Power system and control system

Abstract

To effectively utilize generated power of a power generation facility in a power system for supplying power to a synthesis point by utilizing the power generation facility and a power storage facility.SOLUTION: The power system 100 includes a plurality of power storage units 21 and a control system 30. Each of the plurality of power storage units 21 includes a power storage device exhibiting deterioration characteristics in which a deterioration speed during operation at a low C rate lower than the reference C rate and a deterioration speed during operation at a high C rate higher than the reference C rate are higher than a deterioration speed during operation at the reference C rate. The control system 30 includes a command acquisition unit that acquires a power command value, and a command distribution unit that distributes the power command value to an individual command value for one or more energy storage units among the plurality of energy storage units by using the deterioration characteristics.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a technique for controlling a power storage device. [Background technology]

[0002] For example, technologies have been proposed for controlling a plurality of power storage devices in accordance with a command value for power to be exchanged with a power grid. For example, Patent Document 1 discloses a configuration in which a priority order is set for each of a plurality of batteries based on the degradation characteristics of each battery's SOC (State Of Charge), and a command power is allocated to each battery according to the priority order. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6157880 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is practically difficult to achieve both suppression of deterioration of each battery and efficient operation of multiple batteries at a high level simply by setting the priority order of each battery based on the deterioration characteristics related to SOC as in Patent Document 1. In consideration of the above circumstances, one aspect of the present disclosure aims to achieve both suppression of deterioration of multiple power storage devices and efficient operation at a high level. [Means for solving the problem]

[0005] In order to solve the above problems, a power system according to one embodiment of the present disclosure is a power system including a plurality of energy storage units and a control system, wherein each of the plurality of energy storage units includes an energy storage device that exhibits deterioration characteristics in which the deterioration rate when operated at a low C rate below a standard C rate is greater than the deterioration rate when operated at a high C rate above the standard C rate, and the control system includes a command acquisition unit that acquires a power command value, and a command distribution unit that utilizes the deterioration characteristics to distribute the power command value to individual command values ​​for one or more energy storage units among the plurality of energy storage units.

[0006] A control system according to one embodiment of the present disclosure is a control system for controlling a plurality of energy storage units including an energy storage device that exhibits deterioration characteristics in which the deterioration rate when operating at a low C rate below a reference C rate exceeds the deterioration rate when operating at a high C rate above the reference C rate, and the control system includes a command acquisition unit that acquires a power command value, and a command distribution unit that utilizes the deterioration characteristic to distribute the power command value to individual command values ​​for one or more energy storage units among the plurality of energy storage units. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a block diagram illustrating a configuration of a power system according to a first embodiment. [Figure 2] FIG. 2 is a block diagram illustrating a configuration of a power storage unit. [Figure 3] 10 is a graph showing deterioration of electrical characteristics of a power storage device. [Figure 4] 1 is a graph showing the deterioration characteristics of a power storage device. [Figure 5] FIG. 1 is a block diagram illustrating a configuration of a control system. [Figure 6] FIG. 2 is a block diagram illustrating an example of the functional configuration of the control system. [Figure 7] 10 is a flowchart of a command distribution process. [Figure 8]3 is a schematic diagram showing changes over time in discharge capacity (remaining capacity) in a power storage device. FIG. [Figure 9] 10 is a flowchart of a process for calculating the number of operating vehicles in the second embodiment. [Figure 10] FIG. 11 is an explanatory diagram of the operation of a command distribution unit in the third embodiment. [Figure 11] 10 is a flowchart of a command allocation process in the third embodiment. [Figure 12] FIG. 10 is a block diagram illustrating a configuration of a power system according to a modified example. [Figure 13] FIG. 10 is a block diagram illustrating a configuration of a power system according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The following description of an embodiment of the present disclosure will be given with reference to the accompanying drawings. Note that the embodiment described below is an exemplary embodiment that may be envisioned when implementing the present disclosure. Therefore, the scope of the present disclosure is not limited to the embodiment exemplified below.

[0009] A: First embodiment 1 is a block diagram illustrating the configuration of a power system 100 according to a first embodiment of the present disclosure. The power system 100 is a system that exchanges electric power (AC power) with a power grid 10. The power grid 10 is, for example, a distribution system or a transmission system that supplies electric power generated by a power generation facility (not shown) such as a thermal power plant or a nuclear power plant to consumers such as business facilities or ordinary households.

[0010] 1, the power system 100 includes a power storage system 20 and a control system 30. The power storage system 20 is a power facility configured with a plurality (N) of power storage units 21 (N is a natural number equal to or greater than 2). The control system 30 is capable of communicating with each of the plurality of power storage units 21 via a communication network (not shown), such as a dedicated line.

[0011] Each of the N power storage units 21 is a power facility capable of charging and discharging power. Specifically, each power storage unit 21 is a system storage battery capable of discharging power to the power system 10 and charging power supplied from an external device such as the power system 10. The control system 30 is a computer system that controls the operation of each power storage unit 21. Specifically, the control system 30 instructs each power storage unit 21 as to the power that each power system 100 should charge or discharge.

[0012] FIG. 2 is a block diagram illustrating the configuration of each power storage unit 21. As illustrated in FIG. 2, each of the N power storage units 21 includes a power storage device 211 and a control device 212. The power storage device 211 is a storage battery capable of charging and discharging power. For example, the power storage device 211 is configured with a plurality of storage battery cells connected to each other in series or in parallel. Each storage battery cell is, for example, a lithium-ion battery in which the positive electrode active material is formed of a metal oxide containing lithium and the negative electrode active material is formed mainly of a carbon-based material.

[0013] The control device 212 is a PCS (Power Conditioning System) that controls charging and discharging of the power storage device 211. Specifically, the control device 212 controls charging and discharging of the power storage device 211 in accordance with a command value (an individual command value Pm, described later) supplied from the control system 30 to each power storage unit 21. The control device 212 also functions as a power conversion device that converts DC / AC power between the power storage device 211 and the power grid 10. That is, the control device 212 converts AC power supplied from the power grid 10 into DC power and outputs it to the power storage device 211, and converts DC power supplied from the power storage device 211 into AC power and outputs it to the power grid 1.

[0014] The electrical characteristics such as capacity of the power storage device 211 deteriorate over time due to continuous operation (charging or discharging) of the power storage device 211. Fig. 3 is a graph showing the deterioration of the electrical characteristics of the power storage device 211. Fig. 3 shows the change over time in the discharge capacity of the power storage device 211, with the horizontal axis representing the number of charge / discharge cycles of the power storage device 211. The discharge capacity shown on the vertical axis is a normalized value with the initial discharge capacity set to 100%.

[0015] 3 also shows the change in discharge capacity over time for a plurality of cases where the C rate during operation of the power storage device 211 is different. Specifically, the discharge capacity is shown for a C rate of 0.1 C (low C rate), a C rate of 0.3 C, and a C rate of 0.5 C (high C rate). The C rate is the rate of charge and discharge, and is expressed, for example, by a current value or a power value. Note that 0.5 C, which is exemplified as a high C rate in the first embodiment, is the rated C rate of the power storage device 211.

[0016] As can be seen from Figure 3, when the storage device 211 is operated at a low C rate (0.1C) or a high C rate (0.5C), there is a tendency for the deterioration of the storage device 211 over time to be accelerated compared to when it is operated at an intermediate C rate (0.3C).

[0017] 4 is a graph showing the relationship between the C rate and the degradation rate of the power storage device 211 (hereinafter referred to as "degradation characteristic D"). The horizontal axis represents the C rate in terms of the power value (individual command value Pm) instructed to the power storage device 211. The vertical axis represents the degradation rate, which is the rate at which the power storage device 211 deteriorates. Specifically, the rate at which the discharge capacity of the power storage device 211 decreases for each predetermined number of charge / discharge cycles is exemplified as the degradation rate.

[0018] 4 illustrates a power value corresponding to a specific C rate (hereinafter referred to as "reference C rate Popt"). The reference C rate Popt is, for example, 0.3C. In the following description, a specific C rate below the reference C rate Popt will be referred to as a "low C rate," and a specific C rate above the reference C rate Popt will be referred to as a "high C rate." The low C rate is, for example, 0.1C, and the high C rate is, for example, 0.5C.

[0019] The deterioration trend of the power storage device 211 described above with reference to Fig. 3 can also be confirmed from Fig. 4. Specifically, as can be seen from Fig. 4, the deterioration rate during operation at the low C rate exceeds the deterioration rate during operation at the reference C rate Popt. Similarly, the deterioration rate during operation at the high C rate exceeds the deterioration rate during operation at the reference C rate Popt.

[0020] As explained above, each power storage device 211 in the first embodiment exhibits deterioration characteristics D in which the deterioration rate during operation at a low C rate and the deterioration rate during operation at a high C rate exceed the deterioration rate during operation at the reference C rate Popt. In other words, the reference C rate Popt is a C rate at which the deterioration rate is minimal in the range between the low C rate and the high C rate under deterioration characteristics D.

[0021] Fig. 5 is a block diagram illustrating the configuration of the control system 30. As illustrated in Fig. 5, the control system 30 includes a control device 31, a storage device 32, and a communication device 33. The control system 30 may be realized by a single device, or may be realized by multiple devices configured separately from each other.

[0022] The control device 31 is composed of one or more processors that control each element of the control system 30. Specifically, the control device 31 is composed of one or more types of processors, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit).

[0023] The storage device 32 is one or more memories that store programs executed by the control device 31 and data used by the control device 31. The storage device 32 is configured with a known storage medium such as a magnetic storage medium or a semiconductor storage medium. The storage device 32 may be configured with a combination of multiple types of storage medium. A portable storage medium that can be attached to and detached from the control system 30 may be used as the storage device 32.

[0024] The communication device 33 communicates with an external device via wire or wirelessly. Specifically, the communication device 33 communicates with each power storage unit 21 (specifically, the control device 212). Furthermore, the communication device 33 of the first embodiment communicates with the management system 41 and the management system 42 of FIG. 1.

[0025] The management systems 41 and 42 are computer systems for managing electricity transactions with the power system 100. The management system 41 manages electricity transactions in the wholesale electricity market. On the other hand, the management system 42 manages electricity (adjustment capacity) transactions in the balancing market. As described above, the power system 100 of the first embodiment is capable of handling electricity transactions in a plurality of different electricity markets. The communication device 33 receives commands for electricity transactions in the wholesale electricity market from the management system 41, and receives commands for electricity transactions in the balancing market from the management system 42.

[0026] The wholesale electricity market managed by the management system 41 is an electricity market aimed at relatively long-term power operation, and therefore fluctuations in the electricity to be traded are long-term. On the other hand, the supply and demand adjustment market managed by the management system 42 is an electricity market aimed at adjustment capacity to respond to short-term or unexpected events, such as actual electricity demand, power generation from renewable energy sources, and unexpected power shortages due to power source failures, and therefore fluctuations in the electricity to be traded are shorter-term compared to the wholesale electricity market.

[0027] Generally, the power storage device 211 is ensured with a large capacity sufficient to appropriately accommodate long-cycle operations such as those in a wholesale electricity market. However, a power storage device 211 designed and installed under conditions suitable for long-cycle operations is not necessarily suitable for short-cycle operations such as those in a balancing market. For example, in a balancing market, power that is sufficiently lower than the rated power of the power storage device 211 may be required. As illustrated above, in the power system 100 that supports electricity transactions in multiple different electricity markets, it is expected that the power storage device 211 may be required to operate at a low C-rate. However, as described above, operation at a low C-rate may accelerate deterioration of the power storage device 211.

[0028] Taking the above circumstances into consideration, the control system 30 of the first embodiment controls each of the power storage devices 211 by utilizing the deterioration characteristic D of each of the power storage devices 211 so as to suppress deterioration of the power storage devices 211 caused by operation at a low C rate.

[0029] 6 is a block diagram illustrating an example of the functional configuration of the control system 30. The control device 31 executes a program stored in the storage device 32 to realize a plurality of functions (a command acquisition unit 51, a command distribution unit 52) ​​for controlling each of the power storage units 21.

[0030] The command acquisition unit 51 acquires a power command value P. The power command value P is the total value of power to be charged or discharged by the entire power storage system 20 (i.e., the N power storage units 21). Charging / discharging is distinguished by, for example, the sign of the power command value P.

[0031] Specifically, the command acquisition unit 51 sets the power command value P in accordance with the commands received by the communication device 33 from the management systems 41 and 42. That is, the power command value P is the total value of power that the power system 100 should trade in multiple power markets, such as the wholesale power market and the balancing market.

[0032] In the above description, the command acquisition unit 51 sets the power command value P in response to a command from an external device such as the management system 41 or the management system 42, but the command acquisition unit 51 may receive the power command value P set by the external device via the communication device 33. In other words, "acquisition" of the power command value P includes both reception and setting (e.g., generation or calculation) of the power command value P.

[0033] The command allocator 52 allocates the power command value P acquired by the command acquirer 51 to individual command values ​​Pm (m=1 to M) for each of M (0≦M≦N) power storage units 21 out of the N power storage units 21. The number M of the power storage units 21 is the total number of power storage units 21 that should actually be operated out of the N power storage units 21 (hereinafter referred to as the "number of operating units"). Specifically, the command allocator 52 determines the M power storage units 21 that should share the power command value P and the share of power by each power storage unit 21 (i.e., individual command value Pm). That is, the individual command value Pm corresponds to the portion of the power command value P allocated to one power storage unit 21. The command allocator 52 of the first embodiment sets the individual command value Pm for each power storage unit 21 according to the power command value P by using the deterioration characteristic D of each power storage unit 21.

[0034] 7 is a flowchart of a process (hereinafter referred to as "command allocation process") in which the control device 31 (command allocation unit 52) ​​sets the individual command value Pm. For example, the command allocation process is started in response to an interrupt signal generated at a predetermined period.

[0035] When the command allocation process is started, the control device 31 determines the priority of the N power storage units 21 (Sa1). The priority is the order in which the power storage units 21 should be preferentially selected as the operation target. The control device 31 determines the priority of each power storage unit 21, for example, so that the power storage unit 21 with less degradation in electrical characteristics is placed higher in the priority order. Specifically, the control device 31 determines the priority according to the amount of decrease in the actual capacity (discharge capacity) of each power storage unit 21 with respect to the rated capacity. For example, the control device 31 determines the priority of each power storage unit 21 so that the power storage unit 21 with a smaller amount of decrease in capacity is placed higher in the priority order. The capacity of each power storage unit 21 is, for example, measured periodically and stored in the storage device 32. Note that the control device 31 may set the priority of each power storage unit 21 randomly, for example, for each command allocation process.

[0036] The control device 31 calculates the number M of operating units according to the result (P / Popt) of dividing the power command value P by the reference C rate Popt in the deterioration characteristic D (Sa2). As described above, the number M of operating units is set to a positive number greater than or equal to 0 and less than or equal to N (0≦M≦N). Specifically, the control device 31 calculates the number M of operating units by rounding down the decimal part of the result (P / Popt) of dividing the power command value P by the reference C rate Popt, as expressed in the following mathematical formula (1).

number

[0037] The control device 31 determines whether the number of operating vehicles M exceeds the total number N of power storage units 21 (Sa3). If the number of operating vehicles M exceeds the total number N (Sa3: YES), the control device 31 sets the total number N of power storage units 21 as the number of operating vehicles M (Sa4). On the other hand, if the number of operating vehicles M is equal to or less than the total number N (Sa3: NO), the control device 31 maintains the value of the number of operating vehicles M.

[0038] The control device 31 divides the power command value P by the number of operating units M, as expressed by the following formula (2), to set an individual command value Pm (P1 to PM) for each of the energy storage units 21 (Sa5). The control device 31 transmits the individual command value Pm from the communication device 33 to each of the M energy storage units 21 in order of priority of the energy storage units 21 (Sa6).

number

[0039] As illustrated above, when the power command value P exceeds the product (hereinafter referred to as the "reference value") N·Popt of the total number N of power storage units 21 and the reference C-rate Popt, the power command value P is distributed evenly to all of the N power storage units 21. On the other hand, when the power command value P is below the reference value N·Popt, the reference C-rate Popt is distributed as individual command values ​​Pm to M power storage units 21, which are a portion of the N power storage units 21. That is, the M power storage units 21 are operated at the reference C-rate Popt with a small deterioration rate in the deterioration characteristic D. Therefore, according to the first embodiment, deterioration of the N power storage devices 211 can be effectively suppressed.

[0040] In the above explanation, the number M of operating units is calculated by rounding down the decimal part of the result (P / Popt) obtained by dividing the power command value P by the reference C-rate Popt, as in the above-mentioned formula (1a). However, the control device 31 may also calculate the number M of operating units by rounding up the decimal part of the result (P / Popt) obtained by dividing the power command value P by the reference C-rate Popt, as in the following formula (1b):

number

[0041] As described above, in the first embodiment, in the process of allocating the power command value P to the individual command values ​​Pm for the M energy storage units 21, the degradation characteristic D is used, in which the degradation rate during operation at the low C rate and the high C rate exceeds the degradation rate during operation at the reference C rate Popt. Therefore, the plurality of energy storage units 21 can be operated efficiently while suppressing degradation of the energy storage device 211 caused by operation (charging or discharging) at the low C rate. That is, according to the first embodiment, it is possible to achieve both suppression of degradation of each energy storage device and efficient operation at a high level.

[0042] Fig. 8 is a schematic diagram showing the change over time in discharge capacity (remaining capacity) of the power storage device 211. Fig. 8 shows the change over time in discharge capacity for both the first embodiment using the deterioration characteristic D and a mode (hereinafter referred to as "comparison") in which each power storage unit 21 is operated without using the deterioration characteristic D.

[0043] The operational capacity in Fig. 8 is a discharge capacity that needs to be secured over an operational period of, for example, about 20 years. As illustrated in Fig. 8, the discharge capacity of the power storage device 211 needs to be equal to or greater than the operational capacity at the end of the operational period.

[0044] In the first embodiment, the degradation of the power storage device 211 caused by operation at a low C rate can be suppressed by allocating the power command value P using the degradation characteristic D (specifically, the reference C rate Popt). As a result of suppressing the degradation of the power storage device 211, according to the first embodiment, as illustrated in Fig. 8, the initial discharge capacity that must be secured at the start of the operation period can be reduced compared to the comparative example. Therefore, according to the first embodiment, the initial cost of installing a plurality of power storage units 21 can be reduced compared to the comparative example.

[0045] B: Second embodiment A second embodiment of the present disclosure will be described. Note that, for elements in the following exemplary aspects that have the same functions as those in the first embodiment, the same reference numerals as those in the first embodiment will be used, and detailed descriptions of each will be omitted as appropriate.

[0046] The control device 31 (command distribution unit 52) ​​of the second embodiment selects as the number of operating units M either the number of operating units M calculated using the above-mentioned formula (1a) (hereinafter referred to as "number of operating units Ma") or the number of operating units M calculated using formula (1b) (hereinafter referred to as "number of operating units Mb").

[0047] 9 is a flowchart of the process (Sa2) of calculating the number of operating vehicles M in the command allocation process in the second embodiment. Other processes in the command allocation process are the same as those in the first embodiment.

[0048] The control device 31 calculates the number of operating units Ma using the above-mentioned formula (1a) (Sa21). The control device 31 calculates the total value Qa of the deterioration rates when the number of operating units Ma of the power storage units 21 are operated (Sa22). The total value Qa is expressed, for example, by the following formula (3a).

number

[0049] The function F() in the formula (3a) is a function (hereinafter referred to as "deterioration function") that represents the deterioration characteristic D of the power storage device 211. Specifically, the deterioration function F() is a function that expresses the deterioration rate using the C rate (power value) as a variable. Note that in the second embodiment, for the sake of convenience, it is assumed that the deterioration function F() is common to each power storage device 211.

[0050] The numerical value F(P / Ma) in formula (3a) means the deterioration rate of each power storage device 211 when the power command value P is evenly distributed to the Ma power storage devices 211. In other words, the total value Qa in formula (3a) is the numerical value obtained by adding up the deterioration rates F(P / Ma) of each power storage device 211 across the Ma power storage devices 211. As can be understood from the above explanation, the total value Qa is an index indicating the overall degree of deterioration expected for the entire power storage system 20 when the power command value P is evenly distributed to the Ma power storage devices 211.

[0051] Further, the control device 31 calculates the number of operating units Mb according to the aforementioned mathematical formula (1b) (Sa23). The control device 31 calculates the total value Qb of the deterioration rates when the power storage unit 21 of the number of operating units Mb is operated (Sa24). The total value Qb is expressed by, for example, the following mathematical formula (3b). [Number] Similar to the total value Qa, the total value Qb is a numerical value obtained by summing up the deterioration rates F(P / Mb) of each power storage device 211 when the power command value P is evenly distributed to Mb power storage devices 211. As understood from the above description, the total value Qb is an index indicating the overall degree of deterioration assumed for the entire power storage system 20 when the power command value P is evenly distributed to Mb power storage devices 211.

[0052] The control device 31 determines whether the total value Qa is less than the total value Qb (Sa25). When the total value Qa is less than the total value Qb (Qa < Qb), it means that the overall degree of deterioration assumed for the entire power storage system 20 is reduced when the power command value P is evenly distributed to Ma power storage devices 211 rather than when it is evenly distributed to Mb power storage devices 211. Therefore, when the total value Qa is less than the total value Qb (Sa25: YES), the control device 31 sets the number of operating units Ma calculated by the mathematical formula (1a) as the final number of operating units M (Sa26).

[0053] On the other hand, when the total value Qb is less than the total value Qa (Qb < Qa), it means that the overall degree of deterioration assumed for the entire power storage system 20 is reduced when the power command value P is evenly distributed to Mb power storage devices 211 rather than when it is evenly distributed to Ma power storage devices 211. Therefore, when the total value Qb is less than the total value Qa (Sa25: NO), the control device 31 sets the number of operating units Mb calculated by the mathematical formula (1b) as the final number of operating units M (Sa27).

[0054] The subsequent processes (Sa3 to Sa6) in the instruction allocation process are the same as those in the first embodiment. When the total value Qa and the total value Qb are equal (Qa = Qb), the control device 31 may select either the number of operating units Ma or the number of operating units Mb as the number of operating units M.

[0055] In the second embodiment, the same effects as those in the first embodiment are also achieved. Further, according to the second embodiment, compared with the form in which the number of operating units M is calculated by the mathematical formula (1a) or the form in which the number of operating units M is calculated by the mathematical formula (1b), the degree of overall degradation assumed for the entire power storage system 20 can be reduced.

[0056] C: Third Embodiment FIG. 10 is an explanatory diagram of the operation of the instruction distribution unit 52 in the third embodiment. The instruction distribution unit 52 in the third embodiment sets the individual command values Pm of each power storage unit 21 by using the threshold value PL and the threshold value PH in the degradation characteristic D of the power storage device 211. The threshold value PL is a predetermined value smaller than the reference C-rate Popt (PL < Popt). The threshold value PH is a predetermined value larger than the reference C-rate Popt (PH > Popt). The threshold value PL is an example of the "first threshold value", and the threshold value PH is an example of the "second threshold value".

[0057] FIG. 11 is a flowchart of the instruction distribution process in the third embodiment. When the instruction distribution process is started, the control device 31 determines the priority order for the N power storage units 21 in the same manner as in the first embodiment (Sb1). Further, the control device 31 initializes the number of operating units M to the total number N of the power storage units 21 (Sb2).

[0058] The control device 31 sets the individual command values Pm (P1 to PM) of each power storage unit 21 by dividing the power command value P by the number of operating units M as per the above-mentioned mathematical formula (2) (Sb3). Further, the control device 31 transmits the individual command value Pm from the communication device 33 to each of the M power storage units 21 in the order of the priority order of each power storage unit 21. As described above, the control device 31 (instruction distribution unit 52) in the third embodiment distributes the power command value P evenly to each power storage unit 21.

[0059] The control device 31 determines whether the current individual command value Pm of each power storage unit 21 is below the aforementioned threshold value PL for the deterioration characteristic D (Sb5). If the individual command value Pm is below the threshold value PL (Sb5: YES), the control device 31 reduces the number of operating units M to which the power command value P is allocated (Sb6). For example, the control device 31 reduces the number of operating units M by 1. On the other hand, if the individual command value Pm is above the threshold value PL (Sb5: NO), the control device 31 maintains the number of operating units M without reducing it. Note that if the individual command value Pm and the threshold value PL are equal, the control device 31 may or may not reduce the number of operating units M (Sb6).

[0060] Furthermore, the control device 31 determines whether the current individual command value Pm of each power storage unit 21 exceeds the aforementioned threshold value PH for the deterioration characteristic D (Sb7). If the individual command value Pm exceeds the threshold value PH (Sb7: YES), the control device 31 increases the number M of operating units to which the power command value P is allocated (Sb8). For example, the control device 31 increases the number M of operating units by 1. On the other hand, if the individual command value Pm is below the threshold value PH (Sb7: NO), the control device 31 maintains the number M of operating units without increasing it. Note that if the individual command value Pm and the threshold value PH are equal, the control device 31 may or may not increase the number M of operating units (Sb8). Furthermore, the order of decreasing the number M of operating units using the threshold value PL (Sb5, Sb6) and increasing the number M of operating units using the threshold value PH (Sb7, Sb8) may be reversed.

[0061] After executing the above process, the control device 31 proceeds to step Sb3. That is, the control device 31 sets an individual command value Pm for each energy storage unit 21 by dividing the power command value P by the number M of currently operating units (Sb3), and transmits the individual command value Pm to each energy storage unit 21 (Sb4). That is, the state in which the power command value P is evenly distributed to each energy storage unit 21 continues.

[0062] In the above configuration, when the number of operating units M decreases as a result of the individual command value Pm falling below the threshold value PL (Sb5, Sb6), the individual command value Pm is increased in the immediately following step Sb3. That is, in the third embodiment, the individual command value Pm is adjusted to a value exceeding the threshold value PL while maintaining a state in which the power command value P is evenly distributed to the energy storage units 21 of the number M of operating units. That is, the possibility that each energy storage unit 21 will be operated at a low C rate below the threshold value PL is reduced.

[0063] On the other hand, when the number M of operating units increases as a result of the individual command value Pm exceeding the threshold value PH (Sb7, Sb8), the individual command value Pm is decreased in the immediately following step Sb3. That is, in the third embodiment, the individual command value Pm is adjusted to a value below the threshold value PH while maintaining a state in which the power command value P is evenly distributed to the M number of operating energy storage units 21. That is, the possibility that each energy storage unit 21 will be operated at a high C rate that exceeds the threshold value PH is reduced.

[0064] As described above, in the third embodiment, the deterioration characteristic D (threshold value PL and threshold value PH) is used to allocate the power command value P to each energy storage unit 21. Therefore, similar to the first embodiment, it is possible to efficiently operate the plurality of energy storage units 21 while suppressing deterioration of the energy storage device 211 caused by operation at a low C rate.

[0065] Furthermore, in the third embodiment, when the individual command value Pm of each power storage unit 21 is below the threshold value PL, the number M of operating units decreases (Sb5, Sb6), and when the individual command value Pm of each power storage unit 21 is above the threshold value PH, the number M of operating units increases (Sb7, Sb8). That is, each power storage unit 21 operates at a C rate within the range between the threshold value PL and the threshold value PH in the deterioration characteristic D. Therefore, deterioration of the power storage device 211 in each power storage unit 21 can be effectively suppressed.

[0066] Note that the amount by which the number of operating units M is reduced when the individual command value Pm is lower than the threshold value PL is not limited to 1. The amount by which the number of operating units M is reduced may be a predetermined value of 2 or more, for example, or a variable value depending on the difference (PL-Pm) between the individual command value Pm and the threshold value PL. For example, the amount by which the number of operating units M is reduced may be set to a larger value as the difference between the individual command value Pm and the threshold value PL increases. Similarly, the amount by which the number of operating units M is increased when the individual command value Pm exceeds the threshold value PH is not limited to 1. The amount by which the number of operating units M is increased may be a predetermined value of 2 or more, for example, or a variable value depending on the difference (Pm-PH) between the individual command value Pm and the threshold value PH. For example, the amount by which the number of operating units M is increased may be set to a larger value as the difference between the individual command value Pm and the threshold value PH increases.

[0067] D: Fourth embodiment In the fourth embodiment, the operation (i.e., command distribution process) by the command distribution unit 52 to set the individual command value Pm for each power storage unit 21 is different from that of the first embodiment. The configuration and process other than the setting of the individual command value Pm are the same as those of the first embodiment.

[0068] The command distribution unit 52 of the fourth embodiment sets the individual command value Pm for each power storage unit 21 by using an objective function G expressed by the following equation (4).

number

[0069] Furthermore, the deterioration function Fn( ) in formula (4) is a function that represents the deterioration characteristic D of the power storage device 211 in the n-th power storage unit 21. That is, in the fourth embodiment, the deterioration characteristic D (deterioration function Fn( )) is set individually for each of the N power storage units 21. As described above, the deterioration characteristic D means the relationship between the C rate and the deterioration rate of the power storage device 211. Therefore, the function value Fn(Pn) in formula (4) means the deterioration rate of the power storage device 211 when the power storage unit 21 is operated with the individual command value Pn as the C rate. The symbol w in formula (4) is a weighting value, which is a coefficient for adjusting the importance of each of the first and second terms on the right-hand side. The weighting value w is set to, for example, a predetermined fixed value or a variable value according to an external instruction.

[0070] As can be understood from the above explanation, the first term Σ{Xn·Fn(Pn)} on the right side of Equation (4) means the total value of the deterioration rates Fn(Pn) across the N energy storage units 21. Specifically, the total value Σ{Xn·Fn(Pn)} is the total value of the deterioration rates Fn(Pn) of one or more energy storage units 21 that are to be operated (Xn=1) among the N energy storage units 21.

[0071] That is, the total value Σ{Xn·Fn(Pn)} is an index indicating the degree of overall deterioration expected for the entire power storage system 20 when each power storage device 211 is driven by each operation variable Xn and each individual command value Pn. Therefore, minimizing the objective function G (particularly the total value Σ{Xn·Fn(Pn)}) corresponds to suppressing the overall deterioration rate of the power storage system 20.

[0072] The symbol μ in Equation (4) denotes an average deterioration rate (hereinafter referred to as "deterioration average"). Specifically, the deterioration average μ is the average value of the deterioration rates Fn(Pn) in the N power storage devices 211. Therefore, the difference between the deterioration rate Fn(Pn) and the deterioration average μ {Fn(Pn)-μ} denotes the deviation of the deterioration rate Fn(Pn). Note that a preset fixed value may be applied as the deterioration average μ instead of a variable value calculated according to each deterioration rate Fn(Pn).

[0073] As can be understood from the above explanation, the second term Σ|Xn·Fn(Pn)-μ| on the right side of the formula (4) 2 means the degree of dispersion (specifically, variance) of the deterioration rates Fn(Pn) in the N power storage units 21. The degree of dispersion is an index (for example, variance) relating to the degree of variation in each deterioration rate Fn(Pn). Therefore, the objective function G (particularly the dispersion Σ|Xn·Fn(Pn)-μ| 2 ) corresponds to suppressing the variation in the deterioration rate among the N power storage units 21.

[0074] As described above, the objective function G is a function of the sum Σ{Xn·Fn(Pn)} of the deterioration rates Fn(Pn) across the N energy storage units 21 and the dispersion Σ|Xn·Fn(Pn)-μ| of the deterioration rates Fn(Pn) across the N energy storage units 21. 2 The command distribution unit 52 of the fourth embodiment determines the operation variable Xn and the individual command value Pn for each of the N power storage units 21 in the command distribution process so that the objective function G is minimized.

[0075] To minimize the objective function G, any known optimization algorithm suitable for optimization problems such as linear programming (LP), integer programming (IP), mixed-integer programming (MIP), or mixed-integer linear programming (MILP) is employed.

[0076] Specifically, the command distribution unit 52 minimizes the objective function G under the constraints expressed by the following formulas (5a) and (5b).

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[0077] The constraint condition of formula (5a) is a condition that the sum of the individual command values ​​Pn in the N energy storage units 21 matches the power command value P. Furthermore, the symbol Rn in formula (5b) is the rated output of the energy storage device 211 in the n-th energy storage unit 21. That is, the constraint condition of formula (5b) is a condition that the individual command value Pn is set with the rated output Rn as the upper limit value.

[0078] As described above, in the fourth embodiment, the degradation characteristic D (specifically, the degradation function Fn( )) is used to allocate the power command value P to each energy storage unit 21. Therefore, similar to the first embodiment, it is possible to efficiently operate the plurality of energy storage units 21 while suppressing degradation of the energy storage device 211 caused by operation at a low C rate.

[0079] In the fourth embodiment, the sum Σ{Xn·Fn(Pn)} of the deterioration rates Fn(Pn) of the power storage units 21 and the dispersion Σ|Xn·Fn(Pn)-μ| of the deterioration rates Fn(Pn) of the multiple power storage units 21 are calculated. 2 The operation variable Xn and the individual command value Pn of each power storage unit 21 are determined so as to minimize an objective function G including the above. Therefore, each power storage unit 21 can be operated so that the deterioration rate of the entire power storage system 20 is suppressed and differences (variations) in the deterioration rate between the power storage units 21 are reduced.

[0080] Furthermore, in the fourth embodiment, the deterioration characteristic D (deterioration function Fn( )) used to allocate the power command value P to each power storage unit 21 is set individually for each power storage unit 21. Therefore, compared to a mode in which a common deterioration characteristic D is applied to a plurality of power storage units 21, even if the deterioration characteristics D of the power storage units 21 differ, it is possible to allocate the power command value P to each power storage system 20 while suppressing deterioration of the power storage device 211 caused by operation at a low C rate.

[0081] E: Modified Example Specific modified embodiments that can be added to each of the embodiments exemplified above are exemplified below. Two or more embodiments arbitrarily selected from the following examples may be combined as appropriate within the scope of not being mutually contradictory.

[0082] (1) In the fourth embodiment, as described above, the degradation characteristic D (degradation function Fn( )) is set individually for each energy storage unit 21. Similarly, in the first to third embodiments, the degradation characteristic D (degradation function Fn( )) may be set individually for each energy storage unit 21.

[0083] For example, in the first or second embodiment, when the deterioration characteristic D is set individually for each power storage unit 21, the standard C rate Popt is also set individually for each power storage unit 21. That is, the standard C rate applied to the calculation of the number of operating vehicles M (and further to the calculation of the individual command value Pm) may differ for each power storage unit 21.

[0084] In the third embodiment, when the deterioration characteristic D is set individually for each power storage unit 21, the threshold value PL and the threshold value PH are also set individually for each power storage unit 21. That is, one or both of the threshold value PL and the threshold value PH may differ for each power storage unit 21.

[0085] (2) The deterioration characteristic D (deterioration function Fn()) may change over time. Specifically, the control device 31 may change the deterioration function Fn() of each power storage device 211 in accordance with, for example, the total number Yn of cycles of the power storage device 211.

[0086] (3) In each of the above-described embodiments, the power storage device 211 of each power storage unit 21 is configured with a plurality of storage battery cells. The deterioration characteristic D of the power storage unit 21 may be set according to the deterioration characteristic of each of the plurality of storage battery cells. For example, the deterioration function F() of the power storage unit 21 is expressed by the following mathematical formula (6).

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[0087] The symbol Kn in formula (6) is the number of storage battery cells that constitute the power storage device 211 of the nth power storage unit 21. Therefore, the symbol Pn / Kn in formula (6) corresponds to the allocation amount per storage battery cell when the individual command value Pn of the power storage unit 21 is evenly allocated to the Kn storage battery cells. Note that the number Kn of storage battery cells may differ for each power storage unit 21.

[0088] Furthermore, the function f() in Equation (6) is a deterioration function that represents the deterioration characteristics of one storage battery cell. Therefore, the symbol f(Pn / Kn) in Equation (6) means the deterioration rate of one storage battery cell when operated with the power value Pn / Kn as the C rate. As can be seen from Equation (6), the deterioration rate Fn(Pn) of the power storage unit 21 corresponds to the sum of the deterioration rates f(Pn / Kn) of the Kn storage battery cells.

[0089] (4) As illustrated in FIG. 12 , the power system 100 may include a power generation facility 60. The power generation facility 60 is, for example, a distributed power source that generates power using renewable energy. For example, any type of power generation system that uses renewable energy may be used as the power generation facility 60, such as a solar power generation system that converts solar energy into electricity, a wind power generation system that converts wind energy into electricity, a geothermal power generation system that converts geothermal energy into electricity, a hydroelectric power generation system that converts hydroelectric energy into electricity, or a biomass power generation system that converts biomass energy into electricity. Note that while FIG. 12 illustrates a single power generation facility 60 for convenience, multiple power generation facilities 60 of the same or different types may be installed in the power system 100. Furthermore, although the power generation facility 60 has been described above as an element of the power system 100, the power generation facility 60 may also be understood as an element external to the power system 100.

[0090] The control system 30 (command acquisition unit 51) sets a power command value P for the power storage system 20 in accordance with commands from external devices such as the management systems 41 and 42 and the power generated by the power generation equipment 60. For example, the control system 30 sets the power command value P in accordance with the difference between a target value in accordance with a command from the management system 41 or 42 and the amount of power generated by the power generation equipment 60. Furthermore, the control system 30 (command acquisition unit 51) may set the power command value P so that a prediction error in the amount of power generated by the power generation equipment 60 is absorbed by the power storage system 20.

[0091] (5) In each of the above-described embodiments, a configuration has been exemplified in which the control device 212 of each power storage unit 21 converts DC / AC power. In the above configuration, AC power is exchanged between the power grid 10 and the power storage system 20 (each power storage unit 21). On the other hand, as illustrated in FIG. 13 , a power conversion device 24 may be installed between the power grid 10 and the power storage system 20.

[0092] 13 is a PCS that converts DC / AC power between the power grid 10 and the power storage system 20. That is, the power conversion device 24 converts AC power supplied from the power grid 10 into DC power and outputs it to each power storage unit 21, and converts DC power supplied from each power storage unit 21 into AC power and outputs it to the power grid 10.

[0093] 13 , the control device 212 of each power storage unit 21 is a DC / DC converter that converts DC power into DC power of another voltage value. That is, the control device 212 converts DC power supplied from the power conversion device 24 into DC power of another voltage value and outputs it to the power storage device 211, and converts DC power supplied from the power storage device 211 into DC power of another voltage value and outputs it to the power conversion device 24. As can be understood from the above explanation, each power storage unit 21 and the power conversion device 24 are connected by the DC bus 25.

[0094] (6) In the fourth embodiment, the objective function G expressed by the mathematical formula (4) was exemplified. However, the objective function G applied to the fourth embodiment is not limited to the above exemplification. For example, the second term Σ|Xn·Fn(Pn)-μ| on the right side of the mathematical formula (4) 2 may be omitted. That is, the control device 31 (command distribution unit 52) may minimize the total value of the degradation rates Fn(Pn) over the N power storage units 21 as the objective function G. Also, the first term Σ{Xn·Fn(Pn)} on the right side of the mathematical formula (4) may be omitted.

[0095] (7) In each of the above-described embodiments, as exemplified in FIGS. 4 and 10, a form in which the degradation rate monotonically decreases toward the reference C rate Popt within the range of a low C rate (Pm < Popt) was exemplified. However, the degradation characteristics D of the power storage device 211 are not limited to the above exemplification. For example, a form in which the degradation rate decreases to a value lower than the degradation rate corresponding to the reference C rate Popt at a C rate even lower than the ranges exemplified in FIGS. 4 and 10 is also assumed. As described above, the reference C rate Popt does not have to be the C rate at which the degradation rate is minimized in the degradation characteristics D. Also, the reference C rate Popt does not have to be the only extreme point in the degradation characteristics D.

[0096] (8) In each of the above-described embodiments, as shown in FIG. 4, 0.5C, which is the rated C rate of the power storage device 211, was exemplified as the high C rate. However, the high C rate is not limited to the above exemplification. For example, the high C rate may be a C rate higher than the rated C rate (0.5C).

[0097] (9) As described above, the functions of the control system 30 according to the above-described embodiment are realized through cooperation between one or more processors constituting the control device 31 and a program stored in the storage device 32. The programs exemplified above can be provided in a form stored on a computer-readable recording medium and installed on a computer. The recording medium is, for example, a non-transitory recording medium, such as an optical recording medium (optical disk) such as a CD-ROM, but also includes any known type of recording medium, such as a semiconductor recording medium or a magnetic recording medium. Note that a non-transitory recording medium includes any recording medium other than a transitory, propagating signal, and does not exclude volatile recording media. Furthermore, in a configuration in which a distribution device distributes a program via a communication network, the recording medium storing the program in the distribution device corresponds to the non-transitory recording medium described above.

[0098] (10) The term "nth" (n is a natural number) in this application is used only as a formal and convenient label to distinguish each element in the description and does not have any substantive meaning. Therefore, there is no room for restrictive interpretation of the position or order of each element based on the term "nth."

[0099] F: Notes From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0100] A power system according to one aspect (aspect 1) of the present disclosure is a power system including a plurality of energy storage units and a control system, wherein each of the plurality of energy storage units includes an energy storage device exhibiting degradation characteristics in which the degradation rate during operation at a low C rate below a reference C rate is greater than the degradation rate during operation at a high C rate above the reference C rate, and the control system includes a command acquisition unit that acquires a power command value and a command allocation unit that utilizes the degradation characteristics to allocate the power command value to individual command values ​​for one or more of the plurality of energy storage units. In the above aspect, the process of allocating the power command values ​​to the individual command values ​​for the one or more energy storage units utilizes the degradation characteristics in which the degradation rate during operation at the low C rate and the high C rate is greater than the degradation rate during operation at the reference C rate. Therefore, the plurality of energy storage units can be operated efficiently while suppressing degradation of the energy storage device due to operation (charging or discharging) at the low C rate.

[0101] In a specific example (Aspect 2) of Aspect 1, the standard C-rate is a C-rate at which the deterioration rate is minimized under the deterioration characteristics, and the command distribution unit sets the individual command value by dividing the power command value by the number of operating power storage units for the number of operating power storage units corresponding to a result of dividing the power command value by the standard C-rate among the plurality of power storage units. In the above aspect, when the power command value exceeds a product (hereinafter referred to as a "standard value") of the total number of power storage units and the standard C-rate, the power command value is uniformly distributed to all of the plurality of power storage units. On the other hand, when the power command value is below the standard value, the standard C-rate is distributed as an individual command value to some of the plurality of power storage units. In other words, the number of operating power storage units is operated at the standard C-rate at which the deterioration rate is small. Therefore, deterioration of the power storage device in each power storage unit can be effectively suppressed. Note that the relationship between the result of dividing the power command value by the standard C-rate and the number of operating power storage units is arbitrary.

[0102] In a specific example (Aspect 3) of Aspect 1 or Aspect 2, the command distribution unit distributes the power command value equally to the power storage units, and when the individual command value of each power storage unit is below a first threshold value that is lower than the reference C-rate, reduces the number of operating power storage units to which the power command value is distributed, and when the individual command value of each power storage unit is above a second threshold value that is higher than the reference C-rate, increases the number of operating power storage units to which the power command value is distributed. In the above aspect, under the configuration in which the power command value is distributed equally to the power storage units, the number of operating units decreases when the individual command value of each power storage unit is below the first threshold value, and the number of operating units increases when the individual command value of each power storage unit is above the second threshold value. That is, each power storage unit operates at a C-rate that is within a range between the first threshold value and the second threshold value in the deterioration characteristic. Therefore, deterioration of the power storage device in each power storage unit can be effectively suppressed.

[0103] In a specific example (Aspect 4) of Aspect 1 or Aspect 2, the command distribution unit determines, for each of the plurality of power storage units, an operation variable indicating operation / stop of the power storage unit and an individual command value for the power storage unit, so as to minimize an objective function including a sum of the deterioration rates of the power storage units in the deterioration characteristics. In the above aspect, the operation variable and individual command value for each power storage unit are determined so as to minimize an objective function including a sum of the deterioration rates of the power storage units. Therefore, each power storage unit can be operated so as to suppress the deterioration rate of the entire plurality of power storage units.

[0104] In a specific example (Aspect 5) of Aspect 4, the objective function further includes a dispersion of the deterioration rates of the plurality of power storage units. According to the above aspect, the deterioration rate of the plurality of power storage units as a whole is suppressed, and each power storage unit can be operated so as to reduce differences (variations) in the deterioration rates of each power storage unit.

[0105] In a specific example (Aspect 6) of any of Aspects 1 to 5, the deterioration characteristic is set individually for each of the plurality of energy storage units. In the above aspects, the deterioration characteristic used for allocating power command values ​​to each energy storage unit is set individually for each energy storage unit. Therefore, compared to an embodiment in which a common deterioration characteristic is applied to a plurality of energy storage units, even if the deterioration characteristics of each energy storage unit differ, it is possible to allocate a power command value to each energy storage system while suppressing deterioration of the energy storage device caused by operation at a low C rate.

[0106] A control system according to one embodiment of the present disclosure is a control system for controlling a plurality of energy storage units including an energy storage device that exhibits deterioration characteristics in which the deterioration rate when operating at a low C rate below a reference C rate exceeds the deterioration rate when operating at a high C rate above the reference C rate, and the control system includes a command acquisition unit that acquires a power command value, and a command distribution unit that utilizes the deterioration characteristic to distribute the power command value to individual command values ​​for one or more energy storage units among the plurality of energy storage units. [Explanation of symbols]

[0107] 100...power system, 10...power system, 20...energy storage system, 21...energy storage unit, 211...energy storage device, 212...control device, 30...control system, 31...control device, 32...storage device, 33...communication device, 41, 42...management system, 51...command acquisition unit, 52...command distribution unit, 60...power generation equipment.

Claims

1. A power system including a plurality of power storage units and a control system, Each of the plurality of power storage units is a power storage device that exhibits a deterioration characteristic in which a deterioration rate during operation at a low C rate below a standard C rate and a deterioration rate during operation at a high C rate above the standard C rate are greater than a deterioration rate during operation at the standard C rate, The control system includes: a command acquisition unit that acquires a power command value; a command distribution unit that distributes the power command value to individual command values ​​for one or more of the plurality of power storage units by utilizing the deterioration characteristic. Power system.

2. the reference C rate is a C rate at which the deterioration rate becomes minimal under the deterioration characteristics, The command distribution unit sets the individual command value by dividing the power command value by the number of operating units for the power storage units of which the number corresponds to a result of dividing the power command value by the reference C rate among the plurality of power storage units. The power system of claim 1 .

3. The command distribution unit uniformly distributing the power command value to each of the power storage units; When the individual command value of each of the power storage units is below a first threshold value that is smaller than the reference C rate, reducing the number of operating power storage units that are targets for allocation of the power command value; When the individual command value of each of the power storage units exceeds a second threshold value that is greater than the reference C rate, the number of operating power storage units to which the power command value is allocated is increased. The power system of claim 1 .

4. The command distribution unit For each of the plurality of power storage units, an operation variable indicating operation / stop of the power storage unit and an individual command value for the power storage unit are determined so that an objective function including a total value of the deterioration rates of the power storage units in the deterioration characteristics is minimized. The power system of claim 1 .

5. The objective function further includes a degree of dispersion of deterioration rates of the plurality of power storage units. The power system of claim 4.

6. The deterioration characteristic is set individually for each of the plurality of power storage units. The power system according to any one of claims 1 to 5.

7. A control system for controlling a plurality of power storage units including a power storage device that exhibits a deterioration characteristic in which a deterioration rate during operation at a low C rate below a standard C rate and a deterioration rate during operation at a high C rate above the standard C rate are greater than a deterioration rate during operation at the standard C rate, a command acquisition unit that acquires a power command value; a command distribution unit that distributes the power command value to individual command values ​​for one or more of the plurality of power storage units by utilizing the deterioration characteristic; A control system comprising:

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