Battery management device, battery system and battery module assembly balancing method

Abstract

A battery system including a battery rack having a plurality of battery module assemblies (BMAs) according to an embodiment of the present invention may include: a first battery management device (RBMS) for controlling the battery rack, wherein the first battery management device is configured to periodically determine whether one or more conditions for performing BMA balancing are satisfied according to whether the battery system is in an idle state and according to a state of charge of the battery system, and determine a BMA balancing target and a BMA balancing time if the conditions for performing BMA balancing are satisfied; and a second battery management device (PBMS) located in the battery module assembly and including a balancing circuit, wherein the second battery management device is configured to receive a BMA balancing command including a BMA balancing target and a BMA balancing time from the first battery management device and perform cell balancing.

Description

Technical Field

[0001] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0075256 filed in the Korean Intellectual Property Office on June 13, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a battery management device, a battery management system, and a method for balancing a battery module assembly, and more particularly to a battery management device, a battery management system, and a method for performing balancing between battery module assemblies in a battery rack including a plurality of battery module assemblies. Background Art

[0003] Secondary batteries that can be recharged and reused are manufactured as battery modules or packs by connecting multiple battery cells in series based on the required output capacity, and are used as power sources for various applications. These batteries are used in small high-tech electronic devices such as smartphones and in various fields including electric bicycles, electric vehicles, and energy storage systems (ESS).

[0004] If some cells encounter overvoltage, overcurrent or overheating, a battery module or pack including a plurality of battery cells faces safety and operating efficiency problems, thus requiring detection means. Therefore, a battery module or battery pack is equipped with a battery management system (BMS) that measures the voltage value of the corresponding battery cell and monitors and controls the voltage state of the battery cell based on the measured value.

[0005] Meanwhile, the voltage deviation between battery cells that occurs due to various factors and the cell balancing of the battery management system may reduce the voltage deviation. However, when replacing a battery module in a system including a plurality of battery modules, a problem arises in that efficient inter-module balancing and inter-cell balancing cannot be expected using only the existing cell balancing function. Summary of the invention

[0006] [Technical issues]

[0007] To achieve the purpose of the present disclosure, an embodiment of the present invention provides a battery management device for performing balancing between battery module assemblies.

[0008] According to another embodiment of the present disclosure, an embodiment of the present invention provides a method for performing balancing between battery module assemblies.

[0009] According to another embodiment of the present disclosure, an embodiment of the present invention provides a battery system for performing balancing between battery module assemblies.

[0010] [Technical solution]

[0011] In order to achieve the purpose of the present disclosure, a battery management device according to an embodiment may control a battery system including a plurality of battery module assemblies (BMAs) and include at least one processor; and a memory configured to store at least one instruction executed by the at least one processor. The at least one instruction executed by the at least one processor may include: an instruction for periodically determining whether one or more conditions for performing BMA balancing are met according to whether the battery system is in an idle state and according to a state of charge of the battery system; and an instruction for performing BMA balancing by determining a BMA balancing target and a BMA balancing time when the conditions for performing BMA balancing are met.

[0012] Here, whether the battery system is in the idle state is determined according to whether the value of the current flowing in the battery system is less than a predetermined current threshold value.

[0013] Instructions for determining whether one or more conditions for performing BMA balancing are met may include: instructions for determining whether the battery system remains in an idle state for a specific period of time without performing charging or discharging; and instructions for determining whether the charge state of the battery system exceeds a determined reference.

[0014] Instructions for performing BMA balancing may include: instructions for calculating the SOC difference of each battery module assembly compared to a battery module assembly having a minimum state of charge (SOC) in the battery system; and instructions for selecting all cells in the corresponding battery module assembly as balancing targets when the SOC difference of the corresponding battery module assembly compared to the minimum SOC is greater than or equal to an SOC difference threshold.

[0015] The at least one instruction may further include an instruction for transmitting a BMA balancing command including information about the selected balancing target and the determined balancing time to the balancing target battery module assembly.

[0016] According to another embodiment of the present disclosure, a battery module assembly (BMA) balancing method in a battery rack including a plurality of battery module assemblies (BMAs) may include: a first battery management device configured to control the battery rack periodically determining whether one or more conditions for performing BMA balancing are met based on whether a battery system including the battery rack is in an idle state and based on a charge state of the battery system; and the first battery management device performing BMA balancing by determining a BMA balancing target and a BMA balancing time when the conditions for performing BMA balancing are met.

[0017] Determining whether one or more conditions for performing BMA balancing are satisfied may include determining whether the battery system remains in an idle state for a certain period of time without performing charging or discharging; and determining whether a state of charge of the battery system exceeds a determined reference.

[0018] Performing BMA balancing may include calculating a state of charge (SOC) difference of each battery module assembly compared to a battery module assembly having a minimum SOC in the battery system; and selecting all cells in the corresponding battery module assembly as balancing targets if the SOC difference of the corresponding battery module assembly compared to the minimum SOC is greater than or equal to an SOC difference threshold.

[0019] The method may further include transmitting a BMA balancing command including information about the selected balancing target and the determined balancing time to the balancing target battery module assembly.

[0020] The method may further include receiving, by a second battery management device in the balancing target battery module assembly, a BMA balancing command; and performing, by the second battery management device, cell balancing on all cells in the balancing target battery module assembly using an internal balancing circuit.

[0021] The method may further include determining, by the second battery management device, whether the SOC deviation of each cell falls within a range between a first value and a second value; and performing cell balancing, by the second battery management device, on each cell whose SOC deviation falls within the range between the first value and the second value.

[0022] Here, the SOC difference threshold for BMA balancing may be determined to be equal to a first value.

[0023] Meanwhile, whether the battery system is in an idle state is determined according to whether the value of the current flowing in the battery system is less than a predetermined current threshold.

[0024] According to another embodiment of the present disclosure, a battery system including a battery rack having a plurality of battery module assemblies (BMAs) may include: a first battery management device for controlling the battery rack, wherein the first battery management device is configured to periodically determine whether one or more conditions for performing BMA balancing are met based on whether the battery system including the battery rack is in an idle state and based on a charge state of the battery system, and determine a BMA balancing target and a BMA balancing time when the conditions for performing BMA balancing are met; and a second battery management device, which is located in the battery module assembly and includes a balancing circuit, wherein the second battery management device is configured to receive a BMA balancing command including a BMA balancing target and a BMA balancing time from the first battery management device and perform single-cell balancing.

[0025] The first battery management device may be configured to determine whether one or more conditions for performing BMA balancing are satisfied by determining whether the battery system remains in an idle state for a certain period of time without performing charging or discharging and determining whether a charge state of the battery system exceeds a determined reference.

[0026] The first battery management device can be configured to calculate the SOC difference of each battery module assembly compared to a battery module assembly having a minimum state of charge (SOC) in the battery system, select all cells in the corresponding battery module assembly as balancing targets when the SOC difference of the corresponding battery module assembly compared to the minimum SOC is greater than or equal to an SOC difference threshold, and send a BMA balancing command including information about the selected balancing target and the determined balancing time to the balancing target battery module assembly.

[0027] Meanwhile, the second battery management device may be configured to receive the BMA balancing command from the first battery management device and perform cell balancing for the balancing time on all cells in the balancing target battery module assembly using the balancing circuit.

[0028] In addition, the second battery management device can also perform the following steps: Figure 2 In other words, the second battery management device may determine whether the SOC deviation of each cell compared to the minimum cell SOC falls within a range between a first value and a second value; and perform cell balancing on each cell where the SOC deviation of the cell falls within the range between the first value and the second value. Here, the first value may be, for example, 2.5%, and the second value may be, for example, 10%.

[0029] Here, the minimum cell SOC among the cell SOCs of multiple cells in the battery system can be calculated by the RBMS, which can be a first battery management device. In other words, the RBMS can obtain battery state information from multiple second battery management devices, calculate the minimum cell SOC, and provide the calculated information to multiple second battery management devices.

[0030] Meanwhile, it may be determined that the SOC difference threshold for performing BMA balancing according to an embodiment of the present invention may be determined to be equal to a lower limit value of a cell SOC deviation according to a general cell balancing condition.

[0031] [Beneficial Effects]

[0032] According to the embodiments of the present invention as described above, balancing between modules can be performed using an existing cell balancing circuit without adding a separate hardware configuration for balancing between modules and without interfering with a general cell balancing function performed in the past.

[0033] Therefore, when a battery module assembly is replaced or expanded in a system including a plurality of battery module assemblies, the SOC difference between the battery module assemblies may be efficiently adjusted. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1is a block diagram showing the structure of a battery module assembly and a battery management device to which an embodiment of the present invention may be applied.

[0035] Figure 2 This is a conceptual diagram that explains the general monomer balance.

[0036] Figure 3 1 is a diagram illustrating a problem of cell balance when replacing a battery module assembly in a conventional battery system.

[0037] Figure 4 An operation sequence of a balancing method between battery module assemblies according to an embodiment of the present invention is shown.

[0038] Figure 5 A detailed operation sequence of the preprocessing steps according to an embodiment of the present invention is shown.

[0039] Figure 6 A detailed operation sequence of the entry condition determination step according to an embodiment of the present invention is shown.

[0040] Figure 7 A detailed operational sequence of a BMA balancing step according to an embodiment of the present invention is shown.

[0041] Figure 8 is a block diagram of a rack BMS and a group BMS according to an embodiment of the present invention.

[0042] Fig. 9 is a diagram for explaining a BMA balancing concept and a balancing execution result according to an embodiment of the present invention when a battery module assembly is replaced.

[0043] 100: Battery Module Assembly (BMA)

[0044] 110: Group BMS (PBMS)

[0045] 111: Controller

[0046] 113: Single cell balancing module

[0047] 115: Communication module

[0048] 200: BMS (RBMS)

[0049] 210: Controller

[0050] 220: Communication module DETAILED DESCRIPTION

[0051] The present invention can be modified in various forms and have various embodiments, and its specific embodiments are shown in the accompanying drawings by way of example and will be described in detail below. However, it should be understood that it is not intended to limit the present invention to specific embodiments, on the contrary, the present invention will cover all modifications, equivalents and substitutions that fall within the spirit and technical scope of the present invention. Throughout the description of the drawings, the same reference numerals refer to the same elements.

[0052] It will be understood that although various elements may be described herein using terms such as first, second, A, B, etc., these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the present invention. As used herein, the term "and / or" includes any one of a combination of a plurality of associated listed items or a plurality of associated listed items.

[0053] It will be understood that when an element is referred to as being "coupled" or "connected" to another element, it can be directly coupled or connected to the other element, or intervening elements may be present. Conversely, when an element is referred to as being "directly coupled" or "directly connected" to another element, there are no intervening elements.

[0054] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms "one", "an" and "the" are also intended to include plural forms. It will be further understood that the terms "include", "comprise", "cover", "contain" and / or "have" specify the existence of stated features, integers, steps, operations, constituent elements, parts and / or combinations thereof when used herein, but do not exclude the existence or addition of one or more other features, integers, steps, operations, constituent elements, parts and / or combinations thereof.

[0055] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such herein.

[0056] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0057] Figure 1 is a block diagram showing the structure of a battery module assembly and a battery management device to which an embodiment of the present invention may be applied.

[0058] refer to Figure 1 , each battery module assembly may include a plurality of battery cells connected in series. The most commonly used battery cell is a lithium-ion (Li-Ion) battery cell. The battery module assembly may be connected to a load through a positive terminal and a negative terminal and perform a charge / discharge operation. The battery module assembly may be configured to be connected in series / parallel according to the requirements of the system in which the battery is applied, and the battery module assembly is Figure 1 In the example shown in , the two are connected in series.

[0059] The battery module assembly 100 generally includes a battery management system (PBMS) for managing a battery module (or battery pack) including a plurality of battery cells connected in series. The PBMS 110 according to an embodiment of the present invention may include various components such as fuses, current sensing elements, thermistors, switches, and balancers, and may be implemented in the form of a printed circuit board (PCB). In other words, the battery module assembly 100 may be a module including a plurality of cells and a PBMS PCB, and may be connected in series with other battery module assemblies to form a battery rack, such as Figure 1 as shown in .

[0060] The pack battery management system (PBMS) 110 can monitor the current, voltage and temperature of each battery module to be managed, calculate the state of charge (SOC) based on the monitoring results, and control charging and discharging. Here, SOC refers to the current state of charge (or charge amount) of the battery, expressed in percentage points [%).

[0061] The group battery management system 110 may monitor battery cells, read cell voltages, and send them to a rack BMS or other components, devices, or systems connected to the battery. A rack BMS (RBMS) 200 is a battery management system that manages a rack including a plurality of battery module assemblies (BMAs) and is linked to a group BMS of each battery module assembly. In the present invention, unlike the PBMS 110, the RBMS 200 does not include a separate balancing circuit therein.

[0062] Meanwhile, the PBMS 110 and the RBMS 200 may include communication modules therein respectively to communicate with each other and with other devices and systems within the device including the battery system. The communication module of the BMS may communicate with other systems using a controller area network (CAN) or Ethernet. When using CAN communication, components, modules or systems in the BMS may be connected to each other via a CAN bus.

[0063] Meanwhile, the plurality of battery cells included in the battery module may not have exactly the same characteristics, and voltage deviation may occur between the cells connected in series due to natural discharge of each cell, environmental factors during use, etc. The PBMS 110 may include a cell balancing (CB) circuit that performs a balancing operation to evenly balance the charges of the battery cells to extend the life of the battery pack. For some reason, the capacity of the cell balancing circuit may be limited by hardware. For example, due to limitations in wattage, resistance value, and thermal durability of the cell balancing circuit, the cell balancing capacity that can be provided may be limited.

[0064] In addition, the PBMS 110 may include a microcontroller unit (MCU) or a battery monitoring integrated chip (BMIC) for controlling the internal components described above in conjunction with them. Here, the BMIC is located inside the BMS and may be an IC type component that measures information such as voltage, temperature, and current of a battery cell / module.

[0065] In the present invention, the BMIC can measure the voltage of cells in the battery module assembly to which the BMIC belongs according to a command from the RBMS 200 , report the cell voltage to the RBMS 200 , and perform on / off control of field effect transistor (FET) elements in a balancing circuit.

[0066] Figure 2 This is a conceptual diagram that explains the general monomer balance.

[0067] like Figure 2 As shown in , a plurality of battery cells included in a battery module have SOC variations between cells due to natural discharge of each cell, environmental factors during use, etc. Cell balancing performed by a pack BMS in order to reduce SOC deviation is generally performed using a balancing circuit including a switch (e.g., a transistor) and a resistor arranged for each cell, which is controlled by a control unit.

[0068] The cell balancing operation may be performed by discharging cells having SOC deviations within a specific range having upper and lower limits with respect to the lowest SOC. Cell balancing may be performed, for example, by discharging individual cells having SOC deviations within a range of 2.5% to 10%. Figure 2 In the example of FIG. 1 , the lowest SOC in one module is 54%, and it can be understood that cell balancing is performed for cells 1, 3, and 5 having deviations between 2.5% and 10% with respect to the lowest SOC. Here, 2.5% may be defined as a lower limit of the cell SOC deviation for cell balancing, and 10% may be defined as an upper limit of the cell SOC deviation for cell balancing.

[0069] Here, for example, the SOC deviation range for cell balancing refers to the SOC deviation between cell groups, which is the SOC error range caused by the manufacturing process that may occur in a battery cell production line. For some reason, a cell (such as Figure 2 The monomer 4) with a SOC of 65% is judged as a defective monomer and does not undergo monomer equilibrium, but is highlighted in a defective state.

[0070] Meanwhile, in this case, when some of the multiple BMAs in the battery system are replaced, new, unused BMAs are often applied to the battery use field as is, in which case the new BMA may have a greater SOC difference than the SOC of the BMA that has been installed and in use.

[0071] Figure 3 1 is a diagram illustrating a problem of cell balance when replacing a battery module assembly in a conventional battery system.

[0072] refer to Figure 3 In the example shown in , the SOC of BMA3, which is already used in the existing system, is 41.25%, the average monomer SOC of the newly added BMA1 is 69.5%, and the average monomer SOC of the newly added BMA2 is 49.75%. Here, the lowest monomer SOC among the monomer SOCs in the system is 39%, and based on this, monomer balancing can be performed only for monomers with an SOC deviation within 10%. In other words, in the newly added BMA, monomer balancing is performed only for monomers 2 and 4 in BMA2, and not for all monomers in BMA1 and not for monomers other than monomers 2 and 4 in BMA2. Therefore, even if the monomers are normal, there will be a problem that the SOC deviation between the monomers still exists even after the monomer balancing is completed.

[0073] In summary, conventional cell balancing is not performed on cells having an SOC deviation of 10% or more compared to the lowest cell SOC among all cells, and thus, the remaining SOC deviation between BMAs results in a reduction in battery charge and discharge performance.

[0074] Therefore, the present invention is proposed to solve this problem and provide a balancing method for a battery rack, which includes a two-step balancing operation (balancing between battery module assemblies and general single-cell balancing).

[0075] Figure 4 An operation sequence of a balancing method between battery module assemblies according to an embodiment of the present invention is shown.

[0076] The balancing method between battery module assemblies according to an embodiment of the present invention can be performed by a rack BMS or a controller in the rack BMS, the rack BMS being a battery management device that manages a battery rack. The balancing method of a battery rack according to an embodiment of the present invention can also be performed by a rack BMS and a battery pack BMS.

[0077] The balancing method between battery module assemblies according to an embodiment of the present invention may include a pre-processing ( S100 ) step, an entry condition determination ( S200 ) step, and a BMA balancing execution ( S300 ) step.

[0078] The pre-processing ( S100 ) step may be a step of checking a balancing execution period, determining whether the period has been reached, and deciding whether to further proceed to the entry condition determination step.

[0079] The entry condition determination ( S200 ) step may be a step of determining whether conditions for performing BMA balancing are satisfied, the conditions including whether the battery is in an idle state and whether a suitable SOC is ensured to perform balancing.

[0080] In other words, through the preprocessing ( S100 ) step and the entry condition determination ( S200 ) step according to the embodiment of the present invention, it can be determined whether the BMA balancing execution condition is satisfied according to whether the battery system is in an idle state and according to the charge state of the battery.

[0081] In the BMA balancing execution (S300) step, a balancing target BMA may be selected and a balancing time may be determined. In addition, a balancing execution command and a balancing time are sent to the selected target BMA, thereby allowing the PBMS within the target BMA to perform balancing using a single cell balancing circuit.

[0082] In summary, a battery module assembly balancing method according to an embodiment of the present invention is a BMA balancing method in a battery rack including a plurality of battery module assemblies (BMAs), wherein a first battery management device configured to control the battery rack can periodically determine whether one or more conditions for performing BMA balancing are met based on whether the battery system is in an idle state and based on a charge state of the battery system, and can perform BMA balancing by determining a BMA balancing target and a BMA balancing time when the conditions for performing BMA balancing are met.

[0083] Determining whether one or more conditions for performing BMA balancing are satisfied may include determining whether the battery system remains in an idle state for a certain period of time without performing charging or discharging, and determining whether a state of charge of the battery system exceeds a determined reference.

[0084] Performing BMA balancing may include: calculating a state of charge (SOC) difference of each battery module assembly compared to a battery module assembly having a minimum SOC in the battery system; and selecting all cells in the corresponding battery module assembly as balancing targets if the SOC difference of the corresponding battery module assembly compared to the minimum SOC is greater than or equal to a SOC difference threshold.

[0085] The method may further include transmitting a BMA balancing command including information about the selected balancing target and the determined balancing time to the balancing target battery module assembly.

[0086] The method may further include: receiving, by a second battery management device in the balancing target battery module assembly, a BMA balancing command; and performing, by the second battery management device, cell balancing on all cells in the balancing target battery module assembly using an internal balancing circuit.

[0087] The method may also include: determining, by a second battery management device, whether an SOC deviation of each cell compared to a minimum SOC falls within a range between a first value and a second value; and performing cell balancing on each cell by the second battery management device, wherein the SOC deviation of the cell falls within the range between the first value and the second value.

[0088] Here, the SOC difference threshold for BMA balancing is determined to be equal to the first value.

[0089] Meanwhile, whether the battery system is in an idle state is determined according to whether the value of the current flowing in the battery system is less than a predetermined current threshold.

[0090] Figure 5 A detailed operation sequence of the preprocessing steps according to an embodiment of the present invention is shown.

[0091] Specifically, in the preprocessing (S100) step, for example, in the case where the balancing execution cycle is set to one day (24 hours), it is checked whether the counting variable Day_count has reached 86400 (S110). If the value has not been reached, the value of the variable Day_count is increased by 1 (S120). The step (S110) of checking whether the counting variable Day_count has reached 86400 (=60*60*24) can be performed in a 1-second cycle. For example, after one day from the initial value 0, Day_count reaches 86400, which can be seen that the balancing execution cycle (ie, one day) has been reached. In this case, the value of the variable Day_flag indicating that the balancing cycle has been reached can be set to "1", and the value of the counting variable Day_count can be initialized to "0" (S130).

[0092] Figure 6A detailed operation sequence of the entry condition determination step according to an embodiment of the present invention is shown.

[0093] refer to Figure 6 In the step of determining the entry condition for performing balancing, the value of the variable Day_flag is checked to determine whether one day as a balancing execution period has passed (S201). After one day has passed, the value of the variable Day_flag is set to 1, as shown above Figure 5 Therefore, if the balancing execution period (for example, one day) has not elapsed since the previous balancing execution (No in S201), the entry condition determination process is not executed and the entry condition determination process is terminated immediately.

[0094] If the value of the variable Day_flag is 1 (Yes in S201 ), it is checked whether a target BMA as a target of balancing has been determined ( S210 ). If a balancing target BMA has been specified (No in S210 ), subsequent processes may not be performed and this process may be terminated.

[0095] If the target BMA is not determined (ie, the target BMA=0), a subsequent process is performed to check whether the battery is in an idle state (S220). This can be done by checking whether the current flowing through the battery is less than a current threshold (I th ) to check whether the battery is in an idle state. Here, the current threshold (I th ) may be set to, for example, 1.89 A, but is not limited thereto. If the battery is in an idle state, it may be further checked whether a specific time period has elapsed in the idle state (S230). Here, the specific time period may be set to, for example, 30 minutes.

[0096] If the battery has been in an idle state for a certain period of time, it is checked whether the SOC of the battery is equal to or higher than a certain reference value (SOC_th) (S240), and if the condition that the SOC of the battery is equal to or higher than the certain reference value is satisfied, the process proceeds to the next step. Here, the SOC of the battery may be an average SOC value of all battery module assemblies included in the battery system. Here, for example, the specific reference value of the SOC may be determined to be 46%, but the scope of the present invention is not limited to this value.

[0097] In summary, the entry condition determination step is a step of determining whether the condition for performing BMA balancing is satisfied, which is a process of checking whether the battery is in an idle state for a certain period of time or longer and whether the charge state of the battery is sufficient to perform balancing.

[0098] Figure 7 A detailed operational sequence of a BMA balancing step according to an embodiment of the present invention is shown.

[0099] exist Figure 7 In the BMA balancing execution step shown in , a balancing target BMA may be selected and a balancing time may be determined, and a balancing execution command and information on the balancing time may be sent to the selected target BMA.

[0100] More specifically, the value of a variable n representing a battery module assembly (BMA) may be set to 0 (S310), and it is checked whether the value of the variable n reaches the total number of battery module assemblies in the system (S320). If the value of n does not reach the total number of battery module assemblies (Yes in S320), it may be checked whether the SOC difference (BMA_soc_diff) between the BMAs (which is defined as the value of the difference between the SOC (BMA_SOC[n]) of the corresponding BMA and the SOC (Min_BMA_SOC) of the minimum BMA SOC (S330)) is greater than or equal to the SOC difference threshold (SOC_diff_th) (S350). If the SOC difference of the corresponding BMA compared to the minimum BMA SOC is greater than or equal to the SOC difference threshold, all cells in the corresponding BMA (e.g., 14 cells included in the battery module assembly) are selected as balancing targets (S370). The operations of S330, S350, and S370 described above may be performed for all BMAs in the system while increasing the variable n (S351).

[0101] Meanwhile, when the SOC difference comparison and balancing target selection for all BMAs are completed (No in S320), it is checked again whether a balancing target has been selected (S340) and the balancing time is determined (S341). Here, the balancing time may be set to a value of, for example, 8245 seconds (=cell capacity (71 Ah) * 3600 s * cell balancing amount (0.1%) / balancing current (31 mA)), but is not limited thereto.

[0102] Once the balancing target and balancing time are determined, a balancing command with balancing time information may be sent to the balancing target BMA (S390). Here, multiple balancing target BMAs may be selected, and in this case, a balancing command and balancing time information may be sent to each group BMS in the multiple target BMAs.

[0103] Figure 8 is a block diagram of a rack BMS and a group BMS according to an embodiment of the present invention.

[0104] As previously in Figure 1 As seen in FIG. 1 , the rack BMS 200 may interoperate with all battery module assemblies (BMAs) included in the rack and communicate with the group BMS 110 within each battery module assembly.

[0105] refer to Figure 8, the group BMS 110 according to an embodiment of the present invention may include a controller (MCU; micro control unit) 111, a single cell balancing module 113 and a communication module 115. In this specification, the controller may be referred to as a processor, a control unit, an MCU, etc., and may refer to a dedicated processor on which the method of the embodiment of the present invention is executed. In addition, the controller 111 may be provided in the form of a battery monitoring integrated chip (BMIC). The BMIC located in each group BMS 110 can measure the voltage of each single cell according to a command from the RBMS 200, report it to the RBMS 200, and perform on / off control on the FET element in the balancing circuit.

[0106] The RBMS 200 may include a controller 210 and a communication module 220. The controller 210 of the RBMS 200 may calculate a BMA voltage based on each cell voltage measured and reported by the BMIC, and calculate a BMA SOC based on the BMA voltage. The controller 210 may select a BMA balancing target using the calculated BMA SOC, and transmit information about the selected target to a controller 111 (e.g., BMIC) of the group BMS 110. The controller of the group BMS 110, which has received the information, may perform balancing on the target cell using a cell balancing circuit 113. Here, balancing may be a discharging operation performed for each cell during a determined balancing time.

[0107] In summary, a battery system according to an embodiment of the present invention may be a battery system having a battery rack including a plurality of battery module assemblies (BMAs), wherein a first battery management device for controlling the battery rack periodically determines whether one or more conditions for performing BMA balancing are met based on whether the battery system is in an idle state and based on a charge state of the battery system, and determines a BMA balancing target and a BMA balancing time when the conditions for performing BMA balancing are met, and a second battery management device located in the battery module assembly and including a balancing circuit receives a BMA balancing command including a BMA balancing target and a BMA balancing time from the first battery management device and performs cell balancing.

[0108] The first battery management device may determine whether one or more conditions for performing BMA balancing are satisfied by determining whether the battery system remains in an idle state for a certain period of time without performing charging or discharging, and determines whether the state of charge of the battery system exceeds a determined reference.

[0109] In addition, the first battery management device can calculate the SOC difference of each battery module assembly compared with the battery module assembly having the minimum state of charge (SOC) in the battery system, select all cells in the corresponding battery module assembly as balancing targets when the SOC difference of the corresponding battery module assembly compared with the minimum SOC is greater than or equal to the SOC difference threshold, and send a BMA balancing command including information about the selected balancing target and the determined balancing time to the target BMA.

[0110] Meanwhile, the second battery management device may receive the BMA balancing command from the first battery management device and perform cell balancing for the balancing time on all cells in the balancing target battery module assembly using the balancing circuit.

[0111] In addition, the second battery management device can also perform the following steps: Figure 2 In other words, the second battery management device may determine whether the SOC deviation of each cell compared to the minimum cell SOC falls within a range between a first value and a second value; and perform cell balancing on each cell if the SOC deviation of the cell falls within the range between the first value and the second value. Here, the first value may be, for example, 2.5%, and the second value may be, for example, 10%.

[0112] Here, the minimum cell SOC among the cell SOCs of multiple cells in the battery system can be calculated by the RBMS, which can be a first battery management device. In other words, the RBMS can obtain battery state information from multiple second battery management devices, calculate the minimum cell SOC, and provide the calculated information to multiple second battery management devices.

[0113] Meanwhile, the SOC difference threshold for performing BMA balancing according to an embodiment of the present invention may be determined to be equal to a lower limit value of a cell SOC deviation according to a general cell balancing condition.

[0114] In addition, the battery management device 200 for controlling a battery rack including a plurality of battery module assemblies (BMAs) may include: at least one processor; and a memory configured to store at least one instruction executed by the at least one processor, and the at least one instruction may include: instructions for periodically determining whether one or more conditions for performing BMA balancing are met based on whether the battery rack is in an idle state and based on a charge state of the battery rack; and instructions for performing BMA balancing by determining a BMA balancing target and a BMA balancing time when the conditions for performing BMA balancing are met.

[0115] Here, whether the battery rack is in the idle state may be determined according to whether the value of the current flowing in the battery rack is less than a predetermined current threshold.

[0116] Instructions for determining whether one or more conditions for performing BMA balancing are met may include: instructions for determining whether a battery rack remains in an idle state for a certain period of time without performing charging or discharging; and instructions for determining whether a state of charge of the battery rack exceeds a determined reference.

[0117] Instructions for performing BMA balancing may include: instructions for calculating the SOC difference of each battery module assembly compared to a battery module assembly having a minimum state of charge (SOC) in the battery rack; and instructions for selecting all cells in the corresponding battery module assembly as balancing targets if the SOC difference of the corresponding battery module assembly compared to the minimum SOC is greater than or equal to an SOC difference threshold.

[0118] The at least one instruction may further include an instruction for sending a BMA balancing command including information about the selected balancing target and the determined balancing time to the balancing target battery module assembly.

[0119] Fig. 9 is a diagram for explaining a BMA balancing concept and a balancing execution result according to an embodiment of the present invention when a battery module assembly is replaced.

[0120] As seen above, the BMA balancing according to an embodiment of the present invention can correct the SOC of the BMA whose SOC difference exceeds the SOC difference threshold (e.g., 2.5%) based on the BMA with the lowest SOC. In other words, discharge is performed on all cells in the BMA where a specific deviation range occurs. The corresponding SOC difference is a BMA-to-BMA difference that is not associated with a defective cell. The BMA balancing that solves the corresponding SOC difference according to an embodiment of the present invention can be performed mainly for the purpose of minimizing the SOC difference when replacing a battery module assembly, and can be operated before performing a general cell balancing operation.

[0121] More specifically, refer to Fig. 9 , assuming that when the SOC of BMA3 in use in the existing system is 41.25%, BMA1 and BMA2 are newly installed. The SOC of the newly added BMA1 is 69.5%, and the SOC of BMA2 is 49.75%. According to an embodiment of the present invention, the SOCs of the corresponding BMAs are compared, and the SOC of the BMA may be set to the average SOC of all cells included in the BMA.

[0122] exist Fig. 9In the system shown in , the lowest BMA SOC is 41.25%, and compared with the lowest BMA SOC, both the SOC of BMA1 and the SOC of BMA2 have an SOC difference of more than 2.5%. Therefore, it is necessary to perform BMA balancing according to the present invention on BMA1 and BMA2, and as a result of balancing, both the SOCs of BMA1 and BMA2 are adjusted to have a BMA SOC of 43.75%.

[0123] After BMA balancing, monomer balancing can be performed for each monomer and can be performed in conjunction with Figure 2 The cell balancing for each cell is performed in the same operation as the general cell balancing described in . Meanwhile, the SOC difference threshold for performing BMA balancing according to an embodiment of the present invention may be set equal to the lower limit value of the cell SOC deviation of the general cell balancing condition.

[0124] In the embodiments of the present invention, balancing between battery modules may be performed using an existing cell balancing circuit without adding a separate component for balancing between battery modules and without interfering with a general cell balancing function that was performed in the past.

[0125] Therefore, when a battery module assembly is replaced or expanded in a system including a plurality of battery module assemblies, the SOC difference between the battery module assemblies may be efficiently adjusted.

[0126] The operation of the method according to an embodiment of the present invention can be implemented as a computer-readable program or code on a computer-readable recording medium. The computer-readable recording medium includes all types of recording devices having data readable by a computer system stored therein. In addition, the computer-readable recording medium can be distributed in a network-connected computer system, thereby storing and executing a computer-readable program or code in a distributed manner.

[0127] In addition, the computer-readable recording medium may include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. The program instructions may include not only machine language codes created by a compiler, but also high-level language codes that can be executed by a computer using an interpreter.

[0128] Although some aspects of the present invention have been described in the context of an apparatus, it can also be represented by a description according to a corresponding method, wherein a block or apparatus corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method can also represent features of a corresponding block or item or a corresponding apparatus. Some or all of the method steps can be performed by (or using) a hardware device such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, one or more of the most important method steps can be performed by such an apparatus.

[0129] In the foregoing, the present invention has been described with reference to exemplary embodiments thereof, but those skilled in the art will appreciate that various modifications and changes may be made to the present invention within the scope without departing from the spirit and area of ​​the invention described in the appended claims.

Claims

1. A battery management device for controlling a battery system including a plurality of battery module assemblies, the battery management device comprising: at least one processor; as well as A memory configured to store at least one instruction executed by the at least one processor, the at least one instruction comprising: instructions for periodically determining whether one or more conditions for performing battery module assembly balancing are satisfied based on whether the battery system is in an idle state and based on a state of charge of the battery system; as well as Instructions for performing battery module assembly balancing by determining a battery module assembly balancing target and a battery module assembly balancing time if the condition for performing battery module assembly balancing is satisfied.

2. The battery management device of claim 1, wherein the instructions for determining whether the one or more conditions for performing battery module assembly balancing are satisfied comprise: instructions for determining whether the battery system remains in an idle state for a specific period of time without performing charging or discharging; as well as Instructions for determining whether the state of charge of the battery system exceeds a determined reference.

3. The battery management device according to claim 1, wherein the instruction for performing battery module assembly balancing comprises: instructions for calculating a state of charge difference of each battery module assembly compared to a battery module assembly having a minimum state of charge in the battery system; as well as Instructions for selecting all cells in the corresponding battery module assembly as balancing targets if the state of charge difference of the corresponding battery module assembly compared to the minimum state of charge is greater than or equal to a state of charge difference threshold.

4. The battery management device according to claim 3, wherein the at least one instruction further comprises: An instruction for transmitting a battery module assembly balancing command including information on the selected balancing target and the determined balancing time to the balancing target battery module assembly. 5 . The battery management device according to claim 1 , wherein whether the battery system is in an idle state is determined according to whether a value of a current flowing in the battery system is less than a predetermined current threshold value.

6. A battery module assembly balancing method in a battery rack including a plurality of battery module assemblies, the battery module assembly balancing method comprising: A first battery management device configured to control the battery rack periodically determines whether one or more conditions for performing battery module assembly balancing are met according to whether the battery system including the battery rack is in an idle state and according to a charge state of the battery system; as well as The first battery management device performs battery module assembly balancing by determining a battery module assembly balancing target and a battery module assembly balancing time when the condition for performing battery module assembly balancing is satisfied.

7. The battery module assembly balancing method according to claim 6, wherein determining whether the one or more conditions for performing battery module assembly balancing are satisfied comprises: determining whether the battery system remains in an idle state for a certain period of time without performing charging or discharging; as well as A determination is made as to whether the state of charge of the battery system exceeds a determined reference.

8. The battery module assembly balancing method according to claim 6, wherein performing battery module assembly balancing comprises: calculating a state of charge difference of each battery module assembly compared to a battery module assembly having a minimum state of charge in the battery system; as well as When a state of charge difference of a corresponding battery module assembly compared to the minimum state of charge is greater than or equal to a state of charge difference threshold, all cells in the corresponding battery module assembly are selected as balancing targets.

9. The battery module assembly balancing method according to claim 8, further comprising: A battery module assembly balancing command including information on the selected balancing target and the determined balancing time is transmitted to the balancing target battery module assembly.

10. The battery module assembly balancing method according to claim 9, further comprising: The second battery management device in the balancing target battery module assembly receives the battery module assembly balancing command; as well as Cell balancing is performed on all cells in the balancing-target battery module assembly by the second battery management device using an internal balancing circuit.

11. The battery module assembly balancing method according to claim 10, further comprising: Determining, by the second battery management device, whether the charge state deviation of each cell falls within a range between a first value and a second value; as well as Cell balancing is performed by the second battery management device on each cell in which the state of charge deviation falls within a range between the first value and the second value. 12 . The battery module assembly balancing method according to claim 11 , wherein the state of charge difference threshold for battery module assembly balancing is determined to be equal to the first value. 13 . The battery module assembly balancing method according to claim 6 , wherein whether the battery system is in an idle state is determined according to whether a value of a current flowing in the battery system is less than a predetermined current threshold.

14. A battery system comprising a battery rack having a plurality of battery module assemblies, the battery system comprising: a first battery management device for controlling the battery rack, wherein the first battery management device is configured to periodically determine whether one or more conditions for performing battery module assembly balancing are satisfied according to whether the battery system is in an idle state and according to a charge state of the battery system, and determine a battery module assembly balancing target and a battery module assembly balancing time when the conditions for performing battery module assembly balancing are satisfied; as well as A second battery management device is located in the battery module assembly and includes a balancing circuit, wherein the second battery management device is configured to receive a battery module assembly balancing command including the battery module assembly balancing target and the battery module assembly balancing time from the first battery management device and perform cell balancing.

15. A battery system according to claim 14, wherein the first battery management device is configured to determine whether the one or more conditions for performing battery module assembly balancing are met by determining whether the battery rack remains in an idle state for a specific period of time without performing charging or discharging and determining whether the charge state of the battery rack exceeds a determined reference.

16. A battery system according to claim 14, wherein the first battery management device is configured to calculate the charge state difference of each battery module assembly compared with the battery module assembly with the minimum charge state in the battery system, and select all cells in the corresponding battery module assembly as balancing targets when the charge state difference of the corresponding battery module assembly compared with the minimum charge state is greater than or equal to a charge state difference threshold. 17 . The battery system according to claim 16 , wherein the first battery management device is configured to transmit a battery module assembly balancing command including information on the selected balancing target and the determined balancing time to the balancing target battery module assembly.

18. The battery system according to claim 17, wherein the second battery management device is configured to receive the battery module assembly balancing command from the first battery management device, and perform cell balancing for the balancing time on all cells in the balancing target battery module assembly using the balancing circuit.

19. A battery system according to claim 18, wherein the second battery management device is configured to determine whether the charge state deviation of each cell compared to the minimum cell charge state falls within a range between a first value and a second value; and perform cell balancing on each cell whose charge state deviation falls within the range between the first value and the second value. 20 . The battery system of claim 19 , wherein the state of charge difference threshold for battery module assembly balancing is determined to be equal to the first value.

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