A via path L1, while the remaining energy storage elements 12A and 12B are connected to power converter 11B and 11C via path L2, which is different from path L1. Control unit 10 can maintain energy storage element 12C using path L1 while simultaneously charging and discharging energy storage elements 12A and 12B using path L1. The maintenance of energy storage element 12C is the same as the maintenance of energy storage element 12A.

[0064] Figure 7 This is a flowchart illustrating the control process in Embodiment 1. The control unit 10 of the energy storage system 1 determines whether to begin maintenance of the energy storage element 12 (step (STEP) S101). For example, the control unit 10 pre-sets a period of time when the power requested from the load PC is relatively low (e.g., nighttime) as the maintenance period. The control unit 10 refers to a built-in clock to determine whether the current time is within the maintenance period and whether to begin maintenance. Alternatively, maintenance can be determined to begin at a periodic time or upon receiving an instruction from the management server 2.

[0065] If the control unit 10 determines that maintenance should not be started (S101: No), it remains on standby until the maintenance start time is set. In this case, the connection state of the power converter 11 and the energy storage element 12 is controlled to become Figure 3 The connection state shown enables charging and discharging via each power converter 11A~11C.

[0066] If it is determined that maintenance should begin (S101: YES), the control unit 10 selects one of the multiple energy storage elements 12 in the energy storage system 1 that has not been maintained as the maintenance target (step S102).

[0067] The control unit 10 controls the opening and closing of switches SW1, SW1A~SW1C on the control path L1 to connect only the selected energy storage element 12 to one power converter 11A, and controls the opening and closing of switches SW2, SW2A~SW2C on the control path L2 to connect the remaining energy storage elements 12 to other power converters 11B and 11C (step S103).

[0068] The control unit 10 performs maintenance on the energy storage element 12 selected in step S102 via a power converter 11A (step S104), and performs charging and discharging of the remaining energy storage elements 12 via other power converters 11B and 11C (step S105).

[0069] After completing step S104, the control unit 10 determines whether to end the maintenance (step S106). The control unit 10 determines whether to end the maintenance by checking whether there are any energy storage elements 12 in the energy storage system 1 that have not been maintained.

[0070] If there are any unmaintained energy storage components 12, the control unit 10 determines that maintenance should not be terminated (S106: No), and returns the process to step S102. The control unit 10 selects an unmaintained energy storage component 12 and executes the processes of steps S103 to S106 again.

[0071] If there are no unmaintained energy storage components 12, the control unit 10 determines that maintenance is to be completed (S106: YES) and ends the processing of this flowchart.

[0072] As described above, in Embodiment 1, when performing maintenance on the energy storage element 12, it is not necessary to stop the energy storage system 1. Maintenance can be performed on a portion of the energy storage element 12 while the remaining energy storage element 12 is used for charging and discharging.

[0073] Since new energy storage components undergo pre-shipment inspection, prior inspection before installation into the system is generally unnecessary. On the other hand, when reusable energy storage components are installed into the system, prior inspection is typically performed to verify their performance. In contrast, in the energy storage system 1 according to Embodiment 1, the energy storage system 1 itself functions as an inspection device, so even if the energy storage components installed in the system are reusable, prior inspection is no longer required.

[0074] In this embodiment, the number of power converters 11 and energy storage elements 12 installed in the energy storage system 1 is set to 3 each. Alternatively, the number of power converters 11 installed may be 2 or 4 or more, and the number of energy storage elements 12 installed may also be 2 or 4 or more. The number of power converters 11 and energy storage elements 12 installed may also not be the same.

[0075] In this embodiment, the structure is configured to maintain the energy storage element 12 one by one. Alternatively, the structure can be configured such that multiple energy storage elements 12 are maintained at a time, and the remaining energy storage elements 12 are charged and discharged.

[0076] In this embodiment, maintenance of the energy storage element 12 is performed by conducting a capacity test. Alternatively, a check can be performed to see if a short circuit has occurred in the energy storage element 12 itself or in the battery pack or module containing the energy storage element 12, or to check if the communication between the energy storage system 1 and the outside is normal.

[0077] (Implementation Method 2)

[0078] In Embodiment 2, a structure for maintaining the reused energy storage element before charging and discharging it is described when the reused energy storage element is installed in the energy storage system 1.

[0079] Figure 8 This is a flowchart illustrating the control process in Embodiment 2. In the energy storage system 1, sometimes reused energy storage elements are installed during manufacturing or at a point after the start of use. When reused energy storage elements are installed in the energy storage system 1, the control unit 10 performs the following processing. Hereinafter, the reused energy storage element installed in the energy storage system 1 is designated as energy storage element 12A, and existing energy storage elements that are not reused are designated as energy storage elements 12B and 12C. Information indicating that energy storage element 12A is a reused energy storage element is provided to the control unit 10 beforehand.

[0080] The control unit 10 selects the reusable energy storage element 12A as the energy storage element to be maintained (step S201).

[0081] Control unit 10 closes switches SW1 and SW1A on path L1 and opens switches SW1B and SW1C to connect only the selected energy storage element 12A to one power converter 11A. Control unit 10 opens switches SW2 and SW2A on path L2 and closes switches SW2B and SW2C to connect the remaining energy storage elements 12B and 12C to other power converters 11B and 11C (step S202).

[0082] The control unit 10 performs maintenance on the reused energy storage element 12A via a power converter 11A (step S203), and performs charging and discharging of the remaining energy storage elements 12B and 12C via other power converters 11B and 11C (step S204).

[0083] Based on the maintenance execution results, the control unit 10 determines whether there is a problem in the reused energy storage element 12A (step S205).

[0084] Control unit 10 performs a capacity test, for example, as maintenance of the reused energy storage element 12A. If, as a result of the capacity test, there is sufficient full-charge capacity, control unit 10 determines that the installed reused energy storage element 12A is without problems (S205: NO), and terminates the process in this flowchart. In this case, the reused energy storage element 12A installed in energy storage system 1 is directly utilized as one of the energy storage elements 12 constituting energy storage system 1.

[0085] As a result of the capacity test, if there is not sufficient full charge capacity, the control unit 10 will determine that there is a problem with the installed reusable energy storage element 12A (S205: YES), and output an alarm to the management server 2, urging the energy storage element 12A to be replaced with a new energy storage element (step S206).

[0086] As described above, in Embodiment 2, when a reusable energy storage element is installed in the energy storage system 1, maintenance is performed before connecting it to other energy storage elements 12, thus suppressing the risk of malfunction.

[0087] (Implementation Method 3)

[0088] In Embodiment 3, a structure is described in which a reusable energy storage element is charged before being connected to other energy storage elements 12 that have already been installed when it is installed into the energy storage system 1.

[0089] Figure 9This is a flowchart illustrating the control process in Embodiment 3. In the energy storage system 1, sometimes reused energy storage elements are installed during manufacturing or after the start of use. When reused energy storage elements are installed in the energy storage system 1, the control unit 10 performs the following processing. Hereinafter, the reused energy storage element installed in the energy storage system 1 is designated as energy storage element 12A, and existing energy storage elements that are not reused are designated as energy storage elements 12B and 12C. Information indicating that energy storage element 12A is a reused energy storage element is provided to the control unit 10 beforehand.

[0090] The control unit 10 selects the reusable energy storage element 12A as the energy storage element to be maintained (step S301).

[0091] Control unit 10 closes switches SW1 and SW1A on path L1 and opens switches SW1B and SW1C to connect only the selected energy storage element 12A to one power converter 11A. Control unit 10 opens switches SW2 and SW2A on path L2 and closes switches SW2B and SW2C to connect the remaining energy storage elements 12B and 12C to other power converters 11B and 11C (step S302).

[0092] The control unit 10 charges the reused energy storage element 12A via a power converter 11A (step S303). The post-charging process is the same as in embodiment 1. When the maintenance start time is reached, maintenance is performed sequentially, including the reused energy storage element 12A, while charging and discharging are performed.

[0093] As described above, in embodiment 3, when a reusable energy storage element is installed in the energy storage system 1, charging is performed before connecting it to other energy storage elements 12, thus preventing a large current from flowing into the reusable energy storage element.

[0094] Alternatively, if a reused energy storage element is installed in the energy storage system 1, the reused energy storage element can be discharged before being connected to other energy storage elements 12. The voltage of a new energy storage element is usually known beforehand, but the voltage of a reused energy storage element is usually unknown. If the voltage of the reused energy storage element is high, it can be discharged separately from the other energy storage elements 12 in order to match their voltages.

[0095] (Implementation Method 4)

[0096] Figure 10This is a schematic diagram showing an example of the installation of the energy storage system 1 in Embodiment 4. The energy storage system 1 in Embodiment 4 is connected, for example, between the power system PS and the load PC. The internal structure and operation of the energy storage system 1 are the same as in Embodiments 1-3, therefore its description is omitted.

[0097] In embodiment 4, the energy storage system 1 functions, for example, as a UPS (Uninterruptible Power Supply). The energy storage system 1 stores electricity supplied from the power system PS under normal conditions and provides the stored electricity to the load PC during power outages, etc.

[0098] (Implementation Method 5)

[0099] Figure 11 This is a schematic diagram showing an example of the installation of the energy storage system 1 in Embodiment 5. The energy storage system 1 in Embodiment 5 is connected to the power system PS, for example. The internal structure and operation of the energy storage system 1 are the same as in Embodiments 1-3, therefore its description is omitted.

[0100] The energy storage system 1 in embodiment 5 is a system for adjusting the supply and demand of electricity. The energy storage system 1 stores the surplus electricity in the power system PS, and when the electricity that should be supplied from the power system PS is insufficient, it supplies the stored electricity to the power system PS to make up for the power shortage in the power system PS.

[0101] The disclosed embodiments are illustrative in all respects and not restrictive. The scope of the invention is defined by the claims, including all modifications within the meaning and scope equivalent to the claims.

[0102] Explanation of reference numerals in the attached figures

[0103] 1. Energy storage system; 10. Control unit; 11. Power converter; 12. Energy storage element; 13. BMU; L1, L2 paths; SW1, SW2, SW1A~SW1C, SW2A~SW2C switches.

Claims

1. An energy storage system, comprising: Multiple power converters; Multiple energy storage elements are charged and discharged via the multiple power converters; The connection circuit connects the energy storage element selected as the object of maintenance from the plurality of energy storage elements to a power converter via a first path, and connects the other energy storage elements to other power converters via a second path different from the first path. as well as The control device sequentially switches between selected energy storage elements as maintenance targets, performs maintenance via the first path, and performs charging and discharging of other energy storage elements via the second path.

2. The energy storage system as described in claim 1, wherein, The plurality of energy storage elements includes reusable energy storage elements.

3. The energy storage system as described in claim 2, wherein, In order to maintain the reused energy storage element before its initial charging and discharging within the energy storage system, the control device controls the connection circuit to connect the reused energy storage element to the power converter via the first path and performs maintenance via the first path.

4. The energy storage system as described in claim 2, wherein, In order to charge the reused energy storage element before connecting it to other energy storage elements, the control device controls the connection circuit to connect the reused energy storage element to the power converter via the first path and to charge the reused energy storage element via the first path.

5. The energy storage system according to any one of claims 1 to 4, wherein, The maintenance includes a capacity test on the selected energy storage components.

6. The energy storage system according to any one of claims 1 to 5, wherein, The energy storage system is connected to the power system.

7. The energy storage system as described in claim 6, wherein, The energy storage system stores the remaining power in the power system.

8. The energy storage system as claimed in claim 6 or claim 7, wherein, The energy storage system provides the power system with the power stored in the energy storage element.

9. The energy storage system according to any one of claims 6 to 8, wherein, When the power system fails, the energy storage system provides the power stored in the energy storage element to the load.

10. A method for controlling charging and discharging, wherein, The energy storage element to be maintained is selected sequentially from multiple energy storage elements that have been charged and discharged through multiple power converters. The selected energy storage element is connected to one of the plurality of power converters via a first path, and the other energy storage elements are connected to the other power converters via a second path different from the first path. Maintenance of the selected energy storage components is performed via the first path. The charging and discharging of other energy storage components are performed via the second path.

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