Storage battery control device and electricity storage system

Abstract

This string system controller (SSC) selectively executes one of standard slope control and shortest slope control, said standard slope control individually calculating a string charge / discharge power instruction value for each predetermined cycle for each string controller (SC1 to SCx) in accordance with an electricity storage system charge / discharge power instruction value and individually transmitting the string charge / discharge power instruction values to the string controllers (SC1 to SCx) for each predetermined cycle, said shortest slope control calculating a string charge / discharge power instruction value common to the plurality of string controllers (SC1 to SCx) in accordance with the electricity storage system charge / discharge power instruction value and simultaneously transmitting the common string charge / discharge power instruction value to the plurality of string controllers (SC1 to SCx). Thus, the charge / discharge power of the entire electricity storage system (1) is changed from a current value to a target value.

Description

Battery control device and power storage system

[0001] The present invention relates to a storage battery control device and a power storage system.

[0002] A known power storage system includes a plurality of battery packs connected in parallel to a power supply target and a power grid via a plurality of power conditioning systems (PCSs) (see Patent Document 1). The power storage system described in Patent Document 1 includes an energy management system (EMS), a plurality of battery management units (BMUs), a plurality of state of charge (SOC) sensors, and the like. The EMS transmits a power instruction value to one of the plurality of BMUs (master BMU). The master BMU sets charge / discharge instruction values ​​for all battery packs and transmits the set charge / discharge instruction values ​​to all slave BMUs. Each slave BMU controls the charge / discharge amount of each battery pack based on the received charge / discharge instruction value and the SOC of the battery pack estimated by SOC estimation.

[0003] Also, a system for controlling the discharge of a storage string in which multiple storage batteries are connected in series is known that bypasses a storage battery that cannot discharge the required current and discharges the other storage batteries (see Patent Document 2). Furthermore, a system for controlling the charging of a storage string in which multiple storage batteries are connected in series is known that bypasses a storage battery that cannot charge the input current and charges the other storage batteries (see Patent Document 3). The storage systems described in Patent Documents 2 and 3 include a first switch that connects or disconnects the storage batteries to or from each other, and a second switch that connects or disconnects the bypass line.

[0004] Japanese Patent Publication No. 2016-167928 Japanese Patent Publication No. 2013-31247 Japanese Patent Publication No. 2013-31249

[0005] If the battery pack of the power storage system described in Patent Document 1 is used in the power storage strings of the systems described in Patent Documents 2 and 3, complex charge and discharge control is required, which results in a huge amount of communication between the control devices and long communication times. As a result, responsiveness to charge and discharge commands from the upper system is sacrificed, making it difficult to control the power receiving point, which requires a high-speed response.

[0006] In view of the above circumstances, an object of the present invention is to provide a battery control device and a power storage system in which a plurality of power storage strings are connected in parallel, which can improve responsiveness to charge / discharge instructions.

[0007] The battery control device of the present invention is a battery control device for controlling a battery system including a plurality of power storage strings connected in parallel, and includes a plurality of first control units provided for each of the power storage strings and controlling charge / discharge power of the corresponding power storage string; and a second control unit that receives a first charge / discharge power instruction value that is an instruction value for charge / discharge power of the entire power storage system from a higher-level control unit, calculates a second charge / discharge power instruction value that is an instruction value for charge / discharge power for each of the power storage strings in accordance with the received first charge / discharge power instruction value, and transmits the calculated second charge / discharge power instruction value to the corresponding first control unit, and the second control unit individually calculates the second charge / discharge power instruction value for each of the first control units for each predetermined period in accordance with the first charge / discharge power instruction value received from the higher-level control unit. and individually transmitting the calculated second charge / discharge power instruction value to the first control unit at each predetermined period; or second control calculating the second charge / discharge power instruction value common to the plurality of first control units according to the first charge / discharge power instruction value received from the higher-level control unit and simultaneously transmitting the calculated common second charge / discharge power instruction value to the plurality of first control units, thereby changing the charge / discharge power of the entire power storage system from a current value to a target value, and after executing the first control or the second control, calculating the second charge / discharge power instruction value individually for each first control unit and individually transmitting the calculated second charge / discharge power instruction value to the first control unit, thereby executing third control adjusting the charge / discharge power of the plurality of power storage strings.

[0008] The present invention provides a power storage system comprising a plurality of power storage strings connected in parallel, and a storage battery control device that controls charge / discharge power of the plurality of power storage strings, wherein the storage battery control device comprises a plurality of first control units that are provided for the power storage strings, and control the charge / discharge power of the corresponding power storage strings, and a second control unit that receives a first charge / discharge power instruction value that is an instruction value for charge / discharge power of the entire power storage system from a higher-level control unit, calculates a second charge / discharge power instruction value that is an instruction value for charge / discharge power for each of the power storage strings in accordance with the received first charge / discharge power instruction value, and transmits the calculated second charge / discharge power instruction value to the corresponding first control unit, and the second control unit controls the second charge / discharge power instruction value for each of the power storage strings in accordance with the first charge / discharge power instruction value received from the higher-level control unit, and a third control is executed to adjust the charge / discharge power of the plurality of power storage strings by selectively executing one of a first control for calculating an instruction value individually for each of the first control units and transmitting the calculated second charge / discharge power instruction value individually to the first control unit at each predetermined period, and a second control for calculating a second charge / discharge power instruction value common to a plurality of the first control units according to the first charge / discharge power instruction value received from the higher-level control unit and transmitting the calculated common second charge / discharge power instruction value simultaneously to the plurality of first control units.

[0009] According to the present invention, it is possible to improve the responsiveness to charge / discharge instructions in a power storage system in which a plurality of power storage strings are connected in parallel.

[0010] FIG. 1 is a circuit diagram showing the circuit configuration of a power storage system including a battery control device according to one embodiment of the present invention. FIG. 2 is a block diagram showing the control configuration of the power storage system shown in FIG. 1. FIG. 3 is a flowchart for explaining processing by the string system controller shown in FIGS. 1 and 2. FIG. 4 is a graph explaining updating of the power storage system charge / discharge power instruction value and the string charge / discharge power instruction value of each string. FIG. 5 is a graph explaining updating of the power storage system charge / discharge power instruction value and the string charge / discharge power instruction value of each string. FIG. 6 is a table showing the power storage system discharge power instruction value and the string discharge power instruction value of each string at the start of standard slope control during the slope control period of the power storage system discharge power. FIG. 7 is a table showing the power storage system discharge power instruction value and the string discharge power instruction value of each string at the start of shortest slope control during the slope control period of the power storage system discharge power. FIG. 8 is a table showing the power storage system discharge power instruction value and the string discharge power instruction value of each string at the start of standard slope control of the string discharge power. Fig. 9 is a table showing the power storage system discharge power instruction value and the string discharge power instruction value of each string at the start of shortest slope control during the slope control period of the power storage system discharge power. Fig. 10 is a table showing the power storage system discharge power instruction value and the string discharge power instruction value of each string at the start of shortest slope control during the slope control period of the power storage system discharge power. Fig. 11 is a table showing the power storage system discharge power instruction value and the string discharge power instruction value of each string at the start of shortest slope control during the slope control period of the power storage system discharge power. Fig. 12 is a table showing the power storage system discharge power instruction value and the string discharge power instruction value of each string at the start of standard slope control of the string discharge power.

[0011] The present invention will be described below in accordance with preferred embodiments. Note that the present invention is not limited to the embodiments described below, and the embodiments can be modified as appropriate without departing from the spirit of the present invention. In addition, in the embodiments described below, some components are omitted from illustration and description, but for the details of the omitted technologies, publicly known or well-known technologies are applied as appropriate within the scope of not causing any contradictions with the content described below.

[0012] 1 is a circuit diagram showing the circuit configuration of a power storage system 1 including a battery control device 2 (see FIG. 2) according to one embodiment of the present invention. The power storage system 1 shown in this figure is a stationary power source and includes a string system 10 and a power storage system controller PSC.

[0013] The power storage system controller PSC is the highest-level control device in the power storage system 1, and communicates with the host server 7 (see FIG. 2) and the string system controller SSC to control the power storage system accessories 3 (see FIG. 2). The power storage system controller PSC also includes a display / input device (not shown) such as a touch panel that has a display function and an input function.

[0014] The string system 10 includes a plurality of strings St1 to Stx, a string bus 6, a string system controller SSC, and a plurality of string controllers SC1 to SCx. The string system controller SSC and the string controllers SC1 to SCx will be described later.

[0015] The multiple strings St1 to Stx are connected in parallel to each other and to an external system (not shown) via a string bus 6. Each string St1 to Stx includes a power converter PCS1 to PCSx, a string cutoff switch 11, multiple modules M1 to Mm, and multiple module controllers MC1 to MCm. The module controllers MC1 to MCm will be described later.

[0016] Each of the modules M1 to Mm includes a storage battery B1 to Bm, a bypass switch unit BSU1 to BSUm, and a voltage sensor 12. In each of the strings St1 to Stx, a plurality of storage batteries B1 to Bm are connected in series, and a bypass switch unit BSU1 to BSUm is provided for each of the storage batteries B1 to Bm. Each of the strings St1 to Stx also includes a current sensor 13, a voltage sensor 14, a fuse 15, the same number of temperature sensors (not shown) as the number of storage batteries B1 to Bm, and the same number of cell voltage sensors (not shown) as the number of storage battery cells.

[0017] The storage batteries B1 to Bm are secondary batteries such as lithium-ion batteries or lithium-ion capacitors, and are charged by receiving power from an external system via the power converters PCS1 to PCSx. The charged power is then discharged via the power converters PCS1 to PCSx to supply power to the external system. Although not particularly limited, the storage batteries B1 to Bm in this embodiment are refurbished secondhand storage batteries, and the degree of deterioration of each storage battery B1 to Bm varies. Note that the storage batteries B1 to Bm may be storage battery packs in which multiple storage battery modules are connected in series, or may be composed of a single storage battery cell.

[0018] Each bypass switch unit BSU1 to BSUm includes a bypass line BL and switches S1 and S2. The bypass line BL is a power line that bypasses each of the storage batteries B1 to Bm. The switch S1 is provided on the bypass line BL. This switch S1 is, for example, a mechanical switch, a semiconductor switch, or a relay. The switch S2 is provided between the positive electrode of each of the storage batteries B1 to Bm and one end of the bypass line BL. This switch S2 is, for example, a mechanical switch, a semiconductor switch, or a relay.

[0019] The starting battery B1 and the ending battery Bm are connected to an external system via power converters PCS1 to PCSx and a string bus 6. When the switch S1 is turned OFF and the switch S2 is turned ON in all of the bypass switch units BSU1 to BSUm, all of the batteries B1 to Bm are connected in series to the external system. On the other hand, when the switch S2 is turned OFF and the switch S1 is turned ON in any of the bypass switch units BSU1 to BSUm, the battery B1 to Bm corresponding to that bypass switch unit BSU1 to BSUm is bypassed.

[0020] The power converters PCS1 to PCSx are bidirectional converters and connected to a string bus 6. Furthermore, the positive electrode of the starting storage battery B1 and the negative electrode of the terminal storage battery Bm are connected to each of the power converters PCS1 to PCSx.

[0021] When charging the strings St1 to Stx, the power converters PCS1 to PCSx convert the voltage input from the string bus 6 according to the string charging power instruction value and output the converted voltage to the multiple storage batteries B1 to Bm. Here, the voltage on the strings St1 to Stx side changes according to the bypass state of the storage batteries B1 to Bm (the number of bypassed storage batteries B1 to Bm) and the charging state of the storage batteries B1 to Bm. Therefore, when charging the strings St1 to Stx, the power converters PCS1 to PCSx convert the voltage input from the string bus 6 to the voltage on the strings St1 to Stx side and output the converted voltage to the multiple storage batteries B1 to Bm.

[0022] When the strings St1 to Stx are being discharged, the power converters PCS1 to PCSx convert the voltages input from the batteries B1 to Bm according to the string discharge power instruction value and output the converted voltage to the string bus 6. The input voltages of the power converters PCS1 to PCSx during discharge vary depending on the bypass state of the batteries B1 to Bm and the charge state of the batteries B1 to Bm. This causes variations in the input voltages of the power converters PCS1 to PCSx among the strings St1 to Stx during discharge. Therefore, when the strings St1 to Stx are being discharged, the power converters PCS1 to PCSx convert the input voltages to voltages consistent with the other strings St1 to Stx and output the converted voltage to the string bus 6. When the current flowing through the string bus 6 is AC, the power converters PCS1 to PCSx are equipped with synchronization means for tracking instantaneous value changes.

[0023] Each string cutoff switch 11 is provided between each power converter PCS1 to PCSx and the string bus 6. This string cutoff switch 11 connects or disconnects the strings St1 to Stx to the string bus 6. In addition, each fuse 15 is a power fuse provided between each string cutoff switch 11 and the string bus 6.

[0024] The voltage sensor 12 is connected between the positive and negative terminals of each of the storage batteries B1 to Bm, detects the terminal voltage of each of the storage batteries B1 to Bm, and transmits a detection signal to each of the module controllers MC1 to MCm. The current sensor 13 is provided on the power line PL of each of the strings St1 to Stx, detects the charge / discharge current of each of the strings St1 to Stx (hereinafter, "string current"), and transmits a detection signal to each of the string controllers SC1 to SCx. The voltage sensor 14 is provided on the power line PL of each of the strings St1 to Stx, detects the total voltage of each of the strings St1 to Stx (hereinafter, "string total voltage"), and transmits a detection signal to each of the string controllers SC1 to SCx.

[0025] A temperature sensor is provided in each of the batteries B1 to Bm to detect the temperature of the battery and transmit a detection signal to the module controllers MC1 to MCm. A cell voltage sensor is provided in each of the batteries B1 to Bm to detect the voltage of the battery cell and transmit a detection signal to the module controllers MC1 to MCm.

[0026] Fig. 2 is a block diagram showing the control configuration of the power storage system 1 shown in Fig. 1. As shown in this figure, the power storage system 1 includes a storage battery control device 2. The storage battery control device 2 includes a plurality of first control devices 21 and a second control device 22. Each first control device 21 includes a string controller SC1 to SCx and a plurality of module controllers MC1 to MCm. The second control device 22 includes a power storage system controller PSC and a string system controller SSC.

[0027] The power storage system controller PSC, the string system controller SSC, the string controllers SC1 to SCx, and the module controllers MC1 to MCm are provided for each hierarchical level. The power storage system controller PSC corresponds to the hierarchical level of the top power storage system 1. The string system controller SSC corresponds to the hierarchical level of the string system 10, which is next to the hierarchical level of the power storage system 1. The string controllers SC1 to SCx correspond to the hierarchical levels of the strings St1 to Stx, which are next to the hierarchical level of the string system 10. The module controllers MC1 to MCm correspond to the hierarchical levels of the modules M1 to Mm (see FIG. 1 ), which are next to the hierarchical level of the strings St1 to Stx.

[0028] The power storage system controller PSC communicates with the host server 7 and the string system controller SSC to control and manage the power storage system auxiliaries 3. The host server 7 is provided in an aggregator facility or in power receiving equipment in a building, factory, etc. This host server 7 calculates a charge / discharge power instruction value for the entire power storage system 1 (hereinafter referred to as the power storage system charge / discharge power instruction value) according to the state of the power storage system 1 and the power demand on the demand side, and transmits the calculated value to the power storage system controller PSC.

[0029] Examples of the power storage system accessories 3 include a temperature sensor that detects the temperature of the installation environment of the power storage system 1, such as a container, and a fire extinguishing equipment (both not shown). If the detected value of the temperature sensor exceeds a threshold, the power storage system controller PSC determines that the temperature of the installation environment of the power storage system 1 is abnormal and outputs an abnormality notification to the display input device. In addition, the power storage system controller PSC monitors the operating state of the fire extinguishing equipment.

[0030] The storage system controller PSC receives information about the states of the strings St1 to Stx (hereinafter, string state information) and information about the state of the string system 10 (hereinafter, string system state information) from the string system controller SSC, and outputs the information to the upper server 7 and the display input device.

[0031] The states of strings St1 to Stx include operating states such as charging, discharging, resting, and maintenance, string current, total string voltage, SOC of strings St1 to Stx (hereinafter referred to as string SOC), SOH (State of Health) of strings St1 to Stx (hereinafter referred to as string SOH), and limit values ​​of charge / discharge power (or charge / discharge current) of strings St1 to Stx (hereinafter referred to as string charge / discharge power limit values).

[0032] The state of the string system 10 may include the current of the string bus 6 (see FIG. 1) (hereinafter referred to as the string bus current), the voltage of the string bus 6 (hereinafter referred to as the string bus voltage), the SOC of the string system 10 (hereinafter referred to as the string system SOC), the SOH of the string system 10 (hereinafter referred to as the string system SOH), and the limit value of the charge / discharge power (or charge / discharge current) of the string system 10 (hereinafter referred to as the string system charge / discharge power limit value).

[0033] The power storage system controller PSC estimates the state of the power storage system 1 based on the string state information and string system state information received from the string system controller SSC. Examples of the state of the power storage system 1 include an operating state such as charging, discharging, suspension, and maintenance, the SOC of the power storage system 1 (hereinafter referred to as power storage system SOC), and the SOH of the power storage system 1 (hereinafter referred to as power storage system SOH). The power storage system controller PSC outputs information about the estimated state of the power storage system 1 (hereinafter referred to as power storage system state information) to a display input device as necessary. Note that in this embodiment in which there is a single string system 10, the string system SOC is equal to the power storage system SOC, and the string SOH is equal to the power storage system SOH.

[0034] The power storage system controller PSC transmits information required for processing by the upper server 7 to the upper server 7. Examples of the information required for processing by the upper server 7 include the power storage system SOC, the power storage system SOH, and the string system charge / discharge power limit value. Here, the upper server 7 determines charge / discharge instructions corresponding to the power storage system 1 based on the "information required for processing by the upper server 7" received from the power storage system controller PSC, and transmits the instructions to the power storage system controller PSC. The charge / discharge instructions include, in addition to the power storage system charge / discharge power instruction value, control variables such as a constant voltage (CV) mode, a constant current (CC) mode, and a constant power (CP) mode, and an operation method such as an independent operation or a grid-connected operation.

[0035] The power storage system controller PSC transmits various instruction information inputted via the display input device by an operator or the like to the string system controller SSC. Examples of the instruction information that can be inputted via the display input device include an instruction to execute a maintenance / stop mode (hereinafter referred to as a maintenance / stop instruction), an instruction to forcibly execute charging / discharging, an instruction to forcibly execute state estimation, and the like.

[0036] Examples of maintenance / stop instructions include an instruction to forcibly operate the power storage system auxiliary device 3, the string system auxiliary device 4, and the string auxiliary device 5. By forcibly operating the power storage system auxiliary device 3, the string system auxiliary device 4, and the string auxiliary device 5, it becomes possible to check the operation of the power storage system auxiliary device 3, the string system auxiliary device 4, and the string auxiliary device 5.

[0037] An example of an instruction to forcibly perform charging / discharging is an instruction to specify a predetermined charging / discharging amount and forcibly perform charging / discharging in the power storage system 1. By specifying the predetermined charging / discharging amount and forcibly performing charging / discharging in the power storage system 1, it becomes possible to check whether the power storage system 1 can charge / discharge the specified predetermined charging / discharging amount.

[0038] An example of an instruction to forcibly execute state estimation is an instruction to specify a predetermined item of state estimation and forcibly execute state estimation in the power storage system 1. By specifying a predetermined item of state estimation and forcibly executing state estimation in the power storage system 1, it becomes possible to acquire, for example, state estimation items such as the string system SOH and the power storage system SOH at any time.

[0039] The string system controller SSC communicates with the power storage system controller PSC and the multiple string controllers SC1 to SCx, and controls and manages the string system auxiliaries 4. The string system auxiliaries 4 include a temperature sensor that detects the ambient temperature, a cooling device in the string system 10, a breaker for the string bus 6, a current sensor that detects the string bus current, a voltage sensor that detects the string bus voltage, and the like (all of which are not shown).

[0040] The string system controller SSC receives string status information from the string controllers SC1 to SCx. The status of the strings St1 to Stx includes an operating state such as charging, discharging, suspension, maintenance, etc., a string current, a string total voltage, a string SOC, a string SOH, a string charge / discharge power limit value, and a status of the string system auxiliary device 4. The status of the string system auxiliary device 4 includes a string bus current, a string bus voltage, etc.

[0041] The string system controller SSC estimates the state of the string system 10 based on the string state information received from the string controllers SC1 to SCx. Examples of the state of the string system 10 include the string bus current, the string bus voltage, the string system SOC, the string system SOH, and the string system charge / discharge power limit value. The state of the string system 10 may be estimated by the power storage system controller PSC. The power storage system controller PSC may receive the string state information from the string system controller SSC, estimate the state of the string system 10, and estimate the state of the power storage system 1 based on the estimation result.

[0042] For example, if the detected values ​​of the temperature sensor, current sensor, or voltage sensor or the estimated value of the state of the string system 10 exceed the threshold range, the string system controller SSC determines whether or not there is an abnormality in the string system 10, stops operation of the string system 10, or sends an abnormality notification to the storage system controller PSC.

[0043] The string system controller SSC transmits to the power storage system controller PSC information required for processing by the power storage system controller PSC, from among the information received from the string controllers SC1 to SCx and information estimated by itself. Examples of information required for processing by the power storage system controller PSC include the string system SOC, the string system SOH, and the string system charge / discharge power limit value.

[0044] Here, the power storage system controller PSC determines instructions corresponding to the string system 10 based on the "information required for processing by the power storage system controller PSC" received from the string system controller SSC, and transmits the instruction information to the string system controller SSC. These instructions include charge / discharge instructions for the string system 10 in the charge / discharge mode, instructions to individually control each part of the string system 10 in the maintenance mode (hereinafter referred to as individual control instructions), and state estimation instructions for the string system 10 in the state estimation mode. The charge / discharge instructions for the string system 10 in the charge / discharge mode include, in addition to string charge / discharge power instruction values ​​assigned to each string St1 to Stx, instructions for the slope control mode, constant voltage (CV) mode, constant current (CC) mode, and constant power (CP) mode control amounts, and operation methods such as independent operation / grid-connected operation, which will be described later. The individual control instructions for the string system 10 in the maintenance mode include instructions to individually control the string system auxiliaries 4, such as the power converters PCS1 to PCSx, cooling devices, and switches S1 and S2. The state estimation instructions to the string system 10 in the state estimation mode include instructions to execute predetermined controls necessary to estimate the states of the strings St1 to Stx.

[0045] The string system controller SSC receives instructions corresponding to the above-mentioned string system 10 from the power storage system controller PSC, and compares the currently received instruction with the previously received instruction to determine whether or not the operating state of the string system 10 needs to be updated. If the operating state of the string system 10 needs to be updated, the string system controller SSC determines the operating mode of each of the strings St1 to Stx, permission for a bypass request from each of the string controllers SC1 to SCx (hereinafter referred to as bypass permission), and a string charge / discharge power instruction value to be assigned to each of the strings St1 to Stx. Examples of the operating mode of each of the strings St1 to Stx include a charge / discharge mode, a state estimation mode, and a maintenance / stop mode.

[0046] Here, the string system controller SSC determines the operation mode, bypass permission, and string charge / discharge power instruction value for each string St1 to Stx based on the operation history of each string St1 to Stx from past to present. Examples of determining the operation mode, etc. based on the operation history from past to present include the following (1) to (4). (1) Determine whether to perform state estimation for each string St1 to Stx based on the timing of state estimation for each string St1 to Stx. (2) Determine whether to perform maintenance on each string St1 to Stx or charge / discharge each string St1 to Stx based on whether or not and when an abnormality was determined for each string St1 to Stx. (3) Determine the string charge / discharge power instruction value for each string St1 to Stx depending on whether or not a bypass request is received from each string controller SC1 to SCx. For example, the string charge / discharge power instruction value for the string St1 to Stx corresponding to the string controller SC1 to SCx that sent the bypass request is set to 0. After the bypass control of the strings St1 to Stx is completed, the string charge / discharge power instruction value for the strings St1 to Stx is increased. (4) The string charge / discharge power instruction value for each of the strings St1 to Stx is determined based on the string SOC, string SOH, and string total voltage of each of the strings St1 to Stx.

[0047] The string controllers SC1 to SCx communicate with the string system controller SSC and multiple module controllers MC1 to MCm to control and manage the string auxiliaries 5. The string auxiliaries 5 include power converters PCS1 to PCSx, a current sensor 13 that detects the string current, a voltage sensor 14 that detects the total string voltage, a string cutoff switch 11, and the like (see FIG. 1 for all of these).

[0048] The string controllers SC1 to SCx receive information about the state of each of the storage batteries B1 to Bm (hereinafter referred to as storage battery state information) from the module controllers MC1 to MCm. The state of each of the storage batteries B1 to Bm includes the temperature, current, voltage, and cell voltage of the storage batteries B1 to Bm, and the state of the bypass switch units BSU1 to BSUm.

[0049] The string controllers SC1 to SCx estimate the SOC, SOH, charge / discharge power limit values, etc. of the storage batteries B1 to Bm based on the storage battery state information received from the module controllers MC1 to MCm. The SOC, SOH, charge / discharge power limit values, etc. of the storage batteries B1 to Bm may be estimated by the module controllers MC1 to MCm. In this case, the module controllers MC1 to MCm simply transmit the estimation results to the string controllers SC1 to SCx.

[0050] The string controllers SC1 to SCx estimate the states of the strings St1 to Stx based on the storage battery state information received from the module controllers MC1 to MCm. Examples of the states of the strings St1 to Stx include the string SOH, the string SOC, and the string charge / discharge power limit value. The states of the strings St1 to Stx may be estimated by the string system controller SSC. In this case, the string controllers SC1 to SCx simply transmit the storage battery state information and the estimated results of the storage battery states to the string system controller SSC.

[0051] For example, when the detected values ​​of the current sensor 13 and the voltage sensor 14 or the estimated values ​​of the states of the strings St1 to Stx are outside the threshold ranges, the string controllers SC1 to SCx determine whether or not there is an abnormality in the strings St1 to Stx. In this case, the string controllers SC1 to SCx stop the operation of the strings St1 to Stx or send an abnormality notification to the string system controller SSC.

[0052] The string controllers SC1 to SCx transmit to the string system controller SSC information required for processing by the string system controller SSC, from among the information received from the module controllers MC1 to MCm and information estimated by themselves. Information required for processing by the string system controller SSC includes the temperature, current, voltage, SOC, SOH, charge / discharge power limit value, cell voltage, state of the bypass switch units BSU1 to BSUm, string SOC, string SOH, string charge / discharge power limit value, etc. of the storage batteries B1 to Bm.

[0053] Here, the string system controller SSC determines instructions corresponding to each of the strings St1 to Stx based on the "information required for processing by the string system controller SSC" received from the string controllers SC1 to SCx, and transmits the instruction information to the string controllers SC1 to SCx. These instructions include charge / discharge instructions for each of the strings St1 to Stx in the charge / discharge mode, individual control instructions for each of the strings St1 to Stx in the maintenance mode, and state estimation instructions for each of the strings St1 to Stx in the state estimation mode. Items of the charge / discharge instructions for each of the strings St1 to Stx in the charge / discharge mode include, in addition to string charge / discharge power instruction values, control amounts for constant voltage mode, constant current mode, and constant power mode, and operation methods such as independent operation / grid-connected operation. Items of the individual control instructions for each of the strings St1 to Stx in the maintenance mode include, for example, instructions to individually control the bypass switch units BSU1 to BSUm. The state estimation instruction items in the state estimation mode include charging and discharging at a constant current and recording the voltages between the terminals of the storage batteries B1 to Bm during this charging and discharging.

[0054] The string controllers SC1 to SCx receive instruction information corresponding to each of the strings St1 to Stx from the string system controller SSC and compare the currently received instruction information with the previously received instruction information to determine whether the bypass schedule for each of the strings St1 to Stx needs to be updated. The bypass schedule for each of the strings St1 to Stx is a plan for bypassing the storage batteries B1 to Bm by the bypass switch units BSU1 to BSUm and is determined based on predetermined criteria. The string controllers SC1 to SCx determine whether a switch from charging to discharging or from discharging to charging will occur in each of the strings St1 to Stx, and if such a switch occurs, determine that the bypass schedule needs to be updated. If the bypass schedule needs to be updated, the string controllers SC1 to SCx determine the bypass schedule for the storage batteries B1 to Bm based on the storage battery state information received from the module controllers MC1 to MCm and the estimated state of each of the storage batteries B1 to Bm.

[0055] On the other hand, the string controllers SC1 to SCx determine whether or not control of the string charge / discharge power is necessary by comparing the current and previous battery state information received from the module controllers MC1 to MCm with the estimated state of each of the batteries B1 to Bm. If control of the string charge / discharge power is necessary, the string controllers SC1 to SCx control the power converters PCS1 to PCSx.

[0056] The string controllers SC1 to SCx control the power converters PCS1 to PCSx in accordance with the string charge / discharge power instruction value received from the string system controller SSC.

[0057] When the string controllers SC1 to SCx receive a maintenance / stop command from the string system controller SSC, they analyze the received maintenance / stop command and determine the type of maintenance to be performed, such as individual control, self-diagnosis, and replacement of the storage batteries B1 to Bm (hereinafter referred to as storage battery replacement).

[0058] Examples of individual control include control of individually turning on / off the string cutoff switch 11 and the cooling devices in the strings St1 to Stx. Examples of self-diagnosis include abnormality determination, which detects abnormalities that are difficult to detect when operating in the state estimation mode or charge / discharge mode. Examples of such abnormality determination include performing special control on the string auxiliaries 5, such as the power converters PCS1 to PCSx, and the bypass switch units BSU1 to BSUm, and acquiring the responses from various sensors to determine whether or not an abnormality exists. Examples of battery replacement include providing guidance on replacing batteries B1 to Bm that have deteriorated or are faulty. When replacing batteries, a work guide is displayed on the display / input device of the power storage system controller PSC, and the power storage system 1 performs necessary control, such as shutting down the strings St1 to Stx whose batteries are to be replaced. Note that the strings St1 to Stx whose batteries are not to be replaced may be operated in the charge / discharge mode. After the battery replacement is completed, the strings St1 to Stx whose batteries have been replaced are operated in a state estimation mode, and battery state information is transmitted from the module controllers MC1 to MCm to the string controllers SC1 to SCx. Note that the strings St1 to Stx whose batteries have not been replaced may be operated in a charge / discharge mode.

[0059] When the string controllers SC1 to SCx receive a state estimation instruction from the string system controller SSC, they compare the currently received string charge / discharge power instruction value with the previously received string charge / discharge power instruction value and determine whether there has been a change. If there is a change in the string charge / discharge power instruction value between the previous and current times, the string controllers SC1 to SCx control the string auxiliary device 5 and the bypass switch units BSU1 to BSUm in a predetermined manner so that the states of the strings St1 to Stx can be estimated. Examples of a method for controlling the string auxiliary device 5 during execution of the state estimation mode include turning on the string cutoff switch 11 and performing constant current control on the power converters PCS1 to PCSx. Examples of a method for controlling the bypass switch units BSU1 to BSUm during execution of the state estimation mode include sequentially bypassing the storage batteries B1 to Bm that have become fully discharged during discharging.

[0060] The string controllers SC1 to SCx record the battery state information received from the module controllers MC1 to MCm. Furthermore, the string controllers SC1 to SCx update parameters used for estimating the state as needed, based on the battery state information received from the module controllers MC1 to MCm. These parameters include the SOH of the batteries B1 to Bm, a map of charge / discharge limit values ​​for the batteries B1 to Bm, and SOC-OCV characteristics.

[0061] The module controllers MC1 to MCm communicate with the string controllers SC1 to SCx to control and manage module auxiliaries (not shown). These module auxiliaries include bypass switch units BSU1 to BSUm and various sensors. The various sensors include voltage sensors that detect the voltages of the storage batteries B1 to Bm, current sensors that detect the currents of the storage batteries B1 to Bm, temperature sensors that detect the temperatures of the storage batteries B1 to Bm, and cell voltage sensors that detect the cell voltages.

[0062] The module controllers MC1 to MCm receive battery status information from a cell monitoring unit (not shown) or the like. The status of the batteries B1 to Bm includes the total voltage of the batteries B1 to Bm, the temperature of the batteries B1 to Bm, and the cell voltage. The cell monitoring unit receives detection signals from various sensors, such as a module voltage sensor that detects the module voltage, a cell voltage sensor that detects the cell voltage, and a module temperature sensor that detects the module temperature. The cell monitoring unit may be configured as a standalone unit, or may be configured using a battery cell monitoring IC (Integrated Circuit) within the module controllers MC1 to MCm.

[0063] The module controllers MC1 to MCm receive battery state information from the above-mentioned cell monitoring units or various sensors of the batteries B1 to Bm, and estimate the states of the batteries B1 to Bm based on the received information. The estimated states of the batteries B1 to Bm include the SOC, SOH, and charge / discharge power limit values ​​of the batteries B1 to Bm. The states of the batteries B1 to Bm may be estimated by the string controllers SC1 to SCx.

[0064] For example, if the detected values ​​of the voltage sensors, cell voltage sensors, and module temperature sensors or the estimated values ​​of the states of the storage batteries B1-Bm are outside the threshold ranges, the module controllers MC1-MCm determine whether or not there is an abnormality in the storage batteries B1-Bm.The module controllers MC1-MCm then shut off the storage batteries B1-Bm determined to be abnormal using the bypass switch units BSU1-BSUm, or send an abnormality notification to the string controllers SC1-SCx.

[0065] The module controllers MC1 to MCm transmit to the string controllers SC1 to SCx information required for processing by higher-level controllers such as the string controllers SC1 to SCx, from among information received from the cell monitoring units or various sensors and information estimated by themselves. Information required for processing by the string controllers SC1 to SCx includes the temperature, current, voltage, SOC, SOH, charge / discharge power limit value, cell voltage, and the state of the bypass switch units BSU1 to BSUm of the storage batteries B1 to Bm.

[0066] Here, the string controllers SC1 to SCx determine instructions corresponding to each of the storage batteries B1 to Bm based on the "information required for the processing of the string controllers SC1 to SCx" received from the module controllers MC1 to MCm, and transmit the instruction information to the module controllers MC1 to MCm. These instructions include bypass control of the storage batteries B1 to Bm by the bypass switch units BSU1 to BSUm, cut-off control of the storage batteries B1 to Bm by the bypass switch units BSU1 to BSUm, etc.

[0067] If there is a change in the instruction information received from the string controllers SC1 to SCx between the current time and the previous time, the module controllers MC1 to MCm control the bypass switch units BSU1 to BSUm to execute the bypass control or shutoff control described above. Furthermore, if there is a change in the information received from the cell monitoring units or various sensors, or in the information estimated by the module controllers MC1 to MCm, the module controllers MC1 to MCm execute exceptional control as necessary, independent of instructions from a higher-level controller. Furthermore, the module controllers MC1 to MCm send instructions to the cell monitoring units to execute cell balancing for the storage batteries B1 to Bm.

[0068] Fig. 3 is a flowchart for explaining the processing of the string system controller SSC shown in Fig. 1 and Fig. 2. When the power storage system 1 is operated, the processing of step S1 is started, and while the power storage system 1 is operating, the processing of steps S2 to S16 is repeated.

[0069] In step S1, the string system controller SSC initializes various parameters, and then in step S2, the string system controller SSC receives string status information from each of the string controllers SC1 to SCx.

[0070] Next, in step S3, the string system controller SSC receives string system accessory status information (string bus voltage, string bus current, etc.) from the string system accessory 4.

[0071] Next, in step S4, the string system controller SSC estimates the state of the string system 10 based on the string state information received in step S2 and the string system accessory state information received in step S3. Note that the estimation of the state of the string system 10 may be performed by the power storage system controller PSC, and the estimation result may be transmitted from the power storage system controller PSC to the string system controller SSC or the upper server 7.

[0072] Next, in step S5, the string system controller SSC analyzes the information received or estimated in steps S2 to S4 and determines whether or not there is an abnormality in the string system 10. The string system controller SSC determines whether or not there is an abnormality in the string system 10, for example, by comparing the various detected values ​​or estimated values ​​received or estimated in steps S2 to S4 with threshold values.

[0073] Next, in step S6, the string system controller SSC transmits to the power storage system controller PSC information (string system state information) required for processing by the power storage system controller PSC and the upper server 7, out of the information received, estimated, or determined in steps S2 to S5. Next, in step S7, the string system controller SSC receives an instruction transmitted from the power storage system controller PSC. Here, the power storage system controller PSC determines an instruction corresponding to the string system 10 (such as a power storage system charge / discharge power instruction value in charge / discharge mode) based on the information received from the string system controller SSC in step S6, and transmits the instruction to the string system controller SSC in step S7.

[0074] Next, in step S8, the string system controller SSC compares the current and previous instructions received from the power storage system controller PSC and determines whether the operating states of the strings St1 to Stx need to be updated. For example, if there is a change between the previous and current storage system charge / discharge power instruction value received from the power storage system controller PSC, the string system controller SSC determines that the operating states of the strings St1 to Stx need to be updated. Furthermore, for example, if there is a change between the previous and current individual control instructions in the maintenance mode received from the power storage system controller PSC, the string system controller SSC determines that the operating states of the strings St1 to Stx need to be updated. If a positive determination is made in step S8, the process proceeds to step S9, and if a negative determination is made in step S8, the process proceeds to step S2.

[0075] Next, in step S9, the string system controller SSC determines instructions for each of the string controllers SC1 to SCx in accordance with predetermined conditions. Examples of the predetermined conditions include the state of each of the strings St1 to Stx acquired in step S2, the operation history of each of the strings St1 to Stx from past to present, and various instructions input via the display / input device. Examples of instructions for each of the string controllers SC1 to SCx include the operation mode of each of the strings St1 to Stx (state estimation mode, charge / discharge mode, maintenance / stop mode, etc.), whether to allow or disallow bypass requests from each of the string controllers SC1 to SCx, and the allocation of string charge / discharge power instruction values ​​to each of the strings St1 to Stx. If a maintenance / stop instruction has been input via the display / input device, the string system controller SSC determines the instruction for each of the strings St1 to Stx to be a maintenance / stop instruction. Similarly, when an instruction to forcibly perform charging / discharging or state estimation is input via the display / input device of the storage system controller PSC, the string system controller SSC determines the instruction for each string St1 to Stx to be a charging / discharging instruction or a state estimation instruction.

[0076] Next, in step S10, the string system controller SSC sets a count value m for managing the transmission of instruction information to the string controllers SC1 to SCx to an initial value (m=1). Next, in step S11, the string system controller SSC determines whether the operation mode of the string St1 to Stx to which the instruction is addressed is the charge / discharge mode, the state estimation mode, or the maintenance / stop mode. If the operation mode is the charge / discharge mode, the process proceeds to step S13; if the operation mode is the state estimation mode, the process proceeds to step S12; and if the operation mode is the maintenance / stop mode, the process proceeds to step S14.

[0077] In step S12, the string system controller SSC transmits a state estimation instruction to the target string controllers SC1 to SCx. The state estimation instruction includes, for example, whether the state estimation mode flag is ON, a string charge / discharge power instruction value, and bypass permission / prohibition. In the state estimation mode for each string St1 to Stx, for example, constant current discharge is performed, and data such as voltage is acquired during the discharge. Here, if there is variation in the degree of deterioration of the storage batteries B1 to Bm in each string St1 to Stx, the storage batteries B1 to Bm are fully discharged in descending order of deterioration. Then, each time a storage battery B1 to Bm is fully discharged, a bypass request is transmitted from the module controllers MC1 to MCm. The string system controller SSC then determines whether to grant bypass permission in response to the received bypass request, and transmits a bypass permission / prohibition notification to the string controllers SC1 to SCx.

[0078] Meanwhile, in step S13, the string system controller SSC transmits a charge / discharge instruction to the target string controllers SC1 to SCx. The charge / discharge instruction items include whether the charge / discharge mode flag is ON, the string charge / discharge power instruction value, and whether bypass is permitted or not permitted. If any of the storage batteries B1 to Bm is fully discharged or fully charged, a bypass request is transmitted from the module controllers MC1 to MCm. The string system controller SSC then determines whether to notify bypass permission in response to the received bypass request, and transmits a notification of bypass permission or not permitted to the string controllers SC1 to SCx.

[0079] Meanwhile, in step S14, the string system controller SSC transmits a maintenance / stop instruction to the target string controllers SC1 to SCx. Examples of the maintenance / stop instruction include turning on the maintenance / stop flag, various instructions, and bypass permission / prohibition. The various instructions correspond to instructions input via the display / input device. For example, an instruction to forcibly operate the power storage system auxiliary 3, the string system auxiliary 4, the string auxiliary 5, and the bypass switch units BSU1 to BSUm is included. Here, when an instruction to forcibly operate the bypass switch units BSU1 to BSUm is input via the display / input device, the string system controller SSC transmits a bypass permission / prohibition instruction to the string controllers SC1 to SCx. The maintenance / stop instruction is not limited to being input via the display / input device; it may also be transmitted when an abnormality occurs or periodically.

[0080] The process proceeds from steps S12, S13, and S14 to step S15, where the string system controller SSC increments a count value m for managing the transmission of instruction information to the string controllers SC1 to SCx. Next, in step S16, the string system controller SSC determines whether or not the transmission of instructions to all of the string controllers SC1 to SCx has been completed. Specifically, the string system controller SSC determines whether or not the count value m has reached the total number x of the string controllers SC1 to SCx. If a negative determination is made in step S16, the process proceeds to step S11, and steps S11 to S16 are repeated. On the other hand, if a positive determination is made in step S16, the process proceeds to step S2, and the processes of steps S2 to S16 are repeated while the power storage system 1 is operating.

[0081] 4 and 5 are graphs illustrating updating of the power storage system charge / discharge power instruction value and the string charge / discharge power instruction values ​​of the strings St1 to Stx. As shown in these graphs, the power storage system charge / discharge power instruction value is updated so as to change from the current value to the target value over a predetermined period (the slope control period for the power storage system charge / discharge power in the figures).

[0082] Furthermore, after the storage system charge / discharge power instruction value is updated, the storage system charge / discharge power instruction value is maintained, while the string charge / discharge power instruction value of each string St1 to Stx is updated. This updating of the string charge / discharge power instruction value of each string St1 to Stx is performed so that the string charge / discharge power instruction value gradually changes to the target value over a predetermined period (the string charge / discharge power slope control period in the figure). The string charge / discharge power instruction value of each string St1 to Stx after the storage system charge / discharge power instruction value is updated for the purpose of adjusting the balance of charge / discharge power among the strings St1 to Stx.

[0083] 4 shows the relationship between the charge / discharge power instruction value of the power storage system and the string charge / discharge power instruction values ​​of each string St1 to Stx and time when control for suppressing the response speed of updating the charge / discharge power instruction value of the power storage system (hereinafter referred to as standard slope control) is executed. The standard slope control is executed for the purpose of suppressing abrupt changes in the charge / discharge power of the power storage system when updating the charge / discharge power instruction value of the power storage system.

[0084] 5 shows the relationship between the charge / discharge power instruction value of the power storage system and the string charge / discharge power instruction values ​​of the strings St1 to Stx and time when control for increasing the response speed of updating the charge / discharge power instruction value of the power storage system (hereinafter referred to as shortest slope control) is executed. The shortest slope control is executed for the purpose of achieving a high-speed response when updating the charge / discharge power instruction value of the power storage system.

[0085] 4, when the standard slope control is performed, the charge / discharge power instruction value of the power storage system changes from the current value to the target value over a longer slope control period (e.g., 1.3 to 30 seconds) than when the shortest slope control is performed. During this slope control period, the string charge power instruction value of each of the strings St1 to Stx is updated so as to gradually change from the current value to the target value.

[0086] Here, the power storage system charge / discharge power instruction value is the sum of the string charge / discharge power instruction values ​​of the strings St1 to Stx. Therefore, the string system controller SSC determines the string charge / discharge power instruction values ​​of the strings St1 to Stx so that the string charge / discharge power instruction values ​​of the strings St1 to Stx gradually change from their current values ​​to their target values, and the sum of the string charge / discharge power instruction values ​​of the strings St1 to Stx gradually changes from their current values ​​to their target values.

[0087] Before the start of a slope control period for the charge / discharge power of the power storage system, the string system controller SSC determines a target value for each individual string St1 to Stx for the string charge / discharge power instruction value. The string system controller SSC also calculates a change amount ΔP1 in the string charge / discharge power instruction value for each string St1 to Stx for each predetermined period (e.g., every few seconds). The change amount ΔP1 is a value obtained by equally dividing the difference between the current value and the target value of the string charge / discharge power instruction value for each string St1 to Stx by n, and is determined by the resolution. n is a value obtained by dividing the duration of the slope control period by the predetermined period.

[0088] The string system controller SSC calculates a string charge / discharge power instruction value for each of the strings St1 to Stx at each of the predetermined cycles during the slope control period for the charge / discharge power of the power storage system, and transmits the calculated string charge / discharge power instruction value to each of the string controllers SC1 to SCx by unicast communication. The string charge / discharge power instruction value is a value obtained by adding the change amount ΔP1 to an estimated current value (hereinafter, estimated current value).

[0089] The string system controller SSC transmits the string charge / discharge power instruction value to all of the string controllers SC1 to SCx, and then broadcasts a flag for updating the control of the power converters PCS1 to PCSx (hereinafter referred to as the PCS control update flag) to all of the string controllers SC1 to SCx.

[0090] During the standard slope control, when the storage system charge / discharge power instruction value converges to the target value, the string charge / discharge power instruction value of each of the strings St1 to Stx also converges to the target value. During the subsequent slope control period of the string charge / discharge power, the string charge / discharge power instruction value of each of the strings St1 to Stx gradually changes to balance the string charge / discharge power of each of the strings St1 to Stx.

[0091] When the storage system charge / discharge power instruction value converges to the target value, the string system controller SSC determines the target value of the string charge / discharge power instruction value for each of the strings St1 to Stx for the purpose of balancing the charge / discharge power of each of the strings St1 to Stx. At the same time, the string system controller SSC also calculates a change ΔP2 in the string charge / discharge power instruction value for each of the strings St1 to Stx at a predetermined period (e.g., every few seconds). The method for calculating the change ΔP2 is the same as the method for calculating the change ΔP1 described above.

[0092] The string system controller SSC transmits the string charge / discharge power instruction value of each string St1 to Stx to each string controller SC1 to SCx by unicast communication at each predetermined cycle during the slope control period of the string charge / discharge power. This string charge / discharge power instruction value is a value obtained by adding the above-mentioned change amount ΔP2 to the estimated current value.

[0093] The string system controller SSC transmits the string charge / discharge power instruction value to all the string controllers SC1 to SCx by unicast communication, and then transmits a PCS control update flag to all the string controllers SC1 to SCx by broadcast communication.

[0094] 5, when the shortest slope control is performed, the charge / discharge power instruction value of the power storage system changes from the current value to the target value over a shorter slope control period (e.g., 200 msec to 2 sec) than when the standard slope control is performed. During this slope control period, the string charge power instruction value of each of the strings St1 to Stx is updated so as to change from the current value to the intermediate target value in one cycle.

[0095] After updating the power storage system charge / discharge power instruction value, the power storage system charge / discharge power instruction value is maintained, while the string charge / discharge power instruction value of each of the strings St1 to Stx is updated. The string charge / discharge power instruction value of each of the strings St1 to Stx is updated so as to gradually change from an intermediate target value to a final target value over a slope control period of the string charge / discharge power.

[0096] Here, the power storage system charge / discharge power instruction value is the sum of the string charge / discharge power instruction values ​​of the strings St1 to Stx. Therefore, the string system controller SSC determines the string charge / discharge power instruction values ​​of the strings St1 to Stx so that the string charge / discharge power instruction values ​​of the strings St1 to Stx change from their current values ​​to their intermediate target values ​​in one cycle, and the sum of the string charge / discharge power instruction values ​​of the strings St1 to Stx change from their current values ​​to their target values ​​in one cycle.

[0097] Before the start of a slope control period for the charge / discharge power of the power storage system, the string system controller SSC determines the same intermediate target values ​​for the string charge / discharge power instruction values ​​of all strings St1 to Stx. The string system controller SSC transmits the intermediate target values ​​for the string charge / discharge power instruction values ​​during the slope control period for the charge / discharge power of the power storage system to all string controllers SC1 to SCx by broadcast communication. Thereafter, the string system controller SSC transmits a PCS control update flag to all string controllers SC1 to SCx by broadcast communication.

[0098] Each string controller SC1 to SCx controls each power converter PCS1 to PCSx according to the received intermediate target value of the string charge / discharge power instruction value, updating the charge / discharge power. Here, for strings St1 to Stx whose intermediate target value of the string charge / discharge power instruction value exceeds the charge / discharge power upper limit, the corresponding string controller SC1 to SCx limits the charge / discharge power to less than the intermediate target value and less than or equal to the charge / discharge power upper limit. In this case, the total value of the charge / discharge power of each string St1 to Stx is less than the target value of the charge / discharge power of the power storage system. Therefore, in this case, the string system controller SSC corrects the target value of the charge / discharge power instruction value of the power storage system so that the charge / discharge power of the entire power storage system 1 satisfies the requirements of the power storage system controller PSC. This point will be described in more detail below.

[0099] When the shortest slope control is performed, the string charge / discharge power instruction value of each string St1 to Stx converges to an intermediate target value when the power storage system charge / discharge power instruction value converges to a target value. Because this intermediate target value and the final target value are different, the string charge / discharge power slope control is performed after the power storage system charge / discharge power instruction value converges to the target value. During the string charge / discharge power slope control period, the string charge / discharge power instruction value of each string St1 to Stx gradually changes from the intermediate target value to the final target value for the purpose of balancing the string charge / discharge power of each string St1 to Stx.

[0100] The string system controller SSC determines a final target value for the charge / discharge power instruction value of each of the strings St1 to Stx at the point in time when the storage system charge / discharge power instruction value converges to the target value, for the purpose of balancing the charge / discharge power of each of the strings St1 to Stx. At the same point in time, the string system controller SSC also calculates a change amount ΔP3 in the string charge / discharge power instruction value for each of the strings St1 to Stx at each predetermined period (e.g., every few seconds). The change amount ΔP3 is a value obtained by equally dividing the difference between the intermediate target value and the final target value of the string charge / discharge power instruction value of each of the strings St1 to Stx by n, and is determined by the resolution.

[0101] The string system controller SSC transmits the string charge / discharge power instruction value of each string St1 to Stx to all string controllers SC1 to SCx by unicast communication at the predetermined cycle during the slope control period of the string charge / discharge power. This string charge / discharge power instruction value is a value obtained by adding the change amount ΔP3 to the estimated current value.

[0102] The string system controller SSC transmits the string charge / discharge power instruction value to all the string controllers SC1 to SCx by unicast communication, and then transmits a PCS control update flag to all the string controllers SC1 to SCx by broadcast communication.

[0103] 6 to 12 are tables for explaining a method for determining a power storage system charge / discharge power instruction value and a string charge / discharge power instruction value for each of strings St1 to St63 during a slope control period for the power storage system charge / discharge power or the string charge / discharge power. The tables in Fig. 6 to 12 show a discharge power instruction value for the power storage system 1 as a whole (hereinafter referred to as the power storage system discharge power instruction value) and a discharge power instruction value for each of strings St1 to St63 (hereinafter referred to as the string discharge power instruction value). Below, a method for determining a power storage system discharge power instruction value and a string discharge power instruction value for each of strings St1 to Stx during a slope control period for the discharge power of the power storage system 1 as a whole (hereinafter referred to as the power storage system discharge power) or the discharge power of each of strings St1 to St63 (string discharge power) will be described. The method for determining the charge power instruction value for the entire energy storage system 1 and the charge power instruction value for each string St1 to Stx during the slope control period of the charge power for the entire energy storage system 1 will not be described here, but is the same as the method described below.

[0104] 6 shows the power storage system discharge power instruction value and the string discharge power instruction values ​​of each of the strings St1 to St63 at the start of the standard slope control during the slope control period of the power storage system discharge power. As shown in this table, at the start of the standard slope control during the slope control period of the power storage system discharge power, the string system controller SSC determines the string discharge power instruction values ​​of each of the strings St1 to St63 from "instruction 0" to "instruction n."

[0105] The string system controller SSC calculates the amount of change ΔP1 by equally dividing the difference between the "estimated current value" and the value in the "command n" column by n, and calculates the values ​​in the columns from "command 1" to "command n." The value in the "command 1" column is the value obtained by adding the amount of change ΔP1 to the "estimated current value," the value in the "command 2" column is the value obtained by adding the amount of change ΔP1 to the value in the "command 1" column, the value in the "command n-1" column is the value obtained by adding the amount of change ΔP1 to the value in the "command n-2" column, and the value in the "command n" column is the value in the "command target value" column. The "estimated current value" is a value that the string system controller SSC estimates based on the string discharge instruction value that it has transmitted and the discharge upper limit value of each of the strings St1 to St63.

[0106] The string system controller SSC transmits the value in the "Instruction 0" column as the string discharge power instruction value to each of the string controllers SC1 to SC63 by unicast communication. After that, the string system controller SSC repeatedly executes the following processes (1) to (4) at predetermined intervals.

[0107] (1) The string system controller SSC assigns the values ​​of the columns from "Instruction 1" to "Instruction Target Value" to the column to the left. That is, the string system controller SSC assigns the value of the column "Instruction 1" to the column "Instruction 0", the value of the column "Instruction 2" to the column "Instruction 1", and the value of the "Instruction Target Value" to "Instruction n".

[0108] (2) When the storage system discharge power instruction value is updated, the string system controller SSC changes the “instruction target value” according to the updated storage system discharge power value, and updates the values ​​in the columns “Instruction 1” to “Instruction n” according to the changed “instruction target value.” At this time, the string system controller SSC calculates a change amount ΔP1 by equally dividing the difference between the “estimated current value” and the value in the column “Instruction n” by n, and calculates the values ​​in the columns from “Instruction 1” to “Instruction n.”

[0109] (3) The string system controller SSC transmits the value in the column of "Instruction 0" as the string discharge power instruction value to each of the string controllers SC1 to SC63 by unicast communication.

[0110] (4) The string system controller SSC broadcasts the PCS control update flag to all the string controllers SC1 to SC63.

[0111] The table in Fig. 7 shows the power storage system discharge power command value and the string discharge power command values ​​of each of the strings St1 to St63 at the start of the shortest slope control of the slope control period of the power storage system discharge power. As shown in this table, at the start of the shortest slope control of the slope control period of the power storage system discharge power, the string system controller SSC determines the string discharge power command values ​​of each of the strings St1 to St63 for "Command 0" and "Command 1." The value in the "Command 0" column is the value in the "Assumed Current Value" column, and the value in the "Command 1" column is the value in the "Command Target Value" column. The value in the "Command Target Value" column is the value obtained by dividing the power storage system discharge power command value by the number of strings St1 to St63 that can be discharged.

[0112] The string system controller SSC broadcasts the value in the "Instruction 0" column as the string discharge power instruction value to all string controllers SC1 to SC63. After that, the string system controller SSC executes the following processes (1) to (4).

[0113] (1) The string system controller SSC assigns the values ​​of the columns from "Instruction 1" to "Instruction Target Value" to the column to the left. That is, the string system controller SSC assigns the value of the "Instruction 1" column to the "Instruction 0" column, and assigns the value of the "Instruction Target Value" column to the "Instruction 1" column. If there is an "Instruction 2" column, the value of the "Instruction 2" column is assigned to the "Instruction 1" column, and the value of the "Instruction Target Value" is assigned to the "Instruction 2" column.

[0114] (2) The string system controller SSC broadcasts the value in the "Instruction 0" column as the string discharge power instruction value to all string controllers SC1 to SC63. The string discharge power instruction value is not transmitted to the string controllers SC1 to SC63 corresponding to the strings St1 to St63 that are not performing the discharging operation. Furthermore, if the power storage system discharge power instruction value is updated during execution of the shortest slope control of the power storage system discharge power, the string system controller SSC broadcasts the string discharge power instruction value to the string controllers SC1 to SC63 based on the power storage system discharge power instruction value before the update, and then executes processing according to the updated power storage system discharge power instruction value. Here, the string system controller SSC may suspend processing according to the power storage system discharge power instruction value before the update and execute processing according to the updated power storage system discharge power instruction value.

[0115] (3) The string system controller SSC broadcasts the PCS control update flag to all string controllers SC1 to SC63. Note that the PCS control update flag is not transmitted to the string controllers SC1 to SC63 corresponding to the strings St1 to St63 that do not perform the discharge operation.

[0116] (4) The string system controller SSC executes the standard slope control of the string discharge power shown in the table of FIG. 8 to maintain the discharge power of the power storage system while adjusting the balance of the string discharge power of each of the strings St1 to St63.

[0117] 8 shows the storage system discharge power instruction value and the string discharge power instruction value of each of the strings St1 to St63 at the start of the standard slope control of the string discharge power. As shown in this table, at the start of the standard slope control of the string discharge power slope control period, the string system controller SSC determines the string discharge power instruction value of each of the strings St1 to St63 from "instruction 0" to "instruction n."

[0118] The string system controller SSC calculates the amount of change ΔP3 by dividing the difference between the "estimated current value" and the value in the "command n" column by n equal parts, and calculates the values ​​in the columns from "command 1" to "command n." The value in the "command 1" column is the value obtained by adding the amount of change ΔP3 to the "estimated current value," the value in the "command 2" column is the value obtained by adding the amount of change ΔP3 to the value in the "command 1" column, the value in the "command n-1" column is the value obtained by adding the amount of change ΔP3 to the value in the "command n-2" column, and the value in the "command n" column is the value in the "command target value" column. The "estimated current value" is a value that the string system controller SSC estimates based on the string discharge command value it transmitted (the value in the "command target value" column in the table of FIG. 7) and the string discharge upper limit value of each of the strings St1 to St63.

[0119] The string system controller SSC transmits the value in the "Instruction 0" column as the string discharge power instruction value to each of the string controllers SC1 to SC63 by unicast communication. After that, the string system controller SSC repeatedly executes the following processes (1) to (4) at predetermined intervals.

[0120] (1) The string system controller SSC assigns the values ​​of the columns from "Instruction 1" to "Instruction Target Value" to the column to the left. That is, the string system controller SSC assigns the value of the column "Instruction 1" to the column "Instruction 0", the value of the column "Instruction 2" to the column "Instruction 1", and the value of the "Instruction Target Value" to "Instruction n".

[0121] (2) When the storage system discharge power instruction value is updated, the string system controller SSC shifts from the standard slope control of the string discharge power to the shortest slope control of the storage system discharge power.

[0122] (3) The string system controller SSC transmits the value in the column of "Instruction 0" as the string discharge power instruction value to each of the string controllers SC1 to SC63 by unicast communication.

[0123] (4) The string system controller SSC broadcasts the PCS control update flag to all the string controllers SC1 to SC63.

[0124] 9 to 11 show the power storage system discharge power instruction value and the string discharge power instruction values ​​of each of the strings St1 to St63 at the start of the shortest slope control of the slope control period of the power storage system discharge power. Here, in the example shown in the tables of Fig. 9 to 11, there are strings St2 and St3 whose "discharge power upper limit value" is lower than the "instruction target value."

[0125] As shown in the table of Fig. 9, at the start of the shortest slope control of the slope control period of the power storage system discharge power, the string system controller SSC determines the string discharge power command values ​​of each of the strings St1 to St63 for "Command 0" and "Command 1." The value in the "Command 0" column is the value in the "Expected Current Value" column, and the value in the "Command 1" column is the value in the "Command Target Value" column. The value in the "Command Target Value" column is the value obtained by dividing the power storage system discharge power command value by the number of strings St1 to St63 that can be discharged.

[0126] The string system controller SSC compares the value in the "Command Target Value" column with the value in the "Command 1" column and the value in the "Discharge Power Upper Limit Value" column, and calculates the shortfall or excess of the string discharge power that can be output by each of the strings St1 to St63 relative to the value in the "Command Target Value" column. Here, if the value in the "Command Target Value" column is smaller than the value in the "Discharge Power Upper Limit Value" column ("Command Target Value" < "Discharge Power Upper Limit Value"), the excess of the string discharge power that can be output by each of the strings St1 to St63 is 0 or greater ("Command 1" - "Command Target Value" ≥ 0). On the other hand, if the value in the "Command Target Value" column is equal to or greater than the value in the "Discharge Power Upper Limit Value" column ("Command Target Value" ≥ "Discharge Power Upper Limit Value"), the shortfall of the string discharge power that can be output by each of the strings St1 to St63 is 0 or greater ("Command Target Value" - "Command 1" ≥ 0).

[0127] As shown in the tables of FIGS. 10 and 11 , the string system controller SSC corrects the power storage system discharge power instruction value and corrects the value in the “Instruction 1” column of the string discharge power instruction value for each of the strings St1 to St63 in accordance with the correction of the power storage system discharge power instruction value. That is, the string system controller SSC corrects the power storage system discharge power instruction value so that the total value of the shortage and excess of the string discharge power for each of the strings St1 to St63 (−1300 in FIG. 9 , −120 in FIG. 10 ) approaches zero. The string system controller SSC also calculates the value in the “Instruction 1” column by dividing the corrected power storage system discharge power instruction value by the number of dischargeable strings St1 to St63 and assigns the calculated value to the “Instruction 1” column. The above process is repeated a necessary number of times until the total value of the shortage and excess of the string discharge power for each of the strings St1 to St63 becomes zero.

[0128] The string system controller SSC broadcasts the value in the "Instruction 0" column shown in the table of Fig. 11 as the string discharge power instruction value to all string controllers SC1 to SC63. After that, the string system controller SSC executes the following processes (1) to (4).

[0129] (1) The string system controller SSC assigns the values ​​of the columns from "Instruction 1" to "Instruction Target Value" to the column to the left. That is, the string system controller SSC assigns the value of the column "Instruction 1" to the column "Instruction 0". If a column "Instruction 2" exists, the value of the column "Instruction 2" is assigned to the column "Instruction 1", and the value of the "Instruction Target Value" is assigned to the column "Instruction 2".

[0130] (2) The string system controller SSC broadcasts the value in the “Instruction 0” column as the string discharge power instruction value to all string controllers SC1 to SC63. Note that the string discharge power instruction value is not transmitted to the string controllers SC1 to SC63 corresponding to the strings St1 to St63 that are not performing the discharge operation.

[0131] (3) The string system controller SSC broadcasts the PCS control update flag to all string controllers SC1 to SC63. The PCS control update flag is not transmitted to the string controllers SC1 to SC63 corresponding to the strings St1 to St63 that are not performing the discharge operation. For strings St2 and St3 whose discharge power upper limit is lower than the command target value, the corresponding string controllers SC2 and SC3 control the power converters PCS2 and PCS3 so that the string discharge power output is equal to or lower than the discharge power upper limit.

[0132] (4) The string system controller SSC executes the standard slope control of the string discharge power shown in the table of FIG.

[0133] The table in FIG. 12 shows the power storage system discharge power instruction value and the string discharge power instruction value of each of the strings St1 to St63 at the start of the standard slope control of the string discharge power.

[0134] As shown in this table, at the start of standard slope control during the string discharge power slope control period, the string system controller SSC determines string discharge power instruction values ​​for each of strings St1 to St63 from "instruction 0" to "instruction n."

[0135] The string system controller SSC calculates the amount of change ΔP3 by dividing the difference between the "estimated current value" and the value in the "command n" column by n equal parts, and calculates the values ​​in the columns from "command 1" to "command n." The value in the "command 1" column is the value obtained by adding the amount of change ΔP3 to the "estimated current value," the value in the "command 2" column is the value obtained by adding the amount of change ΔP3 to the value in the "command 1" column, the value in the "command n-1" column is the value obtained by adding the amount of change ΔP3 to the value in the "command n-2" column, and the value in the "command n" column is the value in the "command target value" column. Furthermore, the "estimated current value" is the lower of the value in the "command 1" column and the value in the "discharge power upper limit" column shown in the table of FIG. 11.

[0136] The string system controller SSC transmits the value in the column of "Instruction 0" as the string discharge power instruction value to each of the string controllers SC1 to SC63 by unicast communication. After that, the string system controller SSC repeatedly executes the following processes (1) to (4) at predetermined intervals while maintaining the discharge power of the power storage system.

[0137] (1) The string system controller SSC assigns the values ​​of the columns from "Instruction 1" to "Instruction Target Value" to the column to the left. That is, the string system controller SSC assigns the value of the column "Instruction 1" to the column "Instruction 0", the value of the column "Instruction 2" to the column "Instruction 1", and the value of the "Instruction Target Value" to "Instruction n".

[0138] (2) When the storage system discharge power instruction value is updated, the string system controller SSC shifts from the standard slope control of the string discharge power to the shortest slope control of the storage system discharge power.

[0139] (3) The string system controller SSC transmits the value in the column of "Instruction 0" as the string discharge power instruction value to each of the string controllers SC1 to SC63 by unicast communication.

[0140] (4) The string system controller SSC broadcasts the PCS control update flag to all the string controllers SC1 to SC63.

[0141] As described above, the battery control device 2 according to this embodiment includes a plurality of string controllers SC1 to SCx, each provided for each of the strings St1 to Stx, a power storage system controller PSC, and a string system controller SSC that communicates with the plurality of string controllers SC1 to SCx. Each of the string controllers SC1 to SCx controls the string charge / discharge power (second charge / discharge power instruction value) of the corresponding string St1 to Stx. The string system controller SSC receives a power storage system charge / discharge power instruction value (first charge / discharge power instruction value) from the power storage system controller PSC, calculates a string charge / discharge power instruction value for each of the strings St1 to Stx in accordance with the received power storage system charge / discharge power instruction value, and transmits the calculated string charge / discharge power instruction value to the corresponding string controller SC1 to SCx.

[0142] Here, the string system controller SSC changes the charge / discharge power of the power storage system from a current value to a target value by selectively executing either standard slope control or shortest slope control during a slope control period of the charge / discharge power of the power storage system. Then, the string system controller SSC adjusts the string charge / discharge power of the multiple strings St1 to Stx by executing standard slope control during a slope control period of the string charge / discharge power after executing the standard slope control or shortest slope control.

[0143] In standard slope control during the slope control period of the power storage system charge / discharge power, the string system controller SSC calculates a string charge / discharge power instruction value for each predetermined period individually for each of the string controllers SC1 to SCx in accordance with the power storage system charge / discharge power instruction value received from the power storage system controller PSC. Then, the string system controller SSC transmits the calculated string charge / discharge power instruction value individually to each of the string controllers SC1 to SCx in each predetermined period. This makes it possible to gradually change the power storage system charge / discharge power over an arbitrary period of time when updating the power storage system charge / discharge power instruction value, thereby suppressing abrupt changes in the power storage system charge / discharge power.

[0144] Furthermore, during the shortest slope control of the slope control period for the charge / discharge power of the power storage system, the string system controller SSC calculates a string charge / discharge power instruction value common to the multiple string controllers SC1 to SCx in accordance with the power storage system charge / discharge power instruction value received from the power storage system controller PSC.The string system controller SSC then simultaneously transmits the calculated common string charge / discharge power instruction value to the multiple string controllers SC1 to SCx.This improves responsiveness when updating the power storage system charge / discharge power instruction value.

[0145] Furthermore, in the standard slope control during the slope control period of the charge / discharge power of the power storage system, the string system controller SSC individually transmits the string charge / discharge power instruction value calculated for each of the string controllers SC1 to SCx to each of the string controllers SC1 to SCx at predetermined intervals by unicast communication. This makes it possible to converge the string charge / discharge power of each of the strings St1 to Stx to the target value at the completion of the slope control of the charge / discharge power of the power storage system.

[0146] In contrast, in the shortest slope control of the slope control period of the charge / discharge power of the power storage system, the string system controller SSC simultaneously transmits a string charge / discharge power instruction value common to the multiple string controllers SC1 to SCx to the multiple string controllers SC1 to SCx by broadcast communication, which enables the slope control of the charge / discharge power of the power storage system to be completed in a shorter time than the standard slope control.

[0147] Furthermore, when the string system controller SSC receives an updated power storage system charge / discharge power instruction value from the power storage system controller PSC while executing standard slope control of the string charge / discharge power after executing shortest slope control of the power storage system charge / discharge power, the string system controller SSC shifts from standard slope control of the string charge / discharge power to shortest slope control of the power storage system charge / discharge power, thereby improving responsiveness to updates of the power storage system charge / discharge power.

[0148] Furthermore, when executing the shortest slope control of the power storage system charge / discharge power, the string system controller SSC calculates the difference between the upper limit value of the string charge / discharge power and the string charge / discharge power instruction value for each of the strings St1 to Stx, and corrects the power storage system charge / discharge power instruction value so that the total value of the differences for the multiple strings St1 to Stx is reduced. The string system controller SSC then calculates a string charge / discharge power instruction value common to the multiple string controllers SC1 to SCx based on the corrected power storage system charge / discharge power instruction value. The string system controller SSC then simultaneously transmits the calculated common string charge / discharge power instruction value to the multiple string controllers SC1 to SCx. This makes it possible to keep the string charge / discharge power of the string St1 to Stx below the upper limit value and bring the actual power storage system charge / discharge power closer to the power storage system charge / discharge power instruction value received from the power storage system controller PSC. It is not essential to correct the power storage system charge / discharge power instruction value so as to reduce the total value of the differences among the multiple strings St1 to Stx, but the string charge / discharge power instruction value may be corrected so as to reduce the total value of the differences among the multiple strings St1 to Stx. In this case, the string charge / discharge power instruction value is a common value among the multiple string controllers SC1 to SCx.

[0149] Here, the charge / discharge power upper limit is an estimated value of the charge / discharge power that the strings St1 to Stx can charge / discharge, whereas the charge / discharge power that the strings St1 to Stx can actually charge / discharge may be equal to or greater than the estimated value. In such a case, if a string charge / discharge power instruction value exceeding the estimated charge / discharge power upper limit is transmitted from the string system controller SSC and the strings St1 to Stx perform charging / discharging in accordance with the transmitted string charge / discharge power instruction value, an error occurs between the charge / discharge power of the power storage system 1 and the charge / discharge power instruction value of the power storage system. Therefore, when performing the shortest slope control of the charge / discharge power of the power storage system, the string controllers SC1 to SCx control the charge / discharge power to be equal to or less than the charge / discharge power upper limit of each of the strings St1 to Stx in accordance with the string charge / discharge power instruction value transmitted from the string system controller SSC. This reduces the error between the charge / discharge power of the power storage system 1 and the charge / discharge power instruction value of the power storage system.

[0150] Furthermore, in the standard slope control of the charge / discharge power of the power storage system or the string system charge / discharge power, the string system controller SSC sets the string charge / discharge power instruction value for each predetermined period so that it gradually changes from the current value to the target value. This makes it possible to gradually change the charge / discharge power of the power storage system over any amount of time when updating the charge / discharge power instruction value of the power storage system, thereby suppressing abrupt changes in the charge / discharge power of the power storage system.

[0151] Furthermore, the string system controller SSC transmits string charge / discharge power instruction values ​​to the plurality of string controllers SC1 to SCx in standard slope control or shortest slope control, and then simultaneously transmits instructions to execute control of the power converters PCS1 to PCSx to the plurality of string controllers SC1 to SCx by broadcast communication. This shortens the communication time for the control instructions of the power converters PCS1 to PCSx and improves responsiveness to updates of the charge / discharge power of the power storage system.

[0152] The present invention has been described above based on the above-mentioned embodiment, but the present invention is not limited to the above-mentioned embodiment, and modifications may be made within the scope of the spirit of the present invention, and publicly known or well-known technologies may be combined as appropriate.

[0153] For example, in the above-described embodiment, the string system controller SSC transmits string charge / discharge power instruction values ​​to the string controllers SC1 to SCx. However, the power storage system controller PSC and the string system controller SSC may be integrated, and the integrated controller may transmit string charge / discharge power instruction values ​​to the string controllers SC1 to SCx. Alternatively, one of the multiple string controllers SC1 to SCx may be a master controller, and the others may be slave controllers, and the master controller may transmit string charge / discharge power instruction values ​​to the slave controllers.

[0154] Although various embodiments have been described above, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any manner as long as they do not deviate from the spirit of the invention.

[0155] This application is based on a Japanese patent application (Patent Application No. 2023-120934) filed on July 25, 2023, the contents of which are incorporated herein by reference.

[0156] 1: Energy storage system 2: Battery control device PCS1: Power converter PCS2: Power converter PCS3: Power converter PCSx: Power converter PSC: Energy storage system controller (higher control unit) SC1: String controller (first control unit) SC2: String controller (first control unit) SC3: String controller (first control unit) SC63: String controller (first control unit) SCx: String controller (first control unit) SSC: String system controller (second control unit) St1: String (energy storage string) St2: String (energy storage string) St3: String (energy storage string) St4: String (energy storage string) St5: String (energy storage string) St63: String (energy storage string) Stx: ​​String (energy storage string)

Claims

1. A battery control device for controlling a power storage system having a plurality of power storage strings connected in parallel, comprising: a plurality of first control units provided for each of the power storage strings and controlling charge / discharge power of the corresponding power storage string; and a second control unit configured to receive a first charge / discharge power instruction value which is an instruction value for charge / discharge power of the entire power storage system from a higher-level control unit, calculate a second charge / discharge power instruction value which is an instruction value for charge / discharge power of each of the power storage strings in accordance with the received first charge / discharge power instruction value, and transmit the calculated second charge / discharge power instruction value to the corresponding first control unit, wherein the second control unit is configured to: calculate the second charge / discharge power instruction value for each predetermined period individually for each of the first control units in accordance with the first charge / discharge power instruction value received from the higher-level control unit, and transmit the calculated second charge / discharge power instruction value individually to the first control unit in each predetermined period; a second control in which the second charge / discharge power instruction value common to the plurality of first control units is calculated in accordance with the first charge / discharge power instruction value received from the higher-level control unit, and the calculated common second charge / discharge power instruction value is transmitted simultaneously to the plurality of first control units, thereby changing the charge / discharge power of the entire power storage system from a current value to a target value; and a third control in which, after execution of the first control or the second control, the second charge / discharge power instruction value is calculated individually for each of the first control units, and the calculated second charge / discharge power instruction value is transmitted individually to the first control unit, thereby adjusting the charge / discharge power of the plurality of power storage strings.

2. The battery control device of claim 1, wherein the second control unit transmits the calculated second charge / discharge power instruction value to the first control unit at each of the predetermined periods via unicast communication when the first control and the third control are being executed, and transmits the calculated common second charge / discharge power instruction value simultaneously to the multiple first control units via broadcast communication when the second control is being executed.

3. A battery control device as described in claim 1 or 2, wherein the second control unit executes the second control when it receives the updated first charge / discharge power instruction value from the higher-level control unit during execution of the third control after execution of the second control.

4. A battery control device as described in claim 1 or 2, wherein, when executing the second control, the second control unit calculates the difference between the charge / discharge power upper limit value and the second charge / discharge power instruction value for each of the power storage strings, calculates the second charge / discharge power instruction value common to the multiple first control units that reduces the total value of the differences for the multiple power storage strings, and transmits the calculated common second charge / discharge power instruction value to the multiple first control units simultaneously.

5. A battery control device as described in claim 4, wherein the first control unit, when executing the second control, controls the charging / discharging power to be below the charging / discharging power upper limit value for each storage string in accordance with the second charging / discharging power instruction value transmitted from the second control unit.

6. A battery control device according to claim 1 or 2, wherein the second charge / discharge power instruction value calculated in the first control for each predetermined period gradually changes from a current value to a target value.

7. The battery control device according to claim 1 or claim 2, wherein the energy storage system includes a plurality of power converters provided for each of the energy storage strings and controlled by the first control unit to convert the charge / discharge power of the energy storage strings, and the second control unit transmits the second charge / discharge power instruction value to the plurality of first control units in the first control, the second control, or the third control, and then transmits an instruction to execute control of the power converters to the plurality of first control units simultaneously by broadcast communication.

8. A power storage system comprising: a plurality of power storage strings connected in parallel; and a battery control device that controls the charge / discharge power of the plurality of power storage strings, wherein the battery control device comprises: a plurality of first control units provided for each of the power storage strings and controlling the charge / discharge power of the corresponding power storage string; and a second control unit that receives a first charge / discharge power instruction value that is an instruction value for the charge / discharge power of the entire power storage system from a higher-level control unit, calculates a second charge / discharge power instruction value that is an instruction value for the charge / discharge power of each of the power storage strings in accordance with the received first charge / discharge power instruction value, and transmits the calculated second charge / discharge power instruction value to the corresponding first control unit; and the second control unit comprises: a first control that calculates the second charge / discharge power instruction value for each predetermined period individually for each of the first control units in accordance with the first charge / discharge power instruction value received from the higher-level control unit, and transmits the calculated second charge / discharge power instruction value individually to the first control unit in accordance with the first charge / discharge power instruction value received from the higher-level control unit; a second control in which the second control calculates the second charge / discharge power instruction value common to the plurality of first control units according to the first charge / discharge power instruction value received from the higher-level control unit, and transmits the calculated common second charge / discharge power instruction value to the plurality of first control units simultaneously, thereby changing the charge / discharge power of the entire energy storage system from a current value to a target value; and after execution of the first control or the second control, the third control calculates the second charge / discharge power instruction value individually for each of the first control units, and transmits the calculated second charge / discharge power instruction value individually to the first control unit, thereby adjusting the charge / discharge power of the plurality of energy storage strings.

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