Storage battery control device and electricity storage system

Abstract

According to the present invention, an MCU (100) of a module interface (MI / F) receives a cell voltage detection signal from a cell monitoring unit (CMU) and transmits a charge-limiting signal for limiting the charge power of a string to an MCU (101) of a power converter (PCS) if the cell voltage is equal to or higher than an upper threshold. The MCU (101) controls the power converter (PCS) to make the charge power of the string approach a designated charge power value while a control signal is received from a string controller (SC) but the charge-limiting signal is not received from the MCU (100), and controls the power converter to make the charge power of the string approach the designated charge power value while the control signal is received from the string controller (SC) and the charge-limiting signal is received from the MCU (100).

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] Known energy storage systems including a string of multiple storage battery modules connected in series include a system equipped with a bypass mechanism that bypasses each storage battery module (see, for example, Patent Documents 1 and 2). In the energy storage systems described in Patent Documents 1 and 2, a fully charged or fully discharged storage battery module can be bypassed by the bypass mechanism, allowing charging and discharging to continue. This allows for the mixing of storage battery modules with different charge / discharge capacities due to differences in their state of deterioration or types.

[0003] Japanese Patent Publication No. 2013-31247 Japanese Patent Publication No. 2013-31249

[0004] For brand new storage battery modules with minimal variations in performance at the time of manufacture, or storage battery modules that have reached the same state of degradation due to being used in the same environment and under the same conditions, monitoring the total voltage and current of the string and controlling the charge and discharge of the string can keep the voltage of all storage battery cells in the string within an appropriate range. However, storage battery modules with variations in performance at the time of manufacture, or storage battery modules that have differing states of degradation due to not being used in the same environment or under the same conditions, often have variations in the performance of the storage battery cells within the storage battery module. When storage battery modules with variations in cell performance are mixed, simply monitoring the total voltage and current of the string and controlling the charge and discharge of the string makes it difficult to control the voltage of all storage battery cells so that they do not exceed an upper limit or fall below a lower limit.

[0005] Therefore, in a power storage system equipped with strings containing a mixture of storage battery modules with varying storage battery cell performance, it is necessary to monitor the voltage of the storage battery cells (hereinafter referred to as cell voltage) to control the charging and discharging of the string. However, if cell voltage information is transmitted from the cell voltage monitoring unit via the interface of the storage battery module to a controller that controls the charging and discharging of the string, and the controller determines whether the cell voltage is between an upper and lower limit, and transmits a control signal based on the determination result to the power converter of the string, the communication process will have a large delay, and during that time, there is a possibility that the cell voltage will exceed the upper limit or fall below the lower limit.

[0006] In view of the above circumstances, the present invention aims to provide a battery control device and a power storage system that can keep the voltage of the battery cells in a battery module within an appropriate range regardless of whether there is variation in the performance of the battery cells in the string.

[0007] The battery control device of the present invention is a battery control device for controlling a power storage system including a string having a plurality of storage battery modules connected in series and a power converter that converts charging and discharging power of the string, wherein the storage battery module includes a plurality of storage battery cells connected in series and a cell voltage detection unit that detects the voltage of the storage battery cells, and the battery control device includes a plurality of module control units that are provided corresponding to the storage battery modules and control the storage battery modules, a power converter control unit that controls the power converter, and a control signal that is provided corresponding to the string and communicates with the plurality of module control units, the power converter control unit, and a higher-level control unit, and is used to control the power converter so that the charging power of the string approaches a charging power instruction value received from the higher-level control unit. and a string control unit that transmits a detection signal of the voltage of the storage battery cell from the cell voltage detection unit to the power converter control unit, wherein the module control unit receives a detection signal of the voltage of the storage battery cell from the cell voltage detection unit, and, when the voltage of the storage battery cell is equal to or higher than an upper threshold, transmits a charge suppression signal to the power converter control unit to suppress charging power of the string, and the power converter control unit controls the power converter to bring the charging power of the string closer to the charging power instruction value while receiving the control signal from the string control unit and the charge suppression signal from the module control unit.

[0008] The battery control device of the present invention is a battery control device for controlling a power storage system including a string having a plurality of storage battery modules connected in series and a power converter that converts charge / discharge power of the string, wherein the storage battery module includes a plurality of storage battery cells connected in series and a cell voltage detection unit that detects the voltage of the storage battery cells, and the battery control device includes a plurality of module control units that are provided corresponding to the storage battery modules and control the storage battery modules, a power converter control unit that controls the power converter, and a control signal that is provided corresponding to the string and communicates with the plurality of module control units, the power converter control unit, and a higher-level control unit, and is used to control the power converter so that the discharge power of the string approaches a discharge power instruction value received from the higher-level control unit. and a string control unit that transmits a detection signal of the voltage of the storage battery cell from the cell voltage detection unit to the power converter control unit, wherein the module control unit receives a detection signal of the voltage of the storage battery cell from the cell voltage detection unit, and, when the voltage of the storage battery cell is equal to or lower than a lower threshold, transmits a discharge suppression signal to the power converter control unit to suppress the discharge power of the string, and while the power converter control unit receives the control signal from the string control unit but does not receive the discharge suppression signal from the module control unit, the power converter control unit controls the power converter to bring the discharge power of the string closer to the discharge power instruction value, and while receiving the control signal from the string control unit and the discharge suppression signal from the module control unit, controls the power converter to suppress the discharge power of the string.

[0009] The energy storage system of the present invention comprises a string having a plurality of storage battery modules connected in series, and a power converter that converts the charging and discharging power of the string, and the storage battery module comprises a plurality of storage battery cells connected in series and a cell voltage detection unit that detects the voltage of the storage battery cells, and is equipped with the energy storage control device described in claim 1 or 2.

[0010] According to the present invention, the voltage of the storage battery cells in a storage battery module can be kept within an appropriate range regardless of whether there is variation in the performance of the storage battery cells in the string.

[0011] 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 graph illustrating updating of a power storage system charge / discharge power instruction value and a string charge / discharge power instruction value of each string. FIG. 4 is a graph illustrating updating of a power storage system charge / discharge power instruction value and a string charge / discharge power instruction value of each string. FIG. 5 is a circuit diagram showing a communication circuit for communication between the string controller, power converter, and module interface shown in FIGS. 1 and 2. FIG. 6 is a chart illustrating a communication method of a battery control device according to a comparative example. FIG. 7 is a chart illustrating a communication method of the battery control device shown in FIGS. 1 and 2. FIG. 8 is a graph showing changes in charge / discharge power instruction value and actual charge / discharge power, and a timing chart showing the ON / OFF timing of a cell upper limit voltage warning signal and a cell lower limit voltage warning signal. FIG. 9 is a flowchart illustrating charge control of the battery control device shown in FIGS. 1 and 2. FIG. 10 is a flowchart illustrating discharge control of the battery control device shown in FIGS. 1 and 2.

[0012] 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.

[0013] 1 is a circuit diagram showing the circuit configuration of a power storage system 1 including a battery control device 2 according to one embodiment of the present invention. The power storage system 1 shown in this diagram is a stationary power source and includes a string system 10 and a power storage system controller PSC.

[0014] 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.

[0015] The string system 10 includes multiple strings St1 to Stx, a string bus 6, a string system controller SSC, and multiple string controllers SC1 to SCx. The string system controller SSC and the string controllers SC1 to SCx will be described later. Note that when it is not necessary to distinguish between the strings St1 to Stx, the strings St1 to Stx will be referred to as string St. Furthermore, when it is not necessary to distinguish between the string controllers SC1 to SCx, the string controllers SC1 to SCx will be referred to as string controllers SC.

[0016] The strings St are connected in parallel to a string bus 6. The string bus 6 is connected to an external system (not shown). The strings St include power converters PCS1 to PCSx, a plurality of modules M1 to Mn, and a plurality of module interfaces M Ｉ／Ｆ 1 to M Ｉ／Ｆ n. Module interface M Ｉ／Ｆ 1 to M Ｉ／Ｆ n will be described later. When it is not necessary to distinguish between the power converters PCS1 to PCSx, the power converters PCS1 to PCSx will be referred to as power converters PCS. When it is not necessary to distinguish between the modules M1 to Mn, the modules M1 to Mn will be referred to as modules M. Furthermore, the module interface M Ｉ／Ｆ 1 to M Ｉ／Ｆ When there is no need to distinguish between the module interfaces M Ｉ／Ｆ 1 to M Ｉ／Ｆ n to the module interface M Ｉ／Ｆ It is written as follows.

[0017] The module M includes a storage battery consisting of multiple storage battery cells C connected in series, a bypass mechanism B, and cell monitoring units CMU1 to CMUn. In a string St, multiple storage batteries are connected in series, and each storage battery is provided with a bypass mechanism B. The string St also includes a current sensor 11 that measures the total current of the string St, a voltage sensor (not shown) that measures the total voltage of the string St (hereinafter referred to as the string total voltage), and the like.

[0018] The storage battery cells C are secondary battery cells such as lithium ion batteries or lithium ion capacitors, and are charged by receiving power from an external system via the power converter PCS, and the charged power is discharged via the power converters PCS1 to PCSx to supply power to the external system. Although not particularly limited, the storage batteries of the module M in this embodiment are regenerated second-hand storage batteries, and there are differences in the degree of deterioration and the performance of the storage battery cells.

[0019] The bypass mechanism B includes a bypass line BL and switches S1 and S2. The bypass line BL is a power line that bypasses the storage battery. 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 the storage battery and one end of the bypass line BL. This switch S2 is, for example, a mechanical switch, a semiconductor switch, or a relay.

[0020] The storage battery of the starting module M1 and the storage battery of the terminal module Mn are connected to an external system via the power converter PCS and the string bus 6. When the switch S1 is turned OFF and the switch S2 is turned ON in all bypass mechanisms B, all the storage batteries of the string St 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 mechanisms B, the storage battery corresponding to that bypass mechanism B is bypassed.

[0021] The power converter PCS is a bidirectional converter and is connected to the string bus 6. The power converter PCS is also connected to the positive terminal of the storage battery in the starting module M1 and the negative terminal of the storage battery in the terminal module Mn.

[0022] When charging the strings St, the power converter PCS converts the voltage input from the string bus 6 and outputs it to the storage batteries of the multiple modules M. Here, the voltage on the string St side changes depending on the bypass state of the multiple modules M (the number of modules M whose storage batteries are bypassed) and the charging state of the storage batteries of the multiple modules M. Therefore, when charging the strings St, the power converter PCS converts the voltage input from the string bus 6 to a voltage on the string St side and outputs it to the storage batteries of the multiple modules M.

[0023] When a string St is discharged, the power converter PCS converts the voltage input from the storage batteries of the multiple modules M and outputs the converted voltage to the string bus 6. Here, the input voltage of the power converter PCS during discharge varies depending on the bypass state of the multiple modules M and the charge state of the storage batteries of the multiple modules M. This causes variations in the input voltage of the power converter PCS between the strings St during discharge. Therefore, when a string St is discharged, the power converter PCS converts the input voltage to a voltage that matches that of the other strings St and outputs the converted voltage to the string bus 6. Note that when the current flowing through the string bus 6 is AC, the power converter PCS is equipped with synchronization means for tracking changes in instantaneous value.

[0024] The cell monitoring units CMU1 to CMUn are connected between the positive and negative terminals of each storage battery cell C, detect the voltage between the terminals (cell voltage) of each storage battery cell C, and transmit the detection signal to the module interface M. Ｉ／Ｆ The cell monitoring units CMU1 to CMUn also have a cell balancing function and equalize the cell voltages of the module M. When it is not necessary to distinguish between the cell monitoring units CMU1 to CMUn and explain them separately, the cell monitoring units CMU1 to CMUn will be referred to as cell monitoring units CMU.

[0025] Module Interface M Ｉ／Ｆ has a function of controlling the switches S1 and S2 of the bypass mechanism B and a function of communicating with the string controller SC and the power converter PCS. These functions will be described later.

[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 storage system controller PSC, a string system controller SSC, a plurality of string controllers SC, and a plurality of module interfaces M. Ｉ／Ｆ The system includes a plurality of cell monitoring units CMUs and a plurality of MCUs (Micro Control Units) 101. A cell monitoring unit CMU is provided for each module M, and an MCU 101 is provided for each power converter PCS.

[0027] A storage system controller PSC, a string system controller SSC, a string controller SC, and a module interface M Ｉ／Ｆ are provided for each layer. The power storage system controller PSC corresponds to the layer of the top power storage system 1. The string system controller SSC corresponds to the layer of the string system 10 that is next to the layer of the power storage system 1. The string controller SC corresponds to the layer of the string St that is next to the layer of the string system 10. The module interface M Ｉ／Ｆ corresponds to the layer of module M next to the layer of string St.

[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 (e.g., a container, etc.) of the power storage system 1, a fire extinguishing equipment, etc. (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 sends an abnormality notification to the display input device. The power storage system controller PSC also monitors the operating status of the fire extinguishing equipment.

[0030] The storage system controller PSC receives information about the state of the string St (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 transmits them to the upper server 7 and the display input device.

[0031] The state of the string St may include an operating state such as charging, discharging, resting, maintenance, etc., a string current, a total string voltage, an SOC (State of Charge) of the string St (hereinafter referred to as string SOC), an SOH (State of Health) of the string St (hereinafter referred to as string SOH), and a limit value of the charge / discharge power (or charge / discharge current) of the string St (hereinafter referred to as string charge / discharge power limit value).

[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 to a display input device as needed. Note that in this embodiment where there is a single string system 10, the string system SOC is equal to the power storage system SOC, and the string system SOH is equal to the power storage system SOH.

[0034] The power storage system controller PSC transmits information required for the processing of the upper server 7 to the upper server 7. Examples of the information required for the processing of 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 a charge / discharge instruction corresponding to the power storage system 1 based on the "information required for the processing of the upper server 7" received from the power storage system controller PSC, and transmits the instruction to the power storage system controller PSC. The charge / discharge instruction may 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, an operation method such as independent operation / grid-connected operation, and the like.

[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 auxiliaries 3, the string system auxiliaries 4, and the auxiliaries of the string St, such as the power converter PCS. By forcibly operating the power storage system auxiliaries 3, the string system auxiliaries 4, and the auxiliaries of the string St, it becomes possible to check the operation of the power storage system auxiliaries 3, the string system auxiliaries 4, and the auxiliaries of the string St.

[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 SC, and controls and manages the string system auxiliaries 4. Examples of the string system auxiliaries 4 include a temperature sensor that detects the ambient temperature, a cooling device in the string system 10, a circuit breaker for the string bus 6, a current sensor that detects the string bus current, and a voltage sensor that detects the string bus voltage (all of which are not shown).

[0040] The string system controller SSC receives string status information from multiple string controllers SC. The status of the string St 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 string state information received from the multiple string controllers SC. 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. Note that the state of the string system 10 may be estimated by the power storage system controller PSC.

[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 are outside the threshold range, the string system controller SSC determines whether there is an abnormality in the string system 10 and 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, among the information received from the multiple string controllers SC 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 for individually controlling 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 St, 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. Note that the charge / discharge instructions for the string system 10 in the charge / discharge mode are transmitted from the power storage system controller PSC to the string controller SC via the string system controller SSC. Individual control instructions for the string system 10 in the maintenance mode include instructions to individually control the power converter PCS, the switches S1 and S2 of the bypass mechanism B, and the string system accessories 4. State estimation instructions for the string system 10 in the state estimation mode include instructions to execute predetermined control necessary to estimate the state of the string St.

[0045] The string system controller SSC receives an instruction 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 the string St, whether to grant permission for a bypass request from the string controller SC, and a string charge / discharge power instruction value to be assigned to the string St. Examples of the operating mode of the string St include a charge / discharge mode, a state estimation mode, and a maintenance / stop mode.

[0046] The string controller SC is connected to a string system controller SSC and a plurality of module interfaces M Ｉ／Ｆ The power converter PCS communicates with the power converter PCS to control and manage the auxiliary devices of the string St. In addition to the power converter PCS, the auxiliary devices of the string St include a current sensor 11 (see FIG. 1 ) that detects the string current, a voltage sensor (not shown) that detects the total string voltage, and a switch (not shown) that connects / disconnects the string St.

[0047] The string controller SC transmits information about the state of the module M (hereinafter referred to as module state information) to the module interface M. Ｉ／Ｆ The module status includes the temperature, current, voltage, cell voltage of the module M, the status of the bypass mechanism B, and the like.

[0048] The string controller SC is connected to the module interface M Ｉ／Ｆ The SOC, SOH, charge / discharge power limit value, etc. of the storage battery of the module M are estimated based on the module status information received from the module interface M. Ｉ／Ｆ In this case, the module interface M Ｉ／Ｆ may transmit the estimation result to the string controller SC.

[0049] The string controller SC is connected to the module interface M Ｉ／Ｆ The state of the string St is estimated based on the module state information received from the string system controller SSC. Examples of the state of the string St include the string SOH, the string SOC, and the string charge / discharge power limit value. The state of the string St may be estimated by the string system controller SSC. In this case, the string controller SC may transmit the module state information and the estimated result of the state of the storage battery to the string system controller SSC.

[0050] If the cell voltage, the total string current, the estimated value of the state of the string St, or the like is outside the threshold range, the string controller SC determines that the string St is abnormal. In this case, the string controller SC stops the operation of the string St or sends an abnormality notification to the string system controller SSC.

[0051] The string controller SC is connected to the module interface M Ｉ／Ｆ The string system controller SSC transmits to the string system controller SSC information required for processing of the string system controller SSC from among the information received from the module M and information estimated by itself. Information required for processing of the string system controller SSC includes the temperature, current, voltage, SOC, SOH, charge / discharge power limit value, cell voltage, state of the bypass mechanism B, string SOC, string SOH, string charge / discharge power limit value, etc. of the storage battery of the module M.

[0052] Here, the string system controller SSC determines instructions for each string St based on the "information required for processing by the string system controller SSC" received from the string controller SC, and transmits the instruction information to the string controller SC. These instructions include a charge / discharge instruction for the string St in the charge / discharge mode, an individual control instruction for the string St in the maintenance mode, and a state estimation instruction for the string St in the state estimation mode. Items of the charge / discharge instruction for the string St in the charge / discharge mode include, in addition to the string charge / discharge power instruction value, the control amount for the constant voltage mode, constant current mode, or constant power mode, and the operation method such as independent operation / grid-connected operation. Items of the individual control instruction for the string St in the maintenance mode include an instruction to individually control the bypass mechanism B. Items of the state estimation instruction in the state estimation mode include, for example, charging / discharging at a constant current and recording the voltage of the storage battery during this.

[0053] The string controller SC receives the above-mentioned instruction information for each string St from the string system controller SSC, and compares the instruction information received this time with the instruction information received last time to determine whether or not the bypass schedule for the string St needs to be updated. The bypass schedule for the string St is a plan for bypassing the storage battery by the bypass mechanism B, and is determined according to predetermined criteria. The string controller SC determines whether or not a switch from charge to discharge or from discharge to charge will occur in the string St, and if such a switch occurs, determines that the bypass schedule needs to be updated. If the bypass schedule needs to be updated, the string controller SC notifies the module interface M Ｉ／Ｆ and a bypass schedule for the battery based on the battery state information received from the storage battery status estimation unit.

[0054] On the other hand, the string controller SC is connected to the module interface M Ｉ／Ｆ The string controller SC determines whether or not control of the string charge / discharge power is necessary by comparing the current and previous module state information received from the string system controller SSC and the estimated result of the storage battery state. If control of the string charge / discharge power is necessary, the string controller SC transmits a control signal corresponding to the string charge / discharge power instruction value received from the string system controller SSC to the MCU101, which is a control device of the power converter PCS.

[0055] Here, the MCU 101 of the power converter PCS and the module interface M Ｉ／Ｆ The module interface M is connected to the MCU 100, which is a control device provided in the module, via dedicated signal lines 102, 103, and 104 (see FIG. 5). Ｉ／Ｆ A charge suppression signal (a cell upper limit voltage warning signal, which will be described later) is sent from the MCU 100 of the module interface M to the MCU 101 of the power converter PCS to instruct the suppression of charging power. Ｉ／ＦA discharge suppression signal (a cell lower limit voltage warning signal, which will be described later) instructing the MCU 101 of the power converter PCS to suppress discharge power is transmitted from the MCU 100 of the power converter PCS to the MCU 101 of the power converter PCS.

[0056] The MCU 101 of the power converter PCS controls the power converter PCS in response to the control signal so that the charge / discharge power of the string St approaches the string charge / discharge power instruction value. However, if the charge suppression signal or the discharge suppression signal is transmitted while the control signal is being transmitted, the MCU 101 of the power converter PCS prioritizes the charge suppression signal or the discharge suppression signal and controls the power converter PCS so that the charge / discharge power of the string St is suppressed. Then, when transmission of the charge suppression signal or the discharge suppression signal stops, the MCU 101 of the power converter PCS controls the power converter PCS in response to the control signal so that the charge / discharge power of the string St approaches the string charge / discharge power instruction value.

[0057] When the string controller SC receives a maintenance / stop command from the string system controller SSC, it analyzes the received maintenance / stop command and determines the type of maintenance to be performed, such as individual control, self-diagnosis, and battery replacement (hereinafter referred to as battery replacement).

[0058] An example of individual control is control for individually turning on / off cooling devices, etc. in the string St. An example of self-diagnosis is abnormality determination for detecting abnormalities that are difficult to detect during operation in the state estimation mode or the charge / discharge mode. Examples of abnormality determination include performing special control on the power converter PCS, etc. or the switches S1, S2 of the bypass mechanism B, acquiring the responses thereof using various sensors, and determining whether or not there is an abnormality. An example of battery replacement is providing guidance for replacing a battery in a module M that has deteriorated or has failed. When replacing a battery, a work guide is displayed on the display / input device of the power storage system controller PSC, and the power storage system 1 executes necessary control, such as stopping the string St whose battery is to be replaced.

[0059] When the string controller SC receives a state estimation instruction from the string system controller SSC, it compares the currently received string charge / discharge power instruction value with the previously received string charge / discharge power instruction value and determines whether there has been a change. When the string controller SC receives the state estimation instruction from the string system controller SSC and there is a change in the string charge / discharge power instruction value between the previous and current times, the string controller SC controls the power converters PCS and the switches S1 and S2 of the bypass mechanism B in a predetermined manner so that the state of the string St can be estimated. An example of a method for controlling the power converters PCS and the like during execution of the state estimation mode is a method for constant current control of the power converters PCS. Furthermore, an example of a method for controlling the switches S1 and S2 of the bypass mechanism B during execution of the state estimation mode is a method for sequentially bypassing the storage batteries of modules M that have become fully discharged during discharging.

[0060] The string controller SC is connected to the module interface M Ｉ／Ｆ The string controller SC also records the module status information received from the module interface M. Ｉ／Ｆ The parameters used for state estimation are updated as necessary based on the module state information received from the module M. These parameters include the SOH of the storage battery of module M, a map of charge / discharge limit values ​​of the storage battery of module M, and SOC-OCV (Open Circuit Voltage) characteristics.

[0061] Module Interface M Ｉ／Ｆ communicates with the string controller SC and the cell monitoring unit CMU. The MCU 100 controls the switches S1 and S2 of the bypass mechanism B, the cell monitoring unit CMU, etc. The module interface M Ｉ／Ｆreceives module status information from the cell monitoring unit CMU etc. The module status information includes the total voltage of the storage battery of the module M, the temperature of the module M, the cell voltage etc. The cell monitoring unit CMU receives detection signals from various sensors (not shown) such as a module voltage sensor that detects the voltage of the storage battery of the module M, a cell voltage sensor that detects the cell voltage, and a module temperature sensor that detects the temperature of the module M. The cell monitoring unit CMU may be configured as a standalone unit, and may be connected to the module interface M Ｉ／Ｆ Alternatively, a battery cell monitoring IC (Integrated Circuit) may be used within the battery cell.

[0062] Module Interface M Ｉ／Ｆ receives module status information from the cell monitoring unit CMU, and the MCU 100 estimates the status of the storage battery of the module M based on the received information. Examples of the estimated status of the storage battery of the module M include the SOC, SOH, and charge / discharge power limit value of the storage battery of the module M. Note that the estimation of the status of the storage battery of the module M may be performed by the string controller SC.

[0063] Module Interface M Ｉ／Ｆ For example, if the detected values ​​of the module voltage sensor, cell voltage sensor, and module temperature sensor or the estimated value of the storage battery state of the module M are outside the threshold range, the module interface M determines that the module M is abnormal. Ｉ／Ｆ The module M that has been determined to have an abnormality is shut off by the switch S2 of the bypass mechanism B, or an abnormality notification is sent to the string controller SC. If the cell voltage exceeds the upper threshold or falls below the lower threshold, a cell upper limit voltage warning signal or a cell lower limit voltage warning signal, which will be described later, is sent to the module interface M. Ｉ／Ｆ to the MCU 101 of the power converter PCS.

[0064] Module Interface M Ｉ／Ｆtransmits to the string controller SC information required for processing by a higher-level controller such as the string controller SC, among the information received from the cell monitoring unit CMU and information estimated by itself. Information required for processing by the string controller SC includes the temperature, current, voltage, SOC, SOH, charge / discharge power limit value, cell voltage, and the state of the switches S1 and S2 of the bypass mechanism B of the storage battery of the module M.

[0065] Here, the string controller SC is connected to the module interface M Ｉ／Ｆ Based on the "information required for processing by the string controller SC" received from the module interface M, instructions for each module M are determined. Ｉ／Ｆ This instruction may include bypass control of module M by switches S1 and S2 of bypass mechanism B, cutoff control of the storage battery of module M by switch S2 of bypass mechanism B, etc.

[0066] Module Interface M Ｉ／Ｆ If there is a change between the current instruction information received from the string controller SC and the previous instruction information, the MCU 100 controls the switches S1 and S2 of the bypass mechanism B to execute the bypass control or cutoff control described above. Ｉ／Ｆ When there is a change in the information received from the cell monitoring unit CMU and the information estimated by itself, the module interface M executes exceptional control as necessary without relying on instructions from the upper controller. Ｉ／Ｆ sends an instruction to the cell monitoring unit CMU to perform cell balancing of the storage batteries of the module M.

[0067] 3 and 4 are graphs illustrating updating of the power storage system charge / discharge power instruction value and the string charge / discharge power instruction value assigned to each string St. As shown in these graphs, the power storage system charge / discharge power instruction value is updated so as to change from a current value to a target value over a predetermined period (a slope control period for the power storage system charge / discharge power in the figures).

[0068] 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 St is updated. This updating of the string charge / discharge power instruction value of each string St 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 updating of the string charge / discharge power instruction value of each string St after the storage system charge / discharge power instruction value is performed for the purpose of balancing the charge / discharge power between the strings St.

[0069] 3 shows the relationship between the power storage system charge / discharge power instruction value and the string charge / discharge power instruction value of each string St and time when control for suppressing the response speed of updating the power storage system charge / discharge power instruction value (hereinafter referred to as standard slope control) is executed. The standard slope control is executed for the purpose of suppressing abrupt changes in the power storage system charge / discharge power when updating the power storage system charge / discharge power instruction value.

[0070] 4 shows the relationship between the power storage system charge / discharge power instruction value and the string charge / discharge power instruction value of each string St and time when control for increasing the response speed of updating the power storage system charge / discharge power instruction value (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 power storage system charge / discharge power instruction value.

[0071] 3, 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 string St is updated so as to gradually change from the current value to the target value.

[0072] Here, the power storage system charge / discharge power instruction value is the sum of the string charge / discharge power instruction values ​​of each string St. Therefore, the string system controller SSC determines the string charge / discharge power instruction value of each string St so that the string charge / discharge power instruction value of each string St gradually changes from its current value to its target value, and the sum of the string charge / discharge power instruction values ​​of each string St gradually changes from its current value to its target value.

[0073] 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 St 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 St 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 St 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.

[0074] The string system controller SSC calculates a string charge / discharge power instruction value for each string St at each predetermined cycle during the slope control period for the charge / discharge power of the power storage system, and transmits the calculated value to each string controller SC by unicast communication. This 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).

[0075] After transmitting the string charge / discharge power instruction value to all string controllers SC, the string system controller SSC broadcasts a flag for updating the control of the power converter PCS (hereinafter referred to as the PCS control update flag) to all string controllers SC.

[0076] 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 string St 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 string St gradually changes in order to adjust the balance of the string charge / discharge power of each string St.

[0077] 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 string St for the purpose of balancing the charge / discharge power of each string St. At the same time, the string system controller SSC also calculates a change ΔP2 in the string charge / discharge power instruction value for each string St 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.

[0078] During the slope control period of the string charge / discharge power, the string system controller SSC transmits the string charge / discharge power instruction value of each string St to each string controller SC by unicast communication at the predetermined cycle. This string charge / discharge power instruction value is a value obtained by adding the change amount ΔP2 to the estimated current value.

[0079] The string system controller SSC transmits the string charge / discharge power instruction value to all the string controllers SC by unicast communication, and then transmits a PCS control update flag to all the string controllers SC by broadcast communication.

[0080] 4, when the shortest slope control is performed, the power storage system charge / discharge power instruction value changes from the current value to the target value over a shorter slope control period (e.g., 200 ms to 2 s) than when the standard slope control is performed. During this slope control period, the string charge power instruction value of each string St is updated so as to change from the current value to the intermediate target value in one cycle.

[0081] After the power storage system charge / discharge power instruction value is updated, the power storage system charge / discharge power instruction value is maintained, while the string charge / discharge power instruction value of each string St is updated. The string charge / discharge power instruction value of each string St 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.

[0082] Here, the power storage system charge / discharge power instruction value is the sum of the string charge / discharge power instruction values ​​of each string St. Therefore, the string system controller SSC determines the string charge / discharge power instruction value of each string St so that the string charge / discharge power instruction value of each string St changes from the current value to the intermediate target value in one cycle, and the sum of the string charge / discharge power instruction values ​​of each string St changes from the current value to the target value in one cycle.

[0083] Before the start of the 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 St. The string system controller SSC transmits the intermediate target values ​​for the string charge / discharge power instruction values ​​to all string controllers SC by broadcast communication during the slope control period for the charge / discharge power of the power storage system. Thereafter, the string system controller SSC transmits a PCS control update flag to all string controllers SC by broadcast communication. Note that it is not essential for the string system controller SSC to transmit the PCS control update flag by broadcast communication to all string controllers SC.

[0084] The string controller SC controls the power converters PCS in accordance with the received intermediate target value of the string charge / discharge power instruction value to update the charge / discharge power. Here, for a string St whose intermediate target value of the string charge / discharge power instruction value exceeds the charge / discharge power upper limit, the corresponding string controller SC limits the charge / discharge power to less than the intermediate target value and equal to or less than the charge / discharge power upper limit. In this case, the total value of the charge / discharge power of each string St falls below the target value of the battery storage system charge / discharge power. Therefore, in this case, the string system controller SSC corrects in advance the target value of the battery storage system charge / discharge power instruction value, taking into account the charge / discharge power upper limit received from the string controller SC.

[0085] When the shortest slope control is performed, the string charge / discharge power instruction value of each string St converges to an intermediate target value when the power storage system charge / discharge power instruction value converges to the target value. Because this intermediate target value is different from the final target value, the slope control of the string charge / discharge power is performed after the power storage system charge / discharge power instruction value converges to the target value. During the slope control period of the string charge / discharge power, the string charge / discharge power instruction value of each string St gradually changes from the intermediate target value to the final target value in order to adjust the balance of the string charge / discharge power of each string St.

[0086] When the storage system charge / discharge power instruction value converges to the target value, the string system controller SSC determines a final target value for the charge / discharge power instruction value of each string St for the purpose of balancing the charge / discharge power of each string St. At the same time, the string system controller SSC also calculates a change ΔP3 in the string charge / discharge power instruction value for each string St at a predetermined period (e.g., every few seconds). The change 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 string St by n, and is determined by the resolution.

[0087] During the slope control period of the string charge / discharge power, the string system controller SSC transmits the string charge / discharge power instruction value of each string St to all the string controllers SC by unicast communication at the predetermined cycles. This string charge / discharge power instruction value is a value obtained by adding the change amount ΔP3 to the estimated current value.

[0088] The string system controller SSC transmits the string charge / discharge power instruction value to all the string controllers SC by unicast communication, and then transmits a PCS control update flag to all the string controllers SC by broadcast communication.

[0089] FIG. 5 shows the string controller SC, the power converter PCS, and the module interface M shown in FIGS. 1 and 2. Ｉ／Ｆ 1 is a circuit diagram showing a communication circuit for performing communication between the module interface M. Ｉ／Ｆ The MCU 100 is connected to the string controller SC via a signal line 105, and is also connected to the MCU 101 of the power converter PCS via dedicated signal lines 103 and 104. Ｉ／Ｆ The MCU 100 is connected to GND (ground) via a signal line 102 .

[0090] Module Interface M Ｉ／Ｆ The power converter PCS includes a first photocoupler PC1 and a second photocoupler PC2. The light-emitting diode of the first photocoupler PC1 is connected to the MCU 100 and GND. The phototransistor of the first photocoupler PC1 is connected to the MCU 101 of the power converter PCS via a signal line 103 and to GND via a signal line 102. The light-emitting diode of the second photocoupler PC2 is connected to the MCU 100 and GND, and the phototransistor of the second photocoupler PC2 is connected to the MCU 101 of the power converter PCS via a signal line 104 and to GND via the signal line 102.

[0091] Module Interface M Ｉ／ＦWhen the cell voltage transmitted from the cell monitoring unit CMU exceeds the upper threshold, the MCU 100 transmits a cell upper limit voltage warning signal to the light emitting diode of the first photocoupler PC1. Ｉ／Ｆ When the cell voltage transmitted from the cell monitoring unit CMU falls below the lower limit threshold, the MCU 100 transmits a cell lower limit voltage warning signal to the light emitting diode of the second photocoupler PC2.

[0092] The first photocoupler PC1 causes the light emitting diode to emit light and the phototransistor to become conductive when a cell upper limit voltage warning signal is sent from the MCU 100. On the other hand, while the cell upper limit voltage warning signal is not being sent from the MCU 100, the first photocoupler PC1 insulates the MCU 100 on the input side from the MCU 101 on the output side.

[0093] The second photocoupler PC2 causes the light emitting diode to emit light and the phototransistor to become conductive when a cell lower limit voltage warning signal is sent from the MCU 100. On the other hand, the second photocoupler PC2 insulates the MCU 100 on the input side from the MCU 101 on the output side while the cell lower limit voltage warning signal is not being sent from the MCU 100.

[0094] The signal line 103 is connected to the power supply Vcc via resistor R1, which is a pull-up resistor. Resistor R1 is connected on the signal line 103 between the connection point of the first photocoupler PC1 and the connection point of the MCU 101. The cell upper limit voltage warning signal is an H-level signal. Therefore, while the cell upper limit voltage warning signal is not being transmitted, the input potential from the signal line 103 to the MCU 101 is the potential of the power supply Vcc, and while the cell upper limit voltage warning signal is being transmitted, the input potential from the signal line 103 to the MCU 101 is 0 (L level). When the input potential from the signal line 103 drops from the potential of the power supply Vcc to 0, the MCU 101 detects the cell upper limit voltage warning signal and controls the power converter PCS to suppress the charging power of the string St.

[0095] Similarly, the signal line 104 is connected to the power supply Vcc via resistor R2, which is a pull-up resistor. Resistor R2 is connected on the signal line 104 between the connection point of the second photocoupler PC2 and the connection point of the MCU 101. The cell lower limit voltage warning signal is an H-level signal. Therefore, while the cell lower limit voltage warning signal is not being transmitted, the input potential from the signal line 104 to the MCU 101 is the potential of the power supply Vcc, and while the cell lower limit voltage warning signal is being transmitted, the input potential from the signal line 104 to the MCU 101 is 0. When the input potential from the signal line 104 drops from the potential of the power supply Vcc to 0, the MCU 101 detects the cell lower limit voltage warning signal and controls the power converter PCS to suppress the discharge power of the string St.

[0096] The upper cell voltage warning signal and the lower cell voltage warning signal do not necessarily have to be H-level signals and may be L-level signals. In this case, while the upper cell voltage warning signal or the lower cell voltage warning signal is not being transmitted, the input potential from the signal line 103 or the signal line 104 of the MCU 101 is 0 (L level), and while the upper cell voltage warning signal or the lower cell voltage warning signal is being transmitted, the input potential from the signal line 103 or the signal line 104 of the MCU 101 is the potential of the power supply Vcc. The MCU 101 detects the upper cell voltage warning signal or the lower cell voltage warning signal when the input potential rises from 0 to the potential of the power supply Vcc, and controls the power converter PCS to suppress the charging power or discharging power of the string St.

[0097] 6 is a chart for explaining a communication method of a storage battery control device according to a comparative example. Similar to the storage battery control device 2 according to the above embodiment, the storage battery control device according to this comparative example includes a power storage system controller PSC, a string system controller SSC, a string controller SC, a power converter PCS, a module interface M, and Ｉ／Ｆ , and a cell monitoring unit CMU. However, the battery control device according to the comparative example includes a module interface M Ｉ／ＦThe battery control device 2 differs from the battery control device 2 according to the above embodiment in that the MCU 100 of the power converter PCS does not transmit a cell upper limit voltage warning signal and a cell lower limit voltage warning signal to the MCU 101 of the power converter PCS.

[0098] In the battery control device of the comparative example, when standard slope control and shortest slope control are executed, the string charge / discharge power instruction value of each string St is transmitted from the string system controller SSC to the string controller SC (charge / discharge power instruction), and a control signal corresponding to the string charge / discharge power instruction value of each string St is transmitted from the string controller SC to the power converter PCS.

[0099] On the other hand, when the standard slope control and the shortest slope control are performed, the cell voltage information is transmitted from the cell monitoring unit CMU to the module interface M. Ｉ／Ｆ , and the voltage of the storage battery of module M is transmitted to module interface M Ｉ／Ｆ The calculated voltage of the storage battery of module M is calculated by the module interface M Ｉ／Ｆ A signal is transmitted from the string controller SC to the power converter PCS, and the string controller SC determines whether the voltage is between an upper limit and a lower limit (determination of whether the voltage exceeds the upper or lower limit). If it is determined that the voltage exceeds the upper limit, a signal is transmitted from the string controller SC to the power converter PCS to instruct the power converter PCS to suppress charging power, and if it is determined that the voltage is below the lower limit, a signal is transmitted from the string controller SC to the power converter PCS to instruct the power converter PCS to suppress discharging power (charge and discharge power suppression).

[0100] In standard slope control, the string charge / discharge power command value gradually changes from the current value to the target value through multiple (e.g., 20) periodic processes. The power converter PCS can complete control within any period (e.g., 100 ms) from the charge / discharge power command. Therefore, when standard slope control is performed, the amount of change per unit time in the charge / discharge power of the string St is small. This allows ample time for the cell voltage to rise from the upper threshold to the upper cell voltage limit (maximum allowable cell voltage) and for the cell voltage to fall from the lower threshold to the lower cell voltage limit (minimum allowable cell voltage). Therefore, the periodic process from the cell monitoring unit CMU to the string controller SC, as shown in FIG. 6, can keep the cell voltage between the upper and lower limits.

[0101] In contrast, with minimum slope control, the string charge / discharge power instruction value changes from the current value to the target value in one periodic process, and the power converter PCS must complete the control within a short period (e.g., 60 ms). Therefore, when minimum slope control is performed, the amount of change per unit time in the charge / discharge power of the string St is large. This results in a lack of time between the time when the cell voltage exceeds the upper threshold and rises to the upper cell voltage limit (maximum allowable cell voltage), and between the time when the cell voltage falls below the lower threshold and falls to the lower cell voltage limit (minimum allowable cell voltage). Therefore, it is difficult to keep the cell voltage between the upper and lower limits through periodic processing from the cell monitoring unit CMU to the string controller SC, as shown in FIG. 6 .

[0102] Therefore, in the storage battery control device 2 according to this embodiment, the module interface M Ｉ／Ｆ The MCU 100 of the power converter PCS transmits a cell upper limit voltage warning signal and a cell lower limit voltage warning signal to the MCU 101 of the power converter PCS, thereby shortening the time from when the cell monitoring unit CMU transmits cell voltage information to when the power converter PCS responds to the charge / discharge power suppression control.

[0103] 7 is a chart illustrating a communication method of the battery control device 2 shown in FIGS. 1 and 2 . In the battery control device 2 according to this embodiment, as in the comparative example described above, when standard slope control and shortest slope control are performed, a string charge / discharge power instruction value is transmitted from the string system controller SSC to the string controller SC (charge / discharge power instruction), and a control signal corresponding to the string charge / discharge power instruction value is transmitted from the string controller SC to the power converter PCS. When standard slope control is performed, the control is completed within an arbitrary period (e.g., 100 ms) from the charge / discharge power instruction. In contrast, when shortest slope control is performed, the power converter PCS completes the control within a short period (e.g., 60 ms) from the charge / discharge power instruction.

[0104] On the other hand, when the standard slope control and the shortest slope control are performed, the cell voltage information is transmitted from the cell monitoring unit CMU to the module interface M. Ｉ／Ｆ and sent to the module interface M Ｉ／Ｆ In the module interface M, it is determined whether the cell voltage is between the upper and lower thresholds (determination of whether the cell voltage exceeds the upper or lower limit). If the cell voltage exceeds the upper threshold, a cell upper limit voltage warning signal and a GND signal are output to the module interface M. Ｉ／Ｆ When the cell voltage is below the lower limit threshold, a cell lower limit voltage warning signal and a GND signal are sent to the module interface M. Ｉ／Ｆ to the power converter PCS.

[0105] This reduces the time from when the cell monitoring unit CMU transmits cell voltage information to when the power converter PCS responds to the charge / discharge power suppression control, compared to the comparative example described above. Therefore, it becomes possible to keep the cell voltage between the upper and lower limits not only when standard slope control is being performed but also when shortest slope control is being performed.

[0106] 8 is a graph showing the transitions between the charge / discharge power instruction value and the actual charge / discharge power, and a timing chart showing the ON / OFF timing of the cell upper limit voltage warning signal and the cell lower limit voltage warning signal. As shown in the graph of FIG. 8, the actual charge / discharge power of each string St changes with a delay relative to the change in the string charge / discharge power instruction value of each string St. During charging, the actual charge power of each string St changes to approach the charge power instruction value, and during discharging, the discharge power of each string St changes to approach the discharge power instruction value. The charge power instruction value is set to a value lower than the charge / discharge upper limit power of each string St, and the discharge power instruction value is set to a value higher than the charge / discharge lower limit power of each string St.

[0107] When charging the string St, if the cell voltage of the module M in the string St exceeds the upper threshold, the module interface M Ｉ／Ｆ The upper cell voltage threshold is set to a value lower than the upper cell voltage limit (hereinafter referred to as the upper cell voltage limit). Therefore, when the cell voltage approaches the upper cell voltage limit, the module interface M Ｉ／Ｆ A cell upper limit voltage warning signal is sent from

[0108] While the cell upper limit voltage warning signal is detected by the MCU 101, the charging power of the string St is reduced by the power converter PCS. Then, when the cell upper limit voltage warning signal is no longer detected by the MCU 101, the charging power of the string St is increased by the power converter PCS so that it approaches the charging power instruction value.

[0109] During the discharge of the string St, if the cell voltage of the module M in the string St falls below the lower limit threshold, the module interface M Ｉ／Ｆ The cell voltage lower limit warning signal is sent from the module interface M. Here, the cell voltage lower limit threshold is set to a value higher than the cell voltage lower limit (hereinafter referred to as the cell voltage lower limit). Therefore, when the cell voltage approaches the cell voltage lower limit, the module interface M Ｉ／Ｆ A cell low voltage warning signal is sent from the

[0110] While the cell low voltage limit warning signal is detected by the MCU 101, the discharge power of the string St is reduced by the power converter PCS. Then, when the cell low voltage limit warning signal is no longer detected by the MCU 101, the discharge power of the string St is increased by the power converter PCS so that it approaches the discharge power command value.

[0111] 9 is a flowchart for explaining the charge control of the battery control device 2 shown in FIG. 1 and FIG. 2. As shown in this flowchart, when the charge control of the power storage system 1 is started, the MCU 101 of the power converter PCS determines whether or not it has received a cell upper limit voltage warning signal (step S11). In this step, the MCU 101 determines whether or not the input potential from the signal line 103 is 0 (L level).

[0112] If the MCU 101 has not received a cell upper limit voltage warning signal (NO in step S11), it controls the power converter PCS so that the charging power of the string St approaches the charging power instruction value (charging power control in step S12). On the other hand, if the MCU 101 has received a cell upper limit voltage warning signal (YES in step S11), it controls the power converter PCS so that the charging power of the string St is reduced (charging power reduction in step S13).

[0113] By repeating the above steps S11 to S13, the charging power of the string St is repeatedly increased to approach the charging power instruction value, and the charging power of the string St is repeatedly decreased to keep the cell voltage below the cell upper limit voltage.

[0114] 1 and 2. As shown in this flowchart, when discharge control of the power storage system 1 is started, the MCU 101 of the power converter PCS determines whether or not it has received a cell lower limit voltage warning signal (step S101). In this step, the MCU 101 determines whether or not the input potential from the signal line 104 is 0 (L level).

[0115] When the MCU 101 has not received a cell lower limit voltage warning signal (NO in step S101), it controls the power converter PCS so that the discharge power of the string St approaches the discharge power instruction value (discharge power control in step S102). On the other hand, when the MCU 101 has received a cell lower limit voltage warning signal (YES in step S101), it controls the power converter PCS so that the discharge power of the string St is suppressed (discharge power suppression in step S103).

[0116] By repeating the above steps S101 to S103, the discharge power of string St is repeatedly increased to approach the discharge power instruction value, and the discharge power of string St is repeatedly decreased to raise the cell voltage above the cell lower limit voltage.

[0117] As described above, in the storage battery control device 2 according to this embodiment, the module interface M Ｉ／Ｆ The MCU 100 of the power converter PCS receives a detection signal of the cell voltage from the cell monitoring unit CMU, and when the cell voltage is equal to or higher than the upper threshold, transmits a charge suppression signal to suppress the charging power of the string St to the MCU 101 of the power converter PCS. The MCU 101 receives a control signal corresponding to the charging power instruction value from the string controller SC, and also transmits a control signal corresponding to the charging power instruction value to the module interface M. Ｉ／Ｆ While not receiving the charge suppression signal from the MCU 100, the MCU 101 controls the power converter PCS so that the charge power of the string St approaches the charge power instruction value. Ｉ／Ｆ While receiving a charge suppression signal from the MCU 100, the power converter PCS is controlled so that the charging power of the string St is suppressed.

[0118] This reduces communication delays between the transmission of cell voltage information by the cell monitoring unit CMU and the response of the charge power suppression control by the power converter PCS. Therefore, in the energy storage system 1 in which the performance of the storage battery cells C in the string St varies, it is possible to control the charging of the string St while maintaining the cell voltage below the upper limit value.

[0119] In addition, in the storage battery control device 2 according to this embodiment, the module interface M Ｉ／Ｆ The MCU 100 of the power converter PCS receives a detection signal of the cell voltage from the cell monitoring unit CMU, and when the cell voltage is equal to or higher than the lower threshold, transmits a discharge suppression signal for suppressing the discharge power of the string St to the MCU 101 of the power converter PCS. The MCU 101 receives a control signal corresponding to the discharge power instruction value from the string controller SC, and also transmits a control signal corresponding to the discharge power instruction value to the module interface M. Ｉ／Ｆ While not receiving the discharge suppression signal from the MCU 100, the MCU 101 controls the power converter PCS so that the discharge power of the string St approaches the discharge power instruction value. Ｉ／Ｆ While receiving the discharge suppression signal from the MCU 100, the power converter PCS is controlled so that the discharge power of the string St is suppressed.

[0120] This reduces communication delays between the transmission of cell voltage information by the cell monitoring unit CMU and the response of discharge power suppression control by the power converter PCS. Therefore, in the energy storage system 1 in which the performance of the storage battery cells C in the string St varies, it is possible to control the discharge of the string St while maintaining the cell voltage higher than the lower limit.

[0121] In addition, the battery control device 2 according to this embodiment includes a module interface M Ｉ／Ｆ and a resistor R1 as a pull-up resistor connected between the first photocoupler PC1 and the MCU 101 on the signal line 103. This allows the MCU 100 and the MCU 101 to be electrically isolated from each other, and enables the MCU 100 to transmit a cell upper limit voltage warning signal to the first photocoupler PC1.

[0122] In addition, the battery control device 2 according to this embodiment includes a module interface M Ｉ／Ｆand a resistor R2 as a pull-up resistor connected between the second photocoupler PC2 and the MCU 101 on the signal line 103. This allows the MCU 100 and the MCU 101 to be electrically insulated from each other, and enables the MCU 100 to transmit a cell lower limit voltage warning signal to the second photocoupler PC2.

[0123] 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.

[0124] For example, in the above embodiment, the first photocoupler PC1 and the second photocoupler PC2 are used to connect the module interface M Ｉ／Ｆ Although the MCU 100 of the power converter PCS and the MCU 101 of the power converter PCS can be insulated from each other, this is not essential. Furthermore, the upper cell voltage limit warning signal and the lower cell voltage limit warning signal are transmitted using separate photocouplers (first photocoupler PC1 and second photocoupler PC2) and separate signal lines 103 and 104, respectively. However, this is not limiting and they may be transmitted using a single photocoupler and a single signal line. In this case, the MCU 101 receives the upper and lower cell voltage limit warning signals, but since the MCU 101 knows whether it is controlling charging or discharging, it can perform charge / discharge power suppression control.

[0125] In the above-described embodiment, the string system controller SSC transmits a string charge / discharge power instruction value to the string controller SC. However, the power storage system controller PSC and the string system controller SSC may be integrated, and the integrated controller may transmit a string charge / discharge power instruction value to the string controller SC. Alternatively, one of the multiple string controllers SC may be a master controller and the others may be slave controllers, and the master controller may transmit a string charge / discharge power instruction value to the slave controller.

[0126] Here, the features of the embodiments of the battery control device and the power storage system according to the present invention described above will be briefly summarized and listed below in [1] to [4]. [1] A battery control device (2) for controlling a power storage system (1) including strings (St, St1 to Stx) each including a plurality of storage battery modules (M, M1 to Mn) connected in series, and power converters (PCS, PCS1 to PCSx) that convert charge / discharge power of the strings (St, St1 to Stx), wherein the storage battery modules (M, M1 to Mn) include a plurality of storage battery cells (C) connected in series, and cell voltage detection units (CMU, CMU1 to CMUn) that detect voltages of the storage battery cells (C), the battery control device (2) comprising: a plurality of module control units (100) that are provided corresponding to the storage battery modules (M, M1 to Mn) and control the storage battery modules (M, M1 to Mn); and a power converter control unit (101) that controls the power converters (PCS, PCS1 to PCSx). and string control units (SC, SC1 to SCx) provided corresponding to the strings (St, St1 to Stx), communicating with a plurality of the module control units (100), the power converter control unit (101), and a host control unit (SSC), and transmitting to the power converter control unit (101) a control signal for controlling the power converters (PCS, PCS1 to PCSx) so that the charging power of the strings (St, St1 to Stx) approaches a charging power instruction value received from the host control unit (SSC), wherein the module control unit (100) receives a detection signal of the voltage of the storage battery cell (C) from the cell voltage detection unit (CMU, CMU1 to CMUn), and when the voltage of the storage battery cell (C) is equal to or higher than an upper threshold, transmits to the power converter control unit (101) a charge suppression signal for suppressing the charging power of the strings (St, St1 to Stx), The power converter control unit (101) receives the control signal from the string control unit (SC, SC1 to SCx) and controls the power converters (PCS, PCS1 to PCSx) so that the charging power of the strings (St, St1 to Stx) approaches the charging power instruction value while not receiving the charge suppression signal from the module control unit (100), anda battery control device (2) that controls the power converters (PCS, PCS1 to PCSx) to suppress charging power of the strings (St, St1 to Stx) while receiving the control signal from the strings (SC1 to SCx) and the charge suppression signal from the module control unit (100). [2] A battery control device (2) for controlling a power storage system (1) including strings (St, St1 to Stx) each including a plurality of storage battery modules (M, M1 to Mn) connected in series, and power converters (PCS, PCS1 to PCSx) that convert charge / discharge power of the strings (St, St1 to Stx), wherein the storage battery modules (M, M1 to Mn) include a plurality of storage battery cells (C) connected in series, and cell voltage detection units (CMU, CMU1 to CMUn) that detect voltages of the storage battery cells (C), the battery control device (2) comprising: a plurality of module control units (100) that are provided corresponding to the storage battery modules (M, M1 to Mn) and control the storage battery modules (M, M1 to Mn); and a power converter control unit (101) that controls the power converters (PCS, PCS1 to PCSx). and string control units (SC, SC1 to SCx) provided corresponding to the strings (St, St1 to Stx), communicating with the plurality of module control units (100), the power converter control unit (101), and a host control unit (SSC), and transmitting to the power converter control unit (101) a control signal for controlling the power converters (PCS, PCS1 to PCSx) so that the discharge power of the strings (St, St1 to Stx) approaches a discharge power instruction value received from the host control unit (SSC), wherein the module control unit (100) receives a detection signal of the voltage of the storage battery cell (C) from the cell voltage detection unit (CMU, CMU1 to CMUn), and when the voltage of the storage battery cell (C) is equal to or lower than a lower limit threshold, transmits to the power converter control unit (101) a discharge suppression signal for suppressing the discharge power of the strings (St, St1 to Stx), The power converter control unit (101) receives the control signal from the string control unit (SC, SC1 to SCx) and, while not receiving the discharge suppression signal from the module control unit (100), controls the power converter (PCS,a control unit (100) for controlling the power converters (PCS, PCS1 to PCSx) to suppress discharge power of the strings (St, St1 to Stx) while receiving the control signal from the string control unit (SC, SC1 to SCx) and the discharge suppression signal from the module control unit (100). [3] The battery control unit (2) according to [1] or [2], further comprising: photocouplers (PC1, PC2) provided on signal lines (103, 104) connecting the module control unit (100) and the power converter control unit (101); and pull-up resistors (R1, R2) connected on the signal lines (103, 104) between the photocouplers (PC1, PC2) and the power converter control unit (101). [4] A power storage system (1) including a string (St, St1 to Stx) having a plurality of storage battery modules (M, M1 to Mn) connected in series, and a power converter (PCS, PCS1 to PCSx) that converts the charge / discharge power of the string (St, St1 to Stx), wherein the storage battery modules (M, M1 to Mn) include a plurality of storage battery cells (C) connected in series, and a cell voltage detection unit (CMU, CMU1 to CMUn) that detects the voltage of the storage battery cells (C), and the power storage system (1) includes the storage battery control device (2) according to [1] or [2].

[0127] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0128] This application is based on a Japanese patent application (Patent Application No. 2024-001574) filed on January 10, 2024, the contents of which are incorporated herein by reference.

[0129] According to the present invention, it is possible to provide a battery control device and a power storage system that can keep the voltage of the battery cells in a battery module within an appropriate range regardless of whether there is variation in the performance of the battery cells in the string. The present invention that achieves this effect is useful for battery control devices and power storage systems.

[0130] 1: Energy storage system 2: Battery control device 100: MCU (module control unit) 101: MCU (power converter control unit) 103: Signal line 104: Signal line C: Battery cell CMU: Cell monitoring unit (cell voltage detection unit) CMU1: Cell monitoring unit (cell voltage detection unit) CMU2: Cell monitoring unit (cell voltage detection unit) CMUn: Cell monitoring unit (cell voltage detection unit) M: Module (battery module) M1: Module (battery module) M2: Module (battery module) Mn: Module (battery module) PC1: First photocoupler (photocoupler) PC2: Second photocoupler (photocoupler) PCS: Power converter PCS1: Power converter PCS2: Power converter PCSx: Power converter R1: Resistor (pull-up resistor) R2 : Resistor (pull-up resistor) SC : String controller (string control unit) SC1 : String controller (string control unit) SC2 : String controller (string control unit) SCx : String controller (string control unit) SSC : String system controller (host control unit) St : String St1 : String St2 : String Stx : String

Claims

1. A battery control device for controlling a power storage system including a string including a plurality of serially connected battery modules and a power converter that converts the charge and discharge power of the string, wherein the battery module includes a plurality of serially connected battery cells and a cell voltage detection unit that detects the voltage of the battery cells, the battery control device comprising: A plurality of module control units respectively provided corresponding to the battery modules for controlling the battery modules; A power converter control unit for controlling the power converter; A string control unit provided corresponding to the string, for communicating with the plurality of module control units, the power converter control unit, and a host control unit, and transmitting a control signal for controlling the power converter so that the charging power of the string approaches a charging power instruction value received from the host control unit; The module control unit receives a detection signal of the voltage of the battery cells from the cell voltage detection unit, and when the voltage of the battery cells is equal to or higher than an upper threshold value, transmits a charge suppression signal for suppressing the charging power of the string to the power converter control unit; The power converter control unit receives the control signal from the string control unit and controls the power converter to bring the charging power of the string close to the charging power instruction value while not receiving the charge suppression signal from the module control unit, and controls the power converter to suppress the charging power of the string while receiving the control signal from the string control unit and the charge suppression signal from the module control unit.

2. A battery control device for controlling a power storage system including a string including a plurality of serially connected battery modules and a power converter that converts charge and discharge power of the string, wherein the battery module includes a plurality of serially connected battery cells and a cell voltage detection unit that detects a voltage of the battery cells, the battery control device comprising: a plurality of module control units respectively provided corresponding to the battery modules and controlling the battery modules; a power converter control unit that controls the power converter; a string control unit provided corresponding to the string, communicating with the plurality of module control units, the power converter control unit, and a host control unit, and transmitting a control signal for controlling the power converter so that the discharge power of the string approaches a discharge power instruction value received from the host control unit; the module control unit receiving a detection signal of the voltage of the battery cells from the cell voltage detection unit, and when the voltage of the battery cells is equal to or lower than a lower threshold value, transmitting a discharge suppression signal for suppressing the discharge power of the string to the power converter control unit; and the power converter control unit controlling the power converter so that the discharge power of the string approaches the discharge power instruction value while receiving the control signal from the string control unit and not receiving the discharge suppression signal from the module control unit, and controlling the power converter so as to suppress the discharge power of the string while receiving the control signal from the string control unit and receiving the discharge suppression signal from the module control unit.

3. The battery control device according to claim 1 or 2, further comprising: a photocoupler provided on a signal line connecting the module control unit and the power converter control unit; and a pull-up resistor connected between the photocoupler and the power converter control unit in the signal line.

4. A power storage system including a string including a plurality of serially connected battery modules and a power converter that converts charge and discharge power of the string, wherein the battery module includes a plurality of serially connected battery cells and a cell voltage detection unit that detects a voltage of the battery cells, the power storage system comprising the battery control device according to claim 1 or 2.

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