JP7768191B2 - Battery system and method for controlling charge and discharge of battery system - Google Patents

Description

This disclosure relates to a battery system and a method for controlling charging and discharging of a battery system.

Patent Document 1 discloses an energy storage system that includes multiple battery units connected in parallel to a common power grid and a power regulator. Specifically, an inverter and a sensor unit are connected to the battery units. The inverter is disposed between the battery units and the power grid. The sensor unit detects the state of the battery units and sends a signal related to the detected state of the battery units to the power regulator. The power regulator controls the charging and discharging of each battery unit to reduce differences in the state of deterioration between the battery units.

JP 2015-115968 A

The inventors of the present application have discovered the following technical problems.
In such a power storage system, each of the battery units may be restrained by a restraining jig. Furthermore, some of the battery units may be deteriorated due to their temperature being higher than the temperature that is desirable for charging and discharging. In such a case, the power regulator reduces the amount of current flowing through some of the battery units while increasing the amount of current flowing through the remaining battery units with lower temperatures in order to suppress the deterioration. As a result, the load is concentrated on the battery units with lower temperatures. This causes the batteries in the battery units to expand, increasing the load on the restraining jig.

This disclosure was made in consideration of the above-mentioned problems, and provides a battery system that can suppress an increase in the load on a restraint jig, and a method for controlling the charging and discharging of a battery system.

The battery system according to the present disclosure comprises:
A battery system including a plurality of battery units connected in parallel to a common power system and a control unit,
Each battery unit includes a relay, a current sensor, and a battery pack.
the relay and the current sensor are disposed between the battery pack and the power grid;
the battery pack is restrained by a restraining jig;
the control unit determines whether a total accumulated discharge amount of each of the battery units calculated using a current value measured by the current sensor of each of the battery units is equal to or greater than a predetermined value;
The control unit closes a relay of a battery unit determined to have a total accumulated discharge amount equal to or greater than a predetermined value, thereby prohibiting charging and discharging of the battery pack of the determined battery unit.

Furthermore, in the above-mentioned battery system, the predetermined value may be determined using the load value required for the restraint jig to break.

The charge/discharge control method for a battery system according to the present disclosure includes:
A charge/discharge control method for a battery system including a plurality of battery units connected in parallel to a common power system and a control unit, comprising:
Each battery unit includes a relay, a current sensor, and a battery pack.
the relay and the current sensor are disposed between the battery pack and the power grid;
the battery pack is restrained by a restraining jig;
determining whether or not a total accumulated discharge amount of each of the battery units calculated using the current values measured by the current sensors of each of the battery units is equal to or greater than a predetermined value;
and closing a relay of a battery unit determined to have the total accumulated discharge amount equal to or greater than a predetermined value, thereby prohibiting charging and discharging of the battery pack of the determined battery unit.

This configuration stops charging and discharging of a specific battery unit whose total accumulated discharge amount is equal to or greater than a predetermined value. This prevents expansion of the specific battery unit and prevents an increase in the load on the restraining jig.

This disclosure makes it possible to suppress an increase in the load on the restraining jig.

1 is a block diagram showing a configuration example of a battery system according to a first embodiment; 1 is a schematic diagram illustrating a side view of an example of a battery pack according to a first embodiment. 10 is a graph showing a restraint load relative to a total discharge integrated amount. 3 is a flowchart showing a charge/discharge control method according to the first embodiment. 4 is a timing chart showing an example of the operation of the battery system according to the first embodiment.

Specific embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. Furthermore, the following description and drawings have been simplified as appropriate for clarity.

First Embodiment
A first embodiment will be described with reference to Figures 1 to 3. Figure 1 is a block diagram showing an example of the configuration of a battery system according to the first embodiment. Figure 2 is a schematic diagram showing a side view of an example of a battery pack of the battery system shown in Figure 1. Figure 3 is a graph showing the constraint load relative to the total discharge integrated amount.

It should be noted that the right-handed XYZ coordinate system shown in Figure 2 is a matter of convenience for explaining the positional relationships of the components. Normally, the positive Z axis is vertically upward, and the XY plane is the horizontal plane, which is common between all drawings.

As shown in FIG. 1, the battery system 100 includes battery units 10-1, 10-2, 10-3, 10-4, ..., 10-N and a control unit 6. It is preferable that the battery units 10-1, 10-2, 10-3, 10-4, ..., 10-N all have the same configuration. N is a natural number greater than or equal to 2.

Battery units 10-1, 10-2, 10-3, 10-4, ..., 10-N are connected in parallel to a common power system 1. The power system 1 is connected to a power generation device (not shown) and a load. The power system 1 is preferably AC.

Battery unit 10-1 includes a relay 2-1, a current sensor 4-1, and a battery pack 5-1. Similarly, battery unit 10-N includes a relay 2-N, a current sensor 4-N, and a battery pack 5-N. The relay 2-1 and the current sensor 4-1 are disposed between the battery pack 5-1 and the power grid 1. Similarly, the relay 2-N and the current sensor 4-N are disposed between the battery pack 5-N and the power grid 1.

Relays 2-1, 2-2, 2-3, 2-4, ..., 2-N are each connected to the control unit 6 so that they can receive signals from the control unit 6. Relays 2-1, 2-2, 2-3, 2-4, ..., 2-N each perform an opening and closing operation in response to the signals received from the control unit 6. By performing this opening and closing operation, relay 2-1 electrically connects and disconnects battery pack 5-1 to and from the power grid 1. Similarly, by performing this opening and closing operation, relay 2-N electrically connects and disconnects battery pack 5-N to and from the power grid 1.

Current sensor 4-1 measures the current flowing between battery pack 5-1 and power grid 1 and generates a current value. Similarly, current sensor 4-N measures the current flowing between battery pack 5-N and power grid 1 and generates a current value.

Battery units 10-1, 10-2, 10-3, 10-4, ..., 10-N may each be equipped with a boost converter 3-1, 3-2, 3-3, 3-4, ..., 3-N.

The boost converter 3-1 is arranged between the battery pack 5-1 and the power grid 1. Specifically, the current sensor 4-1, the boost converter 3-1, and the relay 2-1 are arranged in this order between the battery pack 5-1 and the power grid 1. The boost converter 3-1 appropriately boosts the current flowing between the battery pack 5-1 and the power grid 1. This prevents current from circulating between the battery pack 5-1 and the power grid 1. Similarly, the boost converter 3-N is arranged between the battery pack 5-N and the power grid 1. Specifically, the current sensor 4-N, the boost converter 3-N, and the relay 2-N are arranged in this order between the battery pack 5-N and the power grid 1. The boost converter 3-N appropriately boosts the current flowing between the battery pack 5-N and the power grid 1. This prevents current from circulating between the battery pack 5-N and the power grid 1.

Battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N may include, for example, at least one battery module and may also include a protection circuit, a cooling mechanism, etc. as appropriate. The battery module may include, for example, a lithium-ion secondary battery, an all-solid-state battery, etc.

Battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N are restrained by restraining jigs 7-1, 7-2, 7-3, 7-4, ..., 7-N (not shown), respectively. Restraining jigs 7-1, 7-2, 7-3, 7-4, ..., 7-N may have the same configuration. Specifically, as shown in FIG. 2, battery pack 5-N is restrained by restraining jig 7-N. Restraining jig 7-N includes restraining members 7a-N, 7b-N and fastening portions 7c-N, 7d-N. Restraining members 7a-N, 7b-N may be any member capable of restraining battery pack 5-N, such as a pair of plate-shaped bodies. The pair of plate-shaped bodies may have a predetermined rigidity. Fastening portions 7c-N, 7d-N may be any member capable of fastening restraining members 7a-N, 7b-N, such as a bolt and nut. While the restraining members 7a-N and 7b-N hold the battery pack 5-N between them, the fastening portions 7c-N and 7d-N fasten the restraining members 7a-N and 7b-N. The battery pack 5-N is subjected to a restraining load from the restraining members 7a-N and 7b-N.

The control unit 6 is connected to each of the current sensors 4-1, 4-2, 4-3, 4-4, ..., 4-N so that it can acquire signals from each of the current sensors 4-1, 4-2, 4-3, 4-4, ..., 4-N. The control unit 6 acquires the current values measured by each of the current sensors 4-1, 4-2, 4-3, 4-4, ..., 4-N from the current sensors 4-1, 4-2, 4-3, 4-4, ..., 4-N.

The control unit 6 calculates the total accumulated discharge amount of the battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N using the current values acquired from the current sensors 4-1, 4-2, 4-3, 4-4, ..., 4-N. The total accumulated discharge amount may be determined, for example, by integrating the current value during discharge from the start to the end of discharge. The control unit 6 determines whether this calculated total accumulated discharge amount is equal to or greater than a predetermined value. This predetermined value may be determined using the load value required to break the restraining jigs 7-1, 7-2, 7-3, 7-4, ..., 7-N.

The load curve CN shown in Figure 3 indicates the load applied to the restraining jig 7-N when the total accumulated discharge amount of the battery pack 5-N is changed within a predetermined range. As shown in Figure 3, the load applied to the restraining jig 7-N is proportional to the total accumulated discharge amount of the battery pack 5-N. When the total accumulated discharge amount of the battery pack 5-N reaches EN, the load applied to the restraining jig 7-N reaches LN, and the restraining jig 7-N breaks. In other words, the load value required to break the restraining jig 7-N is LN. Therefore, EN can be determined as the predetermined value for the total accumulated discharge amount of the current sensor 4-N. If the restraining jigs 7-1, 7-2, 7-3, 7-4, ..., 7-N all have the same configuration, EN can similarly be determined as the predetermined value for the total accumulated discharge amount of the battery pack 5-N.

The control unit 6 controls the opening and closing of relays 2-1, 2-2, 2-3, 2-4, ..., 2-N. Specifically, the control unit 6 closes the relay of a battery unit whose total accumulated discharge amount is determined to be equal to or greater than a predetermined value EN, thereby prohibiting charging and discharging of the battery pack of the battery unit. For example, if it is determined that the total accumulated discharge amount of battery unit 10-K is equal to or greater than a predetermined value, the control unit 6 closes relay 2-K of battery unit 10-K, thereby prohibiting charging and discharging of battery pack 5-K of battery unit 10-K. Here, K is at least one natural number selectable from the range of 1 to N, inclusive.

In detail, the control unit 6 may turn on an abnormality flag when it determines that the calculated total accumulated discharge amount is equal to or greater than a predetermined value. If the abnormality flag is on, it is assumed that an abnormality has occurred in the battery pack. The control unit 6 may increment an abnormality counter depending on the length of time or number of times that the abnormality flag is on. If the abnormality counter reaches a threshold value Tr, the control unit 6 may turn on the abnormality determination. If the abnormality determination is on, it is determined that an abnormality has definitely occurred in the battery pack. If the abnormality determination is turned on, the control unit 6 may turn off the relay. A relay off state means that the relay is closed. By having this configuration, the control unit 6 may be able to prevent erroneous determination that the calculated total accumulated discharge amount is equal to or greater than a predetermined value.

The battery system 100 may also include a power regulator. The power regulator reduces the amount of current flowing through some of the battery units 10-1, 10-2, 10-3, 10-4, ..., 10-N that have a temperature higher than the preferred temperature for charging and discharging. At roughly the same time as this reduction, the power regulator increases the amount of current flowing through the remaining battery units 10-1, 10-2, 10-3, 10-4, ..., 10-N that have a temperature lower than the preferred temperature for charging and discharging. This prevents some of the battery units 10-1, 10-2, 10-3, 10-4, ..., 10-N from deteriorating due to their temperatures being higher than the preferred temperature for charging and discharging.

<Charge/Discharge Control Method>
Next, an example of a charge/discharge control method for the battery system 100 according to the first embodiment will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the charge/discharge control method according to the first embodiment.

The control unit 6 calculates the total accumulated discharge amount of battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N (step ST1).

Next, the control unit 6 determines whether the total accumulated discharge amount of the battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N is equal to or greater than a predetermined value EN (step ST2).

The control unit 6 determines that the total accumulated discharge amounts of all battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N are less than the predetermined value EN (step ST2: NO). Then, steps ST1 and ST2 are repeated.

On the other hand, the control unit 6 determines that the total accumulated discharge amount of at least one of the battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N is equal to or greater than the predetermined value EN (step ST2: YES). The control unit 6 then prohibits charging or discharging of at least one of the battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N whose total accumulated discharge amount is determined to be equal to or greater than the predetermined value EN (step ST3). Specifically, for example, if the control unit 6 determines that the total accumulated discharge amount of battery pack 5-N is equal to or greater than the predetermined value EN, it closes relay 2-N of battery pack 5-N. This prohibits charging or discharging of battery pack 5-N.

As described above, with the above configuration, charging and discharging of at least one of the battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N whose total accumulated discharge amount is equal to or greater than a predetermined value is stopped. This prevents expansion of the battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N and prevents an increase in the load on the restraining jigs 7-1, 7-2, 7-3, 7-4, ..., 7-N.

The battery system 100 is also preferably equipped with the above-mentioned power regulator. The power regulator increases the amount of current flowing through the remaining battery units 10-1, 10-2, 10-3, 10-4, ..., 10-N, which have a lower temperature than the temperature that is preferable from the viewpoint of charging and discharging. As discharging continues, the total accumulated discharge amount of the battery units with increased current flowing reaches a predetermined value. Therefore, charging and discharging of the battery packs of the battery units with increased current flowing is stopped. In other words, the concentration of load on the battery units is suppressed. Therefore, the increase in load on the restraining jigs 7-1, 7-2, 7-3, 7-4, ..., 7-N due to the expansion of the battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N of the battery units can be suppressed.

Furthermore, with reference to Figure 5, the operation of the battery system 100 in an example of the charge/discharge control method for the battery system 100 according to the first embodiment will be described. Figure 5 is a timing chart showing an example of the operation of the battery system according to the first embodiment. The horizontal axis of Figure 5 represents time, and the vertical axis of Figure 3 represents the determination of the total discharge accumulated amount, the state of the abnormality occurrence flag, the state of the counter, the abnormality determination, and the operation of the relay.

As shown in Figure 5, at time t0 when charging and discharging of the battery system 100 begins, if it is determined that the total accumulated discharge amount of battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N is less than the predetermined value EN (step ST2: NO), the total accumulated discharge amount determination is in the OFF state. Relay 2-N is in the OFF state.

A predetermined time has passed since time t0, and time t1 is reached. At time t1, it is determined that the total accumulated discharge amount of at least one of battery packs 5-1, 5-2, 5-3, 5-4, ..., 5-N is equal to or greater than the predetermined value EN (step ST2: YES). For example, it is determined that the total accumulated discharge amount of battery pack 5-N is equal to or greater than the predetermined value EN. The total accumulated discharge amount determination for battery pack 5-N is in the ON state.

Then, at time t2, the abnormality occurrence flag is changed from OFF to ON. The abnormality counter begins to increment.

After that, at time t3, the abnormality counter reaches the threshold value Tr. Furthermore, the abnormality determination is turned on, and it is determined that an abnormality has definitely occurred in the battery pack.

After that, at time t4, relay 2-N is changed from the ON state to the OFF state. Relay 2-N closes, cutting off the electrical connection between battery pack 5-N and the power grid 1. Note that relay 2-N is a system main relay (SMR), and the OFF state of relay 2-N preferably corresponds to the OFF state of the system main relay (SMR-OFF).

Each component in the above-described embodiments may be configured with hardware, software, or both, and may be configured with a single piece of hardware or software, or may be configured with multiple pieces of hardware or software. The functions (processing) of each device may be implemented by a computer having a CPU (Central Processing Unit), memory, etc. For example, a program for performing a method in the embodiment (e.g., a control method) may be stored in a storage device, and each function may be implemented by having a CPU execute the program stored in the storage device.

These programs can be stored and supplied to a computer using various types of non-transitory computer-readable media. Non-transitory computer-readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-RWs, and semiconductor memory (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs (Random Access Memory)). The programs may also be supplied to a computer via various types of transitory computer-readable media. Examples of transitory computer-readable media include electrical signals, optical signals, and electromagnetic waves. Transitory computer-readable media can be supplied to a computer via wired communication paths such as electrical wires and optical fibers, or wireless communication paths.

The present invention is not limited to the above-described embodiment, and modifications can be made as appropriate without departing from the spirit of the invention. Furthermore, the present invention may be implemented by combining the above-described embodiment and examples thereof as appropriate.

100 Battery system 10-1, 10-2, 10-3, 10-4, 10-N Battery unit 1 Power system 2-1, 2-2, 2-3, 2-4, 2-N Relay 3-1, 3-2, 3-3, 3-4, 3-N Boost converter 4-1, 4-2, 4-3, 4-4, 4-N Current sensor 5-1, 5-2, 5-3, 5-4, 5-N Battery pack 6 Control unit 7-N Restraint jig 7a-N, 7b-N Restraint member 7c-N, 7d-N Fastening part LN Load value EN Predetermined value CN (of total discharge accumulated amount) Load curve t0, t1, t2, t3, t4 Time points

Claims (2)

A battery system including a plurality of battery units connected in parallel to a common power system and a control unit,
Each battery unit includes a relay, a current sensor, and a battery pack.
the relay and the current sensor are disposed between the battery pack and the power grid;
the battery pack is restrained by a restraining jig;
the control unit determines whether a total accumulated discharge amount of each of the battery units calculated using a current value measured by the current sensor of each of the battery units is equal to or greater than a predetermined value;
the control unit closes a relay of a battery unit determined to have a total accumulated discharge amount equal to or greater than a predetermined value, thereby prohibiting charging and discharging of the battery pack of the determined battery unit ;
The predetermined value is determined using a load value required for the restraint jig to break .
Battery system. A charge/discharge control method for a battery system including a plurality of battery units connected in parallel to a common power system and a control unit, comprising:
Each battery unit includes a relay, a current sensor, and a battery pack.
the relay and the current sensor are disposed between the battery pack and the power grid;
the battery pack is restrained by a restraining jig;
determining whether or not a total accumulated discharge amount of each of the battery units calculated using the current values measured by the current sensors of each of the battery units is equal to or greater than a predetermined value;
and closing a relay of a battery unit determined to have a total accumulated discharge amount equal to or greater than a predetermined value, thereby prohibiting charging and discharging of the battery pack of the determined battery unit ,
The predetermined value is determined using a load value required for the restraint jig to break .
A method for controlling charging and discharging of a battery system.