Battery storage system

Abstract

This battery system provides a mechanism to prevent overcharging and over-discharging of multiple batteries even when a failure occurs in one of the multiple power converters and the operation of multiple batteries continues using the remaining functioning power converters. [Solution] A battery system is provided comprising: multiple storage batteries; multiple power converters for charging and discharging the multiple storage batteries; multiple switches that allow switching between an individual connection state in which the multiple storage batteries are individually connected to the multiple power converters and a parallel connection state in which the multiple storage batteries are connected in parallel to the multiple power converters; and a control device that controls the operation of the multiple power converters and controls the switching of the multiple switches, wherein the control device performs an operation to equalize the voltage magnitude of each of the multiple storage batteries when charging or discharging the multiple storage batteries in the parallel connection state.

Description

Technical Field

[0001] Embodiments of the present invention relate to a battery system.

Background Art

[0002] There is a battery system including a plurality of batteries, a plurality of power conversion devices, and a control device. The plurality of power conversion devices are provided corresponding to each of the plurality of batteries. The plurality of power conversion devices are connected to each of the plurality of batteries, and perform charging of the plurality of batteries based on power supplied from the outside and discharging of the power stored in the plurality of batteries to the outside. The control device controls the charging and discharging operations of the plurality of batteries by the plurality of power conversion devices. The battery system is connected to, for example, a power grid, and suppresses fluctuations in the voltage and frequency of the power grid by performing charging and discharging of the plurality of batteries according to fluctuations in the power of the power grid.

[0003] Thus, in a battery system in which a plurality of batteries and a plurality of power conversion devices correspond one-to-one, if a power conversion device fails, even if the battery connected to the failed power conversion device is normal, this battery cannot be used, and the utilization rate of the battery decreases. Further, since the battery cannot be used, the capacity of the entire system also decreases.

[0004] Therefore, when a power conversion device fails and the battery connected to the failed power conversion device is normal, it has been considered to connect each of the plurality of batteries to the remaining normal power conversion devices so that the operation of the battery connected to the failed power conversion device can be continued. Thereby, it is possible to suppress a decrease in the utilization rate of the battery and a decrease in the capacity of the entire system.

[0005] However, when connecting multiple batteries to the remaining functioning power converters, the voltages of each battery may differ. If the multiple batteries are operated in this state, the voltage variations among the batteries will not be corrected, and overcharging or over-discharging may occur in one of the batteries.

[0006] Therefore, in a battery storage system, it is desirable to be able to suppress overcharging and over-discharging of multiple batteries even when a failure occurs in one of the multiple power converters and the operation of multiple batteries continues with the remaining working power converters. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-207714 [Patent Document 2] Patent No. 7211509 [Patent Document 3] Japanese Patent Publication No. 2024-31887 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Embodiments of the present invention provide a battery storage system that can suppress overcharging and over-discharging of multiple batteries even when a failure occurs in one of the multiple power converters and the operation of the multiple batteries continues with the remaining working power converters. [Means for solving the problem]

[0009] According to an embodiment of the present invention, the present invention comprises a plurality of storage batteries, a plurality of power conversion devices provided corresponding to each of the plurality of storage batteries, which perform charging of the plurality of storage batteries based on power supplied from an external source and discharging of the power stored in the plurality of storage batteries to the outside, a plurality of switches that can switch between an individual connection state in which each of the plurality of storage batteries is individually connected to each of the plurality of power conversion devices, and a parallel connection state in which each of the plurality of storage batteries is connected in parallel to each of the plurality of power conversion devices, and a control device that controls the charging and discharging operations of the plurality of storage batteries by the plurality of power conversion devices, and controls the switching between the closed state and the open state of the plurality of switches, wherein the control device sets the plurality of storage batteries and the plurality of power conversion devices to the individual connection state when they are functioning normally, and A battery system is provided that, when a failure occurs in any of the multiple power converters, the remaining working power converters can continue to operate each of the multiple batteries by connecting them in parallel, and the system acquires information regarding the voltage of each of the multiple batteries. When charging the multiple batteries in the parallel connection state, the system uses the voltage information to connect the batteries to the multiple power converters in order from the lowest voltage to the highest voltage, thereby equalizing the voltage of each of the multiple batteries. When discharging the multiple batteries in the parallel connection state, the system uses the voltage information to connect the batteries to the multiple power converters in order from the highest voltage to the highest voltage, thereby equalizing the voltage of each of the multiple batteries. [Effects of the Invention]

[0010] A battery storage system is provided that can suppress overcharging and over-discharging of multiple batteries even when a failure occurs in one of the multiple power converters and the operation of multiple batteries continues with the remaining working power converters. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram schematically representing the battery storage system according to the embodiment. [Modes for carrying out the invention]

[0012] Each embodiment will be described below with reference to the drawings. Please note that the drawings are schematic or conceptual, and the relationships between the thickness and width of each part, as well as the ratios of the sizes of the parts, are not necessarily identical to those of reality. Furthermore, even when representing the same part, the dimensions and ratios may differ between drawings. In this specification and in each figure, elements similar to those described above are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

[0013] Figure 1 is a block diagram schematically representing a battery storage system according to an embodiment. As shown in Figure 1, the battery storage system 10 comprises multiple batteries 12a to 12c, multiple power converters 14a to 14c, and a control device 16.

[0014] Multiple power converters 14a to 14c are provided in correspondence with each of the multiple storage batteries 12a to 12c. Each of the multiple power converters 14a to 14c is connected to each of the multiple storage batteries 12a to 12c and performs charging of the multiple storage batteries 12a to 12c based on power supplied from an external source, and discharges the power stored in the multiple storage batteries 12a to 12c to an external source.

[0015] This example shows three battery storage units 12a-12c and three power converters 14a-14c. However, the number of battery storage units 12a-12c and the number of power converters 14a-14c are not limited to three; they can be any number of two or more.

[0016] The control device 16 controls the charging and discharging operations of multiple storage batteries 12a to 12c by multiple power converters 14a to 14c.

[0017] The battery system 10 is connected to the power grid 2 via, for example, a switch 3, a transformer 4, etc. The battery system 10 suppresses fluctuations in the voltage and frequency of the AC power of the power grid 2 by, for example, charging and discharging a plurality of batteries 12a to 12c according to fluctuations in the AC power of the power grid 2.

[0018] The plurality of power conversion devices 14a to 14c are connected to the power grid 2 via, for example, a switch 3, a transformer 4, etc. The plurality of power conversion devices 14a to 14c perform a discharging operation of the plurality of batteries 12a to 12c by converting the DC power of the plurality of batteries 12a to 12c into AC power corresponding to the power grid 2 and supplying the converted AC power to the power grid 2. Then, the plurality of power conversion devices 14a to 14c perform a charging operation of the plurality of batteries 12a to 12c by converting the AC power of the power grid 2 into DC power corresponding to the plurality of batteries 12a to 12c and supplying the converted DC power to the plurality of batteries 12a to 12c.

[0019] However, the battery system 10 is not limited to the power grid 2 and may be used, for example, by connecting to a load, a generator, etc. The power of the load or the generator is not limited to AC power and may be DC power or the like. The power conversion operation of the plurality of power conversion devices 14a to 14c is not limited to the operation of converting between DC power and AC power and may be, for example, an operation of converting between DC power and another DC power.

[0020] The battery system 10 further includes a plurality of switches 18a to 18e. The switch 18a is provided between the battery 12a and the power conversion device 14a. The switch 18b is provided between the battery 12b and the power conversion device 14b. The switch 18c is provided between the battery 12c and the power conversion device 14c. Thereby, the plurality of power conversion devices 14a to 14c are connected to each of the plurality of batteries 12a to 12c via the plurality of switches 18a to 18c.

[0021] The switch 18d is provided between the connection path of the storage battery 12a and the power conversion device 14a and the connection path of the storage battery 12b and the power conversion device 14b. The switch 18e is provided between the connection path of the storage battery 12b and the power conversion device 14b and the connection path of the storage battery 12c and the power conversion device 14c.

[0022] More specifically, when the switches 18a and 18b are turned on, the switch 18d electrically connects the positive electrode of the storage battery 12a and the positive electrode of the storage battery 12b, and also electrically connects the negative electrode of the storage battery 12a and the negative electrode of the storage battery 12b. More specifically, when the switches 18b and 18c are turned on, the switch 18e electrically connects the positive electrode of the storage battery 12b and the positive electrode of the storage battery 12c, and also electrically connects the negative electrode of the storage battery 12b and the negative electrode of the storage battery 12c.

[0023] In addition, the switches 18d and 18e are provided at positions closer to the power conversion devices 14a to 14c than the switches 18a to 18c. One end of the switch 18d is connected between the power conversion device 14a and the switch 18a. The other end of the switch 18d is connected between the power conversion device 14b and the switch 18b. One end of the switch 18e is connected between the power conversion device 14b and the switch 18b. The other end of the switch 18e is connected between the power conversion device 14c and the switch 18c.

[0024] Thus, by turning on the switches 18a to 18c and turning off the switches 18d and 18e, each of the plurality of storage batteries 12a to 12c can be individually connected to each of the plurality of power conversion devices 14a to 14c.

[0025] By switching on each of the switches 18a to 18e, multiple batteries 12a to 12c can be connected in parallel to multiple power converters 14a to 14c. When switches 18a to 18e are switched on, each of the multiple power converters 14a to 14c can charge and discharge each of the multiple batteries 12a to 12c. In other words, when switches 18a to 18e are switched on, multiple batteries 12a to 12c can be connected in parallel and treated as one large-capacity battery.

[0026] In this way, the multiple switches 18a to 18e are configured to switch between an individual connection state in which each of the multiple storage batteries 12a to 12c is individually connected to each of the multiple power converters 14a to 14c, and a parallel connection state in which each of the multiple storage batteries 12a to 12c is connected in parallel to each of the multiple power converters 14a to 14c.

[0027] The switching between the closed and open states of the multiple switches 18a to 18e is controlled by the control device 16. The control device 16 controls the charging and discharging operations of the multiple batteries 12a to 12c by the multiple power converters 14a to 14c, and also controls the switching between the closed and open states of the multiple switches 18a to 18e. In other words, the control device 16 controls the switching between an individual connection state in which each of the multiple batteries 12a to 12c is individually connected to each of the multiple power converters 14a to 14c, and a parallel connection state in which each of the multiple batteries 12a to 12c is connected in parallel to each of the multiple power converters 14a to 14c.

[0028] When the multiple storage batteries 12a to 12c and the multiple power converters 14a to 14c are functioning normally, the control device 16 closes switches 18a to 18c and opens switches 18d and 18e, thereby creating an individual connection state where each of the multiple storage batteries 12a to 12c is individually connected to each of the multiple power converters 14a to 14c. This allows each of the multiple power converters 14a to 14c to individually charge and discharge each of the multiple storage batteries 12a to 12c.

[0029] Furthermore, when a failure occurs in any of the power converters 14a to 14c, the control device 16 turns on each of the switches 18a to 18e, thereby creating a parallel connection state in which each of the batteries 12a to 12c is connected in parallel to each of the power converters 14a to 14c. This allows the operation of each of the batteries 12a to 12c to continue using the remaining functioning power converters even when one of the power converters 14a to 14c fails.

[0030] The control device 16 detects failures in multiple power converters 14a to 14c by communicating with each of the multiple power converters 14a to 14c, for example. The control device 16 detects failures in multiple power converters 14a to 14c by receiving failure signals from the multiple power converters 14a to 14c, for example. However, the method for detecting failures in multiple power converters 14a to 14c is not limited to the above, and any method that allows the control device 16 to appropriately detect failures in multiple power converters 14a to 14c may be used. The control device 16 may also detect failures in multiple power converters 14a to 14c by receiving signals from a higher-level controller, for example.

[0031] For example, suppose power converter 14c fails. If there is a one-to-one correspondence between multiple batteries 12a to 12c and multiple power converters 14a to 14c, even if the battery 12c connected to power converter 14c is functioning normally, the failure of power converter 14c will render the battery 12c unusable, reducing the utilization rate of the battery 12c. Furthermore, the inability to use the battery 12c will also reduce the overall system capacity.

[0032] Therefore, in response to detecting a failure in the power converter 14c, the control device 16 connects each of the multiple storage batteries 12a to 12c in parallel to each of the multiple power converters 14a to 14c, creating a parallel connection state. This allows the remaining normal power converters 14a and 14b to continue operating the storage batteries 12c, thereby suppressing a decrease in the utilization rate of the storage batteries 12c and a decrease in the overall system capacity.

[0033] Multiple storage batteries 12a to 12c each have control units 20a to 20c. The control units 20a to 20c control the charging and discharging operations of the batteries built into the storage batteries 12a to 12c and monitor the state of the built-in batteries. For example, the control units 20a to 20c suppress the occurrence of overcharging and over-discharging of the built-in batteries. The control units 20a to 20c are, for example, a battery management system.

[0034] The control device 16 communicates with the control units 20a to 20c of multiple storage batteries 12a to 12c, thereby obtaining information regarding the voltage of each of the multiple storage batteries 12a to 12c from the control units 20a to 20c.

[0035] The control device 16 acquires, for example, information on the State of Charge (SOC) of batteries 12a to 12c as voltage information from the control units 20a to 20c. However, the voltage information is not limited to this, and may be any information regarding the voltage of batteries 12a to 12c. The voltage information may also be information representing the magnitude of the voltage of batteries 12a to 12c. Furthermore, the control device 16 may acquire voltage information not only from the control units 20a to 20c, but also from, for example, another controller that controls the operation of multiple batteries 12a to 12c, or from a voltmeter that measures the voltage of batteries 12a to 12c. The method for acquiring voltage information for each of batteries 12a to 12c is not limited to the above, and may be any method that allows the control device 16 to appropriately acquire voltage information.

[0036] When charging multiple batteries 12a to 12c in a parallel connection state, the control device 16 uses the acquired voltage information to connect the batteries 12a to 12c to the power converters 14a to 14c in order from the battery with the lowest voltage, thereby equalizing the voltage of each of the batteries 12a to 12c.

[0037] For example, as shown in Figure 1, suppose the charge level of battery 12a is 78%, the charge level of battery 12b is 76%, and the charge level of battery 12c is 74%. In this case, the control device 16 first closes switches 18c to 18e and opens switches 18a and 18b, and connects only battery 12c, which has the lowest voltage (charge level), to multiple power converters 14a to 14c, thereby charging only battery 12c.

[0038] The control device 16 charges the battery 12c, and when the voltage of battery 12c matches the voltage of the next lowest-voltage battery 12b (when the charge level of battery 12c reaches 76%), it switches the switch 18b to the closed position, thereby connecting battery 12b to multiple power converters 14a to 14c in addition to battery 12c, and starting to charge batteries 12b and 12c.

[0039] The control device 16 then charges batteries 12b and 12c, and when the voltages of batteries 12b and 12c match the voltage of the next lowest voltage (highest voltage) battery 12a (when the charge rate of batteries 12b and 12c reaches 78%), the control device 16 switches the switch 18a to the closed position. This connects battery 12a to multiple power converters 14a to 14c in addition to batteries 12b and 12c, and starts charging batteries 12a to 12c. This makes it possible to equalize the voltage of each of the multiple batteries 12a to 12c.

[0040] Furthermore, when discharging multiple batteries 12a to 12c in a parallel connection state, the control device 16 uses the acquired voltage information to connect the batteries 12a to 12c to the power converters 14a to 14c in order from the battery with the highest voltage, thereby equalizing the voltage of each of the batteries 12a to 12c.

[0041] For example, as shown in Figure 1, suppose the charge level of battery 12a is 78%, the charge level of battery 12b is 76%, and the charge level of battery 12c is 74%. In this case, the control device 16 first closes switches 18a, 18d, and 18e, and opens switches 18b and 18c, and connects only battery 12a, which has the highest voltage (charge level), to multiple power converters 14a to 14c, thereby discharging only battery 12a.

[0042] The control device 16 charges the battery 12a, and when the voltage of battery 12a matches the voltage of the next highest-voltage battery 12b (when the charge level of battery 12a reaches 76%), it switches the switch 18b to the closed position, thereby connecting battery 12b to multiple power converters 14a to 14c in addition to battery 12a, and starting the discharge of batteries 12a and 12b.

[0043] The control device 16 then discharges batteries 12a and 12b, and when the voltages of batteries 12a and 12b match the voltage of battery 12c, which has the next highest voltage (lowest voltage) (when the charge rate of batteries 12a and 12b reaches 74%), the control device 16 switches the switch 18c to the closed position. This connects battery 12c to multiple power converters 14a to 14c in addition to batteries 12a and 12b, and starts discharging batteries 12a to 12c. In this way, just as during charging, the voltages of multiple batteries 12a to 12c can be made equal during discharging.

[0044] As described above, in the battery storage system 10 according to this embodiment, when the control device 16 charges multiple batteries 12a to 12c in a parallel connection state, and when it discharges multiple batteries 12a to 12c in a parallel connection state, it performs an operation to equalize the voltage magnitude of each of the multiple batteries 12a to 12c. Therefore, in the battery storage system 10 according to this embodiment, even if a failure occurs in one of the multiple power converters 14a to 14c and the operation of the multiple batteries 12a to 12c is continued with the remaining normal power converters, it is possible to suppress overcharging and over-discharging of the multiple batteries 12a to 12c.

[0045] Furthermore, in the battery storage system 10 according to this embodiment, when the control device 16 charges multiple batteries 12a to 12c in a parallel connection state, it connects the batteries with the lowest voltages to the multiple power converters 14a to 14c in order, and then connects the batteries with the next lowest voltages to the multiple power converters 14a to 14c at the timing when the voltage of the next lowest voltage battery matches that of the previous lowest voltage battery. This makes it possible to suppress the occurrence of crosscurrent between multiple batteries 12a to 12c even when multiple batteries 12a to 12c are connected in parallel.

[0046] Furthermore, in the battery storage system 10 according to this embodiment, when the control device 16 discharges multiple batteries 12a to 12c in a parallel connection state, it connects the batteries with the highest voltage to the multiple power converters 14a to 14c in order, and then connects the batteries with the next highest voltage to the multiple power converters 14a to 14c at the timing when the voltage of the next highest voltage battery matches that of the previous highest voltage battery. This makes it possible to suppress the occurrence of crosscurrent between multiple batteries 12a to 12c even when multiple batteries 12a to 12c are connected in parallel.

[0047] Furthermore, in the battery storage system 10, it may not be possible to freely supply power to the power grid 2 side due to contracts with, for example, power companies. In this case, it is preferable to equalize the voltage levels of multiple batteries 12a to 12c during charging.

[0048] This embodiment includes the following aspects. (Note 1) Multiple battery storage systems, Multiple power conversion devices are provided corresponding to each of the multiple storage batteries, and perform charging of the multiple storage batteries based on power supplied from an external source, and discharging of the power stored in the multiple storage batteries to an external source. Multiple switches that allow switching between an individual connection state in which each of the multiple storage batteries is individually connected to each of the multiple power converters, and a parallel connection state in which each of the multiple storage batteries is connected in parallel to each of the multiple power converters, A control device that controls the charging and discharging operations of the multiple power converters and the switching between the closed and open states of the multiple switches, Equipped with, The control device is When the aforementioned multiple storage batteries and the aforementioned multiple power converters are functioning normally, the individual connection state is set. When a failure occurs in any of the aforementioned power converters, by connecting them in parallel, the remaining functioning power converters can continue to operate each of the aforementioned batteries. Information regarding the voltage of each of the aforementioned multiple storage batteries is obtained, When charging the multiple batteries in the parallel connection state, based on the voltage information, the power converter is connected to the multiple batteries in order from the battery with the lowest voltage, thereby equalizing the voltage of each of the multiple batteries. A battery system that, when discharging the multiple batteries in the parallel connection state, connects the batteries to the power converters in order from the battery with the highest voltage, based on the voltage information, thereby equalizing the voltage of each of the multiple batteries.

[0049] (Note 2) The battery system according to Appendix 1, wherein, when charging the multiple batteries in the parallel connection state, the control device connects the batteries in order from the lowest voltage to the multiple power converters, and then connects the next lowest voltage battery to the multiple power converters at a timing that matches the voltage of the next lowest voltage battery.

[0050] (Note 3) The battery system according to Appendix 1 or 2, wherein when discharging the multiple batteries in the parallel connection state, the control device connects the batteries in order from the highest voltage to the multiple power converters, and then connects the next highest voltage battery to the multiple power converters at a timing that matches the voltage of the next highest voltage battery.

[0051] (Note 4) The aforementioned multiple storage batteries each have a control unit that monitors the state of the batteries, The battery system according to any one of the appendices 1 to 3, wherein the control device communicates with the control units of the plurality of batteries to obtain information regarding the voltage of each of the plurality of batteries from the control units.

[0052] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0053] 2...Power system, 3...Switch, 4...Transformer, 10...Battery system, 12a~12c...Battery, 14a~14c...Power converter, 16...Control device, 18a~18e...Switch, 20a~20c...Control unit

Claims

1. Multiple battery storage systems, Multiple power conversion devices are provided corresponding to each of the multiple storage batteries, and perform charging of the multiple storage batteries based on power supplied from an external source, and discharging of the power stored in the multiple storage batteries to an external source. Multiple switches that allow switching between an individual connection state in which each of the multiple storage batteries is individually connected to each of the multiple power converters, and a parallel connection state in which each of the multiple storage batteries is connected in parallel to each of the multiple power converters, A control device that controls the charging and discharging operations of the multiple power converters and the switching between the closed and open states of the multiple switches, Equipped with, The control device is When the aforementioned multiple storage batteries and the aforementioned multiple power converters are functioning normally, the individual connection state is set. When a failure occurs in any of the aforementioned power converters, by connecting them in parallel, the remaining functioning power converters can continue to operate each of the aforementioned batteries. Information regarding the voltage of each of the aforementioned multiple storage batteries is obtained, When charging the multiple batteries in the parallel connection state, based on the voltage information, the power converter is connected to the multiple batteries in order from the battery with the lowest voltage, thereby equalizing the voltage of each of the multiple batteries. A battery system that, when discharging the multiple batteries in the parallel connection state, connects the batteries to the power converters in order from the battery with the highest voltage, based on the voltage information, thereby equalizing the voltage of each of the multiple batteries.

2. The battery system according to claim 1, wherein, when the control device charges the plurality of batteries in the parallel connection state, it connects the batteries in order from the lowest voltage to the plurality of power converters, and then connects the next lowest voltage battery to the plurality of power converters at a timing that matches the voltage of the next lowest voltage battery.

3. The battery system according to claim 1, wherein when discharging the multiple batteries in the parallel connection state, the control device connects the batteries in order from the highest voltage to the multiple power converters, and then connects the next highest voltage battery to the multiple power converters at a timing that matches the voltage of the next highest voltage battery.

4. The aforementioned multiple storage batteries each have a control unit that monitors the state of the batteries, The battery system according to claim 1, wherein the control device communicates with the control units of the plurality of batteries to obtain information regarding the voltage of each of the plurality of batteries from the control units.

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