Energy storage system and full charge capacity measuring method of storage battery board

Abstract

To measure full charge capacity of a storage battery board.SOLUTION: An energy storage system 10 linked to a system includes one or a plurality of storage battery boards 20, a power control unit 40 for adjusting supply and demand performing supply and demand adjustment of power by charging / discharging the storage battery boards 20, and a control device 50. The control device 50 charges the storage battery boards 20 from a complete discharge state to a full charge state by the power control unit 40 for adjusting supply and demand, or discharges from the full charge state to the complete discharge state, and measures a full charge capacity of the storage battery boards 20 based on a first current integration value while the storage battery boards 20 change from the complete discharge state to the full charge state, or a second current integration value while they change from the full charge state to the complete discharge state.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a technique for measuring the full charge capacity of a battery panel in an energy storage system connected to a power grid. [Background technology]

[0002] The introduction of energy storage systems is being promoted to achieve efficient energy management. When demand for electricity is lower than supply, the energy storage system charges a storage battery panel with surplus electricity, and when demand for electricity exceeds supply, the system discharges the battery panel to make up for the power shortage. Patent Document 1 discloses technology related to energy storage systems.

[0003] Patent Document 1 discloses the installation of an operation PCS and a capacity measurement PCS in a battery storage system. The operation PCS is used to adjust the supply and demand of electricity, and the capacity measurement PCS is used to measure the capacity of the battery on the battery panel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-158397 Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of Patent Document 1, if there is no capacity measurement PCS or if it breaks down, the full charge capacity (battery capacity) of the battery panel cannot be measured. An object of the present invention is to measure the full charge capacity of a battery panel using a method different from that of Patent Document 1, which is provided with a capacity measurement PCS. [Means for solving the problem]

[0006] The energy storage system is connected to a grid and includes one or more battery panels, a power control unit for adjusting supply and demand of electricity by charging and discharging the battery panels, and a control device.

[0007] The control device charges the battery panel from a fully discharged state to a fully charged state, or discharges the battery panel from a fully charged state to a fully discharged state using the power control unit for supply and demand adjustment, and measures the full charge capacity of the battery panel based on a first current accumulation value during the change of the battery panel from a fully discharged state to a fully charged state, or a second current accumulation value during the change of the battery panel from a fully charged state to a fully discharged state.

[0008] This technology can be applied to measuring the full charge capacity of a battery panel. [Effects of the Invention]

[0009] This technology can measure the full charge capacity of a battery panel using a method different from that of Patent Document 1, which uses a capacity measurement PCS. [Brief explanation of the drawings]

[0010] [Figure 1] Perspective view of an energy storage system [Figure 2] Energy storage system block diagram [Figure 3] Power Control Unit Block Diagram [Figure 4] Flowchart of full charge measurement process [Figure 5] Diagram showing the discharge operation of the battery panel [Figure 6] Diagram showing the charging operation of the battery panel [Figure 7] Diagram showing the timing for measuring full charge capacity [Figure 8A] Diagram showing three battery panels being charged and discharged simultaneously [Figure 8B] Diagram showing the battery panels being charged and discharged one by one [Figure 9] Energy storage system block diagram [Figure 10]Energy storage system block diagram DETAILED DESCRIPTION OF THE INVENTION

[0011] (Outline of this embodiment) (1) An energy storage system according to one embodiment of the present invention includes one or more battery panels, a power control unit for adjusting the supply and demand of electricity by charging and discharging the battery panels, and a control device.

[0012] The control device charges the battery panel from a fully discharged state to a fully charged state, or discharges the battery panel from a fully charged state to a fully discharged state using the power control unit for supply and demand adjustment, and measures the full charge capacity of the battery panel based on a first current accumulation value during the change of the battery panel from a fully discharged state to a fully charged state, or a second current accumulation value during the change of the battery panel from a fully charged state to a fully discharged state.

[0013] According to an energy storage system according to one embodiment of the present invention, the full charge capacity [Ah] is measured by charging and discharging the battery panel, changing it from a fully discharged state to a fully charged state (the reverse is also possible). The state of the battery panel can be understood from the full charge capacity measurement results, which can be useful for maintenance of the battery panel. When measuring the full charge capacity, the battery panel is charged and discharged using a power control unit for adjusting supply and demand, so a power control unit dedicated to measuring the full charge capacity can be omitted. Furthermore, because branch lines and switches for measuring the full charge capacity can be omitted, the system can be simplified, resulting in cost benefits.

[0014] This technology can also be applied to systems with a power control unit dedicated to measuring full charge capacity. In this case, even if some kind of trouble occurs with the power control unit dedicated to measuring full charge capacity, it is possible to measure full charge capacity [Ah] by using the power control unit for supply and demand adjustment.

[0015] (2) In the energy storage system described in (1) above, the control device may prioritize power supply and demand adjustment over full charge capacity measurement. This configuration enables control such as charging and discharging the battery panel and checking the full charge capacity using a power control unit for supply and demand adjustment when a supply and demand adjustment instruction is not received from a higher-level device such as an EMS (when no instruction is received and charging or discharging is not being performed). This configuration prioritizes power supply and demand adjustment over full charge capacity measurement, thereby achieving a power source with high flexibility in supply and demand adjustment, as well as enabling flexible measurement of full charge capacity, enabling efficient operation. Furthermore, by accurately determining the full charge capacity, the risk of being unable to adjust supply and demand as expected can be reduced, and requests from the higher-level EMS can be accurately met.

[0016] (3) An energy storage system in which a plurality of the energy storage systems described in (1) or (2) above are connected in parallel may be provided, and the full charge capacity may be measured by changing the storage battery panel whose full charge capacity is to be measured between a fully discharged state and a fully charged state by exchanging energy between the plurality of parallel-connected energy storage systems. In this configuration, there is almost no change in the energy of the entire energy storage system before and after measuring the full charge capacity. Therefore, an energy-saving energy storage system can be realized. Since energy exchange is completed only within the parallel-connected energy storage systems, there is an advantage in that the full charge capacity can be measured without affecting any system other than the system exchanging energy.

[0017] (4) An energy storage system in which a plurality of the energy storage systems described in (1) or (2) above are connected in parallel may be configured such that, during power supply and demand adjustment, the battery panel of an energy storage system among the plurality of energy storage systems whose full charge capacity is to be measured is charged or discharged preferentially over the battery panel of an energy storage system whose full charge capacity is not measured, thereby changing from a fully discharged state to a fully charged state or from a fully charged state to a fully discharged state. This configuration allows the full charge capacity to be measured in parallel with power supply and demand adjustment, which is suitable, for example, for cases where power supply and demand is unstable and supply and demand adjustment is performed frequently, making it possible to measure the full charge capacity only during supply and demand adjustment. Measuring the full charge capacity does not restrict supply and demand adjustment, contributing to energy conservation. Another advantage is that there is no need to shut down the system to measure the full charge capacity (maintenance), thereby ensuring operating time for the energy storage system.

[0018] <Embodiment 1> 1. Description of the energy storage system S FIG. 1 is a perspective view of an energy storage system 10. The energy storage system 10 is a system that is connected to a power grid 1 and adjusts the supply and demand of electricity. The power grid 1 may be that of an electric power company, or it may be an independent power grid that is made up of the stand-alone operation output of a large power conditioner.

[0019] 2 is a block diagram of the energy storage system 10. In this embodiment, three energy storage systems 10A to 10C are installed in parallel. Since the energy storage systems 10A to 10C have the same structure, the configuration of the energy storage system 10A will be described as a representative.

[0020] The energy storage system 10A includes a battery panel 20A and a PCS panel 30A. PCS stands for Power Conditioning System.

[0021] The battery panel 20A includes a power storage bank 21, a monitoring unit 23, and a housing 25 that houses these. The power storage bank 21 is composed of a plurality of power storage cells connected in series. Various types of cells can be used as the power storage cells as long as they are capable of storing electricity (capable of repeated charging and discharging), such as non-aqueous electrolyte secondary battery cells such as lithium ion secondary batteries, capacitors, NAS battery cells, and redox flow battery cells. The power storage bank 21 may be configured as a single bank, or may be configured as multiple banks connected in parallel.

[0022] The monitoring unit 23 monitors the state of the battery panel 20A. Items monitored include the voltage (total voltage of the power storage banks 21), current (total current of the power storage banks 21), temperature, etc. of the battery panel 20A. These monitored items can be measured by sensors.

[0023] The storage battery panel 20A is connected via a switch SW to the PCS panel 30. In this embodiment, a plurality of (three) storage battery panels 20A are connected in parallel to one PCS panel 30A.

[0024] The PCS panel 30A includes a power control unit 40A, a switch SW, a control device 50A, and a housing 60 that houses these components. The power control unit 40A is connected to an interconnection line L1 of the power system 1 via the switch SW.

[0025] As shown in FIG. 3, the power control unit 40A includes a DC / DC converter 41, a link capacitor 42, an inverter 43, a current sensor 44, an LC filter 45, and a switch 46.

[0026] The power control unit 40A is a bidirectional power converter capable of inverse conversion operation (DC to AC) and forward conversion operation (AC to DC).

[0027] The inverse conversion operation (DC to AC) of the power control unit 40A allows the battery panel 20A to be discharged and AC power to be supplied to the power grid 1. The forward conversion operation (AC to DC) of the power control unit 40A allows the battery panel 20A to be charged with AC power from the power grid 1.

[0028] In this embodiment, a plurality of power control units 40A are provided in parallel to ensure the capacity of the PCS board 30A.

[0029] The control device 50A includes, for example, a CPU (Central Processing Unit) and a memory for storing various data. The control device 50A controls the power control unit 40A in response to commands from a higher-level device 100 such as an EMS (Energy Management System) and adjusts the supply and demand of power.

[0030] Specifically, when the demand for electricity is lower than the supply, the excess electricity is used to charge the battery panel 20A of the energy storage system 10A, and when the demand for electricity exceeds the supply, the power shortage is compensated for by discharging the battery panel 20A of the energy storage system 10A.

[0031] As described above, the energy storage system 10A can improve the efficiency of energy use and contribute to energy conservation by exchanging power with the power grid 1 and adjusting supply and demand.

[0032] As shown in FIGS. 1 and 2, this system includes three energy storage systems 10A to 10C, and control devices 50A to 50C of the energy storage systems 10A to 10C are connected by a communication line L2.

[0033] The three control devices 50A to 50C cooperate through mutual communication to control the entire energy storage systems 10A to 10C. By adjusting the supply and demand of electricity using the three parallel energy storage systems 10A to 10C, it is possible to adjust three times the amount of energy compared to a single system.

[0034] The control system is not limited to the above, and an integrated control device that integrates the three control devices 50A to 50C may be separately installed. The integrated control device may control the entire energy storage system 10A to 10C via the three control devices 50A to 50C (including the control of charging and discharging when measuring the full charge capacity).

[0035] 2. Estimation of full charge capacity of battery panel Since the full charge capacity [Ah] of the storage battery panels 20A to 20C decreases due to aging and other factors, it is desirable to periodically measure the full charge capacity [Ah] to understand the condition. Below, we will explain how to measure the full charge capacity [Ah] with reference to the measurement flow of the full charge capacity [Ah] in Figure 4.

[0036] The flow of measuring the full charge capacity [Ah] is made up of five steps S10 to S50, and is executed by the control device 50A, for example, every time a predetermined period of time elapses.

[0037] When a predetermined period has elapsed since the previous measurement and the measurement flow for the full charge capacity [Ah] is started, the control device 50A first determines in S10 whether the energy storage systems 10A to 10C are adjusting the supply and demand of power.

[0038] If supply and demand adjustment is in progress, the process proceeds to S20 and enters a standby state. During standby, the control device 50A determines the progress of supply and demand adjustment based on the energy adjustment amount (I×T). When the energy adjustment amount (I×T) reaches the command value, it can be determined that supply and demand adjustment has ended. I is current, and T is time.

[0039] Then, when the power supply and demand adjustment is completed, the control device 50A executes S30 to S50 and measures the full charge capacity [Ah] of the storage battery panel 20A. If supply and demand adjustment is not being performed, S20 is not executed, and the process immediately shifts to S30 to S50, where the full charge capacity [Ah] is measured.

[0040] Specifically, in S30, the control device 50A discharges the battery panel 20A via the power control unit 40A, as shown in Fig. 5. In parallel with the discharge of the battery panel 20A, the control device 50A sends a charge instruction to the control devices 50B and 50C of the other energy storage systems 10B and 10C, and charges the battery panels 20B and 20C of the other energy storage systems 10B and 10C by discharging the battery panel 20A to be measured.

[0041] The control device 50A monitors the voltage of the battery panel 20A during discharge, and when the battery panel 20A being measured reaches a predetermined discharge cut-off voltage, it determines that the battery panel 20A has reached a fully discharged state and stops discharging. The fully discharged state is a state in which the battery has discharged down to the discharge cut-off voltage (the lower limit voltage at which discharge can be safely performed). The fully discharged state may be determined by other methods.

[0042] After that, the process proceeds to S40. When the process proceeds to S40, the control device 50A reverses the charge and discharge as shown in Fig. 6, sends discharge instructions to the control devices 50B and 50C of the other energy storage systems 10B and 10C, and charges the fully discharged storage battery panel 20A by discharging the storage battery panels 20B and 20C of the other energy storage systems 10B and 10C.

[0043] The control device 50A monitors the voltage and current of the battery panel 20A during charging, and charges the fully discharged battery panel 20A until it is fully charged (a state in which further charging is not possible). In this embodiment, the battery panel 20A is determined to be fully charged when it reaches a predetermined upper limit voltage, the current value falls below a predetermined value, and a predetermined time has passed. The reason for waiting the predetermined time to determine that the battery panel 20A is fully charged is to perform so-called forced charging (charging that approaches SOC 100% by small-scale charging). If forced charging is not performed, full charge may be determined when the current value reaches a predetermined value, without waiting for the predetermined time to pass. The method of determining the full charge state is not limited to the method exemplified in the embodiment, and it can also be determined based on voltage alone.

[0044] Thereafter, the process proceeds to S50, where the control device 50A calculates the full charge capacity [Ah] of the battery panel 20A based on the integrated current value during charging of the battery panel 20A from a fully discharged state to a fully charged state, as shown in Fig. 7. The integrated current value may be a value measured by the monitoring unit 23 installed in the battery panel 20A, or a value measured by the current sensor 44 installed in the power control unit 40A.

[0045] The full charge capacity [Ah] may be measured by simultaneously charging and discharging the three battery panels 20A-1 to 20A-3 as shown in Fig. 8A, or by charging and discharging the three battery panels 20A-1 to 20A-3 one by one as shown in Fig. 8B.

[0046] After measuring the full charge capacity of the battery panel 20A, the control device 50A sends a measurement instruction for the full charge capacity [Ah] to the control devices 50B and 50C of the other energy storage systems. Then, upon receiving the measurement instruction, the control devices 50B and 50C measure the full charge capacity [Ah] of the battery panel 20B and the full charge capacity [Ah] of the battery panel 20C using the same measurement method as that used for the battery panel 20A.

[0047] As a result of the above, it is possible to measure the full charge capacities [Ah] of the battery panels 20A to 20C for the three energy storage systems 10A to 10C.

[0048] 3.Effectiveness The energy storage system 10 measures the full charge capacity [Ah] by charging and discharging the battery panels 20A to 20C and changing them from a fully discharged state to a fully charged state. The state of the battery panels 20A to 20C can be determined from the measurement result of the full charge capacity, which can be useful for maintenance of the battery panels 20A to 20C.

[0049] When measuring the full charge capacity [Ah], the battery panels 20A-20C are charged from a fully discharged state to a fully charged state using the power control units 40A-40C for adjusting supply and demand, so a power control unit dedicated to measuring the full charge capacity can be omitted.Furthermore, the branch lines and switches for measuring the full charge capacity can also be omitted, which simplifies the system and provides cost benefits.

[0050] This technology can also be applied to a system that has a power control unit dedicated to measuring full charge capacity. In this case, even if some kind of trouble occurs in the power control unit dedicated to measuring full charge capacity, it is possible to measure full charge capacity [Ah] using power control units 40A to 40C for supply and demand adjustment.

[0051] The energy storage system 10 prioritizes power supply and demand adjustment and does not measure the full charge capacity [Ah] during power supply and demand adjustment. By prioritizing power supply and demand adjustment, it is possible to suppress a decrease in energy utilization efficiency and contribute to energy conservation. With this configuration, by prioritizing power supply and demand adjustment over full charge capacity measurement, not only is it possible to achieve a power source with high flexibility in supply and demand adjustment, but it is also possible to flexibly measure the full charge capacity, enabling efficient operation. Furthermore, by knowing the exact full charge capacity, it is possible to reduce the risk of not being able to adjust supply and demand when it was thought possible, and to accurately respond to requests from the upper EMS.

[0052] Being able to accurately respond to requests from the host EMS helps adjust power supply and demand, enabling energy management for the entire system. In the power trading market, operations can be performed according to plan based on the amount of power that has been agreed upon in advance, which has the added benefit of eliminating penalties if the amount falls short of the plan. In addition, because the degree of deterioration can be determined from the measurement results of the full charge state, preventive maintenance of the battery panel 20 is possible, making it clear when to replace the battery panel 20 and making it easier to formulate business plans. Furthermore, it is expected to contribute to BCP (Business Continuity Planning: a business continuity plan for companies and organizations in emergencies such as disasters).

[0053] When measuring the full charge capacity [Ah], the energy storage system 10 charges the battery panel 20A of the energy storage system 10A being measured from a fully discharged state to a fully charged state by discharging the battery panels 20B and 20C of the other energy storage systems 10B and 10C.

[0054] In other words, by sharing energy (power) among multiple energy storage systems 10A, 10B, and 10C connected in parallel, the battery panel 20A, whose full charge capacity is to be measured, is changed between a fully discharged state and a fully charged state, and the full charge capacity [Ah] is measured. By doing this, there is almost no change in the energy of the entire energy storage system before and after charging (as well as before and after discharging). Therefore, the full charge capacity [Ah] of the battery panels 20A to 20C can be measured without energy loss.

[0055] The energy storage system 10 can measure the full charge capacity [Ah] without switching the current path when adjusting the power supply and demand, simply by controlling the power control unit 40. This makes it easy to switch between adjusting the power supply and demand and measuring the full charge capacity, and has the advantage of being able to reduce the number of switch components required to switch the current path.

[0056] <Other embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included within the technical scope of the present invention.

[0057] (1) In the above embodiment, a configuration in which three energy storage systems 10A to 10C are installed side by side is shown as in Figures 1 and 2. However, the present technology is not limited to this, and can be applied to a single energy storage system 10A as shown in Figure 9.

[0058] (2) In the above embodiment, when measuring the full charge capacity [Ah], the power control unit 40 for supply and demand adjustment is used to interchange (charge and discharge) energy with the storage battery panels 20A to 20C of the other energy storage systems 10A to 10C, thereby changing the storage battery panel 20A to 20C being measured from a fully discharged state to a fully charged state. This is not a limitation, and for example, as shown in FIG. 9 , the storage battery panel 20A may be changed from a fully discharged state to a fully charged state by interchange (charge and discharge) energy with the power grid 1. Furthermore, the storage battery panel 20A may be changed from a fully discharged state to a fully charged state by interchange (charge and discharge) energy with the load 110 or the generator 120 connected to the interconnection line L1.

[0059] (3) In the embodiment, the full charge capacity of the battery panel 20A is measured by the integrated value of the current while the battery panel 20A changes from a fully discharged state to a fully charged state. However, this is not limited to this, and the full charge capacity of the battery panel 20A may be measured by the integrated value of the current while the battery panel 20A changes from a fully charged state to a fully discharged state. The same applies to the battery panels 20B and 20C.

[0060] (4) In the embodiment, three power control units 40A are provided in parallel, but the number of power control units 40A may be one. The same applies to the battery panel 20A.

[0061] (5) In the embodiment, the full charge capacity is measured periodically, but it may be measured at a predetermined timing, such as after adjusting the supply and demand of power. Furthermore, if an instruction to adjust the supply and demand of power is received from the upper device 100 while measuring the full charge capacity, the measurement of the full charge capacity may be temporarily stopped and may be performed again after adjusting the demand.

[0062] (6) In the embodiment, the battery panel 20 is charged and discharged during a non-adjustment period when power demand adjustment is not being performed, and the full charge capacity is measured. During power demand adjustment, the battery panel 20 to be measured may be charged and discharged preferentially over other battery panels 20, and the full charge capacity [Ah] may be measured by changing the battery panel 20 from a fully discharged state to a fully charged state, or from a fully charged state to a fully discharged state.

[0063] For example, as shown in Figure 10, two energy storage systems 10A and 10B are pre-adjusted such that the battery panel 20A of one energy storage system 10A is fully discharged and the battery panel 20B of the other energy storage system 10B is fully charged. When a command to adjust supply and demand due to an excess supply of power is received from the upper device 100, the energy storage system 10A is connected to the grid (10B is not connected) and charged preferentially, and the battery panel 20A is changed from a fully discharged state to a fully charged state. The full charge capacity of the battery panel can be measured from the integrated current value at that time. Conversely, when a command to adjust supply and demand due to an excess demand is received, the energy storage system 10B is connected to the grid (10A is not connected) and discharged preferentially, and the battery panel 20B is changed from a fully charged state to a fully discharged state. The full charge capacity of the battery panel 20B can be measured from the integrated current value at that time.

[0064] 1 Power system 10A~10C Energy Storage System 20A~20C storage battery board 30A~30C PCS board 40A~40C Power control unit (power control unit for adjusting supply and demand) 50A~50C control device

Claims

1. A grid-connected energy storage system, one or more battery panels; a power control unit for adjusting supply and demand of power by charging and discharging the battery panel; a control device; The control device The battery panel is charged from a fully discharged state to a fully charged state or discharged from a fully charged state to a fully discharged state by the power control unit for adjusting supply and demand, and measuring a full charge capacity of the battery panel based on a first current integration value during a transition of the battery panel from a fully discharged state to a fully charged state or a second current integration value during a transition of the battery panel from a fully charged state to a fully discharged state.

2. 10. The energy storage system of claim 1, The control device prioritizes adjusting the supply and demand of electricity over measuring the full charge capacity.

3. An energy storage system in which a plurality of the energy storage systems according to claim 1 or 2 are connected in parallel, An energy storage system in which the full charge capacity is measured by changing the state of the battery panel whose full charge capacity is to be measured between a fully discharged state and a fully charged state by exchanging energy between a plurality of the energy storage systems connected in parallel.

4. An energy storage system in which a plurality of the energy storage systems according to claim 1 or 2 are connected in parallel, During adjustment of power supply and demand, the energy storage system changes from a fully discharged state to a fully charged state or from a fully charged state to a fully discharged state by preferentially charging and discharging the battery panel of an energy storage system among the plurality of energy storage systems whose full charge capacity is to be measured over the battery panel of an energy storage system whose full charge capacity is not to be measured.

5. A method for measuring the full charge capacity of a battery panel, comprising: The battery panel is charged from a fully discharged state to a fully charged state or discharged from a fully charged state to a fully discharged state by a power control unit for adjusting supply and demand, A method for measuring the full charge capacity of a battery panel, measuring the full charge capacity of the battery panel based on a first current integrated value during the change of the battery panel from a fully discharged state to a fully charged state or a second current integrated value during the change of the battery panel from a fully charged state to a fully discharged state.

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