Energy Storage System

Abstract

To provide a power storage system capable of fully charging a battery pack without using a battery for adjustment.SOLUTION: A power storage system that performs charging and discharging with an external system includes a power converter connected to the external system, a plurality of battery packs used for the charging and discharging and connected in parallel with each other to the power converter, and a control device that controls an operation of the power converter such that a sum of a power storage amount after charging of each of the battery packs becomes a predetermined amount when each of the battery packs is charged. When each of the battery packs is charged and there is a first battery pack in which a predetermined time has elapsed since the previous full charge of the plurality of the battery packs, the control device charges the first battery pack until the first battery pack is fully charged, and adjusts a power storage amount of a second battery pack other than the first battery pack among the plurality of the battery packs such that the sum of the power storage amount after charging of each of the battery packs becomes the predetermined amount.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to an electricity storage system. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2014-103804 (Patent Document 1) discloses a battery system in which multiple battery packs are connected in parallel. The battery system of Patent Document 1 includes a host control device that transmits an instruction to equalize the voltages of the multiple battery packs based on the voltages of the battery packs, and a battery management device that equalizes the voltages of the battery packs based on the instruction transmitted from the host control device. The battery management device has an adjustment battery pack that charges each cell of the battery pack. In the battery system, the adjustment battery pack is used to balance the multiple cells in the battery pack, and then balancing is performed among the multiple battery packs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-103804 A [Patent Document 2] JP 2013-169051 A [Patent Document 3] JP 2012-85487 A [Patent Document 4] JP 2011-188700 A [Patent Document 5] JP 2010-142040 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve the accuracy of estimating the state of charge (SOC) of a battery, it is necessary to fully charge the battery pack. However, in a power storage (battery) system in which a plurality of battery packs are connected in parallel, there are cases in which none of the battery packs are fully charged. In such a power storage system, it is desirable to fully charge the battery pack without using the adjustment battery pack shown in Patent Document 1, from the viewpoint of cost reduction, etc.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a power storage system that is capable of fully charging a battery pack without using an adjustment battery. [Means for solving the problem]

[0006] According to an aspect of the present disclosure, a power storage system performs charging and discharging between the power storage system and an external system. The power storage system includes a power conversion device connected to the external system, and the above-mentioned power conversion device connected in parallel to the power conversion device. charge / discharge The power converter includes a plurality of battery packs for use in a power supply system, and a control device that controls the operation of a power conversion device so that the total amount of stored power in each of the battery packs after charging becomes a predetermined amount when each of the battery packs is charged. When charging each of the battery packs, if there is a first battery pack among the plurality of battery packs for which a predetermined time has elapsed since it was last fully charged, the control device charges the first battery pack until it becomes fully charged, and adjusts the amount of stored power in a second battery pack other than the first battery pack among the plurality of battery packs so that the total amount of stored power in each of the battery packs after charging becomes a predetermined amount.

[0007] According to the above configuration, a first battery pack among a plurality of battery packs that charge and discharge with an external system can be fully charged by using the plurality of battery packs. Therefore, it is possible to fully charge the first battery pack among the battery packs without using an adjustment battery pack different from the plurality of battery packs that charge and discharge with the external system.

[0008] Preferably, before the power storage system is put into practical use, an error between an integrated value of a current when the battery pack is charged or discharged for a predetermined time and a theoretical value of a current flowing in a predetermined time is calculated for each battery pack. The length of the predetermined time is set for each battery pack before the power storage system is put into practical use based on the error. The greater the error, the shorter the length of the predetermined time is set.

[0009] When the above error is large, the accuracy of estimating the state of charge (charging rate) is low. By fully charging the first assembled battery early, the accuracy of estimating the state of charge of the first assembled battery can be improved. Therefore, as described above, the accuracy of estimating the state of charge of the first assembled battery can be improved quickly by setting the predetermined time for determining whether or not full charging is required to be performed shorter as the above error is large.

[0010] Preferably, each assembled battery includes a plurality of cells. Prior to practical operation of the power storage system, variation in the self-discharge amount of each cell is calculated for each assembled battery. The length of the predetermined time is set for each assembled battery prior to practical operation based on the magnitude of the variation. The greater the variation, the shorter the length of the predetermined time is set.

[0011] The greater the variation in the self-discharge amount, the earlier it is preferable to perform cell equalization control for each of the multiple cells in the first assembled battery. When the first assembled battery is fully charged, each cell in the first assembled battery is also fully charged, so that cell equalization can be performed in the first assembled battery. Therefore, as described above, the greater the variation in the self-discharge amount, the shorter the predetermined time for determining whether or not full charging is required is set, so that cell equalization can be performed more quickly in assembled batteries that require cell equalization.

[0012] Preferably, each assembled battery includes a plurality of cells. The power storage system further includes a plurality of voltage detection circuits provided in association with each of the plurality of cells, each detecting a voltage of the cell. Prior to actual operation of the power storage system, a variation in impedance of each voltage detection circuit is calculated for each assembled battery. The length of the predetermined time is set for each assembled battery prior to actual operation based on the magnitude of the variation. The greater the variation, the shorter the length of the predetermined time is set.

[0013] The greater the variation in impedance, the greater the variation in the self-discharge amount. As described above, the greater the variation in the self-discharge amount, the earlier it is preferable to perform cell equalization control for each of the multiple cells in the first assembled battery. When the first assembled battery is fully charged, each cell in the first assembled battery is also fully charged, so that cell equalization can be performed in the first assembled battery. Therefore, as described above, the greater the variation in impedance, the shorter the predetermined time for determining whether or not full charging is required, so that cell equalization can be performed more quickly in assembled batteries that require cell equalization.

[0014] Preferably, when the control device adjusts the storage capacity of the multiple second assembled batteries and the multiple second assembled batteries include ternary lithium-ion batteries and iron phosphate lithium-ion batteries, the control device controls the operation of the power conversion device so that the storage capacity of the ternary lithium-ion batteries is greater than the storage capacity of the iron phosphate lithium-ion batteries.

[0015] The internal resistance of an iron phosphate lithium-ion battery is higher than that of a ternary lithium-ion battery. Therefore, by making the charge amount of the ternary lithium-ion battery with the lower resistance greater than that of the iron phosphate lithium-ion battery during adjustment (preferentially charging the ternary lithium-ion battery), it is possible to reduce power consumption compared to when the charge amount of the iron phosphate lithium-ion battery is made greater than that of the ternary lithium-ion battery. Effect of the Invention

[0016] According to the above disclosure, it is possible to fully charge the assembled battery without using an adjustment battery.

Brief Description of the Drawings

[0017] [Figure 1] It is a diagram for explaining the configuration of the power storage system and the external system. [Diagram 2] It is a diagram for explaining a part of the circuit configuration of the assembled battery. [Diagram 3] It is a diagram for explaining the outline of the processing in the power storage system. [Figure 4] It is a flowchart for explaining the flow of processing when charging three assembled batteries.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same members are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0019] <A. Overall Configuration> FIG. 1 is a diagram for explaining the configuration of the power storage system and the external system. As shown in FIG. 1, the power storage system 1 is connected to the external system 900 by a power line. The power storage system 1 can supply power to the external system 900 and can discharge to the external system 900.

[0020] The power storage system 1 includes a plurality of battery units 10A, 10B,... and a host controller 20. Hereinafter, any one of the plurality of battery units 10A, 10B,... will also be referred to as "battery unit 10".

[0021] The battery unit 10A includes a PCU (Power Control Unit) 11, an assembled battery 12A, an assembled battery 12B, an assembled battery 12C, and an ECU (Electronic Control Unit) 13.

[0022] The PCU 11 is a power conversion device including an inverter, a DC / DC converter, etc. In the battery unit 10A, three assembled batteries 12A, 12B, and 12C are connected in parallel to the PCU 11. More specifically, the battery unit 10A has three terminals 111, 112, and 113 for external connection of the PCU 11. The assembled battery 12A is connected to the terminal 111 of the three terminals. The assembled battery 12B is connected to the terminal 112. The assembled battery 12C is connected to the terminal 113.

[0023] The assembled batteries 12A, 12B, and 12C are each a pack of a plurality of the same type of single batteries (also referred to as "battery cells"). The assembled batteries 12A, 12B, and 12C are also referred to as "battery packs." Each of the assembled batteries 12A, 12B, and 12C is, for example, a ternary lithium ion battery (hereinafter referred to as a "ternary battery") or an iron phosphate lithium ion battery (hereinafter referred to as an "LFP battery"). The internal resistance of an LPF battery is higher than that of a ternary battery. The internal resistance of an LPF battery becomes high especially in the low temperature range.

[0024] Like the battery unit 10A, the battery unit 10B includes a PCU 11, battery packs 12A, 12B, and 12C, and an ECU 13. Note that in the battery unit 10B, the type of battery pack connected to the PCU 11 may be different from that in the battery unit 10A. For example, the battery unit 10A may include two ternary batteries and one LFP battery as the battery packs 12A, 12B, and 12C, and the battery unit 10B may include one ternary battery and two LFP batteries as the battery packs 12A, 12B, and 12C. The combination of the battery packs included in each battery unit 10 is not particularly limited.

[0025] In the following description, any one of the multiple battery packs 12A, 12B, and 12C will also be referred to as "battery pack 12."

[0026] In this example, a PCU and an ECU that were installed in a vehicle are repurposed as the PCU 11 and the ECU 13, respectively. Similarly, assembled batteries that were installed in a vehicle are repurposed as the assembled batteries 12A, 12B, and 12C. In this manner, the energy storage system 1 is constructed using unnecessary vehicle parts. In detail, the three-phase AC motor connected to the PCU of the vehicle is removed, and three assembled batteries (one each for the U layer, V layer, and W layer) are connected. Note that terminals 111, 112, and 113 are terminals for the U layer, the V layer, and the W layer, respectively.

[0027] The external system 900 includes a PCS (Power Conditioning System) 910, a solar power generation device 920, a load 930, and a power system 940. The battery units 10 (more specifically, the PCUs 11) are connected to the PCS 910 in parallel with each other.

[0028] The PCS 910 is a power conversion device capable of both AC / DC conversion (conversion from alternating current to direct current) and DC / AC conversion (conversion from direct current to alternating current). The PCS 910 receives direct current power from, for example, a solar power generation device 920. The PCS 910 supplies alternating current power to a load 930. The load 930 includes electrical appliances used in the home (for example, air conditioners and lighting fixtures). The PCS 910 exchanges alternating current power with a power grid 940.

[0029] Each ECU 13 includes a processor and a memory (see FIG. 2), and controls the battery unit 10. Each ECU 13 is communicatively connected to the upper controller 20. When charging each of the assembled batteries 12A, 12B, 12C, each ECU 13 controls the operation of the PCU 11 so that the total amount of stored power in each of the assembled batteries 12A, 12B, 12C after charging becomes a predetermined amount Qs.

[0030] The upper controller 20 includes a processor and a memory (neither of which are shown), and sends commands to each ECU 13. The upper controller 20 is communicatively connected to a server (not shown) via a network NW.

[0031] In the power storage system 1, each battery unit 10 is charged by the external system 900 at least during the late-night time zone and discharges to the external system 900 at least during the daytime time zone. Specifically, in each battery unit 10, each of the three battery packs 12 is supplied with power from the external system 900 at least during the late-night time zone and discharges to the external system 900 at least during the daytime time zone.

[0032] <B. Configuration of Battery Pack> FIG. 2 is a diagram for explaining a part of the circuit configuration of the battery pack 12. As shown in FIG. 2, the battery pack 12 includes a plurality of units 120. Each unit 120 includes a cell 121, a voltage detection circuit 122, an ammeter 123, charge / discharge and a usage circuit 124. charge / discharge The usage circuit 124 has a switch 1241.

[0033] The ammeter 123 and the switch 1241 are connected in series to the cell 121. The voltage detection circuit 122 is connected in parallel to the cell 121.

[0034] The voltage detection circuit 122 detects the voltage of the cell 121. Specifically, the voltage detection circuit 122 has two connection terminals 1221 and 1222 for connecting to the positive electrode and the negative electrode of the cell 121, and a voltmeter 1223 provided between the connection terminal 1221 and the connection terminal 1222. The voltage detection circuit 122 detects the voltage between the two connection terminals 1221 and 1222 (i.e., the voltage between the positive electrode and the negative electrode of the cell 121) by the voltmeter 1223.

[0035] The ammeter 123 measures the current value of the current flowing out of the cell 121 when the current is discharged from the cell 121 and the current value of the current flowing into the cell 121 when the cell 121 is charged. That is, the ammeter 123 measures charge / discharge the current value of the current flowing into the usage circuit 124 when the cell 121 is charged or discharged. Further, the ammeter 123 also measures the self-discharge amount of the cell 121.

[0036] By turning on switch 1241, charging and discharging of cell 121 become possible. The on and off operations of switch 1241 are controlled by ECU 13.

[0037] The measured value (voltage value) by voltmeter 1223 and the measured value (current value) by ammeter 123 are sent to ECU 13. Note that ECU 13 includes processor 131 and memory 132.

[0038] <C. Outline of Processing> Figure 3 is a diagram for explaining the outline of the processing in power storage system 1. As shown in Figure 3, state (A) is a diagram for explaining the state immediately before starting the Nth charge. State (B) is a diagram for explaining the state immediately before starting the (N + 1)th charge. Note that N is a natural number.

[0039] (1) The Nth Charge In this example, immediately before starting the Nth charge, it is assumed that the elapsed time Ta_1 since the battery pack 12A of battery unit 10 became fully charged last time is less than the threshold Ta_th for battery pack 12A. Similarly, it is assumed that the elapsed time Tb_1 since the battery pack 12B became fully charged last time is less than the threshold Tb_th for battery pack 12B. Further, it is assumed that the elapsed time Tc_1 since the battery pack 12C became fully charged last time is less than the threshold Tc_th for battery pack 12C. Note that each threshold Ta_th, Tb_th, Tc_th is stored in advance in ECU 13.

[0040] As described above, when ECU 13 charges each battery pack 12A, 12B, 12C in battery unit 10, it controls the operation of PCU 11 so that the total amount of stored electricity after charging each battery pack 12A, 12B, 12C becomes a predetermined amount Qs.

[0041] The ECU 13 assigns a post-charging storage amount (target value) to each of the assembled batteries 12A, 12B, and 12C. In this example, the ECU 13 controls the operation of the PCU 11 so that the post-charging storage amount of the assembled battery 12A becomes Qa_1. Similarly, the ECU 13 controls the operation of the PCU 11 so that the post-charging storage amount of the assembled battery 12B becomes Qb_1. The ECU 13 controls the operation of the PCU 11 so that the post-charging storage amount of the assembled battery 12C becomes Qc_1.

[0042] Qa_1 is a value less than the fully charged capacity of the battery pack 12A. Qb_1 is a value less than the fully charged capacity of the battery pack 12B. Qc_1 is a value less than the fully charged capacity of the battery pack 12C. The sum of Qa_1, Qb_1, and Qc_1 is Qs.

[0043] For example, the ECU 13 may control Qa_1, Qb_1, and Qc_1 to be the same value. Also, Ta_th, Tb_th, and Tc_th may be set to the same value.

[0044] (2) N+1th charge Next, after the Nth charging is completed, as shown in state (B), it is assumed that the elapsed time Ta_2 since the battery pack 12A was previously fully charged is equal to or greater than the threshold value Ta_th for the battery pack 12A immediately before the (N+1)th charging is started. It is also assumed that the elapsed time Tb_2 since the battery pack 12B was previously fully charged is less than the threshold value Tb_th, and the elapsed time Tc_2 since the battery pack 12C was previously fully charged is less than the threshold value Tc_th.

[0045] In this case, the ECU 13 performs the following control: The ECU 13 controls the operation of the PCU 11 so that the amount of stored electricity after charging of the battery pack 12A becomes Qa_max. That is, the ECU 13 fully charges the battery pack 12A.

[0046] Furthermore, the ECU 13 controls the operation of the PCU 11 such that the amount of stored electricity after charging of the battery pack 12B becomes Qb_2. The ECU 13 controls the operation of the PCU 11 such that the amount of stored electricity after charging of the battery pack 12C becomes Qc_2. Qb_2 is a value less than the full charge capacity of the battery pack 12B. Qc_2 is a value less than the full charge capacity of the battery pack 12C.

[0047] Specifically, the ECU 13 determines the values of Qb_2 and Qc_2 such that the value obtained by adding Qb_2 and Qc_2 to Qa_max (i.e., the total capacity of the three battery packs 12A, 12B, and 12C) becomes Qs. For example, the ECU 13 sets the value (Qd / 2) obtained by dividing the difference value (Qd = Qs - Qa_max) obtained when Qa_max is subtracted from Qs by 2 as Qb_2 and Qc_2. However, such an allocation is just an example and is not limited thereto.

[0048] By such control of the ECU 13, it becomes possible to fully charge the battery pack 12A for which the elapsed time since the previous full charge is equal to or longer than the threshold Ta_th.

[0049] <D. Control Structure> FIG. 4 is a flowchart for explaining the flow of processing when charging the three battery packs 12A, 12B, and 12C. That is, hereinafter, the processing when the charging timing of the battery packs 12A, 12B, and 12C arrives will be described.

[0050] As shown in FIG. 4, in step S1, the ECU 13 determines whether there is a battery pack 12 (hereinafter also referred to as "battery pack α" for convenience of explanation) among the battery packs 12A, 12B, and 12C for which the time set for each battery pack since the previous full charge (specifically, the above-described thresholds Ta_th, Tb_th, and Tc_th) has elapsed.

[0051] If it is determined that the battery pack α is not present (NO in step S1), in step S6, the ECU 13 starts charging the battery packs 12A, 12B, and 12C. Specifically, as shown in state (A) in FIG. 4, the ECU 13 controls the operation of the PCU 11 so that the amounts of charge after charging of the battery packs 12A, 12B, and 12C become Qa_1, Qb_1, and Qc_1, respectively. After that, the ECU 13 advances the process to step S5. Note that in step S6, the ECU 13 may charge the three battery packs 12A, 12B, and 12C simultaneously or one at a time.

[0052] If it is determined that the battery pack α is present (YES in step S1), in step S2, the ECU 13 starts charging the battery pack α. In step S3, the ECU 13 determines whether the battery pack α is fully charged. Typically, the ECU 13 determines whether the battery pack 12α is fully charged (SOC (State Of Charge)=100%) based on the voltage of the battery pack 12α.

[0053] If it is determined that the battery pack α is fully charged (YES in step S3), the ECU 13 starts charging the remaining two battery packs (also referred to as "battery pack β" and "battery pack γ") among the three battery packs 12A, 12B, and 12C excluding the battery pack α. If it is determined that the battery pack α is not fully charged (NO in step S3), the ECU 13 continues charging the battery pack α until it is fully charged.

[0054] In step S5, the ECU 13 judges whether the total amount of charge stored in the three assembled batteries 12A, 12B, and 12C (i.e., assembled batteries α, β, and γ) has reached Qs. If it is judged that the total amount of charge stored in the three assembled batteries 12A, 12B, and 12C has not reached Qs (NO in step S5), the ECU 13 continues the charging in step S4 or the charging in step S5. If it is judged that the total amount of charge stored in the three assembled batteries 12A, 12B, and 12C has reached Qs (YES in step S5), the ECU 13 ends the series of charging processes.

[0055] In the above description, an example has been given in which the charging of battery pack β and battery pack γ is started after battery pack α is fully charged. However, the present invention is not limited to this. ECU 13 may start charging the three battery packs α, β, and γ simultaneously. Alternatively, ECU 13 may start charging battery packs β and γ during the charging of battery pack α.

[0056] <E. Parentheses> As described above, the power storage system 1 performs charge and discharge with the external system 900. The power storage system 1 includes a PCU 11 connected to the external system 900, and a plurality of battery packs 12 (12A to 12C) for the above charge / discharge purpose, which are connected in parallel to the PCU 11, and an ECU 13 that controls the operation of the PCU 11 so that the total amount of stored electricity after charging each battery pack 12 becomes a predetermined amount Qs when charging each battery pack 12.

[0057] When charging each battery pack 12, if there is a battery pack α among the plurality of battery packs 12 in which a predetermined time has elapsed since the previous full charge, ECU 13 charges battery pack α until it is fully charged, and adjusts the stored electricity amounts of battery packs β and γ other than battery pack α among the plurality of battery packs 12 so that the total amount of stored electricity after charging each battery pack 12 becomes a predetermined amount Qs.

[0058] According to such a configuration, it is possible to fully charge battery pack α among the three battery packs 12 that perform charge and discharge with the external system 900. Therefore, it is possible to fully charge battery pack α without using an adjustment battery different from the three battery packs 12 that perform charge and discharge with the external system 900.

[0059] If there are a plurality of battery packs among the plurality of battery packs 12 in which a predetermined time has elapsed since the previous full charge, ECU 13 may preferentially fully charge the one with the longer elapsed time. Alternatively, ECU 13 may fully charge all of the plurality of battery packs 12.

[0060] <Method for Setting Threshold Value F> Hereinafter, a plurality of examples will be given to explain the method for setting the threshold values Ta_th, Tb_th, and Tc_th. Note that hereinafter, when the threshold values Ta_th, Tb_th, and Tc_th are not distinguished, they are referred to as "threshold value T_th". The threshold value T_th is set before the actual operation of the power storage system 1.

[0061] (1) First Method Using the ECU 13 or another device (not shown), before the actual operation of the power storage system 1, the error between the integrated value of the current when the battery pack 12 is charged or discharged for a predetermined time and the theoretical value of the current flowing during the predetermined time is calculated for each battery pack 12.

[0062] The threshold value T_th (predetermined time length) is set for each battery pack 12 before the actual operation based on the above error. For example, the threshold value Ta_th is set before the actual operation based on the error between the integrated value of the current when the battery pack 12A is charged or discharged for a predetermined time and the theoretical value of the current flowing during the predetermined time. Specifically, the larger the error, the shorter the threshold value T_th is set. Note that the determination of the threshold value T_th may be performed by another device or by the ECU 13. As long as the determined threshold value T_th is finally stored in the ECU 13.

[0063] When the above error is large, the estimation accuracy of the SOC becomes low. By charging the battery pack 12 (battery pack α) to full charge earlier, the estimation accuracy of the SOC can be improved. Therefore, as described above, the larger the above error, the shorter the threshold value T_th, which is the reference time for determining the necessity of performing full charge, is set, so that the estimation accuracy of the SOC can be quickly improved.

[0064] (2) Second Method Using the ECU 13 or another device (not shown), the variation in the self-discharge amount of each cell 121 (see FIG. 2 ) is calculated for each assembled battery 12 before the actual operation of the power storage system 1. The threshold value T_th (a predetermined length of time) is set for each assembled battery 12 before the actual operation based on the magnitude of the variation in the self-discharge amount. In particular, the threshold value T_th is set shorter as the variation in the self-discharge amount increases. Note that the threshold value T_th may be determined by another device or by the ECU 13. It is sufficient that the determined threshold value T_th is finally stored in the ECU 13.

[0065] The greater the variation in the self-discharge amount, the earlier it is preferable to perform equalization control of each of the multiple cells 121 in the battery pack 12. When the battery pack 12 is fully charged, each cell 121 in the battery pack 12 is also fully charged, so that the cells 121 can be equalized in the battery pack 12. Therefore, as described above, by setting the threshold value T_th, which is the reference time for determining whether or not full charging is required, to be shorter as the variation in the self-discharge amount is greater, the cells 121 can be equalized more quickly in the battery pack 12 that requires the cells 121 to be equalized.

[0066] (3) The third method As shown in FIG. 2, the power storage system 1 (specifically, the battery unit 10) includes a plurality of voltage detection circuits 122 that are provided in association with the plurality of cells 121, respectively, and each detects the voltage of the cell 121.

[0067] Using a device not shown, the impedance variation of each voltage detection circuit 122 is calculated for each battery pack 12 before the power storage system is put into practical use. A threshold value T_th (a predetermined length of time) is set for each battery pack 12 before the power storage system is put into practical use, based on the magnitude of the variation. In particular, the threshold value T_th is set shorter as the impedance variation increases. Note that the threshold value T_th may be determined by another device or by the ECU 13. The determined threshold value T_th may be finally stored in the ECU 13.

[0068] The greater the impedance variation, the greater the self-discharge variation. As the self-discharge variation increases, as described above, it is preferable to perform the equalization control of each cell 121 in the plurality of cells 121 in the assembled battery 12 earlier. When the assembled battery 12 is fully charged, each cell 121 in the assembled battery 12 is also fully charged, so the equalization of the cells 121 can be performed in the assembled battery 12. Therefore, as described above, the greater the impedance variation, the shorter the threshold value T_th, which is the reference time for determining the necessity of full charge execution, is set, so that the equalization of the cells 121 can be performed more promptly for the assembled battery 12 that requires equalization of the cells 121.

[0069] <G. Modification Example> (1) When adjusting the stored power of a plurality of assembled batteries β and γ, when the assembled battery β is a ternary battery and the assembled battery γ is an LPF battery, the ECU 13 may be configured to control the PCU 11 so that the stored power of the ternary battery (assembled battery β) is greater than the stored power of the LPF battery (assembled battery γ).

[0070] The internal resistance of the LPF battery is higher than that of the ternary battery. Therefore, by making the stored power of the ternary battery with the lower resistance greater than the stored power of the LPF battery (prioritizing the charging of the ternary battery) during adjustment, the power consumption can be reduced compared to the case where the stored power of the LPF battery is made greater than the stored power of the ternary battery.

[0071] (2) In the above, the configuration in which three assembled batteries 12 can be connected to the PCU 11 has been described as an example, but it is not limited thereto. The PCU and the power storage system 1 may be configured such that two or four or more assembled batteries are connected to the PCU.

[0072] <H. Supplementary Note> (1) A control method for a control device included in a power storage system that performs charge and discharge with an external system, When charging a plurality of assembled batteries connected in parallel to a power conversion device connected to the external system, the control device controls an operation of the power conversion device so that a total amount of stored power in each of the assembled batteries after charging becomes a predetermined amount; a step of determining, by the control device, whether or not a first assembled battery is present among the plurality of assembled batteries for which a predetermined time has elapsed since the last time the assembled batteries were fully charged, when the control device is charging each of the assembled batteries; the step of controlling the operation of the power conversion device includes a step of, when the first assembled battery is present, charging the first assembled battery until it is fully charged, and adjusting the amount of stored power of a second assembled battery other than the first assembled battery among the plurality of assembled batteries so that a total amount of stored power after charging of each of the assembled batteries becomes the predetermined amount.

[0073] (2) A program for causing one or more processors (eg, processor 131 of ECU 13) to execute each step of the control method.

[0074] (3) A non-transitory computer-readable storage medium storing the program. 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 scope of the claims, and it is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. [Explanation of symbols]

[0075] 1 Energy storage system, 10, 10A, 10B Battery unit, 12, 12A, 12B, 12C Battery pack, 20 Upper controller, 111, 112, 113 Terminal, 120 Unit, 121 Cell, 122 Voltage detection circuit, 123 Ammeter, 124 charge / discharge A circuit for use in the photovoltaic power generation system, 131 a processor, 132 a memory, 900 an external system, 920 a photovoltaic power generation system, 930 a load, 940 a power system, 1221, 1222 connection terminals, 1223 a voltmeter, 1241 a switch, and a NW network.

Claims

1. A power storage system that charges and discharges between an external system, A power converter connected to the external system; A plurality of the charge / discharge assembled batteries connected in parallel to the power conversion device; a control device that controls an operation of the power conversion device so that a total amount of stored power in each of the battery packs after charging the battery packs becomes a predetermined amount when the battery packs are charged; The control device, when charging each of the assembled batteries, if there is a first assembled battery among the plurality of assembled batteries for which a predetermined time has elapsed since it was last fully charged, charges the first assembled battery until it is fully charged, and adjusts the amount of stored power of a second assembled battery other than the first assembled battery among the plurality of assembled batteries so that the total amount of stored power after charging of each of the assembled batteries becomes the predetermined amount.

2. Before the power storage system is put into practical use, an error between an integrated value of a current when the battery pack is charged or discharged for a predetermined time and a theoretical value of a current flowing in the predetermined time is calculated for each battery pack; the predetermined length of time is set for each of the assembled batteries prior to the actual operation based on the error; The power storage system according to claim 1 , wherein the predetermined time length is set to be shorter as the error is larger.

3. Each of the assembled batteries includes a plurality of cells, Before the power storage system is put into practical use, a variation in a self-discharge amount of each of the cells is calculated for each of the assembled batteries; the predetermined length of time is set for each of the assembled batteries prior to the actual operation based on the magnitude of the variation; The power storage system according to claim 1 , wherein the length of the predetermined time is set to be shorter as the variation is larger.

4. Each of the assembled batteries includes a plurality of cells, the power storage system further includes a plurality of voltage detection circuits each corresponding to one of the plurality of cells and each detecting a voltage of the cell; Before the power storage system is put into practical use, a variation in impedance of each of the voltage detection circuits is calculated for each of the assembled batteries; the predetermined length of time is set for each of the assembled batteries prior to the actual operation based on the magnitude of the variation; The power storage system according to claim 1 , wherein the length of the predetermined time is set to be shorter as the variation is larger.

5. 5. The power storage system according to claim 1, wherein when the control device adjusts the storage amounts of the plurality of second assembled batteries and when the plurality of second assembled batteries include ternary lithium-ion batteries and iron phosphate lithium-ion batteries, the control device controls the operation of the power conversion device so that the storage amount of the ternary lithium-ion batteries is greater than the storage amount of the iron phosphate lithium-ion batteries.

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