Cell voltage abnormality detection method and storage battery system

Abstract

To provide a cell voltage abnormality detection method with which it is possible to detect the abnormality of a cell voltage before a voltage change that actuates an abnormality detection function occurs in a storage battery system and discriminate whether the cause of the cell voltage abnormality is the cell voltage itself or a measurement circuit.SOLUTION: Provided is an abnormality detection method for a storage battery system that is formed including one or a plurality of cells interconnected in series and a measurement circuit for measuring the end-to-end voltage of the cell. This method includes: a voltage measurement step for measuring the end-to-end voltage of one or each of the cells by the measurement circuit and measuring the output voltage of the entire storage battery system; a computation step for calculating the difference between the output voltage of the entire storage battery system and the sum total of end-to-end voltages of one or each of the cells; and a comparative determination step for determining that abnormality has occurred in the measurement circuit when it is determined that the difference is on the order of a prescribed level.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for detecting an abnormality in a cell voltage and a storage battery system. [Background technology]

[0002] Conventionally, a technique for detecting a break in an electric wire connecting each of a plurality of unit cells (such as a unit battery) and a cell monitoring device (such as a voltage measurement circuit) is known. In a cell monitoring device of a power storage module having this technique, a cell monitoring unit turns a plurality of switches connected in parallel to each of a plurality of cells via voltage measurement lines from off to on and then back off in a predetermined order. Then, the cell voltage of each cell is measured between a pair of voltage measurement lines connected to each cell after the switch connected in parallel to the cell is turned off again and after the next switch in the order is turned on. Then, when it is determined that at least one of a high abnormal cell voltage that is equal to or higher than a first threshold and a low abnormal cell voltage that is equal to or lower than a second threshold that is lower than the first threshold is present among the measured cell voltages, it is detected that the voltage measurement line is broken (for example, see Patent Document 1).

[0003] Also known is a DC power supply device for vehicles that has a diagnostic function for diagnosing an abnormality in a measurement circuit for the terminal voltage of a lithium battery cell. This DC power supply device includes a plurality of lithium battery cells connected in series, a measurement circuit for measuring the terminal voltage of each battery cell, a plurality of detection harnesses connecting the measurement circuit to the terminals of each battery cell, a plurality of series circuits having resistors and balancing switches for passing a discharge current of the battery cells, a control circuit for controlling the balancing switches, and a diagnostic circuit having a comparison circuit, and each of the series circuits is connected in parallel to each battery cell via the detection harness, the control circuit turns on the balancing switch, the measurement circuit measures the terminal voltage of the battery cell supplied via the detection harness, and the comparison circuit compares the measured terminal voltage with a predetermined threshold to determine an abnormal state in the diagnostic circuit (see, for example, Patent Document 2).

[0004] In the above invention, when detecting an abnormality in the voltage of multiple cells connected in series (the "battery cells" shown in Patent Document 2 are also simply called "cells"), if the cell voltage of one cell differs significantly from the cell voltages of the other cells or from the design voltage value, the abnormality detection function is activated. In devices such as those shown in Patent Documents 1 and 2, it is necessary to generate a voltage change that will activate the abnormality detection function. At present, it is difficult to detect a voltage abnormality unless a voltage change that will activate the abnormality detection function occurs.

[0005] Furthermore, there are two main possible causes for abnormalities in measured cell voltages, such as a sudden drop in the measured cell voltage. The first is that abnormalities occur in the cell voltage itself due to daily charging and discharging operations. The second is that the cell voltage itself is normal, but an abnormality occurs in the measurement circuit (hereinafter referred to as the "measurement circuit"), such as poor contact in a connector. Currently, when an abnormality occurs in the measured cell voltage, it is difficult to determine whether the cause is the cell voltage itself or the measurement circuit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2013-011596 A [Patent Document 2] JP 2009-089488 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above-mentioned problems, and has as its ultimate objective the provision of technology that makes it possible to detect abnormalities in cell voltages in a battery storage system even if no voltage change occurs that would activate the abnormality detection function, and that makes it possible to determine whether the cause of the cell voltage abnormality is the cell voltage itself or the measurement circuit, thereby making it possible to detect abnormalities in cell voltages more easily or more accurately. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides: A method for detecting an abnormality in a storage battery system including one or a plurality of cells connected in series, comprising: the battery system includes a measurement circuit for measuring a voltage across one or each of the cells; a voltage measurement step of measuring the voltage across one or each of the cells by the measurement circuit and measuring an output voltage of the entire storage battery system; A calculation step of calculating a difference between a sum of the voltages across one or each of the cells and an output voltage of the entire storage battery system; and a comparison and determination step of determining that an abnormality has occurred in the measurement circuit when the difference is equal to or greater than a predetermined level.

[0009] According to the present invention, when an abnormality occurs in the measurement circuit of a storage battery system, it is possible to accurately determine that the abnormality has occurred, without checking the cell voltage of one or each cell, and this can lead to improving the function of the measurement circuit. The steps included in the cell voltage abnormality detection method of the present invention are simple, and when an abnormality occurs in the measurement circuit, it is easy to grasp the abnormality.

[0010] The present invention may also be a method for detecting an abnormality in cell voltages, characterized in that the difference is a voltage difference between the total value of the voltages across both ends and the output voltage, and in the comparing and judging step, it is judged that an abnormality has occurred in the measurement circuit when the voltage difference is equal to or greater than a predetermined threshold value. With this, when an abnormality has occurred in the measurement circuit of the storage battery system, it is possible to simply and accurately judge that the abnormality has occurred based on the difference between the total value of the voltages across both ends and the output voltage.

[0011] In addition, the present invention may be a method for detecting an abnormality in a cell voltage, characterized in that the predetermined threshold value is a value obtained by multiplying the voltage across both ends of one of the cells by a predetermined ratio. This makes it possible to easily set the predetermined threshold value.

[0012] In addition, the present invention may be a method for detecting an abnormality in a cell voltage, further comprising a step of issuing a notification that an abnormality has occurred in the measurement circuit when the voltage difference is equal to or greater than the predetermined threshold value in the comparison and determination step. In this way, it is possible to grasp by some means that an abnormality has occurred in the measurement circuit.

[0013] The present invention may also be a method for detecting an abnormality in cell voltage, further comprising an abnormality determination step of determining whether the voltage across at least one of the cells is abnormal, and when the comparison step determines that the voltage difference is less than the predetermined threshold, and when the abnormality determination step determines that the difference between the voltage across any one of the cells and a reference voltage is equal to or greater than a second predetermined threshold, the method determines that the voltage across any one of the cells is abnormal. According to this, in addition to determining whether an abnormality has occurred in the measurement circuit, it is possible to determine whether the voltage across any one of the cells is abnormal, making it possible to determine whether the cause of the cell voltage abnormality is the cell voltage itself or the measurement circuit. Also, in the abnormality detection step, It is also possible to detect an abnormality in the cell voltage without causing a voltage change that activates the function. The content of the abnormality may be, for example, a cell balance abnormality.

[0014] In addition, the present invention may also be a cell voltage abnormality detection method further comprising a second reporting step of reporting that an abnormality has occurred in the voltage across the arbitrary one of the cells when the voltage difference is less than the predetermined threshold value in the comparison and judgment step and when the voltage across the arbitrary one of the cells is judged to be abnormal in the abnormality judgment step. According to this, it is possible to grasp by some means that an abnormality has occurred in the voltage across the arbitrary one of the cells.

[0015] In addition, in the present invention, A storage battery system including one or more cells connected in series, a measurement circuit connected to one or each of the cells for measuring a voltage across the cell; A calculation unit that measures the voltage across one or each of the cells and an overall output voltage, and calculates a difference between the total value of the voltage across one or each of the cells and the output voltage; The storage battery system may further include a comparison and determination unit that determines that an abnormality has occurred in the measurement circuit when the difference is equal to or greater than a predetermined level.

[0016] According to the present invention, when an abnormality occurs in the measurement circuit of the battery storage system, it is possible to accurately determine that the abnormality has occurred and to improve the function of the measurement circuit without checking the cell voltage of one or each cell. The system configuration of the battery storage system in the present invention is simple, and when an abnormality occurs in the measurement circuit, it is easy to grasp the abnormality.

[0017] In addition, the present invention may be a storage battery system, characterized in that the difference is a voltage difference between the sum of the voltages at both ends and the output voltage, and the comparison and determination unit determines that an abnormality has occurred in the measurement circuit when the voltage difference is equal to or greater than a predetermined threshold. According to this, when an abnormality has occurred in the measurement circuit of the storage battery system, the comparison and determination unit can simply and accurately determine that the abnormality has occurred based on the difference between the sum of the voltages at both ends and the output voltage.

[0018] In addition, in the present invention, the storage battery system may be characterized in that the predetermined threshold value is a value obtained by multiplying the voltage across both ends of one of the cells by a predetermined ratio, which makes it possible to easily set the predetermined threshold value in the comparison and determination unit.

[0019] In addition, the present invention may be a storage battery system further comprising a second comparison and judgment unit that judges whether the voltage across at least one of the cells is abnormal, and when the voltage difference is less than the predetermined threshold and the second comparison and judgment unit judges that the voltage across the arbitrary cell is abnormal when the difference between the voltage across the arbitrary cell and a reference voltage is equal to or greater than a second predetermined threshold. In this way, in addition to judging whether an abnormality occurs in the measurement circuit, it is possible to judge whether the voltage across the arbitrary cell is abnormal, so that it is possible to judge whether the cause of the cell voltage abnormality is the cell voltage itself or the measurement circuit. It is also possible to detect an abnormality in the cell voltage without causing a voltage change that would activate the abnormality detection function.

[0020] In addition, in the present invention, the comparison and judgment unit issues a report that an abnormality has occurred in the measurement circuit when the voltage difference is equal to or greater than the predetermined threshold value, or when the comparison and judgment unit determines that the voltage difference is less than the predetermined threshold value and the second comparison and judgment unit determines that the difference between the voltage across any one cell and a reference voltage is equal to or greater than a predetermined second threshold value. Alternatively, the storage battery system may further include an alarm means for alarming that an abnormality has occurred in the voltage across any one of the cells, whereby it is possible to grasp, by some means, that an abnormality has occurred in the measurement circuit or in the voltage across any one of the cells.

[0021] Furthermore, the present invention may provide a power supply system including the storage battery system described above, further including a solar power generation module and a power converter, wherein the power converter includes a control unit that controls DC power supplied to a power bus, a first converter that converts the voltage of DC power generated by the solar power generation module based on a control command from the control unit regarding maximum power point tracking control and supplies the voltage to the power bus, a second converter connected to the power bus and converts the voltage of the DC power supplied to the power bus based on a charge / discharge control command from the control unit regarding charge / discharge control and charges the storage battery system, or converts the voltage of DC power discharged from the storage battery system and supplies the voltage to the power bus, and a power conversion unit that converts DC current supplied through the power bus from both the storage battery system and the solar power generation module into AC current and supplies power to a load.

[0022] According to this, the first converter and the second converter can be controlled so that, with regard to the DC power supplied to the power bus, the power stored in the battery system is given priority for output. Also, since the DC power supplied from the battery system to the power bus can be given priority for supply to the load, it is possible to prevent overcharging of the battery system due to minute power flowing through the power bus in the charging direction during independent operation.

[0023] The above means for solving the problems can be used in combination with each other whenever possible. Effect of the Invention

[0024] According to the present invention, in a storage battery system, it is possible to more easily detect a cell voltage abnormality and to more accurately determine the cause of the cell voltage abnormality compared to the conventional technology. That is, it is possible to detect a cell voltage abnormality even when no voltage change that can be detected as a cell balance abnormality occurs, and it is possible to determine whether the cause of the cell voltage abnormality is the cell voltage itself or the measurement circuit. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a functional block diagram illustrating an example of a distributed power supply system formed including a storage battery system according to a first embodiment. [Diagram 2] FIG. 2 is a functional block diagram illustrating an example of the storage battery system according to the first embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing an example of a method for determining whether the measured cell voltage value is normal or abnormal in the first embodiment. [Figure 4] FIG. 4 is a flowchart showing the steps of the method for detecting an abnormality in a cell voltage in the first embodiment. [Diagram 5] FIG. 5 is a flowchart showing the procedure of a method for detecting an abnormality in a cell voltage in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] [Application example] The method for detecting an abnormality in cell voltage in this application example includes a step of measuring the cell voltage of each of a plurality of cells included in a storage battery unit as well as an output voltage of the entire storage battery system, a step of calculating a voltage difference between the output voltage and a sum value of the cell voltages of the plurality of cells, and a step of calculating a voltage difference between the voltage difference and a predetermined and determining that an abnormality has occurred in the measurement circuit included in the storage battery unit when it is determined that the voltage difference is equal to or greater than the predetermined threshold. The storage battery unit is a component of the storage battery system.

[0027] Fig. 1 is a functional block diagram showing an example of a distributed power system 2 formed including a storage battery system 1 to which the present invention can be applied. The distributed power system 2 in this application example is a hybrid power system including the storage battery system 1 and a solar power generation system (a solar power generation module 21+a DC / DC converter 22). The configuration of the storage battery system 1 in this application example will be described in detail with reference to Fig. 2 below.

[0028] As shown in FIG. 1, the distributed power supply system 2 includes a storage battery system 1, a photovoltaic power generation module 21, and a PCS (Power Conditioning System) 3. The PCS 3 includes a control unit 31, a power conversion unit 32, a DC / DC converter 22, and a bidirectional DC / DC converter 23. The DC / DC converter 22 of the PCS 3 is connected to the photovoltaic power generation module 21. The bidirectional DC / DC converter 23 of the PCS 3 is connected to the storage battery system 1. The DC / DC converter 22 is a unit for boosting the DC power generated by the photovoltaic power generation module 21 and supplying it to a DC bus 24. The bidirectional DC / DC converter 23 is a unit for bidirectionally converting the voltage of the power supplied through the DC bus 24 to be charged to the storage battery system 1 and the voltage of the discharge power output from the storage battery system 1 to the DC bus 24. The DC / DC converter 22 and the bidirectional DC / DC converter 23 are connected by the DC bus 24. The power conversion unit 32 of the PCS 3 is connected to the DC bus 24, and converts DC power supplied through the DC bus 24 into AC power synchronized with a power system (not shown), and also converts AC power supplied from the power system into DC power and outputs it to the DC bus 24. Here, the distributed power system 2 corresponds to the power supply system in the present invention. Also, the DC / DC converter 22 and the bidirectional DC / DC converter 23 correspond to the first converter and the second converter in the present invention. Also, the PCS 3 corresponds to the power converter in the present invention.

[0029] The control unit 31 of the PCS 3 receives the outputs of various sensors, including a power sensor 25 (current sensor+voltage sensor) provided on the DC bus 24, and a power sensor 26 (current sensor, voltage sensor) provided between the photovoltaic power generation module 21 and the DC / DC converter 22. Based on the information detected through the various sensors, the control unit 31 calculates MPPT (Maximum Power Point PT) so that the DC / DC converter 22 operates at the maximum power (value of current x voltage) point where the power output of the photovoltaic power generation module 21 is maximized or at the optimal operating point. The control unit 31 performs control processing related to charging and discharging based on the load conditions detected through the various sensors and preset charging and discharging modes. The storage battery system 1, the DC / DC converter 22, and the bidirectional DC / DC converter 23 incorporate microcomputers and the like that operate in response to control commands from the control unit 31. The distributed power system 2 is connected to a power system and a load 4 via a distribution board (not shown). The distributed power system 2 is interconnected with a power system provided, for example, on the premises of a consumer, and supplies AC power to the load 4 and the interconnected power system.

[0030] FIG. 2 is a functional block diagram showing an example of a storage battery system 1 to which the present invention can be applied. With reference to FIG. 2, the configuration of the storage battery system 1 will be described in detail. The storage battery system 1 in this application example includes a storage battery unit 5, a calculation device 6 that executes a procedure based on information acquired from the storage battery unit 5, and a display unit 7 that displays the details of an abnormality when an abnormality occurs. The calculation device 6 includes a calculation unit 61 that measures voltage and executes calculations based on the measured voltage, and a comparison and determination unit 62 and a second comparison and determination unit 63 that compare a value calculated by the calculation unit 61 with a threshold value and determine whether or not an abnormality has occurred in the storage battery unit 5. In addition, the storage battery The battery unit 5 includes measurement circuits 91-94 that are connected to each of the serially connected cells 81-84 and measure the cell voltage of each of the cells 81-84. In this application example, the cell voltage refers to the voltage across each of the cells 81-84. The display unit 7 corresponds to the alarm means in the present invention. In the following description, any one of the cells 81-84 will also be referred to as cell 8. The same applies to the measurement circuits 91-94.

[0031] The calculation unit 61 of the calculation device 6 measures the cell voltages of the cells 81-84 via the measurement circuits 91-94, and also measures the output voltage of the entire storage battery system 1 via the output circuit 51. Furthermore, the calculation unit 61 calculates the total value of the cell voltages of the cells 81-84 from each cell voltage, and calculates a voltage difference between the output voltage and the total value of the cell voltages of the cells 81-84.

[0032] A comparison / determination unit 62 of the calculation device 6 compares the voltage difference calculated by the calculation unit 61 with a predetermined threshold value that is set in advance. If the voltage difference is equal to or greater than the predetermined threshold value, it is determined that an abnormality has occurred in the measurement circuit 9. If the voltage difference is less than the predetermined threshold value, a second comparison / determination unit 63 of the calculation device 6 determines whether or not the cell voltage is abnormal.

[0033] Specifically, the second comparison / determination unit 63 compares the difference between the cell voltage of each cell 8 calculated by the calculation unit 61 and the reference voltage with a predetermined second threshold value set in advance. If the difference between the cell voltage of each cell 8 and the reference voltage is equal to or greater than the predetermined second threshold value, it is determined that an abnormality has occurred in the cell voltage of the cell 8. If it is determined that the difference between the cell voltage of each cell 8 and the reference voltage is less than the predetermined second threshold value, it is determined that no abnormality has occurred in the cell voltage. The display unit 7 displays that an abnormality has occurred in the measurement circuit 9 or that an abnormality has occurred in the cell voltage of the cell 8.

[0034] 4 is a flowchart showing the steps of a method for detecting an abnormality in a cell voltage to which the present invention can be applied. Only an outline of the flow will be described in this application example, and details will be described in the following embodiment 1.

[0035] In the method for detecting an abnormality in cell voltage in this application example, as described above, the output voltage of the entire storage battery system 1 is measured together with the cell voltages of the cells 81-84 included in the storage battery unit 5. A total value of the cell voltages of the cells 81-84 is calculated based on the measured cell voltages of the cells 81-84, and a voltage difference is further calculated based on the total value of the cell voltages and the output voltage. In addition, a difference between each cell voltage and a reference voltage set for each of the cells 81-84 is calculated for each cell 8. The calculated voltage difference is compared with a predetermined threshold, and if the voltage difference is equal to or greater than the predetermined threshold, it is determined that an abnormality has occurred in the measurement circuit 9, and a notification to that effect is issued. If the voltage difference is less than the predetermined threshold, the calculated difference between the cell voltage of each cell 8 and the reference voltage is compared with a predetermined second threshold. If the difference between the cell voltage of each cell 8 and the reference voltage is equal to or greater than the predetermined second threshold, it is determined that an abnormality has occurred in the cell voltage of the cell 8.

[0036] Example 1 Hereinafter, a cell voltage abnormality detection method and a storage battery system according to a first embodiment of the present invention will be described in more detail with reference to the drawings. Note that the cell voltage abnormality detection method and the storage battery system according to the present invention are not intended to be limited to the following configurations.

[0037] <System configuration> Returning now to the description of Fig. 1, as described above, the distributed power supply system 2 in the first embodiment is a hybrid power supply system including the storage battery system 1 as a power storage mechanism and a solar power generation system as a power generation mechanism. Other power generation systems may be adopted. Examples of other power generation systems include a power generation system using natural energy such as wind power or hydraulic power, and a private power generation system using fuel. Alternatively, the distributed power generation system 2 may be a power supply system including the storage battery system 1 without including a solar power generation system.

[0038] The control unit 31 of the PCS 3 is a unit including a processor (such as a CPU), a memory, a gate driver, a communication interface circuit, etc. The control unit 31 can detect and control abnormalities such as overvoltage and overheating of the cells 81-84 during charging and discharging of the storage battery system 1, and can suppress variations in the capacity of the cells 81-84 by maintaining cell balance.

[0039] Returning now to the explanation of Fig. 2, in the storage battery unit 5, the cells 81-84 may be, for example, secondary batteries such as lithium ion batteries or capacitors. The number of cells 8 constituting the storage battery unit 5 is not limited to four as shown in Fig. 2, and may be, for example, a single cell. When the number of cells 8 is three or more, some of the cells may be connected in parallel as long as they are connected in series.

[0040] Furthermore, all or part of the calculation unit 61, the comparison and judgment unit 62, the second comparison and judgment unit 63, and the display unit 7 may be components constituting the PCS 3. That is, after the storage battery system 1 supplies power to the PCS 3, the cell voltages of the cells 81-84 and the output voltage of the entire storage battery system 1 may be measured. The output voltage is output to, for example, a terminal block (not shown).

[0041] Furthermore, the comparison and judgment unit 62 and the second comparison and judgment unit 63 may execute procedures using the same program, or may execute procedures using separate programs. Alternatively, if the comparison and judgment unit 62 can determine abnormalities in the cell voltage in addition to determining abnormalities in the measurement circuit 9, the second comparison and judgment unit 63 is not necessary. Furthermore, the components of the storage battery system 1 may not include the display unit 7, and an abnormality in the measurement circuit 9 or cell voltage may be reported by, for example, lighting an LED or sending an email to a terminal. Alternatively, the control unit 31 may detect an abnormality in the measurement circuit 9 or cell voltage and stop the function of the storage battery unit 5.

[0042] <Judgment method> FIG. 3 is a schematic diagram showing an example of a method for determining whether the measured cell voltage value in the first embodiment is normal or abnormal. FIG. 3A shows an example of a method for determining whether the measured cell voltage value is normal. In FIG. 3A, the design values ​​of the cell voltages of the cells 81-84 are all 4.0 V, and the measured cell voltage values ​​are also all 4.0 V. The output voltage of the entire storage battery system 1 is 16.0 V. The sum of the cell voltages of the cells 81-84 is 16.0 V, which is equal to the output voltage of the entire storage battery system 1, that is, the voltage difference is 0.0 V, so the comparison and judgment unit 62 does not determine that an abnormality has occurred in the measurement circuit 9. In addition, when the design value of the cell voltage is set as the reference voltage, the cell voltage of each of the cells 81-84 matches the reference voltage, that is, the difference between the cell voltage of each of the cells 8 and the reference voltage is 0.0 V, so the second comparison and judgment unit 63 does not determine that an abnormality has occurred in the cell voltage. Here, in FIG. 3, it is assumed that the design values ​​of the cell voltages of the cells 81-84 are all the same. In addition to using the design value as the reference voltage, the average of the measured values ​​of three cells 8 other than the cell 8 being judged may be used as the reference voltage.

[0043] FIG. 3B shows an example of a method for determining if the measured cell voltages are abnormal. In FIG. 3B, the design values ​​of the cell voltages of cells 81-84 are all 4.0V, and the measured values ​​of cells 81, 82, and 84 are also 4.0V. However, because measurement circuit 93 is disconnected, the measured cell voltage of cell 83 is 0.0V. The output voltage of the entire storage battery system 1 is 16.0V. 3B, the predetermined threshold is 3.2V, which is 80% of the design value of 4.0V. In FIG. 3B, the predetermined threshold is 4.0V or less, and the voltage difference is equal to or greater than the predetermined threshold, so that the comparison and judgment unit 62 judges that an abnormality has occurred in the measurement circuit 9.

[0044] <Flowchart> Returning to the description of FIG. 4, the flow of the method for detecting an abnormality in cell voltage according to the first embodiment will be described in detail below with reference to FIG. 4. In this flowchart, first, the calculation unit 61 measures the cell voltages of the cells 81-84 included in the storage battery unit 5 as well as the output voltage of the entire storage battery system 1 (S101). Here, S101 corresponds to the voltage measurement step in the present invention. Furthermore, the calculation unit 61 calculates the total value of the cell voltages of the cells 81-84 based on the measured cell voltages of each of the cells 81-84, and further calculates a voltage difference based on the total value of the cell voltages and the output voltage. In addition, the calculation unit 61 calculates the difference between each cell voltage and a reference voltage set for each of the cells 81-84 for each cell 8 (S102). Note that in the first embodiment, the value calculated based on the total value of the cell voltages and the output voltage is not limited to the voltage difference, and may be, for example, a voltage ratio, that is, the ratio of the total value of the cell voltages to the output voltage. Here, S102 corresponds to the calculation step in the present invention. Next, the comparison and determination unit 62 compares the calculated voltage difference with a predetermined threshold value (S103), and if the voltage difference is equal to or greater than the predetermined threshold value (S103: yes), it determines that an abnormality has occurred in the measurement circuit 9 (S104). Here, S103 corresponds to the comparison and determination step in the present invention. The display unit 7 issues a notification that an abnormality has occurred in the measurement circuit 9 (S105), and the series of steps ends. An example of the mode of the notification is to display a specified error code on the display unit 7. Here, S105 corresponds to the notification step in the present invention.

[0045] If the voltage difference is less than the predetermined threshold value in the comparison and judgment unit 62 (S103: no), then the second comparison and judgment unit 63 compares the calculated difference between the cell voltage of each cell 8 and the reference voltage with a predetermined second threshold value (S106). If the difference between the cell voltage of each cell 8 and the reference voltage is equal to or greater than the predetermined second threshold value (S106: yes), it is judged that an abnormality has occurred in the cell voltage of the cell 8 (S107). The difference between the cell voltage of each cell 8 and the reference voltage may be the ratio of the cell voltage to the reference voltage of each cell 8, similar to the above-mentioned voltage difference. The predetermined second threshold value may also be a value obtained by multiplying the reference voltage (design value) by a ratio of 1 or less, similar to the above-mentioned predetermined threshold value. Here, S106 corresponds to the abnormality judgment step in the present invention. The display unit 7 issues a notice that an abnormality has occurred in the cell voltage of the cell 8 (S108), and the series of steps ends. Here, S108 also corresponds to the notice issuing step in the present invention. If the second comparison and judgment unit 63 determines that the difference between the cell voltage of each cell 8 and the reference voltage is less than a predetermined second threshold value (S106: no), it determines that no abnormality has occurred in the storage battery unit 5, and the series of steps ends.

[0046] 4, the voltage difference is compared with a predetermined threshold (S103) before the difference between the cell voltage of each cell 8 and the reference voltage is compared with a predetermined second threshold (S106). In this way, if an abnormality occurs in the measurement circuit 9, the abnormality can be quickly identified, which can lead to improvement of the function of the measurement circuit 9.

[0047] Example 2 Next, a second embodiment of the present invention will be described. The procedure of the method for detecting an abnormality in cell voltage in the first embodiment includes a flow in which the voltage difference between the total value of the cell voltages of cells 81-84 and the output voltage of the entire storage battery system 1 is compared with a predetermined threshold, and then the difference between the cell voltage of each cell 8 and a reference voltage is compared with a second predetermined threshold. The method procedure includes a step of comparing the difference between the cell voltage of each cell 8 and a reference voltage with a predetermined second threshold, and then comparing the voltage difference between the sum of the cell voltages of cells 81-84 and the output voltage of the entire storage battery system 1 with a predetermined threshold.

[0048] FIG. 5 is a flowchart showing the procedure of the cell voltage abnormality detection method in the second embodiment. Hereinafter, the method will be described with reference to FIG. 5 in comparison with the flow of the cell voltage abnormality detection method shown in FIG. 4 in the first embodiment. S109 and S110 shown in FIG. 5 are the same as S101 and S102 shown in FIG. 4, and therefore will not be described. In FIG. 4, the comparison and judgment unit 62 first obtains information from the calculation unit 61, whereas in FIG. 5, the second comparison and judgment unit 63 first obtains information from the calculation unit 61. That is, after the calculation unit 61 executes a calculation, the second comparison and judgment unit 63 compares the difference between the cell voltage of each cell 8 calculated by the calculation unit 61 and the reference voltage with a predetermined second threshold value (S111). Here, S111 corresponds to the abnormality judgment step in the present invention. When the difference between the cell voltage of each cell 8 and the reference voltage is less than the predetermined second threshold value (S111: no), the second comparison and judgment unit 63 determines that no abnormality has occurred in the storage battery unit 5, and the series of steps ends. If the difference between the cell voltage of each cell 8 and the reference voltage is equal to or greater than the second predetermined threshold (S111: yes), the comparison and judgment unit 62 then compares the voltage difference calculated by the calculation unit 61 with the predetermined threshold (S112). Here, S112 corresponds to the comparison and judgment step in the present invention. If the voltage difference is equal to or greater than the predetermined threshold (S112: yes), the comparison and judgment unit 62 judges that an abnormality has occurred in the measurement circuit 9 (S113), and then the display unit 7 issues a notice to that effect (S114), and the series of steps ends. S113 and S114 shown in FIG. 5 are the same as S104 and S105 shown in FIG. 4. If the voltage difference is less than the predetermined threshold (S112: no), the comparison and judgment unit 62 judges that an abnormality has occurred in the cell voltage of the cell 8 (S115), and then the display unit 7 issues a notice to that effect (S116), and the series of steps ends. S115 and S116 shown in FIG. 5 are the same as S107 and S108 shown in FIG.

[0049] 5, before comparing the voltage difference with the predetermined threshold value (S112), the difference between the cell voltage of each cell 8 and the reference voltage is compared with the predetermined second threshold value (S111), and if the difference between the cell voltage of each cell 8 and the reference voltage is less than the predetermined second threshold value (S111: no), the second comparison and determination unit 63 determines that no abnormality has occurred in the storage battery unit 5. This may result in a series of steps being completed more quickly than in the flowchart shown in Fig. 4. In other words, it may be possible to determine that no abnormality has occurred in the storage battery unit 5 without executing the procedure in the comparison and determination unit 62.

[0050] In the second embodiment, the functional configuration of a distributed power supply system 2 formed including the storage battery system 1 is the same as that shown in Fig. 1 of the first embodiment. Also, the functional configuration of the storage battery system 1 is the same as that shown in Fig. 2 of the first embodiment. Also, the method of determining whether the measured cell voltages of the cells 81-84 are normal or abnormal is the same as that shown in Fig. 3 of the first embodiment.

[0051] <Appendix 1> A method for detecting an abnormality in a storage battery system (1) including one or a plurality of cells (81-84) connected in series, comprising: The battery system includes a measurement circuit (91-94) for measuring a voltage across one or each of the cells, A voltage measurement process (S101, S109) of measuring the voltage across one or each of the cells by the measurement circuit and measuring the output voltage of the entire storage battery system; A calculation step (S102, S110) of calculating a difference between an output voltage of the entire storage battery system and a sum of the voltages across one or each of the cells; When it is determined that the difference is at a predetermined level, it is determined that an abnormality has occurred in the measurement circuit. and a comparison and determination step (S103, S112) of determining that the cell voltage is abnormal.

[0052] <Appendix 2> A storage battery system (1) including one or more cells (81-84) connected in series, a measurement circuit (91-94) connected to one or each of the cells for measuring the voltage across the cell; a calculation unit (61) that measures the voltage across one or each of the cells and an overall output voltage, and calculates a difference between the output voltage and a sum of the voltages across one or each of the cells; The storage battery system (1) is provided with a comparison and determination unit (62) that determines that an abnormality has occurred in the measurement circuit when the difference is at a predetermined level. [Explanation of symbols]

[0053] 1: Battery storage system 2: Distributed power systems 21: Photovoltaic power generation module 22: DC / DC converter 23: Bidirectional DC / DC converter 24: DC bus 25, 26: Power sensor 3: PCS 31: Control section 32: Power conversion section 4: Load 5: Battery unit 51: Output circuit 6: Arithmetic device 61: Arithmetic section 62: Comparison / judgment section 63: Second comparison and judgment unit 7: Display section 81-84: Cell 91-94: Measurement circuit

Claims

1. A method for detecting an abnormality in a storage battery system including one or a plurality of cells connected in series, comprising: the battery system includes a measurement circuit for measuring a voltage across one or each of the cells; a voltage measurement step of measuring the voltage across one or each of the cells by the measurement circuit and measuring an output voltage of the entire storage battery system; an abnormality determination step of determining whether or not there is an abnormality in the voltage across one or each of the cells; A calculation step of calculating a difference between a sum of the voltages at both ends of one or each of the cells and an output voltage of the entire storage battery system; a comparison and determination step of determining whether or not the difference calculated in the calculation step is equal to or greater than a predetermined first threshold value when one or more of the end-to-end voltages are determined to be abnormal in the abnormality determination step, and determining that an abnormality has occurred in the measurement circuit when the difference is equal to or greater than the first threshold value; Including, In the abnormality determination step, whether or not there is an abnormality in the voltage between one or each of the cells is determined based on whether or not the difference between the voltage between both ends of the cell and a reference voltage that is a design value of the cell is less than a predetermined second threshold value, and if the difference between the voltage between both ends of the cell and the reference voltage for any of the cells is less than the second threshold value, it is determined that there is no abnormality and the process is terminated.

13. A method for detecting an abnormality in a cell voltage, comprising:

2. The reference voltages of the plurality of cells are all set to the same value, and the first threshold value is a value obtained by multiplying the reference voltage of one of the cells by a predetermined ratio.

2. The method for detecting an abnormality in a cell voltage according to claim 1.

3. The method further includes a step of issuing a notification that an abnormality has occurred in the measurement circuit when a voltage difference between the sum of the voltages at both ends and the output voltage is equal to or greater than the first threshold value in the comparison and determination step. The method for detecting an abnormality in a cell voltage according to claim 1 or 2.

4. The method further includes a second reporting step of reporting that an abnormality has occurred in the voltage across the arbitrary cell when it is determined in the comparison and determination step that the voltage difference between the sum of the voltages across the arbitrary cell and the output voltage is less than the first threshold value and when it is determined in the abnormality determination step that the voltage across the arbitrary cell is abnormal. The method for detecting an abnormality in a cell voltage according to any one of claims 1 to 3.

5. A storage battery system including one or more cells connected in series, a measurement circuit coupled to one or each of said cells for measuring a reference voltage of said cell; a calculation unit that measures a voltage across one or each of the cells and an output voltage of the entire battery system, and calculates a difference between a sum of the voltages across one or each of the cells and an output voltage of the entire battery system; a comparison and determination unit that executes: determining whether or not there is an abnormality in the voltage across one or each of the cells; and, when it is determined that there is an abnormality in at least one of the voltages across the cells and the difference calculated by the calculation unit is equal to or greater than a predetermined first threshold, determining that an abnormality has occurred in the measurement circuit; Equipped with The comparison and determination unit determines whether or not there is an abnormality in the voltage between one or each of the cells based on whether or not the difference between the voltage between both ends of the cell and a reference voltage that is a design value of the cell is less than a predetermined second threshold value, and if the difference between the voltage between both ends of the cell and the reference voltage for any of the cells is less than the second threshold value, it determines that there is no abnormality and ends the process. A battery storage system comprising:

6. The reference voltages of the plurality of cells are all set to the same value, and the first threshold value is a value obtained by multiplying the reference voltage of one of the cells by a predetermined ratio. The battery system according to claim 5 .

7. When the voltage difference between the sum of the voltages at both ends and the output voltage is equal to or greater than the first threshold value, and the difference between the voltage at both ends of any one cell and the reference voltage is equal to or greater than the second threshold value, a notification is issued that an abnormality has occurred in the measurement circuit; and a reporting unit that reports that an abnormality has occurred in the voltage across any one of the cells when the voltage difference is less than the first threshold value and the difference between the voltage across any one of the cells and the reference voltage is equal to or greater than the second threshold value. The battery system according to claim 5 or 6.

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