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

Abstract

To continuously supply power driven by a system of a power supply destination in a power storage system composed of a plurality of storage batteries connected in series.SOLUTION: A storage battery control device controls a power storage system including a plurality of storage battery modules connected in series and a bypass circuit bypassing each storage battery module. The storage battery control device performs first processing for discharging each storage battery module while switching the storage battery modules bypassed by a bypass circuit so that difference of a remaining discharging amount of the plurality of storage battery modules until discharge completion is decreased, and second processing for completing discharge of the plurality of storage battery modules after the first processing, and performs the first processing until OCV of each storage battery module falls below a threshold set for every storage battery module, and performs the first processing so that output possible power of the discharged storage battery module does not drop below minimum required power of the power supply destination.SELECTED DRAWING: Figure 2

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] A battery control unit that controls the discharge of a power storage system in which multiple storage batteries are connected in series is known that selects a storage battery that has reached a discharge end state, bypasses that storage battery, and discharges the other storage batteries (see, for example, Patent Document 1). In the battery control unit described in Patent Document 1, storage batteries whose dischargeable capacity has reached a predetermined value are switched to a bypass state in order, and after the dischargeable capacity of all storage batteries has reached the predetermined value, all storage batteries are switched to a discharge state, and thereafter, storage batteries whose dischargeable capacity has reached a discharge end state are switched to a bypass state in order. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-1006 Summary of the Invention [Problem to be solved by the invention]

[0004] In the system described in Patent Document 1, a process is performed to align the dischargeable capacities of all storage batteries to a predetermined value, but even when this process is being performed, it is necessary to continuously supply power to operate the systems to which the power is supplied, and measures are therefore required.

[0005] 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 continuously supply power to operate a system to which the power is supplied in a battery storage system in which multiple storage batteries are connected in series. [Means for solving the problem]

[0006] The battery control device of the present invention is a battery control device that controls an electricity storage system including a plurality of storage batteries connected in series and a bypass circuit that bypasses each of the storage batteries, and executes a first process of discharging each of the storage batteries while switching the storage batteries to be bypassed by the bypass circuit so as to reduce a difference in remaining discharge amounts until the discharge of the plurality of storage batteries is completed, and executes a second process of completing the discharge of the plurality of storage batteries after the first process, and executes the first process while the OCV or SOC of each storage battery is equal to or lower than the OCV or SOC set for each storage battery. No. 1 The first process is executed until the output power of the storage battery to be discharged falls below a threshold value, and the first process is executed so that the output power of the storage battery to be discharged does not fall below the minimum power required by the power supply destination. The second process is executed until the output power of the storage battery to be discharged falls below the minimum power required for the power supply destination, or until the OCV or SOC of each storage battery falls below a second threshold value of OCV or SOC set for each storage battery, and the state of each storage battery is estimated before the start of the first process, and based on the estimation result, it is determined whether or not the first threshold value needs to be updated. do. The battery control device of the present invention is a battery control device that controls an electricity storage system including a plurality of storage batteries connected in series and a bypass circuit that bypasses each of the storage batteries, and executes a first process of discharging each of the storage batteries while switching the storage batteries to be bypassed by the bypass circuit so as to reduce a difference in remaining discharge amounts until the discharge of the plurality of storage batteries is completed, and a second process of completing the discharge of the plurality of storage batteries after the first process, executes the first process until the OCV or SOC of each storage battery falls below a first threshold value of OCV or SOC set for each storage battery, executes the first process so that the outputtable power of the storage battery to be discharged does not fall below the minimum power required for the power supply destination, and executes the second process of discharging. The process is executed until the output power of the storage batteries falls below the minimum power required by the power supply destination, or until the OCV or SOC of each storage battery falls below a second threshold value of OCV or SOC set for each storage battery, and the first process is executed in accordance with a predetermined discharge bypass schedule, which determines for each period a combination of two or more storage batteries to be discharged and a storage battery to be bypassed so that the difference in the remaining discharge amount until the completion of discharging of the multiple storage batteries is reduced while the output power of the multiple storage batteries is maintained above the minimum power required by the power supply destination, and before starting the first process, the state of each storage battery is estimated, and based on the estimation result, it is determined whether or not the discharge bypass schedule needs to be updated.

[0007] The power storage system of the present invention includes a plurality of storage batteries connected in series, a bypass circuit for bypassing each of the storage batteries, and a storage battery control device for controlling the bypass circuit, and the storage battery control device executes a first process for discharging each of the storage batteries while switching the storage batteries to be bypassed by the bypass circuit so as to reduce a difference in remaining discharge amounts until the discharge of the plurality of storage batteries is completed, and a second process for completing the discharge of the plurality of storage batteries after the first process, and the first process is performed while the OCV or SOC of each storage battery is set to an OCV or SOC set for each storage battery. No. 1 The first process is executed until the output power of the storage battery to be discharged falls below a threshold value, and the first process is executed so that the output power of the storage battery to be discharged does not fall below the minimum power required by the power supply destination. The second process is executed until the output power of the storage battery to be discharged falls below the minimum power required for the power supply destination, or until the OCV or SOC of each storage battery falls below a second threshold value of OCV or SOC set for each storage battery, and the state of each storage battery is estimated before the start of the first process, and based on the estimation result, it is determined whether or not the first threshold value needs to be updated. do. The power storage system of the present invention includes a plurality of storage batteries connected in series, a bypass circuit for bypassing each of the storage batteries, and a storage battery control device for controlling the bypass circuit, wherein the storage battery control device executes a first process for discharging each of the storage batteries while switching the storage batteries to be bypassed by the bypass circuit so as to reduce a difference in remaining discharge amounts until the discharge of the plurality of storage batteries is completed, and a second process for completing the discharge of the plurality of storage batteries after the first process, the first process being executed until the OCV or SOC of each storage battery falls below a first threshold value of OCV or SOC set for each storage battery, the first process being executed so that the outputtable power of the storage battery to be discharged does not fall below the minimum power required for a power supply destination, and the second process being executed so as to control the discharge of the plurality of storage batteries while switching the storage batteries to be bypassed by the bypass circuit so as to reduce a difference in remaining discharge amounts until the discharge of the plurality of storage batteries is completed. the first process is executed until the available output power of the storage batteries to be discharged falls below the minimum power required by the power supply destination, or until the OCV or SOC of each storage battery falls below a second threshold value of OCV or SOC set for each storage battery, and the first process is executed in accordance with a predetermined discharge bypass schedule, the discharge bypass schedule determining for each period a combination of two or more storage batteries to be discharged and a storage battery to be bypassed so that a difference in remaining discharge amounts until the completion of discharging of the multiple storage batteries is reduced while the available output power of the multiple storage batteries is maintained at or above the minimum power required by the power supply destination, and a state of each storage battery is estimated before starting the first process, and a determination is made as to whether or not the discharge bypass schedule needs to be updated based on the estimation result.

[0008] The battery control method of the present invention is a battery control method executed using a battery control device that controls a power storage system including a plurality of storage batteries connected in series and a bypass circuit that bypasses each of the storage batteries, the method including: a first step of discharging each of the storage batteries while switching the storage batteries to be bypassed by the bypass circuit so as to reduce a difference in remaining discharge amounts until the discharge of the plurality of storage batteries is completed; and a second step of completing the discharge of the plurality of storage batteries after the first step, the first step being executed until the OCV or SOC of each of the storage batteries falls below a first threshold value of OCV or SOC set for each storage battery; the first step being executed so that the available output power of the storage battery to be discharged does not fall below the minimum required power of the power supply destination; and the second step being executed until the available output power of the storage battery to be discharged falls below the minimum required power of the power supply destination or until the OCV or SOC of each of the storage batteries falls below a second threshold value of OCV or SOC set for each storage battery; and estimating a state of each storage battery before starting the first step, and determining whether or not the first threshold value needs to be updated based on the estimation result. The storage battery control method of the present invention is a storage battery control method executed by a storage battery control device that controls a power storage system including a plurality of storage batteries connected in series and a bypass circuit that bypasses each of the storage batteries, the method including: executing a first step of discharging each of the storage batteries while switching the storage batteries to be bypassed by the bypass circuit so as to reduce a difference in remaining discharge amounts until the completion of discharge of the plurality of storage batteries; and executing a second step of completing discharge of the plurality of storage batteries after the first step; executing the first step until the OCV or SOC of each of the storage batteries falls below a first threshold value of OCV or SOC set for each storage battery; executing the first step so that the available output power of the storage battery to be discharged does not fall below a minimum required power of a power supply destination; and executing the second step until the available output power of the storage battery to be discharged falls below the minimum required power of the power supply destination or until the OCV or SOC of each of the storage batteries falls below a second threshold value of OCV or SOC set for each storage battery; procedurea discharge bypass schedule that determines a combination of two or more storage batteries to be discharged and a storage battery to be bypassed for each period so that a difference in remaining discharge amount until the completion of discharge of the plurality of storage batteries is reduced in a state where the outputtable power of the plurality of storage batteries is maintained at or above the minimum power required for the power supply destination; procedure Before the start of the discharge bypass schedule, the state of each storage battery is estimated, and based on the estimation result, it is determined whether or not the discharge bypass schedule needs to be updated. Effect of the Invention

[0009] According to the present invention, in a power storage system in which a plurality of storage batteries are connected in series, it is possible to continuously supply power to operate a system that is a power supply destination. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a 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 flowchart showing a process performed by the battery control device shown in FIG. 1 in the discharging mode. [Diagram 3] FIG. 3 is a flowchart showing another embodiment of the process performed by the battery control device shown in FIG. 1 in the discharging mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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.

[0012] 1 is a 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 a battery string 10, a bypass circuit 20, a charge / discharge circuit 30, and the battery control device 100.

[0013] The storage battery string 10 is a stationary or vehicle-mounted power source including n (n is an integer of 2 or more) storage battery modules M1-Mn connected in series. Although not particularly limited, the storage battery string 10 of this embodiment is a regenerated second-hand storage battery, and the deterioration levels of the storage battery modules M1-Mn differ from one another. The storage battery modules M1-Mn are, for example, secondary batteries such as lithium ion batteries and lithium ion capacitors, and are charged by receiving power from an external system ES via a charge / discharge circuit 30, and the charged power is discharged via the charge / discharge circuit 30 to supply power to the external system ES.

[0014] The external system ES includes loads and generators. 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.

[0015] The battery string 10 may include n storage battery cells or storage battery packs connected in series, instead of the n storage battery modules M1 to Mn connected in series. The power storage system 1 may include a bypass circuit that bypasses each storage battery cell or each storage battery pack.

[0016] The battery string 10 includes a plurality of voltage measurement units 12, a current measurement unit 13, and a battery temperature measurement unit 14. The voltage measurement units 12 are connected between the positive and negative terminals of each of the battery modules M1 to Mn. The voltage measurement units 12 measure the inter-terminal voltages of each of the battery modules M1 to Mn.

[0017] The current measurement unit 13 is provided in a current path of the storage battery string 10. The current measurement unit 13 measures the charge / discharge current of the storage battery string 10. The storage battery string 10 is also provided with a battery temperature measurement unit 14. The battery temperature measurement unit 14 measures the battery temperature of the storage battery string 10.

[0018] The bypass circuit 20 includes n bypass circuits B1-Bn (n is an integer of 2 or more) provided for each of the storage battery modules M1-Mn. Each of the bypass circuits B1-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-Mn. The switch S1 is provided on the bypass line BL. The switch S1 is, for example, a mechanical switch. The switch S2 is provided between the positive electrode of each of the storage battery modules M1-Mn and one end of the bypass line BL. The switch S2 is, for example, a semiconductor switch or a relay.

[0019] The starting battery module M1 and the ending battery module Mn are connected to an external system ES via a charge / discharge circuit 30. When the switch S1 is open and the switch S2 is closed in all of the bypass circuits B1-Bn, all of the storage battery modules M1-Mn are connected in series to the charge / discharge circuit 30 and the external system ES. On the other hand, when the switch S2 is open and the switch S1 is closed in any of the bypass circuits B1-Bn, the storage battery module M1-Mn corresponding to that bypass circuit B1-Bn is bypassed.

[0020] The battery control device 100 is connected to the battery string 10, the bypass circuit 20, and the charge / discharge circuit 30, and monitors and controls each of the battery modules M1-Mn, controls switching of each of the bypass circuits B1-Bn, and controls charging and discharging by the charge / discharge circuit 30. In particular, when a discharge mode is executed, the battery control device 100 of this embodiment executes a first process for equalizing the remaining discharge amounts (hereinafter referred to as remaining discharge capacities) until the completion of discharging of all of the battery modules M1-Mn, and a second process for discharging all of the battery modules M1-Mn after the first process. In the first process, the battery control device 100 discharges each of the battery modules M1-Mn while switching between the bypass circuits B1-Bn according to a discharge bypass schedule generated in advance, thereby equalizing the remaining discharge capacities of all of the battery modules M1-Mn.

[0021] The discharge bypass schedule includes schedule information and voltage information. The schedule information is information that sets a combination of the storage battery modules M1 to Mn to be discharged and the storage battery modules M1 to Mn to be bypassed in a time series. For example, this schedule information is information that in a first period, the storage battery modules M1 to M6 are discharged and the other storage battery modules M7 to Mn are bypassed, and in a second period, the storage battery modules M5 to Mn are discharged and the other storage battery modules M1 to M4 are bypassed. On the other hand, the voltage information is information on the threshold of the OCV (Open Circuit Voltage) of each storage battery module M1 to Mn, which is a threshold when the first process is ended. The threshold of the OCV of each storage battery module M1 to Mn as the voltage information is set for the purpose of making the remaining discharge capacity of the multiple storage battery modules M1 to Mn uniform at the end of the first process.

[0022] Here, the discharge bypass schedule is set so that the available output power of the storage battery string 10 during execution of the first process is continuously maintained at or above the minimum power required by the system to which the power is supplied. That is, a combination of the storage battery modules M1-Mn to be discharged and the storage battery modules M1-Mn to be bypassed is set so that the available output power of the storage battery string 10 does not fall below the minimum power required by the system to which the power is supplied during each period during which the first process is executed.

[0023] The battery control device 100 updates the discharge bypass schedule when a predetermined condition is satisfied at the start of the discharge mode. Examples of the predetermined condition include the following (1) to (6). When such a condition is satisfied, it is expected that the variation in the remaining discharge capacity of the storage battery modules M1 to Mn will become large. In addition, the relative relationship of the remaining discharge capacity among the storage battery modules M1 to Mn also changes each time. Therefore, the battery control device 100 generates a new discharge bypass schedule when the predetermined condition is satisfied at the start of the discharge mode.

[0024] The battery control device 100 holds, as information on the battery modules M1-Mn, an OCV-SOC curve showing the relationship between the OCV and SOC (State of Charge) of the battery modules M1-Mn, the initial capacity of the battery modules M1-Mn, and the SOH (State of Health). The discharge amount of the battery modules M1-Mn differs depending on the degree of deterioration and temperature. Therefore, the battery control device 100 calculates and sets the above-mentioned OCV threshold value based on the information on the battery modules M1-Mn, temperature information, an estimated OCV value, etc.

[0025] The SOC can be estimated using various known methods such as a current integration method, a method of calculating from the OCV (voltage method), a method combining the current integration method and the voltage method, etc. The SOC can also be estimated using various known methods that estimate the SOC using the change in SOC over time and / or the increase in internal resistance over time. Examples of methods for estimating the SOH include a method using a charge / discharge test, a method using a current integration method, a method using an open circuit voltage measurement, a method using a terminal voltage measurement, a model-based method (all of which use the change in SOC over time), a method using AC impedance measurement, a method using an adaptive digital filter based on a model, a method using linear regression (the slope of the straight line of the IV characteristics) from the IV characteristics (current-voltage characteristics), and a method using a step response (all of which use the increase in internal resistance over time to estimate the SOC).

[0026] The remaining discharge capacity can be calculated by the following formula (1). Remaining discharge capacity [Ah] = CC × SOC / 100 … (1) Here, CC is the current battery capacity of each of the storage battery modules M1 to Mn, and can be calculated by the following formula (2). CC[Ah]=C0×SOH / 100 …(2) Here, C0 is the initial capacity (Ah) of each of the storage battery modules M1 to Mn.

[0027] Fig. 2 is a flowchart showing the process during the discharge mode by the storage battery control device 100 shown in Fig. 1. As shown in this flowchart, when the power storage system 1 shown in Fig. 1 enters the discharge mode, the process is started.

[0028] First, in step S1, the battery control device 100 turns off all the switches S1 and S2 of the battery string 10 shown in Fig. 1. Next, in step S2, the battery control device 100 determines whether or not a predetermined condition that requires updating of the discharge bypass schedule is satisfied. The predetermined condition is that at least one of the following conditions (1) to (6) is satisfied. (1) The device has switched to discharge mode. (2) The charging time before the discharge mode is equal to or longer than a specified time. (3) The charging power capacity before the discharge mode is equal to or greater than a specified capacity. (4) The temperature change from the time the discharge bypass schedule was last created is equal to or greater than the specified temperature. (5) The cumulative number of interruptions to charging during discharging has exceeded a certain number. (6) Any other changes in the operating state of the energy storage system, such as changes in the average discharge power or the remaining discharge capacity at the end of the second process.

[0029] If the determination in step S2 is affirmative, the process proceeds to step S20. In step S20, the battery control device 100 calculates the remaining discharge capacity of the battery modules M1 to Mn based on the initial capacity, OCV, SOC, and SOH. Next, in step S3, the battery control device 100 generates a discharge bypass schedule according to the remaining discharge capacity of the battery modules M1 to Mn calculated in step S20. At this time, the battery control device 100 sets a combination of the battery modules M1 to Mn to be discharged and the battery modules M1 to Mn to be bypassed so that the outputtable power of the battery string 10 is continuously maintained at or above the minimum power required for the system to which the power is supplied. In addition, the battery control device 100 sets the OCV threshold of the battery modules M1 to Mn, which is the threshold for ending the first process, based on the battery information held for each of the battery modules M1 to Mn, such as the OCV-SOC curves of the battery modules M1 to Mn. The process proceeds from step S3 to step S4.

[0030] On the other hand, if a negative determination is made in step S2, the process proceeds to step S4 without updating the discharge bypass schedule. In this case, the processes of steps S5 to S8 are executed according to the discharge bypass schedule used in the previous discharge mode.

[0031] In step S4, the battery control device 100 turns on all the switches S2 of the battery string 10 to connect all the battery modules M1 to Mn in series. Next, in step S5, the battery control device 100 starts a first process. In the first process, the battery control device 100 discharges each of the battery modules M1 to Mn while switching each of the bypass circuits B1 to Bn in accordance with a discharge bypass schedule.

[0032] Next, in step S6, the battery control device 100 compares the OCV of the battery modules M1-Mn with the OCV threshold value set in step S3 or when the discharge mode was executed before the last time, and determines whether or not there is any battery module M1-Mn whose OCV has fallen below the threshold value. Step S6 is repeated until a positive determination is made, and if a positive determination is made in step S6, the process proceeds to step S7.

[0033] In step S7, the battery control device 100 determines whether or not all of the battery modules M1 to Mn of the battery string 10 are bypassed by the bypass circuits B1 to Bn. If a positive determination is made in step S7, the process proceeds to step S9, and if a negative determination is made in step S7, the process proceeds to step S8.

[0034] In step S8, the battery control device 100 bypasses the battery modules M1 to Mn, for which it has been determined in step S6 that the OCV has fallen to or below the threshold, by the corresponding bypass circuits B1 to Bn. The process returns from step S8 to step S6.

[0035] On the other hand, in step S9, the battery control device 100 turns on all the switches S2 of the battery string 10 to connect all the battery modules M1 to Mn in series. That is, after the first process, the battery control device 100 executes a second process in which all the battery modules M1 to Mn are discharged.

[0036] Next, in step S10, the battery control device 100 determines whether the available output power of the battery string 10 has fallen to or below the minimum power required by the system to which the power is supplied. Step S10 is repeated until a positive determination is made, and if a positive determination is made in step S10, the process proceeds to step S11.

[0037] In step S11, the battery control device 100 turns off all of the switches S1 and S2 of the battery string 10. This ends the process in the discharge mode.

[0038] As described above, the battery control device 100 of this embodiment first executes the first process when the discharging mode is executed, and then executes the second process after the first process. In the first process, the battery control device 100 discharges each of the battery modules M1 to Mn while switching the battery modules M1 to Mn to be bypassed by the bypass circuits B1 to Bn so that the difference in the remaining discharge capacity of the battery modules M1 to Mn is reduced. After that, in the second process, the battery control device 100 completes the discharge of the battery modules M1 to Mn. This makes it possible to uniformly maintain the remaining discharge capacity of the battery modules M1 to Mn from the start of the second process until the later stage of the second process. Therefore, it becomes possible to discharge more battery modules M1 to Mn without bypassing them until the later stage of the discharging mode when the voltage of each of the battery modules M1 to Mn decreases.

[0039] Here, the battery control device 100 executes the first process until the OCV of each of the battery modules M1-Mn falls below the OCV threshold set for each of the battery modules M1-Mn. By setting the OCV threshold for each of the battery modules M1-Mn according to the deterioration state, temperature, etc. of each of the battery modules M1-Mn, it is possible to reduce the difference in remaining discharge capacity among the multiple battery modules M1-Mn at the end of the first process.

[0040] Furthermore, the battery control device 100 executes the first process so that the available output power of the storage battery modules M1-Mn to be discharged does not fall below the minimum power required by the power supply destination. This makes it possible to continuously supply power to drive the system of the power supply destination from the start of the first process until the later stage of the discharging mode when the voltage of each of the storage battery modules M1-Mn decreases.

[0041] The battery control device 100 executes the first process according to a discharge bypass schedule that determines a combination of two or more battery modules M1-Mn to be discharged and the battery modules M1-Mn to be bypassed for each period. This discharge bypass schedule is set so that the difference in remaining discharge capacity of the battery modules M1-Mn decreases while the available output power of the battery modules M1-Mn is maintained at or above the minimum required power of the system to which the power is supplied. Here, it is possible to sequentially bypass the battery modules M1-Mn whose OCV has decreased to a threshold value. In this case, the number of battery modules M1-Mn to be discharged decreases as the first process approaches a later stage, and the available output power of the battery string 10 decreases. In contrast, in this embodiment, more battery modules M1-Mn can be discharged without being bypassed until the later stage of the first process, and the available output power of the battery string 10 can be maintained at or above the minimum required power of the system to which the power is supplied.

[0042] Furthermore, the battery control device 100 estimates the state of each of the storage battery modules M1-Mn before starting the first process, and determines whether or not it is necessary to update the OCV threshold of each of the storage battery modules M1-Mn based on the estimation result. This makes it possible to set the OCV threshold of each of the storage battery modules M1-Mn for each of the storage battery modules M1-Mn depending on the deterioration state, temperature, etc. of each of the storage battery modules M1-Mn. This makes it possible to reduce differences in remaining discharge capacity among the multiple storage battery modules M1-Mn at the end of the first process.

[0043] Fig. 3 is a flowchart showing another embodiment of the process during the discharge mode by the battery control device 100 shown in Fig. 1. As shown in this flowchart, when the power storage system 1 shown in Fig. 1 enters the discharge mode, the process is started.

[0044] First, in step S101, the battery control device 100 turns off all of the switches S1 and S2 of the battery string 10. Next, in step S102, the battery control device 100 calculates the remaining discharge capacity of the battery modules M1 to Mn based on the initial capacity, OCV, SOC, and SOH.

[0045] Next, in step S103, the battery control device 100 generates a discharge bypass schedule according to the remaining discharge capacity of the battery modules M1-Mn calculated in step S102. At this time, the battery control device 100 sets a combination of the battery modules M1-Mn to be discharged and the battery modules M1-Mn to be bypassed so that the possible output power of the battery string 10 is continuously equal to or greater than the minimum power required for the system to which the power is supplied.

[0046] The battery control device 100 also sets the SOC thresholds of the battery modules M1 to Mn, which are to be the thresholds for ending the first process, based on the battery information held for each of the battery modules M1 to Mn, such as the OCV-SOC curves of the battery modules M1 to Mn. The process proceeds from step S103 to step S104.

[0047] In step S104, the battery control device 100 turns on all the switches S2 of the battery string 10 to connect all the battery modules M1 to Mn in series. Next, in step S105, the battery control device 100 starts a first process. In the first process, the battery control device 100 discharges each of the battery modules M1 to Mn while switching each of the bypass circuits B1 to Bn in accordance with a discharge bypass schedule.

[0048] Next, in step S106, the battery control device 100 compares the SOC of the battery modules M1-Mn with the SOC threshold set in step S103, and determines whether or not there is any battery module M1-Mn whose SOC has fallen to or below the threshold. Step S106 is repeated until a positive determination is made, and if a positive determination is made in step S106, the process proceeds to step S107.

[0049] In step S107, the battery control device 100 determines whether or not all of the battery modules M1 to Mn of the battery string 10 are bypassed by the bypass circuits B1 to Bn. If a positive determination is made in step S107, the process proceeds to step S109, and if a negative determination is made in step S107, the process proceeds to step S108.

[0050] In step S108, the battery control device 100 causes the corresponding bypass circuits B1 to Bn to bypass the battery modules M1 to Mn whose SOC has been determined to have dropped to or below the threshold in step S106. The process returns from step S108 to step S106.

[0051] On the other hand, in step S109, the battery control device 100 turns on all the switches S2 of the battery string 10 to connect all the battery modules M1 to Mn in series. That is, after the first process, the battery control device 100 executes a second process in which all the battery modules M1 to Mn are discharged.

[0052] Next, in step S110, the battery control device 100 determines whether the available output power of the battery string 10 has fallen to or below the minimum power required by the system to which the power is supplied. Step S110 is repeated until a positive determination is made, and if a positive determination is made in step S110, the process proceeds to step S111.

[0053] In step S111, the battery control device 100 turns off all of the switches S1 and S2 of the battery string 10. This ends the process in the discharge mode.

[0054] As described above, the battery control device 100 of this embodiment executes the first process until the SOC of each of the battery modules M1-Mn falls below the SOC threshold set for each of the battery modules M1-Mn. By setting the SOC threshold for each of the battery modules M1-Mn according to the deterioration state, temperature, etc. of each of the battery modules M1-Mn, it is possible to reduce the difference in remaining discharge capacity among the multiple battery modules M1-Mn at the end of the first process.

[0055] The present invention has been described above based on the above embodiment, but the present invention is not limited to the above embodiment, and modifications may be made without departing from the spirit of the present invention, and known or well-known technologies may be appropriately combined.

[0056] For example, in the above embodiment, the battery control device 100 executes the first process according to a discharge bypass schedule in which a combination of the storage battery modules M1-Mn to be discharged and the storage battery modules M1-Mn to be bypassed is set for each period. However, in the first process, the battery control device 100 may reduce the difference in remaining discharge capacity among the multiple storage battery modules M1-Mn by, for example, sequentially bypassing the storage battery modules M1-Mn whose OCV or SOC has fallen to a threshold value.

[0057] From the viewpoint of eventually using up the remaining discharge capacities of all the storage battery modules M1-Mn and aligning the timing of completion of discharge of all the storage battery modules M1-Mn, it is preferable to align the remaining charge capacities of the multiple storage battery modules M1-Mn in the first process. However, it is not essential to align the remaining discharge capacities of the multiple storage battery modules M1-Mn in the first process, and it is sufficient if the difference in the remaining discharge capacities of the multiple storage battery modules M1-Mn is reduced in the first process.

[0058] In the above embodiment, the discharge completion threshold is set to a uniform value, and the first process is executed so that the difference in the remaining discharge capacity until the discharge completion of the plurality of storage battery modules M1 to Mn is reduced in all of the storage battery modules M1 to Mn at the end of the second process. However, the discharge completion threshold may be set for each storage battery module M1 to Mn, and the first process may be executed so that the difference in the remaining discharge capacity until the discharge completion of the plurality of storage battery modules M1 to Mn is reduced in all of the storage battery modules M1 to Mn at the end of the second process. That is, the discharge completion threshold may be set for each storage battery module M1 to Mn according to the deterioration state of the storage battery modules M1 to Mn and the type of the storage battery modules M1 to Mn. This makes it possible to set the discharge completion threshold for the storage battery modules M1 to Mn that are more deteriorated to a higher value, and to prevent the deteriorated storage battery modules M1 to Mn from deteriorating further. Also, different types of storage batteries can be used together.

[0059] Furthermore, it is not essential that the available output power of the storage battery modules M1-Mn to be discharged is maintained at or above the minimum required power of the system to which the power is supplied until the end of the first process. It is sufficient that the available output power of the storage battery modules M1-Mn to be discharged is maintained at or above the minimum required power of the system to which the power is supplied for as long a period as possible from the start of the first process.

[0060] Furthermore, in the second process, it is not essential to discharge all of the storage battery modules M1 to Mn, and the number of storage battery modules M1 to Mn to be discharged may be set appropriately. [Explanation of symbols]

[0061] 1: Energy storage system 20: Bypass circuit 100: Battery control device M1~Mn: Battery module (battery)

Claims

1. A battery control device that controls a power storage system including a plurality of storage batteries connected in series and a bypass circuit that bypasses each of the storage batteries, a first process of discharging each of the plurality of storage batteries while switching the storage batteries to be bypassed by the bypass circuit so that a difference in remaining discharge amounts until the completion of discharge of the plurality of storage batteries is reduced; a second process for completing discharging the plurality of storage batteries after the first process; Run The first process is executed until the OCV or SOC of each storage battery falls to or below a first threshold value of the OCV or SOC set for each storage battery; The first process is executed so that the outputtable power of the storage battery to be discharged does not fall below a minimum required power of a power supply destination; The second process is executed until the output power of the storage battery to be discharged falls below the minimum power required by the power supply destination, or until the OCV or SOC of each storage battery falls below a second threshold value of the OCV or SOC set for each storage battery, A battery control device that estimates a state of each battery before starting the first process and determines whether or not the first threshold needs to be updated based on a result of the estimation.

2. A battery control device that controls a power storage system including a plurality of storage batteries connected in series and a bypass circuit that bypasses each of the storage batteries, a first process of discharging each of the plurality of storage batteries while switching the storage batteries to be bypassed by the bypass circuit so that a difference in remaining discharge amounts until the completion of discharge of the plurality of storage batteries is reduced; a second process for completing discharging the plurality of storage batteries after the first process; Run The first process is executed until the OCV or SOC of each storage battery falls to or below a first threshold value of the OCV or SOC set for each storage battery; The first process is executed so that the outputtable power of the storage battery to be discharged does not fall below a minimum required power of a power supply destination; The second process is executed until the output power of the storage battery to be discharged falls below the minimum power required by the power supply destination, or until the OCV or SOC of each storage battery falls below a second threshold value of the OCV or SOC set for each storage battery, The first process is performed according to a predetermined discharge bypass schedule; the discharge bypass schedule determines, for each period, a combination of two or more storage batteries to be discharged and a storage battery to be bypassed so that a difference in remaining discharge amount until completion of discharge of the multiple storage batteries is reduced in a state in which the outputtable power of the multiple storage batteries is maintained at or above the minimum power required of a power supply destination; A battery control device that estimates a state of each battery before starting the first process and determines whether or not the discharge bypass schedule needs to be updated based on a result of the estimation.

3. The battery control device according to claim 1 or 2, wherein in the first process, the storage batteries whose OCV or SOC has decreased to the first threshold value are sequentially bypassed.

4. A plurality of storage batteries connected in series; A bypass circuit for bypassing each storage battery; a battery control device that controls the bypass circuit; Equipped with The battery control device includes: a first process of discharging each of the plurality of storage batteries while switching the storage batteries to be bypassed by the bypass circuit so that a difference in remaining discharge amounts until the completion of discharge of the plurality of storage batteries is reduced; a second process for completing discharging the plurality of storage batteries after the first process; Run The first process is executed until the OCV or SOC of each storage battery falls to or below a first threshold value of the OCV or SOC set for each storage battery; The first process is executed so that the outputtable power of the storage battery to be discharged does not fall below a minimum required power of a power supply destination; The second process is executed until the output power of the storage battery to be discharged falls below the minimum power required by the power supply destination, or until the OCV or SOC of each storage battery falls below a second threshold value of the OCV or SOC set for each storage battery, The power storage system estimates a state of each storage battery before starting the first process, and determines whether or not the first threshold needs to be updated based on a result of the estimation.

5. A plurality of storage batteries connected in series; A bypass circuit for bypassing each storage battery; a battery control device that controls the bypass circuit; Equipped with The battery control device includes: a first process of discharging each of the plurality of storage batteries while switching the storage batteries to be bypassed by the bypass circuit so that a difference in remaining discharge amounts until the completion of discharge of the plurality of storage batteries is reduced; a second process for completing discharging the plurality of storage batteries after the first process; Run The first process is executed until the OCV or SOC of each storage battery falls to or below a first threshold value of the OCV or SOC set for each storage battery; The first process is executed so that the outputtable power of the storage battery to be discharged does not fall below a minimum required power of a power supply destination; The second process is executed until the output power of the storage battery to be discharged falls below the minimum power required by the power supply destination, or until the OCV or SOC of each storage battery falls below a second threshold value of the OCV or SOC set for each storage battery, The first process is performed according to a predetermined discharge bypass schedule; the discharge bypass schedule determines, for each period, a combination of two or more storage batteries to be discharged and a storage battery to be bypassed so that a difference in remaining discharge amount until completion of discharge of the multiple storage batteries is reduced in a state in which the outputtable power of the multiple storage batteries is maintained at or above the minimum power required of a power supply destination; The power storage system estimates a state of each storage battery before starting the first process, and determines whether or not the discharge bypass schedule needs to be updated based on a result of the estimation.

6. A battery control method executed by a battery control device that controls a power storage system including a plurality of storage batteries connected in series and a bypass circuit that bypasses each of the storage batteries, a first step of discharging each of the plurality of storage batteries while switching the storage batteries to be bypassed by the bypass circuit so that a difference in remaining discharge amounts until the completion of discharge of the plurality of storage batteries decreases; a second step of completing the discharge of the plurality of storage batteries after the first step; Run The first procedure is performed until the OCV or SOC of each storage battery falls to or below a first threshold value of the OCV or SOC set for each storage battery; The first step is performed so that the outputtable power of the storage battery to be discharged does not fall below the minimum power required by the power supply destination; The second procedure is performed until the output power of the storage battery to be discharged falls below the minimum power required by the power supply destination, or until the OCV or SOC of each storage battery falls below a second threshold value of the OCV or SOC set for each storage battery; A battery control method comprising: estimating a state of each storage battery before starting the first procedure; and determining whether or not the first threshold needs to be updated based on a result of the estimation.

7. A battery control method executed by a battery control device that controls a power storage system including a plurality of storage batteries connected in series and a bypass circuit that bypasses each of the storage batteries, a first step of discharging each of the plurality of storage batteries while switching the storage batteries to be bypassed by the bypass circuit so that a difference in remaining discharge amounts until the completion of discharge of the plurality of storage batteries decreases; a second step of completing the discharge of the plurality of storage batteries after the first step; Run The first procedure is performed until the OCV or SOC of each storage battery falls to or below a first threshold value of the OCV or SOC set for each storage battery; The first step is performed so that the outputtable power of the storage battery to be discharged does not fall below the minimum power required by the power supply destination; The second procedure is performed until the output power of the storage battery to be discharged falls below the minimum power required by the power supply destination, or until the OCV or SOC of each storage battery falls below a second threshold value of the OCV or SOC set for each storage battery; The first step is carried out according to a predetermined discharge bypass schedule; the discharge bypass schedule determines, for each period, a combination of two or more storage batteries to be discharged and a storage battery to be bypassed so that a difference in remaining discharge amount until completion of discharge of the multiple storage batteries is reduced in a state in which the outputtable power of the multiple storage batteries is maintained at or above the minimum power required of a power supply destination; A battery control method comprising: estimating a state of each battery before starting the first procedure; and determining whether or not the discharge bypass schedule needs to be updated based on a result of the estimation.

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