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

Abstract

A battery control device (100) allocates an instruction value of charging or discharging power or current for a plurality of battery strings (STR1 to STRm), controls bypass switch units (B1 to Bn), and controls power converters (PC1 to PCm). Before controlling the bypass switching units (B1 to Bn), the battery control device (100) allocates an instruction value allocated to the battery strings (STR1 to STRm) to be bypass-controlled to one or more battery strings (STR1 to STRm) that do not need to be bypass-controlled, and stops the power converters (PC1 to PCm) of the battery strings (STR1 to STRm) to be bypass-controlled.

Description

Technical Field

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

[0002] There is known a power storage system including a plurality of storage battery strings connected in parallel to a DC bus, and a plurality of power converters each provided for each corresponding storage battery string (for example, see Patent Document 1). In the power 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 the power storage system described in Patent Document 1, the range of the output value output by each storage battery string is limited to prevent overcharging and overdischarging of the storage battery.

[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 and configured to switch the corresponding storage battery between a connection state and a bypass state (for example, see Patent Document 2). In the power storage system described in Patent Document 2, a storage battery that cannot discharge a required current is bypassed, and discharge is performed from the other storage batteries.

[0004] Citation List

[0005] Patent Literature

[0006] Patent Document 1: JP2014-79164A

[0007] Patent Document 2: JP2013-31247A Summary of the invention

[0008] Technical issues

[0009] A power storage system in which a bypass circuit described in Patent Document 2 is provided in the battery string described in Patent Document 1 will be considered. In this power storage system, when bypass control is performed on the battery string under load, the charging and discharging power (or current) of the battery string changes drastically, thereby affecting the charging and discharging power (or current) of the entire power storage system. Here, if the charging and discharging power (or current) of other battery strings can be changed to supplement the drastic change in the charging and discharging power (or current) of the battery string to be subjected to bypass control, the charging and discharging power (or current) of the entire power storage system will not be affected. However, it is difficult to synchronize the switch control of the bypass circuit of the battery string to be subjected to bypass control with the control of the charging and discharging power (or current) of other battery strings. Therefore, when bypass control is performed, it is possible that the target charging and discharging power (or current) of the power storage system cannot be maintained.

[0010] In view of the above situation, an object of the present invention is to provide a battery control device, a battery system, and a battery control method, which can maintain the target charging and discharging power (or current) of the battery system when performing bypass control in a battery system in which multiple battery strings are connected in parallel and each battery string is provided with a bypass circuit.

[0011] Solution to the problem

[0012] A battery control device according to the present invention is a battery control device for controlling a power storage system including a plurality of battery strings connected in parallel to each other, the battery string including a plurality of batteries connected in series, a bypass circuit configured to switch the plurality of batteries between a connection state and a bypass state, and a power converter configured to convert input and output power of the battery string. The battery control device allocates instruction values ​​of charging or discharging power or current of the plurality of battery strings, controls the bypass circuit, and controls the power converter. Before controlling the bypass circuit, the battery control device allocates the instruction value allocated to the battery string to be controlled by the bypass circuit to one or more of the battery strings not controlled by the bypass circuit, and stops the power converter of the battery string to be controlled by the bypass circuit.

[0013] The power storage system according to the present invention is a power storage system including a plurality of battery strings connected in parallel to each other, and a battery control device configured to control the battery strings, the battery strings including a plurality of batteries connected in series, a bypass circuit configured to switch the plurality of batteries between a connection state and a bypass state, and a power converter configured to convert input and output power of the battery strings. The battery control device allocates instruction values ​​of charging or discharging power or current of the plurality of battery strings, controls the bypass circuit, and controls the power converter. Before controlling the bypass circuit, the battery control device allocates the instruction value allocated to the battery strings to be controlled by the bypass circuit to one or more of the battery strings not controlled by the bypass circuit, and stops the power converter of the battery strings controlled by the bypass circuit.

[0014] The battery control method according to the present invention is a battery control method performed by a battery control device for controlling a power storage system including a plurality of battery strings connected in parallel to each other, the battery string including a plurality of batteries connected in series, a bypass circuit configured to switch the plurality of batteries between a connection state and a bypass state, and a power converter configured to convert input and output power of the battery string. The battery control method includes assigning an indication value of charging or discharging power or current of the plurality of battery strings, controlling the bypass circuit, and controlling the power converter. The battery control method includes, before controlling the bypass circuit, assigning the indication value assigned to the battery string to be controlled by the bypass circuit to one or more of the battery strings not controlled by the bypass circuit, and stopping the power converter of the battery string controlled by the bypass circuit.

[0015] Advantageous Effects of the Invention

[0016] According to the present invention, in a power storage system in which a plurality of 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 charging and discharging power (or current) of the power storage system while executing bypass control. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : is a circuit diagram schematically showing a power storage system including a storage battery control device according to an embodiment of the present invention.

[0018] Figure 2 : is a graph showing the relationship between the indicated value of charging power and the elapsed time when the indicated value of charging power to be distributed to the storage battery strings is changed.

[0019] Figure 3 Detailed Description of the Invention The flowchart shows a process for changing the instruction value of the charging power of the storage battery string.

[0020] Figure 4 : is a graph showing the relationship between the indicated value of the discharge power and the elapsed time when the indicated value of the charging power to be distributed to the storage battery string is changed.

[0021] Figure 5 Detailed description of the invention is a flowchart showing a process for changing the instruction value of the discharge power of the storage battery string. DETAILED DESCRIPTION

[0022] Hereinafter, the present invention will be described with reference to a preferred embodiment. The present invention is not limited to the embodiment described below, and the embodiment may be appropriately modified without departing from the gist of the present invention. In the embodiment described below, part of the configuration may not be described or shown in the drawings, and with respect to the details of the omitted technology, as long as it does not contradict the content described below, the known or well-known technology will be appropriately applied.

[0023] Figure 1 1 is a circuit diagram schematically showing a power storage system 1 including a battery control device 100 according to an embodiment of the present invention. As shown in the figure, the power storage system 1 includes m groups (m is an integer greater than or equal to 2) of battery strings STR1 to STRm, a string bus 3, and a battery control device 100. The m groups of battery strings STR1 to STRm are connected in parallel to each other through the string bus 3 and are connected together to an external system (not shown). The power storage system 1 is a fixed or vehicle-mounted power source.

[0024] The battery strings STR1 to STRm each include n (n is an integer greater than or equal to 2) battery modules M1 to Mn connected in series. Although not particularly limited, the battery strings STR1 to STRm according to the present embodiment are obtained by remanufacturing used batteries, and the battery modules M1 to Mn have different degrees of deterioration. The battery modules M1 to Mn are formed by connecting a plurality of secondary battery cells such as lithium-ion batteries and lithium-ion capacitors.

[0025] The storage battery modules M1 to Mn are charged by power supplied from an external system through the string bus 3 and power converters PC1 to PCm described later. The storage battery modules M1 to Mn supply power to the external system through the power converters PC1 to PCm and the string bus 3 .

[0026] The external system includes loads, generators, and the like. When the power storage system 1 is a stationary power storage system, household appliances, commercial power supply systems, liquid crystal displays, communication modules, and the like are used as loads, and a solar photovoltaic power generation system and the like are used as generators. On the other hand, when the power storage system 1 is a vehicle-mounted power storage system, a drive motor, an air conditioner, various vehicle-mounted electrical components, and the like are used as loads. The drive motor is both a load and a generator.

[0027] Each of the battery strings STR1 to STRm may include n battery cells or battery groups connected in series, instead of 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 group.

[0028] Each battery string STR1 to STRm includes one of the power converters PC1 to PCm and n bypass switch units B1 to Bn. Each battery string STR1 to STRm includes n voltage sensors 12, one current sensor 13, one voltage sensor 14, n temperature sensors (not shown), and a plurality of cell voltage sensors (not shown).

[0029] Power converters PC1 to PCm are DC / DC converters or DC / AC converters, and are connected to the string bus 3. A positive electrode of the battery module M1 at the start end and a negative electrode of the battery module Mn at the end end are connected to each of the power converters PC1 to PCm.

[0030] When the battery strings STR1 to STRm are charged, each power converter PC1 to PCm converts the voltage received from the string bus 3 according to the indicated value of the charging power (or current) described later, and outputs the converted voltage to the plurality of battery modules M1 to Mn. Here, the voltage on the side of each battery string STR1 to STRm varies due to the bypass state of the battery modules M1 to Mn (the number of bypassed battery modules M1 to Mn) and the charging state of the battery modules M1 to Mn. Therefore, when the battery strings STR1 to STRm are charged, each power converter PC1 to PCm converts the voltage received from the string bus 3 to the voltage on the side of each battery string STR1 to STRm, and outputs the converted voltage to the plurality of battery modules M1 to Mn.

[0031] When the battery strings STR1 to STRm are discharged, each power converter PC1 to PCm converts the voltage received from the plurality of battery modules M1 to Mn according to the indicated value of the discharge power (or current) described later, and outputs the converted voltage to the string bus 3. Here, the voltage input to each power converter PC1 to PCm during discharge varies due to the bypass state of the battery modules M1 to Mn and the charge state of the battery modules M1 to Mn. Therefore, during discharge, the voltage input to the power converter PC1 to PCm varies between the battery strings STR1 to STRm. Therefore, when the battery strings STR1 to STRm are discharged, each power converter PC1 to PCm converts the input voltage to a voltage matching the other battery strings STR1 to STRm, and outputs the converted voltage to the string bus 3.

[0032] When the current flowing through the string bus 3 is direct current, the power converters PC1 to PCm are DC / DC converters, and when the current flowing through the string bus 3 is alternating current, the power converters PC1 to PCm are DC / AC converters. When the current flowing through the string bus 3 is alternating current, each power converter PC1 to PCm is equipped with a synchronization unit that follows the instantaneous value change.

[0033] The voltage sensor 12 is connected between the positive and negative terminals of each battery module M1 to Mn, detects the voltage between the terminals of each battery module M1 to Mn, and sends the detection signal to each string controller C1 to Cm described later. The current sensor 13 is provided on the power line PL of each battery string STR1 to STRm, detects the charging and discharging current of each battery string STR1 to STRm, and sends the detection signal to each string controller C1 to Cm. The voltage sensor 14 is provided on the power line PL of each battery string STR1 to STRm, detects the total voltage of each battery string STR1 to STRm, and sends the detection signal to each string controller C1 to Cm.

[0034] Each battery module M1 to Mn is equipped with a temperature sensor for detecting the temperature of each battery module M1 to Mn and sending a detection signal to each string controller C1 to Cm. In addition, each battery cell of each battery module M1 to Mn is equipped with a battery voltage sensor for detecting the voltage of the battery cell and sending a detection signal to each string controller C1 to Cm.

[0035] The bypass switch units B1 to Bn are respectively arranged on the battery modules M1 to Mn. Each bypass switch unit B1 to Bn includes a bypass line BL and switches S1 and S2. The bypass line BL is a power line for bypassing each battery module M1 to Mn. The switch S1 is arranged on the bypass line BL. The switch S1 is, for example, a mechanical relay or a semiconductor switch. The switch S2 is arranged between the positive pole of each battery module M1 to Mn and one end of the bypass line BL. The switch S2 is, for example, a mechanical relay or a semiconductor switch.

[0036] The battery module M1 at the start end and the battery module Mn at the end end are connected to the external system through the power converters PC1 to PCm and the series bus 3. When the switch S1 in all the bypass switch units B1 to Bn is turned off and the switch S2 is turned on, all the battery modules M1 to Mn are connected in series to the external system. On the other hand, when the switch S2 in any one of the bypass switch units B1 to Bn is turned off and the switch S1 is turned on, the battery modules M1 to Mn corresponding to the bypass switch units B1 to Bn are bypassed.

[0037] The storage battery control device 100 includes m string controllers C1 to Cm and a system controller 101. The string controllers C1 to Cm are provided for the storage battery strings STR1 to STRm, respectively.

[0038] The string controllers C1 to Cm control the switches S1 and S2 of the bypass switch units B1 to Bn of the corresponding battery strings STR1 to STRm and the corresponding power converters PC1 to PCm. The power converters PC1 to PCm convert the charge and discharge voltages of the corresponding battery strings STR1 to STRm under the control of the corresponding string controllers C1 to Cm.

[0039] The string controllers C1 to Cm detect the states of the corresponding battery strings STR1 to STRm, estimate the states of the corresponding battery strings STR1 to STRm, and notify the system controller 101 of the device control request. Examples of the detection of the states of the battery strings STR1 to STRm include detecting the charge and discharge currents of the battery strings STR1 to STRm based on the detection signal of the current sensor 13, detecting the total voltage of the battery strings STR1 to STRm based on the detection signal of the voltage sensor 14, detecting the voltage of the battery modules M1 to Mn based on the detection signal of the voltage sensor 12, detecting the temperature of the battery modules M1 to Mn based on the detection signal from the temperature sensor, and detecting the voltage of the battery cells based on the detection signal of the battery voltage sensor. Examples of the estimation of the states of the battery strings STR1 to STRm include estimation of the state of charge (SOC) and the state of health (SOH) of the battery modules M1 to Mn, and estimation of the SOC and SOH of the battery strings STR1 to STRm. Furthermore, examples of notifying the system controller 101 of a device control request include notifying a switching control request for the switches S1 and S2 of the bypass switch units B1 to Bn, and notifying a control request for the power converters PC1 to PCm.

[0040] Examples of methods for estimating SOH include a method based on charge and discharge testing, a method based on a current integration method, a method based on open circuit voltage measurement, a method based on terminal voltage measurement, a model-based method (the above is a method using SOC changes over time), a method based on AC impedance measurement, a method obtained using a model-based adaptive digital filter, a method based on IV characteristics (current-voltage characteristics) through linear regression (the slope of the straight line of the IV characteristics), and a step response-based method (the above is a method for estimating using an increase in internal resistance over time).

[0041] Examples of methods for estimating SOC include various known methods such as a current integration method, a method (voltage method) obtained based on an open circuit voltage (OCV), and a method combining the current integration method and the voltage method. OCV can be estimated using various known methods that estimate using a change in terminal voltage over time or an increase in internal resistance over time.

[0042] Here, the string controllers C1 to Cm calculate the charging and discharging powers of the corresponding battery strings STR1 to STRm and transmit the calculation results to the system controller 101. The charging and discharging powers of the battery strings STR1 to STRm are calculated using the product of the charging and discharging currents of the battery strings STR1 to STRm detected by the current sensors 13 of the battery strings STR1 to STRm and the total voltages of the battery strings STR1 to STRm detected by the voltage sensors 14 of the battery strings STR1 to STRm.

[0043] The system controller 101 is a controller that controls the entire power storage system 1 as a whole, and performs 1:m communication with the m string controllers C1 to Cm. The system controller 101 monitors the states of the storage battery strings STR1 to STRm, determines whether to permit a device control request from the string controllers C1 to Cm, and notifies the string controllers C1 to Cm of the permit of the device control request. The system controller 101 sets the indicated values ​​of the charging and discharging power (or current) of the storage battery strings STR1 to STRm, and transmits the indicated values ​​of the charging and discharging power (or current) to the string controllers C1 to Cm.

[0044] The system controller 101 monitors the states of the storage battery strings STR1 to STRm based on the detection results and estimation results of the states of the storage battery strings STR1 to STRm sent from the string controllers C1 to Cm. Then, the system controller 101 calculates the indicated values ​​of the charging and discharging power (or current) to be distributed to each of the storage battery strings STR1 to STRm according to the instructions of the input and output power (or current) of the entire power storage system 1 received from the upper system (not shown) and the states of the storage battery strings STR1 to STRm.

[0045] Here, the system controller 101 determines the priority order of the storage battery strings STR1 to STRm to which the charging and discharging power (or current) indication values ​​are to be assigned according to the states of the monitored storage battery strings STR1 to STRm. Then, the system controller 101 assigns the indication values ​​of the charging and discharging power (or current) to the storage battery strings STR1 to STRm according to the determined priority order. For example, the system controller 101 may assign the indication values ​​of the charging and discharging power (or current) to the storage battery strings STR1 to STRm having a relatively high priority, but may not assign the indication values ​​of the charging and discharging amount (or current) to the storage battery strings STR1 to STRm having a lower priority. For example, the system controller 101 may assign a larger indication value of the charging and discharging power (or current) to the storage battery strings STR1 to STRm having a relatively high priority, and may assign a smaller indication value of the charging and discharging power (or current) to the storage battery strings STR1 to STRm having a relatively low priority.

[0046] Examples of methods for determining the priority order include determining the priority order based on the integrated charge and discharge capacity of each battery string STR1 to STRm, determining the priority order based on the SOH of each battery string STR1 to STRm, and randomly determining the priority order each time the charge and discharge power (or current) changes. In the method of determining the priority order based on the integrated charge and discharge capacity of each battery string STR1 to STRm, the priority order is higher for the battery strings STR1 to STRm with smaller integrated charge and discharge capacity. In the method of determining the priority order based on the SOH of each battery string STR1 to STRm, the priority order is higher for the battery strings STR1 to STRm with higher SOH among the battery strings STR1 to STRm.

[0047] The system controller 101 determines whether to respond to the device control request from the string controllers C1 to Cm based on the monitored states of the other storage battery strings STR1 to STRm. When the device control request from the string controllers C1 to Cm is permitted, the system controller 101 sends a permission notification of the control request to the string controllers C1 to Cm. The string controllers C1 and Cm that receive the permission notification of the control request for the bypass switch units B1 to Bn perform switch control on the corresponding bypass switch units B1 to Bn. The string controllers C1 to Cm that receive the permission notification of the control request for the power converters PC1 to PCm control the corresponding power converters PC1 to PCm.

[0048] In the case where a device control request is not sent from one of the string controllers C1 to Cm, the system controller 101 may send a device control instruction to one of the string controllers C1 to Cm as needed. When an abnormality in the battery strings STR1 to STRm is detected, the string controllers C1 to Cm may stop the operation of the power converters PC1 to PCm regardless of the presence or absence of a notification of control permission or a control instruction from the system controller 101.

[0049] Here, when the system controller 101 receives a control request for the bypass switch units B1 to Bn from any one of the string controllers C1 to Cm, the system controller 101 stops the operation of the power converters PC1 to PCm (hereinafter referred to as PC′) corresponding to the string controllers C1 to Cm (hereinafter referred to as C′). The operation of the power converter PC′ is stopped, so that the storage battery strings STR1 to STRm (hereinafter referred to as STR′) corresponding to the power converter PC′ are in a no-load state.

[0050] Then, the system controller 101 assigns "0" to the indicated value of the charging and discharging power (or current) of the storage battery string STR' in the no-load state. On the other hand, the system controller 101 assigns a value capable of supplementing the charging and discharging power (or current) of the storage battery string STR' in the no-load state to the indicated value of the charging and discharging power (or current) of one or more other storage battery strings STR1 to STRm.

[0051] At this time, in the process of changing the indicated value of the charging and discharging power (or current) of the battery strings STR′, STR1 to STRm, the system controller 101 gradually and continuously changes the indicated value of the charging and discharging power (or current) of each battery string STR′, STR1 to STRm from the current value to the target value. That is, the system controller 101 gradually and continuously changes the indicated value of the charging and discharging power (or current) of the battery string STR′ in a no-load state (to be bypass-controlled) from the current value to "0". On the other hand, the system controller 101 gradually and continuously changes the indicated value of the charging and discharging power (or current) of one or more battery strings STR1 to STRm in a load state (not to be bypass-controlled) from the current value to the target value. Hereinafter, the process of changing the indicated value of the charging and discharging power (or current) of each battery string STR′, STR1 to STRm will be described.

[0052] Figure 2 1 is a diagram showing the relationship between the charging power instruction value and the elapsed time when the instruction value of the charging power allocated to the storage battery string STR′ to be controlled by bypass and the other storage battery strings STR1 to STRm (hereinafter referred to as the charging power instruction value) is changed. The diagram shows an example in which the charging power instruction value of the storage battery string STR′ to be controlled by bypass is reduced to 0, while the charging power instruction values ​​of the other storage battery strings STR1 to STRm are increased. In this example, the charging power instruction value allocated to the storage battery string STR′ to be controlled by bypass is transferred to the other storage battery strings STR1 to STRm.

[0053] like Figure 2 As shown by the solid line in , the charging power indication value of the storage battery string STR′ to be subjected to bypass control gradually and continuously decreases from the current value to the target value “0” within a predetermined period of time. Figure 2 As shown by the dotted lines in , the charging power instruction values ​​of the other storage battery strings STR1 to STRm are gradually and continuously increased from the current values ​​to the target values ​​within a predetermined period of time.

[0054] Hereinafter, the details of the process of changing the charging power instruction value of the battery strings STR′, STR1 to STRm will be described. Instead of changing the charging power instruction value of the battery strings STR′, STR1 to STRm, the instruction value of the charging current of the battery strings STR′, STR1 to STRm may be changed. In this case, the same process as that to be described below may be performed.

[0055] Figure 3 1 is a flowchart showing a process for changing the charging power instruction value of the battery strings STR′, STR1 to STRm. First, in step S1, the system controller 101 (see Figure 1 ) from the respective string controllers C′, C1 to Cm (see Figure 1 ) obtain each battery string STR′, STR1 to STRm (see Figure 1 )’s status (detection results and estimation results).

[0056] Next, in step S2, the system controller 101 determines whether a bypass control request is received from the string controllers C1 to Cm. If the determination in step S2 is NO, the process proceeds to step S1, and if the determination in step S2 is YES, the process proceeds to step S3.

[0057] In step S3, the system controller 101 selects one or more storage battery strings STR1 to STRm to which the charging power instruction value of the storage battery string STR′ to be subjected to bypass control is transferred. In this step, the storage battery strings STR1 to STRm having the ability to independently withstand the charging power of the storage battery string STR′ to be subjected to bypass control, or the plurality of storage battery strings STR1 to STRm having the ability to jointly withstand the charging power of the storage battery string STR′ to be subjected to bypass control are selected according to the above-mentioned priority order.

[0058] Next, in step S4, the charging power indication value of the one or more storage battery strings STR1 to STRm to which the charging power of the storage battery string STR' to be controlled by bypass is to be transferred is determined. Specifically, the charging power indication value of the one or more storage battery strings STR1 to STRm selected in step S3 is increased by the charging power indication value of the storage battery string STR' to be controlled by bypass.

[0059] Next, the system controller 101 repeatedly performs the loop processing 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 storage battery string STR1 to STRm from the current value by a predetermined amount ΔP1 to the target value. 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′ to be subjected to bypass control from the current value by a predetermined amount ΔP1 to 0.

[0060] 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. The predetermined amount ΔP1 is set to a smaller amount to satisfy the purpose of preventing the charging power from changing drastically. When the difference between the current value and the target value of the charging power instruction value is small, the 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, the predetermined amount ΔP1 may be smaller than the difference between the current value and the target value of the charging power instruction value. When the predetermined amount ΔP1 is smaller than the difference between the current value and the target value of the charging power instruction value, the charging power instruction value is repeatedly updated multiple times.

[0061] Next, in step S6, the system controller 101 waits for a predetermined period of time T1 after sending the charging power instruction value to the string controllers C', C1 to Cm. The predetermined period of time T1 is set in consideration of the period of time required for the string controllers C', C1 to Cm to control the charging power of the storage battery strings STR1 to STRm and the rate of change of the charging power. Here, the rate of change of the charging power is set low to meet the purpose of preventing the charging power from changing sharply.

[0062] Next, in step S7, the system controller 101 determines whether the current charging power instruction value of each storage battery string STR1 to STRm has reached the target charging power instruction value of each storage battery string STR1 to STRm. If the determination in step S7 is no, the process proceeds to step S5, and if the determination in step S7 is yes, the process proceeds to step S8.

[0063] In step S8, the system controller 101 stops the operation of the power converter PC' corresponding to the storage battery string STR' to be bypass-controlled. Therefore, the storage battery string STR' to be bypass-controlled is in a no-load state.

[0064] Next, in step S9, the system controller 101 sends a permission notification of the bypass control request to the string controller C' corresponding to the storage battery string STR' to be bypass controlled. Therefore, the string controller C' performs bypass control on the storage battery string STR' to be bypass controlled.

[0065] Next, in step S10, the system controller 101 determines whether the bypass control request from the string controller C' is released. Step S10 is repeated until the determination in step S10 is yes, and when the determination in step S10 is yes, the process proceeds to step S11.

[0066] In step S11, the system controller 101 assigns 0 to the charging power instruction value of the storage battery string STR' to be bypass controlled. Next, in step S12, the system controller 101 starts the operation of the power converter PC' corresponding to the storage battery string STR' to be bypass controlled. This completes the processing.

[0067] Figure 4 1 is a diagram showing the relationship between the discharge power indication value and the elapsed time when the indication value of the discharge power of the storage battery string STR′ to be controlled by bypass and another one or more storage battery strings STR1 to STRm (hereinafter referred to as the discharge power indication value) is changed. The diagram shows an example in which the discharge power indication value of the storage battery string STR′ to be controlled by bypass decreases to 0, while the discharge power indication values ​​of the other storage battery strings STR1 to STRm increase. In this example, the discharge power indication value allocated to the storage battery string STR′ to be controlled by bypass is transferred to the other storage battery strings STR1 to STRm.

[0068] like Figure 4 As shown by the solid line in , the discharge power indication value of the storage battery string STR′ to be subjected to bypass control gradually and continuously decreases from the current value to the target value “0” within a predetermined period of time. Figure 4 As shown by the dotted lines in , the discharge power instruction values ​​of the other storage battery strings STR1 to STRm gradually and continuously increase from the current value to the target value within a predetermined period of time.

[0069] Hereinafter, the details of the process of changing the discharge power instruction value of the battery strings STR′, STR1 to STRm will be described. Instead of changing the discharge power instruction value of the battery strings STR1 to STRm, the instruction value of the discharge current of the battery strings STR′, STR1 to STRm may be changed. In this case, the same process as that to be described below may be performed.

[0070] Figure 51 is a flowchart showing a process for changing the discharge power instruction value of the battery strings STR′, STR1 to STRm. First, in step S101, the system controller 101 (see Figure 1 ) obtains the latest information (detection results and estimation results) on the status of each battery string STR′, STR1 to STRm from a corresponding one of the string controllers C′, C1 to Cm.

[0071] Next, in step S102, the system controller 101 determines whether a bypass control request is received from the string controllers C1 to Cm. If the determination in step S102 is NO, the process proceeds to step S101, and if the determination in step S102 is YES, the process proceeds to step S103.

[0072] Next, in step S103, the system controller 101 selects one or more storage battery strings STR1 to STRm to which the discharge power of the storage battery string STR′ to be bypass controlled is transferred. In this step, the storage battery strings STR1 to STRm having the ability to independently withstand the discharge power of the storage battery string STR′ to be bypass controlled, or the plurality of storage battery strings STR1 to STRm having the ability to jointly withstand the discharge power of the storage battery string STR′ to be bypass controlled are selected according to the above-mentioned priority order.

[0073] Next, in step S104, the target discharge power indication value of the one or more storage battery strings STR1 to STRm to which the discharge power of the storage battery string STR' to be controlled by bypass is transferred is determined. Specifically, the discharge power indication value of the one or more storage battery strings STR1 to STRm selected in step S103 is increased by the discharge power indication value of the storage battery string STR' to be controlled by bypass.

[0074] Next, the system controller 101 repeatedly executes the loop processing 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 storage battery string STR1 to STRm from the current value by a predetermined amount ΔP2 to the target value. 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′ to be subjected to bypass control from the current value by a predetermined amount ΔP2 to 0.

[0075] 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. The predetermined amount ΔP2 is set to a smaller amount to satisfy the purpose of preventing the discharge power from changing drastically. When the difference between the current value and the target value of the discharge power instruction value is small, the predetermined amount ΔP2 may be equal to the difference between the current value and the target value of the discharge power instruction value. On the other hand, when the difference between the current value and the target value of the discharge power instruction value is relatively large, the predetermined amount ΔP2 may be smaller than the difference between the current value and the target value of the discharge power instruction value. When the predetermined amount ΔP2 is smaller than the difference between the current value and the target value of the discharge power instruction value, the discharge power instruction value is repeatedly updated multiple times.

[0076] Next, in step S106, the system controller 101 waits for a predetermined period of time T1 after sending the discharge power instruction value to the string controllers C′, C1 to Cm. The predetermined period of time T1 is set in consideration of the period of time required for the string controllers C′, C1 to Cm to control the discharge power of the storage battery strings STR′, STR1 to STRm and the rate of change of the discharge power. Here, the rate of change of the discharge power is set low to satisfy the purpose of preventing the discharge power from changing sharply.

[0077] Next, in step S107, the system controller 101 determines whether the current discharge power instruction value of each storage battery string STR1 to STRm has reached the target discharge power instruction value of each storage battery string STR1 to STRm. If the determination in step S107 is no, the process proceeds to step S105, and if the determination in step 107 is yes, the process proceeds to step S108.

[0078] In step S108, the system controller 101 stops the operation of the power converter PC' corresponding to the storage battery string STR' to be bypass-controlled. Therefore, the storage battery string STR' to be bypass-controlled is in a no-load state.

[0079] Next, in step S109, the system controller 101 sends a permission notification of the bypass control request to the string controller C' corresponding to the storage battery string STR' to be bypass controlled. Therefore, the string controller C' performs bypass control on the storage battery string STR' to be bypass controlled.

[0080] Next, in step S110, the system controller 101 determines whether the bypass control request from the string controller C' is released. Step S110 is repeated until the determination in step S110 is yes, and when the determination in step S110 is yes, the process proceeds to step S111.

[0081] In step S111, the system controller 101 assigns 0 to the discharge power instruction value of the storage battery string STR' to be bypass controlled. Next, in step S112, the system controller 101 starts the operation of the power converter PC' corresponding to the storage battery string STR' to be bypass controlled. This completes the processing.

[0082] As described above, in the storage battery control device 100 according to the present embodiment, when the bypass control request is notified from the string controller C′ to the system controller 101, the system controller 101 notifies the string controller C′ of the bypass control permission. At this time, before the system controller 101 notifies the string controller C′ of the bypass control permission, the system controller 101 allocates the instruction value of the charging and discharging power (or current) allocated to the storage battery string STR′ to be subjected to the bypass control to one or more storage battery strings STR1 to STRm not subjected to the bypass control. Then, the system controller 101 stops the operation of the power converter PC′ of the storage battery string STR′ to be subjected to the bypass control.

[0083] Here, when bypass control is performed on the battery string STR′ to be bypass-controlled when the battery string STR′ is in a load state, the charging and discharging power (or current) of the battery string STR′ changes drastically. On the other hand, in the battery control device 100 according to the present embodiment, the charging and discharging power (or current) of the battery string STR′ to be bypass-controlled is distributed to one or more battery strings STR1 to STRm, and the bypass control of the battery string STR′ is performed after the battery string STR′ is in a no-load state. Therefore, when the bypass control is performed, the target charging and discharging power (or current) of the power storage system 1 can be maintained.

[0084] Here, in the storage battery control device 100 according to the present embodiment, the system controller 101 allocates the indicated value of the charging and discharging power (or current) allocated to the storage battery string STR′ to be subjected to the bypass control to one or more storage battery strings STR1 to STRm that are not subjected to the bypass control. At this time, the system controller 101 repeatedly performs a process of changing the indicated value of the charging and discharging power (or current) of the storage battery strings STR′, STR1 to STRm by predetermined amounts ΔP1 and ΔP2 toward the indicated value of the target charging and discharging power (or current) until the indicated value reaches the target value. Here, the predetermined amounts ΔP1 and ΔP2 are smaller than the difference between the target value and the current value of the indicated value of the charging and discharging power (or current). Therefore, when the indicated value of the charging and discharging power (or current) of the storage battery strings STR′, STR1 to STRm changes from the current value to the target value, it is possible to prevent the charging and discharging power (or current) of the storage battery strings STR′, STR1 to STRm from changing sharply, and maintain the target charging and discharging power (or current) of the power storage system 1.

[0085] Although the present invention has been described above based on the above embodiment, the present invention is not limited to the above embodiment, and modifications may be made without departing from the gist of the present invention, or known or well-known technologies may be appropriately combined.

[0086] For example, in the above-described embodiment, the indicated values ​​of the charging and discharging power (or current) of the battery strings STR′, STR1 to STRm are gradually and continuously changed to the target value by a predetermined amount ΔP1 or a predetermined amount ΔP2 over time. However, for example, when the change in the charging and discharging power (or current) of the battery strings STR′, STR1 to STRm has little influence on the charging and discharging power (or current) of the power storage system 1, the indicated values ​​of the charging and discharging power (or current) of the battery strings STR′ and STR1 to STRm may all be changed at the same time.

[0087] In the above embodiment, the system controller 101 sends the indication value of the charging and discharging power (or current) to the string controllers C1 to Cm. However, a controller in which the system controller 101 and the string controllers C1 to Cm are integrated may also set the indication value of the charging and discharging power (or current) of each battery string STR1 to STRm.

[0088] Here, the features of the embodiments of the battery control device, power storage system, and battery control method according to the present invention described above will be briefly summarized and listed in the following [1] to [4]. [1]

[0090] A storage battery control device (100) for controlling a power storage system (1) including a plurality of storage battery strings (STR1 to STRm) connected in parallel to each other, the storage battery strings (STR1 to STRn) including a plurality of storage batteries (M1 to Mn) connected in series, a bypass circuit (B1 to Bn) configured to switch the plurality of storage batteries (M1 to Mn) between a connection state and a bypass state, and a power converter (PC1 to PCm) configured to convert input and output power of the storage battery strings (STR1 to STRm).

[0091] The battery control device (100) distributes the indicated values ​​of the charging or discharging power or current of the plurality of battery strings (STR1 to STRm), controls the bypass circuits (B1 to Bn), and controls the power converters (PC1 to PCm), and

[0092] The battery control device (100) allocates the indication value allocated to the battery strings (STR1 to STRm) to be controlled by the bypass circuit (B1 to Bn) to one or more of the battery strings (STR1 to STRm) not controlled by the bypass circuit (B1 to Bn) before controlling the bypass circuit (B1 to Bn), and stops the power converters (PC1 to PCm) of the battery strings (STR1 to STRm) to be controlled by the bypass circuit (B1 to Bn). [2]

[0094] According to the battery control device (100) described in [1],

[0095] When the indication value assigned to the battery strings (STR1 to STRm) to be controlled by the bypass circuit (B1 to Bn) is assigned to one or more of the battery strings not controlled by the bypass circuit (B1 to Bn), the process of increasing the indication value toward the target value by an amount of change that is less than the difference between the target value and the current value is repeatedly performed until the indication value reaches the target value. [3]

[0097] A power storage system (1) comprises a plurality of battery strings (STR1 to STRm) connected in parallel with each other, and a battery control device (100) configured to control the battery strings (STR1 to STRn), wherein the battery strings (STR1 to STRm) comprise a plurality of batteries (M1 to Mn) connected in series, a bypass circuit (B1 to Bn) configured to switch the plurality of batteries (M1 to Mn) between a connection state and a bypass state, and a power converter (PC1 to PCm) configured to convert input and output power of the battery strings (STR1 to STRm).

[0098] Wherein, the battery control device (100)

[0099] allocating the indicated values ​​of the charging or discharging power or current of the plurality of battery strings (STR1 to STRm), controlling the bypass circuits (B1 to Bn), and controlling the power converters (PC1 to PCm), and

[0100] The indication value assigned to the battery strings (STR1 to STRm) to be controlled by the bypass control (B1 to Bn) is assigned to one or more of the battery strings not controlled by the bypass, and before controlling the bypass circuit (B1 to Bn), the power converters (PC1 to PCm) of the battery strings (STR1 to STRm) controlled by the bypass circuit (B1 to Bn) are stopped. [4]

[0102] A battery control method is performed by a battery control device (100) for controlling a power storage system (1) including a plurality of battery strings (STR1 to STRm) connected in parallel to each other, wherein the battery strings (STR1 to STRm) include a plurality of batteries (M1 to Mn) connected in series, a bypass circuit (B1 to Bn) configured to switch the plurality of batteries (M1 to Mn) between a connection state and a bypass state, and a power converter (PC1 to PCm) configured to convert input and output power of the battery strings (STR1 to STRm), the battery control method comprising:

[0103] allocating the indicated value of the charging or discharging power or current of the plurality of battery strings (STR1 to STRm), controlling the bypass circuits (B1 to Bn), and controlling the power converters (PC1 to PCm), and

[0104] Before controlling the bypass circuit (B1 to Bn), the indication value assigned to the battery strings (STR1 to STRm) to be controlled by the bypass circuit (B1 to Bn) is assigned to one or more of the battery strings (STR1 to STRm) not controlled by the bypass circuit (B1 to Bn), and the power converters (PC1 to PCm) of the battery strings (STR1 to STRm) to be controlled by the bypass circuit (B1 to Bn) are stopped.

[0105] While the invention has been described in detail and with reference to specific embodiments, it will be apparent to one skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0106] This application is based on the Japanese patent application filed on October 4, 2022 (Japanese patent application No. 2022-160011), the contents of which are incorporated herein by reference.

[0107] Industrial Applicability

[0108] According to the present invention, a battery control device, a power storage system, and a battery control method can be provided, which can maintain the target charging and discharging power (or current) of the power storage system when bypass control is performed in a power storage system in which a plurality of battery strings are connected in parallel and each battery string is provided with a bypass circuit. The present invention having such an effect is useful for a battery control device, a power storage system, and a battery control method.

[0109] Reference Symbols List

[0110] 1: Power storage system

[0111] 100: Battery control device

[0112] B1 to Bn: Bypass switch unit (bypass circuit)

[0113] M1 to Mn: Battery modules (batteries)

[0114] PC1 to PCm, PC′: Power converter

[0115] STR1 to STRm, STR′: battery string

[0116] ΔP1: Predetermined amount (small change)

[0117] 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 string including a plurality of batteries connected in series, a bypass circuit configured to switch the plurality of batteries between a connection state and a bypass state, and a power converter configured to convert input and output power of the battery string, in, The battery control device distributes the indicated values ​​of the charging or discharging power or current of the plurality of battery strings, controls the bypass circuit, and controls the power converter, and Before controlling the bypass circuit, the battery control device allocates the indication value allocated to the battery string to be controlled by the bypass circuit to one or more of the battery strings not controlled by the bypass circuit, and stops the power converter of the battery string to be controlled by the bypass circuit.

2. The battery control device according to claim 1, wherein: When the indication value assigned to the battery string to be controlled by the bypass circuit is assigned to one or more of the battery strings not controlled by the bypass circuit, a process of increasing the indication value toward a target value by an amount of change that is less than a difference between the target value and a current value is repeatedly performed until the indication value reaches the target value.

3. A power storage system comprising: A plurality of battery strings are connected in parallel with each other; as well as a battery control device configured to control the battery string, Wherein, the battery string comprises: Multiple batteries connected in series, a bypass circuit configured to switch the plurality of batteries between a connected state and a bypass state, and a power converter configured to convert input and output power of the battery string, wherein the battery control device distributes the indicated values ​​of charging or discharging power or current of a plurality of the battery strings, controls the bypass circuit, and controls the power converter, and Wherein, before controlling the bypass circuit, the battery control device allocates the indication value allocated to the battery string to be controlled by the bypass circuit to one or more of the battery strings not controlled by the bypass circuit, and stops the power converter of the battery string controlled by the bypass circuit.

4. A battery control method, executed by a battery control device for controlling a power storage system including a plurality of battery strings connected in parallel to each other, the battery string including a plurality of batteries connected in series, a bypass circuit configured to switch the plurality of batteries between a connection state and a bypass state, and a power converter configured to convert input and output power of the battery string, the battery control method comprising: allocating the indicated value of the charging or discharging power or current of the plurality of battery strings, controlling the bypass circuit, and controlling the power converter, and Before controlling the bypass circuit, the indication value assigned to the battery strings to be controlled by the bypass circuit is assigned to one or more of the battery strings not controlled by the bypass circuit, and the power converters of the battery strings controlled by the bypass circuit are stopped.

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