Energy storage system and method for voltage balancing between energy storage modules connected in series.

Abstract

An energy storage system and method are disclosed 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. An energy storage system according to one embodiment includes a plurality of energy storage modules, each containing a plurality of unit cells and connected in series, and a voltage balancing device provided on each energy storage module, which communicates with each other to perform voltage balancing among the plurality of energy storage modules.

Description

Technical Field

[0005]

[0001] This application claims priority based on Korean Patent Application No. 10-2023-0122087 filed on September 13, 2023, and all the content disclosed in the specification and drawings of that application is incorporated 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 specifically, to an energy storage system and method for performing voltage balancing between energy storage modules connected in series.

Background Art

[0003] Generally, an energy storage module includes a plurality of unit cells connected in series to achieve a high voltage. Also, such an energy storage module is generally not used as a single module, but a plurality of them are connected in series and implemented as one pack for use. In such a pack or energy storage module, it is necessary to appropriately perform voltage balancing.

[0004] Voltage balancing refers to sensing an energy storage module having a voltage greater than or less than a reference voltage and discharging or charging the energy storage module to adjust the energy storage module to the reference voltage. If voltage balancing is not appropriately performed, the degradation of the cells is accelerated, the lifespan is shortened, and the stability and reliability of the entire system cannot be guaranteed.

[0005] Conventionally, 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 to adjust the voltage deviation between the energy storage modules using passive balancing or active balancing technology. In order for the controller to control each voltage balancing device, a separate circuit is required for the connection between each voltage balancing device and the controller that controls them. Because a separate circuit is required for voltage balancing in this way, the size of the printed circuit board increases, the circuit becomes more complex, and the number of points where defects can occur increases. [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention was proposed to solve the above-mentioned problems and aims 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. [Means for solving the problem]

[0007] An energy storage system according to one aspect of the present invention includes a plurality of energy storage modules, each containing a plurality of unit cells and connected in series, and a voltage balancing device provided on each energy storage module, which communicates with each other to perform voltage balancing among 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 the voltage values ​​of those 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 value of the other energy storage module.

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

[0010] The processing unit may perform voltage balancing of the energy storage module equipped with the voltage balancing device if the measured voltage value is greater than or equal to a predetermined value than the average voltage value of other energy storage modules.

[0011] The processing unit may perform voltage balancing of the energy storage module equipped with the voltage balancing device if the difference between the maximum and minimum voltage values ​​of the other energy storage modules is greater than a predetermined critical value, and the measured voltage value is greater than the average of the maximum and minimum voltage values.

[0012] The processing unit may perform voltage balancing of the energy storage module equipped with the voltage balancing device if the measured voltage value is equal to or greater than the notification reference value.

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

[0014] The voltage measuring unit measures the voltage value of a unit cell, and the processing unit may perform voltage balancing of a specific unit cell if the voltage value of that specific unit cell is greater than or equal to a predetermined value than the average voltage value of the other unit cells.

[0015] The voltage measuring unit measures the voltage value of a unit cell, and the processing unit may perform voltage balancing of the specific unit cell if the difference between the maximum and minimum voltage values ​​of other unit cells (excluding the specific unit cell) is greater than a predetermined critical value, and the voltage value of the specific unit cell is greater than the average of the maximum and minimum voltage values.

[0016] The voltage measuring unit measures the voltage value of a unit cell, and the processing unit may perform voltage balancing of a specific unit cell if the voltage value of that specific unit cell is equal to or greater than a notification reference value.

[0017] Another aspect of the present invention relates to a voltage balancing method in an energy storage system including a plurality of energy storage modules, each containing a plurality of unit cells and connected in series, wherein the method comprises a step of performing voltage balancing among the plurality of energy storage modules by communicating with voltage balancing devices provided in other energy storage modules.

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

[0019] The receiving step involves receiving voltage values ​​via CAN communication messages with the other voltage balancing device, wherein the series-connected energy storage modules have the same node ID in the ID field of the CAN communication message, and each energy storage module may have a different module ID.

[0020] The step of performing voltage balancing on an energy storage module equipped with the voltage balancing device may be performed if the measured voltage value is greater than or equal to a predetermined value than the average voltage value of other energy storage modules.

[0021] The step of performing voltage balancing on an energy storage module equipped with the voltage balancing device may be performed if the difference between the maximum and minimum voltage values ​​among the voltage values ​​of other energy storage modules is greater than a predetermined critical value, and the measured voltage value is greater than the average of the maximum and minimum voltage values.

[0022] The voltage balancing method may further include the step of performing voltage balancing of an energy storage module equipped with a voltage balancing device if the measured voltage value is equal to or greater than a notification reference value.

[0023] After the voltage balancing of the energy storage module provided with the voltage balancing device is completed, the voltage balancing method may further include a step of performing voltage balancing between unit cells in the energy storage module.

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

[0025] The step of performing voltage balancing between the unit cells may include a step of measuring the voltage value of a unit cell, a step of performing voltage balancing of the specific unit cell when the difference between the maximum voltage value and the minimum voltage value among the voltage values of other unit cells other than the specific unit cell is greater than a predetermined critical value, and the voltage value of the specific unit cell is greater than the average of the maximum voltage value and the minimum voltage value.

[0026] The step of performing voltage balancing between the unit cells may include a step of measuring the voltage value of a unit cell, and a step of performing voltage balancing of the specific unit cell when the voltage value of the specific unit cell is equal to or greater than a notification reference value.

Advantages of the Invention

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

Brief Description of the Drawings

[0028] [Figure 1] It is a diagram showing the configuration of an energy storage system according to an embodiment of the present invention. [Figure 2] It is an example showing the 29-bit ID field of the extended CAN according to an embodiment of the present invention. [Figure 3]This figure shows the configuration of a voltage balancing device according to one embodiment of the present invention. [Figure 4] This is a flowchart illustrating a voltage balancing method between energy storage modules according to one embodiment of the present invention. [Figure 5] This is a flowchart illustrating a method for voltage balancing between cells within an energy storage module according to one embodiment of the present invention. [Figure 6a] This figure shows an experimental example of voltage balancing performed using one embodiment of the present invention. [Figure 6b] This figure shows an experimental example of voltage balancing performed using one embodiment of the present invention. [Figure 6c] This figure shows an experimental example of voltage balancing performed using one embodiment of the present invention. [Modes for carrying out the invention]

[0029] Embodiments of the present invention will be described in detail below with reference to the attached drawings. However, regardless of the drawing number, identical or similar components will be denoted by the same reference numeral, and redundant descriptions will be omitted. The suffix "part" used in the following description of components is added or mixed in solely for the purpose of facilitating the preparation of the specification and does not have a distinct meaning or role in itself. Furthermore, when describing embodiments disclosed herein, if it is determined that a specific description of related prior art may obscure the gist of the embodiments of the present invention, such detailed description will be omitted. In addition, the attached drawings are intended to facilitate understanding of embodiments of the present invention, and the drawings are not intended to limit the technical ideas disclosed herein, but rather to include all modifications, equivalents, or substitutions that fall within the concept and technical scope of the present invention.

[0030] Terms that include ordinal numbers, such as "1st," "2nd," etc., are used to distinguish one of several components from other components, and these terms do not limit the components themselves.

[0031] Furthermore, singular expressions include plural expressions unless the context makes it clear that they have a different meaning. In this invention, terms such as "includes" or "has" indicate the presence of features, numbers, stages, operations, components, parts, or combinations thereof described in the specification, and should be understood as not preemptively excluding the possibility of the presence or addition of one or more other features, numbers, stages, operations, components, parts, or combinations thereof.

[0032] Figure 1 is a diagram showing the configuration of an energy storage system according to one embodiment of the present invention. Referring to Figure 1, the energy storage system according to this embodiment has a plurality of energy storage modules 110-1, 110-2, ..., 110-n connected in series, and each of the energy storage modules 110-1, 110-2, ..., 110-n includes a plurality of unit cells and voltage balancing devices 120-1, 120-2, ..., 120-n connected in series. In this embodiment, only a plurality of energy storage modules 110-1, 110-2, ..., 110-n connected in series are shown and described, but the invention is not limited to this, and a plurality of sets of a plurality of energy storage modules 110-1, 110-2, ..., 110-n connected in series may be provided, and the sets may be connected in parallel to realize an energy storage system.

[0033] 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 via a busbar or the like, with their positive and negative electrodes connected. The number of unit cells in each energy storage module 110-1, 110-2, ..., 110-n, and the total number of energy storage modules 110-1, 110-2, ..., 110-n, can be determined according to the operating voltage required by the application.

[0034] Voltage balancing devices 120-1, 120-2, ..., 120-n, provided in each energy storage module 110-1, 110-2, ..., 110-n, are interconnected and communicate with each other. They are also interconnected with all unit cells within 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 between the cells within the energy storage modules 110-1, 110-2, ..., 110-n. Preferably, the voltage balancing devices 120-1, 120-2, ..., 120-n communicate via CAN (Controller Area Network). Here, the balancing is generally passive balancing.

[0035] Conventionally, in order to balance the voltage of an energy storage system composed of multiple energy storage modules, a voltage balancing device is provided for each energy storage module, and each voltage balancing device is controlled by a controller. Therefore, a separate circuit is required to connect each voltage balancing device to the controller that controls them. However, in the present invention, since the voltage balancing devices 120-1, 120-2, ..., 120-n perform voltage balancing via CAN communication, a controller is not required to control the voltage balancing devices 120-1, 120-2, ..., 120-n, and therefore a separate circuit is not required to connect the voltage balancing devices 120-1, 120-2, ..., 120-n to a controller.

[0036] Furthermore, conventionally, voltage balancing between energy storage modules is performed by connecting resistors to the positive and / or negative electrodes of the energy storage modules. However, in the present invention, voltage balancing between modules and between cells is performed by controlling the on / off state of the balancing channels of each cell within the energy storage modules 110-1, 110-2, ..., 110-n, without using separate external resistors.

[0037] CAN communication is a message-based protocol in which data is transmitted and received in frame form. Each frame is identified by an ID field, which is 11 bits long in standard CAN and 29 bits long in extended CAN. In this invention, the ID field of CAN communication is used to determine the priority of messages and to determine whether a message has been received. In this embodiment, an extended CAN with a length of 29 bits is given as an example. Figure 2 shows an example of a 29-bit ID field of an extended CAN according to one embodiment of the present invention. Referring to Figure 2, the ID field consists of a 3-bit service ID field, a 5-bit module ID field, a 13-bit node ID field, and an 8-bit extended ID field. In this embodiment, energy storage modules 110-1, 110-2, ..., 110-n connected in series are configured to use the same node ID. In other words, the voltage balancing devices 120-1, 120-2, ..., 120-n of energy storage modules 110-1, 110-2, ..., 110-n connected in series communicate with each other 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 their module IDs. On the other hand, when energy storage modules 110-1, 110-2, ..., 110-n are connected in parallel, each energy storage module 110-1, 110-2, ..., 110-n is configured to use a different node ID.

[0038] The voltage balancing devices 120-1, 120-2, ..., 120-n, provided in the energy storage modules 110-1, 110-2, ..., 110-n, are interconnected and communicate with each other to 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 operations of each voltage balancing device 120-1, 120-2, ..., 120-n are performed independently and similarly, the following explanation will use the voltage balancing device 120-1 of the first energy storage module 110-1 as the reference.

[0039] Figure 3 shows the configuration of a voltage balancing device 120-1 according to one embodiment of the present invention. Referring to Figure 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 a microprocessor or the like, but is not limited thereto, and may include processing circuits such as a DSP (Digital Signal Processor), ASIC (Application-Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), and may operate by a program stored in memory. Below, we will first set up voltage balancing between energy storage modules 110-1, 110-2, ..., 110-n, and then describe voltage balancing between cells within one energy storage module 110-1.

[0040] First, the voltage measurement 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. The processing unit 123 then checks whether the voltage value of the energy storage module 110-1 measured by the voltage measurement unit 122 is equal to or greater than the notification reference value. If the voltage value of the energy storage module 110-1 is equal to or greater than the notification reference value, the processing unit 123 performs module voltage balancing by collectively performing passive balancing on all unit cells provided within the energy storage module 110-1. That is, the processing unit 123 turns on the balancing channels of all unit cells in the energy storage module 110-1 to lower the voltage value of the energy storage module 110-1 to the reference voltage value. For example, if the notification reference value is 15V and the voltage value of the energy storage module 110-1 is 16V, voltage balancing is performed so that the voltage value of the energy storage module 110-1 is lowered to the reference voltage value.

[0041] If the voltage value of energy storage module 110-1 is below the notification reference value, the processing unit 123 receives the voltage values ​​of the other energy storage modules 110-2, ..., 110-n via 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 via CAN communication.

[0042] The processing unit 123 calculates an average voltage value by averaging the voltage values ​​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 or equal to a predetermined value than that average voltage value. For example, if the average voltage value is 10V, the voltage value of energy storage module 110-1 is 13V, and the predetermined value is 2V, then the voltage value of energy storage module 110-1, 13V, is greater than 12V, which is the average voltage value of 10V plus the predetermined value of 2V.

[0043] If the voltage value of the energy storage module 110-1 is greater than or equal to a predetermined value than the average voltage, the processing unit 123 performs module voltage balancing by collectively performing passive balancing on all unit cells provided in the energy storage module 110-1. That is, the processing unit 123 turns on the balancing channels of all unit cells in the energy storage module 110-1 and performs voltage balancing so that the voltage value of the energy storage module 110-1 is reduced 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 average voltage value of the other energy storage modules 110-2, ..., 110-n connected in series.

[0044] If the voltage value of energy storage module 110-1 is not greater than a predetermined value than the average voltage value, the processing unit 123 checks whether the difference between the maximum voltage value and the minimum voltage value of the other energy storage modules 110-2, ..., 110-n is greater than a predetermined critical value. If the difference between the maximum voltage value and the minimum voltage value is greater than the predetermined critical value, the processing unit 123 checks whether the voltage value of energy storage module 110-1 is greater than the average of the maximum voltage value and the minimum voltage value. For reference, the process of checking whether the difference between the maximum voltage value and the minimum voltage value is greater than the predetermined critical value is to adjust the voltage values ​​of energy storage modules 110-1, 110-2, ..., 110-n to match 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.

[0045] If the voltage value of the energy storage module 110-1 is greater than the average of the maximum voltage value and the minimum voltage value, the processing unit 123 performs module voltage balancing by collectively performing passive balancing on all unit cells provided in the energy storage module 110-1. That is, the processing unit 123 can turn on the balancing channels of all unit cells in the energy storage module 110-1 and perform voltage balancing over a predetermined period of time so that the voltage value of the energy storage module 110-1 drops to the reference voltage value, or so that the voltage value of the energy storage module 110-1 returns to the average voltage value of the 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 above operation and repeats the process.

[0046] If the difference between the maximum voltage value and the minimum voltage value is less than or equal to the predetermined critical value, or if the voltage value of the energy storage module 110-1 is not greater than the average of the maximum voltage value and the minimum voltage value, the processing unit 123 does not perform voltage balancing for the energy storage module 110-1, waits for a predetermined time, and then returns to the beginning of the above operation and repeats the process.

[0047] The reason why the processing unit 123 performs voltage balancing for a predetermined period of time, or waits for a predetermined period of time if it does not perform voltage balancing, is to wait until the other energy storage modules 110-2, ..., 110-n perform voltage balancing operations in the same way as energy storage module 110-1 is completed.

[0048] Next, we will explain voltage balancing between cells within one energy storage module 110-1. Even if voltage balancing is performed between energy storage modules 110-1, 110-2, ..., 110-n, voltage deviations may occur between cells within each energy storage module 110-1, 110-2, ..., 110-n, therefore, voltage balancing between cells is performed. The main feature of this invention is that voltage balancing is performed first between energy storage modules 110-1, 110-2, ..., 110-n, and then voltage balancing is performed between cells within each energy storage module 110-1, 110-2, ..., 110-n. This invention performs voltage balancing between energy storage modules 110-1, 110-2, ..., 110-n first for efficient voltage balancing not only in applications where the voltage is maintained at a constant voltage for a long period of time, but also in applications where charging and discharging are frequent. The operations described later are performed independently for each unit cell.

[0049] 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 specific unit cell is equal to or greater than the notification reference value, and if it is, performs voltage balancing on the specific unit cell so that the voltage value is reduced to the reference voltage value.

[0050] If the voltage value of the specific unit cell is less than the notification reference value, the processing unit 123 calculates the average voltage value by averaging the voltage values ​​of the other unit cells and checks whether the voltage value of the specific unit cell is greater than or equal to a predetermined value than the average voltage value. Here, the predetermined value is, for example, 0.1V.

[0051] If the voltage value of a particular unit cell is greater than or equal to a predetermined value than the average voltage value, the processing unit 123 performs voltage balancing so that the voltage value of that particular unit cell is reduced to the reference voltage value. Alternatively, the processing unit 123 may perform voltage balancing so that the voltage value of that particular unit cell returns to the average voltage value of the other unit cells.

[0052] If the voltage value of the particular unit cell is not greater than a predetermined value than the average voltage, the processing unit 123 checks whether the difference between the maximum and minimum voltage values ​​of the other unit cells is greater than a predetermined critical value. If the difference between the maximum and minimum voltage values ​​is greater than the predetermined critical value, it checks whether the voltage value of the particular unit cell is greater than the average of the maximum and minimum voltage values. For reference, the process of checking whether the difference between the maximum and minimum voltage values ​​is greater than the predetermined critical value is to adjust the voltage value of a unit cell to match the low voltage state when there is a unit cell in a series-connected unit cell.

[0053] If the voltage value of a particular unit cell is greater than the average of the maximum voltage value and the minimum voltage value, the processing unit 123 may perform voltage balancing over a predetermined period of time so that the voltage value of the particular unit cell decreases to the reference voltage value, or so that the voltage value of the particular unit cell returns to the average voltage value of other unit cells connected in series. After performing voltage balancing, the processing unit 123 repeats the above operation for the other unit cells.

[0054] If the difference between the maximum voltage value and the minimum voltage value is less than or equal to the predetermined critical value, or if the voltage value of the particular unit cell is not greater than the average of the maximum voltage value and the minimum voltage value, the processing unit 123 does not perform voltage balancing for the particular unit cell, waits for a predetermined time, and then repeats the above operation for the other unit cells.

[0055] The reason why the processing unit 123 performs voltage balancing for a predetermined period of time, or waits for a predetermined period of time if it does not perform voltage balancing, is to wait until the other energy storage modules 110-2, ..., 110-n perform voltage balancing operations in the same way as energy storage module 110-1 is completed.

[0056] Once voltage balancing for all unit cells is complete, the processing unit 123 restarts the voltage balancing operation between energy storage modules 110-1, 110-2, ..., 110-n.

[0057] Figure 4 is a flowchart illustrating a voltage balancing method between energy storage modules according to one embodiment of the present invention, and explains the operation of the voltage balancing device 120-1 of energy storage module 110-1, one of a plurality of energy storage modules 110-1, 110-2, ..., 110-n connected in series. The operation explained with reference to Figure 4 is similarly performed for the voltage balancing devices 120-2, ..., 120-n of the other energy storage modules 110-2, ..., 110-n.

[0058] Referring to Figure 4, in step S401, the voltage balancing device 120-1 measures the voltage value of the energy storage module 110-1 on 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 greater than the notification reference value.

[0059] If the voltage value of the energy storage module 110-1 is greater than or equal to the notification 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 reduced to the reference voltage value. For example, if the notification reference value is 15V and the voltage value of the energy storage module 110-1 is 16V, voltage balancing is performed so that the voltage value of the energy storage module 110-1 is reduced to the reference voltage value.

[0060] On the other hand, if the voltage value of energy storage module 110-1 is less than the notification reference value, in step S403, the voltage balancing device 120-1 receives the voltage values ​​of the other energy storage modules 110-2, ..., 110-n via 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 by CAN communication.

[0061] In step S404, the voltage balancing device 120-1 calculates an average voltage value by averaging the voltage values ​​of the other energy storage modules 110-2, ..., 110-n, and checks whether the voltage value of the energy storage module 110-1 on which it is installed is greater than or equal to a predetermined value, for example, 2V or more, than that average voltage value.

[0062] If the voltage value of the energy storage module 110-1 is greater than a predetermined value or more than the average voltage 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 reduced 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 average voltage value of the other energy storage modules 110-2, ..., 110-n connected in series.

[0063] On the other hand, if the voltage value of energy storage module 110-1 is not greater than a predetermined value than the average voltage value, in step S405, the voltage balancing device 120-1 checks whether the difference between the maximum voltage value and the minimum voltage value among the voltage values ​​of the other energy storage modules 110-2, ..., 110-n is greater than a predetermined critical value.

[0064] If the difference between the maximum voltage value and the minimum voltage value is greater than the predetermined critical 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 maximum voltage value and the minimum voltage value.

[0065] If the voltage value of the energy storage module 110-1 is greater than the average of the maximum voltage value and the minimum voltage 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 and performs voltage balancing for a predetermined time such that the voltage value of the energy storage module 110-1 drops to the reference voltage value, or returns to the average voltage value of the other energy storage modules 110-2, ..., 110-n connected in series.

[0066] On the other hand, if, as a result of checking in step S405, the difference between the maximum voltage value and the minimum voltage value is not greater than a predetermined critical value, or if, as a result of checking in step S406, the voltage value of the energy storage module 110-1 is not greater than the average of the maximum voltage value and the minimum voltage value, 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 above operation and repeats the process.

[0067] Figure 5 is a flowchart illustrating a voltage balancing method 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 energy storage module 110-1, one of a plurality of energy storage modules 110-1, 110-2, ..., 110-n connected in series. The operation described with reference to Figure 5 is similarly performed for the voltage balancing devices 120-2, ..., 120-n of the other energy storage modules 110-2, ..., 110-n. For reference, the operation described with reference to Figure 5 may be performed after step S407 or step S408 of the operation described with reference to Figure 4.

[0068] Referring to Figure 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 greater than the notification reference value.

[0069] If the voltage value of the specified unit cell is greater than or equal to the notification reference value, in step S508, the voltage balancing device 120-1 performs voltage balancing so that the voltage value of the specified unit cell is reduced to the reference voltage value.

[0070] On the other hand, if the voltage value measured for the specific unit cell is less than the notification reference value, in step S503, the voltage balancing device 120-1 measures the voltage values ​​of other unit cells.

[0071] 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 or equal to a predetermined value, for example, 0.1V or more, than the average voltage value.

[0072] If the voltage value measured for the particular unit cell is greater than or equal to a predetermined value than the average voltage value, in step S508, the voltage balancing device 120-1 may perform voltage balancing so that the voltage value of the particular unit cell is reduced to the reference voltage value, or perform voltage balancing so that the voltage value of the particular unit cell returns to the average voltage value of the other unit cells connected in series.

[0073] On the other hand, if the voltage value of the specific unit cell is not greater than a predetermined value than the average voltage value, in step S505, the voltage balancing device 120-1 checks whether the difference between the maximum voltage value and the minimum voltage value among the other unit cells is greater than a predetermined critical value.

[0074] If the difference between the maximum voltage value and the minimum voltage value is greater than the predetermined critical value, in step S506, the voltage balancing device 120-1 checks whether the voltage value of the particular unit cell is greater than the average of the maximum voltage value and the minimum voltage value.

[0075] If the voltage value of the particular unit cell is greater than the average of the maximum voltage value and the minimum voltage value, in step S508, the voltage balancing device 120-1 performs voltage balancing over a predetermined period of time so that the voltage value of the particular unit cell decreases to the reference voltage value, or so that the voltage value of the particular unit cell returns to the average voltage value of the other unit cells connected in series.

[0076] On the other hand, if, as a result of checking in step S505, the difference between the maximum voltage value and the minimum voltage value is not greater than a predetermined critical value, or if, as a result of checking in step S506, the voltage value of the particular unit cell is not greater than the average of the maximum voltage value and the minimum voltage value, 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 above operation and repeats it for the other unit cells.

[0077] After performing the operation described with reference to Figure 5 for all unit cells, the voltage balancing device 120-1 performs the voltage balancing operation between energy storage modules described with reference to Figure 4 again.

[0078] Figures 6a to 6c show experimental examples of voltage balancing performed by one embodiment of the present invention, illustrating the time-dependent voltage balancing process for three energy storage modules, each consisting of 18 unit cells connected in series.

[0079] Figure 6a shows the voltages of three energy storage modules (module #1, #2, and #3) over time, Figure 6b shows the voltage of an internal unit cell in energy storage module #1 over time, and Figure 6c shows the number of unit cells performing voltage balancing in energy storage module #1. In Figures 6a and 6b, the X-axis represents time (minutes) and the Y-axis represents voltage. In Figure 6c, the X-axis represents time (minutes) and the Y-axis represents the total number of cells in which balancing is performed (i.e., channel ON).

[0080] In this embodiment, initially, the voltage of energy storage module #3 is low among the three energy storage modules. 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, causing the voltage of energy storage module #3 to increase. In period 1, energy storage module #1 completes voltage balancing between energy storage modules, and in periods 2 and 3, it performs voltage balancing between internal cells. However, energy storage module #2 continues to perform voltage balancing between energy storage modules in period 2, and performs voltage balancing between cells in period 3. As a result, the voltage of energy storage module #3, which does not perform voltage balancing between modules or between cells in periods 2 and 3, becomes higher.

[0081] According to Figure 6b, energy storage module #1 completes voltage balancing between energy storage modules in cycle 1, but performs voltage balancing between internal cells in cycles 2 and 3, completing voltage balancing between cells in cycle 3.

[0082] According to Figure 6c, in period 1, energy storage module #1 performs voltage balancing among 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 among cells, this time balancing is performed on 8 unit cells. Then, in period 3, the number of unit cells performing voltage balancing gradually decreases.

[0083] As described above, according to the embodiment of the present invention, voltage balancing between energy storage modules can be performed by direct communication between energy storage modules connected in series, without configuring a separate circuit for voltage balancing.

[0084] This specification includes a variety of features, but these features are not intended to limit the scope of the invention or the claims. Furthermore, features described in this specification as individual embodiments can be combined and realized as a single embodiment. Conversely, the various features described in this specification as a single example can be realized individually as various embodiments or appropriately combined and realized.

[0085] Although multiple operations are described in a specific order in the drawings, it should not be understood that these operations are performed in a specific order as shown, or in a series of consecutive orders, or that all described operations are performed to obtain a desired result. Multitasking and parallel processing may be advantageous in certain environments. Furthermore, although the system components are divided in various ways in the embodiments described above, it should be understood that such divisions are not necessary in all embodiments.

[0086] The present invention described above is not limited by the embodiments described above and the accompanying drawings, as it can be substituted, modified, and altered in various ways by a person with ordinary skill in the art to which the present invention belongs, without departing from the technical spirit of the invention.

Claims

1. Multiple energy storage modules, each containing multiple unit cells and connected in series, An energy storage system including a voltage balancing device provided in each energy storage module, which communicates with each other to perform voltage balancing among a plurality of energy storage modules.

2. The voltage balancing device is A voltage measuring unit that measures the voltage value of an energy storage module equipped with the voltage balancing device, A communication unit that communicates with other voltage balancing devices installed in other energy storage modules and receives the voltage values ​​of those other energy storage modules, The energy storage system according to claim 1, further comprising a processing unit that performs voltage balancing of the energy storage module equipped with the voltage balancing device based on the measured voltage value and the received voltage value of another energy storage module.

3. The aforementioned communications unit is The voltage values ​​are transmitted and received via CAN communication messages with the aforementioned other voltage balancing device. The energy storage system according to claim 2, wherein in the ID field of the CAN communication message, energy storage modules connected in series have the same node ID, and each energy storage module has a different module ID.

4. The aforementioned processing unit, The energy storage system according to claim 2, wherein if the measured voltage value is greater than or equal to a predetermined value than the average voltage value of other energy storage modules, the voltage balancing of the energy storage module equipped with the voltage balancing device is performed.

5. The aforementioned processing unit, The energy storage system according to claim 2, wherein if the difference between the maximum voltage value and the minimum voltage value among the voltage values ​​of other energy storage modules is greater than a predetermined critical value, and the measured voltage value is greater than the average of the maximum voltage value and the minimum voltage value, the voltage balancing device is performed on the energy storage module on which the device is provided.

6. The aforementioned processing unit, The energy storage system according to claim 2, wherein if the measured voltage value is equal to or greater than a notification reference value, the voltage balancing device is performed on the energy storage module equipped with the voltage balancing device.

7. The aforementioned processing unit, The energy storage system according to claim 2, wherein after the voltage balancing of the energy storage module equipped with the voltage balancing device is completed, voltage balancing is performed between unit cells within the energy storage module.

8. The voltage measuring unit is Measure the voltage value of a unit cell, The aforementioned processing unit, The energy storage system according to claim 7, wherein if the voltage value of a specific unit cell is greater than or equal to a predetermined value than the average voltage value of other unit cells, voltage balancing of the specific unit cell is performed.

9. The voltage measuring unit is Measure the voltage value of a unit cell, The aforementioned processing unit, The energy storage system according to claim 7, wherein if the difference between the maximum and minimum voltage values ​​of other unit cells other than the specific unit cell is greater than a predetermined critical value, and the voltage value of the specific unit cell is greater than the average of the maximum and minimum voltage values, voltage balancing of the specific unit cell is performed.

10. The voltage measuring unit is Measure the voltage value of a unit cell, The aforementioned processing unit, The energy storage system according to claim 7, wherein if the voltage value of a specific unit cell is greater than or equal to a notification reference value, voltage balancing of the specific unit cell is performed.

11. In an energy storage system including multiple energy storage modules, each containing multiple unit cells and connected in series, a voltage balancing method for each voltage balancing device provided for each energy storage module, A voltage balancing method comprising the step of communicating with a voltage balancing device provided in another energy storage module to perform voltage balancing among a plurality of energy storage modules.

12. The step of performing voltage balancing among the energy storage modules is: The steps include measuring the voltage value of the energy storage module on which the voltage balancing device is installed, The steps include communicating with other voltage balancing devices installed in other energy storage modules to receive the voltage values ​​of those other energy storage modules, The voltage balancing method according to claim 11, further comprising the step of performing voltage balancing of an energy storage module equipped with a voltage balancing device based on the measured voltage value and the received voltage value of another energy storage module.

13. The aforementioned receiving step is, The voltage value is received via CAN communication message with the aforementioned other voltage balancing device. The voltage balancing method according to claim 12, wherein in the ID field of the CAN communication message, the node IDs of energy storage modules connected in series are the same, and the module IDs of each energy storage module are different.

14. The step of performing voltage balancing of an energy storage module equipped with the aforementioned voltage balancing device is: The voltage balancing method according to claim 12, wherein if the measured voltage value is greater than or equal to a predetermined value than the average voltage value of other energy storage modules, the voltage balancing of the energy storage module equipped with the voltage balancing device is performed.

15. The step of performing voltage balancing of an energy storage module equipped with the aforementioned voltage balancing device is: The voltage balancing method according to claim 12, wherein if the difference between the maximum voltage value and the minimum voltage value among the voltage values ​​of other energy storage modules is greater than a predetermined critical value, and the measured voltage value is greater than the average of the maximum voltage value and the minimum voltage value, the voltage balancing of the energy storage module equipped with the voltage balancing device is performed.

16. The voltage balancing method according to claim 12, further comprising the step of performing voltage balancing of an energy storage module equipped with the voltage balancing device if the measured voltage value is equal to or greater than a notification reference value.

17. The voltage balancing method according to claim 12, further comprising the step of performing voltage balancing between unit cells within an energy storage module after the voltage balancing of the energy storage module in which the voltage balancing device is provided has been completed.

18. The step of performing voltage balancing between the unit cells is: The steps include measuring the voltage value of a unit cell, The voltage balancing method according to claim 17, further comprising the step of performing voltage balancing of a specific unit cell if the voltage value of the specific unit cell is greater than or equal to a predetermined value than the average voltage value of other unit cells.

19. The step of performing voltage balancing between the unit cells is: The steps include measuring the voltage value of a unit cell, A voltage balancing method according to claim 17, comprising the step of performing voltage balancing of a specific unit cell if the difference between the maximum voltage value and the minimum voltage value of other unit cells other than the specific unit cell is greater than a predetermined critical value, and the voltage value of the specific unit cell is greater than the average of the maximum voltage value and the minimum voltage value.

20. The step of performing voltage balancing between the unit cells is: The steps include measuring the voltage value of a unit cell, The voltage balancing method according to claim 17, further comprising the step of performing voltage balancing of a specific unit cell if the voltage value of the specific unit cell is equal to or greater than a notification reference value.

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