Energy storage system and method for performing voltage balancing between serially connected energy storage modules

Abstract

Disclosed are an energy storage system and a method for performing voltage balancing between serially connected energy storage modules through direct communication between the energy storage modules without configuring a separate circuit for voltage balancing. The energy storage system according to an aspect of the present invention includes: a plurality of energy storage modules connected in series and each including a plurality of unit cells; and voltage balancing devices that are installed in the respective energy storage modules and communicate with each other to perform voltage balancing between the plurality of energy storage modules.

Description

Energy storage system and method for performing voltage balancing between series-connected energy storage modules

[0001] This application claims priority to Korean Patent Application No. 10-2023-0122087, filed September 13, 2023, the entire disclosure of which is incorporated by reference into this application.

[0002] The present invention relates to an energy storage system and method for performing voltage balancing between energy storage modules, and more particularly, to an energy storage system and method for performing voltage balancing between energy storage modules connected in series.

[0003] Typically, energy storage modules comprise multiple unit cells connected in series to achieve high voltages. These energy storage modules are typically implemented as a pack, with multiple units connected in series, rather than as a single module. Appropriate voltage balancing is essential in these packs or energy storage modules.

[0004] Voltage balancing refers to the process of detecting energy storage modules exhibiting voltages higher or lower than the reference voltage and adjusting them to the reference voltage by discharging or charging them. If voltage balancing is not properly performed, cell deterioration accelerates, shortening their lifespan and compromising the stability and reliability of the entire system.

[0005] Conventionally, to balance the voltage of an energy storage system comprised of energy storage modules, a voltage balancing device is installed in each energy storage module, and a controller controls each voltage balancing device to compensate for voltage deviations between the energy storage modules using passive or active balancing technology. To control each voltage balancing device with a controller, a separate circuit is required to connect each voltage balancing device to the controller that controls them. This separate circuit configuration for voltage balancing increases the size of the printed circuit board, increases circuit complexity, and increases the likelihood of defects.

[0006] The present invention has been proposed to solve the above-described problem, and its purpose is to provide an energy storage system and method that performs voltage balancing between energy storage modules by direct communication between energy storage modules connected in series without configuring a separate circuit for voltage balancing.

[0007] According to one aspect, the energy storage system includes a plurality of energy storage modules, each of which includes a plurality of unit cells and is connected in series; and a voltage balancing device installed in each energy storage module and communicating with each other to perform voltage balancing between the plurality of energy storage modules.

[0008] The voltage balancing device may include a voltage measuring unit that measures the voltage value of an energy storage module on which the voltage balancing device is installed; a communication unit that communicates with other voltage balancing devices installed in other energy storage modules to receive voltage values ​​of other energy storage modules; and a processing unit that performs voltage balancing of the energy storage module on which the voltage balancing device is installed based on the measured voltage value and the received voltage values ​​of other energy storage modules.

[0009] The above communication unit transmits and receives voltage values ​​through a CAN (Controller Area Network) communication message with the other voltage balancing devices, and in the ID field of the CAN communication message, the serially connected energy storage modules have the same node ID, the parallel connected energy storage modules have different node IDs, and each energy storage module may have different module IDs.

[0010] The above processing unit can perform voltage balancing of the energy storage module in which the voltage balancing device is installed when the measured voltage value is greater than the average voltage value of other energy storage modules by a predetermined value or more.

[0011] The above processing unit can perform voltage balancing of an energy storage module in which a voltage balancing device is installed when the difference between the largest voltage value and the smallest voltage value among the voltage values ​​of other energy storage modules is greater than a predetermined threshold value and the measured voltage value is greater than the average of the largest voltage value and the smallest voltage value.

[0012] The above processing unit can perform voltage balancing of the energy storage module in which the voltage balancing device is installed when the measured voltage value is higher than the alarm reference value.

[0013] The above processing unit can perform voltage balancing between unit cells within the energy storage module after voltage balancing of the energy storage module in which the voltage balancing device is installed is completed.

[0014] The voltage measuring unit measures the voltage values ​​of the unit cells, and the processing unit can perform voltage balancing of the specific unit cell when the voltage value of the specific unit cell is greater than the average voltage value of other unit cells by a predetermined value or more.

[0015] The voltage measuring unit measures the voltage values ​​of the unit cells, and the processing unit can perform voltage balancing of the specific unit cell when the difference between the largest voltage value and the smallest voltage value among the voltage values ​​of unit cells other than the specific unit cell is greater than a predetermined threshold value, and the voltage value of the specific unit cell is greater than the average of the largest voltage value and the smallest voltage value.

[0016] The voltage measuring unit measures the voltage values ​​of unit cells, and the processing unit can perform voltage balancing of a specific unit cell when the voltage value of the specific unit cell is greater than or equal to an alarm reference value.

[0017] According to another aspect, in an energy storage system including a plurality of energy storage modules each including a plurality of unit cells and connected in series, a voltage balancing method of each voltage balancing device installed in each energy storage module includes a step of performing voltage balancing between the plurality of energy storage modules by mutually communicating with voltage balancing devices installed in other energy storage modules.

[0018] The step of performing the above may include: measuring a voltage value of an energy storage module in which the voltage balancing device is installed; communicating with other voltage balancing devices installed in other energy storage modules to receive voltage values ​​of other energy storage modules; and performing voltage balancing of the energy storage module in which the voltage balancing device is installed based on the measured voltage value and the received voltage values ​​of other energy storage modules.

[0019] The receiving step receives a voltage value through a CAN (Controller Area Network) communication message with the other voltage balancing devices, and in the ID field of the CAN communication message, the serially connected energy storage modules may have the same node ID and each energy storage module may have a different module ID.

[0020] The step of performing voltage balancing of the energy storage module in which the voltage balancing device is installed may perform voltage balancing of the energy storage module in which the voltage balancing device is installed when the measured voltage value is greater than the average voltage value of other energy storage modules by a predetermined value or more.

[0021] The step of performing voltage balancing of the energy storage module in which the voltage balancing device is installed may perform voltage balancing of the energy storage module in which the voltage balancing device is installed when the difference between the largest voltage value and the smallest voltage value among the voltage values ​​of other energy storage modules is greater than a predetermined threshold value and the measured voltage value is greater than the average of the largest voltage value and the smallest voltage value.

[0022] The above voltage balancing method may further include a step of performing voltage balancing of an energy storage module in which the voltage balancing device is installed when the measured voltage value is equal to or higher than an alarm reference value.

[0023] The above voltage balancing method may further include a step of performing voltage balancing between unit cells within the energy storage module after voltage balancing of the energy storage module in which the voltage balancing device is installed is completed.

[0024] The step of performing voltage balancing between the unit cells may include: a step of measuring voltage values ​​of the unit cells; and a step of performing voltage balancing of the specific unit cell when the voltage value of the specific unit cell is greater than the average voltage value of other unit cells by a predetermined value or more.

[0025] The step of performing voltage balancing between the unit cells may include: measuring voltage values ​​of the unit cells; and performing voltage balancing of the specific unit cell when a difference between the largest voltage value and the smallest voltage value among voltage values ​​of unit cells other than the specific unit cell is greater than a predetermined threshold value and the voltage value of the specific unit cell is greater than an average of the largest voltage value and the smallest voltage value.

[0026] The step of performing voltage balancing between the unit cells includes: a step of measuring voltage values ​​of the unit cells; and when the voltage value of a specific unit cell is equal to or greater than an alarm reference value, voltage balancing of the specific unit cell can be performed.

[0027] According to the present invention, voltage balancing between energy storage modules can be achieved through direct communication between energy storage modules connected in series without configuring a separate circuit for voltage balancing.

[0028] FIG. 1 is a drawing showing the configuration of an energy storage system according to one embodiment of the present invention.

[0029] FIG. 2 is an example illustrating a 29-bit long ID field of an extended CAN according to one embodiment of the present invention.

[0030] FIG. 3 is a drawing showing the configuration of a voltage balancing device according to one embodiment of the present invention.

[0031] FIG. 4 is a flowchart illustrating a voltage balancing method between energy storage modules according to one embodiment of the present invention.

[0032] FIG. 5 is a flowchart illustrating a method for balancing voltage between cells in an energy storage module according to one embodiment of the present invention.

[0033] Figure 6 is a drawing showing an experimental example of performing voltage balancing according to one embodiment of the present invention.

[0034] Hereinafter, the embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Regardless of the drawing numbers, identical or similar components will be given the same reference numbers, and redundant descriptions thereof will be omitted. The suffix "part" used for components in the following description is given or used interchangeably only for the convenience of writing the specification, and does not in itself have a distinct meaning or role. In addition, when describing the embodiments disclosed in this specification, if it is determined that a specific description of a related known technology may obscure the gist of the embodiments disclosed in this specification, a detailed description thereof will be omitted. In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention.

[0035] Terms that include ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another.

[0036] Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as "comprises" or "have" are intended to indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but should be understood not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0037] FIG. 1 is a diagram showing the configuration of an energy storage system according to one embodiment of the present invention. Referring to FIG. 1, the energy storage system according to the present embodiment includes a plurality of energy storage modules (110-1, 110-2, ..., 110-n) connected in series, and each energy storage module (110-1, 110-2, ..., 110-n) includes a plurality of series-connected unit cells and a voltage balancing device (120-1, 120-2, ..., 120-n). In the present embodiment, only the plurality of series-connected energy storage modules (110-1, 110-2, ..., 110-n) are illustrated and described, but the present invention is not limited thereto, and the plurality of series-connected energy storage modules (110-1, 110-2, ..., 110-n) may be provided in multiple sets and connected in parallel between each set to implement the energy storage system.

[0038] A unit cell refers to an energy storage device such as a rechargeable secondary battery, an electrolytic capacitor, or an ultracapacitor having characteristics intermediate between an electrolytic capacitor and a secondary battery. Within each energy storage module (110-1, 110-2, ..., 110-n), adjacent unit cells are electrically connected in series between positive and negative poles via busbars, etc. The number of unit cells within each energy storage module (110-1, 110-2, ..., 110-n) and the number of energy storage modules (110-1, 110-2, ..., 110-n) can be determined according to the operating voltage required in the application to be applied.

[0039] Voltage balancing devices (120-1, 120-2,..., 120-n) installed in each energy storage module (110-1, 110-2,..., 110-n) are connected to each other to perform communication and are also connected to all unit cells installed in the energy storage modules (110-1, 110-2,..., 110-n) to perform voltage balancing between the energy storage modules (110-1, 110-2,..., 110-n) and voltage balancing between cells in the energy storage modules (110-1, 110-2,..., 110-n). Preferably, the voltage balancing devices (120-1, 120-2,..., 120-n) perform CAN (Controller Area Network) communication. Here, the balancing is generally passive balancing.

[0040] Conventionally, in order to balance the voltage of an energy storage system composed of energy storage modules, a voltage balancing device is installed in each energy storage module, and each voltage balancing device is controlled by a controller, so a separate circuit is required for connecting each voltage balancing device and the controller that controls them. However, in the present invention, since the voltage balancing devices (120-1, 120-2, ..., 120-n) perform voltage balancing by performing CAN communication, a controller for controlling the voltage balancing devices (120-1, 120-2, ..., 120-n) is not required, and therefore, a separate circuit for connecting the voltage balancing devices (120-1, 120-2, ..., 120-n) and the controller is not required.

[0041] In addition, conventionally, voltage balancing is performed by connecting a resistor to the positive and / or negative poles of an energy storage module for voltage balancing between energy storage modules, but in the present invention, voltage balancing between modules and voltage balancing between cells is performed by controlling the on / off of the balancing channel of each cell in the energy storage module (110-1, 110-2, ..., 110-n) without using a separate external resistor.

[0042] CAN communication is a message-based protocol, and data is transmitted and received in the form of frames. Each frame is identified by an ID field, which is 11 bits long in standard CAN and 29 bits long in extended CAN. In the present invention, the ID field of CAN communication is used to determine the priority of a message and whether or not to receive a message. In this embodiment, the 29-bit extended CAN is taken as an example. FIG. 2 is an example illustrating a 29-bit ID field of the extended CAN according to an embodiment of the present invention. Referring to FIG. 2, the ID field is composed of a 3-bit service ID field, a 5-bit module ID field, a 13-bit node ID field, and an 8-bit extension ID field. In this embodiment, serially connected energy storage modules (110-1, 110-2, ..., 110-n) are set to use the same node ID. That is, the voltage balancing devices (120-1, 120-2,..., 120-n) of the serially connected energy storage modules (110-1, 110-2,..., 110-n) communicate using the same node ID and identify the voltage balancing devices (120-1, 120-2,..., 120-n) of other energy storage modules (110-1, 110-2,..., 110-n) based on the module ID. Meanwhile, when the energy storage modules (110-1, 110-2,..., 110-n) are connected in parallel, the energy storage modules (110-1, 110-2,..., 110-n) are set to use different node IDs.

[0043] Voltage balancing devices (120-1, 120-2,..., 120-n) installed in each energy storage module (110-1, 110-2,..., 110-n) are connected to each other to perform communication and perform voltage balancing between the energy storage modules (110-1, 110-2,..., 110-n) and voltage balancing between cells within the energy storage modules (110-1, 110-2,..., 110-n). Since the voltage balancing operation of each voltage balancing device (120-1, 120-2,..., 120-n) is performed independently and identically, the following description will be based on the voltage balancing device (120-1) of the first energy storage module (110-1).

[0044] FIG. 3 is a diagram showing the configuration of a voltage balancing device (120-1) according to one embodiment of the present invention. Referring to FIG. 3, the voltage balancing device (120-1) includes a communication unit (121), a voltage measurement unit (122), and a processing unit (123). The processing unit (123) may be, but is not limited to, a microprocessor, and may include a processing circuit such as a DSP, an ASIC, an FPGA, and may operate according to a program stored in a memory. Hereinafter, voltage balancing between energy storage modules (110-1, 110-2, ..., 110-n) will be first set, and then voltage balancing between cells within one energy storage module (110-1) will be described.

[0045] First, the voltage measuring unit (122) of the voltage balancing device (120-1) measures the voltage value of the energy storage module (110-1) in which it is installed. Then, the processing unit (123) checks whether the voltage value of the energy storage module (110-1) measured by the voltage measuring unit (122) is equal to or higher than the alarm reference value. If the voltage value of the energy storage module (110-1) is equal to or higher than the alarm reference value, the processing unit (123) performs passive balancing on all unit cells installed in the energy storage module (110-1) to perform module voltage balancing. That is, the processing unit (123) turns on the balancing channels of all unit cells in the energy storage module (110-1) so that the voltage value of the energy storage module (110-1) is lowered to the reference voltage value. For example, if the alarm reference value is 15 V and the voltage value of the energy storage module (110-1) is 16 V, voltage balancing is performed so that the voltage value of the energy storage module (110-1) is lowered to the reference voltage value.

[0046] When the voltage value of the energy storage module (110-1) is lower than the alarm reference value, the processing unit (123) receives the voltage values ​​of each of the other energy storage modules (110-2,..., 110-n) through the communication unit (121). The communication unit (121) can identify the other energy storage modules (110-2,..., 110-n) connected in series based on the node ID and module ID of the message received through CAN communication.

[0047] The processing unit (123) averages the voltage values ​​of each of the other energy storage modules (110-2,..., 110-n) and checks whether the voltage value of the energy storage module (110-1) in which it is installed is greater than the voltage average value by a predetermined value. For example, when the voltage average value is 10 V, the voltage value of the energy storage module (110-1) is 13 V, and the predetermined value is 2 V, the voltage value of 13 V of the energy storage module (110-1) is greater than 12 V, which is the result of adding the predetermined value of 2 V to the voltage average value of 10 V.

[0048] The processing unit (123) performs module voltage balancing by performing passive balancing on all unit cells installed in the energy storage module (110-1) when the voltage value of the energy storage module (110-1) is greater than the voltage average value by a predetermined value. That is, the processing unit (123) performs voltage balancing by turning on the balancing channels of all unit cells in the energy storage module (110-1) so that the voltage value of the energy storage module (110-1) is lowered to a reference voltage value. Alternatively, the processing unit (123) may perform voltage balancing so that the voltage value of the energy storage module (110-1) returns to the voltage average value of other energy storage modules (110-2, ..., 110-n) that are connected in series.

[0049] The processing unit (123) checks whether the difference between the largest voltage value and the smallest voltage value among the voltage values ​​of other energy storage modules (110-2, ..., 110-n) is greater than a predetermined threshold value when the voltage value of the energy storage module (110-1) is not greater than the average voltage value, and if the difference between the largest voltage value and the smallest voltage value is greater than the predetermined threshold value, checks whether the voltage value of the energy storage module (110-1) is greater than the average of the largest voltage value and the smallest voltage value. For reference, the process of checking whether the difference between the largest voltage value and the smallest voltage value is greater than the predetermined threshold value is to adjust the voltage values ​​of the energy storage modules (110-1, 110-2, ..., 110-n) to the low-voltage state when there is an energy storage module in a low-voltage state among the energy storage modules (110-1, 110-2, ..., 110-n) connected in series.

[0050] The processing unit (123) performs module voltage balancing by performing passive balancing on all unit cells installed in the energy storage module (110-1) when the voltage value of the energy storage module (110-1) is greater than the average of the largest voltage value and the smallest voltage value. That is, the processing unit (123) can perform voltage balancing for a predetermined period of time by turning on the balancing channel of all unit cells in the energy storage module (110-1) so that the voltage value of the energy storage module (110-1) is lowered to a reference voltage value, or so that the voltage value of the energy storage module (110-1) returns to the average voltage value of other energy storage modules (110-2, ..., 110-n) connected in series. After performing voltage balancing, the processing unit (123) returns to the beginning of the operation described above and repeats the operation.

[0051] If the difference between the largest voltage value and the smallest voltage value is less than or equal to the predetermined threshold value, or if the voltage value of the energy storage module (110-1) is not greater than the average of the largest voltage value and the smallest voltage value, the processing unit (123) does not perform voltage balancing on the energy storage module (110-1), waits for a predetermined time, and then returns to the beginning of the operation described above and repeats the operation.

[0052] The reason why the processing unit (123) performs voltage balancing for the predetermined time or waits for the predetermined time when not performing voltage balancing is to wait until the completion of voltage balancing operations performed by other energy storage modules (110-2,..., 110-n) similar to the energy storage module (110-1).

[0053] Next, voltage balancing between cells within one energy storage module (110-1) will be described. Even if voltage balancing is performed between energy storage modules (110-1, 110-2, ..., 110-n), voltage deviations between cells may occur within each energy storage module (110-1, 110-2, ..., 110-n), so voltage balancing between cells is performed. It should be noted that a key feature of the present invention is that voltage balancing between energy storage modules (110-1, 110-2, ..., 110-n) is performed first, and then voltage balancing between cells within the energy storage modules (110-1, 110-2, ..., 110-n) is performed. The present invention first performs voltage balancing between energy storage modules (110-1, 110-2, ..., 110-n) to achieve efficient voltage balancing not only in applications that maintain a constant voltage for a long period of time but also in frequent charging and discharging applications. The operations described below are performed independently for each unit cell.

[0054] The voltage measurement unit (122) of the energy storage module (110-1) measures the voltage of each specific unit cell within the energy storage module (110-1). The processing unit (123) checks whether the voltage value of the corresponding measurement unit cell is equal to or higher than the alarm reference value, and if so, performs voltage balancing for the specific unit cell so that the voltage value is lowered to the reference voltage value.

[0055] The processing unit (123) averages the voltage values ​​of other unit cells when the voltage value of the specific unit cell is less than the alarm reference value, and checks whether the voltage value of the specific unit cell is greater than the average voltage value by a predetermined value. Here, the predetermined value is, for example, 0.1 V.

[0056] The processing unit (123) performs voltage balancing so that the voltage value of the specific unit cell is lowered to a reference voltage value when the voltage value of the specific unit cell is greater than the voltage average value by a predetermined value or more. Alternatively, the processing unit (123) may perform voltage balancing so that the voltage value of the specific unit cell returns to the voltage average value of other unit cells.

[0057] The processing unit (123) checks whether the difference between the largest voltage value and the smallest voltage value among the voltage values ​​of other unit cells is greater than a predetermined threshold value when the voltage value of the specific unit cell is not greater than the average voltage value by a predetermined value, and if the difference between the largest voltage value and the smallest voltage value is greater than the predetermined threshold value, checks whether the voltage value of the specific unit cell is greater than the average of the largest voltage value and the smallest voltage value. For reference, the process of checking whether the difference between the largest voltage value and the smallest voltage value is greater than the predetermined threshold value is to adjust the voltage values ​​of the unit cells to a low-voltage state when there is a unit cell in a low-voltage state among the series-connected unit cells.

[0058] The processing unit (123) may perform voltage balancing for a predetermined period of time so that the voltage value of the specific unit cell is lowered to a reference voltage value, or so that the voltage value of the specific unit cell returns to the voltage average value of other unit cells connected in series, when the voltage value of the specific unit cell is greater than the average of the largest voltage value and the smallest voltage value. After performing voltage balancing, the processing unit (123) repeats the operation described above for other unit cells.

[0059] If the difference between the largest voltage value and the smallest voltage value is less than or equal to the predetermined threshold value, or if the voltage value of the specific unit cell is not greater than the average of the largest voltage value and the smallest voltage value, the processing unit (123) does not perform voltage balancing for the specific unit cell, but waits for a predetermined time and then repeats the operation described above for other unit cells.

[0060] The reason why the processing unit (123) performs voltage balancing for the predetermined time or waits for the predetermined time when not performing voltage balancing is to wait until the completion of voltage balancing operations performed by other energy storage modules (110-2,..., 110-n) similar to the energy storage module (110-1).

[0061] When voltage balancing for all unit cells is completed, the processing unit (123) restarts the voltage balancing operation between the energy storage modules (110-1, 110-2, ..., 110-n).

[0062] FIG. 4 is a flowchart illustrating a voltage balancing method between energy storage modules according to one embodiment of the present invention, and describes the operation of the voltage balancing device (120-1) of the energy storage module (110-1) among a plurality of energy storage modules (110-1, 110-2, ..., 110-n) connected in series as an example. The operation described with reference to FIG. 4 is also performed in the same manner in the voltage balancing devices (120-2, ..., 120-n) of other energy storage modules (110-2, ..., 110-n).

[0063] Referring to FIG. 4, in step S401, the voltage balancing device (120-1) measures the voltage value of the energy storage module (110-1) in which it is installed. Then, in step S402, the voltage balancing device (120-1) checks whether the measured voltage value of the energy storage module (110-1) is equal to or higher than the alarm reference value.

[0064] If the voltage value of the energy storage module (110-1) is higher than the alarm reference value, in step S408, the voltage balancing device (120-1) turns on the balancing channels of all unit cells in the energy storage module (110-1) to perform voltage balancing so that the voltage value of the energy storage module (110-1) is lowered to the reference voltage value. For example, if the alarm reference value is 15 V and the voltage value of the energy storage module (110-1) is 16 V, voltage balancing is performed so that the voltage value of the energy storage module (110-1) is lowered to the reference voltage value.

[0065] Meanwhile, if the voltage value of the energy storage module (110-1) is lower than the alarm reference value, in step S403, the voltage balancing device (120-1) receives the voltage values ​​of each of the other energy storage modules (110-2, ..., 110-n) through the communication unit (121). The voltage balancing device (120-1) can identify the other energy storage modules (110-2, ..., 110-n) connected in series based on the node ID and module ID of the message received through CAN communication.

[0066] In step S404, the voltage balancing device (120-1) averages the voltage values ​​of each of the other energy storage modules (110-2,..., 110-n) and checks whether the voltage value of the energy storage module (110-1) in which it is installed is greater than the average voltage value by a predetermined value, for example, 2 V or more.

[0067] If the voltage value of the energy storage module (110-1) is greater than the voltage average value by a predetermined value or more, in step S408, the voltage balancing device (120-1) turns on the balancing channels of all unit cells in the energy storage module (110-1) to perform voltage balancing so that the voltage value of the energy storage module (110-1) is lowered to a reference voltage value. Alternatively, the voltage balancing device (120-1) may perform voltage balancing so that the voltage value of the energy storage module (110-1) returns to the voltage average value of other energy storage modules (110-2, ..., 110-n) connected in series.

[0068] Meanwhile, if the voltage value of the energy storage module (110-1) is not greater than the average voltage value by a predetermined value, in step S405, the voltage balancing device (120-1) checks whether the difference between the largest (Max.) voltage value and the smallest (Min.) voltage value among the voltage values ​​of the other energy storage modules (110-2,..., 110-n) is greater than a predetermined threshold value.

[0069] If the difference between the largest (Max.) voltage value and the smallest (Min.) voltage value is greater than the predetermined threshold value, in step S406, the voltage balancing device (120-1) checks whether the voltage value of the energy storage module (110-1) is greater than the average of the largest (Max.) voltage value and the smallest (Minx) voltage value.

[0070] If the voltage value of the energy storage module (110-1) is greater than the average of the largest (Max.) voltage value and the smallest (Min.) voltage value, in step S408, the voltage balancing device (120-1) performs voltage balancing for a predetermined time by turning on the balancing channels of all unit cells in the energy storage module (110-1) so that the voltage value of the energy storage module (110-1) is lowered to a reference voltage value, or so that the voltage value of the energy storage module (110-1) returns to the voltage average value of other energy storage modules (110-2,..., 110-n) connected in series.

[0071] Meanwhile, if the difference between the largest (Max.) voltage value and the smallest (Min.) voltage value is not greater than a predetermined threshold value as a result of checking in step S405, or if the voltage value of the energy storage module (110-1) is not greater than the average of the largest (Max.) voltage value and the smallest (Min.) voltage value as a result of checking in step S406, then in step S407, the voltage balancing device (120-1) does not perform voltage balancing, waits for a predetermined time, and then returns to the beginning of the operation described above and repeats the operation.

[0072] FIG. 5 is a flowchart illustrating a method for balancing voltage between cells in an energy storage module according to one embodiment of the present invention, and describes the operation of the voltage balancing device (120-1) of the energy storage module (110-1) among a plurality of energy storage modules (110-1, 110-2, ..., 110-n) connected in series as an example. The operation described with reference to FIG. 5 is also performed in the same manner in the voltage balancing devices (120-2, ..., 120-n) of other energy storage modules (110-2, ..., 110-n). For reference, the operation described with reference to FIG. 5 may be performed after step S407 or step S408 of the operation described with reference to FIG. 4.

[0073] Referring to FIG. 5, in step S501, the voltage balancing device (120-1) measures the voltage value of a specific unit cell within the energy storage module (110-1). Then, in step S502, the voltage balancing device (120-1) checks whether the measured voltage value of the specific unit cell is equal to or higher than the alarm reference value.

[0074] If the voltage value of the specific unit cell is higher than the alarm reference value, in step S508, the voltage balancing device (120-1) performs voltage balancing so that the voltage value of the specific unit cells is lowered to the reference voltage value.

[0075] Meanwhile, if the measured voltage value of the specific unit cell is less than the alarm reference value, in step S503, the voltage balancing device (120-1) measures the voltage values ​​of other unit cells.

[0076] In step S504, the voltage balancing device (120-1) averages the voltage values ​​of other unit cells and checks whether the voltage value of the specific unit cell is greater than the average voltage value by a predetermined value, for example, 0.1 V or more.

[0077] If the measured voltage value of the specific unit cell is greater than the voltage average value by a predetermined value or more, in step S508, the voltage balancing device (120-1) may perform voltage balancing so that the voltage value of the specific unit cell is lowered to a reference voltage value, or may perform voltage balancing so that the voltage value of the specific unit cell returns to the voltage average value of other unit cells connected in series.

[0078] Meanwhile, if the voltage value of the specific unit cell is not greater than the average voltage value by a predetermined value, in step S505, the voltage balancing device (120-1) checks whether the difference between the largest (Max.) voltage value and the smallest (Min.) voltage value among the voltage values ​​of other unit cells is greater than a predetermined threshold value.

[0079] If the difference between the largest (Max.) voltage value and the smallest (Min.) voltage value is greater than the predetermined threshold value, in step S506, the voltage balancing device (120-1) checks whether the voltage value of the specific unit cell is greater than the average of the largest (Max.) voltage value and the smallest (Minx) voltage value.

[0080] If the voltage value of the specific unit cell is greater than the average of the largest (Max.) voltage value and the smallest (Min.) voltage value, in step S508, the voltage balancing device (120-1) performs voltage balancing for a predetermined time so that the voltage value of the specific unit cells is lowered to the reference voltage value, or the voltage value of the specific unit cell returns to the average voltage value of other unit cells connected in series.

[0081] Meanwhile, if the difference between the largest (Max.) voltage value and the smallest (Min.) voltage value is not greater than a predetermined threshold value as a result of checking in step S505, or if the voltage value of the specific unit cell is not greater than the average of the largest (Max.) voltage value and the smallest (Min.) voltage value as a result of checking in step S506, then in step S507, the voltage balancing device (120-1) does not perform voltage balancing, waits for a predetermined time, and then returns to the beginning of the operation described above and repeats the operation for other unit cells.

[0082] After performing the operation described with reference to FIG. 5 for all unit cells, the voltage balancing device (120-1) performs the voltage balancing operation between energy storage modules described with reference to FIG. 4 again.

[0083] FIG. 6 is a diagram showing an experimental example of voltage balancing according to one embodiment of the present invention, showing the process of voltage balancing over time between three energy storage modules, each of which has 18 unit cells connected in series.

[0084] Figure 6 (a) shows the voltage of three energy storage modules (modules #1, 2, 3) over time, Figure 6 (b) shows the voltage of internal unit cells of energy storage module #1 over time, and Figure 6 (c) shows the number of unit cells performing voltage balancing of energy storage module #1. In Figures 6 (a) and (b), the X-axis represents time (min) and the Y-axis represents voltage. And in Figure 6 (c), the X-axis represents time (min) and the Y-axis represents the total number of cells in which balancing is in progress (i.e., channel ON).

[0085] In this embodiment, among the three energy storage modules, the voltage of energy storage module #3 is initially low. In period 1, energy storage modules #1 and #2 each lower their voltages according to the voltage balancing method between energy storage modules described above, and thus the voltage of energy storage module #3 increases. In period 1, energy storage module #1 completes voltage balancing between energy storage modules, and performs voltage balancing between internal cells in periods 2 and 3. However, energy storage module #2 still performs voltage balancing between energy storage modules in period 2, and performs voltage balancing between cells in period 3. Therefore, the voltage of energy storage module #3, which does not perform voltage balancing between modules or voltage balancing between cells, increases in periods 2 and 3.

[0086] According to (b) of FIG. 6, energy storage module #1 completes voltage balancing between energy storage modules in period 1, but performs voltage balancing between internal cells in periods 2 and 3, and voltage balancing between cells is completed in period 3.

[0087] According to (c) of FIG. 6, in period 1, energy storage module #1 performs voltage balancing between energy storage modules, so the number of unit cells performing voltage balancing is the total number of 18. In period 2, energy storage module #1 performs voltage balancing between cells, and at this time, voltage balancing of 8 unit cells is performed. In period 3, the number of unit cells performing voltage balancing gradually decreases.

[0088] As described above, according to an embodiment of the present invention, voltage balancing between energy storage modules can be achieved through direct communication between energy storage modules connected in series without configuring a separate circuit for voltage balancing.

[0089] While this specification includes many features, such features should not be construed as limiting the scope of the present invention or the claims. Furthermore, features described in individual embodiments herein may be combined and implemented in a single embodiment. Conversely, various features described in a single embodiment herein may be implemented individually or in appropriate combinations across multiple embodiments.

[0090] Although operations are illustrated in a specific order in the drawings, this should not be construed as meaning that such operations are performed in the specific order depicted, or in a series of sequential orders, or that all described operations must be performed to achieve a desired result. Multitasking and parallel processing may be advantageous in certain environments. Furthermore, it should be understood that the distinction between various system components in the embodiments described above does not require such distinction in all embodiments.

[0091] The present invention described above is not limited to the above-described embodiments and the attached drawings, as various substitutions, modifications, and changes can be made within the scope of the technical idea of ​​the present invention by a person having ordinary skill in the art to which the present invention pertains.

Claims

1. A plurality of energy storage modules each including a plurality of unit cells and connected in series; and An energy storage system including a voltage balancing device installed in each energy storage module and communicating with each other to perform voltage balancing between the plurality of energy storage modules.

2. In paragraph 1, The above voltage balancing device, A voltage measuring unit for measuring the voltage value of an energy storage module in which the voltage balancing device is installed; A communication unit that communicates with other voltage balancing devices installed in other energy storage modules to receive voltage values ​​of other energy storage modules; and An energy storage system including a processing unit that performs voltage balancing of an energy storage module in which a voltage balancing device is installed based on the measured voltage value and the received voltage values ​​of other energy storage modules.

3. In paragraph 2, The above communication department, Transmit and receive voltage values ​​through CAN (Controller Area Network) communication messages with the other voltage balancing devices mentioned above, An energy storage system characterized in that the serially connected energy storage modules in the ID field of the above CAN communication message have the same node ID and each energy storage module has a different module ID.

4. In paragraph 2, The above processing unit, An energy storage system characterized in that voltage balancing is performed on an energy storage module in which a voltage balancing device is installed when the measured voltage value is greater than a predetermined value or more than the average voltage value of other energy storage modules.

5. In paragraph 2, The above processing unit, An energy storage system characterized in that voltage balancing of an energy storage module in which a voltage balancing device is installed is performed when the difference between the largest voltage value and the smallest voltage value among the voltage values ​​of other energy storage modules is greater than a predetermined threshold value and the measured voltage value is greater than the average of the largest voltage value and the smallest voltage value.

6. In paragraph 2, The above processing unit, An energy storage system characterized in that when the measured voltage value is higher than the alarm reference value, voltage balancing of an energy storage module in which the voltage balancing device is installed is performed.

7. In paragraph 2, The above processing unit, An energy storage system characterized in that voltage balancing is performed between unit cells within the energy storage module after voltage balancing of the energy storage module in which the voltage balancing device is installed is completed.

8. In paragraph 7, The above voltage measuring unit, Measure the voltage values ​​of the unit cells, The above processing unit, An energy storage system characterized in that voltage balancing of a specific unit cell is performed when the voltage value of the specific unit cell is greater than the average voltage value of other unit cells by a predetermined value or more.

9. In paragraph 7, The above voltage measuring unit, Measure the voltage values ​​of the unit cells, The above processing unit, An energy storage system characterized in that voltage balancing of a specific unit cell is performed when the difference between the largest voltage value and the smallest voltage value among the voltage values ​​of unit cells other than a specific unit cell is greater than a predetermined threshold value, and the voltage value of the specific unit cell is greater than the average of the largest voltage value and the smallest voltage value.

10. In paragraph 7, The above voltage measuring unit, Measure the voltage values ​​of the unit cells, The above processing unit, An energy storage system characterized in that voltage balancing of a specific unit cell is performed when the voltage value of the specific unit cell is higher than an alarm reference value.

11. A voltage balancing method of each voltage balancing device installed in each energy storage module in an energy storage system including a plurality of energy storage modules each including a plurality of unit cells and connected in series, A voltage balancing method comprising a step of performing voltage balancing between a plurality of energy storage modules by communicating with voltage balancing devices installed in other energy storage modules.

12. In paragraph 11, The steps performed above are: A step of measuring the voltage value of an energy storage module in which the voltage balancing device is installed; A step of communicating with other voltage balancing devices installed in other energy storage modules to receive voltage values ​​of other energy storage modules; and A voltage balancing method comprising a step of performing voltage balancing of an energy storage module in which a voltage balancing device is installed based on the measured voltage value and the received voltage values ​​of other energy storage modules.

13. In paragraph 12, The above receiving step is, Receive voltage values ​​through CAN (Controller Area Network) communication messages with the other voltage balancing devices mentioned above, A voltage balancing method characterized in that the serially connected energy storage modules in the ID field of the above CAN communication message have the same node ID and each energy storage module has a different module ID.

14. In paragraph 12, The step of performing voltage balancing of the energy storage module in which the voltage balancing device is installed comprises: A voltage balancing method characterized in that when the measured voltage value is greater than the average voltage value of other energy storage modules by a predetermined value or more, voltage balancing of the energy storage module in which the voltage balancing device is installed is performed.

15. In paragraph 12, The step of performing voltage balancing of the energy storage module in which the voltage balancing device is installed comprises: A voltage balancing method characterized in that when the difference between the largest voltage value and the smallest voltage value among the voltage values ​​of other energy storage modules is greater than a predetermined threshold value, and the measured voltage value is greater than the average of the largest voltage value and the smallest voltage value, voltage balancing of an energy storage module in which a voltage balancing device is installed is performed.

16. In paragraph 12, A voltage balancing method, characterized in that it further includes a step of performing voltage balancing of an energy storage module in which the voltage balancing device is installed when the measured voltage value is higher than an alarm reference value.

17. In paragraph 12, A voltage balancing method characterized in that it further includes a step of performing voltage balancing between unit cells within the energy storage module after voltage balancing of the energy storage module in which the voltage balancing device is installed is completed.

18. In paragraph 17, The step of performing voltage balancing between the above unit cells is: A step of measuring the voltage values ​​of unit cells; and A voltage balancing method, characterized in that it includes a step of performing voltage balancing of a specific unit cell when the voltage value of the specific unit cell is greater than the average voltage value of other unit cells by a predetermined value or more.

19. In paragraph 17, The step of performing voltage balancing between the above unit cells is: A step of measuring the voltage values ​​of unit cells; and A voltage balancing method, characterized in that it includes a step of performing voltage balancing of a specific unit cell when a difference between the largest voltage value and the smallest voltage value among voltage values ​​of unit cells other than a specific unit cell is greater than a predetermined threshold value and the voltage value of the specific unit cell is greater than an average of the largest voltage value and the smallest voltage value.

20. In paragraph 17, The step of performing voltage balancing between the above unit cells is: A step of measuring the voltage values ​​of unit cells; and A voltage balancing method characterized in that voltage balancing of a specific unit cell is performed when the voltage value of the specific unit cell is higher than an alarm reference value.

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