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

Abstract

To provide a control device for a power storage system that can extend the life of both a storage battery and a converter and reduce operation costs.SOLUTION: A control device of a power storage system includes a life prediction unit that predicts the consumption life of each of a power storage battery and a converter according to the load rate of charging and discharging power allocated to each of a storage battery unit, a cost loss prediction unit that predicts the consumption cost of each of the storage batteries and the converter according to the load rate on the basis of the consumption life, a load rate calculation unit that calculates a first load rate for each of the storage battery units on the basis of the state of the storage batteries, and a load rate adjustment unit that adjusts the first load rate such that the total cost loss, which is the sum of the consumption costs of all of the storage batteries and the converters, is minimized.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a control device for an energy storage system, an energy storage system, a control method for an energy storage system, and a program.

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an energy storage system (ESS: Energy Storage System) in which a plurality of battery units having a battery and a converter are arranged in parallel, control is generally performed to extend the life of the battery, which is more expensive than the converter. In that case, since it is difficult to consider the life of the relatively inexpensive converter, the converter may deteriorate.

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

Means for Solving the Problems

[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 that connects a plurality of power storage units having a storage battery and a converter for converting charge and discharge power to the storage battery in parallel via a DC bus, and includes a life prediction unit that predicts the consumption life of each of the storage battery and the converter according to the load factor of the charge and discharge power assigned to each of the power storage units, a cost loss prediction unit that predicts the consumption cost of each of the storage battery and the converter according to the load factor based on the consumption life, a load factor calculation unit that calculates a first load factor for each of the power storage units based on the state of the storage battery, and a load factor adjustment unit that adjusts the first load factor so that the total cost loss obtained by summing the consumption costs of all 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 power storage units having a storage battery and a converter that converts the voltage of charge and discharge power to 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 that connects a plurality of power storage units having a storage battery and a converter that converts the voltage of charge and discharge power to the storage battery in parallel via a DC bus, and includes a step of predicting the consumption life of each of the storage battery and the converter according to the load factor of the charge and discharge power assigned to each of the power storage units, a step of predicting the consumption cost of each of the storage battery and the converter according to the load factor based on the consumption life, a step of calculating a first load factor for each of the power storage units based on the state of the storage battery, and a step of adjusting the first load factor so that the total cost loss obtained by summing the consumption costs of all the storage batteries and the converters is minimized.

[0009] According to one aspect of the present disclosure, the program causes a control device of a power storage system that connects a plurality of power storage units each having a storage battery and a converter that converts the voltage of the charge / discharge power to the storage battery in parallel via a DC bus to predict the consumption life of each of the storage battery and the converter according to the load factor of the charge / discharge power assigned to each of the power storage units, predict the consumption cost of each of the storage battery and the converter according to the load factor based on the consumption life, calculate a first load factor for each of the power storage units based on the state of the storage battery, and adjust the first load factor so that the total cost loss obtained by summing up the consumption costs of all the storage batteries and the converters is minimized.

Advantages of the Invention

[0010] According to the above aspect, it is possible to extend the service life of both the storage battery and the converter and reduce the operation cost.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0012] <First Embodiment> Hereinafter, the first embodiment will be described in detail with reference to FIGS. 1 to 7.

[0013] (Overall Configuration) FIG. 1 is a schematic diagram showing the overall configuration of a power system according to the first embodiment. 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 the DC bus 4. The DCPH system 2 includes a PCS (Power Conditioning System) 21, a converter 22, PV (Photovoltaic) equipment 23, and an EV (Electric Vehicle) charger 24. The PV equipment 23 is a solar power generation facility. The EV charger is a charger for charging an electric vehicle.

[0015] The PCS 21 is a power conditioner that is interconnected with the power grid and has a bidirectional inverter for converting AC power and DC power. The PCS 21 converts the DC power flowing through the DC bus into AC power and outputs it to the power grid. Also, the PCS 21 converts the AC power supplied from the power grid into DC power and outputs it to the DC bus 4.

[0016] The converter 22 is a DC / DC converter. As in the example of FIG. 1, a plurality of converters 22 are connected in parallel via the DC bus 4. Each converter 22 is connected to the PV facility 23 or the EV charger 24. In the example of FIG. 1, the converters 22A and 22B are connected to the EV chargers 24A and 24B, respectively. The converters 22C, 22D, and 22E are connected to the 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 power storage unit 31 having a converter 32 and a storage battery 33. As in the example of FIG. 1, a plurality of power storage units 31 are connected in parallel via the DC bus 4. The converter 32 is a DC / DC converter. The converter 32 converts the voltage of the charge and discharge power with respect to the storage battery 33 according to the command of the control device 10. The storage battery 33 is charged by the power supplied from the power grid or the power generated by the PV facility 23. Also, the discharge power of the storage battery 33 is supplied to the power grid or the EV charger 24.

[0018] The control device 10 controls the charge and discharge of each power storage unit 31 of the power storage system 3.

[0019] (Functional configuration) FIG. 2 is a block diagram showing the functional configuration of the control device according to the first embodiment. 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] By operating according to a predetermined program, the processor 11 exhibits functions as an acquisition unit 110, a load factor calculation unit 111, a life 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 the battery information of the battery 33 of each battery unit 31. The battery information includes the SOC (State of Charge [%]) of the battery 33, the voltage value and current value of the charge and discharge power of the battery 33 measured by a sensor (not shown), the temperature, and the SOH (State of Health [%]). The SOH is periodically measured by a BMS (Battery Management System) or the like (not shown). The battery information acquired by the acquisition unit 110 is recorded in the storage 13.

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

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

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

[0025] The load factor adjustment unit 114 adjusts the load factor (first load factor) assigned to each battery unit 31 so that the total cost loss obtained by summing up the consumption costs of all the batteries 33 and converters 32 is minimized.

[0026] The control unit 115 generates and outputs a control command for performing droop control on each battery unit 31. For example, the control unit 115 determines the set values of the slope and intercept of the droop characteristics according to the load factor of each battery unit 31 so that the voltage of the DC bus 4 is kept constant. The converter 32 of each battery unit 31 controls its own power according to 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] Storage 13 is a so-called auxiliary storage device, such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), etc.

[0029] The communication interface 14 is an interface for transmitting and receiving various types of information (such as battery information, etc.) to and from an external device.

[0030] (Processing Flow) FIG. 3 is a first flowchart showing an example of the processing of the control device according to the first embodiment. Here, while referring to FIG. 3, the flow of the process in which the control device 10 adjusts the load factor of each battery unit 31 will be described. The control device 10 (acquisition unit 110) has, for example, acquired 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 battery unit 31 so as to be able to supply the required 100 kW of discharge power for the entire power storage system 3.

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

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

[0033] Next, the remaining life prediction unit 112 predicts the remaining life of each storage battery 33 (step S103). For example, it is determined whether each storage battery 33 has reached the set life based on the SOH. For example, when the SOH becomes equal to or lower than a preset SOH lower limit value (for example, 30%), it is determined that the set life has been reached and replacement is necessary. Therefore, the remaining life is the decrease width of the SOH. The decrease width of the SOH is calculated using, for example, a table or a function obtained by tabulating or functionalizing the SOH reduction curve at the time of load approval obtained from past test data or operation data (voltage, current, temperature of the storage battery 33). This table or function defines the decrease width of the SOH when operating for a certain period of time under each operating condition. Since differences occur in the temperature during operation depending on the individual differences and arrangement of the storage batteries 33, the SOH reduction curve may be different for each storage battery 33 as the operation data of each storage battery 33 is accumulated. Therefore, different tables or functions are prepared for each storage battery 33. The remaining life prediction unit 112 calculates the decrease width of the SOH of each storage battery 33 based on this table or function, the operating conditions (voltage, current) acquired in step S102, and the assumed operating time.

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

[0035] Also, the life prediction unit 112 predicts the consumption 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. 3.

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

[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 Loss is an estimated value estimated based on the relational expression between the current and the loss Loss. The thermal resistance Rth is a constant determined by the configuration of the power semiconductor. In addition, in order to consider the individual differences (differences due to variations) of the power semiconductors, a deterioration weighting factor is created from the static characteristics (Ic-Vce characteristics, Id-Vds characteristics) of the power semiconductors in the shipping test (pre-shipment inspection) and reflected in the relational expression of the loss Loss. Thereby, considering the deterioration differences for each converter 32, the lifetime of each converter 32 can be predicted.

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

[0040] FIG. 5 is a first diagram for explaining the functions of the control device according to the first embodiment. The life prediction unit 112 has information in which the consumption life for each change cycle (one ΔT1) of the junction temperature Tj is tabulated by the rainflow method. Further, the life prediction unit 112 estimates the operation pattern (how many temperature changes are repeated for how many cycles) of each converter 32 at the assumed operation time based on past operation data and the operation conditions acquired in step S102. During a period when there is no accumulation of operation data, the life prediction unit 112 may estimate the operation pattern based on predetermined provisional data. For example, assume that an operation pattern as shown in FIG. 5 is estimated. The life prediction unit 112 calculates the consumption life from the estimated operation pattern based on ΔT and the number of times thereof at the assumed operation time. For example, in the example of FIG. 5, assume that ΔT1 = 40 degrees and ΔT2 = 30 degrees. Also, according to the consumption life table, assume that when the temperature change of 40 degrees is repeated X1 times, which is the upper limit cycle number, the life is reached (100% of the life is consumed). Also, assume that when the temperature change of 30 degrees is repeated X2 times, which is the upper limit cycle number, the life is reached. At this time, the consumption life for one cycle of ΔT1 is 1 / X1, and the consumption life for one cycle of ΔT2 is 1 / X2. That is, the consumption life for each ΔT is obtained as the reciprocal of the upper limit cycle number for each temperature. The life prediction unit 112 sums up the consumption life for each ΔT and calculates the consumption life of each converter 32 in the entire operation pattern.

[0041] Next, the cost loss prediction unit 113 predicts the consumption cost of each converter 32 (step S106). The method for obtaining the consumption cost is the same as in step S104. The cost loss prediction unit 113 predicts the consumption cost of the converter 32 assuming that the cost consumed for the replacement cost when the life of the converter 32 reaches the set life (lower limit value of deterioration) is proportional to the ratio of the consumption life to the total life of the converter 32. For example, assume that the lower limit value of deterioration of the converter 32A is 30%, the consumption life is 8%, and the replacement cost is 1.4 million yen. That is, assume that the replacement cost corresponding to 8% of 100 - 30 = 70 [%] of the life is consumed. That is, the consumption cost C of the converter 32A = 140 × 8 / 70 = 160,000 yen. The cost loss prediction unit 113 predicts the consumption cost for the other converters 32B to 32E in the same manner.

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

[0043] FIG. 6 is a second diagram for explaining the function of the control device according to the first embodiment. As shown in FIG. 6, it is assumed that the total cost loss Ct was 425,000 yen for the load factor (first load factor) calculated in step S101. Next, the load factor adjustment unit 114 searches for the load factor at which the total cost loss becomes the first 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 the second total cost loss 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 in which 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 at the first load factor is decreased, and the load factors of the other storage battery units 31 are increased. 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 decreases the load factor of the storage battery unit 31A by a predetermined amount, and sets a second load factor obtained by distributing 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%. Also, 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] Also, the control unit 115, the life prediction unit 112, and the cost loss prediction unit 113 perform the processes of steps S102 to S107 again to predict the 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 < 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 cost loss Ct is smaller (step S109; NO), this first total cost loss Ct becomes the minimum cost loss. Therefore, the load factor adjustment unit 114 determines the condition (first load factor) of this first total cost loss Ct as final. Then, the control unit 115 sets a control command (droop control command) for each battery unit 31 based on the determined first load factor. In this way, the load factor adjustment unit 114 repeatedly performs the process of rewriting the first load factor with the value of the second load factor until the first total cost loss Ct of the first load factor becomes the minimum, and obtaining the second total cost loss Ct+1 with the new second load factor (step S108).

[0048] FIG. 7 is a third diagram for explaining 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. The total cost loss was 425,000 yen at the load factor shown in FIG. 6, but by adjusting the load factor as shown in FIG. 7, the total cost loss could be reduced to 423,000 yen. That is, the converter 32A of the battery unit 31A could be made to have a longer life and the operating cost of the power storage system 3 could be reduced compared to the initial load factor (FIG. 6).

[0049] (Operation, Effect) As described above, the control device 10 of the power storage system 3 according to the present embodiment includes a life prediction unit 112 that predicts the consumption life of each of the power storage battery 33 and the converter 32 according to the load factor of the charge-discharge power assigned to each power storage battery unit 31, a cost loss prediction unit 113 that predicts the consumption cost of each of the power storage battery 33 and the converter 32 according to the load factor based on the consumption life, a load factor calculation unit 111 that calculates a first load factor for each power storage battery unit 31 based on the state of the power storage battery 33, and a load factor adjustment unit 114 that adjusts the first load factor so that the total cost loss Ct obtained by summing up the consumption costs of all the power storage batteries 33 and converters 32 is minimized.

[0050] For example, when there are five power storage battery units and it is desired to output 100 kW in total, ideally each power storage battery unit should output 20 kW. However, in reality, due to factors such as individual differences in converters and power storage batteries and the fact that some power storage battery units are placed in a thermally severe environment due to the layout relationship, even if the same current is passed through each power storage battery unit, the degradation rate may be different. Therefore, in the conventional technology, in order to extend the expected life of the power storage battery, the load factor was calculated so that the SOH of each power storage battery was substantially uniform and input to each converter. However, in the conventional technology, the extension of the long life of the converter, which is less expensive than the power storage battery, has not been fully considered. In contrast, the control device 10 according to the present embodiment can reduce the consumption life of both the power storage battery 33 and the converter 32 and extend their long life by minimizing the total cost loss Ct, which is the sum of the consumption costs of the power storage battery 33 and the converter 32, and can also reduce the operation cost of the entire power storage system 3.

[0051] Further, the load factor adjustment unit 114 reduces the first load factor of the battery unit 31 with the highest total consumption cost of the storage battery 33 and the converter 32 by a predetermined amount, distributes and adds a predetermined amount to the first load factors of the other battery units 31, and sets the second load factor, which is the adjusted load factor. When the second total cost loss Ct+1 of the second load factor is smaller than the first total cost loss Ct of the first load factor, the process of rewriting the first load factor with the value of the second load factor until the first total cost loss Ct of the first load factor becomes the minimum and predicting the consumption cost with the new second load factor is repeatedly performed.

[0052] By doing so, it is possible to more reliably achieve the extended life of the storage battery 33 and the converter 32 and the reduction of the operation cost of the entire power storage system 3.

[0053] The cost loss prediction unit 113 predicts the consumption cost of the storage battery 33 and the converter 32 on the assumption that, regarding the replacement cost when the lives of the storage battery 33 and the converter 32 reach the set life, a cost corresponding to the ratio of the consumption life to the total life of the storage battery 33 and the converter 32 is consumed.

[0054] By doing so, the control device 10 can accurately predict the consumption cost of the storage battery 33 and the converter 32.

[0055] <Second Embodiment> Next, the second embodiment will be described with reference to FIGS. 8 to 13. The same reference numerals are given to the components common to the above-described embodiments, and the detailed description thereof will be omitted.

[0056] The storage battery 33 and the converter 32 each have an individual difference in strength against deterioration. In the present embodiment, by changing the combination of the storage battery 33 and the converter 32 based on the strength against deterioration of each of the storage battery 33 and the converter 32, the extended life of the battery unit 31 and the reduction of the operation cost are achieved.

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

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

[0059] Also, the control device 10 may further include a display device 15. The strength of each storage battery 33 and each converter 32 estimated by the strength estimation unit 116 is displayed on the display device 15 and can be viewed by an operator who performs maintenance of the power storage system 3 or the like. Also, the strength estimated by the strength estimation unit 116 may be transmitted to other devices such as a server or a terminal device used by the operator.

[0060] FIG. 9 is a flowchart showing an example of an assembly method of a power storage system according to a second embodiment. Here, an example of an assembly method before the start of operation (at the time of new introduction) of the power storage system 3 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 semiconductor of each converter 32 in the shipping test (pre-shipment inspection) with the serial number of the converter 32 (step S201). Note that the static characteristics of the power semiconductor are obtained from a data sheet provided by the manufacturer of the power semiconductor. At this time, the strength estimation unit 116 may estimate the strength against deterioration from the static characteristics of the power semiconductor and associate it with the serial number of each converter 32. The strength against deterioration may be represented in three levels such as strong, medium, and weak, for example. Note that the strength estimation unit 116 estimates that the higher the resistance value of the power semiconductor, the weaker the strength against deterioration.

[0062] Further, the strength estimation unit 116 associates the cell battery capacity data of each storage battery 33 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 greater the cell battery capacity, the stronger the strength against deterioration, and associate the estimation result with the serial number of each converter 32.

[0063] The information associated by the strength estimation unit 116 is attached to the casings of the storage battery 33 and the converter 32 by a two-dimensional code such as a QR code (registered trademark). The installer (assembler) of the power storage system 3 determines the superiority or inferiority of the strength against deterioration of the storage battery 33 and the converter 32 by reading this QR code (step S203).

[0064] Further, the installer arranges the storage battery 33 and the converter 32 in order so that they are combined with those having strong strength and those having weak strength based on the superiority or inferiority relationship between the storage battery 33 and the converter 32.

[0065] FIG. 10 is a diagram for explaining a method of assembling a power storage system according to the second embodiment. For example, as shown in FIG. 10(a), assume that the strengths of the storage batteries 33A, 33B, and 33C are medium, strong, and weak, respectively, and the strengths of the converters 32A, 32B, and 32C are medium, weak, and strong, respectively. Here, when combined without considering the strengths of the storage battery 33 and the converter 32 as in the example of FIG. 10(a), for example, the converter 32B with a weak strength may be combined with the storage battery 33B with a strong strength. Then, for the converter 32B, if the consumption life and consumption cost of the converter 32B are predicted according to the static characteristics of the converter 32B as in the first embodiment, since the strength against deterioration is weak, the consumption cost tends to be relatively large, and the load factor for this converter 32B may decrease. Then, for the storage battery 33B combined with this converter 32B, the strength against deterioration cannot be fully utilized. Also, for the combination of the converter 32C and the storage battery 33C, an imbalance in strength against deterioration occurs. In such an unbalanced storage battery unit 31, there is a possibility that the strength cannot be fully utilized, or a load may be applied although the strength is insufficient.

[0066] On the other hand, as shown in FIG. 10(b), by combining the converter 32C, which also has a strong strength, with the storage battery 33B having a strong strength, the imbalance is eliminated, and a configuration is achieved in which the strengths of the storage battery 33B and the converter 32C against deterioration can be fully utilized. Also, in the combination of the storage battery 33C and the converter 32B, which is a combination with a weak strength, the possibility of an 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 male connector 36 of the converter 32 may be attachable by inserting it into the female connector 35 of the substrate 34. In the examples of FIGS. 10(b) and 11, by swapping the converter 32B and the converter 32C, it is possible to easily configure each storage battery unit 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. Also, as shown in FIG. 12, during the operation of the power storage system 3, the degree of deterioration of the storage battery 33 and the converter 32 may be evaluated, and the combination of the storage battery 33 and the converter 32 may be changed. For example, the control device 10 executes a series of processes shown in FIG. 12 at the timing when the SOH of each storage battery 33 is measured.

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

[0070] Also, the strength estimation unit 116 acquires the past average load factor of each storage battery 33 (step S212). In the storage 13, a history of the load factors determined by the load factor adjustment unit 114 is recorded, and the strength estimation unit 116 obtains the average value of the load factors from the start of operation of the power storage system 3 to the present from this history.

[0071] The strength estimation unit 116 calculates the life loss of the converter 32 (step S213). For example, a history of the current values applied to each converter 32 is recorded in the storage 13, and the strength estimation unit 116 calculates the life deterioration of each converter 32 based on this history such that the higher the current value, the higher the degree of deterioration.

[0072] Also, the strength estimation unit 116 acquires the past average load factor of each converter 32 (step S214).

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

[0074] Further, the strength estimation unit 116 determines the combination of the storage battery 33 and the converter 32 based on the coefficient α (step S216). For example, the smaller the coefficient α is, the stronger the strength against deterioration is determined by the strength estimation unit 116, and the combination of the storage battery 33 and the converter 32 is determined so that the combination is between those with strong strength and those with weak strength. The determined combination is displayed on the display device 15 and presented to the operator. In other embodiments, the strength estimation unit 116 may display the coefficient α of the storage battery 33 and the converter 32 on the display device 15, and the operator may determine the combination based on the coefficient α.

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

[0076] FIG. 13 is a diagram for explaining a method of changing the configuration of the power storage system according to the second embodiment. Due to the influence of the arrangement of the storage battery 33, etc., for example, as shown in FIG. 13(a), it is assumed that the deterioration of the storage battery 33B has progressed and the strength against deterioration has become weak (the coefficient α has become large). Then, the strength against deterioration becomes unbalanced between the storage battery 33B and the converter 32C, and it may become difficult to optimize the load factor. Therefore, as shown in FIG. 13(b), the strength estimation unit 116 determines to combine the storage battery 33B and the converter 32C and combine the storage battery 33C and the converter 32B based on the strength (coefficient α), and presents it to the operator. The operator swaps the converter 32B and the converter 32C according to the presented combination.

[0077] By doing so, the control device 10 can present to the operator a combination that can eliminate the imbalance in the strength against deterioration between the storage battery 33 and the converter 32. As a result, it becomes 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> As described above, one embodiment has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like are possible. That is, in other embodiments, the order of the above-described processes may be appropriately changed. Also, some processes may be executed in parallel.

[0079] <Appendix> The control device of the power storage system, the power storage system, the control method of the power storage system, and the program described in the above embodiment are understood as follows, for example.

[0080] (1) According to the first aspect, the control device 10 of the power storage system 3 is a control device 10 of the power storage system 3 that connects a plurality of power storage battery units 31 having a power storage battery 33 and a converter 32 for converting charge and discharge power to the power storage battery 33 in parallel via a DC bus 4. The control device 10 includes a life prediction unit 112 that predicts the consumption life of each of the power storage battery 33 and the converter 32 according to the load factor of the charge and discharge power assigned to each of the power storage battery units 31, a cost loss prediction unit 113 that predicts the consumption cost of each of the power storage battery 33 and the converter 32 according to the load factor based on the consumption life, a load factor calculation unit 111 that calculates a first load factor for each of the power storage battery units 31 based on the state of the power storage battery 33, and a load factor adjustment unit 114 that adjusts the first load factor so that the total cost loss obtained by summing the consumption costs of all the power storage batteries 33 and converters 32 is minimized.

[0081] For example, when there are five battery units and it is desired to output a total of 100 kW, ideally each battery unit should output 20 kW. However, in reality, due to factors such as individual differences in converters and batteries, and the relationship of the arrangement where only some battery units are placed in a thermally severe environment, even if the same current is passed through each battery unit, the degradation rates may be different. For this reason, in the conventional technology, in order to extend the expected life of the battery, the load factor was calculated so that the SOH of each battery would be approximately uniform and input to each converter. However, in the conventional technology, the long life of the converter, which is less expensive compared to the battery, has not been fully considered. On the other hand, the control device 10 according to the present embodiment can reduce the consumption life of both the battery 33 and the converter 32 and extend their life by minimizing the total cost loss Ct, which is the sum of the consumption costs of the battery 33 and the converter 32 as described above, and can also reduce the operation cost of the entire power storage system 3.

[0082] (2) According to the second aspect, in the control device 10 of the power storage system 3 according to the first aspect, the load factor adjustment unit 114 reduces the first load factor of the battery unit 31 with the highest total consumption cost of the battery 33 and the converter 32 by a predetermined amount, distributes and adds a predetermined amount to the first load factors of the other battery units 31, sets the second load factor, which is the adjusted load factor, and when 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 becomes the minimum, and the process of predicting the consumption cost with the new second load factor is repeatedly performed.

[0083] By doing so, it is possible to more surely achieve the extension of the life of the battery 33 and the converter 32 and the reduction of the operation cost of the entire power storage system 3.

[0084] (3) According to the third aspect, in the control device 10 of the power storage system 3 according to the first or second aspect, the cost loss prediction unit 113 assumes that, for the replacement cost when the lives of the storage battery 33 and the converter 32 reach the set life, the cost consumed is in accordance with the ratio of the consumed life to the total life of the storage battery 33 and the converter 32, and predicts the consumption cost of the storage battery 33 and the converter 32.

[0085] By doing so, the control device 10 can accurately predict the consumption cost of the storage battery 33 and the converter 32.

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

[0087] By doing so, the control device 10 can present to the operator a combination that can eliminate the imbalance in strength against deterioration between the storage battery 33 and the converter 32. Thereby, it becomes 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 the fifth aspect, the power storage system 3 includes a plurality of power storage battery units 31 each having a storage battery 33 and a converter 32 for converting charge and discharge power with respect to the storage battery 33, and a control device 10 according to any one of the first to fourth aspects.

[0089] The power storage system 3 can reduce the consumed life of both the storage battery 33 and the converter 32 and extend their lives by minimizing the total cost loss Ct, which is the sum of the consumption costs of the storage battery 33 and the converter 32, and can also reduce the operation cost of the entire power storage system 3.

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

[0091] By doing so, the power storage system 3 can present to the operator a combination that can eliminate the imbalance in strength against deterioration between the storage battery 33 and the converter 32. Thereby, it becomes 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 the 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 power storage units 31 each having a storage battery 33 and a converter 32 for converting charge and discharge power to the storage battery 33 are connected in parallel via a DC bus 4, the method including: predicting the consumption life of each of the storage battery 33 and the converter 32 according to the load factor of the charge and discharge power assigned to each power storage unit 31; predicting the consumption cost of each of the storage battery 33 and the converter 32 according to the load factor based on the consumption life; calculating a first load factor for each power storage unit 31 based on the state of the storage battery 33; and adjusting the first load factor so that the total cost loss obtained by summing up the consumption costs of all the storage batteries 33 and converters 32 is minimized.

[0093] (8) According to the eighth aspect, the program causes the control device 10 of the power storage system 3 that connects a plurality of power storage units 31 having a power storage battery 33 and a converter 32 for converting charge and discharge power with respect to the power storage battery 33 in parallel via a DC bus 4 to execute steps of predicting the consumption life of each of the power storage battery 33 and the converter 32 according to the load factor of the charge and discharge power assigned to each power storage unit 31, predicting the consumption cost of each of the power storage battery 33 and the converter 32 according to the load factor based on the consumption life, calculating a first load factor for each power storage unit 31 based on the state of the power storage battery 33, and adjusting the first load factor so that the total cost loss obtained by summing up the consumption costs of all the power storage batteries 33 and the converters 32 becomes minimum.

Explanation of Signs

[0094] 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 Life 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 Power storage unit 31 Power storage unit 32 Converter 33 Power storage battery 34 Substrate 35 Female connector 36 Male connector

Claims

1. A control device for a power storage system that connects in parallel a plurality of power storage units each having a storage battery and a converter for converting charge and discharge power with respect to the storage battery via a DC bus, a life prediction unit that predicts the consumption life of each of the storage battery and the converter according to the load factor of the charge and discharge power assigned to each of the power storage units, a cost loss prediction unit that predicts the consumption cost of each of the storage battery and the converter according to the load factor based on the consumption life, a load factor calculation unit that calculates a first load factor for each of the power storage units based on the state of the storage battery, a load factor adjustment unit that adjusts the first load factor so that the total cost loss obtained by summing the consumption costs of all the storage batteries and converters is minimized, A control device for a power storage system comprising the above.

2. The load factor adjustment unit, reduces the first load factor of the power storage unit with the highest total consumption cost of the storage battery and the converter by a predetermined amount, distributes and adds the predetermined amount to the first load factors of the other power storage units, and sets a second load factor which is the adjusted load factor, when the second total cost loss of the second load factor is smaller than the 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 repeatedly performs a process of predicting the consumption cost with the new second load factor. The control device for a power storage system according to Claim 1.

3. The cost loss prediction unit predicts the consumption cost of the storage battery and the converter on the assumption that, regarding the replacement cost when the lives of the storage battery and the converter reach the set life, a cost corresponding to the ratio of the consumption life to the total life of the storage battery and the converter is consumed. The control device for a power storage system according to Claim 1.

4. 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 the average load factor of each of the storage battery and the converter. The control device for a power storage system according to any one of Claims 1 to 3.

5. A power storage system comprising a storage battery, a plurality of power storage units each having a converter for converting charge and discharge power with respect to the storage battery, and the control device according to any one of Claims 1 to 3. A power storage system comprising the above.

6. The control device further includes a strength estimation unit that estimates the strength against deterioration of each of the storage battery and the converter from the life loss and the average load factor of each of the storage battery and the converter. The converter can be combined with the storage battery based on the strength. The power storage system according to claim 5.

7. A method for controlling a power storage system in which a plurality of power storage units each having a storage battery and a converter for converting charge and discharge power to the storage battery are connected in parallel via a DC bus, predicting the consumption life of each of the storage battery and the converter according to the load factor of the charge and discharge power assigned to each of the power storage units; predicting the consumption cost of each of the storage battery and the converter according to the load factor based on the consumption life; calculating a first load factor for each of the power storage units based on the state of the storage battery; adjusting the first load factor so that the total cost loss obtained by summing the consumption costs of all the storage batteries and the converters is minimized; A method for controlling a power storage system having the above steps.

8. In a control device for a power storage system in which a plurality of power storage units each having a storage battery and a converter for converting charge and discharge power to the storage battery are connected in parallel via a DC bus, predicting the consumption life of each of the storage battery and the converter according to the load factor of the charge and discharge power assigned to each of the power storage units; predicting the consumption cost of each of the storage battery and the converter according to the load factor based on the consumption life; calculating a first load factor for each of the power storage units based on the state of the storage battery; adjusting the first load factor so that the total cost loss obtained by summing the consumption costs of all the storage batteries and the converters is minimized; A program for executing the above steps.

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