Battery system operation device, battery system operation method, and program

Abstract

Provided is a battery system operation device that makes it possible to propose an appropriate system expansion period for a secondary battery system. For this purpose, a battery system operation device (100) is provided with: a battery deterioration calculation unit (102) that calculates a first transition prediction, which is a prediction of a future transition in the deterioration degree of a first battery group, and a second transition prediction, which is a prediction of a future transition in the deterioration degree of a second battery group having a different deterioration degree than the first battery group; a battery deterioration degree comparison unit (103) that, on the basis of the first and second transition predictions, calculates an equivalence condition satisfaction period, which is a period which the first and second battery groups will satisfy a prescribed equivalence condition; and a system expansion period calculation unit (105) that, on the basis of the equivalence condition satisfaction period, determines or proposes a system expansion period, which is a period in which a secondary battery is to be added to the battery system.

Description

Battery System Operation Device, Battery System Operation Method, and Program

[0001] The present invention relates to a battery system operation device, a battery system operation method, and a program.

[0002] As the main power source of renewable energy such as wind power and solar power progresses towards realizing a carbon-neutral society, the introduction of stationary battery energy storage systems (BESS: Battery Energy Storage System) as a battery system that bears the adjustment power to eliminate system instability is advancing. In the operation process of the power storage system, the available battery capacity decreases due to the deterioration of the secondary battery. Therefore, it is necessary to design the initial capacity of the system in anticipation of the deterioration of the secondary battery with respect to the battery capacity to be covered by the power storage system. However, if a system is designed to carry an excessive number of batteries for stable operation, the introduction cost of the power storage system will increase. Therefore, as a method for reducing the introduction cost of the power storage system, while designing a small margin of the initial capacity with respect to the battery capacity to be covered by the system, the capacity of the entire power storage system is ensured by appropriately adding batteries according to the deterioration of the secondary battery, and system augmentation is used. As an example, Non-Patent Document 1 describes a method for determining the augmentation timing in the operation method of a battery system including system augmentation.

[0003] Hunyong Shin, et al., Optimal Energy Storage Sizing With Battery Augmentation for Renewable-Plus-Storage Power Plants, IEEE Access 8 (2020): 187730-187743, [online], [searched on November 15, 2023], Internet <URL: https: / / ieeexplore.ieee.org / stamp / stamp.jsp?tp=&arnumber=<9223659>

[0004] However, in the above-mentioned technology, there is a demand for being able to propose a more appropriate system expansion timing for a secondary battery system. The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a battery system operation device, a battery system operation method, and a program that can propose an appropriate system expansion timing for a secondary battery system.

[0005] In order to solve the above problem, the battery system operation device of the present invention is characterized by comprising: a battery deterioration calculation unit that calculates a first transition prediction that is a transition prediction of the future degree of deterioration of a first battery group included in a battery system and having one or more secondary batteries; and a second transition prediction that is a transition prediction of the future degree of deterioration of a second battery group included in the battery system and having a different degree of deterioration than the first battery group; a battery deterioration level comparison unit that calculates, based on the first and second transition predictions, the time when the first and second battery groups will satisfy a specified equalization condition; and a system expansion time calculation unit that determines or proposes the time when a secondary battery will be added to the battery system based on the time when the equalization condition is satisfied.

[0006] According to the present invention, it is possible to propose an appropriate timing for system expansion for a secondary battery system.

[0007] FIG. 1 is a diagram showing an example of the transition of system capacity in a comparative example. FIG. 2 is a diagram showing an example of the configuration of a battery system applied to the first embodiment. FIG. 3 is a block diagram of a battery system operation device according to the first embodiment. FIG. 4 is a hardware configuration diagram of a battery system operation device. FIG. 5 is a diagram showing an example of the configuration of a battery system after system expansion. FIG. 6 is a diagram showing an example of an SOHQ transition curve in the first embodiment. FIG. 7 is a diagram showing an example of change in system capacity in the first embodiment. FIG. 8 is an example of calculation of the transition of the minimum SOHQ of a battery rack in a battery system. FIG. 9 is an example of change in system capacity of the entire battery system. FIG. 10 is an example of calculation of the transition of life cycle cost in the first embodiment and the comparative example. FIG. 11 is a diagram showing an example of an SOHQ transition curve in the second embodiment.

[0008] [Overview of the embodiment] A secondary battery system generally includes multiple secondary batteries. The sum of the battery capacities of these secondary batteries is called the system capacity Qs (see FIG. 1 ). The minimum value allowed for the system capacity Qs is called the required value Qsmin. By applying the content of Non-Patent Document 1 mentioned above, it is believed possible to predict the deterioration of secondary batteries and predict the timing at which the predicted system capacity Qs will reach the required value Qsmin. It is believed possible to then add a secondary battery at that timing to increase the system capacity Qs.

[0009] FIG. 1 is a diagram showing an example of the transition of system capacity Qs in a comparative example. Note that this comparative example applies the content of the aforementioned Non-Patent Document 1. In FIG. 1, system capacity Qs decreases over time t according to capacity characteristic Qs1. Then, at time t1, system capacity Qs reaches the required value Qsmin. Therefore, at or before time t1, a new secondary battery is added to the secondary battery system, and the system is expanded. As a result, the system capacity Qs thereafter becomes as shown by capacity characteristic Qs2, and the system capacity Qs can be continuously maintained at or above the required value Qsmin.

[0010] However, expanding the system by connecting batteries with different operational histories can cause problems such as an increase in the life cycle cost of the battery system. In view of this, the embodiment described below proposes a system expansion timing for adding batteries so as to reduce the life cycle cost of the battery system.

[0011] [First embodiment] <Configuration of battery system BS> Figure 2 is a diagram showing an example of the configuration of a battery system BS applied to the first embodiment. The battery system BS includes multiple (four in the illustrated example) banks 10-1 to 10-4. In the following description, multiple components, information, etc. having the same or similar functions or significance may be represented by the same reference numeral with a "-" and alphanumeric characters added, such as "bank 10-1, bank 10-2." However, when it is not necessary to distinguish between these multiple components, etc., the "-" and alphanumeric characters may be omitted, such as "bank 10."

[0012] Each of the banks 10-1 to 10-4 includes one PCS (Power Conditioning System) 11-1 to 11-4, one container 12-1 to 12-4, and multiple battery racks 14. Each battery rack 14 houses one or more secondary battery cells (not shown), and each container 12 is a housing that houses one or more battery racks 14. More specifically, container 12-1 of bank 10-1 houses battery racks 14-11, 14-12, and 14-13, container 12-2 of bank 10-2 houses battery racks 14-21, 14-22, and 14-23, container 12-3 of bank 10-3 houses battery racks 14-31, 14-32, and 14-33, and container 12-4 of bank 10-4 houses battery racks 14-41, 14-42, and 14-43.

[0013] In this embodiment, the multiple battery racks 14 housed in each container 12 are connected in parallel. However, in each container 12, these battery racks 14 may also be connected in series. In the illustrated example, the battery system BS includes four banks 10-1 to 10-4, but the number of banks 10 may be changed depending on the capacity and output required for the battery system BS. Also, in the illustrated example, one bank 10 includes three battery racks 14, but the number of battery racks 14 may be changed in a similar manner.

[0014] <Configuration of First Embodiment> Figure 3 is a block diagram of a battery system operation device 100 (computer) according to the first embodiment. This battery system operation device 100 is a device that determines or proposes the timing of adding battery racks 14 to a battery system BS (see Figure 2). In Figure 3, the battery system operation device 100 includes a battery system information input unit 101, a battery degradation calculation unit 102 (battery degradation calculation process, battery degradation calculation means), a battery degradation level comparison unit 103 (battery degradation level comparison process, battery degradation level comparison means), a battery system capacity calculation unit 104 (system expansion timing calculation process, system expansion timing calculation means), and a system expansion timing calculation unit 105.

[0015] Battery system information including a secondary battery specification data DB, degradation state data DH, system configuration data DS, required value Qsmin (see FIG. 1 ) operation data DL, and economic index data DE is input to the battery system information input unit 101. The secondary battery specification data DB is data that defines the specifications of each battery rack 14 and the secondary batteries (not shown) housed therein.

[0016] The degradation state data DH is data that defines the SOH (State of Health) of each battery rack 14. The SOH includes various battery characteristics, such as SOHQ for capacity and SOHR for resistance. SOHQ is generally expressed as a percentage, with SOHQ being 100 for a brand new battery before degradation and gradually decreasing as the battery deteriorates. Meanwhile, SOHR is also generally expressed as a percentage, with SOHR being 100 for a brand new battery before degradation and gradually increasing as the battery deteriorates.

[0017] The system configuration data DS includes the number of battery racks 14 connected in series or in parallel, the number of PCSs 11, etc. The operation data DL is time-series data on the current values, voltage values, input / output energy values, temperature, etc. of the battery system BS and each battery rack 14. The economic indicator data DE is data on economic indicators for cost calculation, and includes the equipment cost, operation and maintenance cost, electricity charges, discount rates, etc.

[0018] The battery deterioration calculation unit 102 stores deterioration prediction model data DM that defines the change state of the SOH in accordance with the input secondary battery specification data DB. A deterioration prediction model based on the physical mechanism of the battery is applied to the deterioration prediction model data DM. However, the deterioration prediction model data DM is not limited to this, and a semi-empirical model, a machine learning model, or the like may also be applied.

[0019] The battery degradation calculation unit 102 then calculates future changes in the SOH of each battery rack 14 using the current and past battery state history, such as the SOH, of each battery rack 14, the current and past operation history of each battery rack 14, and the degradation prediction model data DM. In this embodiment, the SOHQ, among the SOH, is used as an indicator of battery degradation. This allows the battery degradation calculation unit 102 to calculate the SOHQ transition characteristics of each battery rack 14. However, the indicator of battery degradation is not limited to SOHQ, and SOH defined with focus on SOHR or other characteristics may also be used.

[0020] The battery degradation level comparison unit 103 compares the SOHQ transition curves of the individual battery racks 14 obtained by the battery degradation calculation unit 102. In particular, the battery degradation level comparison unit 103 calculates the equalization condition fulfillment time, which is the time at which the SOHQs of two or more battery racks 14 originally having different SOHQs will satisfy a predetermined equalization condition at a certain time in the future, and the SOHQ values ​​of these battery racks 14 at that time. Here, the "predetermined equalization condition" means that the relative ratio of the SOHQs of these battery racks 14 falls within a predetermined range, and this "predetermined range" can be, for example, "±10%, ±5%, ±2%, etc. In the following description, "satisfying the predetermined equalization condition" may also be referred to as "approximate equality."

[0021] The battery system capacity calculation unit 104 calculates the change in the system capacity Qs of the entire battery system BS based on the SOHQ transition curves of the individual battery racks 14 obtained by the battery deterioration calculation unit 102. The system expansion timing calculation unit 105 calculates the system expansion timing for adding battery racks 14 based on the relationship between the approximate equality information of the individual battery SOHQs obtained by the battery deterioration level comparison unit 103, the transition of the system capacity Qs obtained by the battery system capacity calculation unit 104, and the required value Qsmin.

[0022] That is, the system expansion timing calculation unit 105 selects, as the system expansion timing, a timing when the following conditions are met: the system capacity Qs is equal to or greater than the required value Qsmin; and the SOHQs of the multiple battery racks 14 are approximately equal. The system expansion timing calculation unit 105 also calculates the life cycle cost when the system expansion is performed at the specified system expansion timing. The life cycle cost may be, for example, the levelized cost of storage (LCOS). However, the system expansion timing calculation unit 105 is not limited to LCOS; it may also calculate other indices that express the life cycle cost of the battery system.

[0023] FIG. 4 is a hardware configuration diagram of the battery system operation device 100. The input device 201 is a device for inputting various data and can be configured, for example, by a keyboard, mouse, touchpad, battery rack ball, etc. The input device 201 embodies the functional units of the battery system information input unit 101. The storage device 204 can be configured, for example, by RAM (Random Access Memory), ROM (Read Only Memory), flash memory, hard disk, optical disk, etc. Part or all of the storage device 204 may be integrated with the computer 202. The storage device 204 stores various data input by the user, parameters for predicting battery deterioration, programs for causing the computer 202 to perform battery deterioration, system expansion timing evaluation, cost calculation, etc.

[0024] The computer 202 is a device that performs numerical analysis using input data and embodies the battery deterioration calculation unit 102, battery deterioration level comparison unit 103, battery system capacity calculation unit 104, and system expansion timing calculation unit 105 shown in FIG. 3 . By executing a predetermined calculation program, the computer 202 reads input battery system information and pre-prepared deterioration prediction model data DM, etc., and performs calculation processing using these to calculate the system expansion timing. Note that the computer 202 may be a device in which the predetermined calculation program used for the numerical analysis is directly incorporated into an arithmetic circuit, or may be a device that reads and executes a predetermined calculation program stored externally. The computer 202 may also have a function for performing various processes, such as display processing.

[0025] The calculator 202 may be configured with various types of computing devices, such as an arithmetic circuit such as an integrated circuit, a central processing unit (CPU) incorporating memory and registers, etc. The display device 203 displays the results of calculations performed by the calculator 202 and displays various information to the user based on instructions from the calculator 202. The displayed content may be numerical values ​​themselves, or a distribution display using colors or textures corresponding to the numerical values. For example, based on instructions from the system expansion timing calculation unit 105 (see FIG. 3 ), the display device 203 displays the SOHQ transition curves Q14 and Q16 (see FIG. 6 ), as well as predicted values ​​of battery degradation, changes in battery system capacity, life cycle costs, and the determined or proposed system expansion timing. The display device 203 may be configured with, for example, a liquid crystal display, a plasma display, an organic electroluminescence (EL) display, a cathode ray tube, etc.

[0026] Figure 5 shows an example configuration of the battery system BS after system expansion. When it is predicted that the system capacity Qs will fall below the required value Qsmin due to capacity degradation of the battery system BS, all battery racks 14 included in the bank 10-4 (see Figure 2) before expansion are relocated to other banks 10. That is, as shown in Figure 5, battery racks 14-41, 14-42, and 14-43 are relocated to banks 10-1, 10-2, and 10-3, respectively. As a result, for example, battery rack 14-41 is connected in parallel to battery racks 14-11, 14-12, and 14-13. These battery racks 14-11 to 14-43, which were installed before the system expansion, are collectively referred to as the battery rack group Ga (first battery group).

[0027] Furthermore, as shown in FIG. 5, other battery racks 14-51, 14-52, and 14-53 are added to the empty space in bank 10-4 created by this rearrangement. This increases the overall system capacity Qs of the battery system BS. These added battery racks 14-51, 14-52, and 14-53 are collectively referred to as the battery rack group Gb (second battery group). The number of battery racks 14 added may be changed depending on the desired capacity increase through system expansion. Furthermore, it is preferable that the SOHQ of the added battery rack group Gb be "100," i.e., that the battery rack group Gb is in an undegraded state. However, as long as a larger SOHQ than that of the battery rack group Ga can be ensured, the SOHQ of the battery rack group Gb may be a value less than "100."

[0028] The system expansion method shown in Figure 5 has the advantage of eliminating the need to add a new PCS 11 to the battery system BS, thereby reducing costs during expansion. As a result of extensive research by the inventors, it has been found that it is preferable to combine changes in the system capacity Qs of the battery system BS with changes in the deterioration level of the battery racks 14 that make up the system. This makes it possible to expand the system by connecting battery racks 14 with different operating histories while reducing the lifecycle cost of the battery system BS.

[0029] FIG. 6 is a diagram showing an example of an SOHQ transition curve in the first embodiment. In FIG. 6, the horizontal axis represents time t, and the vertical axis represents the SOHQ [%] of the battery rack 14. The SOHQ transition curve Q12 represents the transition of the SOHQ of the battery rack group Ga installed in the initial state. When multiple banks 10 are present as in the example of FIG. 2, the SOHQ of each battery rack 14 in the battery system BS can be changed, for example, along the curve Q12 by equally allocating loads to each bank 10. In the illustrated example, assume that the first system expansion, as shown in FIG. 5, was performed at time t10. After time t10, the SOHQ of the battery rack group Ga changes along the curve Q14 (first transition prediction) starting from time t10. Meanwhile, a larger load is assigned to the added battery rack group Gb than to the battery rack group Ga after time t10.

[0030] As a result, the SOHQ of the battery rack group Gb changes, for example, along the SOHQ transition curve Q16 (second transition prediction) in the figure. According to curve Q16, the SOHQ is 100% at time t10, and thereafter, curve Q16 drops more steeply than curve Q14. Then, at time t15 (when the equalization condition is satisfied), the SOHQ transition curves Q14 and Q16 intersect. Therefore, the equalization condition is satisfied at and around time t15. The curves Q14 and Q16 can be predicted by the battery degradation calculation unit 102 (see FIG. 3). This allows the battery degradation level comparison unit 103 to predict time t15 in advance during operation of the battery system BS after time t10. The SOHQ transition curve Q17 shows the change in the SOHQ of the battery rack group Gb assuming that the same load as before time t15 continues to be applied to the battery rack group Gb.

[0031] Here, the sum of the battery capacities of the battery rack group Ga is the battery capacity C a For example, if the SOHQs of the battery racks 14 belonging to the battery rack group Ga are the same, the sum of the initial capacities of these battery racks multiplied by the SOHQ is the battery capacity C a Similarly, the sum of the battery capacities of the battery rack group Gb is expressed as battery capacity C b (not shown).

[0032] The system expansion timing calculation unit 105 calculates a coefficient k that satisfies the following [Equation 1]. a , k b Define the coefficient k a , k b The load sharing between the battery rack groups Ga and Gb is set according to the ratio of

[0033] In [Equation 1], the coefficient k a , k b is a coefficient that determines the ratio of the load distribution shared by the battery rack groups Ga and Gb with respect to the total load of the battery system BS. a , k b Therefore, the battery deterioration calculation unit 102 calculates the coefficient k a , k b In other words, a plurality of types of combinations of SOHQ transition curves Q14 and Q16 corresponding to various load distribution candidates are output. In this way, the battery deterioration level comparison unit 103 calculates the equality condition fulfillment time (for example, time t15) corresponding to various load distribution candidates. For example, the coefficient k b If a value greater than "1" is set to k, then the coefficient k a becomes a value smaller than 1. This makes it possible to adjust the load of each battery rack 14 in the battery rack group Gb to be greater than the load of each battery rack 14 in the battery rack group Ga.

[0034] As a result of this adjustment, as described above, the slope of curve Q16 after time t10 becomes larger than the slope of curve Q14, and curves Q14 and Q16 intersect at time t15. This means that the equality condition is met at and around time t15, as described above. Therefore, it is advisable to perform a second system expansion during the period in which this equality condition is met, for example, at time t15.

[0035] In the second system expansion, similar to the first system expansion, the battery racks 14-51, 14-52, and 14-53 belonging to bank 10-4 (in other words, included in battery rack group Gb) may be moved to banks 10-1, 10-2, and 10-3, respectively, and a new battery rack 14 (not shown) may be added to the vacant bank 10-4.

[0036] In this way, by performing the second system expansion around time t15 when the intersection of curves Q14 and Q16 appears, the SOHQ of all battery racks 14 belonging to banks 10-1, 10-2, and 10-3 can be made approximately the same value. After time t15, it is advisable to make the load of the newly added battery rack 14 belonging to bank 10-4 relatively large and the load of the existing battery racks 14 belonging to banks 10-1, 10-2, and 10-3 relatively small.

[0037] As a result, in the illustrated example, the SOHQ of the newly added battery rack 14 belonging to bank 10-4 drops sharply as shown by SOHQ transition curve Q20. Also, the SOHQ of the battery racks 14 belonging to banks 10-1, 10-2, and 10-3 drops gradually as shown by SOHQ transition curve Q18 starting from time t15.

[0038] Figure 7 is a diagram showing an example of changes in system capacity Qs in the first embodiment. The capacity characteristic Qs30 shown by the solid line in the figure is the system capacity Qs achieved when the SOHQ of each battery rack 14 changes as shown in Figure 6. That is, as a result of the first and second system expansions at times t10 and t15, the capacity characteristic Qs30 rises at these times and gradually decreases during other periods. The capacity characteristic Qs32 shown by the dashed line indicates the change in system capacity Qs when no system expansion is performed.

[0039] 7, focusing on the required value Qsmin of the system capacity Qs, at time t15, the capacity characteristic Qs30 does not fall below the required value Qsmin. Therefore, it is possible to continue operating the battery system BS after time t15 without performing system expansion. In this case, the system capacity Qs decreases along the capacity characteristic Qs34 starting from time t15, and at time t20, the capacity characteristic Qs34 reaches the required value Qsmin.

[0040] Here, the comparative example will be described again. As explained in Fig. 1, in the comparative example, the timing when the system capacity Qs reaches the required value Qsmin is selected as the time for system expansion. Therefore, in the comparative example, at time t15 shown in Fig. 7, the operation of the battery system BS continues without performing system expansion, and time t20 is selected as the time for the second system expansion.

[0041] As shown in Figure 6, in this embodiment, it is assumed that a second system expansion will be performed at time t15, so curve Q16 ends at time t15. However, in the comparative example, a second system expansion is not performed at time t15, so the SOHQ of battery racks 14-51, 14-52, and 14-53 decreases along curve Q17 shown in Figure 6. In other words, the SOHQ of battery racks 14-51, 14-52, and 14-53 decreases significantly compared to the SOHQ of the other battery racks 14, which changes along SOHQ transition curve Q18.

[0042] In the comparative example, the second system expansion is performed at time t20 in Figure 7, and battery racks 14-51, 14-52, and 14-53, whose SOHQ has significantly decreased, are relocated to banks 10-1, 10-2, and 10-3. If the SOHQs of multiple interconnected battery racks 14 belonging to a certain bank 10 are different, the operation of that bank 10 must be reconsidered when the battery rack 14 with the relatively small SOHQ reaches the service limit Qmin (60% in the example of Figure 8 described below). In other words, the system expansion timing calculation unit 105 determines or proposes the time when the equalization condition is satisfied (e.g., time t15) as the time for system expansion, provided that the SOHQs of the battery rack groups Ga and Gb at that time are all equal to or greater than the service limit Qmin.

[0043] In this case, when the SOHQ of a particular battery rack 14 reaches 60%, even if the other battery racks 14 have SOHQs greater than 60% and are still usable, the lifespan of the bank 10 at that point becomes limited by the particular battery rack 14 whose SOHQ has reached 60%. In other words, the particular battery rack 14 whose SOHQ has reached 60% becomes a bottleneck. Furthermore, when multiple battery racks 14 are connected in series within a bank 10, the capacity of the bank 10 is determined by the battery rack 14 with the smallest SOHQ. Therefore, there is a problem in that the capacity of the bank 10 decreases significantly even before the end of its life.

[0044] In contrast, according to this embodiment, system expansion can be performed at a timing when the SOHQ of the existing battery racks 14 included in a certain bank 10 and the SOHQ of the battery racks 14 to be moved to that bank 10 are approximately equal. This makes it possible to prevent problems caused by multiple battery racks 14 with different SOHQs belonging to the same bank 10. In the above example, the usage limit Qmin was set to the timing when the SOHQ reached "60%." However, the usage limit Qmin may also be set to an SOHQ value other than "60%" in accordance with the characteristics of the secondary batteries and the system operation standards. Furthermore, the usage limit of the battery rack 14 may also be determined using an index other than SOHQ.

[0045] FIG. 8 shows an example of calculation of the transition of the minimum SOHQ of the battery racks 14 in the battery system BS. The SOHQ transition curve Q22 is an example of the transition of the minimum SOHQ according to this embodiment. That is, the curve Q22 is an example of the transition when the second system expansion is performed at time t15 (see FIG. 7) when the SOHQ of each battery rack 14 is approximately equal. The SOHQ transition curve Q24 is an example of the transition of the minimum SOHQ according to the comparative example. That is, the curve Q24 is an example of the transition when the second system expansion is performed at time t20 when the SOHQ of each battery rack 14 is not approximately equal. The usage limit Qmin of the battery rack 14 is assumed to be "60%."

[0046] In both curves Q22 and Q24, the battery rack 14 with the smallest SOHQ in the battery system BS reaches the service limit Qmin earlier than the other battery racks 14. According to curve Q22 of the present embodiment, the service limit Qmin is reached at time t35. On the other hand, according to curve Q24 of the comparative example, the service limit Qmin is reached at time t30, which is earlier than curve Q22 of the present embodiment. Therefore, according to the present embodiment, a longer lifespan can be achieved for the battery system BS than in the comparative example.

[0047] FIG. 9 shows an example of the change in the system capacity Qs of the entire battery system BS during the operation shown in FIG. 8 . The capacity characteristic Qs42 shows the change in the system capacity Qs according to this embodiment. Furthermore, the capacity characteristic Qs44 shown by the dashed line shows the change in the system capacity Qs according to the comparative example. As described above, in the comparative example, a second system expansion is performed at time t20. After that, the system capacity Qs according to the capacity characteristic Qs42 of the comparative example becomes larger than that according to the capacity characteristic Qs42 of this embodiment. However, as described in FIG. 8 , in the comparative example, the battery rack 14 with the smallest SOHQ reaches the service limit Qmin at time t30. On the other hand, according to this embodiment, the operation of the battery system BS can be continued until time t35. Therefore, if it is sufficient to satisfy the condition that the system capacity Qs is equal to or greater than the required value Qsmin, it is preferable to operate the battery system BS according to the capacity characteristic Qs42 of this embodiment.

[0048] Next, the life cycle cost (LCOS) will be described. The life cycle cost (LCOS) of the present embodiment and the comparative example can be calculated by the following [Equation 2].

[0049] In [Equation 2], n is the year after the battery system BS is put into operation, and its initial value is "1", which is incremented by "1" each year. N is the final year of the period for which the life cycle cost LCOS is calculated. CAPEX(n) is the equipment cost in year n, and in the first year (n = 1), it includes the cost of installing the battery system BS. In subsequent years, it also includes the cost of expanding the system. OPEX(n) is the operating cost in year n, and includes maintenance costs, etc. ECC(n) is the charging cost in year n, and includes the electricity fee required to charge the battery system BS. Eout(n) is the output energy in year n. d is the discount rate used to convert costs and energy into present value.

[0050] In this way, the life cycle cost LCOS can be calculated by converting the cost and the output energy Eout(n) for each fiscal year n into present value, adding them up over the total operation period, and calculating the ratio between the two. The life cycle cost LCOS is the system cost per unit of energy. For this reason, it is preferable for users of the battery system BS to introduce and operate the battery system BS so that the life cycle cost LCOS is small over the desired operation period.

[0051] FIG. 10 shows an example of calculation of the transition of life cycle costs in this embodiment and a comparative example. The transition curve LC1 in FIG. 10 shows the transition of the life cycle cost LCOS in this embodiment. The transition curve LC2 shows the transition of the life cycle cost LCOS in the comparative example. In this embodiment, as a result of the second system expansion being performed at time t15, the transition curve LC1 has a higher value than the transition curve LC2 around time t15. However, thereafter, the transition curve LC1 has a lower value than the transition curve LC2. Thus, according to this embodiment, the life cycle cost LCOS can be reduced in the long term compared to the comparative example.

[0052] [Second embodiment] Next, a battery system operation device according to a second embodiment will be described. The configuration of the battery system operation device according to the second embodiment is the same as that of the first embodiment (see FIG. 3) except for the following points. As previously explained in FIG. 6, the coefficient k a , k b Since there are multiple combinations of coefficient k a , k b By adjusting the SOHQ transition curves Q14 and Q16, it is possible to adjust the slopes of the SOHQ transition curves Q14 and Q16 and the timing at which they intersect. Therefore, in this embodiment, from among multiple candidates for the SOHQ transition curves Q14 and Q16, the one that results in the smallest life cycle cost LCOS is selected and applied.

[0053] 11 is a diagram showing an example of an SOHQ transition curve in the second embodiment. The SOHQ transition curve Q12 in FIG. 11 is the same as that shown in FIG. 6. The SOHQ transition curves Q14A and Q16A are also plotted using a coefficient k a , k b The curves Q14A and Q16A intersect at time t17 (the time when the equality condition is satisfied). The SOHQ transition curve Q18A represents the transition of the SOHQ of the existing battery rack 14 that was installed before the second system expansion at time t17. The SOHQ transition curve Q20A represents the transition of the SOHQ of the newly added battery rack 14 when the second system expansion is performed at time t17.

[0054] The system expansion time calculation unit 105 of this embodiment calculates the life cycle cost (LCOS) based on each operating condition for multiple system expansion time candidates (e.g., time t15 in FIG. 6 and time t17 in FIG. 11) that vary depending on the load distribution conditions.The system expansion time calculation unit 105 then selects the system expansion time candidate that results in the smallest life cycle cost (LCOS) as the system expansion time.This makes it possible to select the system expansion time that will minimize the life cycle cost (LCOS).

[0055] In other words, the system expansion timing calculation unit 105 calculates various coefficients k a , k b Among the combinations of SOHQ transition curves Q14 and Q16 corresponding to the load distribution candidates, that is, the curves Q14 and Q16 to be actually applied should be selected based on which the system capacity Qs is equal to or greater than the required value Qsmin at the time when the equalization condition is satisfied (for example, at time t15) and which have the smallest life cycle cost.The system expansion timing calculation unit 105 should then determine or propose the time when the equalization condition is satisfied based on the selected curves Q14 and Q16 (for example, at time t15) as the system expansion timing.

[0056] In the above example, one candidate system expansion time is selected from among candidates based on different load distributions. However, multiple candidates may be used as the system expansion time. For example, it is conceivable to apply curves Q14 and Q16 (see FIG. 6) to two of four different banks 10, and curves Q14A and Q16A (see FIG. 11) to the remaining two banks 10. In this case, for example, both time t15 in FIG. 6 and time t17 in FIG. 11 can be used as the system expansion time. In this way, by distributing the system expansion time over multiple times, the life cycle cost (LCOS) may be further reduced.

[0057] [Third Embodiment] Next, a battery system operation device according to a third embodiment will be described. The configuration of the battery system operation device according to the third embodiment is the same as that of the first and second embodiments (see FIG. 3) except for the following points. In this embodiment, a user inputs a maintenance schedule via a battery system information input unit 101. This maintenance schedule includes a maintenance possible period, which is a period during which maintenance work on the battery system BS is possible.

[0058] When expanding the battery system BS, it becomes necessary to connect a battery rack 14 whose SOHQ has decreased due to degradation to a bank 10 different from the previous bank 10. It is necessary to reserve time for work such as changing the installation location of the battery rack 14 and changing the settings of the connection cables. Because the battery system BS cannot be operated during these works, it becomes necessary to plan a maintenance schedule and reserve a period during which maintenance can be performed.

[0059] Therefore, the system expansion time calculation unit 105 of this embodiment determines or proposes, as the system expansion time, one of multiple system expansion time candidates that differ depending on the load distribution conditions (for example, time t15 in FIG. 6 and time t17 in FIG. 11) that falls within the maintenance possible period. Furthermore, if there are multiple candidates that fall within the maintenance possible period, the system expansion time calculation unit 105 calculates the life cycle cost (LCOS) of each, and determines or proposes, as the system expansion time, the one that minimizes the life cycle cost (LCOS).

[0060] Effects of the embodiment As described above, according to the embodiment, the battery system operation device 100 includes a battery degradation calculation unit 102 that calculates a first transition prediction (Q14) that is a transition prediction of the future degree of degradation of a first battery group (Ga) that is included in the battery system BS and has one or more secondary batteries, and a second transition prediction (Q16) that is a transition prediction of the future degree of degradation of a second battery group (Gb) that is included in the battery system BS and has a different degree of degradation from the first battery group (Ga); a battery degradation level comparison unit 103 that calculates, based on the first and second transition predictions (Q14, Q16), equalization condition fulfillment times (t15, t17, etc.), which are times when the first and second battery groups (Ga, Gb) will fulfill a predetermined equalization condition; and a system expansion timing calculation unit 105 that determines or proposes a system expansion timing, which is the time to add a secondary battery to the battery system BS, based on the equalization condition fulfillment times (t15, t17, etc.). This allows the system expansion timing to be determined or proposed based on the equalization condition fulfillment time (t15, t17, etc.), which is the time when the first and second battery groups (Ga, Gb) satisfy the specified equalization condition, so that an appropriate system expansion timing can be proposed for the secondary battery system.

[0061] Furthermore, the battery deterioration calculation unit 102 calculates first and second transition predictions (Q14, Q16) for each of multiple load distribution candidates, which are candidates for load distribution for the first and second battery groups (Ga, Gb), the battery deterioration level comparison unit 103 calculates an equality condition fulfillment time (t15, t17, etc.) for each of the load distribution candidates, and the system expansion timing calculation unit 105 further has a function of calculating a life cycle cost (LCOS) corresponding to each load distribution candidate and a function of selecting one of the load distribution candidates based on the life cycle cost (LCOS), and it is more preferable to determine or propose a system expansion time based on the equality condition fulfillment time (t15, t17, etc.) corresponding to the selected load distribution candidate. This makes it possible to select one of multiple equality condition fulfillment times (t15, t17, etc.) corresponding to the multiple load distribution candidates based on the life cycle cost (LCOS), thereby making it possible to determine or propose a more appropriate system expansion time.

[0062] Furthermore, it is more preferable that the battery system operation device 100 further includes a battery system information input unit 101 having a function of inputting a maintenance possible period, which is a period during which maintenance work on the battery system BS is possible, and the system expansion timing calculation unit 105 selects a load distribution candidate with the smallest life cycle cost (LCOS) from among the load distribution candidates whose corresponding equality condition fulfillment times (t15, t17, etc.) fall within the maintenance possible period, and determines or proposes the system expansion timing. This makes it possible to select a load distribution candidate with the smallest life cycle cost (LCOS) from among the load distribution candidates whose equality condition fulfillment times (t15, t17, etc.) fall within the maintenance possible period, thereby making it possible to determine or propose a more appropriate system expansion timing.

[0063] Furthermore, it is more preferable that the battery deterioration calculation unit 102 calculates the first and second transition predictions (Q14, Q16) using the past deterioration history of the first and second battery groups (Ga, Gb) and the past operation history. This makes it possible to obtain accurate first and second transition predictions (Q14, Q16), thereby making it possible to determine or propose a more appropriate system expansion timing.

[0064] Furthermore, it is more preferable that the system expansion timing calculation unit 105 determines or proposes the system expansion timing based on the times when the equalization condition is satisfied (t15, t17, etc.), on the condition that the deterioration levels of the first and second battery groups (Ga, Gb) at the times when the equalization condition is satisfied (t15, t17, etc.) both satisfy a predetermined condition (SOHQ≧Qmin). This allows the system expansion timing to be determined or proposed within a range in which the first and second battery groups (Ga, Gb) function appropriately, thereby making it possible to determine or propose a more appropriate system expansion timing.

[0065] Furthermore, it is more preferable that the system expansion timing calculation unit 105 further has a function of displaying the first and second transition predictions (Q14, Q16) and the system expansion timing on the screen of the display device 203. This allows the user to recognize the first and second transition predictions (Q14, Q16) and the system expansion timing via the display device 203.

[0066] [Modifications] The present invention is not limited to the above-described embodiment, and various modifications are possible. The above-described embodiment is provided as an example to facilitate understanding of the present invention, and is not necessarily limited to an embodiment including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to delete part of the configuration of each embodiment, or to add or replace other configurations. Furthermore, the control lines and information lines shown in the figures are those considered necessary for explanation, and do not necessarily represent all control lines and information lines necessary for the product. In reality, it is possible to consider that almost all components are interconnected. Possible modifications of the above-described embodiment include, for example, the following.

[0067] (1) Since the hardware of the battery system operation device 100 in each of the above embodiments can be realized by a general computer, programs for executing the various processes described above may be stored in a storage medium (a computer-readable storage medium on which a program is recorded) or distributed via a transmission path.

[0068] (2) In the above embodiment, the various processes described above are described as software processes using programs. However, some or all of the processes may be replaced with hardware processes using an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), etc.

[0069] (3) The various processes executed in the above embodiment may be executed by a server computer via a network (not shown), and the various data stored in the above embodiment may also be stored in the server computer.

[0070] REFERENCE SIGNS LIST 100 Battery system operation device (computer) 101 Battery system information input unit 102 Battery deterioration calculation unit (battery deterioration calculation process, battery deterioration calculation means) 103 Battery deterioration level comparison unit (battery deterioration level comparison process, battery deterioration level comparison means) 105 System expansion timing calculation unit (system expansion timing calculation process, system expansion timing calculation means) 203 Display device BS Battery system Ga Battery rack group (first battery group) Gb Battery rack group (second battery group) Q14 SOHQ transition curve (first transition prediction) Q16 SOHQ transition curve (second transition prediction) t15 Time (time when equality conditions are met) t17 Time (time when equality conditions are met) LCOS Life cycle cost

Claims

1. A battery system operation device comprising: a battery deterioration calculation unit that calculates a first transition prediction that is a transition prediction of a future deterioration level of a first battery group included in a battery system and having one or more secondary batteries, and a second transition prediction that is a transition prediction of a future deterioration level of a second battery group included in the battery system and having a different deterioration level from that of the first battery group; a battery deterioration level comparison unit that calculates an equalization condition fulfillment time, which is the time when the first and second battery groups will satisfy a specified equalization condition, based on the first and second transition predictions; and a system expansion timing calculation unit that determines or proposes a system expansion time, which is the time to add a secondary battery to the battery system, based on the equalization condition fulfillment time.

2. The battery system operation device described in claim 1, characterized in that the battery deterioration calculation unit calculates the first and second trend predictions for each of load distribution candidates, which are multiple candidates for load distribution to the first and second battery groups, the battery deterioration degree comparison unit calculates the time when the equality condition will be satisfied for each of the load distribution candidates, and the system expansion timing calculation unit further has a function of calculating a life cycle cost corresponding to each of the load distribution candidates and a function of selecting one of the load distribution candidates based on the life cycle cost, and determines or proposes the system expansion timing based on the time when the equality condition will be satisfied corresponding to the selected load distribution candidate.

3. The battery system operation device of claim 2, further comprising a battery system information input unit having a function of inputting a maintenance possible period, which is a period during which maintenance work on the battery system is possible, and the system expansion timing calculation unit selects the load distribution candidate with the smallest life cycle cost from among the load distribution candidates whose corresponding equality condition satisfaction period is included in the maintenance possible period, and determines or proposes the system expansion timing.

4. A battery system operation device as described in any one of claims 1 to 3, characterized in that the battery deterioration calculation unit calculates the first and second trend predictions using past deterioration history and past operation history of the first and second battery groups.

5. The battery system operation device described in claim 4, characterized in that the system expansion timing calculation unit determines or proposes the system expansion timing based on the time when the equalization condition is satisfied, on the condition that the deterioration levels of the first and second battery groups at the time when the equalization condition is satisfied both satisfy a specified condition.

6. A battery system operation device as described in claim 5, characterized in that the system expansion timing calculation unit further has a function of displaying the first and second trend predictions and the system expansion timing on a screen of a display device.

7. A battery system operation method comprising: causing a computer to execute a battery deterioration calculation process for calculating a first transition prediction which is a transition prediction of a future deterioration level of a first battery group included in a battery system and having one or more secondary batteries; and a second transition prediction which is a transition prediction of a future deterioration level of a second battery group included in the battery system and having a different deterioration level from that of the first battery group; a battery deterioration level comparison process for calculating an equalization condition fulfillment time, which is the time when the first and second battery groups will fulfill a predetermined equalization condition, based on the first and second transition predictions; and a system expansion timing calculation process for determining or proposing a system expansion time, which is the time to add a secondary battery to the battery system, based on the equalization condition fulfillment time.

8. A program for causing a computer to function as: a battery deterioration calculation means for calculating a first transition prediction which is a transition prediction of a future deterioration level of a first battery group included in a battery system and having one or more secondary batteries, and a second transition prediction which is a transition prediction of a future deterioration level of a second battery group included in the battery system and having a different deterioration level from that of the first battery group; a battery deterioration level comparison means for calculating an equality condition fulfillment time, which is the time when the first and second battery groups will satisfy a specified equality condition, based on the first and second transition predictions; and a system expansion timing calculation means for determining or proposing a system expansion timing, which is the time to add a secondary battery to the battery system, based on the equality condition fulfillment time.

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