Deterioration state evaluation device, power supply and demand system, deterioration state evaluation method, and deterioration state evaluation program

Abstract

Provided are a deterioration state evaluation device that is capable of accurately measuring a deterioration evaluation value by charging and discharging to a limit value, a power supply and demand system, a deterioration state evaluation method, and a deterioration state evaluation program. A deterioration state evaluation device (20) applied to a battery system comprises a selecting unit (21) for selecting a storage battery to be an evaluation target, and a measurement execution unit (22) for acquiring a deterioration evaluation value relating to a deterioration state of the storage battery, using a voltage value or a current value when charging / discharging of the storage battery of the evaluation target is controlled in accordance with a preset charge / discharge pattern, wherein the charge / discharge pattern includes at least one of a charge pattern for charging to a fully charged state and a discharge pattern for discharging to a charge amount lower limit state; the charge pattern includes an adjusted charge pattern for changing the charge current value or the charge voltage value stepwise or continuously in the vicinity of the full charge; and the discharge pattern includes an adjusted discharge pattern for changing the discharge current value or the discharge voltage value stepwise or continuously in the vicinity of the charge amount lower limit.

Description

Deterioration state evaluation device, power supply and demand system, deterioration state evaluation method, and deterioration state evaluation program

[0001] The present disclosure relates to a degradation state evaluation device, an electric power supply and demand system, a degradation state evaluation method, and a degradation state evaluation program.

[0002] A method for determining the degradation state of battery cells in a battery system using a storage battery is known. For example, in Patent Document 1, the storage battery is discharged until its charge rate reaches zero during a predetermined period, and then charged until its charge rate reaches its maximum, thereby measuring the charge capacity and discharge capacity of the storage battery. Patent Document 1 discloses calculating the degradation state based on the charge capacity and discharge capacity of the storage battery measured before use and the measured charge capacity and discharge capacity. In Patent Document 1, the degree of degradation of the storage battery is determined based on the degradation state, the internal resistance of the storage battery, and the usage time of the power storage device.

[0003] International Publication No. 2011 / 078215

[0004] However, the invention of Patent Document 1 does not consider the method of discharging the storage battery until the charging rate reaches 0 or charging it until the charging rate reaches its maximum. Furthermore, Patent Document 1 calculates the deterioration state based on past data, and is unable to obtain accurate current values.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a degradation state evaluation device, an electricity supply and demand system, a degradation state evaluation method, and a degradation state evaluation program that are capable of charging and discharging up to a limit value and accurately measuring a degradation evaluation value.

[0006] In order to solve the above problems, the present disclosure provides a degradation state evaluation device, an electric power supply and demand system, a degradation state evaluation method, and a degradation state evaluation program, which employ the following means: The degradation state evaluation device is applicable to a battery system including a plurality of storage batteries, and includes: a selection unit that selects a storage battery to be evaluated for its degradation state; and a measurement execution unit that acquires a degradation evaluation value relating to the degradation state of the storage battery by using a voltage value or a current value obtained when charging and discharging the storage battery to be evaluated according to a predetermined charge and discharge pattern, the charge and discharge pattern including at least one of a charge pattern for charging to a fully charged state and a discharge pattern for discharging to a lower charge limit state, the charge pattern including an adjusted charge pattern for changing a charge current value or a charge voltage value stepwise or continuously near a full charge, and the discharge pattern including an adjusted discharge pattern for changing a discharge current value or a discharge voltage value stepwise or continuously near the lower charge limit.

[0007] The power supply and demand system of the present disclosure includes a battery system including a plurality of storage batteries and the degradation state evaluation device described above.

[0008] The deterioration state evaluation method disclosed herein is a deterioration state evaluation method applied to a battery system having a plurality of storage batteries, and includes: a selection process for selecting a storage battery to be evaluated for evaluating the deterioration state of the battery; and a deterioration state evaluation process for acquiring a deterioration evaluation value related to the deterioration state of the storage battery using a voltage value or a current value when charging and discharging of the storage battery to be evaluated according to a predetermined charge and discharge pattern, wherein the charge and discharge pattern includes at least one of a charge pattern for charging to a fully charged state and a discharge pattern for discharging to a lower charge limit state, wherein the charge pattern includes an adjusted charge pattern for changing the charge current value or the charge voltage value stepwise or continuously near full charge, and the discharge pattern includes an adjusted discharge pattern for changing the discharge current value or the discharge voltage value stepwise or continuously near the lower charge limit, and the method is executed by a computer.

[0009] The degradation state evaluation program of the present disclosure causes a computer to execute the degradation state evaluation method described above.

[0010] According to the present disclosure, charging and discharging can be performed up to at least one of the vicinity of a fully charged state and the vicinity of a lower limit of the charge amount, thereby obtaining a more accurate degradation evaluation value.

[0011] 6 is an enlarged view of the time when the regulated charge shown in FIG. 6 is performed; FIG. 7 is an enlarged view of the time when the regulated discharge shown in FIG. 6 is performed; FIG. 8 is a diagram showing an example of the processing procedure of the degradation state evaluation device according to some embodiments of the present disclosure; FIG. 9 is a diagram showing an example of the time when the regulated charge shown in FIG. 6 is performed; FIG. 10 is a diagram showing an example of the time when the regulated discharge shown in FIG. 10 is performed; FIG. 11 is a diagram showing an example of the time when the regulated charge shown in FIG. 10 is performed; FIG. 12 is a diagram showing an example of the time when the regulated discharge shown in FIG. 10 is performed; FIG. 13 is a diagram showing an example of the processing procedure of the degradation state evaluation device according to some embodiments of the present disclosure; FIG. 14 is a diagram showing an example of the time when the regulated charge shown in FIG. 10 is performed;

[0012] [First embodiment] Hereinafter, an embodiment of a degradation state evaluation device, an electric power supply and demand system, a degradation state evaluation method, and a degradation state evaluation program according to the present disclosure will be described with reference to the drawings. Fig. 1 is a diagram showing a schematic configuration of an electric power supply and demand system according to some embodiments of the present disclosure. As shown in Fig. 1, an electric power supply and demand system 100 includes a battery system (ESS: Energy Storage System) 1 and a battery control system 10.

[0013] The battery system 1 is connected to a power grid 2 via a substation 3, and supplies and demands power to and from the power grid 2. The substation 3 and the battery system 1 are connected by an AC link 4. The battery system 1 includes multiple storage batteries 5 (5a to 5d). While FIG. 1 illustrates an example in which four storage batteries 5 are included, the number of storage batteries 5 is not limited. Hereinafter, when it is necessary to distinguish between the storage batteries 5a, 5b, etc., they will be referred to as storage batteries 5a, 5b, and when there is no need to distinguish between them, they will be simply referred to as storage batteries 5. The same applies to other configurations.

[0014] Each storage battery 5 is chargeable and dischargeable, and is configured, for example, as a battery string in which a plurality of unit batteries (cells) are connected in series. In this embodiment, a configuration in which a plurality of battery strings are connected in parallel may also be used. Each storage battery 5 may include a measurement unit (not shown) that measures various data (battery information) such as voltage value, current value, and temperature, and a battery management unit (BMU: Battery Management Unit) (not shown) that monitors the state of the storage battery 5 based on this measurement data. The configuration of the storage battery 5 may be any known technology and is not particularly limited.

[0015] Each storage battery 5 is connected to the AC link 4 via a power converter 7 (7a to 7d). The power converter 7 is, for example, an AC / DC converter. The power converter 7 controls the charging and discharging of the storage batteries 5 by operating based on, for example, individual power commands provided from the battery control system 10. Specifically, the power converter 7a controls the charging and discharging of the storage battery 5a, the power converter 7b controls the charging and discharging of the storage battery 5b, the power converter 7c controls the charging and discharging of the storage battery 5c, and the power converter 7d controls the charging and discharging of the storage battery 5d. During charging, the power converter 7 converts AC power from the power grid 2 into DC power and outputs it to the storage batteries 5. During discharging, the power converter 7 converts DC power from the storage batteries 5 into AC power and supplies it to the power grid 2.

[0016] The battery control system 10 is a control system that controls the battery system 1. The battery control system 10 is connected to the battery system 1 via, for example, a communication network, and is configured to be able to exchange information. The battery control system 10 may be a cloud server or a local system installed at the installation location of the battery system 1. The battery control system 10 is connected to a grid monitoring system 6 via the communication network. The grid monitoring system 6 is, for example, a central power supply control center of a power company, a higher-level energy management system (EMS), or the like. The grid monitoring system 6 determines a system power request to be made to the battery system 1 and transmits this system power request to the battery control system 10.

[0017] Next, a battery control system 10 according to the present embodiment will be described. FIG. 2 is a diagram showing an example of a hardware configuration of a battery control system according to some embodiments of the present disclosure. As shown in FIG. 2, the battery control system 10 is a computer and includes, for example, a CPU (Central Processing Unit: processor) 11, a main memory 12, a secondary storage 13, a communication interface 14, and the like. The battery control system 10 may also include an input device 15 that accepts input from a user, a display 16, and the like. These components are connected via a bus 18.

[0018] The main storage device 12 is composed of writable memory such as cache memory, RAM (Random Access Memory), etc., and is used as a work area for reading execution programs of the CPU 11 and writing processing data by the execution programs. The secondary storage device 13 is a non-transitory computer-readable storage medium. Examples of the secondary storage device 13 include magnetic disks such as HDDs (Hard Disk Drives), magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories such as SSDs (Solid State Drives).

[0019] Fig. 3 is a functional configuration diagram showing an example of functions of a battery control system according to some embodiments of the present disclosure. The battery control system 10 evaluates the state of degradation of each storage battery 5 while the battery system 1 is connected to the power grid 2, and controls the charging and discharging of each storage battery 5 using the evaluation results of the state of degradation. Specifically, as shown in Fig. 3, the battery control system 10 includes a state of degradation evaluation device 20. The battery control system 10 may also include a data management unit 30, a sharing adjustment rate setting unit 40, a power command setting unit 50, and a storage unit 60.

[0020] A series of processes for realizing the various functions described below is stored in the secondary storage device 13 (see FIG. 2) in the form of a program (e.g., a battery control program), for example, and the CPU 11 reads this program into the main storage device 12 and executes information processing and arithmetic operations to realize the various functions. The program may be pre-installed in the secondary storage device 13, provided in a state stored in another computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0021] The degradation state evaluation device 20 performs a degradation state evaluation to evaluate the degradation state of the storage battery 5. The degradation state evaluation is performed while the storage battery 5 is connected to the power grid 2. The degradation state evaluation is started when a preset start condition is satisfied. Examples of the start condition include when a predetermined period has elapsed since the previous degradation state evaluation, when the cumulative operating time since the previous degradation state evaluation reaches a predetermined time, or when a command to start the degradation state evaluation is input by the user. The start condition may be a combination of these. The cycle of the degradation state evaluation may be set so that the cycle becomes shorter as the degradation evaluation value decreases.

[0022] FIG. 4 is a functional configuration diagram illustrating an example of functions included in a degradation state evaluation device according to some embodiments of the present disclosure. As shown in FIG. 4 , the degradation state evaluation device 20 includes, for example, a selection unit 21, a measurement execution unit 22, a restoration control unit 23, and an evaluation value calculation unit 24. The selection unit 21 sequentially selects storage batteries 5 to be evaluated during degradation state evaluation. Specifically, during degradation state evaluation, the selection unit 21 selects one or more storage batteries 5 to be evaluated according to a predetermined algorithm. Then, after the measurement execution unit 22 (described later) finishes evaluating the degradation state of the storage battery 5 selected as the evaluation target, the selection unit 21 selects one or more storage batteries 5 to be evaluated next as the evaluation target. The selection unit 21 repeats the selection until all storage batteries 5a to 5d included in the battery system 1 have been selected as evaluation targets. For ease of explanation, this embodiment will be described with an example in which the selection is performed sequentially in the order of storage batteries 5a, 5b, 5c, and 5d. The storage batteries 5 other than the one to be evaluated are considered to be operational storage batteries because they are in operation in the battery system 1. The storage battery 5 to be evaluated is considered to be operated as an operational storage battery until it is selected as the one to be evaluated.

[0023] The measurement execution unit 22 controls the charging and discharging of the storage battery 5 to be evaluated in accordance with a preset charging and discharging pattern, and acquires the voltage value or current value at this time. Specifically, the measurement execution unit 22 issues a charging and discharging command in accordance with the predetermined charging and discharging pattern to the power conversion device 7 corresponding to the storage battery 5 to be evaluated. As a result, the power conversion device 7 is driven in accordance with the charging and discharging pattern, thereby realizing charging and discharging in accordance with the charging and discharging pattern.

[0024] The charge / discharge pattern may include, for example, a charge pattern for charging to a fully charged state and a discharge pattern for discharging to a lower charge limit state. The charge pattern may also include an adjusted charge pattern for gradually or continuously changing the charging current value near the fully charged state. By including such an adjusted charge pattern, the storage battery 5 can be brought closer to a fully charged state than when charging with only a constant current (e.g., 1 C).

[0025] The discharge pattern may include an adjusted discharge pattern that changes the discharge current value stepwise or continuously near the lower limit of the charge amount. By including such an adjusted discharge pattern, the storage battery 5 can be brought closer to the lower limit of the charge amount compared to discharging at a constant current (e.g., 1 C).

[0026] Fig. 5 is a diagram showing an example of the transition of the state of charge (SOC) when charge / discharge control is performed according to some embodiments of the present disclosure. Fig. 6 is a diagram showing an example of the transition of the battery voltage when charge / discharge control is performed using the same charge / discharge pattern as Fig. 5. In Figs. 5 and 6, the solid lines show an example of the transition of the storage battery 5 to be evaluated, and the dashed lines show an example of the transition of an arbitrary storage battery (operated storage battery) 5 other than the evaluation target. For example, the transition of the operational storage battery, which is an arbitrary storage battery 5 other than the evaluation target, represents the average value of the operational storage battery.

[0027] Fig. 7 is an enlarged view of the state of charge shown in Fig. 6 when the adjustment charge is being performed. Fig. 7 illustrates an example in which the current value is changed stepwise during the adjustment charge. Fig. 8 is an enlarged view of the state of discharge shown in Fig. 6 when the adjustment discharge is being performed. Fig. 8 illustrates an example in which the current value is changed stepwise during the adjustment discharge.

[0028] At time t0 in Figures 5 and 6, the measurement execution unit 22 performs a start process on the storage battery 5 to be evaluated selected by the selection unit 21. That is, evaluation (measurement) of the degradation state of the storage battery 5 to be evaluated begins at time t0. The storage battery 5 to be evaluated selected by the selection unit 21 is started to undergo start process from a state in which normal control is being performed as an operational storage battery, like the other storage batteries 5. Here, normal control refers to control in which the system power of the power grid 2 is shared among multiple storage batteries 5. If the storage battery 5 to be evaluated is charged while in normal control, the state may become unstable. Therefore, as a start process, the storage battery 5 to be evaluated is placed in a charge / discharge stop state in which charging / discharging is stopped, and a settling period is performed by waiting. This makes it possible to stabilize the charge rate of the storage battery 5.

[0029] The state of charge (SOC) of the storage battery 5 under evaluation at time t0 is approximately the same as the state of charge (SOC) of the operational storage battery, as shown in Figure 5. The battery voltage of the storage battery 5 under evaluation at time t0 is approximately the same as the battery voltage of the operational storage battery, as shown in Figure 6.

[0030] 5 and 6 , charging processing is started at time t1, and CC charging (Constant Current charging) is performed from time t1 to t2. As shown in FIG. 5 , CC charging causes the SOC of the storage battery 5 under evaluation to steadily increase. As shown in FIG. 6 , CC charging causes charging at a constant current while gradually increasing the voltage, so the battery voltage of the storage battery 5 under evaluation also steadily increases. CC charging is performed until the battery voltage reaches the maximum battery voltage.

[0031] When the battery voltage reaches the maximum battery voltage at time t2 in Figures 5 and 6, adjusted charging begins, and adjusted charging is performed from time t2 to t3. As shown in Figure 6, the storage battery 5 under evaluation is charged while gradually increasing its voltage. As the battery voltage approaches the maximum battery voltage V_max, the degradation state evaluation device 20 reduces the rate of the charging current value and again increases the voltage while charging. This process is repeated to perform adjusted charging. As shown in Figure 5, the SOC of the storage battery 5 under evaluation continues to increase steadily as adjusted charging is performed, but the rate of increase decreases as the maximum SOC (time t3) is approached.

[0032] Conditioned charging will be described with reference to Fig. 7. The vertical axis of Fig. 7 represents battery voltage, the horizontal axis represents time, and the solid line represents the voltage of the storage battery 5 under evaluation. Fig. 7 is an enlarged view of Fig. 6 when the battery voltage of the storage battery 5 under evaluation approaches the maximum battery voltage V_max.

[0033] FIG. 7 shows the transition of the battery voltage of the storage battery 5 under evaluation when the rate of the charging current value of CC charging is decreased by 0.2 increments. CC charging is performed at a rate of 1 C. When the battery voltage approaches and almost reaches the maximum battery voltage V_max, the degradation state evaluation device 20 starts conditioning charging, pauses charging, and then decreases the charging current rate by 0.2 to 0.8 C, at which point CC charging is performed at a rate of 0.8 C. Conditioning charging is performed by repeating the same process at 0.6 C, 0.4 C, and 0.2 C. Conditioning charging is stopped when CC charging is performed at a rate of 0.2 C and the battery voltage reaches the maximum battery voltage V_max. During conditioning charging, the charging current value is controlled so that the battery voltage does not exceed the maximum battery voltage V_max, which is a threshold value. The charging current value is also controlled so that charging is stopped when the battery voltage reaches the maximum battery voltage V_max, which is the threshold value. In this way, it is preferable to gradually reduce the charging current value during adjusted charging so that the battery voltage (open circuit voltage) when the charging current is stopped approaches the value of SOC 100% (fully charged state) as closely as possible, and adjusted charging may also be performed as multi-stage CC charging.

[0034] Although an example in which the charging current is changed stepwise has been shown here, this is not limiting. For example, if the power conversion device 7 can charge the storage battery 5 while maintaining the maximum battery voltage, CC-CV charging may be used. That is, charging may be performed by continuously changing the current until a predetermined charging voltage set near the maximum battery voltage is reached, and after the predetermined charging voltage is reached, the current may be switched to CV and charging may be performed until the battery is fully charged while avoiding an overvoltage charging state.

[0035] The battery voltage (open circuit voltage) when the charging current is stopped is preferably a value of 100% SOC, but can be other values. For example, if the SOC is 80% and a capacity test is performed for 80% SOC from 80% to 0%, the full charge capacity of the test result can be converted to the result of a capacity test for 100% SOC by multiplying it by 100% / 80% (= 1.25).

[0036] Settling begins at time t3 in Figures 5 and 6 and continues from time t3 to t4. As shown in Figure 5, the SOC of the storage battery 5 under evaluation is maintained at a constant value close to the maximum SOC (fully charged), SOC_max. As shown in Figure 6, the battery voltage of the storage battery 5 under evaluation is maintained at a substantially constant value slightly lower than the maximum battery voltage V_max. While current is flowing, fluctuations in voltage may occur depending on the current value. To prevent this from occurring, charging is stopped and settling is performed.

[0037] Discharge processing begins at time t4 in Figures 5 and 6 , and CC discharge (Constant Current discharge) is performed from time t4 to t5. As shown in Figure 5 , CC discharge causes the SOC of the storage battery 5 under evaluation to decrease sharply to the right. As shown in Figure 6 , CC discharge causes discharge at a constant current while gradually lowering the voltage, so the battery voltage of the storage battery 5 under evaluation also decreases sharply to the right. CC discharge is performed until the battery voltage reaches the minimum battery voltage.

[0038] When the battery voltage reaches the minimum battery voltage at time t5 in FIGS. 5 and 6 , regulated discharge begins, and regulated discharge is performed from time t5 to t6. As shown in FIG. 6 , the storage battery 5 to be evaluated gradually decreases its voltage while discharging. When the battery voltage approaches the minimum battery voltage V_min, the degradation state evaluation device 20 reduces the rate of the discharge current and again decreases the voltage while discharging. This process is repeated to perform regulated discharge. In regulated discharge, the discharge current value is controlled so that discharging stops when the battery voltage reaches the minimum battery voltage V_min, which is a threshold value. As shown in FIG. 5 , regulated discharge causes the SOC to continue to decrease steadily, but the rate of decrease decreases as the battery approaches the minimum SOC (time t6). Regulated discharge is not necessarily required; only CC discharge may be performed.

[0039] The regulated discharge will be described with reference to Fig. 8. The vertical axis of Fig. 8 represents battery voltage, the horizontal axis represents time, and the solid line represents the voltage of the storage battery 5 under evaluation. Fig. 8 is an enlarged view of Fig. 6 when the battery voltage of the storage battery 5 under evaluation approaches the minimum battery voltage V_min.

[0040] FIG. 8 shows the transition of the battery voltage of the storage battery 5 under evaluation when the discharge current rate of CC discharge is reduced by 0.2 increments. CC discharge is performed at a rate of 1 C. When the battery voltage approaches and reaches the minimum battery voltage V_min, the degradation state evaluation device 20 starts regulated discharge. After suspending discharge, the discharge current rate is reduced by 0.2 to 0.8 C, and CC discharge is performed at a rate of 0.8 C. Regulated discharge is performed by repeating the same process at 0.6 C, 0.4 C, and 0.2 C. Regulated discharge is stopped when CC discharge is performed at a rate of 0.2 C and the battery voltage reaches approximately the minimum battery voltage V_min. In regulated discharge, the discharge current value is controlled so that discharge is stopped when the battery voltage reaches the minimum battery voltage V_min, which is a threshold value. In this manner, it is preferable to gradually reduce the discharge current value during regulated discharge so that the battery voltage (open circuit voltage) at the time of discharge current stop approaches the value at 0% SOC as much as possible. Regulated discharge may also be performed as multi-stage CC discharge.

[0041] Although an example in which the discharge current is changed in stages has been shown here, CC-CV discharge may also be used if the power conversion device 7 can discharge while maintaining the minimum battery voltage of the storage battery 5. That is, discharge may be performed by continuously changing the current until a predetermined discharge voltage set near the minimum battery voltage is reached, and after the predetermined discharge voltage is reached, the current may be switched to CV and discharge may be performed down to the minimum battery voltage.

[0042] The battery voltage (open circuit voltage) when the discharge current is stopped is preferably a value of 0% SOC, but may be other values. For example, if the SOC is 20% and a capacity test is performed for 80% SOC from 100% to 20%, the full charge capacity of the test result can be converted to the result of a capacity test for 100% SOC by multiplying it by 100% / 80% (= 1.25).

[0043] 5 and 6 , settling begins at time t6 and continues from time t6 to t7. As shown in Fig. 5 , the SOC of the storage battery 5 under evaluation is maintained at a constant value close to the minimum SOC (lower charge limit), SOC_min. As shown in Fig. 6 , the battery voltage of the storage battery 5 under evaluation is maintained at a constant value slightly higher than the minimum battery voltage V_min.

[0044] After the measurement execution unit 22 finishes measuring, i.e., after the charge / discharge control based on the predetermined charge / discharge pattern is completed, the restoration control unit 23 controls the charge / discharge of the storage battery under evaluation (e.g., 5a) so as to bring the state of charge ratio of the storage battery under evaluation closer to the state of charge ratio of the operational storage batteries (e.g., 5b-5d). Then, if the difference between the state of charge ratio of the storage battery under evaluation (e.g., 5a) and the state of charge ratio of any operational storage battery (e.g., 5b-5d) is within a predetermined range when a predetermined condition is satisfied, the restoration control unit 23 restores the storage battery under evaluation as an operational storage battery (see the restoration process in FIGS. 5 and 6). For example, the restoration control unit 23 may restore the storage battery under evaluation as an operational storage battery when the difference between the average cell voltage of the storage battery under evaluation and the average value of the average cell voltages of the operational storage batteries is within a predetermined range. Instead of the average cell voltage, the state of charge ratio may be used.

[0045] 5 and 6 , the recovery process is initiated at time t7 and continues from time t7 to time t8. As shown in FIG. 6 , the evaluation (measurement) of the degradation state of the storage battery 5 under evaluation ends at time t7. The storage battery 5 under evaluation is charged and discharged (in this embodiment, charging, and further CC charging) so that the SOC of the storage battery 5 under evaluation approaches the SOC of the operating storage battery shown by the dashed line. As shown in FIG. 6 , the battery voltage of the storage battery 5 under evaluation increases steadily because the battery is charged at a constant current while increasing the voltage through CC charging.

[0046] When the difference between the state of charge of the storage battery 5 under evaluation and the state of charge of the operational storage battery satisfies a predetermined condition around time t8 in FIG. 5 , the storage battery 5 under evaluation is restored as an operational storage battery. As shown in FIG. 5 , the SOC of the storage battery 5 under evaluation at time t8 is approximately the same as the SOC of the operational storage battery. As shown in FIG. 6 , the battery voltage of the storage battery 5 under evaluation at time t8 is approximately the same as the battery voltage of the operational storage battery. For example, the restoration control unit 23 may restore the storage battery 5 under evaluation as an operational storage battery when the difference between the average cell voltage of the storage battery 5 under evaluation and the average value of the average cell voltages of the operational storage batteries satisfies a predetermined condition. The state of charge (SOC) may be used instead of the average cell voltage.

[0047] Settling begins at time t8 in Figures 5 and 6 and continues from time t8 to t9. As shown in Figure 5, the SOC of the storage battery 5 under evaluation is set to a value close to the SOC of the operating storage battery. As shown in Figure 6, the battery voltage of the storage battery 5 under evaluation is set to a value close to the battery voltage of the operating storage battery. Here, settling is performed to reset various control parameters in order to return the storage battery 5 under evaluation to normal control.

[0048] The evaluation value calculation unit 24 calculates a degradation evaluation value that evaluates the degradation state of the storage battery 5 to be evaluated based on the current value or voltage value when charge / discharge control is performed by the measurement execution unit 22. For example, the evaluation value calculation unit 24 receives battery information (current value, voltage value, temperature, etc.) from the storage battery 5 to be evaluated, and calculates a degradation evaluation value based on the received battery information.

[0049] The degradation evaluation value is, for example, an evaluation value that indicates a decrease in the current full charge capacity of the storage battery 5 relative to the initial full charge capacity, and an example thereof is the SOH (State of Health). The evaluation value calculation unit 24 calculates the latest full charge capacity (Ah) by, for example, integrating the current value when the storage battery 5 to be evaluated is changed from a fully charged state to a lower charge limit state, or from the lower charge limit state to a fully charged state. The evaluation value calculation unit 24 then calculates the SOH by dividing the latest full charge capacity by the full charge capacity at the start (initial) of operation of the battery system 1. The method for evaluating the degradation state of the battery is not limited to the above example. For example, any known technology for evaluating the degradation state of a battery can be appropriately adopted.

[0050] For example, the latest full charge capacity is calculated as the time integral of the discharge current value when the evaluation value calculation unit 24 changes the storage battery 5 to be evaluated from the fully charged state to the lower charge limit state (the period from time t4 to t6 in FIGS. 5 and 6 ). The latest full charge capacity of the storage battery 5 to be evaluated may be calculated by correcting the time integral of the discharge current value using at least one of a temperature correction coefficient, a current correction coefficient, and an SOC correction coefficient for the period from time t4 to t6 in FIGS. 5 and 6 .

[0051] After calculating the degradation evaluation values ​​for all of the storage batteries 5a to 5d, the evaluation value calculation unit 24 outputs degradation evaluation information that associates the identification information of each storage battery with the degradation evaluation value to the data management unit 30 (see FIG. 3). The degradation evaluation information may also include time information, battery information of each storage battery 5a to 5d acquired by the measurement execution unit 22, and the like.

[0052] Next, the operation of the degradation state evaluation device 20 according to this embodiment will be described. Fig. 9 is a diagram showing an example of a processing procedure of the degradation state evaluation device according to some embodiments of the present disclosure. The processing shown below is started when a preset condition for starting degradation state evaluation is satisfied. For convenience of explanation, the following description will be given taking as an example a case where degradation state evaluation is performed on the storage batteries 5a, 5b, 5c, and 5d in that order.

[0053] First, in step SA1, the selection unit 21 of the degradation state evaluation device 20 selects a storage battery 5 a to be evaluated for degradation state evaluation. In step SA2, the measurement execution unit 22 controls the charge and discharge of the storage battery 5 a to be evaluated in accordance with a preset charge and discharge pattern, and acquires battery information such as the voltage value, current value, and temperature of the storage battery 5 a from the battery system 1.

[0054] When the charge / discharge control of the storage battery 5a to be evaluated is completed, in step SA3, the evaluation value calculation unit 24 calculates a deterioration evaluation value from the acquired battery information.

[0055] In step SA4, the degradation state evaluation device 20 stores the identification information "#1" of the storage battery 5a to be evaluated and the degradation evaluation value in association with each other in its internal memory.

[0056] In step SA5, a restoration process is performed. In the restoration process, the charge and discharge of the storage battery 5a under evaluation is controlled so that the state of charge (SOC) of the storage battery 5a under evaluation approaches the state of charge (SOC) of the operational storage batteries 5b to 5d. When the state of charge of the storage battery 5a under evaluation satisfies a predetermined condition defined in relation to the state of charge of the operational storage batteries, the restoration control unit 23 restores the storage battery 5a under evaluation as an operational storage battery. When the difference between the average cell voltage of the storage battery 5a under evaluation and the average value of the average cell voltages of the operational storage batteries 5b to 5d satisfies a predetermined condition.

[0057] In step SA6, it is determined whether all of the storage batteries 5a to 5d have been selected as the storage batteries to be evaluated. In this case, since all of the storage batteries 5a to 5d have not been selected (SA6: NO), the process returns to step SA1, and the unselected storage battery 5b is selected as the storage battery to be evaluated. In step SA1, a degradation state evaluation is performed for the storage battery 5b. Here, if the storage battery 5b has been selected as the storage battery to be evaluated, the operating storage batteries are the storage batteries 5a, 5c, and 5d.

[0058] Similar processing is performed for storage batteries 5c and 5d, and if it is determined in step SA6 that all storage batteries 5a to 5d have been selected for evaluation (SA6: YES), deterioration evaluation information that associates the identification information #1 to #4 of each storage battery 5a to 5d with the deterioration evaluation value is output (SA7), and processing is terminated.

[0059] As described above, according to this embodiment, charging and discharging can be performed to at least one of near full charge and near the lower limit of charge, thereby obtaining a more accurate state of health (SOH). Since the current SOH (deterioration evaluation value) of a storage battery to be evaluated selected from the operating storage batteries is obtained, the SOH of the storage battery to be evaluated can be obtained without stopping the operation of the operating storage battery. By performing this process sequentially for each storage battery, the SOH of multiple storage batteries can be obtained.

[0060] Although the battery system 1 of the present embodiment is connected to the AC link 4, it may be connected to a DC link. FIG. 10 is a diagram showing a schematic configuration of a power supply and demand system according to some embodiments of the present disclosure. In the above-described power supply and demand system 100, the power conversion device 7 is an AC / DC converter, and the battery system 1 is connected to the AC link 4 via this power conversion device 7. In contrast, as shown in FIG. 10 , in a power supply and demand system 100a, the battery system 1a may be connected to a DC link 8 via a power conversion device 7′ (7a′ to 7d′) that is a DC / DC converter. In this case, the DC link 8 and the substation 3 are connected via an AC / DC converter 9. Even when the battery system 1 is connected to the DC link 8, the degradation state evaluation device 20 of the battery control system 10a of the present disclosure performs similar processing.

[0061] Second Embodiment A second embodiment of the present disclosure will be described with reference to the drawings. FIG. 11 is a diagram illustrating a control flow of a degradation state evaluation device according to some embodiments of the present disclosure. FIG. 12 is a diagram illustrating the relationship between power and time of a storage battery according to some embodiments of the present disclosure. The vertical axis of FIG. 12 represents the power (kW) of the storage batteries 5, and the horizontal axis represents time, showing the transition of power in the first storage battery group and the second storage battery group. This embodiment differs from the first embodiment described above in that the first storage battery group and the second storage battery group each consisting of the same number of storage batteries 5 are selected, but is otherwise similar to the first embodiment. Here, differences from the first embodiment will be mainly described, and duplicated descriptions of parts that are the same as those in the first embodiment will be omitted. The same reference numerals are used for parts that are the same as those in the first embodiment.

[0062] 11 , the selection unit 21 extracts two groups of arbitrary storage batteries 5. The selection by the selection unit 21 does not matter how many storage batteries 5 are included in each group, as long as the first storage battery group and the second storage battery group are selected and each group is configured with the same number of storage batteries 5. In this embodiment, for example, the number of storage batteries 5 included in the first storage battery group and the second storage battery group is assumed to be one.

[0063] In step S302, the measurement execution unit 22 of the degradation state evaluation device 20 performs charge / discharge control to adjust the SOCs of the first storage battery group and the second storage battery group in order to acquire the degradation evaluation values.

[0064] At time t1 in FIG. 12 , the SOCs of the first and second storage battery groups are adjusted. At time t1, both the first and second storage battery groups are in a zero-power state. At time t1, the first storage battery group starts charging and is charged until it is nearly fully charged. Meanwhile, at time t1, the second storage battery group starts discharging and is discharged so that the sum of the charge amount of the first storage battery group and the discharge amount of the second storage battery group approaches zero, corresponding to the charging of the first storage battery group. Charging of the first storage battery group and discharging of the second storage battery group continue until time t2. Before time t1, charging and discharging of the first and second storage battery groups may be stopped and settling may be performed, and then the first and second storage battery groups may be brought to a zero-power state at time t1.

[0065] 11 , the measurement execution unit 22 of the degradation state evaluation device 20 performs charge / discharge control to evaluate the SOH of the first storage battery group. Specifically, the first storage battery group is discharged and the second storage battery group is charged. The evaluation value calculation unit 24 acquires the degradation evaluation value (SOH) of the first storage battery group.

[0066] At time t2 in Fig. 12 , charging and discharging are performed for the first and second storage battery groups. At time t2, the first storage battery group starts discharging and continues discharging until it approaches a lower charge limit. Meanwhile, at time t2, the second storage battery group starts charging and continues charging until it approaches a fully charged state so that the sum of the discharged amount of the first storage battery group and the charged amount of the second storage battery group approaches zero. Discharging of the first storage battery group and charging of the second storage battery group continue until time t3. The evaluation value calculation unit 24 of the degradation state evaluation device 20 calculates a degradation evaluation value (SOH) for the first storage battery group from the latest full charge capacity of the first storage battery group during the period from time t2 to t3 and the full charge capacity of the first storage battery group at the start (initial) of operation.

[0067] In step S304 of FIG. 11, the measurement execution unit 22 of the degradation state evaluation device 20 temporarily suspends and settles the SOH (degradation evaluation value) measurement of the first storage battery group and the second storage battery group.

[0068] At time t3 in Fig. 12, the first and second storage battery groups are settling. The first and second storage battery groups are placed in a charging / discharging stopped state and are placed on standby for a certain period of time (the period from time t3 to time t4).

[0069] 11 , the measurement execution unit 22 of the degradation state evaluation device 20 performs charge / discharge control to evaluate the SOH of the second storage battery group. Specifically, the second storage battery group is discharged and the first storage battery group is charged. The evaluation value calculation unit 24 acquires the degradation evaluation value (SOH) of the second storage battery group.

[0070] At time t4 in Fig. 12 , charging and discharging are performed on the first and second storage battery groups. At time t4, discharging of the second storage battery group begins, and is continued until the second storage battery group approaches a lower charge limit. Meanwhile, at time t3, charging of the first storage battery group begins, and is continued until the first storage battery group approaches a fully charged state so that the sum of the charge amount of the first storage battery group and the discharge amount of the second storage battery group approaches zero. Discharging of the second storage battery group and charging of the first storage battery group continue until time t5. The evaluation value calculation unit 24 of the degradation state evaluation device 20 calculates a degradation evaluation value (SOH) of the second storage battery group from the latest full charge capacity of the second storage battery group during the period from time t4 to t5 and the full charge capacity of the second storage battery group at the start (initial) of operation.

[0071] In step S306 of FIG. 11, the measurement execution unit 22 of the degradation state evaluation device 20 temporarily suspends and settles the SOH (degradation evaluation value) measurement of the first storage battery group and the second storage battery group.

[0072] At time t5 in Fig. 12, the first and second storage battery groups are stabilized. The first and second storage battery groups are placed in a charging / discharging stopped state and are placed on standby for a certain period of time (the period from time t3 to time t4).

[0073] In step S307 of Figure 11, the restoration control unit 23 of the degradation state evaluation device 20 performs charge / discharge control to adjust the SOC of the first storage battery group and the second storage battery group in order to restore them to operational storage batteries.

[0074] At time t6 in Fig. 12 , the SOCs of the first storage battery group and the second storage battery group are adjusted. At time t6, the first storage battery group is in a charged state relative to time t1, and the second storage battery group is in a discharged state relative to time t1. Therefore, the restoration control unit 23 of the degradation state evaluation device 20 controls the first storage battery group and the second storage battery group so that the SOCs of the first storage battery group and the second storage battery group approach the SOC of the operational storage batteries. The restoration control unit 23 may also control the first storage battery group and the second storage battery group so that the average cell voltages of the first storage battery group and the second storage battery group approach the average value of the average cell voltages of the operational storage batteries.

[0075] In step S308 of FIG. 11 , the restoration control unit 23 of the degradation state evaluation device 20 restores the first storage battery group and the second storage battery group to normal operation as operational storage batteries.

[0076] 12 , the restoration control unit 23 of the degradation state evaluation device 20 restores the first storage battery group and the second storage battery group as operational batteries when the difference between the SOC of the first storage battery group and the second storage battery group and the SOC of the operational batteries satisfies a predetermined condition (for example, when it is within a predetermined range). The restoration control unit 23 may restore the first storage battery group and the second storage battery group as operational batteries when the difference between the average cell voltage of the first storage battery group and the second storage battery group and the average value of the average cell voltage of the operational batteries satisfies a predetermined condition (when it is within a predetermined range).

[0077] In this way, for the first storage battery group and the second storage battery group each consisting of the same number of storage batteries 5, charging and discharging are controlled according to a reversed charging and discharging pattern in which charging and discharging are reversed from one of the charging and discharging patterns so that the sum of the charging and discharging amounts of the first storage battery group and the second storage battery group approaches zero, and the SOH is measured. This reduces the impact on the charging and discharging amount of the entire battery system 1, and allows the SOH of each storage battery group to be measured while operating the battery system 1. The SOH of each storage battery group can be measured while suppressing voltage fluctuations in the battery system 1.

[0078] <Additional Notes> The degradation state evaluation device, the power supply and demand system, the degradation state evaluation method, and the degradation state evaluation program described in the above-described embodiments can be understood, for example, as follows.

[0079] A degradation state evaluation device according to a first aspect of the present disclosure is a degradation state evaluation device (20) that is applied to a battery system (1) that includes a plurality of storage batteries (5), and includes: a selection unit (21) that selects a storage battery to be evaluated for evaluating the degradation state of the battery; and a measurement execution unit (22) that acquires a degradation evaluation value related to the degradation state of the storage battery by using a voltage value or a current value when charging and discharging of the storage battery to be evaluated according to a predetermined charge and discharge pattern, wherein the charge and discharge pattern includes at least one of a charge pattern for charging to a fully charged state and a discharge pattern for discharging to a lower charge limit state, the charge pattern includes an adjusted charge pattern for changing a charge current value or a charge voltage value stepwise or continuously near a full charge, and the discharge pattern includes an adjusted discharge pattern for changing a discharge current value or a discharge voltage value stepwise or continuously near the lower charge limit.

[0080] This allows charging and discharging to at least either near full charge or near the lower limit of charge, resulting in a more accurate state of health (SOH) rating. By obtaining the current degradation rating of a battery selected from the operational batteries to be evaluated, the SOH of the battery to be evaluated can be obtained without stopping the operation of the operational batteries. By performing this process sequentially for each battery, the SOH of multiple batteries can be obtained.

[0081] The degradation state evaluation device according to the second aspect of the present disclosure may be configured in the first aspect such that the charging current value or the charging voltage value of the adjusted charging pattern is set to gradually decrease.

[0082] Multi-stage CC charging or multi-stage CV charging can be performed to charge the battery to near full charge.

[0083] The degradation state evaluating device of the third aspect of the present disclosure may be configured such that in the first or second aspect, the discharge current value or the discharge voltage value of the adjusted discharge pattern is set to gradually decrease.

[0084] Multi-stage CC discharge or multi-stage CV discharge can be performed to discharge close to the lower limit of the charge amount.

[0085] The deterioration state evaluation device of the fourth aspect of the present disclosure may be, in any of the first to third aspects, equipped with a restoration control unit (23) that controls the storage battery to be evaluated so that the charge state of the storage battery to be evaluated approaches the charge state of an operational storage battery, which is a storage battery other than the storage battery to be evaluated, after charge / discharge control based on the charge / discharge pattern is completed, and restores the storage battery to be evaluated as the operational storage battery when the charge state of the storage battery to be evaluated and the charge state of the operational storage battery satisfy predetermined conditions.

[0086] After the degradation state evaluation is completed, the storage battery being evaluated is returned to normal control, which is the same as that of the operational storage battery, so that it can be operated as part of the battery system after the evaluation is completed. When returning, the state of charge of the storage battery being evaluated can be brought closer to that of the operational storage battery, and the battery can be steadily returned to normal control.

[0087] A deterioration state evaluation device of a fifth aspect of the present disclosure may, in any of the first to fourth aspects, select a first storage battery group and a second storage battery group consisting of the same number of storage batteries, control charging and discharging of the first storage battery group in accordance with the charge and discharge pattern, and control charging and discharging of the second storage battery group in accordance with a reverse charge and discharge pattern in which the charge and discharge pattern of the first storage battery group is reversed so that the sum of the charge and discharge amounts of the first storage battery group and the second storage battery group approaches zero, and obtain the deterioration evaluation value of each of the storage batteries of the first storage battery group and the second storage battery group.

[0088] The degradation state of each battery group can be evaluated while the battery system is operating, minimizing the impact on the charge / discharge amount of the entire battery system. The degradation state of each battery group can be evaluated while minimizing voltage fluctuations in the battery system.

[0089] A sixth aspect of the present disclosure provides an electric power supply and demand system including a battery system including a plurality of storage batteries and the degradation state evaluation device according to any one of the first to fifth aspects.

[0090] A seventh aspect of the present disclosure provides a degradation state evaluation method that is applicable to a battery system having a plurality of storage batteries, and includes: a selection step of selecting a storage battery to be evaluated for evaluating the degradation state of the battery; and a measurement execution step of acquiring a degradation evaluation value related to the degradation state of the storage battery using a voltage value or a current value obtained when charging and discharging of the storage battery to be evaluated according to a predetermined charge and discharge pattern, wherein the charge and discharge pattern includes at least one of a charge pattern for charging to a fully charged state and a discharge pattern for discharging to a lower charge limit state, wherein the charge pattern includes an adjusted charge pattern for changing a charge current value or a charge voltage value stepwise or continuously near a full charge, and the discharge pattern includes an adjusted discharge pattern for changing a discharge current value or a discharge voltage value stepwise or continuously near the lower charge limit, and the method is executed by a computer.

[0091] A degradation state evaluation program according to an eighth aspect of the present disclosure causes a computer to execute the degradation state evaluation method according to the seventh aspect.

[0092] Although the present disclosure has been described using embodiments, the technical scope of the present disclosure is not limited to the scope described in the above embodiments. For example, although CC charging is performed in the embodiments of the present disclosure, CV charging (constant voltage charging) may be performed instead. Furthermore, CV discharging (constant voltage discharging) may be performed instead of CC discharging.

[0093] DESCRIPTION OF SYMBOLS 1, 1a: Battery system 2: Power system 3: Substation 4: AC link 5 (5a to 5d): Storage battery 6: System monitoring system 7 (7a to 7d): Power conversion device 7' (7a' to 7d'): Power conversion device 8: DC link 9: AC / DC converter 10, 10a: Battery control system 11: CPU 12: Main memory device 13: Secondary memory device 14: Communication interface 15: Input device 16: Display 20: Degradation state evaluation device 21: Selection unit 22: Measurement execution unit 23: Recovery control unit 24: Evaluation value calculation unit 30: Data management unit 40: Sharing adjustment rate setting unit 50: Power command setting unit 60: Storage unit 100, 100a: Power supply and demand system

Claims

1. A degradation state evaluation device applicable to a battery system having a plurality of storage batteries, comprising: a selection unit which selects a storage battery to be evaluated for evaluating the degradation state of the battery; and a measurement execution unit which obtains a degradation evaluation value relating to the degradation state of the storage battery by using a voltage value or a current value when charging and discharging of the storage battery to be evaluated according to a preset charge and discharge pattern, wherein the charge and discharge pattern includes at least one of a charge pattern for charging to a fully charged state and a discharge pattern for discharging to a lower charge limit state, the charge pattern includes an adjusted charge pattern for changing a charge current value or a charge voltage value stepwise or continuously near a full charge, and the discharge pattern includes an adjusted discharge pattern for changing a discharge current value or a discharge voltage value stepwise or continuously near a lower charge limit.

2. The degradation state evaluation device according to claim 1, wherein the charging current value or the charging voltage value of the adjusted charging pattern is set to gradually decrease.

3. The degradation state evaluation device according to claim 1, wherein the discharge current value or the discharge voltage value of the adjusted discharge pattern is set to gradually decrease.

4. The deterioration state evaluation device of claim 1, further comprising a restoration control unit that controls the storage battery to be evaluated so that the state of charge of the storage battery to be evaluated approaches the state of charge of an operational storage battery, which is a storage battery other than the storage battery to be evaluated, after completion of charge and discharge control based on the charge and discharge pattern, and restores the storage battery to be evaluated as the operational storage battery when the state of charge of the storage battery to be evaluated and the state of charge of the operational storage battery satisfy predetermined conditions.

5. The deterioration state evaluation device according to claim 2, which selects a first storage battery group and a second storage battery group each consisting of an equal number of the storage batteries, controls charging and discharging of the first storage battery group in accordance with the charge and discharge pattern, and controls charging and discharging of the second storage battery group in accordance with a reverse charge and discharge pattern in which charging and discharging are reversed from the charge and discharge pattern of the first storage battery group so that a sum of a charge and discharge amount of the first storage battery group and a charge and discharge amount of the second storage battery group approaches zero, and obtains the deterioration evaluation value of each of the storage batteries of the first storage battery group and the second storage battery group.

6. An electric power supply and demand system comprising: a battery system having a plurality of storage batteries; and the degradation state evaluation device according to claim 1.

7. A degradation state evaluation method applied to a battery system having a plurality of storage batteries, comprising: a selection step of selecting a storage battery to be evaluated for evaluating the degradation state of the battery; and a measurement execution step of acquiring a degradation evaluation value relating to the degradation state of the storage battery by using a voltage value or a current value when charging and discharging of the storage battery to be evaluated according to a preset charge and discharge pattern, wherein the charge and discharge pattern includes at least one of a charge pattern for charging to a fully charged state and a discharge pattern for discharging to a lower charge limit state, the charge pattern includes an adjusted charge pattern for changing a charge current value or a charge voltage value stepwise or continuously near a full charge, and the discharge pattern includes an adjusted discharge pattern for changing a discharge current value or a discharge voltage value stepwise or continuously near a lower charge limit. A degradation state evaluation method executed by a computer.

8. A degradation state evaluation program for causing a computer to execute the degradation state evaluation method according to claim 7.

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