Control device for electrical power storage system, electrical power storage system, control method for electrical power storage system, and program

Abstract

This control device for an electrical power storage system comprises: a life prediction unit for predicting a consumption life of a storage battery and a converter, respectively, according to a load factor of charge / discharge power allocated to respective storage battery units; a cost loss prediction unit for predicting, on the basis of the consumption life, consumption costs of the storage battery and the converter, respectively, according to the load factor; a load factor calculation unit for calculating a first load factor for each of the storage battery units on the basis of the state of the storage battery; and a load factor adjustment unit for adjusting the first load factor so as to minimize the total cost loss which is obtained by totaling the consumption costs of all the storage batteries and all the converters.

Description

Control device for power storage system, power storage system, control method for power storage system, and program

[0001] This disclosure relates to a power storage system control device, a power storage system, a power storage system control method, and a program. This application claims priority to Japanese Patent Application No. 2023-211741 filed on December 15, 2023, the contents of which are incorporated herein by reference.

[0002] Patent Document 1 describes a technique for equally allocating loads to each converter in a system in which a plurality of power conversion devices (hereinafter also simply referred to as converters) are connected.

[0003] Japanese Patent Application Publication No. 11-296244

[0004] In an energy storage system (ESS) in which multiple storage battery units, each having a storage battery and a converter, are arranged in parallel, control is generally performed to extend the life of the storage battery, which is more expensive than the converter. In such cases, little consideration is given to the life of the relatively inexpensive converter, which may result in the converter deteriorating.

[0005] An object of the present disclosure is to provide a control device for a power storage system, a power storage system, a control method for a power storage system, and a program that can extend the life of both the storage battery and the converter and reduce operating costs.

[0006] According to one aspect of the present disclosure, a control device for a power storage system is a control device for a power storage system in which a plurality of storage battery units, each having a storage battery and a converter for charging and discharging power for the storage battery, are connected in parallel via a DC bus, and includes: a life prediction unit that predicts a consumption life of each of the storage batteries and the converter according to a load rate of the charging and discharging power assigned to each of the storage battery units; a cost loss prediction unit that predicts a consumption cost of each of the storage batteries and the converter according to the load rate based on the consumption life; a load rate calculation unit that calculates a first load rate for each of the storage battery units based on a state of the storage batteries; and a load rate adjustment unit that adjusts the first load rate so that a total cost loss, which is the sum of the consumption costs of all of the storage batteries and the converters, is minimized.

[0007] According to one aspect of the present disclosure, a power storage system includes a plurality of storage battery units each having a storage battery and a converter that converts the voltage of charging / discharging power for the storage battery, and the above-described control device.

[0008] According to one aspect of the present disclosure, a control method for a power storage system is a control method for a power storage system in which a plurality of storage battery units, each having a storage battery and a converter that converts the voltage of charging and discharging power to the storage battery, are connected in parallel via a DC bus, and includes the steps of: predicting a consumption life of each of the storage batteries and the converter according to a load rate of the charging and discharging power assigned to each of the storage battery units; predicting a consumption cost of each of the storage batteries and the converter according to the load rate based on the consumption life; calculating a first load rate for each of the storage battery units based on a state of the storage batteries; and adjusting the first load rate so that a total cost loss, which is the sum of the consumption costs of all of the storage batteries and the converters, is minimized.

[0009] According to one aspect of the present disclosure, a program causes a control device of a power storage system in which multiple storage battery units, each having a storage battery and a converter that converts the voltage of charging and discharging power to the storage battery, are connected in parallel via a DC bus to execute the following steps: predicting the consumption life of each of the storage batteries and the converter according to the load rate of the charging and discharging power assigned to each of the storage battery units; predicting the consumption cost of each of the storage batteries and the converter according to the load rate based on the consumption life; calculating a first load rate for each of the storage battery units based on the state of the storage batteries; and adjusting the first load rate so that the total cost loss, which is the sum of the consumption costs of all of the storage batteries and the converters, is minimized.

[0010] According to the above aspect, it is possible to extend the life of both the storage battery and the converter, thereby reducing the operating costs.

[0011] 1 is a schematic diagram showing the overall configuration of a power system according to a first embodiment. FIG. 2 is a block diagram showing the functional configuration of a control device according to the first embodiment. FIG. 3 is a first diagram for explaining the function of the control device according to the first embodiment. FIG. 4 is a second diagram for explaining the function of the control device according to the first embodiment. FIG. 5 is a third diagram for explaining the function of the control device according to the first embodiment. FIG. 6 is a block diagram showing the functional configuration of a control device according to a second embodiment. FIG. 7 is a flowchart showing an example of a method for assembling a power storage system according to a second embodiment. FIG. 8 is a diagram for explaining the method for assembling a power storage system according to a second embodiment. FIG. 9 is a diagram showing the configuration of a power storage system according to a second embodiment. FIG. 10 is a flowchart showing an example of a method for changing the configuration of a power storage system according to a second embodiment. FIG. 11 is a diagram for explaining the method for changing the configuration of a power storage system according to a second embodiment.

[0012] First Embodiment Hereinafter, a first embodiment will be described in detail with reference to FIGS.

[0013] 1 is a schematic diagram showing the overall configuration of a power system according to Embodiment 1. The power system 1 includes a DCPH system 2, a power storage system 3, a DC bus 4, and a control device 10.

[0014] The DCPH system 2 and the power storage system 3 are connected in parallel via a DC bus 4. The DCPH system 2 includes a power conditioning system (PCS) 21, a converter 22, a photovoltaic (PV) facility 23, and an electric vehicle (EV) charger 24. The PV facility 23 is a solar power generation facility. The EV charger is a charger for charging electric vehicles.

[0015] The PCS 21 is a power conditioner connected to the power grid and includes a bidirectional inverter that converts AC power to DC power. The PCS 21 converts DC power flowing through the DC bus into AC power and outputs it to the power grid. The PCS 21 also converts AC power supplied from the power grid into DC power and outputs it to the DC bus 4.

[0016] The converters 22 are DC / DC converters. As in the example of FIG. 1 , multiple converters 22 are connected in parallel via a DC bus 4. Each converter 22 is connected to a PV facility 23 or an EV charger 24. In the example of FIG. 1 , converters 22A and 22B are connected to EV chargers 24A and 24B, respectively. Converters 22C, 22D, and 22E are connected to PV facilities 23A, 23B, and 23C, respectively. The converters 22A and 22B transform the direct current flowing through the DC bus 4 to a predetermined voltage and supply it to the EV chargers 24A and 24B. The converters 22C, 22D, and 22E transform the power generated by the PV facilities 23A, 23B, and 23C to a predetermined voltage and supply it to the DC bus 4.

[0017] The power storage system 3 includes a storage battery unit 31 having a converter 32 and a storage battery 33. As in the example of FIG. 1 , the multiple storage battery units 31 are connected in parallel via a DC bus 4. The converter 32 is a DC / DC converter. The converter 32 converts the voltage of the charging / discharging power for the storage battery 33 in accordance with a command from the control device 10. The storage battery 33 is charged with power supplied from the power grid or power generated by the PV equipment 23. The discharged power of the storage battery 33 is supplied to the power grid or the EV charger 24.

[0018] The control device 10 controls the charging and discharging of each storage battery unit 31 in the power storage system 3 .

[0019] (Functional Configuration) Fig. 2 is a block diagram showing the functional configuration of the control device according to embodiment 1. As shown in Fig. 2, the control device 10 includes a processor 11, a memory 12, a storage 13, and a communication interface 14.

[0020] The processor 11 operates according to a predetermined program to perform the functions of an acquisition unit 110, a load factor calculation unit 111, a life expectancy prediction unit 112, a cost loss prediction unit 113, a load factor adjustment unit 114, and a control unit 115.

[0021] The acquisition unit 110 acquires storage battery information of the storage battery 33 of each storage battery unit 31. The storage battery information includes the SOC (State of Charge: charging rate [%]) of the storage battery 33, the voltage and current values ​​of the charging and discharging power of the storage battery 33 measured by a sensor (not shown), the temperature, and the SOH (State of Health: health level [%]). The SOH is measured periodically by a battery management system (BMS) (not shown) or the like. The storage battery information acquired by the acquisition unit 110 is recorded in the storage 13.

[0022] The load factor calculation unit 111 calculates a load factor (first load factor) of charge / discharge power allocated to each storage battery unit 31 based on the state of health (SOH) of the storage battery 33 .

[0023] The life prediction unit 112 predicts the consumed life of each of the storage battery 33 and the converter 32 according to the load factor.

[0024] The cost loss prediction unit 113 predicts the consumption costs of the storage battery 33 and the converter 32 according to the load factor based on the consumed lifespan.

[0025] The load factor adjusting unit 114 adjusts the load factor (first load factor) assigned to each storage battery unit 31 so that the total cost loss, which is the sum of the consumption costs of all storage batteries 33 and converters 32, is minimized.

[0026] The control unit 115 generates and outputs a control command for performing droop control of each storage battery unit 31. For example, the control unit 115 determines set values ​​for the slope and intercept of the droop characteristics according to the load factor of each storage battery unit 31 so as to maintain a constant voltage of the DC bus 4. The converter 32 of each storage battery unit 31 controls its own power in accordance with the droop slope and intercept included in the control command.

[0027] The memory 12 has a memory area necessary for the operation of the processor 11 .

[0028] The storage 13 is a so-called auxiliary storage device, such as a hard disk drive (HDD) or a solid state drive (SSD).

[0029] The communication interface 14 is an interface for transmitting and receiving various information (such as storage battery information) to and from external devices.

[0030] (Processing Flow) Fig. 3 is a first flowchart showing an example of processing by the control device according to the first embodiment. Here, the flow of processing in which the control device 10 adjusts the load factor of each storage battery unit 31 will be described with reference to Fig. 3. For example, it is assumed that the control device 10 (acquisition unit 110) acquires a command to discharge 100 kW from the power storage system 3 from a higher-level device that controls the power system 1. The control device 10 adjusts the load factor of each storage battery unit 31 so that the power storage system 3 as a whole can supply the requested 100 kW of discharge power.

[0031] First, the load factor calculation unit 111 calculates the load factor (first load factor) of each storage battery 33 (step S101). The load factor of storage battery 33A is the value obtained by dividing the SOH of storage battery 33A by the total SOH of storage batteries 33A to 33E. For example, if the SOH of storage batteries 33A to 33E are {A: 88%, B: 93%, C: 91%, D: 90%, E: 92%}, respectively, the load factor of storage battery 33A is 88 / (88 + 93 + 91 + 90 + 92) = 19.38%. The load factor calculation unit 111 similarly calculates the load factors of the other storage batteries 33B to 33E.

[0032] The control unit 115 performs droop control based on the load factor (first load factor) of each storage battery unit 31. Then, the control unit 115 acquires operating conditions (voltage, current) from the sensors of each storage battery unit 31 (step S102).

[0033] Next, the life prediction unit 112 predicts the consumed life of each storage battery 33 (step S103). For example, it is determined whether each storage battery 33 has reached its set life based on its SOH. For example, if the SOH falls below a predetermined SOH lower limit (e.g., 30%), it is determined that the set life has been reached and replacement is necessary. Therefore, the consumed life is the amount of SOH decline. The amount of SOH decline is calculated using a table or function of an SOH reduction curve under load obtained from, for example, past test data or operating data (voltage, current, and temperature of the storage battery 33). This table or function specifies the amount of SOH decline when operating for a certain period of time under various operating conditions. Because differences in temperature and other factors during operation occur depending on the individual storage battery 33 and its placement, the SOH reduction curve may differ for each storage battery 33 as operating data for each storage battery 33 is accumulated. Therefore, a different table or function is prepared for each storage battery 33. The life prediction unit 112 calculates the extent of SOH decrease of each storage battery 33 based on this table or function, the operating conditions (voltage, current) acquired in step S102, and the expected operating time.

[0034] The cost loss prediction unit 113 also predicts the consumption cost of each storage battery 33 (step S104). The consumption cost is the replacement cost of the storage battery 33 converted into a value (amount) corresponding to the consumed lifespan. The replacement cost is the sum of the cost of the storage battery 33 itself (purchase cost), the cost required for the replacement work (labor cost), and the opportunity loss cost during the replacement work. The opportunity loss cost includes revenue (such as service fees) that would have been earned during the service outage of the power storage system 3 due to replacement, and the cost of using another power storage system. The cost loss prediction unit 113 predicts the consumption cost of the storage battery 33 by assuming that the replacement cost when the lifespan of the storage battery 33 reaches the set lifespan (SOH lower limit) is a cost corresponding to the ratio of the consumed lifespan to the total lifespan of the storage battery 33. For example, if the SOH lower limit of storage battery 33A is 30%, the consumed lifespan is 1%, and the replacement cost is 1.75 million yen, the replacement cost is assumed to be 1% of the lifespan (100 - 30 = 70%). That is, the consumption cost C of the storage battery 33A is 175×1 / 70=25,000 yen. The cost loss prediction unit 113 predicts the consumption costs of the other storage batteries 33B to 33E in the same manner.

[0035] Furthermore, the life prediction unit 112 predicts the consumed life of each converter 32 (step S105). Note that steps S103 to S104 and steps S105 to S106 may be performed in order, or may be performed in parallel as in the example of FIG.

[0036] FIG. 4 is a second flowchart showing an example of processing by the control device according to the first embodiment. For example, the power semiconductor is an important factor in determining the lifespan of the converter 32. The power semiconductor deteriorates due to cracks caused by thermal expansion and contraction. Therefore, the lifespan prediction unit 112 calculates the consumed lifespan of the converter 32 using the degree of deterioration of the power semiconductor as an index. Specifically, the lifespan prediction unit 112 first calculates the junction temperature Tj of the power semiconductor from the operating conditions (voltage, current) acquired in step S102 (step S105A). Specifically, the lifespan prediction unit 112 calculates the junction temperature Tj from the temperature Tth, loss Loss, and thermal resistance Rth of the built-in thermistor using the following equation:

[0037] Tj=Loss×Rth+Tth

[0038] The temperature Tth of the built-in thermistor is a measured value by a sensor (not shown). The loss is an estimated value estimated based on the relational expression between the current and the loss. The thermal resistance Rth is a constant determined by the configuration of the power semiconductor. In order to take into account the individual differences (differences due to variations) of the power semiconductor, a weighting coefficient for deterioration is created from the static characteristics (Ic-Vce characteristics, Id-Vds characteristics) of the power semiconductor in the shipping test (pre-shipment inspection) and reflected in the relational expression for the loss. This makes it possible to predict the lifespan of each converter 32 taking into account the difference in deterioration between each converter 32.

[0039] Furthermore, the life prediction unit 112 calculates the consumed life Lc of each converter 32 (step S105B).

[0040] FIG. 5 is a first diagram illustrating the function of the control device according to the first embodiment. The life prediction unit 112 stores information in the form of a table showing the consumed life for each cycle (each ΔT1) of change in junction temperature Tj using the rainflow method. Furthermore, the life prediction unit 112 estimates the operating pattern (the number of cycles of temperature change) of each converter 32 during the expected operating time based on past operating data, the operating conditions acquired in step S102, and the like. Note that during periods when no operating data is accumulated, the life prediction unit 112 may estimate the operating pattern based on predetermined hypothetical data. For example, assume that the operating pattern shown in FIG. 5 is estimated. The life prediction unit 112 calculates the consumed life from the estimated operating pattern, ΔT during the expected operating time, and the number of cycles. For example, in the example of FIG. 5, ΔT1 = 40 degrees and ΔT2 = 30 degrees. Furthermore, according to the consumed life table, the life will expire if a 40-degree temperature change is repeated X1 times, which is the upper limit number of cycles. (The life will be 100% consumed.) Furthermore, it is assumed that the life span will be reached when a temperature change of 30 degrees is repeated X2 times, which is the upper limit number of cycles. In this case, the consumed life span for one cycle of ΔT1 is 1 / X1, and the consumed life span for one cycle of ΔT2 is 1 / X2. In other words, the consumed life span for each ΔT is calculated as the reciprocal of the upper limit number of cycles for each temperature. The life span prediction unit 112 adds up the consumed life spans for each ΔT and calculates the consumed life span of each converter 32 for this entire operating pattern.

[0041] Next, the cost loss prediction unit 113 predicts the consumption cost of each converter 32 (step S106). The method for calculating the consumption cost is the same as in step S104. The cost loss prediction unit 113 predicts the consumption cost of each converter 32, assuming that the replacement cost when the converter 32 reaches its set lifespan (lower degradation limit) is a cost corresponding to the ratio of the consumed lifespan to the total lifespan of the converter 32. For example, if the lower degradation limit of converter 32A is 30%, the consumed lifespan is 8%, and the replacement cost is 1.4 million yen, then the replacement cost corresponds to 8% of the lifespan (100-30=70%). In other words, the consumption cost C of converter 32A is 140 x 8 / 70 = 160,000 yen. The cost loss prediction unit 113 similarly predicts the consumption costs of the other converters 32B to 32E.

[0042] Once the prediction of the consumption costs of each storage battery 33 and each converter 32 is completed, the cost loss prediction unit 113 adds up the total consumption costs of each storage battery unit 31 (consumption cost of storage battery 33 + consumption cost of converter 32) and predicts the first total cost loss Ct for the first load rate (step S107).

[0043] FIG. 6 is a second diagram illustrating the function of the control device according to the first embodiment. As shown in FIG. 6 , assume that the total loss cost Ct is 425,000 yen for the load factor (first load factor) calculated in step S101. Next, the load factor adjustment unit 114 searches for a load factor that results in the initial total loss cost while changing this load factor. Specifically, the load factor adjustment unit 114 first changes the load factor of each storage battery unit 31 and predicts a second total loss cost Ct+1 corresponding to the changed load factor (second load factor) (step S108).

[0044] The load factor adjustment unit 114 sets a second load factor by reducing the load factor of the storage battery unit 31 with the highest consumption cost among the total consumption costs of each storage battery unit 31 predicted using the first load factor and increasing the load factors of the other storage battery units 31. In the example of FIG. 6 , the total consumption cost of the storage battery unit 31A is the highest. Therefore, the load factor adjustment unit 114 sets a second load factor by reducing the load factor of the storage battery unit 31A by a predetermined amount and allocating and adding a predetermined amount to the load factors of the other storage battery units 31B to 31E. The predetermined amount is, for example, 0.1% × (total number of units − 1). In the example of FIG. 6 , the load factor of the storage battery unit 31A is changed to 35% − 0.4% = 34.6%. Furthermore, the load factors of the storage battery units 31B to 31E are increased by 0.1% to 25.1%, 20.1%, 15.1%, and 5.1%, respectively.

[0045] Furthermore, the control unit 115, the life expectancy prediction unit 112, and the cost loss prediction unit 113 perform the processes of steps S102 to S107 again to predict a second total cost loss Ct+1 for the second load factor.

[0046] Next, the load factor adjustment unit 114 determines whether the second total cost loss Ct+1 for the second load factor is smaller than the first total cost loss Ct for the first load factor (step S109). If the second total cost loss Ct+1 is smaller than the first total cost loss Ct (step S109; YES), the load factor adjustment unit 114 updates the first load factor with the second load factor and updates the first total cost loss Ct with the second total cost loss Ct+1 (step S110). Thereafter, the load factor adjustment unit 114 returns to step S108.

[0047] On the other hand, if the first total loss cost Ct is smaller (step S109; NO), this first total loss cost Ct becomes the minimum loss cost. Therefore, the load factor adjustment unit 114 determines the condition (first load factor) of this first total loss cost Ct. Then, the control unit 115 sets a control command (droop control command) for each storage battery unit 31 based on the determined first load factor. In this way, the load factor adjustment unit 114 repeatedly rewrites the first load factor with the value of the second load factor and calculates the second total loss cost Ct+1 at the new second load factor (step S108) until the first total loss cost Ct at the first load factor becomes the minimum.

[0048] FIG. 7 is a third diagram illustrating the function of the control device according to the first embodiment. FIG. 7 shows an example of a combination of load factors that minimizes the total cost loss. At the load factor shown in FIG. 6, the total cost loss was 425,000 yen. However, by adjusting the load factor as shown in FIG. 7, the total cost loss could be reduced to 423,000 yen. In other words, compared to the initial load factor (FIG. 6), the life of the converter 32A of the storage battery unit 31A could be extended, and the operating costs of the power storage system 3 could be reduced.

[0049] (Actions and Effects) As described above, the control device 10 of the energy storage system 3 according to this embodiment includes a lifespan prediction unit 112 that predicts the consumption lifespan of each of the storage batteries 33 and the converters 32 according to the load rate of the charging and discharging power allocated to each of the storage battery units 31, a cost loss prediction unit 113 that predicts the consumption cost of each of the storage batteries 33 and the converters 32 according to the load rate based on the consumption lifespan, a load rate calculation unit 111 that calculates a first load rate for each of the storage battery units 31 based on the state of the storage batteries 33, and a load rate adjustment unit 114 that adjusts the first load rate so that the total cost loss Ct, which is the sum of the consumption costs of all of the storage batteries 33 and the converters 32, is minimized.

[0050] For example, if five storage battery units are required to output a total of 100 kW, ideally, each storage battery unit should output 20 kW. However, in reality, due to individual differences in converters and storage batteries, or factors such as placement of some storage battery units in a thermally severe environment, the degradation rates of each storage battery unit may differ even if the same current is applied to each storage battery unit. For this reason, in conventional technology, in order to extend the expected life of the storage batteries, the load factor is calculated to ensure a substantially uniform SOH for each storage battery and input it to each converter. However, in conventional technology, the long life of converters, which are less expensive than storage batteries, is not sufficiently considered. In contrast, the control device 10 according to the present embodiment minimizes the total cost loss Ct, which is the sum of the consumption costs of the storage battery 33 and the converter 32, as described above. This reduces the consumed life of both the storage battery 33 and the converter 32, thereby extending their lifespan and reducing the operating costs of the entire energy storage system 3.

[0051] In addition, the load rate adjustment unit 114 reduces, by a predetermined amount, the first load rate of the storage battery unit 31 having the highest total value of the consumption costs of the storage batteries 33 and the converter 32, distributes and adds the predetermined amount to the first load rates of the other storage battery units 31, and sets a second load rate, which is the adjusted load rate; if the second total cost loss Ct+1 of the second load rate is smaller than the first total cost loss Ct of the first load rate, the load rate adjustment unit 114 rewrites the first load rate with the value of the second load rate until the first total cost loss Ct of the first load rate becomes the smallest, and repeats the process of predicting the consumption cost using the new second load rate.

[0052] In this way, it is possible to more reliably extend the life of the storage battery 33 and the converter 32 and reduce the operating costs of the entire power storage system 3 .

[0053] The cost loss prediction unit 113 predicts the consumption costs of the storage battery 33 and the converter 32, assuming that the replacement costs when the lifespans of the storage battery 33 and the converter 32 reach their set lifespans are incurred at a rate proportional to the ratio of the consumed lifespan to the total lifespan of the storage battery 33 and the converter 32.

[0054] In this way, the control device 10 can accurately predict the consumption costs of the storage battery 33 and the converter 32.

[0055] Second Embodiment Next, a second embodiment will be described with reference to Figures 8 to 13. Components common to the above-described embodiment will be assigned the same reference numerals, and detailed description thereof will be omitted.

[0056] The storage batteries 33 and the converters 32 each have different resistance to deterioration. In this embodiment, the combination of the storage batteries 33 and the converters 32 is changed based on the resistance of each of the storage batteries 33 and the converters 32 to deterioration, thereby extending the life of the storage battery unit 31 and reducing the operating costs.

[0057] 8 is a block diagram showing the functional configuration of the control device according to the second embodiment. As shown in FIG. 8, the control device 10 according to this embodiment further includes an intensity estimation unit 116.

[0058] The strength estimation unit 116 estimates the strength of the storage battery 33 and the converter 32 against deterioration from the life loss and average load factor of each of the storage battery 33 and the converter 32.

[0059] The control device 10 may further include a display device 15. The intensities of the storage batteries 33 and the converters 32 estimated by the intensity estimation unit 116 are displayed on the display device 15 and can be viewed by a worker performing maintenance on the power storage system 3. The intensities estimated by the intensity estimation unit 116 may also be transmitted to another device, such as a server or terminal device, used by the worker.

[0060] Fig. 9 is a flowchart showing an example of a method for assembling the power storage system according to the second embodiment. Here, an example of a method for assembling the power storage system 3 before it starts to be operated (at the time of new installation) will be described with reference to Fig. 9 .

[0061] First, the strength estimation unit 116 associates the static characteristics (Ic-Vce characteristics, Id-Vds characteristics) of the power semiconductors of each converter 32 obtained during shipping testing (pre-shipment inspection) with the serial numbers of the converters 32 (step S201). The static characteristics of the power semiconductors are obtained from data sheets provided by the power semiconductor manufacturers. At this time, the strength estimation unit 116 may estimate the strength against degradation from the static characteristics of the power semiconductors and associate the strength against degradation with the serial numbers of each converter 32. The strength against degradation may be expressed in three levels, such as strong, medium, and weak. The strength estimation unit 116 estimates that the higher the resistance value of the power semiconductor, the weaker the strength against degradation.

[0062] The strength estimation unit 116 also associates the cell battery capacity data of each storage battery 33 obtained in the shipping test with the serial number of the storage battery 33 (step S202). At this time, the strength estimation unit 116 may estimate that the larger the cell battery capacity, the stronger the resistance to deterioration, and associate the estimation result with the serial number of each converter 32.

[0063] The information linked by the strength estimation unit 116 is attached to the housings of the storage battery 33 and the converter 32 using a two-dimensional code such as a QR code (registered trademark). The installer (assembly worker) of the power storage system 3 reads the QR code to determine the relative strengths of the storage battery 33 and the converter 32 with respect to deterioration (step S203).

[0064] In addition, the installer arranges the storage batteries 33 and converters 32 in order based on the relative merits of the storage batteries 33 and converters 32, so that the storage batteries 33 and converters 32 are combined together in a combination of stronger and weaker strength.

[0065] FIG. 10 is a diagram illustrating a method for assembling a power storage system according to the second embodiment. For example, as shown in FIG. 10A, the intensities of the storage batteries 33A, 33B, and 33C are medium, strong, and weak, respectively, and the intensities of the converters 32A, 32B, and 32C are medium, weak, and strong, respectively. Here, as in the example of FIG. 10A, if the storage battery 33 and the converter 32 are combined without considering their intensities, for example, a weak converter 32B may be combined with a strong storage battery 33B. In this case, if the lifespan and consumption cost of the converter 32B are predicted based on the static characteristics of the converter 32B, as in the first embodiment, the consumption cost is likely to be relatively high due to the converter 32B's low resistance to degradation, which may result in a low load factor for the converter 32B. As a result, the storage battery 33B combined with the converter 32B will not be able to fully utilize its resistance to degradation. Furthermore, an imbalance in resistance to degradation also occurs in the combination of the converter 32C and the storage battery 33C. In such an unbalanced storage battery unit 31, the strength may not be fully utilized, or a load may be applied even though the strength is insufficient.

[0066] 10(b), by combining a high-power storage battery 33B with a similarly high-power converter 32C, the imbalance is eliminated, and the strengths of the storage battery 33B and the converter 32C against deterioration can be fully utilized. Also, in the case of a weak combination of the storage battery 33C and the converter 32B, the possibility of excessive load being applied can be reduced.

[0067] Fig. 11 is a diagram showing the configuration of the power storage system according to the second embodiment. As shown in Fig. 11, the converter 32 may be attached by inserting the male connector 36 into the female connector 35 of the circuit board 34. In the examples of Fig. 10(b) and Fig. 11, by swapping the converter 32B and the converter 32C, it is possible to easily configure the storage battery units 31 in an appropriate combination.

[0068] Fig. 12 is a flowchart showing an example of a method for changing the configuration of the power storage system according to the second embodiment. As shown in Fig. 12, the combination of the storage batteries 33 and the converters 32 may be changed by evaluating the degree of deterioration of the storage batteries 33 and the converters 32 during operation of the power storage system 3. For example, the control device 10 executes the series of processes shown in Fig. 12 when the SOH of each storage battery 33 is measured.

[0069] First, the intensity estimation unit 116 reads the loss of life (SOH) of each storage battery 33 (step S211).

[0070] The intensity estimator 116 also acquires the past average load factor of each storage battery 33 (step S212). The storage 13 stores a history of the load factors determined by the load factor adjuster 114, and the intensity estimator 116 calculates the average value of the load factor from the start of operation of the power storage system 3 to the present from this history.

[0071] The intensity estimator 116 calculates the life loss of the converter 32 (step S213). For example, the storage 13 records a history of the current value applied to each converter 32, and the intensity estimator 116 calculates the life deterioration of each converter 32 based on this history so that the greater the current value, the greater the degree of deterioration.

[0072] The intensity estimator 116 also acquires the past average load factor of each converter 32 (step S214).

[0073] Next, the intensity estimation unit 116 calculates a coefficient α by dividing the life loss of each storage battery 33 and each converter 32 by the average load factor (step S215).

[0074] Furthermore, the intensity estimation unit 116 determines a combination of the storage battery 33 and the converter 32 based on the coefficient α (step S216). For example, the intensity estimation unit 116 determines that the smaller the coefficient α, the stronger the resistance to deterioration, and determines a combination of the storage battery 33 and the converter 32 such that two storage batteries with high strength and two storage batteries with low strength are combined. The determined combination is displayed on the display device 15 and presented to the worker. Note that in another embodiment, the intensity estimation unit 116 may display the coefficient α of the storage battery 33 and the converter 32 on the display device 15, and the worker may determine a combination based on the coefficient α.

[0075] Next, the operator replaces the converters 32 so as to obtain the combination obtained from the calculation result of the intensity estimation unit 116 (step S217).

[0076] FIG. 13 is a diagram illustrating a method for changing the configuration of the power storage system according to the second embodiment. For example, as shown in FIG. 13A, due to factors such as the placement of the storage battery 33, the storage battery 33B deteriorates, weakening its resistance to deterioration (increasing the coefficient α). This may result in an imbalance in the resistance to deterioration between the storage battery 33B and the converter 32C, making it difficult to optimize the load factor. Therefore, as shown in FIG. 13BB, the intensity estimation unit 116 determines a combination of the storage battery 33B and the converter 32C based on the strengths (coefficient α), and a combination of the storage battery 33C and the converter 32B, and presents this combination to the operator. The operator then swaps the converter 32B and the converter 32C according to the presented combination.

[0077] In this way, the control device 10 can present to the worker a combination that can eliminate the imbalance in strength against deterioration between the storage battery 33 and the converter 32. This makes it possible to optimize the combination of the storage battery 33 and the converter 32 and operate the power storage system 3 more efficiently.

[0078] Other Embodiments Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design modifications are possible. That is, in other embodiments, the order of the above-described processes may be changed as appropriate. Furthermore, some processes may be executed in parallel.

[0079] <Additional Notes> The power storage system control device, the power storage system, the power storage system control method, and the program described in the above-described embodiments can be understood, for example, as follows.

[0080] (1) According to a first aspect, the control device 10 of the energy storage system 3 is a control device 10 of the energy storage system 3 in which a plurality of storage battery units 31, each having a storage battery 33 and a converter 32 for charging and discharging power for the storage battery 33, are connected in parallel via a DC bus 4, and includes: a lifespan prediction unit 112 that predicts the consumption lifespan of each of the storage batteries 33 and the converter 32 according to the load rate of charging and discharging power assigned to each of the storage battery units 31; a cost loss prediction unit 113 that predicts the consumption cost of each of the storage batteries 33 and the converter 32 according to the load rate based on the consumption lifespan; a load rate calculation unit 111 that calculates a first load rate for each of the storage battery units 31 based on the state of the storage battery 33; and a load rate adjustment unit 114 that adjusts the first load rate so that the total cost loss, which is the sum of the consumption costs of all of the storage batteries 33 and the converters 32, is minimized.

[0081] For example, if five storage battery units are required to output a total of 100 kW, ideally, each storage battery unit should output 20 kW. However, in reality, due to individual differences in converters and storage batteries, or factors such as placement of some storage battery units in a thermally severe environment, the degradation rates of each storage battery unit may differ even if the same current is applied to each storage battery unit. For this reason, in conventional technology, in order to extend the expected life of the storage batteries, the load factor is calculated to ensure a substantially uniform SOH for each storage battery and input it to each converter. However, in conventional technology, the long life of converters, which are less expensive than storage batteries, is not sufficiently considered. In contrast, the control device 10 according to the present embodiment minimizes the total cost loss Ct, which is the sum of the consumption costs of the storage battery 33 and the converter 32, as described above. This reduces the consumed life of both the storage battery 33 and the converter 32, thereby extending their lifespan and reducing the operating costs of the entire energy storage system 3.

[0082] (2) According to the second aspect, in the control device 10 of the energy storage system 3 according to the first aspect, the load factor adjustment unit 114 reduces, by a predetermined amount, the first load factor of the storage battery unit 31 having the highest total value of the consumption costs of the storage batteries 33 and the converter 32, distributes and adds the predetermined amount to the first load factors of the other storage battery units 31, and sets a second load factor, which is the adjusted load factor. If the second total cost loss of the second load factor is smaller than the first total cost loss of the first load factor, the first load factor is rewritten with the value of the second load factor until the first total cost loss of the first load factor is minimized, and the process of predicting the consumption cost using the new second load factor is repeated.

[0083] In this way, it is possible to more reliably extend the life of the storage battery 33 and the converter 32 and reduce the operating costs of the entire power storage system 3 .

[0084] (3) According to the third aspect, in the control device 10 of the energy storage system 3 relating to the first or second aspect, the cost loss prediction unit 113 predicts the consumption costs of the storage battery 33 and the converter 32, assuming that the replacement costs when the lifespans of the storage battery 33 and the converter 32 reach their set lifespans are calculated based on the ratio of the consumed lifespan to the total lifespan of the storage battery 33 and the converter 32.

[0085] In this way, the control device 10 can accurately predict the consumption costs of the storage battery 33 and the converter 32.

[0086] (4) According to a fourth aspect, the control device 10 of the energy storage system 3 relating to any one of the first to third aspects further includes an intensity estimation unit 116 that estimates the intensity of deterioration of each of the storage battery 33 and the converter 32 from the life loss and average load factor of each of the storage battery 33 and the converter 32.

[0087] In this way, the control device 10 can present to the worker a combination that can eliminate the imbalance in strength against deterioration between the storage battery 33 and the converter 32. This makes it possible to optimize the combination of the storage battery 33 and the converter 32 and operate the power storage system 3 more efficiently.

[0088] (5) According to a fifth aspect, the energy storage system 3 includes a plurality of storage battery units 31 each having a storage battery 33 and a converter 32 for charging and discharging power for the storage battery 33, and a control device 10 according to any one of the first to fourth aspects.

[0089] By minimizing the total cost loss Ct, which is the sum of the consumption costs of the storage battery 33 and the converter 32, the storage system 3 can reduce and extend the consumption lifespan of both the storage battery 33 and the converter 32, and can also reduce the operating costs of the entire storage system 3.

[0090] (6) According to a sixth aspect, in the energy storage system 3 relating to the fifth aspect, the control device 10 further includes an intensity estimation unit 116 that estimates the strength of the storage battery 33 and the converter 32 against deterioration based on the life loss and average load factor of each of the storage battery 33 and the converter 32, and the converter 32 can be changed in combination with the storage battery 33 based on the strength.

[0091] In this way, the power storage system 3 can present to the worker a combination that can eliminate the imbalance in strength against deterioration between the storage battery 33 and the converter 32. This makes it possible to optimize the combination of the storage battery 33 and the converter 32 and operate the power storage system 3 more efficiently.

[0092] (7) According to a seventh aspect, a control method for a power storage system 3 is a control method for a power storage system 3 in which a plurality of storage battery units 31, each having a storage battery 33 and a converter 32 for charging and discharging power for the storage battery 33, are connected in parallel via a DC bus 4, and includes the steps of: predicting a consumption life of each of the storage batteries 33 and the converter 32 according to a load rate of charging and discharging power allocated to each of the storage battery units 31; predicting a consumption cost of each of the storage batteries 33 and the converter 32 according to the load rate based on the consumption life; calculating a first load rate for each of the storage battery units 31 based on the state of the storage battery 33; and adjusting the first load rate so that a total cost loss obtained by adding up the consumption costs of all the storage batteries 33 and the converters 32 is minimized.

[0093] (8) According to the eighth aspect, the program causes the control device 10 of the power storage system 3, in which a plurality of storage battery units 31, each having a storage battery 33 and a converter 32 for charging and discharging power for the storage battery 33, are connected in parallel via a DC bus 4, to execute the following steps: predicting the consumption life of each of the storage batteries 33 and the converter 32 according to the load rate of charging and discharging power assigned to each of the storage battery units 31; predicting the consumption cost of each of the storage batteries 33 and the converter 32 according to the load rate based on the consumption life; calculating a first load rate for each of the storage battery units 31 based on the state of the storage battery 33; and adjusting the first load rate so that the total cost loss, which is the sum of the consumption costs of all the storage batteries 33 and the converters 32, is minimized.

[0094] According to the above aspect, it is possible to extend the life of both the storage battery and the converter, thereby reducing the operating costs.

[0095] REFERENCE SIGNS LIST 1 Power system 2 DCPH system 3 Power storage system 4 DC bus 10 Control device 11 Processor 110 Acquisition unit 111 Load factor calculation unit 112 Lifetime prediction unit 113 Cost loss prediction unit 114 Load factor adjustment unit 115 Control unit 116 Strength estimation unit 12 Memory 13 Storage 14 Communication interface 15 Display device 21 PCS 22 Converter 23 PV equipment 24 EV charger 31 Storage battery unit 31 Storage battery unit 32 Converter 33 Storage battery 34 Board 35 Female side connector 36 Male side connector

Claims

1. A control device for a power storage system in which a plurality of storage battery units, each having a storage battery and a converter for charging and discharging power for the storage battery, are connected in parallel via a DC bus, comprising: a life prediction unit that predicts the consumption life of each of the storage batteries and the converter according to the load rate of the charging and discharging power assigned to each of the storage battery units; a cost loss prediction unit that predicts the consumption cost of each of the storage batteries and the converter according to the load rate based on the consumption life; a load rate calculation unit that calculates a first load rate for each of the storage battery units based on the state of the storage batteries; and a load rate adjustment unit that adjusts the first load rate so that a total cost loss obtained by adding up the consumption costs of all of the storage batteries and the converters is minimized.

2. The control device for a power storage system as described in claim 1, wherein the load factor adjustment unit reduces, by a predetermined amount, a first load factor of a storage battery unit having the highest total value of the consumption costs of the storage battery and the converter, distributes and adds the predetermined amount to the first load factors of the other storage battery units, and sets a second load factor which is the adjusted load factor; and when a second total cost loss of the second load factor is smaller than a first total cost loss of the first load factor, rewrites the first load factor with the value of the second load factor until the first total cost loss of the first load factor is minimized, and repeats the process of predicting the consumption cost using the new second load factor.

3. The control device for a power storage system as described in claim 1, wherein the cost loss prediction unit predicts the consumption costs of the storage battery and the converter when their lifespans reach a set lifespan, assuming that the cost of replacement when the lifespans of the storage battery and the converter reach a ratio of the consumed lifespan to the total lifespan of the storage battery and the converter has been consumed.

4. The control device for a power storage system according to any one of claims 1 to 3, further comprising a strength estimation unit that estimates the strength against deterioration of each of the storage battery and the converter from the life loss and average load factor of each of the storage battery and the converter.

5. A power storage system comprising: a plurality of storage battery units each having a storage battery and a converter for charging and discharging power for the storage battery; and the control device according to any one of claims 1 to 3.

6. The power storage system according to claim 5, wherein the control device further comprises a strength estimation unit that estimates the strength against deterioration of the storage battery and the converter from the life loss and average load factor of each of the storage battery and the converter, and the converter is capable of changing its combination with the storage battery based on the strength.

7. A control method for a power storage system in which a plurality of storage battery units, each having a storage battery and a converter for charging and discharging power for the storage batteries, are connected in parallel via a DC bus, the control method comprising the steps of: predicting a consumption life of each of the storage batteries and the converter according to a load rate of the charging and discharging power assigned to each of the storage battery units; predicting a consumption cost of each of the storage batteries and the converter according to the load rate based on the consumption life; calculating a first load rate for each of the storage battery units based on a state of the storage batteries; and adjusting the first load rate so that a total cost loss calculated by adding up the consumption costs of all of the storage batteries and the converters is minimized.

8. A program that causes a control device of a power storage system in which multiple storage battery units, each having a storage battery and a converter for charging and discharging power for the storage batteries, are connected in parallel via a DC bus, to execute the following steps: predicting a consumption life of each of the storage batteries and the converter according to a load rate of the charging and discharging power assigned to each of the storage battery units; predicting a consumption cost of each of the storage batteries and the converter according to the load rate based on the consumption life; calculating a first load rate for each of the storage battery units based on the state of the storage batteries; and adjusting the first load rate so that a total cost loss obtained by adding up the consumption costs of all of the storage batteries and the converters is minimized.

Images