Battery control device and battery storage system

Abstract

To efficiently acquire information on voltage changes in a storage battery.SOLUTION: A storage battery controller performs: first processing that discharges a plurality of storage battery modules by a predetermined discharging amount from a predetermined state of charge, and records a module voltage and a string current; second processing that discharges the plurality of storage battery modules discharged by the predetermined discharging amount, to a predetermined state of discharge; third processing that charges the plurality of storage battery modules discharged to the predetermined state of discharge, by a predetermined charging amount; fourth processing that discharges the plurality of storage battery modules charged by the predetermined charging amount, to a predetermined state of discharge, and records a module voltage and a string current; and fifth processing that generates information on voltage changes during discharging of the plurality of storage battery modules on the basis of the module voltage and the string current recorded in the first processing, and the module voltage and the string current recorded in the fourth processing.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] There is known an SOH estimation device that estimates the SOH (State of Health) that indicates the health of a battery (see, for example, Patent Documents 1 and 2). When charging of a storage battery is completed, the SOH estimation device described in Patent Document 1 acquires the voltage of the storage battery from a voltage detection unit and starts measuring the polarization recovery time, and when the difference between the acquired voltage and the voltage to be acquired again becomes equal to or greater than a predetermined voltage, ends the measurement of the polarization recovery time. Then, the SOH estimation device estimates the SOH of the storage battery based on the measured polarization recovery time.

[0003] The SOH estimation device described in Patent Document 2 determines the SOC based on an SOC-OCV curve that indicates the correlation between the SOC (State of Charge) and the OCV (Open Circuit Voltage), and estimates the SOH of the storage battery based on the determined SOC.

[0004] On the other hand, there is known an energy storage system that includes a bypass circuit for each of a plurality of storage batteries connected in series (see, for example, Patent Document 3). In the energy storage system described in Patent Document 3, when the storage batteries reach a fully discharged state or a fully charged state, the bypass circuit is controlled by a controller to switch the storage batteries from a connected state to a bypass state. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-148452 A [Patent Document 2] Patent Publication No. 2021-71320 [Patent Document 3] JP 2022-29299 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the energy storage system described in Patent Document 3, a case is assumed in which the storage batteries are discharged in order to obtain an SOC-OCV curve. In this case, if there is a difference in the deterioration state of the multiple storage batteries, a storage battery with a higher degree of deterioration reaches the fully discharged state first while all the storage batteries are in the fully discharged state, and the storage battery is switched from the connected state to the bypass state. As a result, the SOC-OCV curve for the storage battery becomes discontinuous at the point of switching from the connected state to the bypass state. Therefore, discharging must be performed for each storage battery in order to obtain an SOC-OCV curve, which lengthens the interruption time of the operation of the energy storage system.

[0007] In view of the above circumstances, the present invention aims to provide a battery control device and a battery storage system that can efficiently acquire voltage trend information of a battery in a battery storage system having a battery string in which the battery is switched between a bypass state and a connected state. [Means for solving the problem]

[0008] The battery control device of the present invention is a battery control device that controls a power storage system including a battery string including a plurality of batteries connected in series, a plurality of bypass circuits provided for each of the batteries and switching the batteries between a connected state and a bypass state, and a power converter that converts input and output power of the battery string, and the battery control device performs a first process of discharging the plurality of batteries from a predetermined charge state by a predetermined discharge amount and recording the voltage of the batteries and the current of the battery string, and a second process of discharging the plurality of batteries that have been discharged by the predetermined discharge amount to a predetermined discharge state. The system executes a second process, a third process of charging the multiple storage batteries that have been discharged to the predetermined discharge state by a predetermined charge amount, a fourth process of discharging the multiple storage batteries that have been charged to the predetermined charge amount to the predetermined discharge state and recording the voltages of the storage batteries and the currents of the storage battery strings, and a fifth process of generating voltage trend information that indicates the voltage trends during discharge of the multiple storage batteries based on the voltages of the storage batteries and the currents of the storage battery strings recorded in the first process and the voltages of the storage batteries and the currents of the storage battery strings recorded in the fourth process.

[0009] The battery control device of the present invention is a battery control device for controlling a power storage system including a battery string including a plurality of batteries connected in series, a plurality of bypass circuits provided for each of the batteries and switching the batteries between a connected state and a bypass state, and a power converter for converting input / output power of the battery string, the battery control device comprising: a first process for charging the plurality of batteries from a predetermined discharge state by a predetermined charge amount and recording the voltage of the batteries and the current of the battery string; and a second process for charging the plurality of batteries that have been charged by the predetermined charge amount to a predetermined charge state. The method executes a second process, a third process of discharging a predetermined amount of the storage batteries that have been charged to the predetermined state of charge, a fourth process of charging the storage batteries that have been discharged to the predetermined state of charge and recording the voltages of the storage batteries and the currents of the storage battery strings, and a fifth process of generating voltage trend information that indicates the voltage trends during charging of the multiple storage batteries based on the voltages of the storage batteries and the currents of the storage battery strings recorded in the first process and the voltages of the storage batteries and the currents of the storage battery strings recorded in the fourth process.

[0010] The present invention provides an energy storage system including a battery string including a plurality of storage batteries connected in series, a plurality of bypass circuits provided for each of the storage batteries and switching the storage batteries between a connected state and a bypass state, a power converter that converts input / output power of the storage battery string, and a battery control device that controls the bypass circuit and the power converter, wherein the battery control device performs a first process of discharging the plurality of storage batteries from a predetermined charge state by a predetermined discharge amount and recording the voltage of the storage batteries and the current of the storage battery string, and a second process of discharging the plurality of storage batteries that have been discharged by the predetermined discharge amount. The system executes a second process of discharging the storage batteries to a predetermined discharge state, a third process of charging the multiple storage batteries that have been discharged to the predetermined discharge state by a predetermined charge amount, a fourth process of discharging the multiple storage batteries that have been charged to the predetermined charge amount to the predetermined discharge state and recording the voltages of the storage batteries and the currents of the storage battery strings, and a fifth process of generating voltage trend information that indicates the voltage trends during discharging of the multiple storage batteries based on the voltages of the storage batteries and the currents of the storage battery strings recorded in the first process and the voltages of the storage batteries and the currents of the storage battery strings recorded in the fourth process.

[0011] The present invention provides an energy storage system including a battery string including a plurality of storage batteries connected in series, a plurality of bypass circuits provided for each of the storage batteries and switching the storage batteries between a connected state and a bypass state, a power converter that converts input / output power of the storage battery string, and a battery control device that controls the bypass circuit and the power converter, wherein the battery control device performs a first process of charging the plurality of storage batteries from a predetermined discharge state by a predetermined charge amount and recording the voltage of the storage batteries and the current of the storage battery string, and a second process of charging the plurality of storage batteries that have been charged by the predetermined charge amount. The system executes a second process of charging the storage batteries to a predetermined charge state, a third process of discharging a predetermined amount of the storage batteries that have been charged to the predetermined charge state, a fourth process of charging the storage batteries that have been discharged by the predetermined amount to the predetermined charge state and recording the voltages of the storage batteries and the currents of the storage battery strings, and a fifth process of generating voltage trend information that indicates the voltage trends during charging of the storage batteries based on the voltages of the storage batteries and the currents of the storage battery strings recorded in the first process and the voltages of the storage batteries and the currents of the storage battery strings recorded in the fourth process. Effect of the Invention

[0012] According to the present invention, in a power storage system including a storage battery string in which the storage batteries are switched between a bypass state and a connected state, voltage transition information of the storage batteries can be efficiently acquired. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a circuit diagram showing an outline of a power storage system including a battery control device according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart for explaining a process in which the system controller shown in FIG. 1 acquires a discharge capacity-module voltage curve indicating the correlation between the discharge capacity and voltage of the storage battery module. [Diagram 3]FIG. 3 is a graph showing the correlation between the discharge capacity and the voltage of the storage battery module during execution of the process shown in the flowchart of FIG. [Figure 4] FIG. 4 is a graph showing the correlation between the discharge capacity and the voltage of the storage battery module during execution of the process shown in the flowchart of FIG. [Diagram 5] FIG. 5 is a graph showing a discharge capacity-module voltage curve generated by the process shown in the flowchart of FIG. [Figure 6] FIG. 6 is a graph showing a discharge capacity-module voltage curve generated by the process shown in the flowchart of FIG. [Figure 7] FIG. 7 is a graph showing a discharge capacity-module voltage curve generated by the process shown in the flowchart of FIG. [Figure 8] FIG. 8 is a flowchart for explaining a process in which the system controller shown in FIG. 1 acquires a charge capacity-module voltage curve indicating the correlation between the charge capacity and the voltage of the storage battery module. [Figure 9] FIG. 9 is a graph showing the correlation between the charge capacity and the voltage of the storage battery module during execution of the process shown in the flowchart of FIG. [Figure 10] FIG. 10 is a graph showing the correlation between the charge capacity and the voltage of the storage battery module during execution of the process shown in the flowchart of FIG. [Figure 11] FIG. 11 is a graph showing a charge capacity-module voltage curve generated by the process shown in the flowchart of FIG. [Figure 12] FIG. 12 is a graph showing a charge capacity-module voltage curve generated by the process shown in the flowchart of FIG. [Figure 13] FIG. 13 is a graph showing a charge capacity-module voltage curve generated by the process shown in the flowchart of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 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.

[0015] Fig. 1 is a circuit diagram showing an outline of a power storage system 1 including a battery control device 100 according to one embodiment of the present invention. As shown in this figure, the power storage system 1 includes m (m is an integer of 2 or more) storage battery strings STR1-STRm, a string bus 3, m power converters PC1-PCm, and the battery control device 100. The m storage battery strings STR1-STRm are connected to each other and to an external system (not shown) via the m power converters PC1-PCm and the string bus 3. The power storage system 1 is a stationary or vehicle-mounted power source.

[0016] Each of the storage battery strings STR1 to STRm includes n (n is an integer of 2 or more) storage battery modules M1 to Mn connected in series. Although not particularly limited, the storage battery modules M1 to Mn in this embodiment are regenerated second-hand storage batteries, and there is a difference in the deterioration state of each of the storage battery modules M1 to Mn. The storage battery modules M1 to Mn are, for example, secondary batteries such as lithium ion batteries and lithium ion capacitors.

[0017] The storage battery modules M1 to Mn are charged by receiving power from an external system via the string bus 3 and the power converters PC1 to PCm, and discharge the charged power via the power converters PC1 to PCm and the string bus 3 to supply power to the external system.

[0018] The external system includes a load, a generator, etc. When the power storage system 1 is for stationary use, household appliances, commercial power systems, 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.

[0019] The battery strings STR1 to STRm may include n battery cells or battery packs connected in series, instead of the n battery modules M1 to Mn connected in series. The power storage system 1 may include a bypass circuit that bypasses each battery cell or each battery pack.

[0020] The power converters PC1 to PCm are DC / DC converters or DC / AC converters, and are connected to the string bus 3. In addition, the power converters PC1 to PCm are connected to the positive electrode of the starting storage battery module M1 and the negative electrode of the terminal storage battery module Mn.

[0021] When the storage battery strings STR1-STRm are being charged, the power converters PC1-PCm convert the voltage input from the string bus 3 and output it to the multiple storage battery modules M1-Mn. On the other hand, when the storage battery strings STR1-STRm are being discharged, the power converters PC1-PCm convert the voltage input from the multiple storage battery modules M1-Mn and output it to the string bus 3. When the current flowing through the string bus 3 is an AC current, the power converters PC1-PCm include synchronization means for following changes in instantaneous values.

[0022] Each of the storage battery strings STR1 to STRm includes n voltage sensors 12, a current sensor 13, and n bypass circuits B1 to Bn. The voltage sensor 12 is connected between the positive and negative terminals of each of the storage battery modules M1 to Mn. The voltage sensor 12 measures the inter-terminal voltage of each of the storage battery modules M1 to Mn.

[0023] The current sensor 13 is provided in the current path of the storage battery strings STR1 to STRm. The current sensor 13 measures the charge / discharge current (hereinafter sometimes referred to as string current) of the storage battery strings STR1 to STRn.

[0024] The bypass circuits B1 to Bn are provided for each of the storage battery modules M1 to Mn. The bypass circuits B1 to Bn include a bypass line BL and switches S1 and S2. The bypass line BL is a power line that bypasses each of the storage battery modules M1 to Mn. The switch S1 is provided on the bypass line BL. The switch S1 is, for example, a semiconductor switch, a mechanical switch, or a relay. The switch S2 is provided between the positive electrode of each of the storage battery modules M1 to Mn and one end of the bypass line BL. The switch S2 is, for example, a semiconductor switch, a mechanical switch, or a relay.

[0025] The starting battery module M1 and the ending battery module Mn are connected to an external system via the power converters PC1-PCm and the string bus 3. When the switch S1 is open and the switch S2 is closed in all the bypass circuits B1-Bn, all the battery modules M1-Mn are connected in series to the external system. 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 battery module M1-Mn corresponding to that bypass circuit B1-Bn is bypassed.

[0026] The battery control device 100 includes a system controller 101 and n string controllers 102. The system controller 101 controls the power converters PC1-PCm. On the other hand, the string controller 102 controls each of the bypass circuits B1-Bn, and transmits information on the state of the bypass circuits B1-Bn (open / closed state of the switches S1, S2) to the system controller 101. In addition, the string controller 102 receives detection signals from each of the voltage sensors 12 and each of the current sensors 13, and transmits the detection signals to the system controller 101.

[0027] The system controller 101 estimates the battery states (hereinafter referred to as state estimation) of the storage battery modules M1 to Mn, such as SOH and SOC, based on a prestored SOC-OCV curve (discharge capacity-module voltage curve or charge capacity-module voltage curve described later) and detection signals from the voltage sensor 12 and the current sensor 13. In particular, in this embodiment, the system controller 101 executes a discharge process or a charge process of the target storage battery strings STR1 to STRm for which acquisition of the basic data is required, in order to acquire an SOC-OCV curve that is basic data for estimating the state of the SOH, SOC, etc. The system controller 101 may execute only a discharge process for the purpose of acquiring the discharge capacity-module voltage curve, or may execute only a charge process for the purpose of acquiring the charge capacity-module voltage curve. The system controller 101 may execute both a discharge process for the purpose of acquiring the discharge capacity-module voltage curve and a charge process for the purpose of acquiring the charge capacity-module voltage curve.

[0028] Here, a predetermined range for the discharge capacity of the storage battery modules M1 to Mn is defined as SOC=100%. The SOC can be obtained by comparing the measured or estimated voltage (corresponding to OCV; hereinafter, sometimes referred to as module voltage) of the storage battery modules M1 to Mn with the SOC-OCV curve.

[0029] The current total capacity of the storage battery modules M1 to Mn can be calculated by converting the charge / discharge capacity in a predetermined range of the SOC-OCV curve to SOC=100%. The SOH can be calculated by calculating the ratio of the initial total capacity of the storage battery modules M1 to Mn to the current total capacity, or by calculating the ratio of the initial and current capacities in a predetermined range of the SOC-OCV curve. It is also possible to determine failures or mounting defects of the storage battery modules M1 to Mn by comparing the initial SOC-OCV curve with the current SOC-OCV curve.

[0030] Fig. 2 is a flowchart for explaining a process in which the system controller 101 shown in Fig. 1 acquires a discharge capacity-module voltage curve (SOC-OCV curve) showing the correlation between the discharge capacity and voltage of the storage battery modules M1 to Mn. Figs. 3 and 4 are graphs showing the correlation between the discharge capacity and voltage of the storage battery modules M1 to Mn during execution of the process shown in the flowchart of Fig. 2. Figs. 5 to 7 are graphs showing the discharge capacity-module voltage curves generated by the process shown in the flowchart of Fig. 2.

[0031] First, in step S1 shown in FIG. 2, the system controller 101 determines the target storage battery strings STR1-STRm that require updating of basic data used in estimating states such as SOH and SOC. Next, in step S2, the system controller 101 controls the corresponding power converters PC1-PCm to input power to the target storage battery strings STR1-STRm. At this time, the system controller 101 puts all the storage battery modules M1-Mn of the target storage battery strings STR1-STRm into a fully charged state. In addition, every time the voltage of each storage battery module M1-Mn rises to a predetermined end-of-charge voltage, the string controller 102 switches the storage battery modules M1-Mn from a connected state to a bypass state by the bypass circuits B1-Bn corresponding to the storage battery modules M1-Mn. Note that the state in which the voltage of each storage battery module M1-Mn is the predetermined end-of-charge voltage is the state shown in FIG. 3 (1), that is, the fully charged state of each storage battery module M1-Mn.

[0032] Here, there are differences in the discharge capacity of each of the storage battery modules M1 to Mn as shown in Fig. 3. As the degree of deterioration of the storage battery modules M1 to Mn increases, the discharge capacity decreases and the time required to go from a fully charged state to a fully discharged state decreases.

[0033] Next, in step S3, the system controller 101 transmits an instruction to switch all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm from the bypass state to the connected state to the string controller 102. As a result, all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm are brought into a series-connected state.

[0034] Next, in step S4, the system controller 101 starts recording the voltages of the storage battery modules M1-Mn detected by the voltage sensors 12 of the target storage battery strings STR1-STRm and the currents detected by the current sensors 13. Here, the recording of the voltages and currents from step S5 to step S7 is referred to as a first recording. On the other hand, the recording of the voltages and currents from step S12 to step S15 is referred to as a second recording.

[0035] Next, in step S5, the system controller 101 controls the corresponding power converters PC1 to PCm to start discharging the target storage battery strings STR1 to STRm at a constant current and a low current.

[0036] Next, in step S6, the system controller 101 determines whether the discharge amounts of all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm have reached a predetermined discharge amount, based on an integrated value of the discharge current detected by the current sensor 13. The state shown in Fig. 3 (2) is the state in which the discharge amounts of all the storage battery modules M1 to Mn have reached the predetermined discharge amount. If a positive determination is made in step S6, the process proceeds to step S7, and if a negative determination is made in step S6, step S6 is repeated.

[0037] Here, the "predetermined discharge amount" is set so that there is an overlapping range between the discharge capacity-module voltage curve obtained in the first recording and the discharge capacity-module voltage curve obtained in the second recording. The storage battery modules M1-Mn that have reached the discharge end voltage during the discharge of the "predetermined discharge amount" are switched from the connected state to the bypass state by the bypass circuits B1-Bn. In this case, there is a possibility that the discharge capacity-module voltage curve obtained in the first recording and the discharge capacity-module voltage curve obtained in the second recording become discontinuous. Therefore, it is preferable to set the "predetermined discharge amount" so that the storage battery modules M1-Mn do not switch from the connected state to the bypass state during the discharge of the "predetermined discharge amount" (during the execution of the first recording). On the other hand, when the storage battery modules M1-Mn switch from the connected state to the bypass state during the discharge of the "predetermined discharge amount", processes such as smoothing and extrapolation are performed to generate a continuous discharge capacity-module voltage curve.

[0038] Next, in step S7, the system controller 101 stops recording (first recording) the voltages of the storage battery modules M1 to Mn detected by the voltage sensors 12 and the currents detected by the current sensors 13 of the target storage battery strings STR1 to STRm.

[0039] Next, in step S8, the system controller 101 controls the corresponding power converters PC1-PCm to output power from all the storage battery modules M1-Mn of the target storage battery strings STR1-SRTm. At this time, the system controller 101 puts all the storage battery modules M1-Mn of the target storage battery strings STR1-STRm into a fully discharged state. In addition, every time the voltage of each storage battery module M1-Mn drops to a predetermined discharge end voltage, the string controller 102 switches the storage battery module M1-Mn from a connected state to a bypass state by the bypass circuit B1-Bn corresponding to the storage battery module M1-Mn. Note that the state in which the voltage of each storage battery module M1-Mn is the predetermined discharge end voltage is the state shown in (3) of FIG. 3 and (3) of FIG. 4, that is, the fully discharged state of each storage battery module M1-Mn.

[0040] Next, in step S9, the system controller 101 transmits an instruction to switch all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm from the bypass state to the connected state to the string controller 102. As a result, all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm are brought into a series-connected state.

[0041] Next, in step S10, the system controller 101 controls the corresponding power converters PC1 to PCm to start charging the target storage battery strings STR1 to STRm with a constant current.

[0042] Next, in step S11, the system controller 101 determines whether the charge amounts of all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm have reached a predetermined charge amount, based on the integrated value of the charging current detected by the current sensor 13. The state shown in (4) in Fig. 4 is the state in which the charge amounts of all the storage battery modules M1 to Mn have reached the predetermined charge amount.

[0043] Here, the "predetermined charge amount" is set so that there is an overlapping range between the discharge capacity-module voltage curve obtained in the first record and the discharge capacity-module voltage curve obtained in the second record. The storage battery modules M1-Mn that have reached the charge end voltage during charging with the "predetermined charge amount" are switched from the connected state to the bypass state by the bypass circuits B1-Bn. In this case, there is a possibility that the discharge capacity-module voltage curve obtained in the first record and the discharge capacity-module voltage curve obtained in the second record become discontinuous. Therefore, it is preferable to set the "predetermined charge amount" so that the storage battery modules M1-Mn do not switch from the connected state to the bypass state during charging with the "predetermined charge amount". On the other hand, when the storage battery modules M1-Mn switch from the connected state to the bypass state during charging with the "predetermined charge amount", processes such as smoothing and extrapolation are performed to generate a continuous discharge capacity-module voltage curve.

[0044] If a positive determination is made in step S11, the process proceeds to step S12, and if a negative determination is made in step S11, step S11 is repeated. In step S12, the system controller 101 starts recording (second recording) the voltages of the storage battery modules M1-Mn detected by the voltage sensors 12 of the target storage battery strings STR1-STRm and the currents detected by the current sensors 13.

[0045] Next, in step S13, the system controller 101 controls the corresponding power converters PC1-PCm to start constant-current and low-current discharge of the target storage battery strings STR1-STRm. Here, if the storage battery modules M1-Mn are switched from the connected state to the bypass state during charging in step S11, the system controller 101 maintains the bypass state of the storage battery modules M1-Mn until the middle of step S14 described below.

[0046] Next, in step S14, the system controller 101 determines whether or not discharging of all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm is completed, based on the integrated value of the discharge current detected by the current sensor 13. The state shown in (5) in FIG. 4 is the fully discharged state of all the storage battery modules M1 to Mn.

[0047] Here, when the storage battery modules M1-Mn are switched from the connected state to the bypass state during charging in step S11, the system controller 101 maintains the storage battery modules M1-Mn in the bypass state until the remaining discharge capacities of the storage battery modules M1-Mn and the other storage battery modules M1-Mn are equalized.

[0048] If a positive determination is made in step S14, the process proceeds to step S15, and if a negative determination is made in step S14, step S14 is repeated. In step S15, the system controller 101 stops recording (second recording) the voltages of the storage battery modules M1-Mn detected by the voltage sensors 12 of the target storage battery strings STR1-STRm and the currents detected by the current sensors 13.

[0049] Next, in step S16, the system controller 101 generates a discharge capacity-module voltage curve for each of the storage battery modules M1-Mn based on the first record and the second record for each of the storage battery modules M1-Mn. Specifically, the system controller 101 generates a discharge capacity-module voltage curve for the high SOC region based on the first record for each of the storage battery modules M1-Mn. On the other hand, the system controller 101 generates a discharge capacity-module voltage curve for the low SOC region based on the second record for each of the storage battery modules M1-Mn. Then, the system controller 101 generates a discharge capacity-module voltage curve showing the transition of voltage from a fully charged state to a fully discharged state by combining the discharge capacity-module voltage curve for the high SOC region and the discharge capacity-module voltage curve for the low SOC region.

[0050] Here, as described above, it is possible that the storage battery modules M1 to Mn are switched from the connected state to the bypass state while the first recording or the second recording is being performed. In this case, the system controller 101 performs processes such as smoothing and extrapolation on the boundary between the range corresponding to the first recording and the range corresponding to the second recording in the discharge capacity vs. module voltage curve, and generates a continuous discharge capacity vs. module voltage curve as shown in Figures 5 to 7. This ends the process shown in the flowchart of Figure 3.

[0051] As described above, the battery control device 100 of this embodiment executes the following first to fifth processes.

[0052] (First process) A plurality of storage battery modules M1 to Mn are discharged from a fully charged state (a predetermined charged state) by a predetermined discharge amount, and the module voltage and string current are recorded. (Second Processing) The plurality of storage battery modules M1 to Mn that have been discharged by the above-mentioned predetermined discharge amount are discharged to a fully discharged state (predetermined discharge state). (Third Processing) A plurality of storage battery modules M1 to Mn that have been discharged to a fully discharged state (a predetermined discharged state) are charged by a predetermined charge amount. (Fourth Process) The plurality of storage battery modules M1 to Mn charged to the above-mentioned predetermined charge amount are discharged to a fully discharged state (predetermined discharged state), and the voltages of the storage battery modules M1 to Mn and the currents of the storage battery strings STR1 to STRm are recorded. (Fifth Process) Based on the module voltages and string currents recorded in the first process and the module voltages and string currents recorded in the fourth process, voltage transition information indicating voltage transitions during discharging of the multiple storage battery modules M1 to Mn is generated.

[0053] This makes it possible to prevent the storage battery modules M1-Mn from switching from the connected state to the bypass state during the discharging mode executed to acquire voltage transition information showing the voltage transition during discharging of the multiple storage battery modules M1-Mn. Therefore, even when the discharging mode is executed for each of the storage battery strings STR1-STRm, it is possible to prevent the generation of a discontinuous range in the voltage transition information from the fully charged state (predetermined charged state) to the fully discharged state (predetermined discharged state). As a result, it is possible to efficiently acquire voltage transition information during discharging of the multiple storage battery modules M1-Mn, and to shorten the interruption time of the operation of the power storage system 1.

[0054] In addition, the specified discharge amount and the specified charge amount are set so that a portion of the range (high SOC region) corresponding to the module voltage and string current recorded in the first process in the voltage transition information during discharge overlaps with a portion of the range (low SOC region) corresponding to the module voltage and string current recorded in the fourth process in the voltage transition information during discharge.

[0055] As a result, when the storage battery modules M1-Mn are switched from the connected state to the bypass state at a discharge capacity corresponding to an overlapping range of the high SOC region and the low SOC region during execution of the first process, the recorded information of the fourth process can be used for that overlapping range. On the other hand, when the storage battery modules M1-Mn are switched from the connected state to the bypass state at a discharge capacity corresponding to an overlapping range of the high SOC region and the low SOC region during execution of the third process, the recorded information of the first process can be used for that overlapping range. Therefore, a continuous discharge capacity-module voltage curve can be obtained as voltage transition information during discharge of the multiple storage battery modules M1-Mn.

[0056] Furthermore, if the storage battery modules M1-Mn are switched from the connected state to the bypass state during execution of the third process, the battery control device 100 maintains the bypass state of the storage battery modules M1-Mn until the discharge capacities of the storage battery modules M1-Mn in the bypass state and the other storage battery modules M1-Mn in the connected state become equal in the fourth process. This makes it possible to simultaneously discharge the multiple storage battery modules M1-Mn to a fully discharged state (a predetermined discharge state) in the fourth process.

[0057] Fig. 8 is a flowchart for explaining a process in which the system controller 101 shown in Fig. 1 acquires a charge capacity-module voltage curve (SOC-OCV curve) showing the correlation between the charge capacity and voltage of the storage battery modules M1 to Mn. Figs. 9 and 10 are graphs showing the correlation between the charge capacity and voltage of the storage battery modules M1 to Mn during execution of the process shown in the flowchart of Fig. 8. Figs. 11 to 13 are graphs showing the charge capacity-module voltage curves generated by the process shown in the flowchart of Fig. 8.

[0058] First, in step S21, the system controller 101 determines the target storage battery strings STR1-STRm that require updating of basic data used in estimating the state of SOH, SOC, etc. Next, in step S22, the system controller 101 controls the corresponding power converters PC1-PCm to output power from the target storage battery strings STR1-STRm. At this time, the system controller 101 puts all the storage battery modules M1-Mn of the target storage battery strings STR1-STRm into a fully discharged state. In addition, every time the voltage of each storage battery module M1-Mn rises to a predetermined discharge end voltage, the string controller 102 switches the storage battery modules M1-Mn from a connected state to a bypass state by the bypass circuits B1-Bn corresponding to the storage battery modules M1-Mn. Note that the state in which the voltage of each storage battery module M1-Mn is the predetermined discharge end voltage is the state shown in (1) of FIG. 9, that is, the fully discharged state of each storage battery module M1-Mn.

[0059] Here, there are differences in charge capacity among the storage battery modules M1 to Mn as shown in Fig. 9. As the deterioration level of the storage battery modules M1 to Mn increases, the charge capacity decreases and the time required to go from a fully discharged state to a fully charged state decreases.

[0060] Next, in step S23, the system controller 101 transmits an instruction to switch all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm from the bypass state to the connected state to the string controller 102. As a result, all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm are brought into a series-connected state.

[0061] Next, in step S24, the system controller 101 starts recording the voltages of the storage battery modules M1-Mn detected by the voltage sensors 12 of the target storage battery strings STR1-STRm and the currents detected by the current sensors 13. Here, the recording of the voltages and currents from step S25 to step S27 is referred to as a first recording. On the other hand, the recording of the voltages and currents from step S32 to step S35 is referred to as a second recording.

[0062] Next, in step S25, the system controller 101 controls the corresponding power converters PC1 to PCm to start charging the target storage battery strings STR1 to STRm with a constant current and a low current.

[0063] Next, in step S26, the system controller 101 determines whether the charge amounts of all the storage battery modules M1-Mn of the target storage battery strings STR1-STRm have reached a predetermined charge amount, based on an integrated value of the charging current detected by the current sensor 13. The state shown in Fig. 9 (2) is the state in which the charge amounts of all the storage battery modules M1-Mn have reached the predetermined charge amount. If a positive determination is made in step S26, the process proceeds to step S27, and if a negative determination is made in step S26, step S26 is repeated.

[0064] Here, the "predetermined charge amount" is set so that there is an overlapping range between the charge capacity-module voltage curve obtained in the first record and the discharge capacity-module voltage curve obtained in the second record. The storage battery modules M1-Mn that have reached the charge end voltage during charging with the "predetermined charge amount" are switched from the connected state to the bypass state by the bypass circuits B1-Bn. In this case, there is a possibility that the charge capacity-module voltage curve obtained in the first record and the charge capacity-module voltage curve obtained in the second record become discontinuous. Therefore, it is preferable to set the "predetermined charge amount" so that the storage battery modules M1-Mn do not switch from the connected state to the bypass state during charging with the "predetermined charge amount" (during execution of the first record). On the other hand, when the storage battery modules M1-Mn switch from the connected state to the bypass state during charging with the "predetermined charge amount", processes such as smoothing and extrapolation are performed to generate a continuous discharge capacity-module voltage curve.

[0065] Next, in step S27, the system controller 101 stops recording (first recording) the voltages of the storage battery modules M1 to Mn detected by the voltage sensors 12 and the currents detected by the current sensors 13 of the target storage battery strings STR1 to STRm.

[0066] Next, in step S28, the system controller 101 controls the corresponding power converters PC1-PCm to input power to all the storage battery modules M1-Mn of the target storage battery strings STR1-SRTm. At this time, the system controller 101 brings all the storage battery modules M1-Mn of the target storage battery strings STR1-STRm into a fully charged state. In addition, every time the voltage of each storage battery module M1-Mn rises to a predetermined end-of-charge voltage, the string controller 102 switches the storage battery module M1-Mn from a connected state to a bypass state by the bypass circuit B1-Bn corresponding to the storage battery module M1-Mn. Note that the state in which the voltage of each storage battery module M1-Mn is the predetermined end-of-charge voltage is the state shown in (3) of FIG. 9 and (3) of FIG. 10, that is, the fully charged state of each storage battery module M1-Mn.

[0067] Next, in step S29, the system controller 101 transmits an instruction to switch all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm from the bypass state to the connected state to the string controller 102. As a result, all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm are brought into a series-connected state.

[0068] Next, in step S30, the system controller 101 controls the corresponding power converters PC1 to PCm to start discharging the constant current from the target storage battery strings STR1 to STRm.

[0069] Next, in step S31, the system controller 101 determines whether the discharge amounts of all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm have reached a predetermined discharge amount, based on the integrated value of the discharge current detected by the current sensor 13. The state shown in (4) in Fig. 10 is the state in which the discharge amounts of all the storage battery modules M1 to Mn have reached the predetermined discharge amount.

[0070] Here, the "predetermined discharge amount" is set so that there is an overlapping range between the charge capacity-module voltage curve obtained in the first record and the charge capacity-module voltage curve obtained in the second record. The storage battery modules M1-Mn that have reached the discharge end voltage during the discharge of the "predetermined discharge amount" are switched from the connected state to the bypass state by the bypass circuits B1-Bn. In this case, there is a possibility that the charge capacity-module voltage curve obtained in the first record and the charge capacity-module voltage curve obtained in the second record become discontinuous. Therefore, it is preferable to set the "predetermined discharge amount" so that the storage battery modules M1-Mn do not switch from the connected state to the bypass state during the discharge of the "predetermined discharge amount". On the other hand, when the storage battery modules M1-Mn switch from the connected state to the bypass state during the discharge of the "predetermined discharge amount", processes such as smoothing and extrapolation are performed to generate a continuous charge capacity-module voltage curve.

[0071] If a positive determination is made in step S31, the process proceeds to step S32, and if a negative determination is made in step S31, step S31 is repeated. In step S32, the system controller 101 starts recording (second recording) the voltages of the storage battery modules M1-Mn detected by the voltage sensors 12 of the target storage battery strings STR1-STRm and the currents detected by the current sensors 13.

[0072] Next, in step S33, the system controller 101 controls the corresponding power converters PC1-PCm to start constant current and low current charging of the target storage battery strings STR1-STRm. Here, if the storage battery modules M1-Mn are switched from the connected state to the bypass state during discharging in step S31, the system controller 101 maintains the bypass state of the storage battery modules M1-Mn until the middle of step S34 described below.

[0073] Next, in step S34, the system controller 101 determines whether or not charging of all the storage battery modules M1 to Mn of the target storage battery strings STR1 to STRm is completed, based on the integrated value of the charging current detected by the current sensor 13. The state shown in (5) in Fig. 10 is the fully charged state of all the storage battery modules M1 to Mn.

[0074] Here, when the storage battery module M1-Mn is switched from the connected state to the bypass state during discharging in step S31, the system controller 101 maintains the storage battery module M1-Mn in the bypass state until the remaining charge capacities of the storage battery module M1-Mn and the other storage battery modules M1-Mn are equalized.

[0075] If a positive determination is made in step S34, the process proceeds to step S35, and if a negative determination is made in step S34, step S34 is repeated. In step S35, the system controller 101 stops recording (second recording) the voltages of the storage battery modules M1-Mn detected by the voltage sensors 12 of the target storage battery strings STR1-STRm and the currents detected by the current sensors 13.

[0076] Next, in step S36, the system controller 101 generates a charge capacity-module voltage curve for each of the storage battery modules M1-Mn based on the first record and the second record for each of the storage battery modules M1-Mn. Specifically, the system controller 101 generates a charge capacity-module voltage curve for the low SOC region based on the first record for each of the storage battery modules M1-Mn. On the other hand, the system controller 101 generates a charge capacity-module voltage curve for the high SOC region based on the second record for each of the storage battery modules M1-Mn. Then, the system controller 101 generates a charge capacity-module voltage curve that shows the transition of voltage from a fully discharged state to a fully charged state by combining the charge capacity-module voltage curve for the low SOC region and the charge capacity-module voltage curve for the high SOC region.

[0077] Here, as described above, it is possible that the storage battery modules M1 to Mn are switched from the connected state to the bypass state while the first record or the second record is being performed. In this case, the system controller 101 performs processes such as smoothing and extrapolation on the boundary between the range corresponding to the first record and the range corresponding to the second record in the charge capacity vs. module voltage curve, and generates a continuous charge capacity vs. module voltage curve as shown in Figures 11 to 13. This ends the process shown in the flowchart of Figure 8.

[0078] As described above, the battery control device 100 of this embodiment executes the following first to fifth processes.

[0079] (First process) A plurality of storage battery modules M1 to Mn are charged by a predetermined charge amount from a fully discharged state (a predetermined discharged state), and the module voltage and string current are recorded. (Second Processing) The plurality of storage battery modules M1 to Mn, which have been charged to the above-mentioned predetermined charge amount, are charged to a fully charged state (a predetermined charged state). (Third Processing) A plurality of storage battery modules M1 to Mn that have been charged to a fully charged state (a predetermined charged state) are discharged by a predetermined discharge amount. (Fourth Process) The plurality of storage battery modules M1 to Mn that have been discharged by the above-mentioned predetermined discharge amount are charged to a fully charged state (predetermined charged state), and the module voltage and string current are recorded. (Fifth Process) Voltage transition information indicating the voltage transitions during charging of the multiple storage battery modules M1 to Mn is generated based on the module voltages and string currents recorded in the first process and the module voltages and string currents recorded in the fourth process.

[0080] This makes it possible to prevent the storage battery modules M1-Mn from switching from the connected state to the bypass state during the charging mode executed to acquire voltage transition information showing the voltage transition during charging of the multiple storage battery modules M1-Mn. Therefore, even when the charging mode is executed for each of the storage battery strings STR1-STRm, it is possible to prevent the generation of a discontinuous range in the voltage transition information from the fully discharged state (predetermined discharged state) to the fully charged state (predetermined charged state). As a result, it is possible to efficiently acquire voltage transition information during charging of the multiple storage battery modules M1-Mn, and shorten the interruption time of the operation of the power storage system 1.

[0081] In addition, the specified charge amount and the specified discharge amount are set so that a portion of the range (low SOC region) corresponding to the module voltage and string current recorded in the first process in the voltage transition information during charging overlaps with a portion of the range (high SOC region) corresponding to the module voltage and string current recorded in the fourth process in the voltage transition information during charging.

[0082] As a result, if the storage battery modules M1-Mn are switched from the connected state to the bypass state at a charge capacity corresponding to an overlapping range of the low SOC region and the high SOC region during execution of the first process, the recorded information of the fourth process can be used for that overlapping range. On the other hand, if the storage battery modules M1-Mn are switched from the connected state to the bypass state at a charge capacity corresponding to an overlapping range of the low SOC region and the high SOC region during execution of the third process, the recorded information of the first process can be used for that overlapping range. Therefore, a continuous charge capacity-module voltage curve can be obtained as voltage transition information during charging of the multiple storage battery modules M1-Mn.

[0083] Furthermore, if the storage battery modules M1-Mn are switched from the connected state to the bypassed state during execution of the third process, the battery control device 100 maintains the bypassed state of the storage battery modules M1-Mn until the charge capacities of the storage battery modules M1-Mn in the bypassed state and the other storage battery modules M1-Mn in the connected state become equal in the fourth process. This makes it possible to charge the multiple storage battery modules M1-Mn simultaneously to a fully charged state (a predetermined charge state) in the fourth process.

[0084] The present invention has been described above based on the above-mentioned embodiment, but the present invention is not limited to the above-mentioned embodiment, and modifications may be made without departing from the spirit of the present invention, and publicly known or well-known technologies may be combined as appropriate.

[0085] For example, in the above-mentioned embodiment, the "predetermined charge state" in the claims is defined as a "fully charged state". However, the "predetermined charge state" is not limited to the "fully charged state", but includes "a state in which the remaining charge capacity is small and close to full charge", "a state in which the remaining charge capacity exceeds the small range and is far from full charge", etc. Also, in the above-mentioned embodiment, the "predetermined discharge state" in the claims is defined as a "fully discharged state". However, the "predetermined discharge state" is not limited to the "fully discharged state", but includes "a state in which the remaining discharge capacity is small and close to full discharge", "a state in which the remaining discharge capacity exceeds the small range and is far from full discharge", etc. [Explanation of symbols]

[0086] 1: Energy storage system 100: Battery control device B1~Bn: Bypass circuit M1~Mn: Battery module (battery) PC1~PCm: Power converter STR1~STRm: Battery strings

Claims

1. A battery control device for controlling a power storage system including a battery string including a plurality of storage batteries connected in series, a plurality of bypass circuits provided for each of the storage batteries and switching the storage batteries between a connected state and a bypass state, and a power converter for converting input / output power of the battery string, a first process for discharging a plurality of the batteries from a predetermined state of charge by a predetermined discharge amount and recording the voltage of the batteries and the current of the battery string; a second process of discharging the plurality of storage batteries that have been discharged by the predetermined discharge amount to a predetermined discharge state; a third process of charging the plurality of storage batteries discharged to the predetermined discharge state by a predetermined charge amount; a fourth process of discharging the plurality of batteries that have been charged to the predetermined charge amount to the predetermined discharge state and recording the voltage of the batteries and the current of the battery string; a fifth process of generating voltage transition information indicating voltage transitions during discharging of the plurality of storage batteries based on the voltages of the storage batteries and the currents of the storage battery strings recorded in the first process and the voltages of the storage batteries and the currents of the storage battery strings recorded in the fourth process; A battery control device that performs the above.

2. 2. The battery control device according to claim 1, wherein the specified discharge amount and the specified charge amount are set so that a portion of a range corresponding to the voltage of the storage battery and the current of the storage battery string recorded in the first processing in the voltage transition information overlaps with a portion of a range corresponding to the voltage of the storage battery and the current of the storage battery string recorded in the fourth processing in the voltage transition information.

3. 3. The battery control device according to claim 1, wherein when the storage battery is switched from a connected state to a bypass state by the bypass circuit during execution of the third process, the bypass state of the storage battery is maintained until the discharge capacities of the storage battery in the bypass state and the storage battery in the connected state become equal in the fourth process.

4. A battery control device for controlling a power storage system including a battery string including a plurality of storage batteries connected in series, a plurality of bypass circuits provided for each of the storage batteries and switching the storage batteries between a connected state and a bypass state, and a power converter for converting input / output power of the battery string, a first process for charging a plurality of the batteries from a predetermined discharge state to a predetermined charge amount and recording the voltage of the batteries and the current of the battery string; a second process of charging the plurality of storage batteries, each of which has been charged to the predetermined charge amount, to a predetermined charge state; a third process of discharging the plurality of storage batteries that have been charged to the predetermined charge state by a predetermined discharge amount; a fourth process of charging the batteries that have been discharged by the predetermined discharge amount to the predetermined state of charge and recording the voltage of the batteries and the current of the battery string; a fifth process of generating voltage transition information indicating voltage transitions during charging of the plurality of storage batteries based on the voltages of the storage batteries and the currents of the storage battery strings recorded in the first process and the voltages of the storage batteries and the currents of the storage battery strings recorded in the fourth process; A battery control device that performs the above.

5. 5. The battery control device according to claim 4, wherein the specified charge amount and the specified discharge amount are set so that a portion of a range corresponding to the voltage of the storage battery and the current of the storage battery string recorded in the first processing in the voltage transition information overlaps with a portion of a range corresponding to the voltage of the storage battery and the current of the storage battery string recorded in the fourth processing in the voltage transition information.

6. 6. The battery control device according to claim 4 or 5, wherein when the storage battery is switched from a connected state to a bypass state by the bypass circuit during execution of the third process, the bypass state of the storage battery is maintained until the charge capacities of the storage battery in the bypass state and the storage battery in the connected state become equal in the fourth process.

7. a battery string including a plurality of storage batteries connected in series and a plurality of bypass circuits each provided for each of the storage batteries and configured to switch the storage battery between a connected state and a bypass state; a power converter that converts input / output power of the storage battery string; a battery control device that controls the bypass circuit and the power converter; A power storage system comprising: The battery control device includes: a first process for discharging a plurality of the batteries from a predetermined state of charge by a predetermined discharge amount and recording the voltage of the batteries and the current of the battery string; a second process of discharging the plurality of storage batteries that have been discharged by the predetermined discharge amount to a predetermined discharge state; a third process of charging the plurality of storage batteries discharged to the predetermined discharge state by a predetermined charge amount; a fourth process of discharging the plurality of batteries that have been charged to the predetermined charge amount to the predetermined discharge state and recording the voltage of the batteries and the current of the battery string; a fifth process of generating voltage transition information indicating voltage transitions during discharging of the plurality of storage batteries based on the voltages of the storage batteries and the currents of the storage battery strings recorded in the first process and the voltages of the storage batteries and the currents of the storage battery strings recorded in the fourth process; A storage system that performs the above.

8. a battery string including a plurality of storage batteries connected in series and a plurality of bypass circuits each provided for each of the storage batteries and configured to switch the storage battery between a connected state and a bypass state; a power converter that converts input / output power of the storage battery string; a battery control device that controls the bypass circuit and the power converter; A power storage system comprising: The battery control device includes: a first process for charging a plurality of the batteries from a predetermined discharge state to a predetermined charge amount and recording the voltage of the batteries and the current of the battery string; a second process of charging the plurality of storage batteries, each of which has been charged to the predetermined charge amount, to a predetermined charge state; a third process of discharging the plurality of storage batteries that have been charged to the predetermined charge state by a predetermined discharge amount; a fourth process of charging the batteries that have been discharged by the predetermined discharge amount to the predetermined state of charge and recording the voltage of the batteries and the current of the battery string; a fifth process of generating voltage transition information indicating voltage transitions during charging of the plurality of storage batteries based on the voltages of the storage batteries and the currents of the storage battery strings recorded in the first process and the voltages of the storage batteries and the currents of the storage battery strings recorded in the fourth process; A storage system that performs the above.

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