Energy storage system

An energy storage system that includes a battery module including a plurality of battery cells, a battery management module connected to the battery cells through a plurality of first wires, detecting voltages of the battery cells and performing first cell balancing operations of the battery cells, and an external balancing module connected to the battery cells through a plurality of second wires, discharging the battery cells to a predetermined voltage and performing second cell balancing operations of the battery cells.

CLAIM PRIORITY

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on 12 Nov. 2012 and there duly assigned Serial No 10-2012-0127754.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention generally relate to an energy storage system.

2. Description of the Related Art

An energy storage system that is a hybrid combination of a solar power generation system and a power storage system can store surplus power from a solar cell and a grid that is supplied to a load while supplying power to the load in a secured manner in the event of power failure.

SUMMARY OF THE INVENTION

It is therefore an aspect of the present invention to provide an energy storage system, which can perform a more efficient cell balancing operation.

At least one of the above and other features and advantages may be realized by providing an energy storage system that includes a battery module including a plurality of battery cells, a battery management module connected to the battery cells through a plurality of first wires, detecting voltages of the battery cells and performing first cell balancing operations of the battery cells, and an external balancing module connected to the battery cells through a plurality of second wires, discharging the battery cells to a predetermined voltage and performing second cell balancing operations of the battery cells. The battery module may further include first connectors installed at electrode terminals of the battery cells and connecting the battery cells to an external device.

The battery management module may include the first wires connected to the battery cells, respectively, a plurality of internal balancing device units connected to the battery cells in parallel through the first wires, a controller detecting voltages of the battery cells through the first wires and controlling the internal balancing device units to perform the first cell balancing operations, and first data ports for controlling a control signal based on the information on the voltages of the battery cells from the controller to an external device.

The internal balancing device units may include internal balancing resistors and internal balancing switches connected in series between the first wires.

The battery management module may discharge a second battery cells having higher voltages than a first battery cell having the lowest voltage, among the plurality of battery cells until each voltage of the second battery cells is equal to the voltage of the first battery cell.

The external balancing module may include the second wires connected to the battery cells, respectively, a plurality of external balancing device units connected in series between the second wires, and second data ports receiving the control signal based on the information on the voltages of the battery cells from the battery management module.

The energy storage system may further include second connectors installed in the second wires and connecting the external balancing device units to the battery cells, respectively.

The external balancing device units may include external balancing resistors and external balancing switches connected in series between the second wires.

The external balancing resistors may be cement resistors.

The external balancing module may forcibly discharge voltages of the battery cells to a predetermined voltage level according to the control signal.

The second wires may have larger diameters than the first wires.

The second wires may have higher allowable current than the first wires.

The external balancing module may discharge the battery cells to a higher current than the battery management module.

The external balancing module may be installed to be attached to/detached from the battery module and the battery management module.

At least one of the above and other features and advantages may be realized by providing a cell balancing system of an energy storage system comprising a battery module including a plurality of battery cells and a battery management module connected to the battery cells through a plurality of first wires, detecting voltages of the battery cells and performing first cell balancing operations of the battery cells, the cell balancing system comprising: a plurality of second wires, connectors installed in the second wires and connecting the second wires to the battery cells, respectively, a plurality of balancing device units connected in series between the second wires, and data ports for receiving information on voltages of the battery cells from the battery management module, wherein the cell balancing system is installed to be attached to/detached from the battery module and the battery management module through the connectors and the data ports, discharges the battery cells to a predetermined voltage level and performs second cell balancing operations.

According to the present invention, an energy storage system is provided, which can perform a more efficient cell balancing operation.

DETAILED DESCRIPTION OF THE INVENTION

A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components. The inventive concept may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity.

It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers, patterns and/or sections, these elements, components, regions, layers, patterns and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer pattern or section from another region, layer, pattern or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of example embodiments.

In an energy storage system, a power storage system is largely composed of a battery module including a plurality of battery cells, and a battery management module controlling charging/discharging of the battery module and performing cell balancing operations.

In general, a cell balancing operation in a battery pack for use in a notebook computer or an electrically driven device is performed with a low balancing current (or discharge current). Since the battery pack use small-sized circular cells, it has a very low capacity of 1 Ah to 3 Ah, and the cell balancing operation is performed based on a passive cell balancing method in which the current of several tens of milliamperes (mA) is made to flow to a resistor.

However, since the capacity of battery cells used in the energy storage system is in a range of 50 Ah to 60 Ah, it is difficult to efficiently perform a cell balancing operation by adopting a cell balancing current level of a general small-sized battery pack.

FIG. 1schematically illustrates a configuration of an energy storage system1000according to an embodiment of the present invention andFIG. 2is a circuit view of an energy storage system1000according to an embodiment of the present invention.

Referring toFIGS. 1 and 2, the energy storage system1000according to an embodiment of the present invention includes a battery module100, a battery management module200, and an external balancing module300.

The battery module100may supply battery power. The battery module100may be a rechargeable battery capable of charging/discharging and may be constituted by a plurality of small-capacity battery cells to implement large-capacity power or a single large-capacity battery cell. For example, as shown inFIG. 2, the battery module100may include a plurality of battery cells B1to B8. The plurality of battery cells B1to B8are in series connected to each other to form the battery module100. In addition, the battery module100serves as a basic unit and may be constituted by a plurality of battery modules connected in parallel to each other. Hereinafter, in the illustrated embodiment, for the sake of convenient explanation, the present invention will be described with regard to a single battery module100including 8 battery cells B1to B8connected in series to each other by way of example.

The battery management module200may be connected to two terminals of the battery cells B1to B8, that is, first terminals (+) and second terminals (−), through a plurality of first wires SL, respectively, and maintains and manages various states of the battery cells B1to B8to secure stability of the battery cells B1to B8. In detail, the battery management module200may monitor voltages of the battery cells B1to B8through the first wires SL and may perform cell balancing operations of the battery cells B1to B8. That is to say, the battery management module200may detect voltages of the battery cells B1to B8and may perform cell balancing operations on cell voltages higher than the lowest cell voltage based on the voltage of the battery cell having the lowest voltage, among the plurality of battery cells B1to B8.

For example, when the voltage of the second battery cell B2is detected to be the lowest cell voltage, balancing operations are performed only on the battery cells having approximately 20 mV higher than the second battery cell B2, and the balancing operations are terminated when a voltage difference between cells is less than or equal to 10 mV.

As described above, in order to perform own balancing operations on the plurality of battery cells B1to B8, the battery management module200may include a plurality of first wires L1, a plurality of balancing device units210(to be referred to as internal balancing device units, hereinafter) and a controller220.

The plurality of first wires SL may be connected to two terminals of the battery cells B1to B8, that is, first terminals (+) and second terminals (−), through a plurality of first wires SL, respectively, and may be used to detect voltages of the battery cells B1to B8and to perform cell balancing operations of the battery cells B1to B8, as described above.

The internal balancing device units210may include a plurality of sub internal balancing device units R2and S2connected in parallel to the plurality of battery cells B1to B8through the first wires SL. Each of the sub internal balancing device units R2and S2may include internal balancing resistors R2and internal balancing switches S2, which are connected in series to each other.

The controller220may be connected to the battery cells B1to B8through the plurality of first wires SL and detects voltages of the battery cells B1to B8. In addition, the controller220may perform cell balancing operations on cell voltages higher than the lowest cell voltage based on the voltage of the battery cell having the lowest voltage, among the plurality of battery cells B1to B8.

For example, when the voltage of the second battery cell B2among the battery cells B1to B8is detected to be the lowest cell voltage, the controller220may perform balancing operations on the battery cells whose voltages are a predetermined level higher than the voltage of the second battery cell B2, such that a voltage difference between the second battery cell B2and each of the battery cells B1and B3to B8is greater than or equal to the predetermined level. In a case where a balancing operation needs to be performed on the third battery cell B3, the controller220may turn on the third internal balancing switches S2connected in parallel to the third battery cell B3. Here, the current output from the third battery cell B3may be consumed through third internal balancing resistors R3. Here, the controller220maintains a turned-on state of the third internal balancing switches S2until a voltage difference between two cells B2and B3reaches a predetermined level or less, and when the voltage difference between two cells B2and B3reaches a predetermined level or less, the third internal balancing switches S2are turned off, thereby terminating the cell balancing operations.

Hereinafter, a cell balancing system suitable to operating the energy storage system1000will be described in more detail. More specifically, the external balancing module300installed to be attached to/detached from the battery module100and the battery management module200will be described in detail.

Referring toFIG. 2, the external balancing module300according to an embodiment of the present invention may include a plurality of second wires BL, external balancing device units320and second data ports330.

The plurality of second wires BL may be configured to correspond to the plurality of first wires SL in number. The second wires BL are used as high current paths for performing cell balancing operations on the plurality of battery cells B1to B8within a short time, and electric wires having relatively high allowable current are suitably selected and used as the second wires BL. For example, when AWG22 (maximum allowable current: 3 A) is selected and used as the first wires SL, AWG18 (allowable current: 7˜16 A) may be selected and used as the second wires BL. In general, the higher the allowable current is, the larger the diameter of an electric wire becomes.

Second connectors310for connecting the external balancing device units320and the plurality of battery cells B1to B8may be installed in the plurality of second wires BL. Here, first connectors110are further installed at the respective electrode terminals of the battery module100. The first connectors110may be connected to the second connectors310while cell balancing operations are performed using the external balancing module300. In a case where the first and second connectors110and310are connected to each other, the plurality of second wires BL may be electrically connected to the plurality of battery cells B1to B8, respectively.

The external balancing device units320may include a plurality of sub external balancing device units R3and S3connected in parallel to the battery cells B1to B8through the plurality of second wires SL. The sub external balancing device units R3and S3may include external balancing resistors R3and external balancing switches S3connected in series, respectively. Since high current may flow in the external balancing resistors R3, cement resistors having excellent heat generating characteristics may be used as the external balancing resistors R3. In addition, devices capable of flowing out high current may be used as the external balancing switches S3.

The second data ports330may receive information on the voltages of the battery cells B1to B8, as detected from the controller220. Here, the first data ports230for transmitting information on voltages of the plurality of battery cells B1to B8to the controller220are installed. When the first and second data ports230and330are connected to each other, the external balancing module300may receive the information on voltages of the plurality of battery cells B1to B8. Here, the information on voltages of the plurality of battery cells B1to B8may include control signals of the external balancing switches S3based on the detected voltages of the battery cells B1to B8, which will later be described in more detail.

Meanwhile, the first data ports230and the second data ports330may transmit data to corresponding components through a first data wire DL1and a second data wire DL2.

Hereinafter, the operation of the external balancing module300according to an embodiment of the present invention will be described in detail.

FIG. 3is a circuit view illustrating a state in which an external balancing module300shown inFIG. 2is assembled with a battery module100and a battery management module200.

The external balancing module300to an embodiment of the present invention may be assembled with the battery module100and the battery management module200during a regular maintenance and repair cycle (6 to 12 months) of the energy storage system1000and may perform cell balancing operations. In addition, during normal operation of the energy storage system1000, the external balancing module300may be detached from the battery module100and the battery management module200. In this case, the cell balancing operation may be performed by the battery management module200but may be skipped according to necessity. The external balancing module300may be detached from/attached to the battery module100and the battery management module200through the first and second connectors110and310and the first and second data ports230and330.

As shown inFIG. 3, when the external balancing module300is assembled with the battery module100and the battery management module200, the controller220may transmit information on voltages of the battery cells B1to B8to the external balancing module300through the first and second data ports230and330, and the external balancing module300may apply the received information to control terminals of the external balancing switches S3. Here, the information on voltages of the battery cells B1to B8may include control signals of the external balancing switches S3based on the voltages of the battery cells B1to B8.

For example, when the first and second connectors110and310are connected to each other and the first and second data ports230and330are connected to each other, the controller220may transmit the control signals turning on all of the external balancing switches S3through the first and second data ports230and330. Accordingly, all of the external balancing switches S3are turned on, and a discharge current of several to several tens of amperes may flow through the first and second connectors110and310and the plurality of second wires BL from the plurality of battery cells B1to B8. In addition, the discharge current may be consumed by the corresponding external balancing resistors R3, thereby performing cell balancing operations of the battery module100.

The external balancing module300performs a forced discharge operation until a target voltage (or a target voltage range) is reached for every cell, rather than a discharge operation on a particular cell like in the cell balancing operation of the battery management module100. Here, the plurality of battery cells B1to B8may be discharged until they reach the target voltage (or the target voltage range). The controller220may consistently monitor voltages of the battery cells B1to B8, and when a target voltage (or target voltage range) is detected from an arbitrary cell, the control signals for turning off the corresponding external balancing switches S3are output, thereby terminating discharging of the corresponding cell. In such a manner, the cell balancing operations are performed until target voltages (or target voltage ranges) of the battery cells B1to B8are all detected.

Thereafter, if the voltages of all the battery cells B1to B8are equal to each other, the controller220turns off all of the external balancing switches S3to terminate the cell balancing operations through the external balancing module300.

Meanwhile, in a state in which cell balancing has not yet been terminated, the first and second connectors110and310and the first and second data ports230and330are disconnected from each other, thereby forcibly terminating cell balancing operations.

According to the embodiment of the present invention, since the second wires BL have higher allowable current (or larger diameters) than the first wires SL, higher current may continuously flow in the second wires BL than in the first wires SL. Accordingly, the external balancing module300may perform cell balancing operations of the large-capacity battery module100within a short time.

An example embodiment of the energy storage system has been disclosed herein, and although specific terms are employed, it is used and is to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.