Battery module and energy storage device including same

Abstract

To provide an energy storage device, in which a voltage between adjacent two battery cells among a large number of battery cells connected in series can each be equalized through an isolated DC / DC converter, and a battery module.SOLUTION: The energy storage device includes battery modules 113a, 113b, ... composed of a large number of battery cells Cell_1, Cell_2, ..., and Cell_x connected in series, a large number of isolated DC / DC converters IC1, IC2, ..., and ICx electrically coupled to the large number of battery cells, respectively, and a controller Co that controls a charge mode and a discharge mode of the large number of isolated DC / DC converters. The large number of isolated DC / DC converters each constitute a cell voltage equalization device 113am having one end connected to one battery cell and the other end connected to another adjacent battery cell to equalize a cell voltage between the two battery cells.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] Various embodiments of the present invention relate to battery modules and energy storage devices including the same. [Background technology]

[0002] Generally, an energy storage system (ESS) refers to a device that stores surplus electricity or energy produced through new renewable energy in a storage device (e.g., a battery) and supplies electricity when needed, thereby improving the efficiency of power usage.

[0003] The energy storage device is composed of a battery, a Battery Management System (BMS) for monitoring the battery status and controlling and operating the battery, a Power Conversion System (PCS) for charging and discharging the battery, and a battery control unit (BCU) for communicating with the BMS and PCS to diagnose the energy storage device and control and monitor the connection and disconnection of the battery rack.

[0004] The energy storage device is used by arranging and connecting a plurality of battery racks in a horizontal direction, in which battery modules, which are an aggregate of a plurality of cells, are arranged and stored in a vertical direction. Of course, the energy storage device may include a battery rack in which battery modules are arranged and stored in a horizontal direction, and the arrangement and storage method of the battery modules and the battery racks may be variously changed.

[0005] Each battery module is stacked and connected vertically and electrically connected to each other in the vertical direction. The battery modules electrically connected in this manner are gathered together to form one rack, and these racks are further electrically connected to each other to form one large battery storage device.

[0006] The battery management system (BMS) includes a module BMS that controls multiple battery cells, a rack BMS for controlling multiple module BMS, a system BMS for controlling multiple rack BMS, and a hub that interfaces the system BMS with a higher-level controller. Each of these components monitors the battery status, transmits the status to the higher-level system, and evenly adjusts charge / discharge cutoff and cell balancing if a problem occurs. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a battery module and an energy storage device including the same, which can improve the efficiency of cell voltage equalization while reducing size and manufacturing costs by equalizing the voltage between two adjacent battery cells among a number of battery cells connected in series via an isolated DC / DC converter. [Means for solving the problem]

[0008] An energy storage device according to an embodiment of the present invention includes a battery module including a number of battery cells connected in series, a number of isolated DC / DC converters electrically connected to each of the plurality of battery cells, and a controller that controls charge and discharge modes of the plurality of isolated DC / DC converters, and each of the plurality of isolated DC / DC converters has one end connected to one battery cell and the other end connected to another adjacent battery cell, and can equalize cell voltages between the two battery cells.

[0009] The plurality of battery cells and the plurality of isolated DC / DC converters may be the same in number, the plurality of battery cells may include a first battery cell, a second battery cell through an Xth battery cell connected in series in sequence, and the plurality of isolated DC / DC converters may include a first isolated DC / DC converter, a second isolated DC / DC converter through an Xth isolated DC / DC converter.

[0010] The first isolated DC / DC converter may have one end electrically connected to the first battery cell and the other end electrically connected to the second battery cell, and the X isolated DC / DC converter may have one end electrically connected to the X battery cell and the other end electrically connected to the first battery cell.

[0011] The controller may compare an average voltage of the multiple battery cells with a voltage of the battery cell electrically connected to one end of the multiple isolated DC / DC converters, and control charging or discharging of the battery cell electrically connected to one end via the isolated DC / DC converter.

[0012] The battery rack includes a plurality of battery modules electrically connected to each other, and a module BMS included in each of the plurality of battery modules includes a plurality of isolated DC / DC converters and a controller, and the controller included in each module BMS can communicate with other module BMSs.

[0013] The average voltage is the average voltage of all battery cells included in the battery rack, and can be calculated by a battery control device included in the battery rack and transmitted to a plurality of module BMSs included in the battery rack via communication.

[0014] The isolated DC / DC converter may include a transformer electrically connected between one end and the other end, a first capacitor connected in parallel to a primary winding of the transformer, a second capacitor connected in parallel to a secondary winding of the transformer, a first switching element electrically connected between the first capacitor and the primary winding of the transformer, and a second switching element electrically connected between the second capacitor and the secondary winding of the transformer.

[0015] The first switching element and the second switching element may be turned on or off under the control of the controller.

[0016] The first switching element has a first electrode electrically connected to a second electrode of the primary winding of the transformer, a second electrode electrically connected to a second electrode of the first capacitor, and a control electrode electrically connected to the controller, and the second switching element has a first electrode electrically connected to a second electrode of the secondary winding of the transformer, a second electrode electrically connected to a second electrode of the second capacitor, and a control electrode electrically connected to the controller, and the first switching element and the second switching element may be transistors having a first electrode as a drain electrode, a second electrode as a collector electrode, and a control electrode.

[0017] The isolated DC / DC converter may include a transformer electrically connected between one end and the other end, a first capacitor connected in parallel to a primary winding of the transformer, a second capacitor electrically connected to a first electrode of a secondary winding of the transformer, a first inductor connected in series with the second capacitor, a third capacitor connected in parallel to the secondary winding of the transformer, a first switching element electrically connected between the first capacitor and the primary winding of the transformer, and a second switching element electrically connected between the secondary winding of the transformer, having a first electrode electrically connected between the second capacitor and the first inductor and a second electrode electrically connected between the secondary winding of the transformer and a third capacitor.

[0018] The first switching element has a first electrode electrically connected to a first electrode of the first capacitor, a second electrode electrically connected to a first electrode of a primary winding of the transformer, and a control electrode electrically connected to the controller, and the second switching element has a first electrode electrically connected between the second capacitor and a first inductor, a second electrode electrically connected to a second electrode of a secondary winding of the transformer, and a control electrode electrically connected to the controller, and the first switching element and the second switching element may be transistors having a first electrode as a drain electrode, a second electrode as a source electrode, and a control electrode.

[0019] A battery module according to an embodiment of the present invention relates to a battery module including a plurality of isolated DC / DC converters electrically connected to each of the plurality of battery cells, and a controller that controls charge and discharge modes of the plurality of isolated DC / DC converters, and each of the plurality of isolated DC / DC converters has one end connected to one battery cell and the other end connected to another adjacent battery cell, and can equalize cell voltages between the two battery cells. Effect of the Invention

[0020] A battery module and an energy storage device thereof according to an embodiment of the present invention can equalize the voltage between two adjacent battery cells in a plurality of battery cells connected in series via an isolated DC / DC converter, thereby improving the efficiency of cell voltage equalization while reducing size and manufacturing costs. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a conceptual diagram showing an energy storage system of the present invention. [Figure 2a] FIG. 2 is an exploded perspective view of a battery rack in the energy storage system shown in FIG. 1. [Figure 2b]FIG. 2 is a front view of a battery rack in the energy storage system shown in FIG. 1. [Diagram 3] FIG. 2 is a structural diagram illustrating the configuration of a cell balancing device of an energy storage system according to various embodiments of the present invention. [Figure 4] FIG. 4 is an example of a circuit diagram of an isolated converter in the cell balancing device of the energy storage system of FIG. 3. [Diagram 5] 4 is another example of a circuit diagram of an isolated converter in the cell balancing device of the energy storage system of FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0023] The embodiments of the present invention are provided to more completely explain the present invention to those having ordinary skill in the art, and the following embodiments can be modified in various other forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to make the present disclosure more faithful and complete, and to fully convey the idea of ​​the present invention to those skilled in the art.

[0024] In the following drawings, the thickness and size of each layer are exaggerated for convenience and clarity of description, and the same reference numerals refer to the same elements in the drawings. As used herein, the term "and / or" includes any one and all combinations of one or more of the listed items. In addition, in this specification, "connected" means not only the case where member A and member B are directly connected, but also the case where member A and member B are indirectly connected with member C interposed between them.

[0025] The terms used in this specification are used to describe specific embodiments and are not intended to limit the present invention. As used in this specification, the singular form may include the plural form unless the context clearly indicates otherwise. Also, as used in this specification, "comprise" and / or "comprising" specify the presence of the mentioned shapes, numbers, steps, operations, members, elements, and / or groups, and do not exclude the presence or addition of one or more other shapes, numbers, operations, members, elements, and / or groups.

[0026] In this specification, terms such as first and second are used to describe various members, parts, regions, layers, and / or portions, but it is clear that these members, parts, regions, layers, and / or portions should not be limited by these terms. These terms are used to distinguish one member, part, region, layer, or portion from another region, layer, or portion. Therefore, a first member, part, region, layer, or portion described in detail below can refer to a second member, part, region, layer, or portion without departing from the spirit of the present invention.

[0027] Space-related terms such as "beneath," "below," "lower," "above," and "upper" are used to facilitate easy understanding of one element or feature from another element or feature shown in the drawings. Such space-related terms are used to facilitate easy understanding of the present invention according to various process or use conditions of the present invention, and are not intended to limit the present invention. For example, if an element or feature in the drawing is turned over, an element described as "below" or "below" becomes "upper" or "above." Therefore, "below" is a concept that encompasses "upper" or "lower."

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

[0029] Herein, parts having similar configurations and operations are designated by the same reference numerals throughout the specification. Furthermore, when a part is said to be electrically coupled to another part, this includes not only the case where the part is directly coupled to another part, but also the case where the part is coupled via another element between them.

[0030] Referring to FIG. 1, a conceptual diagram showing the energy storage system of the present invention is shown, and referring to FIG. 2, a front view and an exploded perspective view of a battery rack of the energy storage system shown in FIG. 1 are shown.

[0031] Referring to Fig. 3, there is shown a structural diagram illustrating the configuration of a cell balancing device of an energy storage system according to various embodiments of the present invention. Hereinafter, the cell balancing device of an energy storage system according to various embodiments of the present invention will be described with reference to Figs. 1 to 3. In addition, the cell balancing device can also be applied to other devices and systems to which a large number of battery cells are applied.

[0032] First, the energy storage device 100 includes at least two or more battery racks 110. Here, the multiple battery racks 110a, 110b, ..., 110x may be electrically connected to each other. Also, the battery racks 110a, 110b, ..., 110x may have high power terminals (positive and negative electrodes) exposed to the outside, and the high power terminals of the battery racks 110a, 110b, ..., 110x may be electrically connected to each other. Also, the multiple battery racks 110a, 110b, ..., 110x may include battery control units (BCUs) 112a, 112b, ..., 112x, respectively.

[0033] Each of the battery racks 110a, 110b, ..., 110x may include a number of battery modules 113 electrically connected to each other. The battery modules 113 included in each of the battery racks 110a, 110b, ..., 110x may be connected in series. For example, the first battery rack 110a may include a rack frame 111 for storing the battery modules 113a, 113b, ..., 113x, and the battery modules 113a, 113b, ..., 113x may be stored in the rack frame 111 and then electrically connected in series. Here, the first battery rack 110a may be stored in the rack frame 111 such that the battery modules 113a, 113b, ..., 113x are vertically stacked. In addition, the first battery rack 110a may store a battery control device 112 at the top end of the rack frame 111.

[0034] Of course, each of the multiple battery racks 110a, 110b, ..., 110x may include multiple battery modules 113a, 113b, ..., 113x and one battery control unit 112. Also, the battery control units (BCUs) of the respective battery racks 110a, 110b, ..., 110x may be connected via a general-purpose communication cable (e.g., CAN).

[0035] The first battery rack 110a may be connected to a high power terminal through fuses and switches. Also, the battery control device 112 included in the first battery rack 110a may control the operation of the fuses and switches according to physical quantities measured in the plurality of battery modules 113a, 113b, ..., 113x, and control that the voltages of the plurality of battery modules 113a, 113b, ..., 113x included in the first battery rack 110a are input / output to the outside via the high power terminal.

[0036] Each of the multiple battery racks 110a, 110b, ..., 110x may be structurally similar to the first battery rack 110a. For convenience of explanation, the following description will focus on the first battery rack 110a among the multiple battery racks 110a, 110b, ..., 110x.

[0037] Also, the multiple battery modules 113a, 113b, ..., 113x may each include multiple battery cells Cell_1, Cell_2, ..., Cell_x, and the multiple battery cells Cell_1, Cell_2, ..., Cell_x included in each battery module 113a, 113b, ..., 113x may be electrically connected in series. For example, the first battery module 113a may further include a module BMS 113am. The module BMS 113am may measure and / or control physical quantities (such as voltages) of the multiple battery cells Cell_1, Cell_2, ..., Cell_x included in the battery module 113, and transmit the result data to a battery control unit (BCU) in the event of an abnormality.

[0038] Each of the multiple battery modules 113a, 113b, ..., 113x may be structurally similar to the first battery module 113a. For convenience of explanation, the following description will focus on the first battery module 113a among the multiple battery modules 113a, 113b, ..., 113x.

[0039] The module BMS113am included in each of the first battery modules 113a can equalize cell voltages of a number of battery cells Cell_1, Cell_2, ..., Cell_x included in the first battery module 113a. In FIG. 3, the module BMS113am shows only a cell voltage equalizer, and the module BMS113am may further include a configuration for measuring and / or controlling physical quantities of the battery cells Cell_1, Cell_2, ..., Cell_x. Hereinafter, for convenience of explanation, the module BMS113am will be described as a cell voltage equalizer.

[0040] The configuration and operation of the cell voltage equalizer 113am will be described in detail below.

[0041] The module BMS 113am of the first battery module 113a may be connected to the module BMSs included in the multiple battery modules 113a, 113b, ..., 113x via a general-purpose communication cable. The module BMS 113am of the first battery module 113a may be connected to the battery control device 112a of the first battery rack 110a via a general-purpose communication cable. The battery control device 112 can manage and control the module BMSs of the multiple battery modules 113a, 113b, ..., 113x included in the first battery rack 110a.

[0042] Furthermore, in the energy storage device 100, the battery control devices 112 included in the multiple battery racks 110a, 110b, ..., 110x may all be connected to the system BMS 120 via general-purpose communication cables. The system BMS 120 can manage and control the battery control devices 112a included in the multiple battery racks 110a, 110b, ..., 110x. Such a system BMS 120 may be a master BMS, but the present invention is not limited thereto.

[0043] The cell voltage equalizer 113am may include the same number of isolated DC / DC converters IC1, IC2, ..., ICx as the number of battery cells Cell_1, Cell_2, ..., Cell_x. Also, the multiple battery cells Cell_1, Cell_2, ..., Cell_x may be electrically connected to the multiple isolated DC / DC converters IC1, IC2, ..., ICx, respectively.

[0044] For example, the battery may include a first isolated DC / DC converter IC1 electrically connected to the first battery cell Cell_1, a second isolated DC / DC converter IC2 electrically connected to the second battery cell Cell_2, and an Xth isolated DC / DC converter ICx electrically connected to the Xth battery cell Cell_x.

[0045] Here, the multiple battery cells Cell_1, Cell_2, ..., Cell_x may be sequentially connected in series. As an example, the negative electrode of the first battery cell Cell_1 may be electrically connected to the positive electrode of the second battery cell Cell_2, the negative electrode of the second battery cell Cell_2 may be electrically connected to the positive electrode of the third battery cell Cell_3, and the negative electrode of the X-1th battery cell Cell_x-1 may be electrically connected to the positive electrode of the Xth battery cell Cell_x. As an example, when the multiple battery cells Cell_1, Cell_2, ..., Cell_x connected in series are 12 in number, the Xth battery cell Cell_x may be the 12th battery cell Cell_12. Also, the multiple battery cells Cell_1, Cell_2, ..., Cell_x connected in series may be three or more in number.

[0046] In addition, the first isolated DC / DC converter IC1 may have one terminal A1, A1' electrically connected to the positive electrode and negative electrode of the first battery cell Cell_1, and the other terminal B1, B1' electrically connected to the positive electrode and negative electrode of the second battery cell Cell_2, the positive electrode of which is connected to the negative electrode of the first battery cell Cell_1. That is, the first isolated DC / DC converter IC1 may equalize the cell voltages between the first battery cell Cell_1 and the second battery cell Cell_2 by adjusting the voltage between the first battery cell Cell_1 and the second battery cell Cell_2.

[0047] The second isolated DC / DC converter IC2 may have one terminal A2, A2' electrically connected to the positive electrode and negative electrode of the second battery cell Cell_2, and the other terminal B2, B2' electrically connected to the positive electrode and negative electrode of a third battery cell Cell_3, the positive electrode of which is connected to the negative electrode of the second battery cell Cell_2. That is, the second isolated DC / DC converter IC2 may equalize the cell voltages between the second battery cell Cell_2 and the third battery cell Cell_3 by adjusting the voltage between the second battery cell Cell_2 and the third battery cell Cell_3.

[0048] Also, the Xth isolated DC / DC converter ICx may have one end AX, AX' electrically connected to the positive electrode and negative electrode of the Xth battery cell Cell_x, and the other end BX, BX' electrically connected to the positive electrode and negative electrode of the first battery cell Cell_1, respectively. Here, the Xth isolated DC / DC converter ICx may be the last battery cell among the multiple battery cells Cell_1, Cell_2, ..., Cell_x connected in series, and the other end BX, BX' may be electrically connected to the positive electrode and negative electrode of the first battery cell Cell_1, which is the first cell. That is, the Xth isolated DC / DC converter ICx may equalize the cell voltage between the X-1st battery cell Cell_x-1 and the Xth battery cell Cell_x by adjusting the voltage between the X-1st battery cell Cell_x-1 and the Xth battery cell Cell_x.

[0049] The multiple isolated DC / DC converters IC1, IC2, ..., ICx can equalize the cell voltages between two adjacent battery cells among the multiple battery cells Cell_1, Cell_2, ..., Cell_x.

[0050] The first isolated DC / DC converter IC1 can be controlled by the controller Co to discharge or charge the first battery cell Cell_1 electrically connected to one end A1, A1'. Of course, the controller Co is electrically connected to a plurality of isolated DC / DC converters IC1, IC2, ..., ICx and can control the charging or discharging of the plurality of isolated DC / DC converters IC1, IC2, ..., ICx. In addition, when the first battery cell Cell_1 is discharged by the first isolated DC / DC converter IC1, the discharge voltage of the first battery cell Cell_1 can charge the second battery cell Cell_2 via the first isolated DC / DC converter IC1.

[0051] The controller Co compares an average voltage Va of the multiple battery cells Cell_1, Cell_2, ..., Cell_x with the voltage of the first battery cell Cell_1 electrically connected to one end A1, A1' of the first isolated DC / DC converter IC1, and charges the first battery cell Cell_1 if the voltage of the first battery cell Cell_1 is lower than the average voltage Va, and discharges the first battery cell Cell_1 if the voltage of the first battery cell Cell_1 is higher than the average voltage Va.

[0052] Here, the average voltage Va may be an average voltage Va of a number of battery cells Cell_1, Cell_2, ..., Cell_x included in the first battery module 113a. Furthermore, the average voltage Va may be an average voltage of all battery cells included in the entire first battery rack 110a, which is an average of the average voltages of not only the first battery module 113a but also the other battery modules 113b, ..., 113x. Here, the module BMS 113am of the first battery module 113a may receive the average voltage through communication with the module BMS of the other battery modules 113b, ..., 113x, or may receive the average voltage of the battery cells included in each of the battery modules 113a, 113b, ..., 113x from the module BMS included in each of the multiple battery modules 113a, 113b, ..., 113x included in the first battery rack 110a in a battery control unit (BCU) to calculate the average voltage of all battery cells included in the first battery rack 110a. Of course, the battery control unit (BCU) can transmit the calculated average voltage through communication with the module BMS 112 included in each of the multiple battery modules 113a, 113b, ..., 113x. As another example, the battery control unit (BCU) can measure the voltages of all the battery cells included in the battery rack 110, calculate an average cell voltage, and transmit it to the module BMS included in the battery rack 110.

[0053] 4, an example of a circuit diagram of an isolated DC / DC converter IC in the cell balancing device of the energy storage system of FIG. 3 is shown. As shown in FIG. 4, the cell balancing device may include a first capacitor C1 connected in parallel to one end A, A', a second capacitor C2 connected in parallel to the other end B, B', a transformer TR1 interposed between the one end A, A' and the other end B, B', a first switching element Q1 interposed between a primary winding n1 of the transformer TR1 and the first capacitor C1, and a second switching element Q2 interposed between a secondary winding n2 of the transformer TR1 and the second capacitor C2. Here, the one end A, A' and the other end B, B' may be electrically connected to the positive and negative electrodes of the battery cells. For example, when the isolated DC / DC converter is a first isolated DC / DC converter IC1, one terminal A, A' may be connected between the positive and negative electrodes of the first battery cell Cell_1, and the other terminal B, B' may be connected between the positive and negative electrodes of the second battery cell Cell_2.

[0054] The first capacitor C1 may have a first electrode electrically connected to the first electrode A of one end A, A', and a second electrode electrically connected to the second electrode A' of one end A, A' and the second electrode of the first switching element Q1.

[0055] The first switching element Q1 may have a first electrode electrically connected to a second electrode of the primary winding n1 of the transformer TR1, and a second electrode electrically connected to the second electrode of the first capacitor C1 and the second electrode A' of one end A, A'. The first switching element Q1 may have a control electrode electrically connected to the controller Co and may be turned on or off by a signal applied from the controller Co. Such a first switching element Q1 may be a transistor FET having a first electrode as a drain electrode, a second electrode as a source electrode, and a control electrode.

[0056] The second switching element Q2 may have a first electrode electrically connected to a second electrode of the secondary winding n2 of the transformer TR1, and a second electrode electrically connected to the second electrode of the second capacitor C2 and the second electrode B' of the other end B, B'. The second switching element Q2 may have a control electrode electrically connected to the controller Co and may be turned on or off by a signal applied from the controller Co. The second switching element Q2 may be a transistor FET having a first electrode as a drain electrode, a second electrode as a source electrode, and a control electrode.

[0057] The second capacitor C2 may have a first electrode electrically connected to the first electrode B of the other end B, B' and a first electrode of the secondary winding n2 of the transformer TR1, and a second electrode electrically connected to the second electrode B' of the other end B, B' and a second electrode of the second switching element Q2.

[0058] In this isolated DC / DC converter IC, when the first switching element Q1 is turned on, the battery cell connected to one end A, A' is discharged. When the first switching element Q1 is turned on, the battery cell connected to one end A, A' becomes a voltage source, and a voltage corresponding to the voltage of the battery cell is applied to the primary winding n1 of the transformer TR1. At this time, the current of the transformer TR1 increases. Also, a voltage corresponding to the ratio of the number of turns is applied to the secondary winding n2 of the transformer TR1. However, when the second switching element Q2 is in an off state, no current flows due to the diode D2 of the second switching element Q2.

[0059] At this time, when the first switching element Q1 is turned off, a current flows through the secondary winding n2 and the diode D2 of the second switching element Q2 due to the magnetic flux of the primary winding n1 of the transformer TR1. At this time, the second capacitor C2 is charged, and the current flowing through the transformer TR1 gradually decreases.

[0060] That is, in the isolated DC / DC converter IC, when the first switching element Q1 is turned on, the energy stored in the transformer TR1 is transferred to and stored in the second capacitor C2. In addition, the first capacitor C1 and the second capacitor C2 smooth the current passing through the transformer TR1 during charging and discharging.

[0061] Here, in the isolated DC / DC converter IC, one battery cell is electrically connected to each of the primary winding n1 and the secondary winding n2 of the transformer TR1, so that the first switching element Q1 and the second switching element Q2 can have a switch withstand voltage corresponding to one battery cell. Generally, the size and price of a switching element can increase as the switch withstand voltage increases, but since the first switching element Q1 and the second switching element Q2 only need to have a switch withstand voltage corresponding to one battery cell, it is possible to prevent an increase in size and price.

[0062] In addition, in the isolated DC / DC converter IC, when the battery cell connected to one end A, A' is charged, it is the same as when the battery cell connected to the other end B, B' is discharged, so the operations of the first switching element Q1 and the second switching element Q2 may be reversed.

[0063] In this isolated DC / DC converter IC, when the voltage of the battery cell connected to one end A, A' is higher than the average voltage Va, the first switching element Q1 is turned on to discharge the battery cell. At this time, the voltage discharged from the battery cell connected to one end A, A' can be transferred to the battery cell connected to the other end B, B' of the isolated DC / DC converter IC.

[0064] Conversely, the isolated DC / DC converter IC can charge the battery cells connected to one end A, A' by turning on the second switching element Q2 when the voltage of the battery cells connected to one end A, A' is lower than the average voltage Va. In this case, the isolated DC / DC converter IC can transfer the voltage discharged from the battery cells connected to the other end B, B' to the battery cells connected to one end A, A'.

[0065] That is, the energy storage device 100 performs cell voltage equalization through charging and discharging between adjacent cells, thereby preventing a decrease in efficiency caused by discharging through a resistor for cell voltage equalization. Also, the energy storage device 100 performs equalization between one battery cell and one adjacent battery cell through charging and discharging, thereby preventing an increase in size and cost for improving switch voltage resistance characteristics that occurs when directly equalizing cells with a plurality of battery cells connected in series.

[0066] Also, referring to Fig. 5, another example of a circuit diagram of an isolated DC / DC converter IC in the cell balancing device of the energy storage system of Fig. 3 is shown. As shown in Fig. 5, the cell balancing device may include a first capacitor C1 connected in parallel to one end A, A', a third capacitor C3 connected in parallel to the other end B, B', a transformer TR1 interposed between one end A, A' and the other end B, B', a first switching element Q1 interposed between a primary winding n1 of the transformer TR1 and the first capacitor C1, a second capacitor C2 and a first inductor L1 interposed between a secondary winding n2 of the transformer TR1 and the third capacitor C3, and a second switching element Q2 connected in parallel to the secondary winding n2 of the transformer TR1 and the third capacitor C3. Here, the one end A, A' and the other end B, B' may be electrically connected to the positive and negative electrodes of the battery cells. For example, when the isolated DC / DC converter is a first isolated DC / DC converter IC1, one terminal A, A' may be connected between the positive and negative electrodes of the first battery cell Cell_1, and the other terminal B, B' may be connected between the positive and negative electrodes of the second battery cell Cell_2.

[0067] The first capacitor C1 may have a first electrode electrically connected to the first electrode A of one end A, A' and the first electrode of the first switching element Q1, and a second electrode electrically connected to the second electrode A' of one end A, A' and the second electrode of the primary winding n1 of the transformer TR1.

[0068] The first switching element Q1 may have a first electrode electrically connected to the first electrode A of one end A, A' and a first electrode of the first capacitor C1, and a second electrode electrically connected to a first electrode of the primary winding n1 of the transformer TR1. The first switching element Q1 may have a control electrode electrically connected to a controller Co and may be turned on or off by a signal applied from the controller Co. Such a first switching element Q1 may be a transistor FET having a first electrode as a drain electrode, a second electrode as a source electrode, and a control electrode.

[0069] The second capacitor C2 may have a first electrode electrically connected to a first electrode of the secondary winding n2 of the transformer TR1, and a second electrode electrically connected to a first electrode of the second switching element Q2 and a first electrode of the first inductor L1.

[0070] The second switching element Q2 may have a first electrode electrically connected to the second electrode of the second capacitor C2 and the first electrode of the first inductor L1, and a second electrode electrically connected to the second electrode of the secondary winding n2 of the transformer TR1 and the second electrode of the third capacitor C3. The second switching element Q2 may have a control electrode electrically connected to the controller Co and may be turned on or off by a signal applied from the controller Co. The second switching element Q2 may be a transistor having a first electrode as a drain electrode, a second electrode as a source electrode, and a control electrode.

[0071] The third capacitor C3 may have a first electrode electrically connected to the second electrode of the first inductor L1 and the first electrode of the other end B, B', and a second electrode electrically connected to the second electrode of the second switching element Q2, the second electrode of the secondary winding n2 of the transformer TR1, and the second electrode of the other end B, B'.

[0072] The first inductor L1 may have a first electrode electrically connected to the second electrode of the second capacitor C2 and the first electrode of the second switching element Q2, and a second electrode electrically connected to the first electrode of the third capacitor C3 and the first electrode B of the other end B, B'.

[0073] In this isolated DC / DC converter IC, when the first switching element Q1 is turned on, the battery cell connected to one end A, A' is discharged. When the first switching element Q1 is turned on, the battery cell connected to one end A, A' becomes a voltage source, and a voltage corresponding to the voltage of the battery cell is applied to the primary winding n1 of the transformer TR1. A voltage corresponding to the ratio of the number of turns is applied to the secondary winding n2 of the transformer TR1. A voltage obtained by adding the voltage of the second capacitor C2 to the voltage of the secondary winding n2 of the transformer TR1 is applied to the first inductor L1 and the third capacitor C3, and the resulting current flows to the third capacitor C3, thereby transferring power to the other end B, B'.

[0074] At this time, when the first switching element Q1 is turned off, a current flows through the secondary winding n2 and the diode D2 of the second switching element Q2 due to the magnetic flux caused by the excitation current of the transformer TR1, and charges the second capacitor C2. At the same time, the current that flowed through the first inductor L1 continues to flow, so that the current that flowed through the third capacitor C3 and the diode D2 of the second switching element Q2 gradually decreases.

[0075] That is, in the isolated DC / DC converter IC, when the first switching element Q1 is turned on, the energy stored in the transformer TR1 is transferred to and stored in the third capacitor C3. In addition, the first capacitor C1 and the third capacitor C3 smooth the current passing through the transformer TR1 during charging and discharging.

[0076] In this isolated DC / DC converter IC, when the voltage of the battery cell connected to one end A, A' is higher than the average voltage Va, the first switching element Q1 turns on / off to discharge the battery cell. At this time, the voltage discharged from the battery cell connected to one end A, A' of the isolated DC / DC converter IC can charge the battery cell connected to the other end B, B'.

[0077] Conversely, the isolated DC / DC converter IC can charge the battery cells connected to one end A, A' by turning on / off the second switching element Q2 when the voltage of the battery cells connected to one end A, A' is lower than the average voltage Va. In this case, the isolated DC / DC converter IC can charge the battery cells connected to one end A, A' with the voltage discharged from the battery cells connected to the other end B, B'.

[0078] That is, the battery module 113 and the energy storage device 100 including the same perform cell voltage equalization through charging and discharging between adjacent cells, thereby preventing a decrease in efficiency caused by discharging through a resistor for cell voltage equalization. Also, the battery module 113 and the energy storage device 100 including the same perform equalization between one battery cell and one adjacent battery cell through charging and discharging, thereby preventing an increase in size and cost for improving switch voltage resistance characteristics that occurs when directly equalizing cells with a plurality of battery cells connected in series.

[0079] What has been described above is merely one embodiment for implementing the energy storage device according to the present invention, and the present invention is not limited to the above-described embodiment. As claimed in the following claims, it can be said that the technical spirit of the present invention is within the scope of the invention to the extent that anyone with ordinary knowledge in the field to which the invention belongs can make various modifications without departing from the gist of the present invention. [Explanation of symbols]

[0080] 100 Energy Storage Device 110 Battery Rack 110a Battery Rack No. 1 111 Rack Frame 112 Battery control device 113 Battery Module 113a First Battery Module 113am Cell voltage equalizer

Claims

1. A number of battery cells connected in series; a plurality of isolated DC / DC converters electrically connected to the plurality of battery cells, respectively; and a controller for controlling charge and discharge modes of the plurality of isolated DC / DC converters, Each of the multiple isolated DC / DC converters has one end connected to one battery cell and the other end connected to another adjacent battery cell, and equalizes cell voltages between the two battery cells; The energy storage device, wherein the number of battery cells and the number of isolated DC / DC converters are the same.

2. The energy storage device of claim 1, wherein the multiple battery cells are a first battery cell, a second battery cell to an Xth battery cell connected in series in sequence, and the multiple isolated DC / DC converters include a first isolated DC / DC converter, a second isolated DC / DC converter to an Xth isolated DC / DC converter.

3. the first isolated DC / DC converter has one end electrically connected to the first battery cell and another end electrically connected to the second battery cell; The energy storage device of claim 2 , wherein one end of the X isolated DC / DC converter is electrically connected to the X battery cell and the other end of the X isolated DC / DC converter is electrically connected to the first battery cell.

4. 3. The energy storage device of claim 2, wherein the controller compares an average voltage of the multiple battery cells with a voltage of the battery cell electrically coupled to one end of the multiple isolated DC / DC converters, and controls charging or discharging of the battery cell electrically coupled to one end via the isolated DC / DC converter.

5. The battery rack includes a plurality of battery modules, the battery modules being electrically connected to each other; The module BMS included in each of the plurality of battery modules includes a plurality of isolated DC / DC converters and a controller; The energy storage device of claim 4 , wherein a controller included in each module BMS communicates with the other module BMSs.

6. 6. The energy storage device according to claim 5, wherein the average voltage is an average voltage of all battery cells included in the battery rack, and is calculated by a battery control device included in the battery rack and transmitted to a plurality of module BMSs included in the battery rack via communication.

7. The isolated DC / DC converter comprises: a transformer electrically connected between one end and the other end; a first capacitor connected in parallel with a primary winding of the transformer; a second capacitor connected in parallel with the secondary winding of the transformer; a first switching element electrically connected between the first capacitor and a primary winding of the transformer; 10. The energy storage device of claim 1 , further comprising: a second switching element electrically coupled between the second capacitor and a secondary winding of the transformer.

8. The energy storage device of claim 7 , wherein the first switching element and the second switching element are turned on or off under the control of the controller.

9. the first switching element has a first electrode electrically connected to a second electrode of the primary winding of the transformer, a second electrode electrically connected to a second electrode of the first capacitor, and a control electrode electrically connected to the controller; the second switching element has a first electrode electrically connected to a second electrode of the secondary winding of the transformer, a second electrode electrically connected to a second electrode of the second capacitor, and a control electrode electrically connected to the controller; The energy storage device of claim 7 , wherein the first switching element and the second switching element are transistors having a first electrode as a drain electrode, a second electrode as a source electrode, and a control electrode.

10. The isolated DC / DC converter comprises: a transformer electrically connected between one end and the other end; a first capacitor connected in parallel with a primary winding of the transformer; a second capacitor electrically connected to a first electrode of the secondary winding of the transformer; a first inductor connected in series with the second capacitor; a third capacitor connected in parallel with the secondary winding of the transformer; a first switching element electrically connected between the first capacitor and a primary winding of the transformer; a second switching element having a first electrode electrically connected between the second capacitor and a first inductor and a second electrode electrically connected between a secondary winding of the transformer and a third capacitor.

11. the first switching element has a first electrode electrically connected to a first electrode of the first capacitor, a second electrode electrically connected to a first electrode of the primary winding of the transformer, and a control electrode electrically connected to the controller; the second switching element has a first electrode electrically connected between the second capacitor and the first inductor, a second electrode electrically connected to a second electrode of the secondary winding of the transformer, and a control electrode electrically connected to the controller; The energy storage device of claim 10 , wherein the first switching element and the second switching element are transistors having a first electrode as a drain electrode, a second electrode as a source electrode, and a control electrode.

12. A number of battery cells connected in series; a plurality of isolated DC / DC converters electrically connected to the plurality of battery cells, respectively; and a controller for controlling charge and discharge modes of the plurality of isolated DC / DC converters, Each of the multiple isolated DC / DC converters has one end connected to one battery cell and the other end connected to another adjacent battery cell, and equalizes cell voltages between the two battery cells; The battery module, wherein the number of the battery cells and the number of the isolated DC / DC converters are the same.

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