Battery control device, power storage system, and battery control method

Abstract

To maintain target charging / discharging power (current) as a power storage system during execution of by-pass control, in the power storage system in which storage battery strings each are provided with a bypass circuit, to which a plurality of the storage battery strings are parallelly connected.SOLUTION: A storage battery control device 100 that performs: allocation of instruction values of power or current for charging or discharging of a plurality of storage battery strings STR1 to STRm; control of bypass switch units B1 to Bn; and control of power converters PC1 to PCm. Before performing the control of the bypass switch units B1 to Bn, the storage battery control device allocates the instruction values allocated to the storage battery strings STR1 to STRm to be bypass-controlled to one or more storage battery strings STR1 to STRm not to be bypass-controlled and stops the power converters PC1 to PCm of the storage battery strings STR1 to STRm to be bypass-controlled.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] There is known an energy storage system that includes a plurality of storage battery strings connected in parallel to a DC bus and a plurality of power converters provided for each storage battery string (see, for example, Patent Document 1). In the energy storage system described in Patent Document 1, the output value of each storage battery string is controlled so that the voltage value of the DC bus is maintained at a predetermined target voltage value. In addition, in the energy storage system described in Patent Document 1, the range of output values ​​that each storage battery string is caused to output is limited in order to prevent overcharging or overdischarging of the storage batteries.

[0003] On the other hand, there is known a power storage system including a plurality of storage batteries connected in series and a bypass circuit provided for each storage battery for switching the corresponding storage battery between a connected state and a bypassed state (see, for example, Patent Document 2). In the power storage system described in Patent Document 2, a storage battery that cannot discharge the required current is bypassed, and discharging is performed from the other storage batteries. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-79164 A [Patent Document 2] JP 2013-31247 A Summary of the Invention [Problem to be solved by the invention]

[0005] Consider a storage battery system in which the storage battery string described in Patent Document 1 is provided with the bypass circuit described in Patent Document 2. In this storage battery system, when bypass control is executed for a storage battery string in a loaded state, a sudden change occurs in the charge / discharge power (or current) of the storage battery string, which affects the charge / discharge power (or current) of the storage battery system as a whole. If the charge / discharge power (or current) of the other storage battery strings can be changed so as to complement the sudden change in the charge / discharge power (or current) of the storage battery string subject to bypass control, the charge / discharge power (or current) of the storage battery system as a whole will not be affected. However, it is difficult to completely synchronize the switching control of the bypass circuit of the storage battery string subject to bypass control with the control of the charge / discharge power (or current) of the other storage battery strings. Therefore, there is a possibility that the target charge / discharge power (or current) of the storage battery system cannot be maintained when the bypass control is executed.

[0006] In view of the above circumstances, the present invention aims to provide a battery control device, a battery storage system, and a battery control method that can maintain a target charge / discharge power (or current) of the battery storage system when bypass control is performed in a battery storage system in which multiple battery strings are connected in parallel and each battery string is provided with a bypass circuit. [Means for solving the problem]

[0007] The battery control device of the present invention is a battery control device that controls a power storage system including a plurality of battery strings connected in parallel to each other, the battery strings including a plurality of batteries connected in series, a bypass circuit that switches the plurality of batteries between a connected state and a bypass state, and a power converter that converts the input / output power of the battery strings, and performs assignment of instruction values ​​for power or current for charging or discharging the plurality of battery strings, control of the bypass circuit, and control of the power converter, and assigns the instruction value that was assigned to the battery string that is the target of control of the bypass circuit before executing control of the bypass circuit to one or more of the battery strings that are not the target of control of the bypass circuit, and stops the power converter of the battery string that is the target of control of the bypass circuit.

[0008] The energy storage system of the present invention is an energy storage system comprising a plurality of storage battery strings connected in parallel to each other and a battery control device that controls the storage battery strings, wherein the storage battery strings comprise a plurality of storage batteries connected in series, a bypass circuit that switches the plurality of storage batteries between a connected state and a bypass state, and a power converter that converts the input / output power of the storage battery strings, and the battery control device assigns instruction values ​​for the charging or discharging power or current of the plurality of storage battery strings, controls the bypass circuit, and controls the power converter, and assigns the instruction value that was assigned to the storage battery string that is the target of the control of the bypass circuit before executing the control of the bypass circuit to one or more of the storage battery strings that are not the target of the control of the bypass circuit, and stops the power converter of the storage battery string that is the target of the control of the bypass circuit.

[0009] The battery control method of the present invention is a battery control method executed by a battery control device that controls a power storage system including a plurality of battery strings connected in parallel to each other, the battery strings including a plurality of batteries connected in series, a bypass circuit that switches the plurality of batteries between a connected state and a bypass state, and a power converter that converts the input / output power of the battery strings, and the method assigns instruction values ​​for charging or discharging power or current of the plurality of battery strings, controls the bypass circuit, and controls the power converter, assigns the instruction values ​​that were assigned to the battery string that is the target of control of the bypass circuit before executing the control of the bypass circuit to one or more battery strings that are not the target of control of the bypass circuit, and stops the power converter of the battery string that is the target of control of the bypass circuit. Effect of the Invention

[0010] According to the present invention, in a power storage system in which multiple storage battery strings are connected in parallel and each storage battery string is provided with a bypass circuit, it is possible to maintain a target charge / discharge power (or current) of the power storage system when bypass control is executed. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a circuit diagram showing an outline of a power storage system including a battery control device according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a graph showing the relationship between the instruction value of the charging power and elapsed time when the instruction value of the charging power to be allocated to the storage battery string is changed. [Diagram 3] FIG. 3 is a flowchart for explaining a process for changing an instruction value of the charging power of a battery string. [Figure 4] FIG. 4 is a graph showing the relationship between the instruction value of the discharge power and elapsed time when the instruction value of the discharge power to be allocated to the storage battery string is changed. [Diagram 5]FIG. 5 is a flowchart for explaining a process of changing the instruction value of the discharge power of the battery string. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described below along with preferred embodiments. Note that the present invention is not limited to the embodiments shown below, and the embodiments can be appropriately modified within the scope of the present invention. In addition, in the embodiments shown below, some configurations are omitted from illustration and description, but for the details of the omitted technologies, publicly known or well-known technologies are appropriately applied within the scope of not causing any contradiction with the contents described below.

[0013] Fig. 1 is a circuit diagram showing an outline of a power storage system 1 including a battery control device 100 according to one embodiment of the present invention. As shown in this diagram, the power storage system 1 includes m sets of storage battery strings STR1 to STRm (m is an integer of 2 or more), a string bus 3, and the battery control device 100. The m sets of storage battery strings STR1 to STRm are connected in parallel to each other and to an external system (not shown) via the string bus 3. The power storage system 1 is a stationary or vehicle-mounted power source.

[0014] Each of the storage battery strings STR1 to STRm includes n (n is an integer of 2 or more) storage battery modules M1 to Mn connected in series. Although not particularly limited, the storage battery strings STR1 to STRm in this embodiment are regenerated second-hand storage batteries, and the storage battery modules M1 to Mn have different degrees of deterioration. The storage battery modules M1 to Mn are, for example, a plurality of cells of secondary batteries such as lithium ion batteries or lithium ion capacitors connected together.

[0015] The storage battery modules M1 to Mn are charged by receiving power from an external system via the string bus 3 and power converters PC1 to PCm described later. In addition, the storage battery modules M1 to Mn supply power to the external system via the power converters PC1 to PCm and the string bus 3.

[0016] The external system includes a load, a generator, etc. When the power storage system 1 is for stationary use, household appliances, commercial power systems, liquid crystal displays, communication modules, etc. are the loads, and a solar power generation system, etc. are the generators. On the other hand, when the power storage system 1 is for vehicle use, the drive motor, air conditioner, various vehicle electrical equipment, etc. are the loads. The drive motor is both a load and a generator.

[0017] The battery strings STR1 to STRm may include n battery cells or battery packs connected in series, instead of the n battery modules M1 to Mn connected in series. The power storage system 1 may include a bypass circuit that bypasses each battery cell or each battery pack.

[0018] Each of the storage battery strings STR1 to STRm includes one power converter PC1 to PCm and n bypass switch units B1 to Bn. Each of the storage battery strings STR1 to STRm also includes n voltage sensors 12, one current sensor 13, one voltage sensor 14, n temperature sensors (not shown), and a number of cell voltage sensors (not shown).

[0019] The power converters PC1 to PCm are DC / DC converters or DC / AC converters, and are connected to the string bus 3. In addition, the power converters PC1 to PCm are connected to the positive electrode of the starting storage battery module M1 and the negative electrode of the terminal storage battery module Mn.

[0020] When the storage battery strings STR1-STRm are being charged, the power converters PC1-PCm convert the voltage input from the string bus 3 according to an instruction value of the charging power (or current) described below, and output the converted voltage to the multiple storage battery modules M1-Mn. Here, the voltage on the side of the storage battery strings STR1-STRm changes according to the bypass state of the storage battery modules M1-Mn (the number of bypassed storage battery modules M1-Mn) and the charging state of the storage battery modules M1-Mn. Therefore, when the storage battery strings STR1-STRm are being charged, the power converters PC1-PCm convert the voltage input from the string bus 3 into the voltage on the side of the storage battery strings STR1-STRm, and output the converted voltage to the multiple storage battery modules M1-Mn.

[0021] When the storage battery strings STR1-STRm are being discharged, the power converters PC1-PCm convert the voltage input from the multiple storage battery modules M1-Mn according to an instruction value of the discharge power (or current) described below, and output the converted voltage to the string bus 3. Here, the input voltage of the power converters PC1-PCm during discharge varies according to the bypass state of the storage battery modules M1-Mn and the charge state of the storage battery modules M1-Mn. This causes variations in the input voltage of the power converters PC1-PCm among the storage battery strings STR1-STRm during discharge. Therefore, when the storage battery strings STR1-STRm are being discharged, the power converters PC1-PCm convert the input voltage to a voltage that matches the other storage battery strings STR1-STRm, and output the converted voltage to the string bus 3.

[0022] When the current flowing through the string bus 3 is a direct current, the power converters PC1 to PCm are DC / DC converters, and when the current flowing through the string bus 3 is an alternating current, the power converters PC1 to PCm are DC / AC converters. When the current flowing through the string bus 3 is an alternating current, the power converters PC1 to PCm are provided with synchronization means for following changes in instantaneous values.

[0023] The voltage sensor 12 is connected between the positive and negative terminals of each of the storage battery modules M1-Mn, detects the terminal voltage of each of the storage battery modules M1-Mn, and transmits a detection signal to the string controllers C1-Cm described below. The current sensor 13 is provided on the power line PL of each of the storage battery strings STR1-STRm, detects the charge / discharge current of each of the storage battery strings STR1-STRm, and transmits a detection signal to the string controllers C1-Cm. The voltage sensor 14 is provided on the power line PL of each of the storage battery strings STR1-STRm, detects the total voltage of each of the storage battery strings STR1-STRm, and transmits a detection signal to the string controllers C1-Cm.

[0024] A temperature sensor is provided in each of the storage battery modules M1-Mn to detect the temperature of each of the storage battery modules M1-Mn and transmit a detection signal to the string controllers C1-Cm. A cell voltage sensor is provided in each of the storage battery cells of each of the storage battery modules M1-Mn to detect the voltage of each storage battery cell and transmit a detection signal to the string controllers C1-Cm.

[0025] The bypass switch units B1 to Bn are provided for each of the storage battery modules M1 to Mn. Each of the bypass switch units B1 to Bn includes a bypass line BL and switches S1 and S2. The bypass line BL is a power line that bypasses each of the storage battery modules M1 to Mn. The switch S1 is provided on the bypass line BL. The switch S1 is, for example, a mechanical relay or a semiconductor switch. The switch S2 is provided between the positive electrode of each of the storage battery modules M1 to Mn and one end of the bypass line BL. The switch S2 is, for example, a mechanical relay or a semiconductor switch.

[0026] The starting battery module M1 and the ending battery module Mn are connected to an external system via power converters PC1-PCm and a string bus 3. When the switches S1 are turned OFF and the switches S2 are turned ON in all the bypass switch units B1-Bn, all the battery modules M1-Mn are connected in series to the external system. On the other hand, when the switches S2 are turned OFF and the switches S1 are turned ON in any of the bypass switch units B1-Bn, the battery module M1-Mn corresponding to that bypass switch unit B1-Bn is bypassed.

[0027] The battery control device 100 includes m string controllers C1 to Cm and one system controller 101. The string controllers C1 to Cm are provided for each of the battery strings STR1 to STRm.

[0028] The string controllers C1-Cm control the switches S1, S2 of the bypass switch units B1-Bn of the corresponding battery strings STR1-STRm and the corresponding power converters PC1-PCm. The power converters PC1-PCm convert the charge / discharge voltages of the corresponding battery strings STR1-STRm under the control of the corresponding string controllers C1-Cm.

[0029] The string controllers C1-Cm execute detection of the states of the corresponding storage battery strings STR1-STRm, estimation of the states of the corresponding storage battery strings STR1-STRm, notification of device control requests to the system controller 101, etc. Examples of detection of the states of the storage battery strings STR1-STRm include detection of the charge / discharge currents of the storage battery strings STR1-STRm based on a detection signal from the current sensor 13, detection of the total voltage of the storage battery strings STR1-STRm based on a detection signal from the voltage sensor 14, detection of the voltages of the storage battery modules M1-Mn based on a detection signal from the voltage sensor 12, detection of the temperatures of the storage battery modules M1-Mn based on a detection signal from a temperature sensor, detection of the voltages of the storage battery cells based on a detection signal from a cell voltage sensor, etc. Examples of estimation of the states of the storage battery strings STR1-STRm include estimation of the SOC (State of Charge) and SOH (State of Health) of the storage battery modules M1-Mn, and estimation of the SOC and SOH of the storage battery strings STR1-STRm. Furthermore, notifications of device control requests to the system controller 101 include requests for switching control of the switches S1, S2 of the bypass switch units B1 to Bn, requests for control of the power converters PC1 to PCm, and the like.

[0030] Methods for estimating SOH include methods using charge / discharge tests, current integration methods, open circuit voltage measurements, terminal voltage measurements, model-based methods (all of which use the change in SOC over time), AC impedance measurements, model-based methods using an adaptive digital filter, linear regression from IV characteristics (current-voltage characteristics) (the slope of the straight line of the IV characteristics), and step response methods (all of which are methods of estimation using the increase in internal resistance over time).

[0031] Methods for estimating the SOC include various known methods such as a current integration method, a method (voltage method) that is calculated from the OCV (Open Circuit Voltage), a method that combines the current integration method and the voltage method, etc. Also, the OCV can be estimated using various known methods that estimate the OCV using the change in terminal voltage over time or the increase in internal resistance over time.

[0032] Here, the string controllers C1 to Cm calculate the charge / discharge power of the corresponding storage battery strings STR1 to STRm and transmit the calculation results to the system controller 101. The charge / discharge power of each of the storage battery strings STR1 to STRm is calculated using the product of the charge / discharge current of each of the storage battery strings STR1 to STRm detected by the current sensor 13 of each of the storage battery strings STR1 to STRm and the total voltage of the storage battery strings STR1 to STRm detected by the voltage sensor 14 of each of the storage battery strings STR1 to STRm.

[0033] The system controller 101 is a controller that performs overall control of the entire power storage system 1, and executes 1:m communication with m string controllers C1-Cm. This system controller 101 monitors the states of the storage battery strings STR1-STRm, judges whether to accept device control requests from the string controllers C1-Cm, and notifies the string controllers C1-Cm of permission for the device control requests. The system controller 101 also sets instruction values ​​for the charge / discharge power (or current) of each of the storage battery strings STR1-STRm, and transmits the instruction values ​​for the charge / discharge power (or current) to the string controllers C1-Cm.

[0034] The system controller 101 monitors the states of the storage battery strings STR1-STRm based on detection results and estimation results of the states of the storage battery strings STR1-STRm transmitted from the string controllers C1-Cm. The system controller 101 then calculates an instruction value of the charge / discharge power (or current) to be allocated to each of the storage battery strings STR1-STRm, according to an instruction of the input / output power (or current) of the entire power storage system 1 received from a higher-level system (not shown) and the states of the storage battery strings STR1-STRm.

[0035] Here, the system controller 101 determines the priority order of the storage battery strings STR1-STRm to which the instruction values ​​of charge / discharge power (or current) are assigned according to the state of the storage battery strings STR1-STRm being monitored. Then, the system controller 101 assigns the instruction values ​​of charge / discharge power (or current) to each of the storage battery strings STR1-STRm according to the determined priority order. For example, the system controller 101 may assign instruction values ​​of charge / discharge power (or current) to the storage battery strings STR1-STRm having a relatively high priority order, but may not assign instruction values ​​of charge / discharge power (or current) to the storage battery strings STR1-STRm having a relatively low priority order. Also, the system controller 101 may assign larger instruction values ​​of charge / discharge power (or current) to the storage battery strings STR1-STRm having a relatively high priority order, but may assign smaller instruction values ​​of charge / discharge power (or current) to the storage battery strings STR1-STRm having a relatively low priority order.

[0036] Methods for determining the priority order include a method of determining the priority order according to the integrated charge / discharge capacity of each of the storage battery strings STR1-STRm, a method of determining the priority order according to the SOH of each of the storage battery strings STR1-STRm, and a method of determining the priority order randomly each time the charge / discharge power (or current) is changed. In a method of determining the priority order according to the integrated charge / discharge capacity of each of the storage battery strings STR1-STRm, the priority order of the storage battery strings STR1-STRm with smaller integrated charge / discharge capacities is higher. In a method of determining the priority order according to the SOH of each of the storage battery strings STR1-STRm, the priority order of the storage battery strings STR1-STRm with higher SOH is higher.

[0037] The system controller 101 judges whether to accept a device control request from the string controllers C1-Cm according to the state of the other storage battery strings STR1-STRm that are being monitored. If the system controller 101 accepts a device control request from the string controllers C1-Cm, it transmits a notification of acceptance of the control request to the string controllers C1-Cm. The string controllers C1-Cm that receive the notification of acceptance of the control request for the bypass switch units B1-Bn execute switching control of the corresponding bypass switch units B1-Bn. Furthermore, the string controllers C1-Cm that receive the notification of acceptance of the control request for the power converters PC1-PCm execute control of the corresponding power converters PC1-PCm.

[0038] In addition, in a situation where a device control request is not transmitted from a certain string controller C1-Cm, the system controller 101 may transmit a device control instruction to the string controller C1-Cm as necessary. Furthermore, when the string controller C1-Cm detects an abnormality in the storage battery string STR1-STRm, the string controller C1-Cm may stop the operation of the corresponding power converter PC1-PCm, regardless of the presence or absence of a control permission notification or a control instruction from the system controller 101.

[0039] Here, when the system controller 101 receives a control request for the bypass switch units B1-Bn from any of the string controllers C1-Cm, it stops the operation of the power converters PC1-PCm (hereinafter, PC') corresponding to the string controller C1-Cm (hereinafter, C'). By stopping the operation of the power converter PC', the storage battery strings STR1-STRm (hereinafter, STR') corresponding to the power converter PC' are put into an unloaded state.

[0040] Then, the system controller 101 assigns "0" to the instruction value of the charge / discharge power (or current) of the storage battery string STR' in the no-load state. On the other hand, the system controller 101 assigns values ​​capable of complementing the charge / discharge power (or current) of the storage battery string STR' in the no-load state to the instruction values ​​of the charge / discharge power (or current) of the other one or more storage battery strings STR1 to STRm.

[0041] At this time, in the process of changing the command values ​​of the charge / discharge power (or current) of the storage battery strings STR', STR1 to STRm, the system controller 101 gradually and continuously changes the command value of the charge / discharge power (or current) of each of the storage battery strings STR', STR1 to STRm from a current value to a target value. That is, the system controller 101 gradually and continuously changes the command value of the charge / discharge power (or current) of the storage battery string STR' in a no-load state (subject to bypass control) from a current value to "0". On the other hand, the system controller 101 gradually and continuously changes the command value of the charge / discharge power (or current) of one or more of the storage battery strings STR1 to STRm in a loaded state (not subject to bypass control) from a current value to a target value. The process of changing the command values ​​of the charge / discharge power (or current) of each of the storage battery strings STR', STR1 to STRm will be described below.

[0042] 2 is a graph showing the relationship between the charging power instruction value and elapsed time when changing the instruction value of the charging power allocated to the storage battery string STR' subject to bypass control and the other storage battery strings STR1-STRm (hereinafter referred to as the charging power instruction value). This graph shows an example in which the charging power instruction value of the storage battery string STR' subject to bypass control decreases to 0, and the charging power instruction values ​​of the other storage battery strings STR1-STRm increase. In this example, the charging power instruction value that was allocated to the storage battery string STR' subject to bypass control is reassigned to the other storage battery strings STR1-STRm.

[0043] As shown by the solid line in Fig. 2, the charging power instruction value of the storage battery string STR' that is the target of the bypass control gradually and continuously decreases over a predetermined time from the current value to the target value of "0." On the other hand, as shown by the dashed line in Fig. 2, the charging power instruction values ​​of the other storage battery strings STR1 to STRm gradually and continuously increase over a predetermined time from the current value to the target value.

[0044] The process of changing the charging power instruction values ​​of the storage battery strings STR', STR1 to STRm will be described in detail below. Note that instead of changing the charging power instruction values ​​of the storage battery strings STR', STR1 to STRm, the charging current instruction values ​​of the storage battery strings STR', STR1 to STRm may be changed. In that case, the same process as that described below may be executed.

[0045] 3 is a flowchart for explaining a process for changing the charging power instruction values ​​of the storage battery strings STR', STR1 to STRm. First, in step S1, the system controller 101 (see FIG. 1) acquires the latest information (detection results and estimation results) on the states of the storage battery strings STR', STR1 to STRm (see FIG. 1) from the string controllers C', C1 to Cm (see FIG. 1).

[0046] Next, in step S2, the system controller 101 determines whether or not a bypass control request has been received from the string controllers C1 to Cm. If a negative determination is made in step S2, the process proceeds to step S1, and if a positive determination is made in step S2, the process proceeds to step S3.

[0047] In step S3, the system controller 101 selects one or more storage battery strings STR1-STRm to which the charging power instruction value of the storage battery string STR' subject to bypass control is to be transferred. In this step, the storage battery string STR1-STRm that has a surplus capacity to independently bear the charging power of the storage battery string STR' subject to bypass control, or the storage battery strings STR1-STRm that have a surplus capacity to jointly bear the charging power of the storage battery string STR' subject to bypass control, is selected according to the above-mentioned priority order.

[0048] Next, in step S4, a charging power instruction value of one or more storage battery strings STR1-STRm to which the charging power of the storage battery string STR' subject to bypass control is transferred is determined. Specifically, the charging power instruction value of the one or more storage battery strings STR1-STRm selected in step S3 is increased by the charging power instruction value of the storage battery string STR' subject to bypass control.

[0049] Next, the system controller 101 repeatedly executes the loop process of steps S5 to S7 until the charging power instruction value of the storage battery strings STR1 to STRm selected in step S3 reaches the target charging power instruction value. Here, in steps S5 to S7, the system controller 101 gradually and continuously increases the charging power instruction value of each of the storage battery strings STR1 to STRm from the current value to the target value by a predetermined amount ΔP1. On the other hand, in steps S5 to S7, the system controller 101 gradually and continuously decreases the charging power instruction value of the storage battery string STR' that is the target of the bypass control from the current value to 0 by a predetermined amount ΔP1.

[0050] First, in step S5, the system controller 101 changes the charging power instruction value of the storage battery strings STR', STR1 to STRm by a predetermined amount ΔP1. This predetermined amount ΔP1 is set to a small amount so as to meet the purpose of preventing a sudden change in charging power. When the difference between the current value and the target value of the charging power instruction value is small, this predetermined amount ΔP1 may be equal to the difference between the current value and the target value of the charging power instruction value. On the other hand, when the difference between the current value and the target value of the charging power instruction value is relatively large, this predetermined amount ΔP1 may be smaller than the difference between the current value and the target value of the charging power instruction value. When this predetermined amount ΔP1 is smaller than the difference between the current value and the target value of the charging power instruction value, the updating of the charging power instruction value is repeatedly executed multiple times.

[0051] Next, in step S6, the system controller 101 waits for a predetermined time T1 after transmitting the charge power instruction value to the string controllers C', C1 to Cm. This predetermined time T1 is set in consideration of the time required for the string controllers C', C1 to Cm to control the charge power of the storage battery strings STR1 to STRm and the rate of change of the charge power. Here, the rate of change of the charge power is set low so as to meet the purpose of preventing abrupt changes in the charge power.

[0052] Next, in step S7, the system controller 101 determines whether or not the current charging power instruction value of each of the storage battery strings STR1 to STRm has reached the target charging power instruction value of each of the storage battery strings STR1 to STRm. If a negative determination is made in step S7, the process proceeds to step S5, and if a positive determination is made in step S7, the process proceeds to step S8.

[0053] In step S8, the system controller 101 stops the operation of the power converter PC' corresponding to the storage battery string STR' that is the target of the bypass control, thereby causing the storage battery string STR' that is the target of the bypass control to enter a no-load state.

[0054] Next, in step S9, the system controller 101 transmits a permission notification for the bypass control request to the string controller C' corresponding to the storage battery string STR' that is the target of the bypass control. As a result, the string controller C' executes the bypass control of the storage battery string STR' that is the target of the bypass control.

[0055] Next, in step S10, the system controller 101 determines whether or not the bypass control request from the string controller C' has been released. Step S10 is repeated until a positive determination is made in step S10, and if a positive determination is made in step S10, the process proceeds to step S11.

[0056] In step S11, the system controller 101 assigns 0 to the charge power instruction value of the storage battery string STR' that was the target of the bypass control. Next, in step S12, the system controller 101 starts the operation of the power converter PC' corresponding to the storage battery string STR' that was the target of the bypass control. This ends the process.

[0057] 4 is a graph showing the relationship between the discharge power instruction value and elapsed time when the instruction values ​​for the discharge power (hereinafter referred to as the discharge power instruction values) of the storage battery string STR' subject to bypass control and one or more other storage battery strings STR1-STRm are changed. This graph shows an example in which the discharge power instruction value of the storage battery string STR' subject to bypass control decreases to 0, and the discharge power instruction values ​​of the other storage battery strings STR1-STRm increase. In this example, the discharge power instruction value that was assigned to the storage battery string STR' subject to bypass control is reassigned to the other storage battery strings STR1-STRm.

[0058] As shown by the solid line in Fig. 4, the discharge power instruction value of the storage battery string STR' that is the target of the bypass control gradually and continuously decreases over a predetermined time from the current value to the target value of "0." On the other hand, as shown by the dashed line in Fig. 4, the discharge power instruction values ​​of the other storage battery strings STR1 to STRm gradually and continuously increase over a predetermined time from the current value to the target value.

[0059] The process of changing the discharge power instruction values ​​of the battery strings STR', STR1 to STRm will be described in detail below. Note that instead of changing the discharge power instruction values ​​of the battery strings STR', STR1 to STRm, the instruction values ​​of the discharge currents of the battery strings STR', STR1 to STRm may be changed. In that case, the same process as that described below may be executed.

[0060] 5 is a flowchart for explaining a process for changing the discharge power instruction values ​​of the storage battery strings STR', STR1 to STRm. First, in step S101, the system controller 101 (see FIG. 1) acquires the latest information (detection results and estimation results) on the states of the storage battery strings STR', STR1 to STRm (see FIG. 1) from the string controllers C', C1 to Cm (see FIG. 1).

[0061] Next, in step S102, the system controller 101 determines whether or not a bypass control request has been received from the string controllers C1 to Cm. If a negative determination is made in step S102, the process proceeds to step S101, and if a positive determination is made in step S102, the process proceeds to step S103.

[0062] Next, in step S103, the system controller 101 selects one or more storage battery strings STR1-STRm to which the discharged power of the storage battery string STR' subject to bypass control is transferred. In this step, the storage battery string STR1-STRm that has a surplus capacity to independently bear the discharged power of the storage battery string STR' subject to bypass control, or the multiple storage battery strings STR1-STRm that have a surplus capacity to jointly bear the discharged power of the storage battery string STR' subject to bypass control, is selected according to the above-mentioned priority order.

[0063] Next, in step S104, a target discharge power instruction value of one or more storage battery strings STR1-STRm to which the discharge power of the storage battery string STR' subject to bypass control is transferred is determined. Specifically, the discharge power instruction value of the one or more storage battery strings STR1-STRm selected in step S103 is increased by the discharge power instruction value of the storage battery string STR' subject to bypass control.

[0064] Next, the system controller 101 repeatedly executes the loop process of steps S105 to S107 until the discharge power instruction value of the storage battery strings STR1 to STRm selected in step S103 reaches the target discharge power instruction value. Here, in steps S105 to S107, the system controller 101 gradually and continuously increases the discharge power instruction value of each of the storage battery strings STR1 to STRm from the current value to the target value by a predetermined amount ΔP2. On the other hand, in steps S105 to S107, the system controller 101 gradually and continuously decreases the discharge power instruction value of the storage battery string STR' that is the target of the bypass control from the current value to 0 by a predetermined amount ΔP2.

[0065] First, in step S105, the system controller 101 changes the discharge power instruction value of the storage battery strings STR', STR1 to STRm by a predetermined amount ΔP2. This predetermined amount ΔP2 is set to a small amount so as to meet the purpose of preventing a sudden change in discharge power. When the difference between the current value of the discharge power instruction value and the target value is small, this predetermined amount ΔP2 may be equal to the difference between the current value of the discharge power instruction value and the target value. On the other hand, when the difference between the current value of the discharge power instruction value and the target value is relatively large, this predetermined amount ΔP2 may be smaller than the difference between the current value of the discharge power instruction value and the target value. When this predetermined amount ΔP2 is smaller than the difference between the current value of the discharge power instruction value and the target value, the update of the discharge power instruction value is repeatedly executed multiple times.

[0066] Next, in step S106, the system controller 101 waits for a predetermined time T1 after transmitting the discharge power instruction value to the string controllers C', C1-Cm. This predetermined time T1 is set in consideration of the time required for the string controllers C', C1-Cm to control the discharge power of the storage battery strings STR', STR1-STRm and the rate of change of the discharge power. Here, the rate of change of the discharge power is set low so as to meet the purpose of preventing abrupt changes in the discharge power.

[0067] Next, in step S107, the system controller 101 determines whether or not the current discharge power instruction value of each of the storage battery strings STR1 to STRm has reached the target discharge power instruction value of each of the storage battery strings STR1 to STRm. If a negative determination is made in step S107, the process proceeds to step S105, and if a positive determination is made in step S107, the process proceeds to step S108.

[0068] In step S108, the system controller 101 stops the operation of the power converter PC' corresponding to the storage battery string STR' that is the target of the bypass control, thereby causing the storage battery string STR' that is the target of the bypass control to enter a no-load state.

[0069] Next, in step S109, the system controller 101 transmits a permission notification for the bypass control request to the string controller C' corresponding to the storage battery string STR' that is the target of the bypass control. As a result, the string controller C' executes the bypass control of the storage battery string STR' that is the target of the bypass control.

[0070] Next, in step S110, the system controller 101 determines whether or not the bypass control request from the string controller C' has been released. Step S110 is repeated until an affirmative determination is made in step S110, and if an affirmative determination is made in step S110, the process proceeds to step S111.

[0071] In step S111, the system controller 101 assigns 0 to the discharge power instruction value of the storage battery string STR' that was the target of the bypass control. Next, in step S112, the system controller 101 starts operation of the power converter PC' corresponding to the storage battery string STR' that was the target of the bypass control. This ends the process.

[0072] As described above, in the battery control device 100 of this embodiment, when a request for bypass control is notified from the string controller C' to the system controller 101, the system controller 101 notifies the string controller C' of permission for bypass control. At this time, before notifying the string controller C' of permission for bypass control, the system controller 101 allocates the instruction value of charge / discharge power (or current) that was allocated to the storage battery string STR' that is the target of the bypass control to one or more storage battery strings STR1 to STRm that are not the target of the bypass control. Then, the system controller 101 stops the operation of the power converter PC' of the storage battery string STR' that is the target of the bypass control.

[0073] Here, if bypass control of the storage battery string STR' subject to bypass control is executed while the storage battery string STR' is in a loaded state, a sudden change occurs in the charge / discharge power (or current) of the storage battery string STR'. In response to this, the storage battery control device 100 of the present embodiment allocates the charge / discharge power (or current) of the storage battery string STR' subject to bypass control to one or more storage battery strings STR1-STRm, and executes bypass control of the storage battery string STR' after placing the storage battery string STR' in an unloaded state. This makes it possible to maintain a target charge / discharge power (or current) of the power storage system 1 when bypass control is executed.

[0074] Here, in the storage battery control device 100 of this embodiment, the system controller 101 assigns the instruction value of the charge / discharge power (or current) assigned to the storage battery string STR' subject to the bypass control to one or more storage battery strings STR1 to STRm that are not subject to the bypass control. At this time, the system controller 101 repeatedly executes a process of changing the instruction value of the charge / discharge power (or current) of the storage battery strings STR', STR1 to STRm toward the target instruction value of the charge / discharge power (or current) by predetermined amounts ΔP1, ΔP2 each time until the target value is reached. Here, the predetermined amounts ΔP1, ΔP2 are smaller than the difference between the target value and the current value of the instruction value of the charge / discharge power (or current). As a result, when the instruction value of the charge / discharge power (or current) of the storage battery strings STR', STR1 to STRm is changed from the current value to the target value, it is possible to suppress a sudden change in the charge / discharge power (or current) in the storage battery strings STR', STR1 to STRm, and it is possible to maintain the target charge / discharge power (or current) of the energy storage system 1.

[0075] 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 without departing from the spirit of the present invention, and publicly known or well-known technologies may be combined as appropriate.

[0076] For example, in the above-described embodiment, the command values ​​of the charge / discharge power (or current) of the storage battery strings STR', STR1 to STRm are changed gradually and continuously over time to the target value by a predetermined amount ΔP1 or a predetermined amount ΔP2. However, for example, in cases where the effect of the change in the charge / discharge power (or current) of the storage battery strings STR', STR1 to STRm on the charge / discharge power (or current) of the energy storage system 1 is minor, the command values ​​of the charge / discharge power (or current) of the storage battery strings STR', STR1 to STRm may be changed all at once.

[0077] In the above embodiment, the system controller 101 transmits command values ​​of charge / discharge power (or current) to the string controllers C1-Cm. However, a controller in which the system controller 101 and the string controllers C1-Cm are integrated may set command values ​​of charge / discharge power (or current) of each of the storage battery strings STR1-STRm. [Explanation of symbols]

[0078] 1: Energy storage system 100: Battery control device B1~Bn: Bypass switch unit (bypass circuit) M1~Mn: Battery module (battery) PC1~PCm, PC': Power converter STR1~STRm,STR': Battery strings ΔP1: Predetermined amount (small change) ΔP2: Predetermined amount (small change)

Claims

1. A battery control device for controlling a power storage system including a plurality of battery strings connected in parallel to each other, the battery strings including a plurality of batteries connected in series, a bypass circuit for switching the plurality of batteries between a connected state and a bypass state, and a power converter for converting input / output power of the battery strings, Assigning power or current indications for charging or discharging the plurality of battery strings, controlling the bypass circuit, and controlling the power converter; A battery control device that, before executing control of the bypass circuit, assigns the instruction value that was assigned to the battery string that is the target of control of the bypass circuit to one or more of the battery strings that are not the target of control of the bypass circuit, and stops the power converter of the battery string that is the target of control of the bypass circuit.

2. 2. The battery control device according to claim 1, wherein when the instruction value that was assigned to the storage battery string that is the target of control of the bypass circuit is assigned to one or more storage battery strings that are not the target of control of the bypass circuit, a process of increasing the instruction value toward the target value by an amount of change that is smaller than the difference between the target value and the current value is repeatedly performed until the instruction value reaches the target value.

3. A power storage system including a plurality of storage battery strings connected in parallel with each other, and a storage battery control device that controls the storage battery strings, wherein the storage battery strings include a plurality of storage batteries connected in series, a bypass circuit that switches the plurality of storage batteries between a connected state and a bypass state, and a power converter that converts input / output power of the storage battery strings; the battery control device performs allocation of instruction values ​​of power or current for charging or discharging the plurality of battery strings, control of the bypass circuit, and control of the power converter; a power storage system that, before executing control of the bypass circuit, assigns the instruction value that was assigned to the storage battery string that is the target of control of the bypass circuit to one or more storage battery strings that are not the target of control of the bypass circuit, and stops the power converter of the storage battery string that is the target of control of the bypass circuit.

4. A battery control method executed by a battery control device that controls a power storage system including a plurality of battery strings connected in parallel to each other, the battery strings including a plurality of batteries connected in series, a bypass circuit that switches the plurality of batteries between a connected state and a bypass state, and a power converter that converts input / output power of the battery strings, Assigning power or current indications for charging or discharging the plurality of battery strings, controlling the bypass circuit, and controlling the power converter; a power supply control method for supplying the power to one or more battery strings that are not subject to the control of the bypass circuit to the power supply of the battery string that is not subject to the control of the bypass circuit before the control of the bypass circuit is executed, and stopping the power converter of the battery string that is subject to the control of the bypass circuit.

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