Control device

Abstract

To improve the accuracy of estimating the states of charge even when the amount of charge approaches a lower limit at the time of estimating the states of charge in a plurality of types of secondary batteries.SOLUTION: A power storage device 2 includes a plurality of types of secondary batteries 211, 221 and a control device 23 that determines the discharge order of the secondary batteries 211, 221. When a value indicating the overall power storage state of the secondary batteries 211, 221 falls below a threshold, the control device 23 preferentially discharges the low-accuracy battery 221, which has a relatively low estimation accuracy of the power storage state, over the high-accuracy battery 211, which has a relatively high estimation accuracy of the power storage state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a control device. [Background technology]

[0002] A current integration method as described in Patent Document 1 below is known as a method for calculating the state of charge (SOC) and remaining capacity of a power storage cell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-132800 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, when a plurality of storage cells of the same type are provided, the state of charge can be estimated with a certain degree of accuracy. However, when a plurality of storage cells of different types are provided, there may be a mixture of storage cells for which the estimation accuracy of the state of charge using the current integration method is high and storage cells for which the estimation accuracy of the state of charge using the current integration method is low. In such cases, the estimation accuracy of the state of charge as a whole decreases. When the estimation accuracy of the state of charge as a whole decreases, it is conceivable that the actual state of charge is lower than the estimated state of charge. In this state, if the state of charge is estimated by continuing to discharge from the storage cells, a sudden drop in the estimated value may occur near the lower limit.

[0005] The present disclosure aims to improve the accuracy of estimating the state of charge in a plurality of types of secondary batteries even when the amount of stored power approaches a lower limit. [Means for solving the problem]

[0006] The present disclosure provides a power storage device including a plurality of types of secondary batteries and a control device that determines a discharge order for the plurality of types of secondary batteries. When a value indicating the overall state of charge of the plurality of types of secondary batteries falls below a threshold, the control device preferentially discharges low-accuracy batteries that are included in the plurality of types of secondary batteries and have a relatively low estimation accuracy for the state of charge, over high-accuracy batteries that are included in the plurality of types of secondary batteries and have a relatively high estimation accuracy for the state of charge. [Effects of the Invention]

[0007] According to the present disclosure, when estimating the state of charge of a plurality of types of secondary batteries, it is possible to improve the accuracy of estimating the state of charge even when the amount of stored power approaches the lower limit. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram for explaining the power storage system according to this embodiment. [Figure 2] FIG. 2 is a flowchart illustrating the processing of the battery integrated ECU shown in FIG. [Figure 3] FIG. 3 is a flowchart illustrating the processing of the battery integrated ECU shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0010] The power storage system S in this embodiment will be described with reference to Fig. 1. The power storage system S is a system that stores power generated by power generation facilities (including wind power generation, solar power generation, etc.) not shown. The power storage system S is also a system that supplies the stored power to a grid not shown. The power storage system S includes a power storage device 2, an EMS (Energy Management System) 3, and a PCS (Power Conditioning System) 4.

[0011] The EMS 3 outputs a discharge command to the power storage device 2. The PCS 4 controls the power supplied to the grid, and is an inverter that converts a direct current input from the power storage device 2 into an alternating current.

[0012] The power storage device 2 includes a plurality of battery packs 21, a plurality of battery packs 22, a battery integrated ECU 23, and a boost converter 24. The battery pack 21 includes a ternary battery cell 211, a voltage sensor 212, a current sensor 213, and a battery pack ECU 214.

[0013] The ternary battery cell 211 is a ternary lithium-ion battery whose positive electrode is a composite material containing three metal elements in which part of the cobalt in lithium cobalt oxide has been replaced with nickel and manganese. A plurality of ternary battery cells 211 are provided and connected in series.

[0014] The voltage sensor 212 is a sensor that measures the voltage of the ternary battery cell 211. The voltage sensor 212 may measure the voltage of each individual ternary battery cell 211, or may measure the voltage of multiple ternary battery cells 211. The voltage sensor 212 outputs a signal indicating the measured voltage to the battery pack ECU 214.

[0015] The current sensor 213 is a sensor that measures the current of the ternary battery cell 211. The current sensor 213 measures the current flowing through the multiple ternary battery cells 211. The current sensor 213 outputs a signal indicating the measured current to the battery pack ECU 214.

[0016] The battery pack ECU 214 generates voltage information and current information for the ternary battery cell 211 based on the received signals indicating the voltage and current, and transmits the information to the battery integrated ECU 23. Based on the discharge instruction information transmitted from the battery integrated ECU 23, the battery pack ECU 214 drives a relay (not shown) to discharge the ternary battery cell 211.

[0017] The battery pack 22 includes an LFP battery cell 221 , a voltage sensor 222 , a current sensor 223 , and a battery pack ECU 224 .

[0018] The LFP battery cell 221 is an iron phosphate lithium ion battery that uses lithium iron phosphate for the positive electrode. A plurality of LFP battery cells 221 are provided and connected in series.

[0019] The voltage sensor 222 is a sensor that measures the voltage of the LFP battery cell 221. The voltage sensor 222 may measure the voltage of each LFP battery cell 221, or may measure the voltage of multiple LFP battery cells 221. The voltage sensor 222 outputs a signal indicating the measured voltage to the battery pack ECU 224.

[0020] The current sensor 223 is a sensor that measures the current of the LFP battery cell 221. The current sensor 223 measures the current flowing through the plurality of LFP battery cells 221. The current sensor 223 outputs a signal indicating the measured current to the battery pack ECU 224.

[0021] The battery pack ECU 224 generates voltage information and current information for the LFP battery cell 221 based on the received signals indicating the voltage and current, and transmits the information to the battery integrated ECU 23. The battery pack ECU 224 drives a relay (not shown) based on the discharge instruction information transmitted from the battery integrated ECU 23, causing the LFP battery cell 221 to discharge.

[0022] The boost converter 24 boosts and converts the DC voltage input from the battery packs 21, 22 to an arbitrary DC voltage and outputs it to the PCS 4. Note that the boost converter 24 does not necessarily have to be installed. The battery integrated ECU 23 is a control device that controls the charging and discharging of the battery packs 21, 22. The battery integrated ECU 23 receives voltage information and current information transmitted from the battery pack ECUs 214, 224. The battery integrated ECU 23 uses the received voltage information and current information to estimate the charge states of the ternary battery cells 211 and the LFP battery cells 221. The battery integrated ECU 23 transmits discharge instruction information to the battery pack ECUs 214, 224.

[0023] Next, the processing flow of the battery integrated ECU 23 will be described with reference to Fig. 2. In step S01, the battery integrated ECU 23 determines whether or not there is a discharge command. The discharge command is transmitted from the EMS 3. If there is a discharge command (step S01: YES), the process proceeds to step S02. If there is no discharge command (step S01: NO), the determination in step S01 is repeated.

[0024] In step S02, the battery integrated ECU 23 determines whether there are battery packs with different estimation accuracies for the state of charge (SOC) such as SOC and remaining capacity (hereinafter also simply referred to as "SOC"). In this embodiment, as described with reference to FIG. 1, the battery packs 21 and 22 controlled by the battery integrated ECU 23 each include a ternary battery cell 211 and an LFP battery cell 221, and therefore there are battery packs with different SOC estimation accuracies.

[0025] If there are battery packs with different SOC estimation accuracies (step S02: YES), the process proceeds to step S03. If there are no battery packs with different SOC estimation accuracies (step S02: NO), the process proceeds to step S04. Steps S04 to S07 are processes performed when the battery packs with different SOC estimation accuracies, as described with reference to FIG. 1, are not included. Prior to describing step S03, the processes from step S04 to step S07 will be described.

[0026] In step S04, the battery integrated ECU 23 executes a normal discharge process in accordance with the discharge command. The normal discharge process is a process in which, for example, if the SOC of all the battery packs is within a certain range, all the battery packs are uniformly discharged.

[0027] In step S05 following step S04, the battery integrated ECU 23 determines whether the system SOC is equal to or lower than a threshold SOCth. The system SOC is the SOC of the entire power storage device and can be calculated, for example, as the average value of the SOCs of all the battery packs included in the power storage device. The threshold SOCth is a threshold that is set to indicate that voltage monitoring is necessary when the system SOC falls below this threshold.

[0028] If the system SOC≦SOCth (step S05: YES), the process proceeds to step S06. If the system SOC≦SOCth is not satisfied (step S05: NO), the process proceeds to step S04.

[0029] In step S06, the battery integrated ECU 23 determines whether the measured voltage V is equal to or less than the threshold voltage Vth. The measured voltage is a value obtained by measuring the voltage of each cell or the voltage of the battery pack. If the measured voltage V is equal to or less than the threshold voltage Vth (step S06: YES), the process proceeds to step S07. If the measured voltage V is not equal to or less than the threshold voltage Vth (step S06: NO), the process of step S06 is repeated. In step S07, the battery integrated ECU 23 executes a discharge stop process and ends the process.

[0030] In step S03, if it is determined in step S02 that there are battery packs with different SOC estimation accuracies, the battery integrated ECU 23 executes a discharge promotion process for the low-accuracy battery. The discharge promotion process for the low-accuracy battery will be described with reference to FIG. 3.

[0031] 3, the battery integrated ECU 23 executes a normal discharge process in accordance with the discharge command. The normal discharge process is a process in which, for example, if the SOC of all the battery packs is within a certain range, all the battery packs are uniformly discharged.

[0032] In step S22 following step S21, the battery integrated ECU 23 determines whether the system SOC is equal to or lower than a threshold SOCth. The system SOC is the SOC of the entire power storage device and can be calculated, for example, as the average value of the SOCs of all the battery packs included in the power storage device. The threshold SOCth is a threshold that is set to indicate that voltage monitoring is necessary when the system SOC falls below this threshold.

[0033] If the system SOC≦SOCth (step S22: YES), the process proceeds to steps S23 and S31. If the system SOC≦SOCth is not satisfied (step S22: NO), the process proceeds to step S21.

[0034] In step S23, the battery integrated ECU 23 determines whether the measured voltage V is equal to or less than the threshold voltage Vth. The measured voltage is a value obtained by measuring the voltage of each cell or the voltage of the battery pack. If the measured voltage V is equal to or less than the threshold voltage Vth (step S23: YES), the process proceeds to step S24. If the measured voltage V is not equal to or less than the threshold voltage Vth (step S23: NO), the process of step S23 is repeated. In step S24, the battery integrated ECU 23 executes a discharge stop process and ends the process.

[0035] Next, we will explain the discharge battery switching process, which includes the processes of steps S31, S32, S33, S34, and S35. The voltage check described in steps S23 and S24 above is performed in parallel during the discharge battery switching process, and if the measured voltage V becomes equal to or lower than the threshold voltage Vth, the discharge stop process is performed even during the discharge battery switching process.

[0036] In step S31, the battery integrated ECU 23 executes a priority discharge process for the LFP battery cell 221. The battery integrated ECU 23 transmits a discharge command to the battery pack ECU 224, and transmits a discharge stop process to the battery pack ECU 214.

[0037] In step S32 following step S31, the battery integrated ECU 23 determines whether the dischargeable value Wout of the LFP battery cell 221 has become equal to or less than the discharge command value. The dischargeable value Wout of the LFP battery cell 221 is transmitted from the battery pack ECU 224 to the battery integrated ECU 23 as needed.

[0038] If the dischargeable value Wout≦the discharge command value (step S32: YES), the process proceeds to step S33. If the dischargeable value Wout is not equal to or less than the discharge command value (step S32: NO), the process proceeds to step S31.

[0039] In step S33, the battery integrated ECU 23 executes a process of making up for the shortfall in discharge command value by discharging the ternary battery cells 211 while executing a prioritized discharge process for the LFP battery cells 221. The battery integrated ECU 23 transmits a discharge command to the battery pack ECU 224 to continue discharge equivalent to the dischargeable value Wout of the LFP battery cells 221. The battery integrated ECU 23 transmits a discharge command to the battery pack ECU 214 to perform discharge equivalent to the difference between the discharge command value and the dischargeable value Wout.

[0040] In step S34 following step S33, the battery integrated ECU 23 determines whether the SOC of the LFP battery cell 221 has become 0. If the SOC of the LFP battery cell 221 has become 0 (step S34: YES), the process proceeds to step S35. If the SOC of the LFP battery cell 221 has not become 0 (step S34: NO), the process proceeds to step S33.

[0041] In step S35, the battery integrated ECU 23 stops the discharge process of the LFP battery cell 221 and executes a process to perform discharge corresponding to the discharge command value in the ternary battery cell 211. The battery integrated ECU 23 transmits a command to the battery pack ECU 224 to stop discharge of the LFP battery cell 221. The battery integrated ECU 23 transmits a discharge command to the battery pack ECU 214 to perform discharge corresponding to the discharge command value. When the process of step S35 ends, the process proceeds to step S23.

[0042] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise.

[0043] [Note] Notes 1 to 4 below can be combined in any way as long as there is no technical contradiction.

[0044] [Appendix 1] Multiple types of secondary batteries; a control device that determines the discharge order of the plurality of types of secondary batteries, The control device is a storage device that, when a value indicating the overall charge state of multiple types of secondary batteries falls below a threshold, preferentially discharges low-precision batteries that are included in the multiple types of secondary batteries and have relatively low estimation accuracy for the charge state, over high-precision batteries that are included in the multiple types of secondary batteries and have relatively high estimation accuracy for the charge state.

[0045] In the energy storage device 2 of this embodiment, the low-accuracy battery is exemplified by the LFP battery cell 221, the high-accuracy battery is exemplified by the ternary battery cell 211, and the control device is exemplified by the battery integrated ECU 23. The low-accuracy battery may be any battery with a relatively low estimation accuracy of the state of charge, and is not limited to an LFP battery. The high-accuracy battery may be any battery with a relatively high estimation accuracy of the state of charge, and is not limited to a ternary battery.

[0046] According to Supplementary Note 1, when the value indicating the charge state of the entire secondary battery falls below a threshold, the low-accuracy battery is preferentially discharged. Therefore, the low-accuracy battery, which has a low estimation accuracy of the charge state, is discharged first. When the charge state of the entire secondary battery decreases, the high-accuracy battery is primarily discharged, thereby improving the estimation accuracy of the charge state of the entire secondary battery.

[0047] [Appendix 2] The storage device according to claim 1, wherein the control device discharges the low-accuracy battery and suppresses discharge of the high-accuracy battery when a value indicating the overall charge state of the multiple types of secondary batteries falls below a threshold.

[0048] According to Appendix 2, when the value indicating the charge state of the entire secondary battery falls below a threshold, the low-precision battery is discharged and the discharge of the high-precision battery is suppressed, so that the low-precision battery can be discharged first without deteriorating the charge state of the high-precision battery.

[0049] In the above embodiment, the discharge of the high-precision battery is stopped, but this is not necessarily limited to stopping it, and the discharge of the high-precision battery can be suppressed to the extent that the discharge of the low-precision battery is prioritized.

[0050] [Appendix 3] The control device is configured to, when the value indicating the charge state of the low-accuracy battery becomes equal to or lower than a threshold value as a result of preferentially discharging the low-accuracy battery, suppress discharge of the low-accuracy battery and discharge the high-accuracy battery.

[0051] According to Supplementary Note 3, when the amount of stored power in the low-precision battery decreases as a result of the preferential discharge of the low-precision battery, the discharge of the low-precision battery is suppressed and the high-precision battery is discharged. Therefore, when the state of charge of the entire secondary battery decreases, the high-precision battery is primarily discharged, thereby improving the accuracy of estimating the amount of stored power in the entire secondary battery.

[0052] [Appendix 4] 4. The power storage device according to any one of appendices 1 to 3, wherein the high-precision battery is a ternary lithium-ion battery, and the low-precision battery is an iron phosphate lithium-ion battery. [Explanation of symbols]

[0053] S: Energy storage system 2: Energy storage device 21, 22: Battery pack 23: Battery integrated ECU (controller)

Claims

1. Multiple types of secondary batteries; a control device that determines a discharge order of the plurality of types of secondary batteries, When a value indicating the overall charge state of the multiple types of secondary batteries falls below a threshold, the control device preferentially discharges low-accuracy batteries that are included in the multiple types of secondary batteries and have a relatively low estimation accuracy for the charge state, over high-accuracy batteries that are included in the multiple types of secondary batteries and have a relatively high estimation accuracy for the charge state.

2. The power storage device according to claim 1 , wherein the control device discharges the low-accuracy battery and suppresses discharging of the high-accuracy battery when a value indicating the overall charge state of the plurality of types of secondary batteries becomes equal to or less than a threshold value.

3. The storage device according to claim 2, wherein the control device suppresses discharging of the low-accuracy battery and discharges the high-accuracy battery when, as a result of preferentially discharging the low-accuracy battery, a value indicating the charge state of the low-accuracy battery becomes equal to or less than a threshold value.

4. The power storage device according to claim 1 , wherein the high-precision battery is a ternary lithium-ion battery, and the low-precision battery is an iron phosphate lithium-ion battery.

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