Equalization strategy and system based on SOC extreme value

Abstract

Embodiments of the present invention relate to the technical field of power batteries, and provide an equalization strategy and system based on an SOC extreme value. The equalization strategy comprises: acquiring cell SOC values of a battery pack and an average SOC value; determining whether the battery pack needs to execute an equalization operation; when it is determined that the battery pack needs to execute the equalization operation, determining a cell SOC extreme value and a cell SOC sub-extreme value of the battery pack; and using a midpoint between the average SOC value and the cell SOC sub-extreme value as a target SOC to equalize the battery pack. According to the equalization strategy and system, by predicting the SOC of a battery pack, a cell having the maximum SOC during charging and a cell having the minimum SOC during discharging are equalized in time, thereby ensuring full utilization of the capacity of the battery pack, and achieving equalization of the whole battery pack and high equalization efficiency.

Description

Equilibrium strategy and system based on SOC maximum value

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202410098391.9 filed on January 24, 2024, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of power batteries, and in particular to a balancing strategy and system based on a maximum SOC value. Background Art

[0004] Because battery cells have relatively small capacity and voltage, they need to be gradually expanded through series and parallel connection to form a battery pack. However, due to factors such as inconsistent production processes and ambient temperatures, cell inconsistencies exist, hindering the efficient utilization of the battery pack. During charging, when the cell with the highest SOC is fully charged, the BMS terminates charging regardless of whether other cells are fully charged, otherwise it will damage the battery cell. During discharge, when the cell with the lowest SOC is fully discharged, discharge ends regardless of whether other cells have any remaining charge. This results in underutilization of the battery pack's capacity.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to provide a balancing strategy and system based on the maximum SOC value. The balancing strategy predicts the SOC of the battery pack and promptly balances the cells with the highest SOC during charging and the cells with the lowest SOC during discharging, ensuring full utilization of the battery pack capacity and achieving balancing of the entire battery pack with high balancing efficiency.

[0007] In order to achieve the above objectives, the present invention provides, on one hand, a balancing strategy based on the maximum SOC value, comprising:

[0008] Get the single cell SOC value and average SOC value of the battery pack;

[0009] Determining whether the battery pack needs to perform a balancing operation;

[0010] In the case where it is determined that the battery pack needs to perform a balancing operation, determining a cell SOC extreme value and a cell SOC sub-extreme value of the battery pack;

[0011] The battery pack is balanced using an intermediate value between the average SOC value and the next-highest SOC value of a single cell as a target SOC.

[0012] Optionally, determining a cell SOC extreme value and a cell SOC sub-extreme value of the battery pack includes:

[0013] determining an operating status of the battery pack;

[0014] When the battery pack is in a charging state, the highest cell SOC value and the second highest cell SOC value are determined.

[0015] Optionally, determining a cell SOC extreme value and a cell SOC sub-extreme value of the battery pack includes:

[0016] determining an operating status of the battery pack;

[0017] When the battery pack is in a discharging state, the lowest cell SOC value and the second lowest cell SOC value are determined.

[0018] Optionally, balancing the battery pack with an intermediate value between the average SOC value and the next-highest SOC value of a single cell as a target SOC includes:

[0019] determining a theoretical control amount for balancing the battery pack according to the target SOC;

[0020] Calculate the theoretical SOC after executing the theoretical control amount according to the objective function;

[0021] executing the theoretical control variable and obtaining the actual SOC of the battery pack;

[0022] Determining a single cell SOC of the battery pack according to the theoretical SOC and the actual SOC;

[0023] Determining whether the battery pack meets a balancing condition according to the single cell SOC;

[0024] If it is determined that the battery pack meets the balancing condition, updating the objective function according to the theoretical SOC and the actual SOC, and returning to the step of determining the theoretical control amount for balancing the battery pack according to the target SOC;

[0025] If it is determined that the battery pack does not meet the balancing condition, it is determined that the balancing of the battery pack is completed.

[0026] Optionally, the balancing strategy includes:

[0027] Formula (1) is used to determine the objective function:

[0028] Among them, minJ is the minimization of the objective function, U(k) T is the transpose of the battery pack balance state matrix, is the internal resistance matrix, U(k) is the battery pack equilibrium state matrix, α, β, η, is the intermediate variable matrix.

[0029] Optionally, obtaining the actual SOC of the battery pack includes:

[0030] collecting the cell terminal voltage of the battery pack;

[0031] The actual SOC is determined according to a preset battery model.

[0032] Optionally, the balancing strategy further includes:

[0033] The actual SOC is determined according to formula (2): U = E0 - I c R in +k1lnSOC+k2ln(1-SOC), (2)

[0034] Among them, U is the single terminal voltage, E0 is the open circuit voltage, I c is the discharge current, R in is the internal resistance of the battery, k1 and k2 are fitting coefficients.

[0035] Optionally, determining the single cell SOC of the battery pack according to the theoretical SOC and the actual SOC includes:

[0036] The monomer SOC is determined according to formula (3): SOC0 = SOC1 + SOC2 / 2, (3)

[0037] Among them, SOC1 is the theoretical SOC, SOC2 is the actual SOC, and SOC0 is the single-cell SOC.

[0038] On the other hand, the present invention further provides a balancing system based on a maximum SOC value, wherein the balancing system includes a processor configured to execute any of the above-mentioned balancing strategies.

[0039] Through the above technical solution, the present invention provides a balancing strategy and system based on SOC maximum values. By obtaining the individual SOC values ​​and average SOC values ​​of a battery pack, when the battery pack needs to perform a balancing operation, the battery pack's individual SOC extreme value and individual SOC sub-extreme value are determined. The battery pack is then balanced using the intermediate value between the average SOC value and the individual SOC sub-extreme value as the target SOC. This balancing strategy and system predicts the battery pack SOC and promptly balances the cells with the highest SOC during charging and the cells with the lowest SOC during discharging, ensuring full utilization of the battery pack capacity and achieving balancing of the entire battery pack with high balancing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG1 is a flow chart of a balancing strategy based on a maximum SOC value according to an embodiment of the present invention;

[0041] 2 is a flow chart of determining a cell SOC extreme value and a cell SOC sub-extreme value of a battery pack according to one embodiment of the present invention;

[0042] 3 is a flow chart of determining a cell SOC extreme value and a cell SOC sub-extreme value of a battery pack according to one embodiment of the present invention;

[0043] FIG4 is a flow chart of balancing a battery pack according to one embodiment of the present invention;

[0044] FIG5 is a flow chart of obtaining the actual SOC of a battery pack according to one embodiment of the present invention. DETAILED DESCRIPTION

[0045] The following describes the specific implementation of the embodiment of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the embodiment of the present invention and is not used to limit the embodiment of the present invention.

[0046] FIG1 is a flow chart of a balancing strategy based on SOC maximum value according to an embodiment of the present invention. In FIG1 , the balancing strategy may include:

[0047] In step S1, the single cell SOC value and the average SOC value of the battery pack are obtained;

[0048] In step S2, it is determined whether the battery pack needs to perform a balancing operation;

[0049] In step S3, when it is determined that the battery pack needs to perform a balancing operation, the cell SOC extreme value and the cell SOC sub-extreme value of the battery pack are determined;

[0050] In step S4 , the battery pack is balanced using the target SOC as the intermediate value between the average SOC value and the next-highest SOC value of the cell.

[0051] In the method shown in Figure 1, step S1 is used to obtain the cell SOC value and the average SOC value of the battery pack. The specific methods for obtaining the cell SOC value can be various, known to those skilled in the art. For example, it can be obtained using the ampere-hour integration method or the open-circuit voltage-SOC curve. As for obtaining the average SOC value, the average SOC value can be further calculated based on the cell SOC values.

[0052] Step S2 can be used to determine whether the battery pack requires balancing. The specific methods for determining whether to perform balancing can be various methods known to those skilled in the art. In one embodiment of the present invention, the determination can be made by comparing the difference between the maximum and minimum SOC values ​​with a preset value. If the difference is greater than the preset value, it indicates that the difference in the cell SOC values ​​within the battery pack is too large, and balancing is performed. Otherwise, balancing is not performed.

[0053] In step S3, the cell SOC extreme value and the cell SOC sub-extreme value may be, for example, the cell SOC maximum value and the cell SOC sub-maximum value. In this case, when the cell SOC extreme value and the cell SOC sub-extreme value are the cell SOC maximum value and the cell SOC sub-maximum value, respectively, step S3 may include the method shown in FIG2 . In FIG2 , step S3 may further include the following steps:

[0054] In step S10, the operating state of the battery pack is determined;

[0055] In step S11 , when the battery pack is in a charging state, a highest cell SOC value and a second highest cell SOC value are determined.

[0056] In step S3, the cell SOC extreme value and the cell SOC sub-extreme value may also be, for example, the cell SOC minimum value and the cell SOC sub-lowest value. Then, when the cell SOC extreme value and the cell SOC sub-extreme value are the cell SOC minimum value and the cell SOC sub-lowest value, respectively, step S3 may include the method shown in FIG3 . In FIG3 , step S3 may further include the following steps:

[0057] In step S20, the operating state of the battery pack is determined;

[0058] In step S21 , when the battery pack is in a discharging state, the lowest cell SOC value and the second lowest cell SOC value are determined.

[0059] In the case where it is determined that the balancing operation needs to be turned on, steps S3 and S4 can be executed to perform balancing. In the prior art, the commonly used balancing strategy is mainly to directly perform balancing by comparing the difference between the maximum and minimum SOC values ​​or voltage values ​​of the single cells in the battery pack, and the target of balancing is generally the average value. This approach will have the technical problem of over-balancing, thereby affecting the balancing efficiency. Therefore, in steps S3 and S4 provided by the present invention, first, the single cell SOC value and the single cell SOC sub-extreme value are determined, and then, in combination with step S4, balancing is performed by taking the middle value between the average SOC value and the single cell SOC sub-extreme value as the target SOC. Since the target SOC used in steps S3 and S4 is the middle value between the average SOC value and the single cell SOC sub-extreme value, compared with the prior art, the middle value is closer to the average value, and therefore can overcome the technical problem of over-balancing in the prior art.

[0060] Step S4 uses the middle value between the average SOC value and the sub-maximal SOC value of the cell as the target SOC to balance the battery pack. Generally speaking, the sub-maximal (or sub-maximal) value of the cell SOC is higher (or lower) than the average SOC value, and it is not necessary to balance the cell SOC extreme value towards the average SOC value. As long as the cell SOC extreme value is closer to the average SOC value than the sub-maximal SOC value of the cell SOC, the state in which the battery pack capacity cannot be fully utilized will be improved, and the technical problem of over-balancing can be alleviated. The method for balancing the battery pack may include the steps shown in Figure 4. Specifically:

[0061] In step S30 , a theoretical control amount for balancing the battery pack is determined according to the target SOC;

[0062] In step S31, the theoretical SOC after executing the theoretical control amount is calculated according to the objective function;

[0063] In step S32, the theoretical control amount is executed and the actual SOC of the battery pack is obtained;

[0064] In step S33, the cell SOC of the battery pack is determined based on the theoretical SOC and the actual SOC;

[0065] In step S34, it is determined whether the battery pack meets the balancing condition based on the cell SOC;

[0066] In step S35, if it is determined that the battery pack meets the balancing condition, the objective function is updated according to the theoretical SOC and the actual SOC, and the process returns to the step of determining the theoretical control amount for balancing the battery pack according to the target SOC, i.e., returning to step S30.

[0067] In step S36 , when it is determined that the battery pack does not meet the balancing condition, it is determined that the balancing of the battery pack is completed.

[0068] In the method shown in Figure 4, step S30 can be used to determine the theoretical control amount for balancing the battery pack based on the target SOC, thereby determining the switching control operation to be performed by the battery pack in the next step. However, due to the relatively limited accuracy of the battery pack's SOC estimation, it is impossible to directly determine the battery pack's actual SOC by estimating the battery pack's SOC after executing the theoretical control amount. Therefore, in this balancing strategy, step S31 can first calculate the theoretical SOC after executing the theoretical control amount in combination with a preset objective function, then step S32 can directly estimate the actual SOC of the battery pack after executing the theoretical control amount, and finally step S33 can combine the theoretical SOC and the actual SOC to obtain the actual SOC, i.e., the cell SOC.

[0069] In addition, the objective function in step S31 can be in various forms known to those skilled in the art. In one example of the present invention, the objective function can be determined using the following formula (1):

[0070] Among them, minJ is the minimization of the objective function, U(k) T is the transpose of the battery pack balance state matrix, is the internal resistance matrix, U(k) is the battery pack equilibrium state matrix, α, β, η, is the intermediate variable matrix.

[0071] The method for determining the actual SOC of the battery pack in step S32 may be any of various methods known to those skilled in the art, including but not limited to the ampere-hour integration method, the curve fitting method, etc. In one example of the present invention, the method for determining the actual SOC may include the steps shown in FIG5 . In FIG5 , the method for determining the actual SOC may include the following steps:

[0072] In step S40, the cell terminal voltage of the battery pack is collected;

[0073] In step S41 , the actual SOC is determined according to a preset battery model.

[0074] The battery model in step S41 may be in various forms known to those skilled in the art. In this example, the battery model may be as shown in the following formula (2): U = E0 - I c R in +k1lnSOC+k2ln(1-SOC), (2)

[0075] Among them, U is the single terminal voltage, E0 is the open circuit voltage, I c is the discharge current, R in is the internal resistance of the battery, k1 and k2 are fitting coefficients.

[0076] In step S33, the specific method for obtaining the single cell SOC by using the theoretical SOC and the actual SOC may be various methods known to those skilled in the art. In one embodiment of the present invention, the single cell SOC may be determined using formula (3): SOC0 = SOC1 + SOC2 / 2, (3)

[0077] Among them, SOC1 is the theoretical SOC, SOC2 is the actual SOC, and SOC0 is the single-cell SOC.

[0078] After determining the cell SOC, which represents the actual SOC of the individual cells, the battery pack can be judged based on the cell SOC to determine whether it meets the balancing condition (step S34). If the battery pack still meets the balancing condition, it indicates that the battery pack needs to continue to perform switching control to escape the balancing condition, so the process returns to step S30. Otherwise, the process exits (step S36).

[0079] On the other hand, the present invention also provides a balancing system based on SOC maximum value, the balancing system including a processor configured to execute any of the above-mentioned balancing strategies. Specifically, the balancing strategy may be the steps shown in Figures 1 to 5. In Figure 1, the balancing strategy may include:

[0080] In step S1, the single cell SOC value and the average SOC value of the battery pack are obtained;

[0081] In step S2, it is determined whether the battery pack needs to perform a balancing operation;

[0082] In step S3, when it is determined that the battery pack needs to perform a balancing operation, the cell SOC extreme value and the cell SOC sub-extreme value of the battery pack are determined;

[0083] In step S4 , the battery pack is balanced using the target SOC as the intermediate value between the average SOC value and the next-highest SOC value of the cell.

[0084] In the method shown in Figure 1, step S1 is used to obtain the cell SOC value and the average SOC value of the battery pack. The specific methods for obtaining the cell SOC value can be various, known to those skilled in the art. For example, it can be obtained using the ampere-hour integration method or the open-circuit voltage-SOC curve. As for obtaining the average SOC value, the average SOC value can be further calculated based on the cell SOC values.

[0085] Step S2 can be used to determine whether the battery pack requires balancing. The specific methods for determining whether to perform balancing can be various methods known to those skilled in the art. In one embodiment of the present invention, the determination can be made by comparing the difference between the maximum and minimum SOC values ​​with a preset value. If the difference is greater than the preset value, it indicates that the difference in the cell SOC values ​​within the battery pack is too large, and balancing is performed. Otherwise, balancing is not performed.

[0086] In step S3, the cell SOC extreme value and the cell SOC sub-extreme value may be, for example, the cell SOC maximum value and the cell SOC sub-maximum value. In this case, when the cell SOC extreme value and the cell SOC sub-extreme value are the cell SOC maximum value and the cell SOC sub-maximum value, respectively, step S3 may include the method shown in FIG2 . In FIG2 , step S3 may further include the following steps:

[0087] In step S10, the operating state of the battery pack is determined;

[0088] In step S11 , when the battery pack is in a charging state, a highest cell SOC value and a second highest cell SOC value are determined.

[0089] In step S3, the cell SOC extreme value and the cell SOC sub-extreme value may also be, for example, the cell SOC minimum value and the cell SOC sub-lowest value. Then, when the cell SOC extreme value and the cell SOC sub-extreme value are the cell SOC minimum value and the cell SOC sub-lowest value, respectively, step S3 may include the method shown in FIG3 . In FIG3 , step S3 may further include the following steps:

[0090] In step S20, the operating state of the battery pack is determined;

[0091] In step S21 , when the battery pack is in a discharging state, the lowest cell SOC value and the second lowest cell SOC value are determined.

[0092] In the case where it is determined that the balancing operation needs to be turned on, steps S3 and S4 can be executed to perform balancing. In the prior art, the commonly used balancing strategy is mainly to directly perform balancing by comparing the difference between the maximum and minimum SOC values ​​or voltage values ​​of the single cells in the battery pack, and the target of balancing is generally the average value. This approach will have the technical problem of over-balancing, thereby affecting the balancing efficiency. Therefore, in steps S3 and S4 provided by the present invention, first, the single cell SOC value and the single cell SOC sub-extreme value are determined, and then, in combination with step S4, balancing is performed by taking the middle value between the average SOC value and the single cell SOC sub-extreme value as the target SOC. Since the target SOC used in steps S3 and S4 is the middle value between the average SOC value and the single cell SOC sub-extreme value, compared with the prior art, the middle value is closer to the average value, and therefore can overcome the technical problem of over-balancing in the prior art.

[0093] Step S4 uses the middle value between the average SOC value and the sub-maximal SOC value of the cell as the target SOC to balance the battery pack. Generally speaking, the sub-maximal (or sub-maximal) value of the cell SOC is higher (or lower) than the average SOC value, and it is not necessary to balance the cell SOC extreme value towards the average SOC value. As long as the cell SOC extreme value is closer to the average SOC value than the sub-maximal SOC value of the cell SOC, the state in which the battery pack capacity cannot be fully utilized will be improved, and the technical problem of over-balancing can be alleviated. The method for balancing the battery pack may include the steps shown in Figure 4. Specifically:

[0094] In step S30 , a theoretical control amount for balancing the battery pack is determined according to the target SOC;

[0095] In step S31, the theoretical SOC after executing the theoretical control amount is calculated according to the objective function;

[0096] In step S32, the theoretical control amount is executed and the actual SOC of the battery pack is obtained;

[0097] In step S33, the cell SOC of the battery pack is determined based on the theoretical SOC and the actual SOC;

[0098] In step S34, it is determined whether the battery pack meets the balancing condition based on the cell SOC;

[0099] In step S35, if it is determined that the battery pack meets the balancing condition, the objective function is updated according to the theoretical SOC and the actual SOC, and the process returns to the step of determining the theoretical control amount for balancing the battery pack according to the target SOC, i.e., returning to step S30.

[0100] In step S36 , when it is determined that the battery pack does not meet the balancing condition, it is determined that the balancing of the battery pack is completed.

[0101] In the method shown in Figure 4, step S30 can be used to determine the theoretical control amount for balancing the battery pack based on the target SOC, thereby determining the switching control operation to be performed by the battery pack in the next step. However, due to the relatively limited accuracy of the battery pack's SOC estimation, it is impossible to directly determine the battery pack's actual SOC by estimating the battery pack's SOC after executing the theoretical control amount. Therefore, in this balancing strategy, step S31 can first calculate the theoretical SOC after executing the theoretical control amount in combination with a preset objective function, then step S32 can directly estimate the actual SOC of the battery pack after executing the theoretical control amount, and finally step S33 can combine the theoretical SOC and the actual SOC to obtain the actual SOC, i.e., the cell SOC.

[0102] In addition, the objective function in step S31 can be in various forms known to those skilled in the art. In one example of the present invention, the objective function can be determined using the following formula (1):

[0103] Among them, minJ is the minimization of the objective function, U(k) T is the transpose of the battery pack balancing state matrix, is the internal resistance matrix, U(k) is the battery pack equilibrium state matrix, α, β, η, is the intermediate variable matrix.

[0104] The method for determining the actual SOC of the battery pack in step S32 may be any of various methods known to those skilled in the art, including but not limited to the ampere-hour integration method, the curve fitting method, etc. In one example of the present invention, the method for determining the actual SOC may include the steps shown in FIG5 . In FIG5 , the method for determining the actual SOC may include the following steps:

[0105] In step S40, the cell terminal voltage of the battery pack is collected;

[0106] In step S41 , the actual SOC is determined according to a preset battery model.

[0107] The battery model in step S41 may be in various forms known to those skilled in the art. In this example, the battery model may be as shown in the following formula (2): U = E0 - I c R in +k1lnSOC+k2ln(1-SOC), (2)

[0108] Among them, U is the single terminal voltage, E0 is the open circuit voltage, I c is the discharge current, R in is the internal resistance of the battery, k1 and k2 are fitting coefficients.

[0109] In step S33, the specific method for obtaining the single cell SOC by using the theoretical SOC and the actual SOC may be various methods known to those skilled in the art. In one embodiment of the present invention, the single cell SOC may be determined using formula (3): SOC0 = SOC1 + SOC2 / 2, (3)

[0110] Among them, SOC1 is the theoretical SOC, SOC2 is the actual SOC, and SOC0 is the single-cell SOC.

[0111] After determining the cell SOC, which represents the actual SOC of the individual cells, the battery pack can be judged based on the cell SOC to determine whether it meets the balancing condition (step S34). If the battery pack still meets the balancing condition, it indicates that the battery pack needs to continue to perform switching control to escape the balancing condition, so the process returns to step S30. Otherwise, the process exits (step S36).

[0112] Through the above technical solution, the present invention provides a balancing strategy and system based on SOC maximum values. By obtaining the individual SOC values ​​and average SOC values ​​of a battery pack, when the battery pack needs to perform a balancing operation, the battery pack's individual SOC extreme value and individual SOC sub-extreme value are determined. The battery pack is then balanced using the intermediate value between the average SOC value and the individual SOC sub-extreme value as the target SOC. This balancing strategy and system predicts the battery pack SOC and promptly balances the cells with the highest SOC during charging and the cells with the lowest SOC during discharging, ensuring full utilization of the battery pack capacity and achieving balancing of the entire battery pack with high balancing efficiency.

[0113] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0114] The present application is described with reference to the flow chart and / or block diagram of the method, device (system), and computer program product according to the embodiment of the present application. It should be understood that each flow process and / or box in the flow chart and / or block diagram and the combination of the flow process and / or box in the flow chart and / or block diagram can be realized by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processing machine or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for realizing the function specified in one flow chart flow or multiple flows and / or one box or multiple boxes of the block diagram.

[0115] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0116] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0117] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0118] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0119] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0120] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0121] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. An equalization strategy based on the maximum and minimum values of SOC, characterized in that, The equalization strategy includes: Obtaining the individual SOC values and the average SOC value of the battery pack; Determining whether the battery pack needs to perform an equalization operation; When it is determined that the battery pack needs to perform an equalization operation, determining the extreme value and the second extreme value of the individual SOC of the battery pack; Using the intermediate value between the average SOC value and the second extreme value of the individual SOC as the target SOC to equalize the battery pack.

2. The equalization strategy according to claim 1, wherein Determining the extreme value and the second extreme value of the individual SOC of the battery pack includes: Determining the working state of the battery pack; When the battery pack is in a charging state, determining the highest value and the second highest value of the individual SOC.

3. The equalization strategy according to claim 1, wherein Determining the extreme value and the second extreme value of the individual SOC of the battery pack includes: Determining the working state of the battery pack; When the battery pack is in a discharging state, determining the lowest value and the second lowest value of the individual SOC.

4. The equalization strategy according to claim 1, wherein Using the intermediate value between the average SOC value and the second extreme value of the individual SOC as the target SOC to equalize the battery pack includes: Determining the theoretical control quantity for equalizing the battery pack according to the target SOC; Calculating the theoretical SOC after executing the theoretical control quantity according to the objective function; Executing the theoretical control quantity and obtaining the actual SOC of the battery pack; Determining the individual SOC of the battery pack according to the theoretical SOC and the actual SOC; Judging whether the battery pack meets the equalization condition according to the individual SOC; When it is determined that the battery pack meets the equalization condition, updating the objective function according to the theoretical SOC and the actual SOC, and returning to the step of determining the theoretical control quantity for equalizing the battery pack according to the target SOC; When it is determined that the battery pack does not meet the equalization condition, determining that the equalization of the battery pack is completed.

5. The equalization strategy according to claim 4, wherein The equalization strategy includes: The objective function is determined by using formula (1). where minJ is the minimization of the objective function, and U(k) T is the transpose of the battery pack balancing state matrix, is the internal resistance matrix, U(k) is the battery pack balancing state matrix, α, β, η, Is the intermediate variable matrix.

6. The equalization strategy according to claim 5, characterized in that, Obtaining the actual SOC of the battery pack includes: Collecting the individual terminal voltages of the battery pack; Determining the actual SOC according to a preset battery model.

7. The equalization strategy according to claim 6, wherein The equalization strategy further includes: Determining the actual SOC according to formula (2), U = E0 - I c R in + k1lnSOC + k2ln(1 - SOC), (2) Among them, U is the monomer terminal voltage, E0 is the open-circuit voltage, I c is the discharge current, R in is the battery internal resistance, and k1 and k2 are fitting coefficients.

8. The equalization strategy according to claim 7, wherein Determining the individual SOC of the battery pack according to the theoretical SOC and the actual SOC includes: Determining the individual SOC according to formula (3), SOC0 = SOC1 + SOC2 / 2, (3) Wherein, SOC1 is the theoretical SOC, SOC2 is the actual SOC, and SOC0 is the individual SOC.

9. An equalization system based on the maximum and minimum values of the SOC, characterized in that, The equalization system includes a processor, and the processor is configured to execute the equalization strategy according to any one of claims 1 to 8.

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