Battery Management System

Abstract

To provide a battery management system capable of appropriately responding to a demand response request.SOLUTION: A battery cellar 2 comprises: a storage unit 21 for storing a plurality of batteries; power conversion devices (AC / DC converter 22 and DC / DC converter 23) that are electrically connected between a power system 5 and the plurality of batteries stored in the storage unit 21; and a server 20 for controlling operation of the power conversion devices according to a demand response request from the power system 5 to charge / discharge the plurality of batteries. Of the plurality of batteries, the server 20 secures in the storage unit 21 batteries corresponding to capacity required for responding to the demand response request when full charge capacity of the plurality of batteries reduces as the plurality of batteries deteriorate, and permits delivery from the storage unit 21 with respect to batteries corresponding to surplus capacity over the required capacity.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a battery management system. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2018-205873 (Patent Document 1) describes encouraging users of electric vehicles that have storage batteries that are compatible with a power storage system to replace the storage batteries. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-205873 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the use of vehicles equipped with battery packs for driving has been rapidly increasing. As a result, the number of used batteries collected when these vehicles are replaced or dismantled is increasing. From the perspective of promoting the Sustainable Development Goals (SDGs), it is desirable to reuse used batteries by manufacturing new battery packs using collected used batteries. Collected used batteries are stored at logistics centers or the like while waiting to be reused. Properly storing used batteries is costly. In addition, it may take a certain amount of time (storage period) from the time collected used batteries are received until they are shipped out for reuse. Therefore, it is desirable to make effective use of the storage period of used batteries.

[0005] It is conceivable that the battery management system is provided with a storage facility for storing multiple batteries, as well as a power conversion device electrically connected between the multiple batteries stored in the storage facility and a power grid. A server of the battery management system charges and discharges the multiple batteries by controlling the operation of the power conversion device in response to a demand response request from the power grid. This allows the battery management system to receive payment from the manager of the power grid (typically a power company).

[0006] The present inventors have noticed that the following problem may arise when responding to a demand response request in this way. The multiple batteries stored in the storage facility gradually deteriorate while responding to a demand response request. As a result, the total capacity of the multiple batteries (composite capacity) decreases over time. As a result, even if the battery management system is initially able to respond to a demand response request, it may become unable to respond appropriately to the demand response request after a certain period of time has passed.

[0007] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a battery management system that can appropriately respond to a demand response request. [Means for solving the problem]

[0008] A battery management system according to an aspect of the present disclosure includes a storage facility for storing a plurality of batteries, a power conversion device electrically connected between the plurality of batteries stored in the storage facility and a power grid, and a server for charging and discharging the plurality of batteries by controlling the operation of the power conversion device in response to a demand response request from the power grid. The server secures in the storage facility batteries with a capacity necessary to respond to a demand response request when the full charge capacity of the plurality of batteries decreases due to deterioration of the plurality of batteries, and allows the shipment of batteries with a capacity exceeding the required capacity from the storage facility.

[0009] In the above configuration, the server takes into consideration a future decrease in full charge capacity and reserves batteries with the necessary capacity to respond to a demand response request from the power grid, and then permits shipment of only the remaining batteries (batteries with more capacity than required). In other words, the server sets a certain limit on the number of batteries that can be shipped so as not to be unable to respond appropriately to a demand response request. Therefore, with the above configuration, it is possible to respond appropriately to a demand response request. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a battery management system capable of appropriately responding to a demand response request. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram showing one aspect of logistics of a battery pack according to the present embodiment. [Diagram 2] FIG. 1 is a diagram showing an example of how used batteries are stored in a storage unit. [Diagram 3] 1 is a flowchart showing an overview of a process for reusing used batteries. [Figure 4] FIG. 2 is a system configuration diagram showing the electrical configuration of a battery cellar. [Diagram 5] FIG. 4 is a diagram illustrating an example of a data structure of battery data. [Figure 6] FIG. 1 is a conceptual diagram for explaining the change over time in capacity of a used battery stored in a battery cellar. [Figure 7] 5 is a flowchart showing an example of a processing procedure related to the sale of a used battery in the present embodiment. [Figure 8] FIG. 2 is a functional block diagram of a server related to deterioration evaluation of a used battery. [Figure 9] FIG. 2 is a functional block diagram of a server related to power adjustment between a battery cellar and a power grid. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In the present disclosure and the embodiments, charging and discharging a battery means at least one of charging and discharging a battery. In other words, charging and discharging a battery is not limited to both charging and discharging a battery, but may be only charging a battery or only discharging a battery.

[0013] In the present disclosure and embodiments, the battery pack includes a plurality of modules (also called blocks or stacks). The plurality of modules may be connected in series or in parallel with each other. Each of the plurality of modules includes a plurality of cells (single cells).

[0014] Generally, the "reuse" of assembled batteries can be broadly divided into reuse, rebuilding, and material recycling. In the case of reuse, collected assembled batteries undergo the necessary shipping inspection and are shipped as-is as reused products. In the case of rebuilding, collected assembled batteries are first disassembled into modules. Then, from among the disassembled modules, usable modules (which may be usable after performance recovery) are combined to manufacture a new assembled battery. The newly manufactured assembled battery undergoes shipping inspection and is shipped as a rebuilt product. In contrast, in material recycling, recyclable materials (resources) are extracted from each cell. Collected assembled batteries are not used as other assembled batteries.

[0015] In the embodiment described below, a battery pack collected from a vehicle is once disassembled into modules. Various processes are then carried out on a module-by-module basis. In other words, in the following, a reusable used battery means a module that can be rebuilt. However, disassembly into modules is not essential. Depending on the configuration of the battery pack or the degree of deterioration of the battery pack, it may be possible to reuse the battery pack without disassembly into modules.

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference characters, and the description thereof will not be repeated.

[0017] [Embodiment Mode] <Battery logistics model> Fig. 1 is a diagram showing one aspect of logistics of a battery pack in this embodiment. Hereinafter, the aspect of logistics shown in Fig. 1 will be referred to as a "battery logistics model". The battery logistics model 100 includes a collector 1, a battery seller 2, a buyer 3, a recycling plant 4, a power grid 5, and a distributed energy resource (DER) 6.

[0018] The recovery company 1 recovers used battery packs (used batteries 9) from a plurality of vehicles. The recovery company 1 may be a vehicle sales store (dealer) or a vehicle dismantling company.

[0019] In the battery logistics model 100 according to this embodiment, inventory management and sales management using battery data (indicated as DATA in the figure) are introduced (see FIG. 5). The battery data is linked to each used battery 9. More specifically, identification information (battery ID) is assigned to each used battery 9. In addition, an evaluation result of the degradation state of each used battery 9 is recorded. Therefore, in the battery logistics model 100, the used battery 9 can be identified using the battery ID, and the degradation state of the used battery can be managed and the distribution route of the used battery can be tracked.

[0020] The battery cellar 2 is a facility for appropriately managing used batteries 9 collected by the collection company 1, like a wine cellar where wine bottles are stored under temperature and humidity control. In the example shown in FIG. 1, the battery cellar 2 is installed at a logistics base near a port. The battery cellar 2 includes a server 20 that manages data related to the used batteries 9, and multiple storage units 21. The battery cellar 2 corresponds to the "battery management system" according to the present disclosure. The storage units 21 correspond to the "storage facility" according to the present disclosure. The batteries stored in the battery cellar 2 are not limited to used batteries, and may include new batteries.

[0021] FIG. 2 is a diagram showing an example of how used batteries 9 are stored in a storage unit 21. As shown in FIG. 2, a plurality of storage units 21 are arranged inside the building of the battery cellar 2. Each of the plurality of storage units 21 is configured to store many used batteries 9. Although details will be described later, in this embodiment, the battery cellar 2 performs a deterioration evaluation test on each of the used batteries 9 stored in the storage unit 21. Then, based on the results of the deterioration evaluation test, the battery cellar 2 judges whether each used battery 9 is reusable or not reusable (whether it is suitable or not for reuse).

[0022] Returning to Fig. 1, buyers 3 sell used batteries 9 that have been determined to be reusable by the battery seller 2. Buyers 3 may include dealers 31 that sell used batteries 9 for use in vehicles, and users 32 that use the batteries as stationary batteries in factories, buildings, etc. Buyers 3 may also include dealers 33 that sell used batteries 9 as supplies (replacement parts for maintenance and repair).

[0023] The recycling factory 4 performs material recycling on the used batteries 9 that have been determined by the battery seller 2 to be non-reusable, in order to regenerate them as raw materials for other products.

[0024] When a used battery 9 is sold to a buyer 3, the used battery 9 and the battery data linked to the used battery are provided to the buyer 3. The same applies to the delivery of the used battery 9 to the recycling factory 4. The battery data may be provided free of charge. In other words, the cost of the battery data may be included in the purchase price of the used battery 9. Alternatively, the provision of the battery data may be for a fee. In other words, the operating company of the battery seller 2 may receive the purchase price for the battery data from the buyer 3 in addition to the purchase price for the used battery 9.

[0025] The power system 5 is a power network constructed by power plants, power transmission and distribution facilities, etc. In this embodiment, the power company serves as both the power generation business operator and the power transmission and distribution business operator. The power company corresponds to a general power transmission and distribution business operator and also corresponds to the manager of the power system 5, and maintains and manages the power system 5. The power system 5 is provided with a business operator server 50. The business operator server 50 belongs to the power company and manages the power supply and demand of the power system 5. The server 20 and the business operator server 50 are configured to be capable of two-way communication.

[0026] The DER 6 is a relatively small-scale power facility that is installed at the logistics base (or the surrounding area) where the battery cellar 2 is installed and is capable of receiving and sending power to and from the battery cellar 2. The DER 6 includes, for example, a power generation type DER and a power storage type DER.

[0027] The power generation type DER may include a variable natural power source and a generator. The variable natural power source is a power generation facility whose power output varies depending on weather conditions. Although a solar power generation facility (solar panels) is illustrated in FIG. 1, the variable natural power source may include a wind power generation facility instead of or in addition to the solar power generation facility. On the other hand, the generator is a power generation facility that is not dependent on weather conditions. The generator may include a steam turbine generator, a gas turbine generator, a diesel engine generator, a gas engine generator, a biomass generator, a stationary fuel cell, and the like. The generator may include a cogeneration system that utilizes heat generated during power generation.

[0028] The energy storage type DER may include a power storage system and a heat storage system. The power storage system is a stationary energy storage device that stores electricity generated by natural variable power sources. The power storage system may be a power-to-gas device that uses electricity to produce gaseous fuels (hydrogen, methane, etc.). The heat storage system includes a heat storage tank installed between the heat source and the load, and is configured to temporarily store the liquid medium in the heat storage tank in a warm state. By using the heat storage system, the generation and consumption of heat can be shifted in time. Therefore, for example, it is possible to store the heat generated by consuming electricity to operate a heat source machine at night in the heat storage tank, and consume the heat during the day for air conditioning.

[0029] In this way, the used batteries 9 collected by the collector 1 are stored in the battery cellar 2 while waiting to be shipped to the buyer 3 or recycling factory 4. However, proper storage of the used batteries 9 using the battery cellar 2 requires maintenance costs (running costs). Furthermore, it may take a certain amount of time from when the collected used batteries 9 are received until they are shipped to the buyer 3 or recycling factory 4. Therefore, it is desirable to make effective use of the storage period of the used batteries 9 in the battery cellar 2.

[0030] In this embodiment, the battery cellar 2 functions as a virtual power plant (VPP) in addition to being a storage location for used batteries 9. This allows the opportunity for charging and discharging the used batteries 9 to serve both as a degradation evaluation of the used batteries 9 to determine the reuse mode of the used batteries 9 and as an adjustment of the power supply and demand balance of the power system 5 using the used batteries 9. As a result, in the battery cellar 2, the storage of the used batteries 9, the degradation evaluation of the used batteries 9, and the adjustment of the power supply and demand balance using the used batteries 9 are performed in a "trinity."

[0031] <Recycling process for used batteries> 3 is a flow chart showing an outline of the work process for reusing used batteries 9. First, used batteries 9 collected by a collection company 1 are delivered to a battery seller 2 (S1).

[0032] In this embodiment, the server 20 performs a deterioration evaluation test (performance inspection) on each of the used batteries 9 while they are stored in the storage unit 21 (S2). The server 20 evaluates the degree of deterioration of each used battery 9 based on electrical characteristics such as full charge capacity and internal resistance (e.g., AC impedance). Then, the server 20 determines whether each used battery 9 is reusable or non-reusable according to the results of the deterioration evaluation test (S3).

[0033] In this embodiment, used batteries 9 are ranked according to the results of the degradation evaluation test (more specifically, the measurement results of the full charge capacity). For example, as shown in FIG. 2, used batteries 9 that can be rebuilt are ranked into four stages, S rank, A rank, B rank, and C rank, in descending order of full charge capacity. This makes it possible to set the buying and selling price of used batteries 9 in association with the rank, and to guarantee the quality of used batteries 9 according to the rank. Therefore, used batteries 9 that have passed through the battery seller 2 can be smoothly distributed in the market. Note that used batteries 9 whose full charge capacity is below a specified value are ranked lower than C rank (denoted as Re) and are sent for material recycling.

[0034] If it is determined that the used battery 9 can be reused (YES in S3), the work process proceeds to a performance recovery process (S4). In the performance recovery process, a process (performance recovery process) is carried out to recover the performance of the used battery 9. For example, the full charge capacity of the used battery 9 can be recovered by overcharging the used battery 9. However, the performance recovery process may be omitted. Also, while the performance recovery process may be carried out on used batteries 9 that have a large degree of degradation (largely degraded performance) as a result of the degradation evaluation test, the performance recovery process may not be carried out on used batteries 9 that have a small degree of degradation (not much performance degradation).

[0035] Next, a new assembled battery is manufactured (rebuilt) using the used batteries 9 whose performance has been restored by the performance recovery process (S5). The used batteries 9 used to rebuild the assembled battery are basically used batteries 9 whose performance has been restored by the performance recovery process, but may include used batteries 9 whose performance recovery process has been omitted, or may include new batteries (new modules). The assembled battery is then sold and shipped to the sales destination 3 (S6).

[0036] If it is determined as not reusable as a result of the degradation evaluation test (NO in S3), the used battery 9 is transported to a recycling factory 4 (S7). In the recycling factory 4, the used battery 9 is dismantled and recycled.

[0037] In this way, the used batteries 9 are stored in the battery cellar 2 until they are collected by the collector 1 and delivered to the buyer 3 or the recycle plant 4, and a deterioration evaluation test is performed during that time. When measuring electrical characteristics such as the full charge capacity of the used batteries 9 in the deterioration evaluation test, the used batteries 9 are charged and discharged. In this embodiment, the charging and discharging uses power exchanged between the battery cellar 2 (and DER 6) and the power grid 5. This allows the battery cellar 2 to function as a VPP (or one of the DERs) and contribute to load leveling of the power grid 5. More specifically, during a time period when there is a surplus of supply relative to demand in the power grid 5, the battery cellar 2 absorbs the power surplus by charging the surplus power to the used batteries 9. On the other hand, when there is a shortage of supply relative to demand in the power grid 5, the battery cellar 2 alleviates the power shortage by discharging the shortage of power from the used batteries 9.

[0038] However, the battery seller 2 does not have to be configured to contribute to both absorbing surplus power and alleviating power shortages in the power grid 5. The battery seller 2 may be configured to contribute to only one of absorbing surplus power and alleviating power shortages. For example, the battery seller 2 can charge the used batteries 9 with surplus power in the power grid 5, while discharging the used batteries 9 to destinations that do not include the power grid 5. The used batteries 9 may be discharged only to the DER 6, for example.

[0039] <Battery cellar system configuration> Fig. 4 is a system configuration diagram showing the electrical configuration of the battery cellar 2. The battery cellar 2 comprises, for example, a storage unit 21, an AC / DC converter 22, a DC / DC converter 23, and a server 20. Note that due to space limitations, only one storage unit 21 is shown in Fig. 4, but as shown in Fig. 2, a typical battery cellar 2 comprises multiple storage units 21.

[0040] The storage unit 21 stores a plurality of used batteries 9. In Fig. 4, the plurality of used batteries 9 are connected in parallel to each other, but this is merely an example, and the connection manner of the plurality of used batteries 9 is not particularly limited. The plurality of used batteries 9 may be connected in series, or may be a combination of series and parallel connections. The storage unit 21 includes a voltage sensor 211, a current sensor 212, and a relay 213.

[0041] The voltage sensor 211 detects the voltage VB of the used battery 9 and outputs the detected value to the server 20. The current sensor 212 detects the current IB charged to and discharged from the used battery and outputs the detected value to the server 20. If temperature is used to evaluate the deterioration of the used battery 9, the storage unit 21 may further include a temperature sensor (not shown). Each sensor may be a sensor attached to the used battery 9.

[0042] The relay 213 includes, for example, a first relay electrically connected to the positive electrode side of the used battery 9 and a second relay electrically connected to the negative electrode side of the used battery 9. The relay 213 is configured to be capable of switching between electrical connection and disconnection between the used battery 9 and the power grid 5. This allows any used battery 9 to be electrically disconnected even while other used batteries 9 are being charged or discharged, and the used battery 9 can be removed from the storage unit 21.

[0043] The AC / DC converter 22 is electrically connected between the power system 5 and the DC / DC converter 23. The AC / DC converter 22 is configured to be capable of performing bidirectional power conversion operations for charging and discharging the used batteries 9 stored in the storage unit in accordance with a control command (charge / discharge command) from the server 20. More specifically, the AC / DC converter 22 converts AC power supplied from the power system 5 into DC power for charging the used batteries 9. The AC / DC converter 22 also converts DC power discharged from the used batteries 9 into AC power for supplying to the power system 5.

[0044] The DC / DC converter 23 is electrically connected between the AC / DC converter 22 and the storage unit 21, and is also electrically connected between the DER 6 and the storage unit 21. Like the AC / DC converter 22, the DC / DC converter 23 is configured to be capable of performing bidirectional power conversion operations in accordance with a control command (charge / discharge command) from the server 20. The DC / DC converter 23 can charge the used battery 9 with DC power from the AC / DC converter 22 and / or the DER 6, and can discharge the DC power stored in the used battery 9 to the AC / DC converter 22 and / or the DER 6. The AC / DC converter 22 and the DC / DC converter 23 correspond to the "power conversion device" according to the present disclosure.

[0045] The server 20 includes a processor such as a CPU (Central Processing Unit), memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and input / output ports (none of which are shown) through which various signals are input and output. The server 20 executes various controls based on signals received from each sensor and programs and maps stored in the memory. The server 20 includes a battery data storage unit 201, a deterioration evaluation unit 202, a power adjustment unit 203, a timing adjustment unit 204, and a display unit 205.

[0046] The battery data storage unit 201 stores battery data used for managing the used batteries 9 in the battery seller 2. Information regarding the degradation state of the used batteries 9 is recorded in the battery data.

[0047] FIG. 5 is a diagram showing an example of the data structure of the battery data. The battery data is stored, for example, in a map format. The battery data includes, as parameters, for example, identification information (battery ID) for identifying the used battery 9, the model number of the used battery 9, the manufacturing date, the current SOC (State Of Charge), the full charge capacity, the internal resistance, the rank, the degradation evaluation date and time (the most recent date and time when the degradation evaluation test was performed), the selling price, and the storage location (such as the identification information of the storage unit in which the used battery 9 is stored). The battery data may also include an evaluation result of the degradation state (specifically, an index ΣD indicating the bias of the salt concentration distribution in the electrolyte of the used battery 9, etc.) in that various evaluation results regarding the degradation state of the used battery 9 are recorded in the battery data, which can be said to be a "medical record" of the used battery 9.

[0048] 4 again, the deterioration evaluation unit 202 performs a deterioration evaluation test on the used battery 9 based on the voltage VB and current IB detected by the voltage sensor 211 and the current sensor 212, respectively, during charging and discharging of the used battery 9. An example of this evaluation method will be described with reference to Fig. 7. The deterioration evaluation unit 202 ranks the used battery 9 based on the results of the deterioration evaluation test.

[0049] The power adjustment unit 203 adjusts power between the battery cellar 2 (and DER 6) and the power grid 5. More specifically, the server 20 selects, from among a plurality of used batteries 9, a used battery 9 to be charged or discharged in response to a demand response (DR) request from the business operator server 50 (see FIG. 1). The power adjustment unit 203 outputs commands to the relay 213, the AC / DC converter 22, and the DC / DC converter 23 so that the selected used battery 9 is charged or discharged. An example of this control method will be described with reference to FIG. 8.

[0050] The timing adjustment unit 204 adjusts the timing of the deterioration evaluation test of the used battery 9 by the deterioration evaluation unit 202 and the timing of the power adjustment between the battery cellar 2 and the power grid 5 by the power adjustment unit 203. More specifically, the timing adjustment unit 204 adjusts the timing so that the deterioration evaluation test of the used battery 9 is performed in accordance with the timing of DR of the battery cellar 2 in response to a DR request from the business operator server 50. Note that what is performed in accordance with the DR of the battery cellar 2 is not limited to the deterioration evaluation test of the used battery 9, and a performance recovery process (see S4 in FIG. 3) may be performed in addition to the deterioration evaluation test.

[0051] The display unit 205 displays battery data in response to operations by the manager of the battery cellar 2 (which may be a worker working in the battery cellar 2). The display unit 205 also displays the progress and results of the deterioration evaluation test performed by the deterioration evaluation unit 202. This allows the manager to understand the status of the deterioration evaluation test. Furthermore, the display unit 205 displays the status of the used batteries 9 selected by the power adjustment unit 203 and being charged / discharged. This allows the manager to understand the status of power adjustment between the battery cellar 2 and the power grid 5.

[0052] <Decreased battery cell capacity> The present inventors have noticed that when the battery seller 2 responds to a DR request as described above, the following problems may occur.

[0053] 6 is a conceptual diagram for explaining the change over time in capacity of the used batteries 9 stored in the battery cellar 2. The horizontal axis represents elapsed time. The vertical axis represents the total capacity of the used batteries 9 stored in the battery cellar 2 (composite capacity of the battery cellar 2).

[0054] First, a case will be described where the quantity of used batteries 9 stored in the battery cellar 2 remains unchanged. The used batteries 9 gradually deteriorate while responding to DR requests. Therefore, as shown by curve L1, the combined capacity of the battery cellar 2 may decrease over time. In addition, the used batteries 9 stored in the battery cellar 2 are sold in response to purchase requests from the sellers 3. When the used batteries 9 are sold, the quantity of used batteries 9 stored in the battery cellar 2 decreases, which may also decrease the combined capacity of the battery cellar 2. On the other hand, a minimum capacity of Cmin is required for the battery cellar 2 to respond appropriately to DR requests.

[0055] For example, when p used batteries 9 are sold (see curve L2), the combined capacity of battery seller 2 exceeds Cmin during the period from initial time ta to time tb, so battery seller 2 can respond to the DR request. However, after time tb, the combined capacity of battery seller 2 falls below Cmin, so there is a possibility that battery seller 2 will not be able to respond properly to the DR request.

[0056] Therefore, in this embodiment, the quantity of used batteries 9 sold by the battery seller 2 is limited to a range in which the combined capacity of the battery seller 2 remains above Cmin even after a certain period of time has passed. As shown by curve L3, when q used batteries 9, which is less than p, are sold, the combined capacity of the battery seller 2 always exceeds Cmin during the period from time ta to time tc. In this way, by preventing the combined capacity of the battery seller 2 from falling below Cmin for a certain period of time from the present even if the used batteries 9 deteriorate, it becomes possible for the battery seller 2 to respond to a DR request.

[0057] <Sales volume of used batteries> 7 is a flowchart showing an example of a processing procedure for selling used batteries in this embodiment. This flowchart is called from a main routine (not shown) and executed when a predetermined condition is met (for example, when an operation is performed by the manager of the battery seller 2). Each step is realized by software processing by the server 20, but may also be realized by hardware (electrical circuitry) arranged within the server 20. Hereinafter, steps are abbreviated as S.

[0058] In S11, the server 20 estimates the future capacity at the time of deterioration for each of the multiple used batteries 9 stored in the battery cellar 2 (storage unit 21) (see FIG. 6). The server 20 holds data on the past and / or current full charge capacity for each used battery 9. Therefore, the server 20 can estimate the full charge capacity that has decreased with deterioration by curve regression analysis (curve fitting) using the data and a known estimation equation for battery deterioration (for example, an estimation equation in the form of a×exp(-bt)).

[0059] In S12, the server 20 acquires a capacity Cmin required to respond to the DR request. The capacity (unit: kWh) required to respond to the DR request is determined according to a contract concluded between the operating company of the battery seller 2 and the power company that manages the power system 5. Therefore, the server 20 can read out the predetermined capacity Cmin from a memory (not shown).

[0060] In S13, the server 20 acquires sales plans for the used batteries 9 (sales plans, purchase requests from the sellers 3, etc.). Then, based on the estimated capacity of each used battery 9 calculated in S11, the server 20 calculates the capacity (combined capacity of the remaining used batteries 9) after the used batteries 9 stored in the battery seller 2 are sold according to the sales plan (S14).

[0061] In S15, the server 20 determines whether the combined capacity of the remaining used batteries 9 is equal to or greater than the required capacity Cmin. If the combined capacity of the remaining used batteries 9 is equal to or greater than the required capacity Cmin (YES in S15), the server 20 permits the sale of all used batteries 9 according to the sales schedule (S16). In contrast, if the combined capacity of the remaining used batteries 9 is less than the required capacity Cmin (NO in S15), the server 20 secures used batteries 9 equivalent to the required capacity Cmin, and then permits the sale of only the used batteries 9 that exceed the required capacity Cmin (so to speak, the surplus) (S17).

[0062] It should be noted that the higher the rank of used batteries 9 sold, the greater the decrease in the combined capacity of the battery seller 2. Therefore, it is desirable for the server 20 to determine the used batteries 9 that can be sold taking the rank into consideration. For example, the server 20 may calculate the maximum number of used batteries 9 that can be sold for each rank. Specifically, the server 20 may calculate in advance separately the number of used batteries 9 of rank S that can be sold, the number of used batteries 9 of rank A that can be sold, the number of used batteries 9 of rank B that can be sold, and the number of used batteries 9 of rank C that can be sold, and determine whether to permit or prohibit sales within the range of these numbers.

[0063] In addition, it is desirable that the server 20 sets the number of high-rank (S rank, A rank, etc.) second-hand batteries 9 available for sale to be small in anticipation of a future decrease in combined capacity, and secures as much of them as possible as inventory. Note that sales are one aspect of "shipment" according to the present disclosure.

[0064] <Deterioration evaluation> 8 is a functional block diagram of the server 20 (deterioration evaluation unit 202) related to the deterioration evaluation of a used battery 9. In the following, for simplicity of explanation, the description focuses on one used battery 9. However, in reality, when there are multiple used batteries 9 for which deterioration evaluation has not been performed, the same process may be executed simultaneously for those used batteries 9. The deterioration evaluation unit 202 includes a current integration unit 71, an OCV (Open Circuit Voltage) calculation unit 72, an SOC change amount calculation unit 73, a full charge capacity calculation unit 74, and a ranking unit 75.

[0065] The current integrator 71 calculates an integrated value (integrated current amount) ΔAh (unit: Ah) of the current charged and discharged to the used battery 9 from when the start condition of the current integration is satisfied until the end condition is satisfied, based on the current IB detected by the current sensor 212. In this embodiment, as described above, the used battery 9 is charged and discharged in response to a DR request from the business entity server 50, and the current flowing during the DR is integrated. More specifically, when an upward DR (a request for an increase in power demand) is performed, the used battery 9 is charged to increase the power demand of the battery cellar 2, and the charging current at that time is integrated. On the other hand, when a downward DR is performed, the used battery 9 is discharged to reduce the power demand of the battery cellar 2, and the discharging current at that time is integrated. The current integrator 71 outputs the calculated integrated current amount ΔAh to the full charge capacity calculator 74.

[0066] The OCV calculation unit 72 calculates the OCV of the used battery 9 at the start of current integration and the OCV of the used battery 9 at the end of current integration. The OCV can be calculated, for example, according to the following formula (1). OCV = VB - ΔVp - IB × R (1)

[0067] In formula (1), the internal resistance of the used battery 9 is written as R, and the polarization voltage is written as Vp. At the start of current integration (immediately before the start of charging and discharging), the current IB=0. If the used battery 9 is left without being charged or discharged before the start of current integration, the polarization voltage Vp can be approximated as 0. Therefore, the OCV at the start of current integration can be calculated based on the voltage VB detected by the voltage sensor 211. On the other hand, the internal resistance R can be determined from the relationship between the voltage VB and the current IB (Ohm's law). If the used battery 9 is charged or discharged at a constant current, the polarization voltage Vp can also be determined from the current IB detected by the current sensor 212 by measuring the relationship between the current and the polarization voltage Vp in advance. Therefore, the OCV of the used battery 9 at the end of current integration can also be calculated based on the voltage VB and the current IB. The OCV calculation unit 72 outputs the two calculated OCVs to the SOC change amount calculation unit 73.

[0068] The SOC change amount calculation unit 73 calculates the SOC change amount ΔSOC of the used battery 9 from the start of current integration to the end of current integration based on the two OCVs. The SOC change amount calculation unit 73 has in advance a characteristic curve (OCV-SOC curve) that indicates the SOC dependency of the OCV. Therefore, by referring to the OCV-SOC curve, the SOC change amount calculation unit 73 can read out the SOC corresponding to the OCV at the start of current integration and the SOC corresponding to the OCV at the end of current integration, and calculate the difference between these SOCs as ΔSOC. The SOC change amount calculation unit 73 outputs the calculated ΔSOC to the full charge capacity calculation unit 74.

[0069] The full charge capacity calculation unit 74 calculates the full charge capacity C of the used battery 9 based on ΔAh from the current integration unit 71 and ΔSOC from the SOC change amount calculation unit 73. In detail, the full charge capacity C of the used battery 9 can be calculated according to the following formula (2) in which the ratio of ΔAh to ΔSOC is equal to the ratio of the full charge capacity C to ΔSOC=100%. Since the full charge capacity C0 in the initial state is known from the specifications of the used battery 9, the full charge capacity calculation unit 74 may further calculate the capacity maintenance rate Q from the full charge capacity C (Q=C / C0). The full charge capacity calculation unit 74 outputs the calculated full charge capacity C to the ranking unit 75. C = ΔAh / ΔSOC × 100 (2)

[0070] The ranking unit 75 ranks the used batteries 9 according to the full charge capacity C. The ranking unit 75 can record the date and time of ranking in the battery data (see FIG. 5) as the degradation assessment date and time.

[0071] The rank of the used battery 9 is displayed on the display unit 205 together with the battery ID, storage location, etc. of the used battery 9. This allows a worker working in the battery cellar 2 to take out from the storage location a used battery 9 of a rank that meets the request of the buyer 3 when a request for purchase of a used battery 9 is received from the buyer 3. By taking out used batteries to be sold from the storage unit 21 as appropriate, it is possible to prevent the storage unit 21 from becoming full.

[0072] The above method of calculating the full charge capacity C is merely an example. Any method can be used to calculate the full charge capacity C, as long as it uses the voltage VB and current IB detected as the used battery 9 is charged and discharged. The ranking unit 75 may determine the rank of the used battery 9 based on other characteristics (such as the internal resistance of the used battery 9 and an index ΣD indicating the bias of the electrolyte concentration in a lithium-ion battery) instead of or in addition to the full charge capacity C. The ranking unit 75 may determine the rank of the used battery 9 according to the length of time the used battery 9 has been charged and discharged and / or the number of times the used battery 9 has been charged and discharged. The ranking unit 75 may determine the rank of the used battery 9 according to the elapsed time since the used battery 9 was manufactured, although the accuracy may be somewhat reduced. The ranking unit 75 may also determine the rank of the used battery 9 by combining the above elements (such as the full charge capacity C, the internal resistance R, the index ΣD, the charge and discharge time, the number of times the used battery 9 has been charged and discharged, and the elapsed time since the used battery 9 was manufactured).

[0073] <Power adjustment> 9 is a functional block diagram of the server 20 (power adjustment unit 203) related to power adjustment between the battery cellar 2 and the power grid 5. In this example, for ease of understanding, a situation will be described assuming that the DER 6 is a power generation type DER (particularly a naturally fluctuating power source such as a solar power generation facility). The power adjustment unit 203 includes an overall adjustment amount calculation unit 81, a DER adjustment amount calculation unit 82, a battery cellar adjustment amount calculation unit 83, a used battery selection unit 84, a conversion operation unit 85, and a command generation unit 86.

[0074] The total adjustment amount calculation unit 81 receives a DR request from the business operator server 50 and calculates the total amount of power that requires power adjustment during a predetermined period (e.g., 30 minutes) using the battery cell 2 and the DER 6. This amount of power is hereinafter referred to as the total adjustment amount, and is also written as kWh (total). The total adjustment amount calculation unit 81 outputs the calculated kWh (total) to the battery cell adjustment amount calculation unit 83.

[0075] The DER adjustment amount calculation unit 82 acquires the operating state of each DER 6 (more specifically, the expected amount of power generated by each DER 6 during a predetermined period) by communicating with that DER 6. Hereinafter, this amount of power will be referred to as the DER adjustment amount, and will also be written as kWh(DER). The DER adjustment amount calculation unit 82 outputs the acquired kWh(DER) to the battery cellar adjustment amount calculation unit 83.

[0076] The battery cell adjustment amount calculation unit 83 calculates the amount of power that requires power adjustment using the battery cell 2 based on the kWh(total) from the total adjustment amount calculation unit 81 and the kWh(DER) from the DER adjustment amount calculation unit 82. This amount of power is hereinafter referred to as the battery cell adjustment amount, and is also written as kWh(bat). The battery cell adjustment amount calculation unit 83 can calculate, for example, the difference between the above two amounts of power, ΔkWh=kWh(total)-kWh(DER), as the battery cell adjustment amount kWh(bat). The battery cell adjustment amount calculation unit 83 outputs the calculated kWh(bat) to the used battery selection unit 84.

[0077] The used battery selection unit 84 knows the amount of power that can be charged and discharged for each of the many used batteries 9 stored in the multiple storage units 21. The used battery selection unit 84 selects used batteries to be used for power adjustment from the many used batteries 9 based on kWh(bat) from the battery cellar adjustment amount calculation unit 83. If kWh(bat)>0, the power shortage in the power system 5 is made up for by discharging from the battery cellar 2. Therefore, the used battery selection unit 84 selects a quantity of used batteries 9 that can discharge an amount of power equal to or greater than kWh(bat). On the other hand, if kWh(bat)<0, the surplus power in the power system 5 is absorbed by charging to the battery cellar 2. Therefore, the used battery selection unit 84 selects a quantity of used batteries 9 that can charge an amount of power equal to or greater than kWh(bat) (absolute value).

[0078] The conversion calculation unit 85 calculates the power to be charged and discharged for each used battery 9 selected by the used battery selection unit 84. More specifically, the conversion calculation unit 85 converts the amount of power (unit: kWh) to be adjusted by each used battery 9 into power (unit: kW) using the remaining time of power adjustment. As an example, if the power adjustment amount allocated to a certain used battery 9 is 10 kWh and the remaining time of power adjustment is 15 minutes, it can be calculated as 10 kWh × (60 minutes / 15 minutes) = 40 kW. The conversion calculation unit 85 outputs the power to be charged and discharged for each used battery 9 to the command generation unit 86.

[0079] The command generating unit 86 generates charge / discharge commands to the AC / DC converter 22 and the DC / DC converter 23, and also generates an opening / closing command to the relay 213, based on the calculation result by the conversion calculation unit 85. More specifically, the command generating unit 86 also generates an opening / closing command such that the selected used batteries 9 are electrically connected to the DC / DC converter 23, while the unselected used batteries 9 are electrically disconnected from the DC / DC converter 23. The command generating unit 86 generates a charge / discharge command such that the total power allocated to the selected used batteries 9 is charged or discharged.

[0080] Note that the power adjustment method shown in FIG. 8 is also merely an example, and is described for the sake of clarity. In this example, it is assumed that the DER6 is a power generation type DER, particularly a naturally variable power source whose power generation amount cannot be controlled. Therefore, the battery cell adjustment amount calculation unit 83 calculates the battery cell adjustment amount kWh(bat) based on the difference kWh(total)-kWh(DER) obtained by subtracting the DER adjustment amount kWh(DER) from the total adjustment amount kWh(total). That is, in this example, after the DER adjustment amount kWh(DER) is determined, the final power adjustment is performed by the battery cell adjustment amount kWh(bat). However, for example, when the DER6 includes a storage type DER, the battery cell adjustment amount calculation unit 83 may distribute the total adjustment amount kWh(total) to the DER adjustment amount kWh(DER) and the battery cell adjustment amount kWh(bat), and perform power adjustment using both the DER adjustment amount kWh(DER) and the battery cell adjustment amount kWh(bat).

[0081] As described above, in this embodiment, the degree of deterioration of each used battery 9 is evaluated while it is stored in the storage unit 21. This allows the storage period of the used batteries 9 to be used effectively in terms of time. Furthermore, the charging and discharging of the used batteries 9 for evaluating the degree of deterioration of the used batteries 9 is basically performed in response to a DR request from the business entity server 50. Furthermore, when the number of used batteries 9 is large, a large amount of power is charged and discharged, and this large amount of power is exchanged between the battery cellar 2 and the power system 5 in response to the DR request from the business entity server 50. This allows the operating company of the battery cellar 2 to receive a compensation (incentive) from the power company, and the compensation can be used as the running cost of the battery cellar 2. Alternatively, the operating company of the battery cellar 2 can recover a part of the initial investment (initial cost) of the battery cellar 2. This allows the storage period of the used batteries 9 to be used effectively in terms of money.

[0082] Furthermore, in this embodiment, the server 20 secures used batteries 9 with a required capacity Cmin to respond to a DR request from the power grid 5, and then permits the sale of only the amount of used batteries 9 that exceeds Cmin. That is, the server 20 sets a certain limit on the number of used batteries 9 that can be sold to the seller 3 so as not to be unable to respond appropriately to a DR request. Therefore, according to this embodiment, the battery seller 2 can respond appropriately to a DR request.

[0083] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0084] 100 Battery logistics model, 1 Collection company, 2 Battery cellar, 3 Sales destination, 31-33 Retail store, 4 Recycling plant, 5 Power system, 50 Business server, 6 Distributed energy resource (DER), 9 Used battery, 20 Server, 201 Battery data storage unit, 202 Deterioration evaluation unit, 203 Power adjustment unit, 204 Timing adjustment unit, 205 Display unit, 21 Storage unit, 211 Voltage sensor, 212 Current sensor, 213 Relay, 22 AC / DC converter, 23 DC / DC converter, 71 Current integration unit, 72 OCV calculation unit, 73 SOC change amount calculation unit, 74 Full charge capacity calculation unit, 75 Ranking unit, 81 Overall adjustment amount calculation unit, 82 Adjustment amount calculation unit, 83 Battery cellar adjustment amount calculation unit, 84 Used battery selection unit, 85 Conversion calculation unit, 86 Command generation unit.

Claims

[Claim 1] A storage unit for storing a plurality of batteries; a power conversion device electrically connected between the plurality of batteries stored in the storage facility and a power system; a server that controls an operation of the power conversion device in response to a demand response request from the power grid to charge and discharge the plurality of batteries; The server secures in the storage facility batteries with a capacity necessary to respond to the demand response request when the full charge capacity of the plurality of batteries decreases due to deterioration of the plurality of batteries, while allowing batteries with a capacity exceeding the required capacity to be shipped from the storage facility.

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