Storage battery system

Abstract

To provide a storage battery system capable of equalizing the charging rate of each storage battery with a simple configuration.SOLUTION: A storage battery system A1 includes a plurality of storage batteries 1, a power conditioner 3, a plurality of main switches 2 connected between any of the plurality of storage batteries 1 and the power conditioner 3 for connecting the plurality of storage batteries 1 in parallel, and a control device 4 for controlling the power conditioner 3. The control device 4 includes a charging rate acquisition unit 41 for acquiring the charging rate of each of the storage batteries 1, and an equalization control unit 42 for opening any of the plurality of main switches 2 according to the charging rate of each of the storage batteries 1 and causing the power conditioner 3 to charge or discharge.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a battery system. [Background technology]

[0002] There is a storage battery system that includes multiple storage batteries connected in parallel and a power conditioner that charges and discharges the multiple storage batteries. In such a storage battery system, there is a problem that the current imbalance occurs during charging and discharging due to the variation in characteristics such as internal resistance of each storage battery, resulting in an uneven charging rate. The charging rate, also called SOC (State Of Charge), is an index that indicates the charging state and is expressed as a percentage of the remaining charge capacity relative to the capacity when fully charged.

[0003] Patent Document 1 discloses a power storage device that can solve this problem. This power storage device is configured with a chopper provided for each battery string, connected in parallel, and suppresses variation in SOC of each battery string by balancing the current of each battery string using the chopper. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-27158 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the case of the power storage device described in Patent Document 1, it is necessary to provide a chopper for each battery string. Therefore, the power storage device is expensive and requires space to place the choppers. Furthermore, if a chopper breaks down, the battery string to which the chopper is connected cannot perform charge / discharge operations, so that the charging rates of the battery strings cannot be equalized.

[0006] The present invention has been devised in light of the above-mentioned circumstances, and has an object to provide a storage battery system that can equalize the charging rates of the storage batteries with a simple configuration. [Means for solving the problem]

[0007] A storage battery system provided by a first aspect of the present invention comprises a plurality of storage batteries, a power conditioner, a plurality of main switches connected between any one of the plurality of storage batteries and the power conditioner for connecting the plurality of storage batteries in parallel, and a control device for controlling the power conditioner, wherein the control device comprises a charging information acquisition unit that acquires charging information which is the charging rate, open circuit voltage, or integrated amount of output current of each of the storage batteries, and an equalization control unit that opens any one of the plurality of main switches in accordance with the charging information of each of the storage batteries and causes the power conditioner to charge or discharge.

[0008] In a preferred embodiment of the present invention, when the plurality of storage batteries includes a storage battery whose charging information is smaller than that of the other storage batteries by a predetermined amount or more, the equalization control unit opens the main switch connected to the other storage batteries to cause the power conditioner to charge, and when the plurality of storage batteries includes a storage battery whose charging information is larger than that of the other storage batteries by a predetermined amount or more, the equalization control unit opens the main switch connected to the other storage batteries to cause the power conditioner to discharge.

[0009] In a preferred embodiment of the present invention, when the plurality of storage batteries includes a storage battery whose charging information is smaller than the other storage batteries by a predetermined amount or more, the equalization control unit opens the main switch connected to the storage battery whose charging information is smaller than the predetermined amount or more to cause the power conditioner to discharge, and when the plurality of storage batteries includes a storage battery whose charging information is larger than the predetermined amount or more than the other storage batteries, the equalization control unit opens the main switch connected to the storage battery whose charging information is larger than the predetermined amount or more to cause the power conditioner to charge.

[0010] In a preferred embodiment of the present invention, the system further includes a plurality of second storage batteries, a second power conditioner, and a plurality of second main switches connected between any of the plurality of second storage batteries and the second power conditioner for connecting the plurality of second storage batteries in parallel, and the equalization control unit opens any of the plurality of main switches in accordance with the charging information of each of the storage batteries, causing the power conditioner to charge and the second power conditioner to discharge, or causing the power conditioner to discharge and the second power conditioner to charge, and opens any of the plurality of second main switches in accordance with the charging information of each of the second storage batteries, causing the second power conditioner to charge and the power conditioner to discharge, or causing the second power conditioner to discharge and charge,

[0011] In a preferred embodiment of the present invention, the system further includes a second storage battery and a second power conditioner to which the second storage battery is connected, and the equalization control unit opens one of the multiple main switches according to the charging information of each of the storage batteries, causing the power conditioner to charge and the second power conditioner to discharge, or causing the power conditioner to discharge and charging the second power conditioner. Effect of the Invention

[0012] According to the present invention, the equalization control unit opens one of the multiple main switches in accordance with the charging information of each storage battery, causing the power conditioner to charge or discharge. Therefore, the equalization control unit can discharge a storage battery with a high charging rate and charge a storage battery with a low charging rate. In this way, the storage battery system according to the present invention can equalize the charging rates of the storage batteries. Furthermore, the storage battery system according to the present invention does not require the addition of a chopper or the like, and has a simple configuration. [Brief description of the drawings]

[0013] [Figure 1]1 is a block diagram showing the overall configuration of a storage battery system according to a first embodiment. [Diagram 2] FIG. 1 is a simplified block diagram of a storage battery system performing a charging rate equalization process. [Diagram 3] 5 is an example of a flowchart showing a charging rate equalization process according to the first embodiment. [Figure 4] 10 is an example of a flowchart showing a charging rate equalization process according to a modified example. [Diagram 5] FIG. 11 is a simplified block diagram of a storage battery system performing a charging rate equalization process according to a modified example. [Figure 6] FIG. 11 is a block diagram showing the overall configuration of a storage battery system according to a second embodiment. [Figure 7] FIG. 11 is a block diagram showing the overall configuration of a storage battery system according to a third embodiment. [Figure 8] FIG. 11 is a simplified block diagram of a storage battery system according to a third embodiment, in which a charging rate equalization process according to the third embodiment is performed. [Figure 9] FIG. 13 is a block diagram showing the overall configuration of a storage battery system according to a modified example of the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0015] FIG. 1 is a block diagram showing the overall configuration of a storage battery system A1 according to a first embodiment. The storage battery system A1 is connected to a power system via a transformer. A load L is connected to a connection line connecting the transformer and the power system. The storage battery system A1 charges with power supplied from the power system or a power generation facility (not shown), and discharges the power in a predetermined case to supply the power to the load L or the power system. The storage battery system A1 includes a plurality of storage batteries 1, a plurality of main switches 2, a power conditioner 3, and a control device 4.

[0016] Each storage battery 1 is a secondary battery that can be repeatedly charged and discharged, for example, a lithium ion battery. The storage battery 1 may be another secondary battery such as a nickel-metal hydride battery, a nickel-cadmium battery, or a lead-acid battery. The storage battery 1 may be a capacitor such as an electric double layer capacitor, instead of a secondary battery. In this embodiment, a case will be described in which the storage battery system A1 includes four storage batteries 11, 12, 13, and 14 as the multiple storage batteries 1. The number of storage batteries 1 included in the storage battery system A1 is not limited.

[0017] The main switches 2 are switches for connecting the storage batteries 1 to the power conditioner 3. Each main switch 2 is connected between one of the storage batteries 1 and the DC side input / output terminal of the power conditioner 3, and opens and closes individually in response to a command from the control device 4. When the main switch 2 is in a closed state, it connects the connected storage battery 1 to the power conditioner 3, and when the main switch 2 is in an open state, it disconnects the connected storage battery 1 from the power conditioner 3. When the main switches 2 are closed, the storage batteries 1 connected to these main switches 2 are connected in parallel to the power conditioner 3. In this embodiment, each main switch 2 is connected to each storage battery 1, and the storage battery system A1 includes four main switches 21, 22, 23, and 24 as the main switches 2. Each main switch 2 may be connected to a storage battery group in which the storage batteries 1 are connected in series or in parallel. When the storage battery 1 includes multiple strings, each main switch 2 may be connected to each string.

[0018] The power conditioner 3 charges and discharges the connected storage battery 1. The DC side input / output terminals of the power conditioner 3 are connected to each storage battery 1 via each main switch 2, and the AC side input / output terminals are connected to the power grid via a transformer. The power conditioner 3 charges and discharges the connected storage battery 1 in response to a command from the control device 4. The power conditioner 3 includes an inverter circuit (not shown), and charges the connected storage battery 1 by converting AC power input from the AC side into DC power and outputting it to the DC side. The power conditioner 3 also discharges the connected storage battery 1 by converting DC power stored in the connected storage battery 1 into AC power and outputting it to the AC side.

[0019] The control device 4 is realized by, for example, a microcomputer, and controls the power conditioner 3 and the main switches 21 to 24. The control device 4 outputs a charge command to the power conditioner 3 to charge each storage battery 1 connected to the power conditioner 3, and outputs a discharge command to discharge each storage battery 1 connected to the power conditioner 3. The control device 4 also outputs a close command to each main switch 2 individually to close the main switch 2, and outputs an open command to open the main switch 2.

[0020] The control device 4 normally closes all the main switches 2 and causes the power conditioner 3 to charge or discharge in response to a command from a higher-level device (not shown). Due to the variation in characteristics such as internal resistance, an imbalance in current occurs during charging and discharging in each storage battery 1. Therefore, the charging and discharging of each storage battery 1 varies with the charging rate. The control device 4 performs a charging rate equalization process, which is a process for suppressing the variation in the charging rate of each storage battery 1. The control device 4 includes a charging rate acquisition unit 41 and an equalization control unit 42 as functional configurations for the charging rate equalization process. Each unit may be configured with a digital circuit or an analog circuit. The control device 4 also includes other functional configurations, but descriptions of functional configurations that are not related to the charging rate equalization process are omitted.

[0021] The charging rate acquisition unit 41 acquires the charging rate of each storage battery 1. The charging rate acquisition unit 41 acquires the charging rate by estimating it using a well-known method such as a current integration method or an OCV method. The method of acquiring the charging rate by the charging rate acquisition unit 41 is not limited. The charging rate acquisition unit 41 outputs the acquired charging rates of each storage battery 1 to the equalization control unit 42.

[0022] The equalization control unit 42 equalizes the charging rates of the storage batteries 1 by controlling each main switch 2 and the power conditioner 3 according to the charging rates of the storage batteries 1 input from the charging rate acquisition unit 41. When the multiple storage batteries 1 include a storage battery 1 whose charging rate is lower than the other storage batteries 1 by a predetermined amount or more, the equalization control unit 42 opens the main switch 2 connected to the other storage batteries 1 to cause the power conditioner 3 to charge. When the multiple storage batteries 1 include a storage battery 1 whose charging rate is higher than the other storage batteries 1 by a predetermined amount or more, the equalization control unit 42 opens the main switch 2 connected to the other storage batteries 1 to cause the power conditioner 3 to discharge.

[0023] For example, the equalization control unit 42 calculates a charging average, which is an arithmetic mean value of the charging rates of the storage batteries 1 input from the charging rate acquisition unit 41, and compares the charging average with the charging rate of each storage battery 1. When the charging rate of a certain storage battery 1 is smaller than the charging average by a first threshold or more, the equalization control unit 42 determines that the charging rate of the certain storage battery 1 is smaller than the charging rate of the other storage batteries 1 by a predetermined amount or more. When the charging rate of a certain storage battery 1 is larger than the charging average by a second threshold or more, the equalization control unit 42 determines that the charging rate of the certain storage battery 1 is larger than the charging rate of the other storage batteries 1 by a predetermined amount or more. The second threshold may be the same as the first threshold, or may be different. The first threshold and the second threshold are, for example, about 20%, but are not limited to this. Note that the number of storage batteries 1 whose charging rates are smaller (larger) than the other storage batteries 1 by a predetermined amount or more is not limited to one, and may be multiple. Also, the method by which the equalization control unit 42 determines which storage batteries 1 whose charging rates are smaller (larger) than the other storage batteries 1 by a predetermined amount or more is not limited. For example, the equalization control unit 42 may compare the charging rates of the respective storage batteries 1 with each other to determine which storage batteries 1 have charging rates that are lower (higher) than the other storage batteries 1 by a predetermined amount. Furthermore, the equalization control unit 42 may determine that the minimum charging rate is lower than the other storage batteries 1 by a predetermined amount when the difference between the minimum charging rate and the second smallest charging rate is equal to or greater than a first threshold, and may determine that the maximum charging rate is higher than the other storage batteries 1 by a predetermined amount when the difference between the maximum charging rate and the second largest charging rate is equal to or greater than a second threshold.

[0024] When there is a storage battery 1 whose charging rate is smaller than the other storage batteries 1 by a predetermined amount or more, the equalization control unit 42 opens the main switch 2 connected to the other storage batteries 1 and causes the power conditioner 3 to charge. As a result, only the storage battery 1 connected to the main switch 2 that remains closed is charged. The equalization control unit 42 causes the power conditioner 3 to continue charging until the charging rate of the storage battery 1 becomes approximately the same as the charging average. In addition, when there is a storage battery 1 whose charging rate is larger than the other storage batteries 1 by a predetermined amount or more, the equalization control unit 42 opens the main switch 2 connected to the other storage batteries 1 and causes the power conditioner 3 to discharge. As a result, only the storage battery 1 connected to the main switch 2 that remains closed is discharged. The equalization control unit 42 causes the power conditioner 3 to continue discharging until the charging rate of the storage battery 1 becomes approximately the same as the charging average. The equalization control unit 42 may continue charging and discharging until the charging rate of the storage battery 1 becomes the charging average, or may continue charging and discharging until it falls within a predetermined range based on the charging average. Furthermore, the equalization control unit 42 may continue charging and discharging for a period of time corresponding to the difference between the initial charging rate of the storage battery 1 and the average charging rate.

[0025] Fig. 2 is a simplified block diagram of a storage battery system A1 performing a charging rate equalization process. Fig. 2 shows a case where the charging rate of the storage battery 11 is lower than the charging rates of the other storage batteries 12, 13, and 14 by a predetermined amount or more. In this case, the main switch 21 remains closed, and the main switches 22, 23, and 24 are open. The power conditioner 3 outputs DC power (see the arrow shown in Fig. 2), thereby charging the storage battery 11. On the other hand, when the charging rate of the storage battery 11 is higher than the charging rates of the other storage batteries 1 by a predetermined amount or more, the states of the main switches 21 to 24 are the same as in Fig. 2, and the power conditioner 3 outputs AC power, thereby discharging the storage battery 11 (power flows in the opposite direction to the arrow in Fig. 2).

[0026] 3 is an example of a flowchart showing the charging rate equalization process performed by the control device 4. The charging rate equalization process is performed at a predetermined timing when there is no command from a higher-level device or the like. Note that the charging rate equalization process is interrupted when a command is received from a higher-level device or the like, and may be resumed or may be performed again from the beginning after the command from the higher-level device or the like is completed.

[0027] First, the charging rate of each storage battery 1 is acquired (S1). Specifically, the charging rate acquisition unit 41 acquires the charging rate of each storage battery 1 and outputs it to the equalization control unit 42. Next, the charging average is calculated (S2). Specifically, the equalization control unit 42 calculates the arithmetic mean value of the charging rates of each storage battery 1 to calculate the charging average.

[0028] Next, it is determined whether or not there is a storage battery 1 whose charging rate is lower than the other storage batteries 1 by a predetermined amount or more (S3). Specifically, the equalization control unit 42 makes this determination by comparing the charging average with the charging rate of each storage battery 1. If there is (S3: YES), each main switch 2 (hereinafter, described as "other switches") connected to the storage batteries 1 other than the detected storage battery 1 is opened (S4). Specifically, the equalization control unit 42 outputs an open command to each of the other switches. As a result, the other switches are opened. Next, charging is started (S5). Specifically, the equalization control unit 42 outputs a charge command to the power conditioner 3. As a result, only the storage battery 1 connected to the power conditioner 3 is charged. Next, the charging rate of the detected storage battery 1 is acquired, and it is determined whether or not the charging rate is within a predetermined range (S6). Specifically, the equalization control unit 42 determines whether or not the charging rate is within a predetermined range based on the charging average. If the charging rate is not within the predetermined range (S6: NO), the process returns to step S6, and the determination in step S6 is repeated. On the other hand, if the charging rate is within the predetermined range (S6: YES), charging is stopped (S7). Specifically, the equalization control unit 42 stops outputting a charging command to the power conditioner 3. That is, the equalization control unit 42 continues charging until the charging rate falls within the predetermined range. Next, the other switches are closed (S8), and the charging rate equalization process is terminated. Specifically, the equalization control unit 42 outputs a closing command to each of the other switches. This causes the other switches to be closed.

[0029] In step S3, if there is no storage battery 1 whose charging rate is lower than the other storage batteries 1 by a predetermined amount or more (S3: NO), it is determined whether there is a storage battery 1 whose charging rate is higher than the other storage batteries 1 by a predetermined amount or more (S9). If there is (S9: YES), each main switch 2 (other switch) connected to the storage batteries 1 other than the detected storage battery 1 is opened (S10). Next, discharging is started (S11). Specifically, the equalization control unit 42 outputs a discharge command to the power conditioner 3. As a result, only the storage battery 1 connected to the power conditioner 3 is discharged. Next, the detected charging rate of the storage battery 1 is acquired, and it is determined whether the charging rate is within a predetermined range (S12). If it is not within the predetermined range (S12: NO), the process returns to step S12, and the determination of step S12 is repeated. On the other hand, if it is within the predetermined range (S12: YES), discharging is stopped (S13). That is, the equalization control unit 42 continues discharging until the charging rate falls within the predetermined range. Next, the other switch is closed (S14), and the charging rate equalization process is terminated.

[0030] In step S9, if there is no storage battery 1 whose charging rate is higher than the other storage batteries 1 by a predetermined amount or more (S9: NO), the charging rate equalization process is terminated. Note that the process shown in the flowchart of FIG. 3 is an example, and the charging rate equalization process performed by the control device 4 is not limited to the above.

[0031] Next, the operation and effects of the storage battery system according to this embodiment will be described.

[0032] According to the present embodiment, the equalization control unit 42 opens one of the main switches 2 according to the charging rates of the storage batteries 1 input from the charging rate acquisition unit 41, and causes the power conditioner 3 to charge or discharge. Therefore, the equalization control unit 42 can discharge the storage battery 1 with a high charging rate and charge the storage battery 1 with a low charging rate. This allows the storage battery system A1 to equalize the charging rates of the storage batteries 1. Furthermore, the storage battery system A1 does not need to be additionally provided with a chopper or the like, and has a simple configuration. Therefore, the storage battery system A1 can be prevented from becoming large and expensive. Furthermore, the storage battery system A1 can be made highly efficient, since no loss due to a chopper occurs, compared to the case where a chopper is added.

[0033] According to the present embodiment, when the plurality of storage batteries 1 includes a storage battery 1 whose charging rate is lower than the other storage batteries 1 by a predetermined amount or more, the equalization control unit 42 opens the main switch 2 connected to the other storage batteries 1 and causes the power conditioner 3 to charge. This allows the equalization control unit 42 to charge only the storage battery 1 connected to the main switch 2 that remains closed, thereby increasing only the charging rate of the storage battery 1. Also, when the plurality of storage batteries 1 includes a storage battery 1 whose charging rate is higher than the other storage batteries 1 by a predetermined amount or more, the equalization control unit 42 opens the main switch 2 connected to the other storage batteries 1 and causes the power conditioner 3 to discharge. This allows the equalization control unit 42 to discharge only the storage battery 1 connected to the main switch 2 that remains closed, thereby decreasing only the charging rate of the storage battery 1.

[0034] Furthermore, according to this embodiment, the equalization control unit 42 calculates a charging average, which is an arithmetic mean value of the charging rates of the storage batteries 1, and compares the charging average with the charging rate of each storage battery 1. This allows the equalization control unit 42 to easily detect a storage battery 1 whose charging rate is lower (higher) than the charging rates of the other storage batteries 1 by a predetermined amount.

[0035] Fig. 4 and Fig. 5 are diagrams for explaining a modified example of the charging rate equalization process of the storage battery system A1 according to the first embodiment. Fig. 4 is an example of a flowchart showing the charging rate equalization process according to the modified example. Fig. 5 is a simplified block diagram of the storage battery system A1 performing the charging rate equalization process according to the modified example.

[0036] When the plurality of storage batteries 1 includes a storage battery 1 whose charging rate is lower than the other storage batteries 1 by a predetermined amount or more, the equalization control unit 42 according to this modification opens only the main switch 2 connected to the detected storage battery 1 and causes the power conditioner 3 to discharge. As a result, the equalization control unit 42 can discharge the storage batteries 1 connected to the main switch 2 that remains closed, thereby decreasing the charging rates of these storage batteries 1. The equalization control unit 42 causes the power conditioner 3 to continue discharging until the charging average becomes approximately the same as the charging rate of the detected storage battery 1. In addition, when the plurality of storage batteries 1 includes a storage battery 1 whose charging rate is higher than the other storage batteries 1 by a predetermined amount or more, the equalization control unit 42 opens only the main switch 2 connected to the detected storage battery 1 and causes the power conditioner 3 to charge. As a result, the equalization control unit 42 can charge the storage batteries 1 connected to the main switch 2 that remains closed, thereby increasing the charging rates of these storage batteries 1. The equalization control unit 42 causes the power conditioner 3 to continue charging until the charging average becomes similar to the detected charging rate of the storage battery 1. The equalization control unit 42 may continue charging and discharging until the charging average becomes the detected charging rate of the storage battery 1, or may continue charging and discharging until the charging average falls within a predetermined range based on the detected charging rate of the storage battery 1. The equalization control unit 42 may also continue charging and discharging for a time period corresponding to the difference between the detected charging rate of the storage battery 1 and the initial charging average.

[0037] Fig. 5 is a simplified block diagram of a storage battery system A1 performing a charging rate equalization process according to a modified example. Fig. 5 shows a case where the charging rate of the storage battery 11 is lower than the charging rates of the other storage batteries 12, 13, 14 by a predetermined amount or more. In this case, the main switches 22, 23, 24 remain closed, and the main switch 21 is open. The power conditioner 3 outputs AC power (see the arrows shown in Fig. 5), thereby discharging the storage batteries 12, 13, 14. On the other hand, when the charging rate of the storage battery 11 is higher than the charging rates of the other storage batteries 1 by a predetermined amount or more, the states of the main switches 21 to 24 are the same as in Fig. 5, and the power conditioner 3 outputs DC power, thereby charging the storage batteries 12, 13, 14 (power flows in the opposite direction to the arrows in Fig. 5).

[0038] As shown in FIG. 4, the charging rate equalization process according to the modified example has steps S1 to S3 and S9 in common with the flowchart shown in FIG. 3, steps S4 to S8 are changed to steps S4' to S8', and steps S10 to S14 are changed to steps S10' to S14'.

[0039] In step S3, if there is a storage battery 1 whose charging rate is lower than the other storage batteries 1 by a predetermined amount or more (S3: YES), the main switch 2 (hereinafter referred to as the "corresponding switch") connected to the detected storage battery 1 is opened (S4'). Specifically, the equalization control unit 42 outputs an open command to each of the corresponding switches. This causes the corresponding switch to be opened. Next, discharging is started (S5'). Next, the charging rate of each storage battery 1 is acquired, the charging average is calculated, and it is determined whether or not the charging average is within a predetermined range (S6'). If it is not within the predetermined range (S6': NO), the process returns to step S6' and the determination of step S6' is repeated. On the other hand, if it is within the predetermined range (S6': YES), discharging is stopped (S7'). That is, the equalization control unit 42 continues discharging until the charging average is within the predetermined range. Next, the corresponding switch is closed (S8'), and the charging rate equalization process is terminated.

[0040] In step S9, if there is a storage battery 1 whose charging rate is greater than the other storage batteries 1 by a predetermined amount or more (S9: YES), the main switch 2 (corresponding switch) connected to the detected storage battery 1 is opened (S10'). Next, charging is started (S11'). Next, the charging rate of each storage battery 1 is acquired, the charging average is calculated, and it is determined whether or not the charging average is within a predetermined range (S12'). If it is not within the predetermined range (S12': NO), the process returns to step S12' and the determination of step S12' is repeated. On the other hand, if it is within the predetermined range (S12': YES), charging is stopped (S13'). That is, the equalization control unit 42 continues charging until the charging average is within the predetermined range. Next, the corresponding switch is closed (S14'), and the charging rate equalization process is terminated. Note that the process shown in the flowchart of FIG. 4 is an example, and the charging rate equalization process performed by the control device 4 is not limited to the above-mentioned one.

[0041] Fig. 6 is a diagram for explaining a storage battery system A2 according to a second embodiment, and is a block diagram showing the overall configuration of the storage battery system A2. In Fig. 6, elements that are the same as or similar to those in the storage battery system A1 according to the first embodiment are given the same reference numerals, and duplicated explanations will be omitted. The storage battery system A2 according to this embodiment differs from the storage battery system A1 according to the first embodiment in that it performs a charging rate equalization process according to the open circuit voltage of each storage battery 1.

[0042] The storage battery system A2 according to the second embodiment further includes a plurality of voltage sensors 5. The storage battery system A2 includes four voltage sensors 51, 52, 53, and 54 as the plurality of voltage sensors 5. The voltage sensor 51 (52, 53, and 54) is disposed at the output end of the storage battery 11 (12, 13, and 14) and detects the open circuit voltage of the storage battery 11 (12, 13, and 14) when no charging or discharging is taking place.

[0043] The control device 4 according to the second embodiment includes an open circuit voltage acquisition unit 43 instead of the charging rate acquisition unit 41. The open circuit voltage acquisition unit 43 acquires the open circuit voltage detected by each voltage sensor 5 and outputs it to the equalization control unit 42. The equalization control unit 42 according to the second embodiment equalizes the charging rates of each storage battery 1 by controlling each main switch 2 and the power conditioner 3 according to the open circuit voltage of each storage battery 1 input from the open circuit voltage acquisition unit 43. The open circuit voltage of each storage battery 1 increases as the charging rate increases. Therefore, the equalization control unit 42 can perform the charging rate equalization process based on the open circuit voltage of each storage battery 1 instead of the charging rate of each storage battery 1.

[0044] According to this embodiment, the equalization control unit 42 opens one of the main switches 2 according to the open-circuit voltage of each storage battery 1 input from the open-circuit voltage acquisition unit 43, and causes the power conditioner 3 to charge or discharge. Therefore, the equalization control unit 42 can discharge the storage battery 1 with a high open-circuit voltage and charge the storage battery 1 with a low open-circuit voltage. This allows the storage battery system A2 to equalize the charging rates of the storage batteries 1. Furthermore, the storage battery system A2 does not require the addition of a chopper or the like, and has a simple configuration. Furthermore, the storage battery system A2 has a configuration in common with the storage battery system A1, and thus achieves the same effects as the storage battery system A1.

[0045] The storage battery system A2 may include current sensors that detect the output current of each storage battery 1 instead of the voltage sensors 5, and detect the accumulated amount of the output current in the charging direction (hereinafter referred to as the "accumulated charging amount"). The larger the accumulated charging amount of the storage battery 1, the higher the charging rate of the storage battery 1. Therefore, the equalization control unit 42 can perform the charging rate equalization process based on the accumulated charging amount detected and accumulated by each current sensor, instead of the charging rate of each storage battery 1. Also, the smaller the accumulated amount of the output current of the storage battery 1 in the discharging direction (hereinafter referred to as the "accumulated discharging amount"), the higher the charging rate of the storage battery 1. Therefore, the equalization control unit 42 can perform the charging rate equalization process based on the accumulated discharging amount detected and accumulated by each current sensor, instead of the charging rate of each storage battery 1. Also, the equalization control unit 42 may perform the charging rate equalization process by combining two or more of the charging rate, the open circuit voltage, the accumulated charging amount, and the accumulated discharging amount.

[0046] 7 and 8 are diagrams for explaining a storage battery system A3 according to a third embodiment. FIG. 7 is a block diagram showing the overall configuration of the storage battery system A3. FIG. 8 is a simplified block diagram of the storage battery system A3 performing a charging rate equalization process according to the third embodiment. In FIG. 7 and FIG. 8, elements that are the same as or similar to those in the storage battery system A1 according to the first embodiment are given the same reference numerals, and duplicated explanations are omitted. The storage battery system A3 according to this embodiment differs from the storage battery system A1 according to the first embodiment in that it includes two sets of blocks each having a plurality of storage batteries 1 and a power conditioner 3.

[0047] As shown in FIG. 7, the storage battery system A3 according to the third embodiment includes a first block 6a, a second block 6b, and a control device 4. The first block 6a includes a plurality of storage batteries 11a, 12a, 13a, and 14a, a plurality of main switches 21a, 22a, 23a, and 24a, and a power conditioner 3a. The second block 6b includes a plurality of storage batteries 11b, 12b, 13b, and 14b, a plurality of main switches 21b, 22b, 23b, and 24b, and a power conditioner 3b. The first block 6a and the second block 6b are similar to the storage battery system A1 according to the first embodiment except for the control device 4. The numbers of storage batteries 1 and main switches 2 included in the first block 6a and the second block 6b are not limited, and may be the same or different between the first block 6a and the second block 6b.

[0048] The control device 4 according to the third embodiment controls the power conditioners 3a and 3b and the main switches 21a, 22a, 23a, 24a, 21b, 22b, 23b, and 24b. The control device 4 uses the second block 6b when performing a charging rate equalization process for suppressing variations in the charging rates of the multiple storage batteries 11a, 12a, 13a, and 14a in the first block 6a. Specifically, when the control device 4 charges any one of the multiple storage batteries 11a, 12a, 13a, and 14a, the control device 4 causes the second block 6b to output the same power as the charging power. In this case, the control device 4 causes the power conditioner 3b to discharge while keeping the multiple main switches 21b, 22b, 23b, and 24b closed. When power is supplied from the storage battery system A3 to the load L, the power obtained by adding the charging power to the power supplied to the load L may be output from the second block 6b.

[0049] For example, when the charging rate of the storage battery 11a is lower than the charging rates of the other storage batteries 12a, 13a, and 14a by a predetermined amount or more, the main switch 21a remains closed, the main switches 22a, 23a, and 24a are opened, and the power conditioner 3 outputs DC power, as shown in Fig. 8. At this time, the main switches 21b, 22b, 23b, and 24b remain closed, and the power conditioner 3b outputs AC power. The AC power output by the power conditioner 3b is converted to DC power by the power conditioner 3a and output, and is charged into the storage battery 11a.

[0050] Conversely, when discharging any of the storage batteries 11a, 12a, 13a, 14a, the control device 4 charges the second block 6b with the same power as the discharged power. In this case, the control device 4 charges the power conditioner 3b while keeping the main switches 21b, 22b, 23b, 24b closed. When supplying power from the storage battery system A3 to the load L, the second block 6b may be charged with power obtained by subtracting the power supplied to the load L from the discharged power. The AC power output by the power conditioner 3a is converted to DC power by the power conditioner 3b and output, and is charged into the storage batteries 11b, 12b, 13b, 14b.

[0051] The control device 4 also uses the first block 6a when performing a charging rate equalization process to suppress variations in the charging rates of the multiple storage batteries 11b, 12b, 13b, and 14b in the second block 6b. Specifically, when the control device 4 charges any one of the multiple storage batteries 11b, 12b, 13b, and 14b, it causes the first block 6a to output the same power as the charging power. In this case, the control device 4 causes the power conditioner 3a to discharge while keeping the multiple main switches 21a, 22a, 23a, and 24a closed. When power is supplied from the storage battery system A3 to the load L, it is sufficient to cause the first block 6a to output power obtained by adding the charging power to the power supplied to the load L. The AC power output by the power conditioner 3a is converted to DC power by the power conditioner 3b and output, and is charged into any one of the storage batteries 11b, 12b, 13b, and 14b.

[0052] Conversely, when discharging any of the storage batteries 11b, 12b, 13b, and 14b, the control device 4 causes the first block 6a to be charged with the same power as the discharged power. In this case, the control device 4 causes the power conditioner 3a to charge while keeping the main switches 21a, 22a, 23a, and 24a closed. When supplying power from the storage battery system A3 to the load L, the first block 6a may be charged with power obtained by subtracting the power supplied to the load L from the discharged power. The AC power output by the power conditioner 3b is converted to DC power by the power conditioner 3a and output, and is charged into the storage batteries 11a, 12a, 13a, and 14a.

[0053] In this embodiment, the same effects as those in the first embodiment can be achieved. Furthermore, according to this embodiment, the control device 4 causes the second block 6b to discharge the same power when charging the first block 6a, and causes the second block 6b to charge the same power when discharging the first block 6a. Furthermore, the control device 4 causes the first block 6a to discharge the same power when charging the second block 6b, and causes the first block 6a to charge the same power when discharging the second block 6b. This allows the storage battery system A3 to perform the charging rate equalization process without outputting power to the power grid or receiving power from the power grid.

[0054] In the present embodiment, the storage battery system A3 includes two blocks each including a plurality of storage batteries 1 and a power conditioner 3, but is not limited to this. The storage battery system A3 may include three or more blocks.

[0055] 9 is a block diagram for explaining a modification of the storage battery system A3 according to the third embodiment, showing the overall configuration of the storage battery system A3 according to the modification. In this modification, a second block 6c is provided instead of the second block 6b. The second block 6c includes a storage battery 10 and a power conditioner 3b, and the storage battery 10 is constantly connected to the power conditioner 3b.

[0056] The control device 4 uses the second block 6c when performing a charging rate equalization process to suppress variation in the charging rates of the multiple storage batteries 11a, 12a, 13a, and 14a in the first block 6a. Specifically, when charging any of the multiple storage batteries 11a, 12a, 13a, and 14a, the control device 4 causes the power conditioner 3b to discharge the same power as the charging power, thereby outputting the same power from the second block 6c. In addition, when discharging any of the multiple storage batteries 11a, 12a, 13a, and 14a, the control device 4 causes the power conditioner 3b to charge the same power as the discharging power, thereby charging the second block 6c.

[0057] The storage battery system according to the present invention is not limited to the above-described embodiment. The specific configuration of each part of the storage battery system according to the present invention can be freely designed in various ways. [Explanation of symbols]

[0058] A1, A2, A3: storage battery system, 1: storage battery, 2: main switch, 3, 3a, 3b: power conditioner, 4: control device, 41: charging rate acquisition unit, 42: equalization control unit, 43: open circuit voltage acquisition unit, 5: voltage sensor

Claims

1. A plurality of storage batteries; A power conditioner, A plurality of main switches are connected between any one of the plurality of storage batteries and the power conditioner, for connecting the plurality of storage batteries in parallel; A control device for controlling the power conditioner; Equipped with The control device includes: a charging information acquisition unit that acquires charging information, which is a charging rate, an open circuit voltage, or an integrated amount of an output current of each of the storage batteries; A leveling control unit that opens one of the plurality of main switches in response to the charging information of each of the storage batteries to charge or discharge the power conditioner; Equipped with Battery storage system.

2. The equalization control unit is When the plurality of storage batteries includes a storage battery whose charging information is smaller than that of the other storage batteries by a predetermined amount or more, the main switch connected to the other storage batteries is opened to cause the power conditioner to perform charging; When the plurality of storage batteries includes a storage battery whose charging information is greater than or equal to a predetermined value compared to other storage batteries, the main switch connected to the other storage batteries is opened to cause the power conditioner to discharge. The battery system according to claim 1 .

3. The equalization control unit is When the plurality of storage batteries includes a storage battery whose charge information is smaller than that of the other storage batteries by a predetermined amount or more, the main switch connected to the storage battery whose charge information is smaller than that of the other storage batteries is opened to cause the power conditioner to discharge the power conditioner; When the plurality of storage batteries includes a storage battery whose charging information is greater than or equal to a predetermined value compared to other storage batteries, the main switch connected to the storage battery whose charging information is greater than or equal to the predetermined value is opened to allow the power conditioner to perform charging. The battery system according to claim 1 .

4. A plurality of second storage batteries; A second power conditioner; a plurality of second main switches connected between any one of the plurality of second storage batteries and the second power conditioner for connecting the plurality of second storage batteries in parallel; Further equipped with The equalization control unit is According to the charging information of each of the storage batteries, one of the plurality of main switches is opened, and the power conditioner is caused to charge and the second power conditioner is caused to discharge, or the power conditioner is caused to discharge and the second power conditioner is caused to charge; According to the charging information of each of the second storage batteries, any of the plurality of second main switches is opened, and the second power conditioner is charged and the power conditioner is discharged, or the second power conditioner is discharged and the power conditioner is charged. The battery system according to claim 1 .

5. A second storage battery; a second power conditioner connected to the second storage battery; Further equipped with The equalization control unit is According to the charging information of each of the storage batteries, one of the plurality of main switches is opened, and the power conditioner is caused to charge and the second power conditioner is caused to discharge, or the power conditioner is caused to discharge and the second power conditioner is caused to charge. The battery system according to claim 1 .

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