Battery cell balance control method, system and equipment for energy storage and frequency modulation, and medium

Abstract

The invention discloses a cell equalization control method, system and device for energy storage and frequency modulation and a medium. The method comprises the steps that a BMS calculates the difference value between the voltage of all single cells and the voltage of the lowest single cell of the system; when the difference value is greater than or equal to a threshold value, marking that equalization is needed; starting equalization for the sorted odd-even number battery cells, and after starting for a preset time, closing equalization for a preset standing time; the operation is repeated until no battery cell needs to be started for equalization; in the energy storage frequency modulation stage, the BMS calculates the capacity difference value between the battery cell and the lowest SOC, and then the needed equalization time is calculated; and when the time that the battery cell needs to start equalization is reduced to 0 or the battery cell needs to stand for preset time again, the BMS jumps out of the capacity equalization state and returns to the voltage equalization state. Through comprehensive monitoring and an accurate judgment mechanism, the problem that the performance of the whole energy storage system is reduced due to abnormal voltage of individual battery cells is avoided, the voltage consistency of the battery cells in the charging and discharging process is ensured, and the stability and reliability of the energy storage system are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage, and relates to a method, system, device and medium for equalizing control of energy storage frequency modulation cells. Background Art

[0002] In current energy storage technologies, whether applied to electric vehicles or industrial and commercial energy storage systems, cell equalization control is a key link to ensure the stable performance of the battery pack and extend its service life. The existing equalization control methods generally use voltage as the main judgment condition for equalization activation, that is, when the voltage difference between cells exceeds a preset threshold, equalization is started, and when the voltage difference drops within the allowable range, equalization is turned off. Although this voltage-based equalization control strategy is simple to implement, it exposes several significant defects in practical applications:

[0003] Insufficient consideration of polarization effect, polarization phenomenon occurs in cells during charge and discharge processes, resulting in a deviation between the measured voltage value and the actual state. If the voltage is simply used as the basis for equalization, after the cell depolarizes, over-discharge of the cell may occur, which not only affects the life of the cell but also may cause potential safety hazards.

[0004] DC internal resistance inconsistency, it is difficult to make the DC internal resistance (DCR) of cells completely consistent during the manufacturing process. The inconsistency will cause voltage deviation between cells under the same current during charge and discharge processes. More importantly, the voltage deviation is closely related to the charge and discharge current, making the equalization strategy based on a fixed voltage threshold difficult to adapt to dynamically changing working conditions.

[0005] Capacity consistency requirement, during the charge and discharge processes of the energy storage system, more attention is paid to the capacity consistency of cells, because the capacity consistency directly affects the overall performance and energy efficiency of the battery pack. According to the relationship between the open circuit voltage (OCV) and capacity, cells with the same capacity should have the same voltage. However, the existing voltage equalization strategies often ignore this point, resulting in the gradual accumulation of cell capacity differences and affecting the long-term stable operation of the energy storage system. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems in the prior art that the voltage-based equalization control method does not consider the polarization effect, DCR inconsistency and capacity consistency requirement of cells, resulting in over-discharge of cells, voltage deviation and accumulation of capacity differences, and to provide a method, system, device and medium for equalizing control of energy storage frequency modulation cells.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for equalizing control of energy storage frequency modulation cells, comprising the following steps:

[0009] During the system initial state or the charge and discharge process, the battery management system BMS calculates the difference between the voltage of each single cell and the voltage of the lowest single cell in the system; when the difference is greater than or equal to a preset voltage difference threshold, the cell is marked as needing equalization;

[0010] The battery management system BMS sorts all the cells that need equalization, turns on the equalization for the odd-numbered cells, and after a preset equalization start time, turns off the equalization for a preset static time; turns on the equalization for the even-numbered cells, and repeatedly operates between the odd and even cells until there are no cells that need to turn on the equalization;

[0011] During the energy storage frequency modulation stage, after a preset static time, the battery management system BMS looks up the state of charge SOC of each cell according to the open-circuit voltage, calculates the capacity difference between each cell and the lowest SOC through the state of charge SOC, and then calculates the equalization time required for each cell to be equalized according to the capacity difference;

[0012] When the time for each cell to turn on the equalization drops to 0 or the system needs to be static for a preset time again, the BMS exits the capacity equalization state and returns to the voltage equalization state.

[0013] During the system initial state or the charge and discharge process, the battery management system BMS calculates the difference between the voltage of each single cell and the voltage of the lowest single cell in the system; specifically: the system initial state trigger is when the energy storage frequency modulation system starts, after the battery management system BMS completes initialization, it triggers the voltage acquisition process, and the battery management system BMS independently starts to monitor the voltage of the cells;

[0014] The charge and discharge process trigger is when the energy storage system performs a charge or discharge operation, the battery management system BMS continuously acquires the cell voltage according to a preset sampling period.

[0015] The battery management system BMS calculates the current capacity Q of each cell according to the SOC of the cell, specifically Q = SOC * Q0, where Q0 is the rated capacity of the cell; and calculates the equalization time T required for each cell to be equalized according to the equalization current I, specifically T = Q / I, where I = U / R, U is the average cell voltage, and R is the equalization resistance.

[0016] When marking the cells, the battery management system BMS uses an internal data structure, including an array or a linked list, assigns a corresponding mark bit to each cell, and when the cell needs equalization, sets its corresponding mark bit to 1; when it does not need equalization, the mark bit is set to 0.

[0017] An equalization control system for cells used in energy storage frequency modulation includes the following modules:

[0018] Balanced startup judgment module. During the initial state of the system or the charge and discharge process, the battery management system (BMS) judges the maximum and minimum values of all battery cells. When the difference between the maximum and minimum values exceeds the set threshold, the balancing of the battery cells is started.

[0019] Voltage balance judgment module. The battery management system (BMS) judges the difference between each battery cell and the lowest single-cell voltage of the system. If the difference exceeds the set threshold, it is considered that this battery cell needs to be balanced; if the difference does not exceed the set threshold, no balancing is required, and all the battery cells in the system are polled once.

[0020] Odd-even balance control module. The battery management system (BMS) polls all the single-cell voltages in the system and identifies the battery cells whose difference from the lowest single cell exceeds the set threshold.

[0021] The battery management system (BMS) controls to first turn on the odd-numbered battery cells that need to be balanced. After the balance is turned on for the set time, then turn on the even-numbered battery cells that need to be balanced.

[0022] After that, it jumps between odd and even voltage balancing. When the static time of the system is long enough and the battery cell voltage depolarizes and approaches the static voltage, the battery management system (BMS) controls the balance mode to jump to the balance time calculation model.

[0023] Balance time calculation module. The balance time calculation module calculates the balance duration T that each battery cell needs to be turned on. The battery management system (BMS) sets the balance time for the odd-numbered battery cells, and then jumps to the balance time setting for the even-numbered battery cells. After each balance, the remaining balance time of the battery cell is correspondingly subtracted by the set time.

[0024] When the balance time T drops to 0, it jumps to the voltage balance judgment module. If the voltage differences of all battery cells are the same at this time, no balancing is required; if there are still voltage differences, the voltage difference balance of the battery cells is started.

[0025] The specific description of the voltage balance judgment module is as follows: The battery management system (BMS) judges the difference between each battery cell and the lowest single-cell voltage of the system. If the difference ≥ 35 mV, it is considered that this battery cell needs to be balanced; if the difference < 35 mV, this battery cell does not need to be balanced. All the battery cells in the system are polled according to this logic.

[0026] In the balance time calculation module, the balance time T required for each battery cell is calculated by the following formula: T = Q / I, where Q is the current capacity of the battery cell, and I is the balance current; the current capacity Q of the battery cell is calculated by the following formula: Q = SOC * Q0, where SOC is the state of charge of the battery cell, obtained by looking up the table with the open-circuit voltage (OCV) of the single cell after the battery cell is static; Q0 is the rated capacity of the battery cell; the balance current I is calculated by the following formula: I = U / R, where U is the average single-cell voltage and R is the balance resistance.

[0027] The equalization setting time in the equalization time calculation module is 60s.

[0028] A device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the method described in any one of the previous items.

[0029] A computer-readable storage medium stores a computer program. When the computer program is executed by a processor, it implements the steps of the method described in one of the previous items.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] In the equalization control method for energy storage frequency modulation battery cells of the present invention, by calculating the difference between the voltages of all single battery cells and the voltage of the lowest single battery cell in the system and comparing it with a preset voltage difference threshold, the battery cells that need to be equalized can be accurately identified. The comprehensive monitoring and accurate judgment mechanism avoid the problem of the performance degradation of the entire energy storage system caused by the abnormal voltage of individual battery cells, ensure the voltage consistency of the battery cells during charge and discharge, and improve the stability and reliability of the energy storage system.

[0032] Further, when the difference is greater than or equal to the preset threshold, the battery cell is immediately marked as needing equalization. And as the charge and discharge process progresses, the BMS can continuously monitor the voltage change and dynamically update the marking of the battery cells that need to be equalized. This enables the equalization control of the battery cells to adapt to the changes in the state of the battery cells in real time, ensuring the timeliness and effectiveness of the equalization control.

[0033] Sort the battery cells that need to be equalized, and then operate in the way of alternately turning on the equalization for odd-numbered battery cells and even-numbered battery cells. The orderly equalization strategy avoids problems such as excessive current and poor system stability that may be caused by equalizing all battery cells at the same time, reduces the energy loss during the equalization process, and improves the equalization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1 It is a flowchart of the equalization control method for energy storage frequency modulation battery cells of the present invention;

[0036] Figure 2 It is a schematic diagram of the software model of the equalization control system for energy storage frequency modulation battery cells of the present invention. Detailed Implementation Manner

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0039] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0040] The following further describes the present invention in detail with reference to the accompanying drawings:

[0041] See Figure 1 , which is a flowchart of the battery cell equalization control method for energy storage frequency modulation of the present invention, specifically including the following steps:

[0042] In the initial state of the system or during the charge and discharge process, the battery management system BMS calculates the difference between the voltages of all individual battery cells and the voltage of the lowest individual battery cell in the system; when the difference is greater than or equal to a preset voltage difference threshold, the battery cell is marked as needing equalization. When marking the battery cell, the battery management system BMS uses an internal data structure, including an array or a linked list, to allocate a corresponding mark bit for each battery cell. When the battery cell needs equalization, its corresponding mark bit is set to 1; when it does not need equalization, the mark bit is set to 0.

[0043] In the initial state of the system or during the charge and discharge process, the battery management system BMS calculates the difference between the voltages of all individual battery cells and the voltage of the lowest individual battery cell in the system; specifically: The initial state trigger of the system is when the energy storage frequency modulation system starts and after the battery management system BMS completes initialization, the voltage acquisition process is triggered, and the battery management system BMS independently starts monitoring the voltages of the battery cells.

[0044] The battery management system BMS sorts all the battery cells that need equalization, turns on the equalization for the odd-numbered battery cells, and after a preset time for the equalization to be turned on, turns off the equalization for a preset static time; turns on the equalization for the even-numbered battery cells, and repeatedly operates between the odd and even battery cells until there are no battery cells that need the equalization to be turned on.

[0045] During the energy storage frequency modulation stage, after a preset static time, the battery management system BMS looks up the state of charge SOC of each cell according to the open circuit voltage, calculates the capacity difference between each cell and the lowest SOC through the state of charge SOC, and then calculates the equalization time required for each cell to be equalized according to the capacity difference.

[0046] The battery management system BMS calculates the current capacity Q of each cell according to the SOC of the cell, specifically Q = SOC * Q0, where Q0 is the rated capacity of the cell; and calculates the time T required for each cell to be equalized according to the equalization current I, specifically T = Q / I, where I = U / R, U is the average voltage of the single cell, and R is the equalization resistance.

[0047] When the time for each cell to start equalization drops to 0 or the system needs to be static for the preset time again, the BMS exits the capacity equalization state and returns to the voltage equalization state.

[0048] An embodiment of the present invention is a cell equalization control system for energy storage frequency modulation, which specifically includes the following modules:

[0049] Equalization start judgment module. In the initial state of the system or during the charge and discharge process, the battery management system BMS judges the maximum and minimum values of all cells. When the difference between the maximum and minimum values exceeds the set threshold, the equalization of the cells is started.

[0050] Voltage equalization judgment module. The battery management system BMS judges the difference between each cell and the lowest single cell voltage of the system. If the difference exceeds the set threshold, it is considered that the cell needs to be equalized; if the difference does not exceed the set threshold, it does not need to be equalized, and all cells of the system are polled once.

[0051] Odd - even equalization control module. The battery management system BMS polls all the single cell voltages in the system and identifies the cells whose difference from the lowest single cell exceeds the set threshold.

[0052] The battery management system BMS controls to first turn on the odd - numbered cells that need to be equalized. After the equalization is turned on for the set time, then turn on the even - numbered cells that need to be equalized.

[0053] Thereafter, it jumps between odd and even voltage equalizations. When the static time of the system is sufficient, the cell voltage depolarizes and approaches the static voltage, and the battery management system BMS controls the equalization mode to jump to the equalization time calculation model.

[0054] Equalization time calculation module. The equalization time calculation module calculates the equalization duration T that each cell needs to be turned on; the battery management system BMS sets the equalization time for the odd - numbered cells, and then jumps to the equalization time setting for the even - numbered cells. After each equalization, the remaining equalization time of the cell is correspondingly subtracted by the set time.

[0055] In the balancing time calculation module, the time T required for balancing each battery cell is calculated by the following formula: T=Q / I, where Q is the current capacity of the battery cell and I is the balancing current; the current capacity Q of the battery cell is calculated by the following formula: Q=SOC*Q0, where SOC is the state of charge of the battery cell, which is obtained by looking up the cell voltage OCV after the battery cell is left at rest; Q0 is the rated capacity of the battery cell; the balancing current I is calculated by the following formula: I=U / R, where U is the average cell voltage and R is the balancing resistance.

[0056] When the balancing time T drops to 0, the module jumps to the voltage balancing judgment module. If the voltage difference of all cells is consistent at this time, balancing is not required. If there is still a voltage difference, the cell voltage difference balancing is turned on.

[0057] Example

[0058] On the basis of the original voltage balancing, the present invention introduces a capacity balancing control method. This control method is different from the traditional balancing method. The voltage balancing uses the difference between the single cell voltage of the system and the lowest single cell voltage of the system as a judgment condition. When the difference exceeds a certain interval, the BMS turns on the balancing. When the difference between the battery cell and the lowest single cell voltage is less than a certain interval, the balancing is turned off. This balancing control method is simple in design and can meet most application scenarios, but there are still some problems in the field of frequency modulation. First of all, we must understand the characteristics of energy storage frequency regulation: the system operating conditions are not fixed, the system operating current is short, the static time is short or not fixed, and there is no predictability. Therefore, if the above-mentioned voltage-based balancing control mode is used, it cannot meet the frequency modulation field or cannot maximize the characteristics in the leveling field. Therefore, the present invention proposes a new balancing control method for use in the field of energy storage frequency regulation. The following is a specific method description of the balancing control method:

[0059] 1. When the battery management system BMS is in the initial state of the system, the battery management system BMS should calculate whether the difference between the voltage of all cells in the system and the voltage of the lowest cell point in the system is ≥35mV.

[0060] 2. If the difference is ≥35mV, the cell is considered to need balancing and the cell is marked as 1.

[0061] 3. After completing the calculation of all cells, the BMS should sort all cells that need to be balanced. Adhering to the principle that adjacent cells cannot be balanced at the same time, the balancing can be turned on for the odd-numbered cells first. After the balancing is turned on for 1 minute, the balancing is turned off for 30 seconds, and then the balancing is turned on for the even-numbered cells. After no static conditions are met, the operation is repeated between the odd and even cells until there are no cells that need to be balanced.

[0062] 4. The system initial conditions and voltage balance are performed first during the charging and discharging process.

[0063] 5. If, during the energy storage frequency modulation stage, the system is static for 30 minutes, the BMS shall obtain the SOC of each cell by looking up the table based on the OCV, calculate the capacity difference between each cell and the lowest SOC through the SOC, and calculate the equalization time T required for each cell to be equalized based on the capacity difference.

[0064] 6. When the equalization time T required for each cell to be turned on is 0 or the condition for re-staging for 30 minutes is met, the BMS will jump out of the capacity equalization state and return to the voltage equalization state.

[0065] 7. Such a design can always keep the cells in an equalized state, avoiding the system not being equalized under some special working conditions and reducing the equalization efficiency.

[0066] In the above control method, taking the LFP cells as an example for parameters such as the voltage difference threshold and the static time, the relevant parameters of different cell models should be set accordingly.

[0067] See Figure 2 , when entering the equalization module, the BMS will first enter the voltage equalization. The BMS controls the cells that need to be equalized to first turn on the equalization of the odd-numbered cells for 60S, then re-enter the voltage equalization judgment condition. After judgment, it enters the equalization of the even-numbered cell voltages. Thereafter, it jumps between the equalizations of odd and even voltages. When the static time of the system is sufficient, the voltages of the cells have been depolarized at this time, and the voltages at this time approach the static voltage. The BMS will control the equalization mode to jump to the equalization time calculation model, calculate the equalization duration T required for each cell to be turned on, then the BMS turns on the equalization of the odd-numbered cells for 60S, and then jumps to the equalization of the even-numbered cells for 60S. After each equalization, the remaining equalization time of the cell is correspondingly reduced by 60S. When the equalization time T drops to 0, the software jumps to the voltage equalization judgment module. If the voltage differences of all cells are the same at this time, no equalization is required. If there are still differences, the voltage differences of the cells will be equalized.

[0068] The following formula is the formula designed in the capacity equalization module:

[0069] 1. After the cells are static, obtain the SOC of each cell by looking up the table based on the single-cell voltage OCV;

[0070] 2. Obtain the capacity Q of each cell according to the SOC: Q = SOC * Q0

[0071] Among them, Q0 is the rated capacity of the cell, and Q is the current capacity of the cell;

[0072] 3. The equalization time T required for each cell: T = Q / I, I = U / R

[0073] Among them, I is the balancing current, which is equal to the cell voltage divided by the balancing resistance. Since the cell voltage is constantly changing during the charging and discharging process, for the convenience of calculation, the average cell voltage is taken here.

[0074] In order to verify the effectiveness of the control method in the present invention, relevant balancing effect tests were conducted in the laboratory. Scheme 1 is the effect of adopting the voltage balancing control method, and Scheme 2 is the effect of adopting the balancing control method of this patent. It was found through comparison that the balancing control method of the present invention can effectively control the consistency of all battery cells and improve the system capacity.

[0075] Scheme 1

[0076]

[0077] Scheme 2

[0078]

[0079] It can be seen from the above comparison of the balancing effects that adopting the balancing control method in the present invention can more effectively ensure the consistency of the cells compared with the traditional balancing method.

[0080] An embodiment of the present invention provides a terminal device. The terminal device of this embodiment includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps in the above-mentioned various method embodiments are implemented. Alternatively, when the processor executes the computer program, the functions of each module / unit in the above-mentioned various device embodiments are implemented.

[0081] The computer program can be divided into one or more modules / units, and the one or more modules / units are stored in the memory and executed by the processor to complete the present invention.

[0082] The device / terminal device can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The device / terminal device may include, but is not limited to, a processor and a memory.

[0083] The processor may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0084] The memory can be used to store the computer program and / or module. By running or executing the computer program and / or module stored in the memory, and calling the data stored in the memory, the processor implements various functions of the device / terminal equipment.

[0085] If the module / unit integrated in the device / terminal equipment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, to implement all or part of the processes in the above-described embodiment methods of the present invention, it can also be completed by instructing relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-described various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file, or some intermediate form, etc. The computer-readable medium can include: any entity or device that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0086] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for balancing and controlling an energy storage frequency modulation battery cell, characterized in that Including the following steps: During the system initial state or the charge and discharge process, the battery management system BMS calculates the difference between the voltage of each single cell and the lowest single cell voltage in the system; when the difference is greater than or equal to a preset voltage difference threshold, mark this cell as needing to be balanced; The battery management system BMS sorts all the cells that need to be balanced, turns on the balance for the odd-numbered cells, and after the balance is turned on for a preset time, turns off the balance for a preset static time; turns on the balance for the even-numbered cells, and repeatedly operates between the odd and even cells until there are no cells that need to turn on the balance; During the energy storage frequency modulation stage, after a preset static time, the battery management system BMS looks up the state of charge SOC of each cell according to the open circuit voltage, calculates the capacity difference between each cell and the lowest SOC through the state of charge SOC, and then calculates the balance time required for each cell to be balanced according to the capacity difference; When the time required for each cell to turn on the balance drops to 0 or the system needs to be static for a preset time again, the BMS exits the capacity balance state and returns to the voltage balance state.

2. The method for balancing control of energy storage frequency modulation battery cells according to claim 1, wherein, During the system initial state or the charge and discharge process, the battery management system BMS calculates the difference between the voltage of each single cell and the lowest single cell voltage in the system; specifically: the system initial state trigger is when the energy storage frequency modulation system starts, after the battery management system BMS completes initialization, it triggers the voltage acquisition process, and the battery management system BMS independently starts to monitor the cell voltage; The charge and discharge process trigger is when the energy storage system performs a charge or discharge operation, and the battery management system BMS continuously acquires the cell voltage according to a preset sampling period.

3. The method for balancing control of energy storage frequency modulation cells according to claim 1, wherein The battery management system BMS calculates the current capacity Q of each cell according to the SOC of the cell, specifically Q = SOC * Q0, where Q0 is the rated capacity of the cell; and calculates the balance time T required for each cell to be balanced according to the balance current I, specifically T = Q / I, where I = U / R, U is the average single cell voltage, and R is the balance resistor.

4. The equalization control method for energy storage frequency modulation battery cells according to claim 1, characterized in that, When marking the cells, the battery management system BMS uses an internal data structure, including an array or a linked list, assigns a corresponding mark bit to each cell, and when the cell needs to be balanced, sets its corresponding mark bit to 1; when it does not need to be balanced, the mark bit is set to 0.

5. A core balancing control system for energy storage frequency modulation, characterized in that, Including the following modules: Balance start judgment module, during the system initial state or the charge and discharge process, the battery management system BMS judges the maximum and minimum values of all cells, and when the difference between the maximum and minimum values exceeds the set threshold, turns on the balance of the cells; Voltage balance judgment module, the battery management system BMS judges the difference between the voltage of each cell and the lowest single cell voltage in the system. If the difference exceeds the set threshold, it is considered that this cell needs to be balanced; If the difference does not exceed the set threshold, there is no need to balance, and all the cells in the system are polled once; Odd-even balance control module, the battery management system BMS polls all the single cell voltages in the system and identifies the cells whose difference from the lowest single cell exceeds the set threshold; The battery management system BMS controls to first turn on the odd-numbered cells that need to be balanced, and after the balance is turned on for the set time, then turn on the even-numbered cells that need to be balanced; Subsequently, it jumps between odd and even voltage equalizations. When the system's static time is sufficient, the cell voltage depolarizes and approaches the static voltage, and the battery management system (BMS) controls the equalization mode to jump to the equalization time calculation model. Equalization time calculation module: The equalization time calculation module calculates the equalization duration T required for each cell to be turned on. The BMS sets the equalization time for odd cells, and then jumps to the equalization time setting for even cells. After each equalization, the remaining equalization time of the cell is correspondingly reduced by the set time. When the equalization time T drops to 0, it jumps to the voltage equalization judgment module. If the voltage differences of all cells are the same at this time, no equalization is required. If there are still voltage differences, the cell voltage differences are equalized.

6. The equalization control system for energy storage frequency modulation battery cells according to claim 5, wherein, The voltage equalization judgment module is specifically as follows: The BMS judges the difference between each cell and the lowest single-cell voltage of the system. If the difference ≥ 35 mV, it is considered that the cell needs equalization. If the difference < 35 mV, this cell does not need equalization. All cells in the system are polled according to this logic.

7. The equalization control system for energy storage frequency modulation battery cells according to claim 5, characterized in that, In the equalization time calculation module, the equalization time T required for each cell is calculated by the following formula: T = Q / I, where Q is the current capacity of the cell, and I is the equalization current. The current capacity Q of the cell is calculated by the following formula: Q = SOC * Q0, where SOC is the state of charge of the cell, obtained by looking up the table according to the open-circuit voltage (OCV) of the single cell after the cell is static; Q0 is the rated capacity of the cell. The equalization current I is calculated by the following formula: I = U / R, where U is the average single-cell voltage and R is the equalization resistance.

8. The equalization control system for energy storage frequency modulation battery cells according to claim 5, wherein The equalization setting time in the equalization time calculation module is 60 s.

9. An apparatus, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1-4.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method according to any one of claims 1-4.

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