JPWO2018203509A1 - Energy storage system and inspection method for minute short circuit - Google Patents

Abstract

The power storage system 50 has a plurality of power storage blocks 60A to 60C connected to the common line Lo in parallel by parallel lines La to Lc. Each of the power storage blocks 60A to 60C includes a plurality of power storage elements 63 connected in series, and switches 65A to 65C provided on the parallel lines La to Lc. By switching the switches 65A to 65C from on to off, the power storage system 50 disconnects the plurality of power storage elements 63 of the power storage blocks 60A to 60C from the common line Lo, and inspects a minute short circuit in the power storage elements 63. Inspection units 77A to 77C to perform inspection.

Description

  The present invention relates to a technique for inspecting a micro short circuit.

  A part of the separator that separates the positive electrode and the negative electrode may be damaged, and the positive electrode and the negative electrode may be short-circuited (hereinafter, short-circuited) inside the battery. The micro short circuit is inspected at the time of shipment of the battery, but may occur even after the shipment due to lithium deposition or the like accompanying charging at a low temperature. Therefore, it has been desired to inspect the occurrence of a micro short circuit during actual use of the battery. Patent Document 1 discloses a method for inspecting a micro short circuit during actual use of a battery. In this document, after charging a battery to a specified voltage VK, the presence or absence of a micro short circuit is inspected by focusing on a voltage difference between cells when a specified elapsed time TK has elapsed.

Japanese Patent Application Laid-Open No. 2006-75567

In order to improve the inspection accuracy of a micro short circuit, it is preferable that the power storage element be set to a no-current state during the inspection. No-current state ”). However, during actual operation of a power storage system including a plurality of power storage blocks connected in parallel, the power storage elements included in each power storage block do not enter a currentless state unless the entire power storage system is stopped. Therefore, it has been desired to accurately inspect a minute short circuit in a power storage element without putting the entire power storage system in a no-current state.
An object of the present invention is to accurately inspect a minute short circuit in a power storage element without putting the entire power storage system in a no-current state.

The power storage system includes a plurality of power storage blocks connected to a common line in parallel by parallel lines, and each of the power storage blocks includes a plurality of power storage elements connected in series and a switch provided on the parallel line. The power storage system further includes an inspection unit that disconnects the plurality of power storage elements of the power storage block from the common line by switching the switch from on to off, and detects a micro short circuit in the plurality of power storage elements. .
The method for inspecting a micro short circuit includes switching a switch provided on a parallel line connecting a plurality of power storage blocks in parallel to a common line from on to off to disconnect a predetermined power storage block from the common line, and operating the power storage system. And inspecting the plurality of power storage elements included in the separated power storage block for minute short-circuits.

  With the above configuration, a minute short circuit in the power storage element can be accurately inspected without putting the entire power storage system in a no-current state.

FIG. 2 is a block diagram illustrating an electrical configuration of the UPS according to the first embodiment. FIG. 2 is a block diagram illustrating an electric configuration of a power storage system. Circuit diagram of discharge circuit SOC-OCV correlation graph of secondary battery Flow chart showing the flow of inspection processing for a micro short circuit 7 is a graph showing SOC-OCV characteristics of a secondary battery according to another embodiment.

The power storage system includes a plurality of power storage blocks connected to a common line in parallel by parallel lines, and each of the power storage blocks includes a plurality of power storage elements connected in series and a switch provided on the parallel line. The power storage system further includes an inspection unit configured to disconnect the plurality of power storage elements of the power storage block from the common line by switching the switch from on to off, and to test a minute short circuit in the plurality of power storage elements. . With this configuration, a minute short circuit in the power storage element can be accurately inspected without putting the entire power storage system in a no-current state.
Conventionally, during operation of a power storage system having a plurality of power storage blocks connected in parallel, an inspection for detecting a micro short circuit of a power storage element has not been performed. Micro short circuits tend to be difficult to detect in a short inspection. It takes a relatively long time (for example, several hours to several days) to detect a micro short circuit while leaving the electric storage element in a no-current state. Instead of detecting a small short circuit of a storage element, a typical conventional power storage system generates an alarm by detecting that the performance of a certain storage block deviates from a normal value / expected value during operation. In other words, the conventional power storage system does not detect the event of the early stage, that is, a minute short circuit of the power storage element, and issues an alarm after the performance of the power storage element and the power storage block is significantly reduced. After the alarm is issued, the power storage system may be forced to stop operating while the worker checks the power storage system.
As a part of preventive maintenance for avoiding the stoppage of the operation of the power storage system, the influence on the operation of the power storage system can be reduced by detecting a minute short circuit in the power storage element at an early stage.

  By switching the switches from on to off one by one, the power storage blocks to be tested may be separated one by one to test for a minute short circuit of the power storage element. With this configuration, it is possible to suppress a decrease in capacity and a decrease in output of the power storage system as compared with a case where a plurality of power storage blocks are simultaneously disconnected.

  The inspection unit may inspect the storage element for a short circuit based on the voltage of the storage element after a predetermined time has elapsed since the switch was turned off. In the case where a micro short circuit has occurred, when the power storage block is disconnected, the voltage of the power storage element decreases early. Therefore, by monitoring the voltage of the power storage element after the elapse of the predetermined time, a minute short circuit of the power storage element can be accurately inspected.

  The inspection unit may inspect the storage element for a short circuit based on a voltage difference between before and after a predetermined time has elapsed. With this configuration, when there is no change or little change in the environmental temperature or the like, the voltage change caused by the minute short circuit can be accurately detected, and therefore, the minute short circuit of the power storage element can be accurately inspected.

  The inspection unit is configured to compare a voltage difference between before and after the predetermined time of the power storage element with an average value of the voltage differences before and after the predetermined time of all the power storage elements constituting the power storage block, It is advisable to inspect for micro shorts. With this configuration, even if there is a change in the environmental temperature or the like, a minute short circuit of the power storage element can be accurately inspected.

  The power storage element has a high change area in which an amount of change in OCV with respect to an amount of change in SOC is higher than a predetermined value in an SOC-OCV characteristic. It is preferable to detect the voltage of the power storage element and check for a short circuit based on the detected voltage. Since the change amount of the OCV with respect to the change amount of the SOC is large in the high change region, a minute short circuit of the power storage element can be accurately inspected.

  The power storage device may further include a correction unit that corrects the SOC of the power storage device based on the voltage of the power storage device detected in the high change region. With this configuration, the SOC can be corrected together with the inspection for the minute short circuit. In the high change region, the change amount of the OCV with respect to the change amount of the SOC is large, so that the SOC can be corrected with high accuracy. In addition, since only the power storage block to be tested is in a no-current state, there is an advantage that the SOC can be corrected at any time during the operation of the power storage system.

  The power storage block includes an equalization circuit provided for each of a plurality of power storage elements connected in series, and the inspection unit operates the equalization circuit in the high-change area, and After equalizing the voltage of the storage element, the switch may be turned off to separate the storage block to be inspected. With this configuration, it is possible to equalize the voltage of each power storage element together with the inspection for a minute short circuit. In addition, since the detection of the minute short circuit is performed in a state where the voltages of the respective storage elements are equalized, it is possible to suppress the variation in the inspection accuracy of the minute short circuit between the respective storage elements as compared with the case where the voltages are not uniform.

  The storage element may be a lithium ion secondary battery having a flat plateau region in SOC-OCV characteristics. In the plateau region, even if the SOC changes, the OCV hardly changes, so that it is difficult to inspect a minute short circuit with high accuracy. However, by applying the present technology, the minute short circuit can be inspected with high accuracy.

<First embodiment>
Embodiment 1 of the present invention will be described with reference to FIGS.
1. FIG. 1 is a block diagram showing an electrical configuration of a UPS (Uninterruptible Power Supply).
The UPS 10 includes a converter 20, an inverter 30, a charge control circuit 41, a diode 45, and a power storage system 50.
Converter 20 and inverter 30 are arranged on path 15. Converter 20 converts AC to DC, and inverter 30 converts DC to AC. The charge control circuit 41 is a circuit that controls charging of the power storage system 50.

  Power storage system 50 is connected to path 15 connecting converter 20 and inverter 30 via charge control circuit 41. The diode 45 is connected to the path 15 in parallel with the charge control circuit 41.

  The UPS 10 is an always-inverter power supply system. When the AC power supply is normal, the converter 20 converts AC to DC, the inverter 30 converts DC to AC, and supplies power to the load. When the AC power supply is abnormal, the converter 20 is stopped, and power is supplied from the power storage system 50 to the load via the diode 45 and the inverter 30.

  Charging of the power storage system 50 is performed when the AC power supply is normal. Specifically, a charging current is supplied via the AC power supply, the converter 20, and the charging control circuit 41 to charge the power storage system 50. The charge control circuit 41 performs constant-current charging control on the power storage system 50 when the remaining capacity of the power storage system 50 is small, and performs constant-voltage charging control to maintain a floating voltage when the power storage system 50 is fully charged.

  FIG. 2 is a block diagram showing an electrical configuration of the power storage system. The power storage system 50 includes a plurality (three in the example of FIG. 2) of power storage blocks 60A to 60C and an integrated management unit 100. The integrated management unit 100 may be a monitoring server. Hereinafter, power storage blocks 60A to 60C are collectively referred to as “power storage block 60”.

The power storage blocks 60A to 60C are connected in parallel to common lines (common charge / discharge paths) Lo connected to the charge control circuit 41 and the diode 45 via parallel lines La to Lc. The power storage blocks 60A to 60C individually manage a plurality of secondary batteries (cells) 63 connected in series, switches 65A to 65C, current sensors 67A to 67C, a discharge circuit 71, sensor units 75A to 75C. Parts 77A to 77C. FIG. 2 shows only a part of the secondary battery 63, and actually, six or more secondary batteries are connected in series. The individual management units 77A to 77C correspond to the “inspection unit” of the present invention.
Although not shown, a plurality of power storage blocks 60A may be connected in series to the parallel line La to form a so-called bank. Similarly, a plurality of power storage blocks 60B and a plurality of power storage blocks 60C may be connected in series to the parallel line Lb and the parallel line Lc, respectively, to form a bank. In the bank, the switches 65A to 65C may be provided only in the power storage block closest to the common line Lo (the power storage block on the most upstream side in the charging path of the parallel lines La to Lc).

  Switches 65A to 65C are arranged on parallel lines La to Lc. By switching each of the switches 65A to 65C from on to off, each of the power storage blocks 60A to 60C can be disconnected from the common line Lo. By switching the switches 65A to 65C from on to off, the plurality of secondary batteries 63 connected in series to the switches 65A to 65C can be separated from the charge / discharge path. The switches 65A to 65C can be configured by contact switches (mechanical switches) such as relays and semiconductor switches such as FETs and transistors.

  The discharge circuit (balancer) 71 is provided individually for each secondary battery 63. The discharging circuit 71 includes a discharging resistor 72 and a discharging switch 73 as shown in FIG. When the discharge switch 73 is turned on, the secondary battery 63 is discharged via the discharge resistor 72. The discharge circuit 71 is provided to equalize the voltage of the plurality of secondary batteries 63 connected in series.

  The sensor units 75A to 75C are provided for each of the plurality of secondary batteries 63. Each of the sensor units 75A to 75C has a voltage detection circuit, and detects the voltage of each corresponding secondary battery 63. The current sensors 67A to 67C detect a current flowing in each of the power storage blocks 60A to 60C or the bank.

  The individual management units 77A to 77C monitor the states of the power storage blocks 60A to 60C based on the outputs of the current sensors 67A to 67C and the outputs of the sensor units 75A to 75C. The individual management units 77A to 77C perform processing for estimating the SOC of each of the secondary batteries 63 forming the power storage blocks 60A to 60C by a current integration method described later, and the voltage of each of the secondary batteries 63 forming the power storage blocks 60A to 60C. Is performed. The individual management units 77 </ b> A to 77 </ b> C perform a process of inspecting the secondary battery 63 for a short circuit. Each of the individual management units 77A to 77C has a storage unit, and data necessary for executing each of the above-described processes is stored in advance.

  The integrated management unit 100 is communicably connected to the individual management units 77A to 77C of the power storage blocks 60A to 60C. The integrated management unit 100 monitors the entire power storage system 10 based on various data transmitted from the individual management units 77A to 77C of the power storage blocks 60A to 60C.

2. Characteristics of Secondary Battery The secondary battery 63 may be an iron phosphate-based lithium ion battery using lithium iron phosphate (LiFePO ₄ ) as a positive electrode active material and graphite as a negative electrode active material.

  FIG. 4 is an SOC-OCV correlation graph in which the horizontal axis is SOC [%] and the vertical axis is OCV [V]. The SOC-OCV correlation graph is an example of the SOC-OCV characteristics of the present invention. The SOC (state of charge) is a ratio of the remaining capacity Cr to the actual capacity (available capacity) Ca of the secondary battery 63, as shown in (1) below. The actual capacity Ca is a capacity that allows the secondary battery 63 to be taken out from a fully charged state, that is, a full charge capacity.

  SOC = Cr / Ca × 100 (1)

  OCV (open circuit voltage) is an open voltage of the secondary battery 63. The open-circuit voltage of the secondary battery 63 can be detected by measuring the voltage of the secondary battery 63 in a state where no current or no current is considered.

  As shown in FIG. 4, the secondary battery (for example, a phosphorous iron-based lithium ion battery) 63 has a plurality of regions in which the amount of change in OCV with respect to the amount of change in SOC is different. More specifically, it has five change regions L1 to L5.

  As shown in FIG. 4, the change region L1 is located in the range of 8% to less than 31% in SOC. The change region L2 is located in a range of 31 [%] to less than 62 [%] in SOC. The change region L3 is in the range of 62 [%] to less than 68 [%] in SOC. The change region L4 is located in a range of 68 [%] to less than 97 [%] in SOC value. The change region L5 is a range of 97% or more in SOC. If the SOC is less than 8%, the area is out of the usable range.

  The change region L2 is a substantially constant plateau region where the change amount of the OCV with respect to the change amount of the SOC is very small and the OCV is about 3.3 [V]. The change region L4 also has a substantially constant plateau region with an OCV of about 3.34 [V]. The plateau region is a region where the graph (curve) is flat, specifically, a region where the variation of the OCV with respect to the variation of the SOC is 2 [mV /%] or less.

  The change region L5 is a region where the change amount of the OCV with respect to the change amount of the SOC is higher than the predetermined value X. The predetermined value X is a numerical value determined by a relationship with the inspection accuracy of the minute short circuit (current value of the minute short circuit to be detected, etc.), and is, for example, 35 [mV /%].

3. Inspection method of minute short circuit If a part of the separator that separates the positive electrode and the negative electrode of the secondary battery 63 is damaged, the positive electrode and the negative electrode may be short-circuited inside the battery (hereinafter, short-circuit). The micro short circuit can be inspected at the time of shipping the battery, but may occur even after the shipping due to lithium deposition and the like accompanying the charging at a low temperature. Hereinafter, a method for inspecting a minute short circuit of the secondary battery 63 after the operation of the power storage system 50 starts will be described.

  FIG. 5 is a flowchart showing a flow of the inspection process for a micro short circuit. The inspection process for a micro short-circuit includes 12 steps of S10 to S120, and is periodically executed every time a predetermined period elapses. Prior to the start of the inspection process for a micro short circuit, the switches 65A to 65C are all in the ON state, and the power storage blocks 60A to 60C are connected to the common line Lo.

  When the inspection process for a micro short circuit starts, a command is given from the integrated management unit 100 to the individual management unit 77A of the power storage block 60A that is the first inspection target. The individual management unit 77A performs a process of determining whether the secondary battery 63 of the power storage block 60A is in the change area L5 (S10). This determination can be made based on the SOC value of the secondary battery 63.

  When the AC power supply is normal, the power storage system 50 of the UPS 10 is controlled by the charge control circuit 41 to maintain full charge. Therefore, when the AC power supply is normal, it is usually determined that the secondary battery 63 is in the change area L5 in each of the power storage blocks 60A to 60C (S10: YES).

  On the other hand, when power is supplied from the power storage system 50 to the load via the diode 45 and the inverter 30 such as when the AC power supply is abnormal (for example, during a power failure), each of the power storage blocks 60A to 60C has a capacity higher than the fully charged state. The state is lowered. When the secondary battery 63 is in the other change areas L1 to L4, the integrated management unit 100 sends a command to the charge control circuit 41 after the restoration of the AC power. According to the command, the secondary batteries 63 of the respective power storage blocks 60A to 60C are charged so as to be included in the change area L5 (S20).

  When it is determined that the secondary battery 63 is in the change area L5 or when the above-described charging control is performed, the integrated management unit 100 performs a small short-circuit test on the individual management unit 77A of the first power storage block 60A. Is transmitted (S30).

  Upon receiving the execution command from the integrated management unit 100, the individual management unit 77A executes an equalization process for equalizing the voltage of the secondary battery 63 (S40). In the equalization process of the secondary battery 63, the discharge circuit 71 discharges the high-voltage secondary battery 63 in accordance with the low-voltage secondary battery.

  When the equalization process is completed, the individual management unit 77A sends a switch-off command to the switch 65A. As a result, the switch 65A is switched from on to off, so that the storage block 60A to be inspected is disconnected from the common line Lo, is cut off, and enters a no-current state (S50).

  Next, the individual management unit 77A sends a command to the sensor unit 75A, and executes a process of measuring the voltage of each secondary battery 63 included in the power storage block 60A in the change area L5 (S60).

  When a predetermined time T has elapsed from the first voltage measurement (S70), the individual management unit 77A sends a command to the sensor unit 75A to execute a process of measuring the voltage of each secondary battery 63 included in the power storage block 60A. (S80). The predetermined time T is, for example, 24 hours.

  After that, the individual management unit 77A determines whether or not each of the secondary batteries 63 included in the power storage block 60A has a micro short circuit (S90). Specifically, the voltage difference ΔV is calculated for each secondary battery 63 by comparing the voltages V1 and V2 before and after the lapse of the predetermined time T.

ΔV = V1−V2 (2)
V1 is the voltage of each secondary battery 63 measured in S60, and V2 is the voltage of each secondary battery 63 measured in S80. ΔV is a voltage difference between the voltages V1 and V2 of the same secondary battery 63 before and after the predetermined time T has elapsed.

  After calculating the voltage difference ΔT, the individual management unit 77A compares the voltage difference ΔT with a threshold value, determines that the voltage difference ΔV is smaller than the threshold value, and determines that the voltage difference ΔV is not short-circuited. It is determined that there is. The threshold value is, for example, 10 mV.

  For example, when a minute short circuit of 1 mAh has occurred, the capacity reduction in 24 hours is 24 mAh. Assuming that the actual capacity of the cell is 2 Ah, 24 mAh is approximately 1% when converted to SOC. In the change region L5, the voltage change per 1% is 35 mV or more. Therefore, the voltage difference ΔV exceeds the threshold value 10 mV. As described above, in this example, at least a minute short circuit of 1 mAh can be detected.

  The individual management unit 77A determines that all of the secondary batteries 63 included in the power storage block 60A are normal when there is no short circuit (S90: YES). If the individual management unit 77A determines that it is normal, it sends an “ON” switching command to the switch 65A. As a result, the switch 65A switches from off to on, so the power storage block 60A disconnected in S50 is connected again to the common line Lo (S100).

  After the switch 65A is switched, the individual management unit 77A notifies the integrated management unit 100 that the power storage block 60A is "normal". Upon receiving the notification of “normal” from the individual management unit 77A, the integrated management unit 100 determines whether the inspection has been completed for all the power storage blocks 60A to 60C (S110).

  At this stage, only the first power storage block 60A has been tested, and the second power storage block 60B and the third power storage block 60C have not been tested. Therefore, NO is determined in S110.

  Thereafter, the process returns to S10, and a command is given from the integrated management unit 100 to the individual management unit 77B of the power storage block 60B to be inspected, and the individual management unit 77B changes the secondary battery 63 of the power storage block 60B. A process is performed to determine whether or not the area L5 exists.

  When it is determined that the secondary battery 63 of the power storage block 60B is located in the change area L5, the integrated management unit 100 instructs the individual management unit 77B of the second power storage block 60B to execute a micro short-circuit inspection. Is transmitted (S30).

  Upon receiving the execution command from the integrated management unit 100, the individual management unit 77B executes an equalization process for equalizing the voltage of the secondary battery 63 (S40).

  When the equalization process is completed, the individual management unit 77B sends a switch-off command to the switch 65B. As a result, the switch 65B is switched from on to off, so that the power storage block 60B to be inspected is disconnected from the common line Lo and enters a no-current state (S50). Then, similarly to the case of the first power storage block 60A, the processing of S60 to S90 is executed, and the presence or absence of a minute short circuit is inspected for each of the secondary batteries 63 constituting the power storage block 60B.

  In this manner, the storage blocks 60A to 60C to be inspected are separated one by one from the common line Lo, and the presence or absence of a micro short circuit is inspected. If there is no minute short-circuit of the secondary battery 63 in each of the power storage blocks 60A to 60C, the inspection is completed for all the power storage blocks 60A to 60C, a YES determination is made in S110, and the entire process ends.

  On the other hand, when it is determined that there is a minute short circuit in a part of the secondary battery 63 (S90: N0), the power storage block 60 to be inspected is instructed from the individual management unit 77 that has detected the minute short circuit to the integrated management unit 100. You will be notified that there is a short circuit. Upon receiving the notification, the integrated management unit 100 performs an error display, such as prompting replacement of the power storage block 60 to be inspected (S120).

4. Description of Effect Since the power storage block 60 to be inspected is separated from the common line Lo, a voltage change caused by a minute short circuit can be accurately detected. For this reason, it is possible to accurately inspect a micro short circuit. Moreover, since only the power storage block 60 to be inspected is disconnected, even during the inspection, the other power storage blocks 60 are connected to the common line Lo and can supply power to the load. That is, in this configuration, a minute short circuit of the secondary battery 63 can be detected with high accuracy without putting the entire power storage system 50 into a no-current state (without stopping the UPS 10).

  After the power storage blocks 60A to 60C to be inspected are separated, the voltage of the secondary battery 63 is detected in the change area L5, and a minute short circuit is inspected based on the detected voltage. The change area L5 is a high change area in which the change amount of the OCV with respect to the change amount of the SOC is higher than the predetermined value X. Since the change amount of the OCV with respect to the change amount of the SOC is large, a minute short circuit of the secondary battery 63 is accurately inspected. You can do it.

  The determination of the micro short circuit is performed based on the voltage difference ΔV before and after the lapse of the predetermined time T for the same secondary battery 63. Since this method compares the voltages of the same secondary batteries 63, if there is no change or a small change in the environmental temperature or the like, it is possible to accurately detect a voltage change caused by a minute short circuit. Therefore, a minute short circuit of the secondary battery 63 can be accurately inspected.

  When the power storage block 60 is disconnected, the voltage of each secondary battery 63 is equalized, and a minute short circuit can be detected for each secondary battery 63 under the same conditions. Therefore, a minute short circuit of the secondary battery 63 can be accurately inspected. Further, there is a merit that the voltage can be equalized in addition to the inspection of the minute short circuit.

<Embodiment 2>
Next, a second embodiment of the present invention will be described.
The individual management units 77A to 77C constantly perform the process of estimating the SOC of each secondary battery 63 in each of the power storage blocks 60A to 60C. The SOC can be estimated from the initial value of the SOC and the cumulative integrated value of the current I detected by the current sensors 67A to 67C, as shown by the following equation (3) (current integrating method). The sign of the current is plus when charging and minus when discharging.

SOC = SOCo + 100 × ∫Idt / Co (3)
SOCo is the initial value of SOC, I is the current, and Co is the initial value of the full charge capacity.

  In the current integration method, measurement errors of the current sensors 67A to 67C accumulate. Therefore, when inspecting a minute short circuit of the secondary battery 63, a process of correcting the SOC by the current integration method is performed.

  For example, when performing an inspection for a minute short circuit for the first power storage block 60A, the individual management unit 77A switches the switch 65A from ON to OFF in S50, and disconnects the power storage block 60A from the common line Lo.

  Next, in step S60, the individual management unit 77A sends a command to the sensor unit 75A, and executes a process of measuring the voltage of each secondary battery 63 included in the power storage block 60A, that is, the OCV, in the change area L5. When the predetermined time T has elapsed from the first voltage measurement (S70), the individual management unit 77A sends a command to the sensor unit 75A to measure the voltage of each secondary battery 63 constituting the power storage block 60A, that is, the OCV. Is executed (S80).

  After the second voltage measurement in S80, the individual management unit 77A refers to the SOC-OCV correlation graph shown in FIG. 4 of the OCV measurement value of each secondary battery 63, and thereby the SOC of each secondary battery 63 Is estimated (OCV method). For example, when the measured value of the OCV is “OCV1”, the SOC of the secondary battery can be estimated to be “SOC1”.

  After the estimation of the SOC, the SOC obtained by the OCV method is used as an initial value to estimate the SOC by the current integration method. By doing so, the SOC by the current integration method can be corrected. In this method, the SOC can be corrected together with the inspection for the minute short circuit of the secondary battery 63. Further, since the SOC is corrected in a state where the power storage blocks 60A to 60C are separated, that is, in a no-current state, the SOC can be corrected with high accuracy. The individual management units 77A to 77C correspond to “correction units” of the present invention.

<Other embodiments>
The present invention is not limited to the embodiments described above.

  (1) In the first embodiment, the power storage system 50 is applied to the UPS. The power storage system 50 is not limited to the UPS, and may be applied to other uses such as a solar power generation system.

  (2) In the first embodiment, the predetermined value X is set to 35 [mV /%], and an inspection for a minute short circuit is performed in the change region L5. The predetermined value X has a trade-off relationship with the inspection accuracy, and can be appropriately set according to the required inspection accuracy. The predetermined value X may be at least 10 [mV /%] or more, and a minute short-circuit test can be performed in the change region L3 in addition to the change region L5.

  As shown in FIG. 4, the slope of the graph of the iron phosphate lithium ion secondary battery 63 becomes steeper as it approaches full charge (SOC = 100%) even in the change region L5. The greater the slope of the graph (the higher the amount of change in OCV with respect to the amount of change in SOC), the higher the accuracy of inspection for a micro short circuit. The optimal value of the predetermined value X is 100 [mV /%], and in the change region L5, a region where the change amount of the OCV with respect to the change amount of the SOC exceeds 100 [mV /%] (the region where the SOC is 98% or more). ) May be tested for a micro short circuit.

  (3) In the first embodiment, the iron phosphate lithium ion secondary battery 63 has been exemplified. Alternatively, the power storage element may be, for example, a ternary lithium ion secondary battery using a lithium-containing metal oxide containing Co, Mn, and Ni elements for the positive electrode active material and hard carbon for the negative electrode. The storage element may be another secondary battery or capacitor. FIG. 6 is an SOC-OCV correlation graph of a ternary lithium ion secondary battery. In a ternary lithium-ion secondary battery, the change in OCV with respect to the change in SOC is generally 10 [mV /%] or more when the SOC is in a range of 30% or less. Therefore, it is preferable to perform the inspection for the minute short circuit in the range where the SOC is 30% or less.

  (4) In the first embodiment, the plurality of secondary battery cells 63 are connected in series. Alternatively, the secondary battery 63 may be a single cell.

  (5) In the first embodiment, after the switch 65 is switched, the voltage of each secondary battery 63 is measured before and after a predetermined time T has elapsed. With respect to the same secondary battery 63, the presence or absence of a micro short circuit was detected by obtaining the voltage difference ΔV before and after the lapse of a predetermined time and comparing it with a threshold value. Alternatively, the voltage difference ΔV before and after the lapse of a predetermined time is obtained for all the secondary batteries 63 constituting the power storage block 60 to be inspected, and the average value may be calculated. For each secondary battery 63, the voltage difference ΔV before and after the elapse of the predetermined time is compared with the average value of the voltage differences ΔV of all the secondary batteries 63. As a result of the comparison, if a voltage drop equal to or more than the threshold value has occurred, it may be determined that there is a minute short circuit, and if no voltage drop has occurred, it may be determined that there is no minute short circuit. With this configuration, even if there is a change in the environmental temperature, a minute short circuit of the secondary battery 63 can be inspected with high accuracy.

  (6) In the first embodiment, after the switch 65 is switched, the voltage of each secondary battery 63 is measured before and after the predetermined time T has elapsed. With respect to the same secondary battery 63, the presence or absence of a micro short circuit was detected by obtaining the voltage difference ΔV before and after the lapse of a predetermined time and comparing it with a threshold value. Alternatively, when a predetermined time T has elapsed after the switch 65 was switched, the presence or absence of a micro short circuit may be detected by obtaining a voltage difference between the respective secondary batteries and comparing the voltage difference with a threshold value. After the switch 65 is switched, when a predetermined time T has elapsed, the presence or absence of a micro short circuit may be detected by comparing the voltage of each secondary battery 63 with a threshold.

  (7) In the first embodiment, the storage blocks 60A to 60C to be inspected are separated one by one, and the storage blocks 60A to 60C are inspected for minute short circuits. The inspection for the micro short circuit may be performed without stopping the power storage system 50. For example, the two power storage blocks 60A and 60B are simultaneously disconnected to perform the inspection for the micro short circuit, and during that time, the power storage block 60C is connected to the load. Power may be supplied.

  (8) In the first embodiment, the power storage blocks 60A to 60C are sequentially disconnected from the common line Lo by sequentially sending the execution command of the inspection of the micro short circuit from the integrated management unit 100 to each of the individual management units 77A to 77C. An inspection for a micro short circuit was performed. The integrated management unit 100 is not always necessary, and the individual management units 77A to 77C may communicate necessary information such as an inspection status, and may perform an inspection for a micro short circuit in order.

  (9) In the first embodiment, the charge control circuit 41 that controls charging of the power storage system is provided. Alternatively, the charge control circuit 41 may be replaced with a semiconductor switch or the like, and the charge to the power storage system may be controlled by controlling the ON / OFF of the semiconductor switch.

10 UPS
Reference Signs List 50 power storage system 60A to 60C power storage block 65A to 65C switch 71 discharge circuit 77A to 77C individual management unit (corresponding to "inspection unit" and "correction unit")
100 Integrated management unit Lo Common line La-Lc Parallel line

Claims (10)

A power storage system including a plurality of power storage blocks connected to a common line in parallel by parallel lines,
Each of the power storage blocks,
A plurality of power storage elements connected in series,
A switch provided on the parallel line,
The power storage system further includes an inspection unit that disconnects the plurality of power storage elements of the power storage block from the common line by switching the switch from on to off, and tests a micro short circuit in the plurality of power storage elements. system. The power storage system according to claim 1,
A power storage system that switches the switches from on to off one by one, disconnects the storage blocks to be tested one by one, and tests for a micro short circuit of the storage element. The power storage system according to claim 1 or 2,
The power storage system, wherein the inspection unit inspects a minute short circuit of the power storage element based on a voltage of the power storage element after a predetermined time has elapsed since the switch was turned off. The power storage system according to any one of claims 1 to 3, wherein
The power storage system, wherein the inspection unit inspects a micro short circuit of the power storage element based on a voltage difference before and after a lapse of a predetermined time of the power storage element. The power storage system according to any one of claims 1 to 3, wherein
The inspection unit is configured to compare a voltage difference before and after a predetermined time of the power storage element with an average value of the voltage differences before and after the predetermined time of all the power storage elements included in the power storage block, based on a result of the comparison. A power storage system that checks for short circuits. The power storage system according to any one of claims 1 to 5, wherein
The power storage element has a high change region in which the change amount of OCV with respect to the change amount of SOC is higher than a predetermined value in the SOC-OCV characteristic,
The inspection unit, after separating the storage block to be inspected,
A power storage system that detects a voltage of the power storage element in the high change region and inspects a minute short circuit based on the detected voltage. The power storage system according to claim 6,
A power storage system further comprising a correction unit that corrects the SOC of the power storage element based on the voltage of the power storage element detected in the high change region. The power storage system according to claim 6 or 7, wherein
The power storage block,
Including an equalizing circuit provided for each of the plurality of power storage elements connected in series,
In the high change area, the inspection unit operates the equalization circuit to equalize the voltages of the plurality of power storage elements, and then switches off the switch to disconnect the power storage block to be inspected. system. The power storage system according to claim 1, wherein:
The power storage system, wherein the power storage element is a lithium ion secondary battery having a flat plateau region in SOC-OCV characteristics. Switching a switch provided on a parallel line connecting a plurality of power storage blocks in parallel from on to off to disconnect a predetermined power storage block from the common line;
A method for inspecting a short circuit in a plurality of power storage elements included in the separated power storage block while continuing operation of the power storage system.

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