JP7651987B2 - Cell voltage abnormality detection method and storage battery system - Google Patents

Description

The present invention relates to a method for detecting abnormalities in cell voltages and a storage battery system.

Conventionally, a technique for detecting a break in a wire connecting each of a plurality of unit cells (unit batteries, etc.) and a cell monitoring device (voltage measurement circuit, etc.) 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, if it is determined that at least one of a high abnormal cell voltage that is equal to or greater than a first threshold and a low abnormal cell voltage that is equal to or less than a second threshold that is smaller than the first threshold is present among the measured cell voltages, it is detected that the voltage measurement line is broken (see, for example, Patent Document 1).

A direct current power supply device for vehicles having a diagnostic function for diagnosing abnormalities in a measurement circuit for the terminal voltage of a lithium battery cell is also known. The direct current power supply device for vehicles 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 the discharge current of the battery cells, a control circuit for controlling the balancing switches, and a diagnostic circuit having a comparison circuit. Each series circuit is connected in parallel to each battery cell via the detection harness, and the control circuit turns on the balancing switch. The measurement circuit then 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).

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 voltage 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. Currently, it is difficult to detect a voltage abnormality unless a voltage change that will activate the abnormality detection function occurs.

In addition, there are two main reasons why an abnormality occurs in the measured cell voltage, such as a sudden drop in the measured cell voltage. The first is when an abnormality occurs in the cell voltage itself due to daily charging and discharging operations. The second is when the cell voltage itself is normal, but an abnormality occurs in the measurement circuit (hereinafter referred to as the "measurement circuit"), such as a poor contact in the 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.

JP 2013-011596 A JP 2009-089488 A

The present invention was made in consideration of the above 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 when no voltage change occurs that would activate the abnormality detection function, and that makes it possible to determine whether the cause of the abnormality in the cell voltage is the cell voltage itself or the measurement circuit, thereby making it possible to detect abnormalities in cell voltages more easily or accurately.

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.

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 improvements in the function of the measurement circuit. The steps involved 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.

The present invention may also be a method for detecting an abnormality in cell voltage, characterized in that the difference is a voltage difference between the total value of the voltages at both ends and the output voltage, and in the comparison and determination step, if the voltage difference is equal to or greater than a predetermined threshold, it is determined that an abnormality has occurred in the measurement circuit. With this, it is possible to simply and accurately determine that an abnormality has occurred in the measurement circuit of the storage battery system based on the difference between the total value of the voltages at both ends and the output voltage.

The present invention may also be a method for detecting an abnormality in 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.

The present invention may also 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 if the voltage difference is equal to or greater than the predetermined threshold value in the comparison and determination step. This allows the occurrence of an abnormality in the measurement circuit to be grasped by some means.

The present invention may also be a method for detecting an abnormality in a 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 voltage difference is determined to be less than the predetermined threshold value in the comparison step, and when the difference between the voltage across the cell and the reference voltage is equal to or greater than a second predetermined threshold value in the abnormality determination step, the method may determine that the voltage across the cell is abnormal. According to this method, in addition to determining whether an abnormality occurs in the measurement circuit, it is possible to determine whether the voltage across the cell is abnormal, so that it is possible to determine whether the cause of the abnormality in the cell voltage 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. The abnormality may be, for example, a cell balance abnormality.

The present invention may also be a method for detecting an abnormality in cell voltage, further comprising a second reporting step of reporting that an abnormality has occurred in the voltage across the arbitrary cell when the voltage difference is less than the predetermined threshold value in the comparison and judgment step and when the voltage across the arbitrary cell is judged to be abnormal in the abnormality judgment step. This makes it possible to grasp by some means that an abnormality has occurred in the voltage across the arbitrary cell.

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.

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 improvements in the function of the measurement circuit. The system configuration of the storage battery system in the present invention is simple, and when an abnormality occurs in the measurement circuit, it is easy to grasp the abnormality.

The present invention may also be a storage battery system characterized in that the difference is a voltage difference between the total value 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 value. In this way, when an abnormality has occurred in the measurement circuit of the storage battery system based on the difference between the total value of the voltages at both ends and the output voltage, the comparison and determination unit can simply and accurately determine that the abnormality has occurred.

The present invention may also 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. This makes it possible to easily set the predetermined threshold value in the comparison and determination unit.

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 value, and when the difference between the voltage across any one of the cells and the reference voltage is equal to or greater than a predetermined second threshold value, the second comparison and judgment unit judges that the voltage across any one of the cells is abnormal. In this way, in addition to judging whether an abnormality has occurred in the measurement circuit, it is possible to judge whether the voltage across any one of the cells is abnormal, making it 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.

In addition, the present invention may be a storage battery system characterized in that the comparison and judgment unit issues a report that an abnormality has occurred in the measurement circuit or that an abnormality has occurred in the voltage across any one of the cells when the voltage difference is equal to or greater than the predetermined threshold value, or when the comparison and judgment unit issues a report that an abnormality has occurred in the voltage across any one of the cells when the voltage difference is less than the predetermined threshold value and the second comparison and judgment unit issues a report that an abnormality has occurred in the voltage across any one of the cells. According to this, it is possible to grasp by some means that an abnormality has occurred in the measurement circuit or that an abnormality has occurred in the voltage across any one of the cells.

In addition, the present invention may also provide a power supply system including the storage battery system described above, further including a photovoltaic power generation module and a power converter, the power converter including a control unit that controls the DC power supplied to a power bus, a first converter that converts the voltage of the DC power generated by the photovoltaic power generation module based on a control command from the control unit regarding maximum power point tracking control and supplies the converted 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 the DC power discharged from the storage battery system and supplies the converted voltage to the power bus, and a power conversion unit that converts the DC current supplied through the power bus from both the storage battery system and the photovoltaic power generation module to AC current and supplies power to a load.

With this, the first converter and the second converter can be controlled so that the power stored in the battery system is given priority for output with respect to the DC power supplied to the power bus. In addition, because the DC power supplied from the battery system to the power bus can be given priority for supply to the load, overcharging of the battery system due to minute power flowing in the charging direction through the power bus during independent operation can be prevented.

The means for solving the above problems can be used in combination with each other whenever possible.

According to the present invention, in a storage battery system, it is possible to more easily detect abnormalities in cell voltages, or to more accurately determine the cause of the abnormality in cell voltages, compared to conventional techniques. In other words, it is possible to detect abnormalities in cell voltages 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 abnormality in cell voltages is the cell voltage itself or the measurement circuit.

FIG. 1 is a functional block diagram illustrating an example of a distributed power supply system formed to include a storage battery system according to a first embodiment. FIG. 2 is a functional block diagram illustrating an example of a storage battery system according to a first embodiment. 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. FIG. 4 is a flowchart showing the steps of a method for detecting an abnormality in a cell voltage in the first embodiment. FIG. 5 is a flowchart showing the steps of a method for detecting an abnormality in a cell voltage in the second embodiment.

[Application example]
The method for detecting an abnormality in cell voltage in this application example includes the steps of measuring the output voltage of the entire battery system together with the cell voltages of each of the multiple cells included in the storage battery unit, calculating a voltage difference between the output voltage and the sum of the cell voltages of the multiple cells, and comparing the voltage difference with a predetermined threshold and determining that an abnormality has occurred in a 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.

Figure 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 (solar power generation module 21 + DC/DC converter 22). The configuration of the storage battery system 1 in this application example will be described in detail in Figure 2 below.

As shown in FIG. 1, the distributed power system 2 includes a storage battery system 1, a solar 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 solar 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 solar power generation module 21 and supplying it to the 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 a DC bus 24. The power conversion unit 32 of the PCS 3 is connected to the DC bus 24 and converts the DC power supplied through the DC bus 24 into AC power synchronized with the power system (not shown), and converts the 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.

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 controls MPPT (Maximum Power Transformation) so that the DC/DC converter 22 operates at the maximum power (value of current x voltage) point where the power generation 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 a preset mode related to charging and discharging. The storage battery system 1, the DC/DC converter 22, and the bidirectional DC/DC converter 23 incorporate microcomputers and the like that operate upon receiving 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 on the premises of a consumer, for example, to supply AC power to the load 4 and the interconnected power system.

FIG. 2 is a functional block diagram showing an example of a storage battery system 1 to which the present invention can be applied. In 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 contents 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 judgment unit 62 and a second comparison and judgment unit 63 that compare a value calculated by the calculation unit 61 with a threshold value and judge whether an abnormality occurs in the storage battery unit 5. In addition, the storage battery unit 5 includes measurement circuits 91-94 that are connected to each of the cells 81-84 connected in series and measure the cell voltages of each of the cells 81-84. Here, in this application example, the cell voltage refers to the voltage across each of the cells 81-84. In addition, 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.

The calculation unit 61 of the calculation device 6 measures the cell voltage of each 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 the voltage difference between the total value of the cell voltages of the cells 81-84 and the output voltage.

The comparison and judgment 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 judged that an abnormality has occurred in the measurement circuit 9. If the voltage difference is less than the predetermined threshold value, the second comparison and judgment unit 63 of the calculation device 6 judges whether the cell voltage is abnormal or not.

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 that is 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.

Figure 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 overview of the flow is provided in this application example, and details are provided in Example 1 below.

In the cell voltage abnormality detection method in this application example, as described above, the output voltage of the entire storage battery system 1 is measured along with the cell voltages of the cells 81-84 included in the storage battery unit 5. The sum of the cell voltages of the cells 81-84 is calculated based on the measured cell voltages of each of the cells 81-84, and the voltage difference is further calculated based on the sum of the cell voltages and the output voltage. In addition, the difference between each cell voltage and the 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.

Example 1
Hereinafter, the cell voltage abnormality detection method and the storage battery system according to the 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.

<System Configuration>
Returning now to the explanation 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, but the distributed power supply system 2 may employ a power generation system other than a solar power generation system. Examples of other power generation systems include a power generation system that uses natural energy such as wind power or hydraulic power, and a private power generation system that uses fuel. Alternatively, the distributed power supply system 2 may be a power supply system that does not include a solar power generation system and includes the storage battery system 1.

The control unit 31 of the PCS3 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 when the storage battery system 1 is being charged or discharged, and can suppress variations in the capacity of the cells 81-84 by maintaining cell balance.

Now, let us return 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. Furthermore, 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. Furthermore, 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.

In addition, all or part of the calculation unit 61, the comparison/determination unit 62, the second comparison/determination unit 63, and the display unit 7 may be components that configure the PCS3. That is, after the storage battery system 1 supplies power to the PCS3, 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).

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 is capable of judging abnormalities in the cell voltage in addition to judging 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 abnormalities 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 abnormalities in the measurement circuit 9 or cell voltage and stop the function of the storage battery unit 5.

<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 cell 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 measurement values of three cells 8 other than the cell 8 being judged may be used as the reference voltage.

FIG. 3B shows an example of a method for determining if the measured cell voltage is abnormal. In FIG. 3B, the design values of the cell voltages of cells 81-84 are all 4.0 V, and the measured values of cells 81, 82, and 84 are also 4.0 V. However, since the measurement circuit 93 is disconnected, the measured cell voltage of cell 83 is 0.0 V. The output voltage of the entire storage battery system 1 is 16.0 V. The sum of the cell voltages of cells 81-84 is 12.0 V, and the voltage difference is 4.0 V. In the comparison and judgment unit 62, the voltage difference is compared with a predetermined threshold value, where the predetermined threshold value is a value obtained by multiplying the design value by a ratio of 1 or less. As an example, the predetermined threshold value is 3.2 V, which is 80% of the design value of 4.0 V. In FIG. 3B, the predetermined threshold value is 4.0 V or less, and the voltage difference is equal to or greater than the predetermined threshold value, so that the comparison and judgment unit 62 determines that an abnormality has occurred in the measurement circuit 9.

<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 difference between each cell voltage and the reference voltage set for each of the cells 81-84 is calculated 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 judgment 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 judges that an abnormality has occurred in the measurement circuit 9 (S104). Here, S103 corresponds to the comparison and judgment step in the present invention. The display unit 7 issues a notice that an abnormality has occurred in the measurement circuit 9 (S105), and the series of steps ends. An example of the manner in which the notice is issued is to display a specified error code on the display unit 7. Here, S105 corresponds to the notice issue step in the present invention.

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), and 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). Note that 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, as in the above-mentioned voltage difference. Also, the predetermined second threshold value may be a value obtained by multiplying the reference voltage (design value) by a ratio of 1 or less, as in the above-mentioned predetermined threshold value. Here, S106 corresponds to the abnormality judgment process 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 is completed. Here, S108 also corresponds to the notice issuing process in the present invention. If the difference between the cell voltage of each cell 8 and the reference voltage is less than a predetermined second threshold (S106: no), the second comparison and determination unit 63 determines that no abnormality has occurred in the storage battery unit 5, and the series of steps ends.

In the flowchart shown in FIG. 4, the voltage difference between the cell voltage of each cell 8 and the reference voltage is compared with a predetermined threshold (S103) before the difference 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, leading to improvements in the function of the measurement circuit 9.

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 predetermined second threshold. In contrast, the procedure of the method for detecting an abnormality in cell voltage in the second embodiment includes a flow in which the difference between the cell voltage of each cell 8 and the reference voltage is compared with a predetermined second threshold, and then 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.

Figure 5 is a flowchart showing the procedure of the cell voltage abnormality detection method in the second embodiment. Hereinafter, using Figure 5, the procedure will be described in comparison with the procedure of the cell voltage abnormality detection method shown in Figure 4 of the first embodiment. S109 and S110 shown in Figure 5 are the same as S101 and S102 shown in Figure 4, so their description will be omitted. In Figure 4, the comparison and judgment unit 62 first obtains information from the calculation unit 61, but in Figure 5, the second comparison and judgment unit 63 first obtains information from the calculation unit 61. That is, after the calculation unit 61 executes the 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. 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 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. 4.

As described above, in the flowchart shown in FIG. 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 a predetermined second threshold value (S111). 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, so that the series of steps may end 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 performing the action in the comparison and determination unit 62.

In the second embodiment, the functional configuration of the 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. The functional configuration of the storage battery system 1 is the same as that shown in FIG. 2 of the first embodiment. The method of determining whether the measured values of the cell voltages of the cells 81-84 are normal or abnormal is the same as that shown in FIG. 3 of the first embodiment.

<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 step (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;
a comparison and determination step (S103, S112) of determining that an abnormality has occurred in the measurement circuit when it is determined that the difference is of a predetermined degree.

<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;
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.

1: Battery system 2: Distributed power supply system 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 unit 32: Power conversion unit 4: Load 5: Storage battery unit 51: Output circuit 6: Calculation device 61: Calculation unit 62: Comparison/determination unit 63: Second comparison/determination unit 7: Display unit 81-84: Cells 91-94: Measurement circuit

Claims (7)

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 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 : The method for detecting an abnormality in a cell voltage according to claim 1 , wherein the reference voltages of the plurality of cells are all set to be the same, and the first threshold value is a value obtained by multiplying the reference voltage of one of the cells by a predetermined ratio. The method for detecting an abnormality in a cell voltage according to claim 1 or 2, further comprising an alarm step of issuing an alarm indicating 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 judgment step. 4. The method for detecting an abnormality in a cell voltage according to claim 1 , further comprising a second reporting step of reporting that an abnormality has occurred in the voltage across both ends of any one of the cells when the comparison judgment step judges that the voltage difference between the sum of the voltages across both ends and the output voltage is less than the first threshold value and when the abnormality judgment step judges that the voltage across both ends of any one of the cells is abnormal. 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: The battery system according to claim 5 , wherein 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. 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 report is issued that an abnormality has occurred in the measurement circuit;
The storage battery system according to claim 5 or 6 , further comprising an alarm means for issuing an alarm indicating 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.

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