Balancing method for an energy storage system, energy storage system

Abstract

The application relates to a balancing method of an energy storage system and the energy storage system. Before performing an active balancing action in a first balancing mode, a plurality of battery cells are evaluated based on current operation state information of the plurality of battery cells, battery cells satisfying thermal reliability conditions and balancing participation conditions are screened, and a candidate battery cell set is constructed. According to the health state and the balancing available amount of the candidate battery cells in the candidate battery cell set, the attenuation deviation of the candidate battery cells is calculated, at least one pair of balancing battery cells is determined according to the sequence of the attenuation deviation, and the donor battery cell in the balancing battery cell pair performs an active balancing action on the receptor battery cell. The active balancing action is rotated among the battery cells, and the individual battery cells are prevented from accelerating degradation due to frequent participation in balancing. The active balancing action is preferentially performed between battery cells with large attenuation deviation difference, the aging difference among the battery cells is gradually reduced, and the aging of the plurality of battery cells in the energy storage system tends to be consistent.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to an energy storage system balancing method and an energy storage system. Background Technology

[0002] Due to variations in manufacturing processes, operating temperature gradients, and charge / discharge cycle counts, the capacity, internal resistance, and self-discharge rate of battery cells in energy storage systems inevitably become inconsistent. This leads to differences in cell performance within the energy storage system, and the usable capacity of the entire battery pack is limited by the worst-performing cell. Furthermore, weaker cells are more prone to overcharging or over-discharging, further accelerating aging and creating a vicious cycle.

[0003] Active balancing technology uses power conversion circuits to transfer energy from cells with a higher state of charge (SOC) to cells with a lower SOC. Compared with passive balancing (which dissipates excess energy through resistors), it has advantages such as high energy utilization, fast balancing speed, and low heat generation.

[0004] However, existing active equilibrium control strategies still have many shortcomings. Summary of the Invention

[0005] Therefore, it is necessary to provide an energy storage system balancing method and an energy storage system to address the above-mentioned technical problems.

[0006] In a first aspect, this application provides a method for balancing an energy storage system, the energy storage system comprising multiple battery cells; the method includes:

[0007] Collect the current operating status information of the multiple battery cells;

[0008] Based on the current operating status information of the multiple battery cells, when the energy storage system meets the first trigger condition, it enters the first equalization mode;

[0009] Based on the current operating status information of the multiple battery cells, the multiple battery cells are evaluated, and battery cells that meet the thermal reliability conditions and equalization participation conditions are selected to construct a candidate battery cell set;

[0010] Based on the health status and available balance of the candidate cells in the candidate cell set, the attenuation deviation of the candidate cells is calculated. At least one pair of equalizing cells is determined according to the order of the attenuation deviation, and the donor cell in the at least one pair of equalizing cells is controlled to perform an active equalization action to the recipient cell.

[0011] In one embodiment, the current operating status information of the battery cell includes state of charge and health status; the evaluation of the multiple battery cells based on their current operating status information, and the selection of cells that meet thermal reliability and equalization participation conditions to construct a candidate battery cell set, includes:

[0012] Based on the current operating status information of the multiple battery cells and the preset balancing current, the predicted temperature of the multiple battery cells after balancing is determined, and based on the historical balancing participation data of the multiple battery cells, the current available balancing quota of the multiple battery cells is determined.

[0013] The candidate cell set is constructed by using cells whose predicted temperature is lower than a preset safe temperature threshold and whose available balance is higher than the balance participation benchmark value.

[0014] The equilibrium participation benchmark value is the participation consumption value for performing the current equilibrium action.

[0015] In one embodiment, the current operating status information of the battery cell further includes the surface temperature of the battery cell; the evaluation of the plurality of battery cells to select those that meet the thermal reliability and equalization participation conditions includes:

[0016] Based on the surface temperature of the multiple battery cells, the ambient operating temperature, and the preset balancing current, the predicted temperature of the multiple battery cells after performing active balancing is calculated using a thermal reliability model.

[0017] A battery cell whose predicted temperature is lower than the preset safe temperature threshold is determined to meet the thermal reliability condition.

[0018] In one embodiment, the thermal reliability model calculates the temperature rise decay of the battery cell during the equalization period based on the surface temperature of the battery cell, the ambient operating temperature, the preset equalization time, and the thermal time constant.

[0019] Based on the preset equalization current, the DC internal resistance and equivalent thermal resistance of the battery cell, the cumulative temperature rise of the battery cell during the equalization period is calculated.

[0020] The predicted temperature is obtained by superimposing the ambient temperature, the temperature rise attenuation, and the temperature rise accumulation.

[0021] In one embodiment, the thermal reliability model is as follows:

[0022] ;

[0023] Among them, T end T is the predicted temperature of the battery cell. curr T is the surface temperature of the battery cell.amb Operating ambient temperature; I bal Preset equalization current; R in R is the DC internal resistance of the battery cell; th τ is the equivalent thermal resistance of the battery cell to the environment; τ is the thermal time constant; Δt is the preset equalization time.

[0024] In one embodiment, the evaluation of the plurality of battery cells to select those that meet the thermal reliability and equalization participation conditions includes:

[0025] Based on the balanced available amount of the multiple battery cells, predict the participation consumption value after the multiple battery cells perform the active balancing action;

[0026] The balanced available amount of the multiple battery cells is compared with the participation consumption value. The battery cells whose balanced available amount is greater than or equal to the participation consumption value are determined to meet the balanced participation condition.

[0027] In one embodiment, the candidate battery cells include basic candidate battery cells and restricted candidate battery cells; the balanced available quota includes a disabled interval, a restricted interval, and an available interval;

[0028] The battery cells whose balanced available quota is within the available range are included as the basic candidate battery cells in the candidate battery cell set;

[0029] The battery cells whose balanced available quota is within the restricted usage range are included in the candidate battery cell set as the restricted usage candidate battery cells;

[0030] Cells whose balanced available quota is in the disabled range are excluded from the candidate cell set;

[0031] The method further includes: if the restricted candidate cell participates in the active balancing action, setting the balancing current of the restricted candidate cell to be less than the balancing current of the basic candidate cell.

[0032] In one embodiment, calculating the attenuation deviation of the candidate cells based on the health status and balanced available capacity of the candidate cells in the candidate cell set includes:

[0033] Calculate the average health status of the candidate battery cell set based on the health status of at least one candidate battery cell in the candidate battery cell set;

[0034] Based on the average health status, the health status and balanced available quota of the candidate cells, the attenuation deviation of the candidate cells is calculated using the balanced tendency function.

[0035] The attenuation deviation is used to characterize the priority of the candidate cell as the donor cell or the recipient cell, so that the health status difference between the multiple cells is reduced as the active balancing action is performed.

[0036] In one embodiment, the equalization tendency function determines the attenuation deviation of the candidate cell based on the degree of deviation of the health status of the candidate cell from the mean of the health status and the remaining proportion of the equalization available quota of the candidate cell relative to the total quota capacity.

[0037] In one embodiment, the equilibrium tendency function is as follows:

[0038] ;

[0039] in, i represents the attenuation deviation of the candidate cell; SOHi represents the health status of the cell; SOH avg Ci represents the average health status of the candidate cell set; Ci is the balanced available capacity of the cells; C max To balance the total available credit capacity; α is the aging weight; β is the weight for balancing available credit.

[0040] In one embodiment, the available balance quota includes a first available balance quota and a second available balance quota. The first available balance quota characterizes the degree of balance participation of the battery cell as the donor battery cell, and the second available balance quota characterizes the degree of balance participation of the battery cell as the recipient battery cell. The step of evaluating the plurality of battery cells and selecting those that meet the thermal reliability and balance participation conditions includes:

[0041] The first and second balanced available quotas of the plurality of battery cells are obtained respectively;

[0042] The multiple battery cells are screened based on the first equalization available quota of the multiple battery cells, and the battery cells that meet the first output equalization condition are included in the first output candidate set;

[0043] The multiple battery cells are screened according to the second equalization available quota of the multiple battery cells, and the battery cells that meet the first receiving equalization condition are included in the first receiving candidate set;

[0044] The candidate cell set is determined based on the first output candidate set and the first received candidate set.

[0045] In one embodiment, determining at least one pair of equalizing cells based on the order of the attenuation deviation, and controlling the donor cell in the at least one pair of equalizing cells to perform an active equalization action on the recipient cell, includes:

[0046] The candidate cell with the largest attenuation deviation in the candidate cell set is used as the donor cell, and the candidate cell with the smallest attenuation deviation is used as the recipient cell, to form at least one pair of balanced cells.

[0047] In one embodiment, determining at least one pair of equalizing cells based on the ranking of the attenuation deviation, and evaluating the plurality of cells to select cells that meet the thermal reliability and equalization participation conditions, includes:

[0048] An output candidate sequence is generated by sorting the attenuation deviations from largest to smallest, and a receiving candidate sequence is generated by sorting the attenuation deviations from smallest to largest.

[0049] Based on parallel constraints, the output candidate sequence is paired with the candidate cells in the received candidate sequence that have the same sorting position and whose attenuation deviation difference is greater than or equal to a preset threshold, to form at least one pair of balanced cells.

[0050] In one embodiment, the parallel constraint includes parallel balancing capacity; the parallel balancing capacity is determined based on the available balancing resources of the energy storage system and the number of candidate cells in the candidate cell set;

[0051] When the output candidate sequence is paired with the received candidate sequence, an upper limit for the number of pairs is set according to the parallel equalization capacity; the upper limit for the number of pairs is not greater than the parallel equalization capacity.

[0052] In one embodiment, the method further includes:

[0053] The charge dispersion of the multiple cells is calculated based on their state of charge, and the aging dispersion of the multiple cells is calculated based on their health status.

[0054] When the charge dispersion is less than or equal to a first preset threshold and the aging dispersion is greater than a second preset threshold, the energy storage system is determined to meet the first triggering condition.

[0055] In one embodiment, the method further includes:

[0056] When the charge dispersion is greater than the first preset threshold, the system enters the second equalization mode to equalize the charge states of the multiple cells.

[0057] In one embodiment, in the second balancing mode, balancing is performed based on the state of charge of the plurality of cells, including:

[0058] A reference state of charge is calculated based on the state of charge of the multiple battery cells.

[0059] The state of charge (SOC) of the plurality of cells is compared with the reference SOC to obtain the SOC deviation of the plurality of cells.

[0060] Based on the state of charge deviation of the multiple battery cells, a second set of output candidate battery cells and a second set of receiving candidate battery cells are constructed respectively.

[0061] The cells in the second output candidate cell set are paired with the cells in the second receiving candidate cell set, and the paired cells are controlled to perform equalization operations.

[0062] Secondly, this application provides an energy storage system, the energy storage system comprising multiple battery cells; the energy storage system further comprises:

[0063] The data acquisition module is used to collect the current operating status information of the multiple battery cells;

[0064] The arbitration module is used to determine, based on the current operating status information of the multiple battery cells, when the energy storage system meets the first trigger condition, to enter the first equalization mode;

[0065] The first screening module is used to evaluate the multiple battery cells based on their current operating status information, screen out the battery cells that meet the thermal reliability conditions and the equalization participation conditions, and construct a candidate battery cell set.

[0066] The first equalization module is used to calculate the attenuation deviation of the candidate cells based on the health status and equalization available quota of the candidate cells in the candidate cell set, determine at least one pair of equalization cell pairs based on the ranking of the attenuation deviation, and control the donor cell in at least one pair of equalization cell pairs to perform an active equalization action to the recipient cell.

[0067] The aforementioned energy storage system's balancing method and system, before executing active balancing in the first balancing mode, evaluate multiple battery cells based on their current operating status information, selecting cells that meet thermal reliability and balancing participation conditions to construct a candidate cell set. Based on the health status and available balancing capacity of the candidate cells in the set, the attenuation deviation of the candidate cells is calculated. At least one pair of balancing cells is determined according to the ranking of attenuation deviations, and the donor cell in the balancing cell pair performs active balancing to the recipient cell. Through thermal reliability constraints, participation in balancing is avoided. The safety risks caused by overheating of the cells due to balancing current are addressed by constraining the frequency of balancing participation by cells through balancing participation conditions. This allows active balancing to rotate among the cells, preventing individual cells from deteriorating faster due to frequent balancing participation. By assessing the health status and available balancing capacity of candidate cells and calculating their attenuation deviation, active balancing is prioritized for cells with larger attenuation deviation differences. This gradually reduces the aging differences between cells, making the aging of multiple cells in the energy storage system more consistent and extending the overall lifespan of the energy storage system to a greater extent. Attached Figure Description

[0068] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0069] Figure 1 This is a flowchart of an energy storage system balancing method in one embodiment;

[0070] Figure 2 This is a schematic diagram of the process for constructing a candidate battery cell set in one embodiment;

[0071] Figure 3 This is a schematic diagram of the process for determining a candidate battery cell set in one embodiment;

[0072] Figure 4 This is a flowchart illustrating the process of calculating the attenuation deviation of a candidate battery cell in one embodiment.

[0073] Figure 5 This is a schematic diagram of the process of assembling at least one pair of balanced cells in one embodiment;

[0074] Figure 6 This is a schematic diagram of the process for assembling at least one pair of balanced cells in another embodiment;

[0075] Figure 7 This is a flowchart of the second equalization mode execution in one embodiment;

[0076] Figure 8 A flowchart of an energy storage system balancing method in another embodiment;

[0077] Figure 9 This is a structural block diagram of an energy storage system in one embodiment;

[0078] Figure 10 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0080] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0081] Firstly, this application provides a balancing method for an energy storage system. The energy storage system includes multiple battery cells, which are connected in parallel or series to form a battery pack. The method is executed by a terminal of the energy storage system, which can be the battery management system of the energy storage system. Figure 1 As shown, the balancing method includes steps S110-S140.

[0082] Step S110: Collect the current operating status information of multiple battery cells.

[0083] In this embodiment, after the system starts, the battery management system collects the operating status information of each cell in real time according to a preset sampling period. The operating status information of the cell may include the cell's terminal voltage, charging and discharging current, surface temperature, state of charge, and health status.

[0084] The battery management system collects the terminal voltage Vi, charging and discharging current Ii, and surface temperature Ti of each individual cell through a voltage sampling circuit, a current Hall sensor, and a temperature sensor attached to the surface of each cell, according to a preset sampling period (exemplarily, 10ms to 100ms).

[0085] Furthermore, the microcontroller built into the battery management system estimates the state of charge (SOCi) and state of health (SOHi) of each cell online based on the collected voltage and current information.

[0086] Step S120: Based on the current operating status information of multiple cells, when the energy storage system meets the first trigger condition, it enters the first equalization mode.

[0087] The terminal obtains the charge dispersion ΔSOCrange and aging dispersion Daging of multiple battery cells based on the current operating status information of multiple battery cells.

[0088] The terminal determines the balancing mode of the energy storage system based on the charge dispersion ΔSOCrange and aging dispersion Daging of multiple cells. When the energy storage system meets the first trigger condition, it determines that a significant deviation has occurred in the aging consistency among the cells, while the state of charge is not in an extremely unbalanced state, thus providing a safe window for performing aging coordination balancing. At this point, the terminal enters the first balancing mode, i.e., the active aging coordination mode, and executes the control logic of subsequent steps S130 to S140.

[0089] Step S130: Based on the current operating status information of multiple cells, evaluate the multiple cells, select cells that meet the thermal reliability conditions and equalization participation conditions, and construct a candidate cell set.

[0090] In this embodiment, after the terminal enters the first equalization mode, thermal reliability assessment and equalization participation condition assessment are performed on each battery cell.

[0091] In the thermal reliability assessment, the terminal estimates the final temperature of the battery cell after performing the preset equalization action based on the cell's surface temperature, ambient temperature, preset equalization current, DC internal resistance, equivalent thermal resistance, and thermal time constant. If the predicted temperature does not exceed the preset safety threshold, the battery cell passes the thermal reliability screening; otherwise, the battery cell is marked as thermally unsafe and removed from the candidate set in this round.

[0092] In the balance participation condition screening, the terminal obtains the current available balance quota of the battery cell and estimates the quota required for this balance action. If the current available quota is not less than the estimated consumption value, the battery cell passes the balance participation condition screening; otherwise, the battery cell is marked as having insufficient quota, forced into a silent rest period, and removed from the candidate set in this round. Battery cells that pass both of the above screenings are included in the candidate battery cell set.

[0093] Step S140: Calculate the attenuation deviation of the candidate cells based on the health status and available balance quota of the candidate cells in the candidate cell set, determine at least one pair of equalizing cells based on the order of attenuation deviation, and control the donor cell in the at least one pair of equalizing cells to perform active equalization action to the recipient cell.

[0094] The terminal performs a comprehensive evaluation of each cell in the candidate cell pool. The battery management system calculates the degradation deviation of each candidate cell based on the health status and current balance available capacity of each candidate cell to determine that the donor cell and the recipient cell constitute at least one pair of balance cells. The system then controls the donor cell in at least one pair of balance cells to perform an active balancing action to the recipient cell to transfer energy.

[0095] In this application, the available balance quota refers to the remaining available throughput capacity of a battery cell in its current state, allowing it to participate in active balancing operations. A higher available balance quota indicates that the battery cell has ample available throughput capacity at the current moment, possessing sufficient capability to participate in new balancing operations; a lower available balance quota indicates that the battery cell has recently accumulated a significant amount of balancing throughput, and its remaining available quota is insufficient, requiring an appropriate reduction in its balancing load. It should be noted that the available balance quota is a dynamically changing virtual quota. Its initial value is set based on the thermodynamic limits of the battery cell and is updated in real-time throughout its entire lifespan as balancing operations are consumed and the cell recovers from rest periods, thus linking the allocation of balancing tasks to the actual heat generation and dissipation physical processes of each battery cell.

[0096] In this application, throughput capacity refers to the cumulative charge flow allowed through the cell within the thermodynamic safety boundary. Remaining usable throughput capacity characterizes the real-time dynamic margin after deducting historical cumulative throughput consumption at the current moment, and is used to characterize the cell's tolerance margin to withstand additional equalization current surges under current operating conditions.

[0097] It should be noted that the cumulative charge throughput used to define throughput capacity in this application refers to the cumulative current flowing through the cell generated by the active balancing action, excluding the load current generated under normal charging and discharging conditions of the cell.

[0098] In this application, the attenuation deviation is a comprehensive quantitative index used to characterize the priority of a candidate cell as a donor cell to undertake energy output tasks in the current state. Its value is determined by factors in two dimensions.

[0099] The first dimension is the degree of deviation of the candidate cell's health status, that is, the direction and magnitude of the deviation of the candidate cell's current health status from the average health level of all cells in the battery pack. If the health status of a candidate cell is higher than the average of the battery pack, it indicates that the cell is relatively healthier, with lower internal resistance and better capacity retention. In its current state, it has better charge and discharge acceptance and lower aging sensitivity, making it suitable as a donor cell (energy output) to undertake balancing tasks. Conversely, if the health status of a candidate cell is lower than the average of the battery pack, it indicates that the cell is relatively weaker, with higher internal resistance and faster capacity degradation. It should be used as a recipient cell (energy receiver) to obtain protection and avoid accelerated aging due to further discharge.

[0100] The second dimension is the sufficiency of the current balance available capacity of the candidate battery cell. The higher the balance available capacity, the smaller the cumulative burden this battery cell has undertaken in historical balance tasks, and the more available throughput capacity it currently has to support its participation in new balance operations. The lower the balance available capacity, the more the battery cell has undertaken a lot of balance throughput recently, and the heat accumulation has reached a high level. It should be allowed to rest and recover rather than continue to participate in balance tasks.

[0101] After identifying the donor and acceptor cells, the battery management system issues control commands to establish an energy transfer path between the donor and acceptor cells, enabling energy to be transferred from the donor cell to the acceptor cell, thereby achieving a redistribution of charge state within the system.

[0102] After the balancing process is completed, the battery management system updates the available balancing allowance for both the donor and recipient cells based on the actual throughput of this balancing operation. The donor cell, having incurred the costs of aging and heat loss due to energy output, has its available balancing allowance reduced accordingly. The recipient cell, having also undergone a charge-discharge process while receiving energy, also has its available balancing allowance reduced, but by a smaller margin than the donor cell. Cells that did not participate in any balancing operations during this cycle, however, have had time for natural cooling and polarization recovery, allowing their available balancing allowance to partially recover. Through this dynamic update mechanism of available balancing allowance, the battery management system achieves a fair rotation of the balancing burden throughout its entire lifecycle.

[0103] The aforementioned energy storage system balancing method, before executing active balancing in the first balancing mode, evaluates multiple battery cells based on their current operating status information, selecting cells that meet thermal reliability and balancing participation conditions to construct a candidate cell set. Based on the health status and available balancing capacity of the candidate cells in the set, the attenuation deviation of the candidate cells is calculated. At least one pair of balancing cells is determined according to the ranking of attenuation deviations. In this pair, the donor cell performs active balancing on the recipient cell. Through thermal reliability constraints, the method avoids situations where the cells participating in balancing are not properly balanced. The safety risks caused by overheating due to balancing current are addressed by constraining the frequency of balancing participation by individual cells through balancing participation conditions. This ensures that active balancing actions rotate among the cells, preventing individual cells from deteriorating faster due to frequent balancing participation. By assessing the health status and available balancing capacity of candidate cells and calculating their attenuation deviation, active balancing actions are prioritized for cells with larger attenuation deviation differences. This gradually reduces the aging differences between cells, making the aging of multiple cells in the energy storage system more consistent and extending the overall service life of the energy storage system to a greater extent.

[0104] In some embodiments, the current operating status information of the battery cell includes state of charge and health status; such as Figure 2As shown, step S130 evaluates multiple battery cells based on their current operating status information, selects cells that meet the thermal reliability and equalization participation conditions, and constructs a candidate battery cell set, including steps S131 to S132.

[0105] Step S131: Based on the current operating status information of multiple cells and the preset balancing current, determine the predicted temperature of multiple cells after balancing, and based on the historical balancing participation data of multiple cells, determine the current balancing available amount of multiple cells.

[0106] In this embodiment, the thermal reliability condition is that the predicted temperature of the battery cell is lower than a preset safe temperature threshold. The preset safe temperature threshold is a pre-set maximum temperature limit that the battery cell is allowed to reach; for example, the preset safe temperature threshold can be set to 60°C.

[0107] In this embodiment, the participation condition for balancing is that the available balancing quota of a battery cell is higher than the balancing participation benchmark value. The balancing participation benchmark value is the balancing cost required to execute the expected balancing action in this round, which is also the participation consumption value. In other words, a battery cell is considered capable of participating in this round of balancing only if its current available balancing quota is greater than the balancing cost required to execute the balancing action in this round. If a battery cell's current available balancing quota is less than or equal to the balancing cost required to execute the balancing action in this round, then this battery cell is considered to have insufficient available balancing quota and enters a mandatory rest period, during which it is prohibited from participating in any balancing action in this round.

[0108] Step S132: Select cells whose predicted temperature is lower than the preset safe temperature threshold and whose available balance is higher than the balance participation benchmark value as candidate cells to construct a candidate cell set.

[0109] Through the dual screening mechanism of thermal reliability conditions and equalization participation conditions, cells whose predicted temperature is lower than the preset safe temperature threshold and whose equalization availability is higher than the equalization participation benchmark value are selected as candidate cells. All candidate cells constitute a candidate cell set for subsequent equalization cell pair matching.

[0110] It should be noted that this application does not limit the execution order of the predicted temperature calculation and the determination of the available balance allowance in step S131. The battery management system may calculate the predicted temperature first and then determine the available balance allowance, or it may determine the available balance allowance first and then calculate the predicted temperature, or both may be executed in parallel, all of which are within the scope of protection of this application.

[0111] In some embodiments, the current operating status information of the battery cell further includes the surface temperature of the battery cell; step S131 determines the current balanced available quota of multiple battery cells, including:

[0112] Step S1311: Based on the surface temperature of multiple cells, the ambient temperature, and the preset balancing current, calculate the predicted temperature of multiple cells after performing active balancing based on the thermal reliability model; cells whose predicted temperature is lower than the preset safe temperature threshold are determined to meet the thermal reliability conditions.

[0113] For each cell, the battery management system uses its built-in thermal reliability model to predict temperature based on the cell's current surface temperature, state of charge, state of health, preset balancing current, and preset balancing duration. The thermal reliability model considers both the Joule heating effect generated by the cell under the balancing current and the cell's heat dissipation capacity to the environment, enabling it to accurately predict the final temperature of each cell after completing the current balancing process.

[0114] Furthermore, the thermal reliability model calculates the temperature rise attenuation of the battery cell during the equalization period based on the cell's surface temperature, ambient operating temperature, preset equalization time, and thermal time constant; it calculates the cumulative temperature rise of the battery cell during the equalization period based on the preset equalization current, the cell's DC internal resistance, and equivalent thermal resistance; and it obtains the predicted temperature by superimposing the ambient operating temperature, temperature rise attenuation, and cumulative temperature rise.

[0115] Furthermore, the thermal reliability model is as follows:

[0116] ;

[0117] Among them, T end T is the predicted temperature of the battery cell. curr T is the surface temperature of the battery cell. amb Operating ambient temperature; I bal Preset equalization current; R in R is the DC internal resistance of the battery cell; th τ is the equivalent thermal resistance of the battery cell to the environment; τ is the thermal time constant; Δt is the preset equalization time.

[0118] Operating ambient temperature T amb It is the temperature of the operating environment of the energy storage system, which can be obtained through the ambient temperature NTC sensor on the BMS board, or by obtaining the temperature of the non-working cells in the system that are in thermal equilibrium.

[0119] Preset equalization current I bal The equalization current amplitude is preset by the terminal and is determined in advance by the battery management system according to the current equalization strategy; the DC internal resistance is the DC internal resistance of the cell in the current state, which is obtained from a pre-calibrated multi-dimensional characteristic lookup table. The lookup table is stored in the non-volatile memory of the battery management system controller and is obtained by real-time interpolation using the current state of charge (SOC) and surface temperature (T) of the cell as indexes.

[0120] In one implementation, the multidimensional characteristic lookup table is a parameter correspondence table pre-constructed based on the current state of charge and surface temperature of the battery cell. The multidimensional characteristic lookup table stores DC internal resistance data that matches different combinations of current state of charge and surface temperature.

[0121] The preset balancing duration Δt is the duration of this round of balancing action, which is preset by the battery management system, and can be 60 seconds for example.

[0122] Equivalent thermal resistance R th The unit is ℃ / W, which characterizes the ease with which the battery cell dissipates heat to the environment. It is determined in advance through a steady-state temperature rise experiment.

[0123] The thermal time constant τ is a physical parameter characterizing the magnitude of the inertia of temperature change in a battery cell, measured in seconds. τ = R th ×C th Among them, C th The heat capacity of the battery cell is calculated from the total mass of the cell and the weighted average specific heat capacity, or determined by fitting the temperature rise rate of a transient temperature rise experiment.

[0124] In the above thermal reliability model, The term characterizes the cumulative temperature rise of the battery cell due to the Joule heating effect under the action of equalization current, reflecting the heat input generated by the equalization current through the internal resistance of the battery cell and the accumulation process of heat under the action of thermal time constant. The term characterizes the temperature rise decay caused by heat dissipation from the battery cell to the environment during the equalization period, reflecting the natural cooling process driven by the difference between the current surface temperature and the ambient temperature. The model uses the operating ambient temperature as the reference temperature, and superimposes the above-mentioned cumulative temperature rise and temperature rise decay to finally obtain the predicted temperature of the battery cell after the equalization process is completed.

[0125] The battery management system will calculate the predicted temperature T end Compared with the preset safe temperature threshold, if the predicted temperature T end If the temperature is below the preset safe temperature threshold, the battery management system determines that the cell meets the thermal reliability requirements and allows it to enter the subsequent candidate cell set construction process; if the predicted temperature T end If the preset safe temperature threshold is reached or exceeded, the cell is determined to not meet the thermal reliability requirements.

[0126] Furthermore, the thermal reliability condition may also include a reserved safety margin. That is, the judgment condition can be that the predicted temperature of the cell is lower than the preset safe temperature threshold minus the safety margin. For example, the safety margin can be 3°C. In other words, the cell is deemed to meet the thermal reliability condition only when the predicted temperature is below 57°C. By setting a safety margin, sufficient safety margin is reserved for the system in the event of sudden disturbances or model errors. If the predicted temperature of a cell reaches or exceeds this safe temperature threshold, the cell is considered thermally limited, and regardless of its state of charge, it is forcibly excluded from the candidate cell set in this round of equalization.

[0127] In some embodiments, refer to Figure 2 In step S130, multiple cells are evaluated and cells that meet the thermal reliability and equalization participation conditions are selected. Before step S132, steps S133 to S134 are also performed.

[0128] Step S133: Based on the balanced available amount of multiple cells, predict the participation consumption value after multiple cells perform active balancing action.

[0129] The battery management system obtains the balance available amount of each cell in the battery pack, and predicts the participation consumption value of each cell after performing the active balance action based on the balance available amount of each cell and the expected balance action parameters.

[0130] The battery management system presets an upper limit for the equalization available capacity of each cell, which is also the total available capacity. In some embodiments, the equalization available capacity is represented by a credit score, and the total available capacity is the upper limit of the credit score, which can be 100 points. The equalization available capacity of each cell is stored in the non-volatile memory of the battery management system and is updated and maintained after each equalization operation is completed.

[0131] In this step, the battery management system first reads the current balance availability of each cell. The higher the balance availability, the more remaining available throughput capacity the cell currently has for participating in the balance process; the lower the balance availability balance, the more the cell has recently undertaken a significant amount of balance throughput and is currently approaching its allowed balance limit.

[0132] The battery management system uses the preset equalization current I to... bal With a pre-set balancing duration Δt, the expected consumption of each cell after performing this round of active balancing is calculated. This expected consumption is the participation consumption value (Cost). action In this embodiment, the battery management system multiplies the expected amount of transferred charge by a preset consumption coefficient k to calculate the participation consumption value (Cost) of each cell after performing this round of equalization. action The expected amount of charge transferred is determined by the preset equalization current I.bal The value is determined by multiplying the value by the preset equilibrium duration Δt. For example, if the expected amount of charge transferred is 0.1 Ah and the consumption coefficient is 100 points / Ah, then the participation consumption value is 10 points.

[0133] Cost action =k×I bal ×Δt.

[0134] It should be noted that in this step, the battery management system predicts the participation consumption value of each cell in the battery pack, regardless of whether the cell will act as a donor or acceptor cell in subsequent matching. This is because, whether it is discharge balancing or charge balancing, the cells participating in the balancing process will undergo the process of current flow, which will generate corresponding Joule heat and aging stress, and thus consume their available balancing capacity.

[0135] It is understood that the consumption coefficient k is not fixed, but dynamically adjusted according to the health status of the battery cell. In this embodiment, the battery management system assigns a larger consumption coefficient k to cells with lower health status, causing the aging cells to consume their credit faster when participating in balancing operations with the same throughput, thus entering the forced rest period earlier; and assigns a smaller consumption coefficient to cells with higher health status, allowing them to undertake more balancing tasks under the same throughput. This achieves differentiated protection for aging cells and further optimizes the aging consistency management effect throughout the entire life cycle.

[0136] Step S134: Compare the balance available amount and participation consumption value of multiple cells respectively. Cells whose balance available amount is greater than or equal to the participation consumption value are determined to meet the balance participation conditions.

[0137] The battery management system sets the current equalization available amount Ci for each cell and its corresponding participation consumption value Cost. action A comparison is made. If the current available balance allowance Ci of a certain battery cell is greater than or equal to its participation consumption value Cost... action If the battery cell has sufficient remaining capacity to participate in this round of balancing, the battery management system determines that the battery cell meets the balancing participation conditions and allows it to participate in this round of balancing scheduling.

[0138] If the current available balance credit Ci of a certain battery cell is less than its participation consumption value Cost actionThis indicates that the cell's current remaining capacity is insufficient to participate in the current balancing process, meaning the cell has recently undertaken too much balancing throughput, and its accumulated heat and polarization state have not yet been fully recovered. In this case, the battery management system determines that the cell does not meet the balancing participation conditions, marks the cell as "overdrawn," and forces it into a rest period. Cells entering the forced rest period are completely excluded from this round of balancing scheduling, neither acting as energy donors nor energy receivers.

[0139] In this way, only cells with sufficient available balance are allowed to participate in this round of balancing, while cells with overdrawn balance are forced to rest. This restricts the frequency and cumulative throughput of each cell participating in balancing, enabling the active balancing action to achieve fair rotation among cells based on remaining balance. This effectively prevents individual cells from deteriorating faster due to frequent participation in balancing and long-term throughput tasks.

[0140] In some embodiments, the dynamic adjustment method of the consumption factor is as follows: using the internal resistance of the cell at the beginning of its life (BOL) as a reference value, the ratio of the current internal resistance to the reference value is multiplied by the reference consumption factor to obtain the current consumption factor of the cell. Since the internal resistance of aged cells is usually significantly higher than that of new cells, this dynamic adjustment method automatically increases the consumption factor of aged cells.

[0141] In some embodiments, candidate cells include basic candidate cells and restricted candidate cells; the balanced availability limit includes a disabled interval, a restricted interval, and an available interval. The battery management system performs hierarchical screening of all cells in the battery pack based on the interval in which each cell's balanced availability limit falls, to construct a candidate cell set. The balanced availability limit has a preset upper limit value C. max =100, which is the total capacity of the balanced available credit limit. The balanced available credit limit has a preset lower limit C. Min =0. The battery management system divides the range of available balance into three consecutive intervals, from high to low: available interval, limited interval, and disabled interval.

[0142] Cells whose available balance is within the available range are included in the candidate cell set as basic candidate cells; the available range means that the cell currently has a sufficient balance available balance and has enough remaining available throughput capacity, and can participate in the active balancing action normally with the preset balancing current without generating excessive heat accumulation or aging stress.

[0143] Cells whose available balance is in the restricted range are included in the candidate cell set as restricted candidate cells. The restricted range means that the cell's current available balance has been consumed to a low level, and its remaining available throughput capacity is limited. Although it has not yet reached the level of complete disabling, it no longer meets the conditions for participating in the balance with the preset balance current.

[0144] Cells whose available balance quota is in the disabled zone are excluded from the candidate cell set. The disabled zone means that the cell's current available balance quota has been exhausted or is below the minimum participation threshold. Its remaining available throughput capacity is insufficient to safely undertake any balance operation. The cell enters a forced rest period and will not participate as a donor or recipient in this round of balance.

[0145] Furthermore, step S140 also includes: if the candidate cells are restricted from participating in the active balancing action, the balancing current of the restricted candidate cells is set to be less than the balancing current of the basic candidate cells.

[0146] For cells included in the candidate cell set but located in the restricted area, the battery management system applies a current derating constraint during the balancing process. This means that cells in the restricted area are driven to participate in balancing at an amplitude lower than the standard balancing current. For example, the allowable balancing current for a restricted candidate cell is limited to 50% of the allowable balancing current for the base candidate cell. Through this derating process, while restricted candidate cells are allowed to participate in balancing, their heat generation and aging stress per unit time are significantly reduced, preventing performance degradation from being exacerbated by large current surges.

[0147] In practical applications, the division of the usable range, restricted range, and prohibited range can be adaptively adjusted according to the thermal characteristics of the battery cell, the equalization current amplitude, and the heat dissipation conditions, all of which are within the protection scope of this application.

[0148] In this way, basic candidate cells with sufficient available balance allowance participate in balance normally with the preset balance current, ensuring balance execution efficiency; limited candidate cells with insufficient but not yet exhausted balance allowance participate in balance to a limited extent with reduced current, which avoids their complete departure from balance scheduling and thus deterioration of consistency, and effectively controls their thermal load and aging stress through current derating; disabled cells with completely overdrawn balance allowance are forced to rest, obtaining sufficient time for thermal recovery and polarization dissipation. The above-mentioned hierarchical mechanism enables cells to achieve a smooth transition from full-capacity normal participation to limited participation with reduced current and then to forced rest and recovery throughout their entire life cycle, which not only ensures the continuous availability of the balance function, but also controls the balance participation burden of each cell within its tolerable balance limit to the greatest extent.

[0149] In some embodiments, the derating ratio of a restricted candidate cell dynamically increases as its equalization available capacity decreases. The battery management system adjusts the maximum allowable equalization current of the restricted candidate cell linearly or piecewise linearly based on its current equalization available capacity relative to the restricted range. For example, the derating ratio is set smaller when the equalization available capacity is close to the lower limit of the available range, and larger when the equalization available capacity is close to the upper limit of the restricted range.

[0150] In some embodiments, refer to Figure 4Step S140 calculates the attenuation deviation of the candidate cells based on the health status and balanced available quota of the candidate cells in the candidate cell set, including steps S141 to S142.

[0151] Step S141: Calculate the average health status of the candidate cell set based on the health status of at least one candidate cell in the candidate cell set.

[0152] The battery management system (BMS) acquires the health status of each candidate cell in the candidate cell set. Based on the health status of at least one candidate cell in the set, it calculates the average health status of the candidate cell set. Further, the BMS sums the health status values ​​of all candidate cells in the set and divides this sum by the total number of cells in the set to obtain the average health status. This average health status reflects the average aging level of the entire candidate cell set at the current moment and serves as a benchmark reference value for subsequent calculations of the relative aging deviation of each candidate cell.

[0153] Step S142: Based on the average health status, the health status of candidate cells, and the available balance quota, calculate the attenuation deviation of candidate cells using the balance tendency function. The attenuation deviation characterizes the priority of a candidate cell as a donor or recipient cell, so that the health status differences among multiple cells decrease as the active balance action is executed.

[0154] The equilibrium tendency function determines the attenuation deviation of a candidate cell based on the degree of deviation of the candidate cell's health status from the mean of its health status, and the remaining proportion of the candidate cell's available equilibrium capacity relative to the total capacity.

[0155] The remaining ratio of the balanced available quota of candidate cells to the total quota capacity refers to the ratio of the balanced available quota to the total quota capacity.

[0156] The degree of deviation of the health status of a candidate cell from the mean health status reflects the relative aging level of the cell in the current battery pack. A positive difference indicates that the cell's health status is above average, meaning the cell is relatively healthier, with lower internal resistance, better capacity retention, and superior charge / discharge acceptance. A negative difference indicates that the cell's health status is below average, meaning the cell is relatively weaker, with higher internal resistance and faster capacity degradation. In balanced scheduling, it should be inclined to receive energy rather than output energy to avoid further accelerated aging.

[0157] The balance tendency function calculates the proportion of the current available balance quota of the candidate battery cell to the total quota capacity. The proportion reflects the sufficiency of the remaining throughput capacity that the battery cell can currently participate in the balance. The higher the proportion, the less balance burden the battery cell has undertaken in the near future; the lower the proportion, the more balance throughput the battery cell has undertaken in the near future, and it should rest and recover in the near future.

[0158] The equilibrium tendency function weights and fuses the above-mentioned health status deviation value and the remaining proportion of the equilibrium available quota according to their respective preset weights, and outputs the attenuation deviation of the candidate battery cell.

[0159] In some embodiments, the equilibrium tendency function is as follows:

[0160] .

[0161] in, i represents the attenuation deviation of the candidate cell; SOHi represents the health status of the cell; SOH avg Ci represents the average health status of the candidate cell set; Ci is the balanced available capacity of the cells; C max To balance the total available credit capacity; α is the aging weight; β is the weight for balancing available credit.

[0162] The weight β for the balanced available credit is set to 1, and the weight α for aging is set to 1~40. This ensures that both dimensions contribute appropriately to the calculation of the attenuation deviation.

[0163] In some embodiments, during the early stages of a battery pack's lifespan, the differences in health status between individual cells are typically small. The battery management system sets the aging weight α to a small value, such as 1-5, to prevent misjudgments due to estimation errors. As the battery pack ages, some cells begin to age faster than others, and the degree of differentiation in health status among cells becomes apparent. The impact of cell consistency differences on the overall performance of the battery pack gradually increases. At this point, maintaining a low α value during the early stages of life results in overly conservative balancing actions, making it difficult to effectively curb the progression of dispersion. However, using an excessively high α value too early may lead to frequent balancing actions, increasing power consumption. Therefore, during the middle stages of the battery pack's lifespan, the battery management system sets the aging weight α to 6-19. As the battery pack ages further, the degree of differentiation in health status among individual cells gradually increases, and the impact of health status differences on the overall performance and lifespan of the battery pack becomes increasingly significant. At this point, it is necessary to increase the aging weight to strengthen the control of aging consistency correction, making the balancing decision more focused on reducing the differences in health status among individual cells. Therefore, when the battery pack enters the middle and late stages of its life, the battery management system increases the aging weight α to a higher value, such as 20~40, to drive the active balancing action to more actively deliver energy to the weakening cells and strongly correct the ever-expanding aging dispersion.

[0164] It is understandable that battery aging is a non-linear, accelerated process. In the early stages of its lifespan, capacity decay is gradual, and the differences in consistency between cells increase slowly. However, in the later stages of lifespan, the aging rate accelerates, and the dispersion increases. Therefore, in this application, the aging weight α does not increase linearly with battery aging, but rather non-linearly. The rate of change of the aging weight α is positively correlated with the rate of battery capacity decay. In this way, the balancing action can better match the battery aging process, achieving a balance between efficiency and energy consumption.

[0165] It should be noted that in this application, "early lifespan", "mid lifespan" and "late lifespan" are based on the battery's real-time state of health (SOH). pack Make a judgment. For example, by setting a first health threshold (e.g., SOH). pack1 =90%) and the second health threshold (e.g., SOH) pack2 =80%), dynamically dividing the actual operating range of the battery into initial, middle, and late stages. When the real-time SOH pack ≥SOH pack1 When the SOH is at its peak, it is considered to be in the early stages of its lifespan; when the SOH is at its peak... pack2 Real-time SOH pack <SOH pack1 When the real-time SOH is at that point, it is determined to be in the middle of its lifespan; when the real-time SOH is at that point... pack ≤SOH pack2 At that time, it was determined to be in the mid-to-late stage of its lifespan. Among them, SOH pack1 SOH pack2 The value is not fixed and can be preset according to the actual aging characteristic curve of the target cell.

[0166] It is understandable that the aging and degradation process of energy storage batteries, such as lithium-ion batteries, has non-linear characteristics, and the capacity decay curve typically shows a trend of initial flattening followed by accelerated decay. In the initial stages of use, the capacity decay rate is relatively slow, and the consistency differences between cells increase gradually. However, once the battery's health deteriorates to a certain critical value, internal side reactions (such as lithium deposition and loss of active materials) accelerate, leading to a precipitous capacity decay and a sharp increase in cell dispersion. This critical value (i.e., the aging inflection point) varies depending on the cell's chemical system, electrode materials, electrolyte formulation, and actual operating conditions such as ambient temperature and charge / discharge rate, and cannot be predefined by a uniform number of cycles or percentage of lifespan.

[0167] Among them, the battery management system can monitor the average health status of all cells in the battery pack in real time, and use the average health status as the basis for determining the overall aging stage of the battery pack, and dynamically adjust the value of the aging weight α in the equilibrium tendency function.

[0168] In some embodiments, after step S140 controls the donor cell in at least one pair of equalizing cells to perform an active equalization action to the recipient cell, the equalization method of the energy storage system further performs step S150: updating the equalization available quota of each cell.

[0169] In this embodiment, the deduction or restoration of balancing quota is performed based on whether each cell actually participated in the active balancing action during the current control cycle. For cells that actually participated in the balancing action during the current control cycle, their corresponding available balancing quota is deducted according to the following formula: 。

[0170] Among them, C new For the new balanced available credit after settlement, C old To balance available credit before settlement, Ah transferred is the absolute value of the charge flowing through the cell during this operation (in Ah), and k is the consumption coefficient (in minutes / Ah), which represents the cost required to transport 1 Ah of energy, and represents the cost of balancing the cell's lifespan and heat accumulation.

[0171] For cells that did not participate in any balancing actions during this control cycle and are in a static state, their available balancing quota will be restored according to the following formula: C new =C old +r*t idle .

[0172] Among them, t idle The cumulative resting time of the cell when it does not participate in active balancing (the unit can be minutes or seconds depending on the system configuration), and r is the capacity recovery rate (the unit is minutes / minute or minutes / second), which represents the capacity value that can be recovered per unit rest time, representing the cell's heat dissipation capacity or polarization recovery capacity.

[0173] It should be noted that the balanced available credit limit has a preset upper limit C. max (Total available capacity for balanced credit) and lower limit C min (lower limit C) min =0). After performing the update of the available balance quota, if C new >C max Then reset Cnew to C max If C new <0, then C new Reset to 0. The consumption factor k is set according to the maximum continuous thermal tolerance of the energy storage system, so that the available capacity of the battery cell is reduced to zero when the thermal boundary is reached.

[0174] In some embodiments, the consumption coefficient k is set as follows: First, set the upper limit C of the balanced available credit. max For example, Cmax =100. Determine the limiting working time T. limit : with maximum equalization current Imax Continuous operation, recording the rise of the battery cell from the current ambient temperature to the preset maximum safe temperature T. safe The required time, for example, T safe =60℃. For example, T limit =20min. Then, calculate the amount of charge transferred during this period: Ah limit =I max ×20 / 60.

[0175] To ensure that the battery cell can operate continuously at the maximum equalization current T limit Balance available credit from C max It just reaches zero, and the consumption coefficient k=C max / Ah limit .

[0176] The capacity recovery rate r is set based on the heat dissipation time constant of the energy storage system, ensuring that the available capacity of the cells is evenly reset after heat dissipation. The method for setting the capacity recovery rate r is as follows: Measure the cooling recovery time T. cool Record the battery cell temperature from its highest safe temperature T safe (Example, T) safe The time required for the temperature (e.g., 60°C) to naturally cool back to the preset safety baseline. For example, T... cool =10min.

[0177] To ensure that the available capacity of the battery cells recovers exactly from 0 to C when they are resting, max Credit limit recovery rate r=C max / T cool Among them, T cool The unit and t idle The units should be kept consistent.

[0178] In some embodiments, the balanced available credit limit includes a first balanced available credit limit and a second balanced available credit limit, wherein the first balanced available credit limit... Used to characterize the leveling participation of the i-th cell as a donor cell, the second leveling available quota Used to characterize the degree of balanced participation of the i-th cell as the recipient cell.

[0179] like Figure 3 As shown, step S130 evaluates multiple battery cells and selects those that meet the thermal reliability and equalization participation conditions, including steps S130-1 to S130-4.

[0180] Step S130-1: Obtain the first and second balanced available quotas for multiple battery cells respectively.

[0181] In this embodiment, both the first and second balanced available credit limits can be quantified in the form of credit scores, and both have preset upper limits (exemplarily, the upper limit can be 100 points each), with initial values ​​set to the upper limits. The first and second balanced available credit limits are independent of each other, and are recorded, consumed, and restored separately.

[0182] It is understandable that the aging mechanisms of a battery cell as an output and as a receiver are not entirely the same. For example, at the end of charging, when the cell is a receiver, it may be more affected by side reactions in the high state of charge range (such as lithium plating and electrolyte oxidation), increasing the aging cost of its received energy. Conversely, at the end of discharging, when the cell is an output, it may be more affected by polarization and available capacity constraints in the low state of charge range, correspondingly increasing the aging cost and thermal risk of its output energy. Therefore, using direction-dependent balancing available capacity allows for finer-grained constraints on balancing behavior. The participation frequency of the donor cell is constrained separately by the output balancing available capacity, and the participation frequency of the receiver cell is constrained separately by the receiver balancing available capacity, thereby achieving targeted protection for the donor and / or receiver cells under different operating conditions.

[0183] Step S130-2: Based on the first equalization available quota of multiple battery cells, filter the multiple battery cells and include the battery cells that meet the first output equalization condition into the first output candidate set.

[0184] The battery management system will equalize the available capacity of each cell. With the first minimum available threshold Comparison. When ≥ When a cell is determined to meet the first output equalization condition, it is included in the first output candidate set. .

[0185] Among them, the first minimum available threshold This is a preset threshold, representing the minimum available balance allowance required for a battery cell to participate in the balance distribution process as a donor cell. When the first available balance allowance of a battery cell falls below the first minimum available threshold... When the available capacity of the battery cell as a power source has been depleted to a low level, continuing to use it as a power source for balancing may lead to overheating or accelerated aging. Therefore, the use of the battery cell as a power source for balancing should be restricted.

[0186] Step S130-3: Based on the second equalization available quota of multiple battery cells, filter the multiple battery cells and include the battery cells that meet the first receiving equalization conditions into the first receiving candidate set.

[0187] The battery management system obtains the second equalization available amount of each cell within the module. The second equalization available quota for each battery cell With the second lowest available threshold Comparison. When ≥ At that time, the battery management system determines that the cell meets the first reception equalization condition and includes it in the first reception candidate set. .

[0188] Among them, the second lowest available threshold The preset threshold represents the minimum available balance quota required for a battery cell to participate in the balance process as a recipient battery cell.

[0189] Step S130-4: Determine the candidate cell set based on the first output candidate set and the first receiving candidate set.

[0190] The candidate cell set is the first output candidate set. With the first receiving candidate set The union of the values. Meanwhile, to facilitate donor / recipient pairing, the battery management system also records the eligibility status of each cell in both the output and receiving directions, i.e., whether a cell possesses both donor and recipient eligibility, only donor eligibility, or only recipient eligibility.

[0191] When a battery cell is simultaneously included in the first output candidate set and the first receiving candidate set At any given time, a battery cell can act as both a donor and a receiver, determined by its ranking within the candidate cell set based on its degradation deviation. However, within the same control cycle, the battery management system restricts a single cell to only one of these roles, preventing it from simultaneously acting as both a donor (outputting energy) and a receiver (receiving energy), in order to avoid control command conflicts and unnecessary energy loss.

[0192] In some embodiments, when the first output candidate set Or the first receiving candidate set When the set is empty, meaning there are no cells qualified as donors or acceptors, it is determined that an effective active balancing action cannot be performed in this round. The subsequent steps S140, including attenuation deviation calculation and balancing action execution, are skipped, and the system proceeds to the status monitoring of the next control cycle. This avoids invalid calculations when there are no cells available for scheduling, thus saving system computing resources.

[0193] In this way, whether a cell is eligible to be a donor is determined by its first available balance quota, and whether it is eligible to be a recipient is determined by its second available balance quota. This makes the determination of eligibility for balance participation more precise in both the donor and recipient dimensions, and further optimizes the fair rotation and aging consistency management throughout the entire life cycle.

[0194] In some embodiments, the first output equalization condition further includes: the thermal margin TH of the battery cell. iGreater than or equal to the preset lower limit of heat margin TH min And the terminal voltage V of the battery cell i Greater than or equal to the preset lower voltage limit V min And the surface temperature Ti of the battery cell is less than or equal to the preset upper temperature limit T. lim .

[0195] In other words, the battery management system will include cells that simultaneously meet four conditions: the first equalization available amount is not lower than the first minimum available threshold, the thermal margin is sufficient, the voltage is not lower than the lower limit, and the temperature is not higher than the upper limit, into the first output candidate set. Among them, the first output candidate set .

[0196] In some embodiments, the first balanced available credit The credit limit is divided into three consecutive ranges, from lowest to highest: the disabled range, the restricted range, and the available range. The first lowest available threshold... This is the lower limit of the available range. The battery management system also has an output direction lock-in threshold. ,and < .when ≥ When the cell is in the usable range, it is included in the first output candidate set as the first basic candidate cell, and is allowed to participate in the equalization operation in the output direction with a preset equalization current; when When the cell is in the restricted usage range, it is included in the first output candidate set as the first restricted usage candidate cell, but its allowed output equalization current is limited to be less than the preset equalization current; when At that time, the battery cell is in the disabled range and is excluded from the first output candidate set.

[0197] In some embodiments, the first reception equalization condition further includes: the thermal margin TH of the battery cell. i Greater than or equal to the preset lower limit of heat margin TH min And the terminal voltage V of the battery cell i Less than or equal to the preset upper voltage limit V max And the surface temperature T of the battery cell i Less than or equal to the preset upper temperature limit T lim In other words, the battery management system will include cells that simultaneously meet four conditions in the first receiving candidate set: the second equalization available amount is not lower than the second minimum available threshold, the thermal margin is sufficient, the voltage is not higher than the upper limit, and the temperature is not higher than the upper limit. , .

[0198] In some embodiments, the second balanced available amount The credit limit is divided into three consecutive ranges, from lowest to highest: the disabled range, the restricted range, and the available range. The second lowest available threshold... This is the lower limit of the available range. The battery management system also has a receive direction lock threshold. ,and < .when ≥ ≥ When the battery cell is in the usable range, it is included in the first receiver candidate set as the second basic candidate battery cell, allowing it to participate in the equalization operation in the receiving direction with a preset equalization current; when When the cell is in the restricted usage range, it is included in the first receiving candidate set as the second restricted candidate cell, but its allowed receiving equalization current is limited to less than the preset equalization current; when At that time, the battery cell is in the disabled zone and is excluded from the first reception candidate set.

[0199] In some embodiments, this applies to energy storage systems configured with single-path active balancing hardware, or to low-complexity control modes. For example... Figure 5 As shown, step S140 determines at least one pair of equalizing cells based on the order of attenuation deviation, and controls the donor cell in the at least one pair of equalizing cells to perform an active equalization action on the recipient cell, including:

[0200] Step S1401: Select the candidate cell with the largest concentrated attenuation deviation as the donor cell and the candidate cell with the smallest attenuation deviation as the recipient cell to form at least one pair of balanced cells.

[0201] The battery management system obtains the degradation deviation λi of each candidate cell in the candidate cell set and sorts the degradation deviation λi of all cells in the candidate cell set. For example, the cells in the candidate cell set can be sorted in descending order of degradation deviation to identify the cell with the largest degradation deviation and the cell with the smallest degradation deviation. The battery management system selects the candidate cell with the largest degradation deviation as the donor cell (i.e., the energy output side) and the candidate cell with the smallest degradation deviation as the acceptor cell (i.e., the energy input side), thereby forming at least one pair of balanced cell pairs.

[0202] The cell with the largest attenuation deviation has a health condition above average and ample available balance capacity. It has low internal resistance, good capacity retention, and the ability to handle energy output. Furthermore, the aging cost of its energy output as a donor is relatively small. Conversely, the cell with the smallest attenuation deviation has a health condition below average or its available balance capacity has been depleted to a low level. It has high internal resistance and rapid capacity decay. As a receiver, it can gain energy and avoid accelerated aging due to further discharge. By pairing the two cells with the largest attenuation deviation differences, energy flows from the healthiest cell to the weakest. This gradually reduces the difference in state of charge while simultaneously reducing the difference in health condition, achieving optimal balancing efficiency within limited hardware resource constraints and realizing the goal of consistent aging control.

[0203] In some embodiments, such as Figure 6 As shown, step S140: Determine at least one pair of balanced cells according to the order of attenuation deviation, evaluate multiple cells, and screen out cells that meet the thermal reliability conditions and equalization participation conditions, including steps S140a to S140b.

[0204] Step S140a: Generate output candidate sequences by sorting the attenuation deviations from largest to smallest, and generate receiving candidate sequences by sorting the attenuation deviations from smallest to largest.

[0205] The battery management system (BMS) obtains the degradation deviation λi of each candidate cell in the candidate cell set and sorts all candidate cells in the set bidirectionally according to their degradation deviation. The BMS then sorts all cells in the candidate cell set in descending order of degradation deviation, generating an output candidate sequence Ωoutsorted. In the sequence, the cell with the largest degradation deviation is ranked first, the cell with the second largest degradation deviation is ranked second, and so on. Cells ranked higher in the sequence are considered healthier and have more balanced available capacity, making them more suitable as donor cells for energy output.

[0206] Simultaneously, the battery management system sorts all cells in the candidate cell set in ascending order of their degradation deviation, generating a receiving candidate sequence. In this sequence, the cell with the smallest degradation deviation is ranked first, the cell with the second smallest deviation is ranked second, and so on. Cells ranked higher in the sequence indicate that they are relatively weaker or have less available capacity, making them more suitable as recipient cells for energy reception.

[0207] When generating the output candidate sequence and the receiving candidate sequence, the battery management system also performs a mutual exclusion check for the same battery cell. Since the same battery cell is only allowed to play one role in the same control cycle, when a battery cell appears in the matching position in both the output candidate sequence and the receiving candidate sequence, the battery management system removes this battery cell from the lower-ranked side or moves it to the end of the sequence to avoid the same battery cell being repeatedly scheduled in the same cycle.

[0208] It should be noted that the output candidate sequence and the received candidate sequence in step S140a are the first output candidate set Ω, which has been filtered in step S130. out and the first receiving candidate set Ω in This is a further sorting based on the existing data. In other words, the range for generating output candidate sequences is the first output candidate set, and the range for generating received candidate sequences is the first received candidate set.

[0209] Step S140b: Based on the parallel constraint, pair the candidate cells in the output candidate sequence with the candidate cells in the received candidate sequence that have the same sorting position and whose attenuation deviation difference is greater than or equal to a preset threshold, and form at least one pair of balanced cells.

[0210] Based on preset parallel constraints, the battery management system pairs candidate cells in the output candidate sequence with those in the received candidate sequence that have the same sorting position and whose attenuation deviation difference is greater than or equal to a preset threshold, forming at least one pair of balanced cell pairs. For example, the first-ranked candidate cell in the output candidate sequence is paired with the first-ranked candidate cell in the received candidate sequence to form the first pair of balanced cell pairs; the second-ranked candidate cell in the output candidate sequence is paired with the second-ranked candidate cell in the received candidate sequence to form the second pair of balanced cell pairs; and so on, until a preset termination condition is met.

[0211] For any candidate pairing (p, q), where p is the donor cell and q is the acceptor cell, the minimum equilibrium revenue threshold must be satisfied: Where Δλmin is the preset minimum attenuation deviation difference threshold.

[0212] If the difference in degradation deviation between a pair of candidate cells is less than Δλmin, the balancing gain between the two cells is considered insufficient. This means the difference in their health status and available balancing capacity is too small, and the state-of-charge alignment gain obtained from balancing is insufficient to offset the losses and aging costs associated with energy conversion. For such pairs, the battery management system will no longer include them in the parallel balancing set to avoid ineffective energy transport and additional thermal burden.

[0213] The minimum attenuation deviation threshold Δλmin is determined as follows: First, the attenuation deviation λi of each candidate cell is normalized to [0, 1], and the value of Δλmin ranges from 0.03 to 0.20. Preferably, it is 0.05 to 0.15; more preferably, it is 0.10.

[0214] In some embodiments, the parallel constraint includes the parallel balancing capacity M; the parallel balancing capacity M is determined based on the available balancing resources of the energy storage system and the number of candidate cells in the candidate cell set.

[0215] When pairing output candidate sequences with received candidate sequences, an upper limit on the number of pairings is set according to the parallel balancing capacity M; the upper limit on the number of pairings is not greater than the parallel balancing capacity M. That is, the parallel balancing capacity M is used to limit the maximum number of balancing actions that can be executed simultaneously within the same control cycle. The parallel balancing capacity M is determined based on the available balancing resources of the energy storage system and the number of candidate cells in the candidate cell pool.

[0216] For example, parallel balancing capacity .

[0217] M hw This represents the maximum number of equalization channels allowed by the energy storage system hardware. The total number of candidate battery cells in the pool; The maximum number of parallel operations is determined by the equalization power supply or bus power limit; This represents the maximum number of parallel operations determined by the thermal margin constraint.

[0218] If the number of matching cell pairs in the output candidate sequence and the received candidate sequence exceeds the parallel balancing capacity, the battery management system will only match the first M pairs according to their sorting position, and the remaining cell pairs will be processed in subsequent control cycles.

[0219] In some embodiments, when the number of valid cells in the candidate cell set is odd, the remaining unpaired individual cells remain unbalanced in the current control cycle, do not participate in any balancing action, and automatically enter the next control cycle to re-participate in the calculation and evaluation of the candidate cell set.

[0220] Thus, this embodiment can not only achieve single-path equalization mode, but also multi-path parallel active equalization. By simultaneously performing energy transfer between multiple pairs of cells, it can accelerate the convergence speed of state of charge consistency and aging consistency within the battery pack, reducing the total number of control cycles required to achieve the equalization target. Simultaneously, through the dual constraints of the minimum equalization benefit threshold Δλmin and the parallel equalization capacity M, it effectively avoids the decrease in benefit, circulating current risk, and increased control complexity caused by an excessive number of parallel paths, achieving a reasonable balance between equalization efficiency and system safety.

[0221] In some embodiments, parallel balancing pairs should be isolated by hardware channels, or a time-division PWM method should be used to avoid mutual coupling of current paths. Each channel is isolated by hardware topology, and the current paths between channels do not interfere with each other. When the number of balancing channels in the energy storage system is limited or complete hardware isolation cannot be achieved, a time-division pulse width modulation method is used, and only one balancing channel is activated in each time slice, thereby avoiding the superposition and coupling of multiple balancing currents on the common bus and causing circulating current.

[0222] In some embodiments, before performing multiple pairs of parallel balancing, the battery management system accumulates the balancing current and balancing power of all balancing pairs to be executed, and compares them with the maximum allowable current of the balancing circuit and the maximum allowable power of the bus, respectively. Only when the sum does not exceed the allowable limit is all parallel balancing pairs allowed to be executed simultaneously. If the sum exceeds the allowable limit, the number of balancing pairs is reduced in descending order of the attenuation deviation difference until the total current and total power are restored to the allowable range.

[0223] In some embodiments, the battery management system continuously monitors the operating status of each equalization channel during parallel equalization execution. If a direction conflict, current abnormality, insufficient heat margin, or bus power abnormality is detected in a certain parallel channel, the channel is immediately shut down. When the number of abnormal channels exceeds a preset fault tolerance threshold, all parallel equalization channels are terminated. The system adopts the single-pair equalization mode in the basic implementation to continue performing the equalization task in the lowest-risk manner, ensuring system safety.

[0224] This helps to constrain the circulating current risk of multiple parallel equalization pairs, avoids current coupling, circulating current loss and control conflicts between multiple equalization pairs, and improves the equalization safety and reliability in parallel mode.

[0225] It should be noted that the single-pair balancing implementation method in step S1401 and the multi-pair parallel balancing implementation methods in steps S140a and S140b can be selected and switched based on the hardware configuration and control requirements of the energy storage system.

[0226] In some embodiments, in step S150, after performing the active balancing action, the battery management system updates the first balancing available amount and the second balancing available amount of each cell respectively.

[0227] For the donor cells within this control cycle, from the first equalization available quota The available capacity of the donor cell is deducted from the total available capacity. The available capacity is determined by multiplying the actual charge transferred by the donor cell by a preset first consumption coefficient. Since the donor cell undergoes a discharge process due to energy output, its internal active materials experience corresponding delithiation or oxidation stress, and Joule heat accumulation leads to a temperature increase. Therefore, its available capacity as a donor cell needs to be reduced accordingly.

[0228] In this embodiment, when the first When a battery cell outputs energy as a donor cell in the current control cycle, the first equalization available quota is updated as follows:

[0229] .

[0230] For the first The first equalization available quota for each cell before active equalization is performed; To balance the current; To balance the duration; This refers to the rated capacity of the battery cell. This is the upper limit of the first level of available credit. This is a limiting function used to ensure that the updated first equalization available quota is within a certain range. interval; The first coefficient of recovery; This is the first consumption coefficient.

[0231] For the acceptor cell within this control cycle, the corresponding quota consumption for this period is deducted from the second equalization available quota. The quota consumption is determined by multiplying the actual charge transferred by the acceptor cell in this period by the preset second consumption coefficient. Since the acceptor cell undergoes a charging process due to receiving energy, its internal active materials experience corresponding lithium intercalation or reduction reaction stress, and Joule heat accumulation also occurs; therefore, its available quota as an acceptor also needs to be deducted accordingly.

[0232] In this embodiment, when the first When a cell receives energy as a recipient cell in the current control cycle, the available second equalization allowance is updated as follows:

[0233] .

[0234] For the first The second equalization quota available for each cell before active equalization is performed; To balance the current; To balance the duration; This refers to the rated capacity of the battery cell. This is the upper limit of the second-balanced available credit limit; This is a limiting function used to ensure that the updated second equalization available quota is within a certain range. interval; The second coefficient of recovery; This is the second consumption coefficient.

[0235] For cells that do not participate in any balancing action and are in a static state during this control cycle, the battery management system does not deduct any credit consumption from them. Instead, it gradually increases the first and second available balancing credits according to their respective preset first and second recovery rates to characterize the polarization recovery voltage obtained by the cells during the static period due to natural cooling and polarization dissipation.

[0236] In some embodiments, the initial values ​​of the first balanced available credit limit and the second balanced available credit limit are the same, both equal to the preset credit limit limit. For example, the credit limit. It can be set to 100. However, the consumption coefficients and recovery rates of the two are set independently and do not affect each other.

[0237] Furthermore, the first consumption coefficient Second consumption coefficient It is not a fixed constant, but a coefficient that is dynamically adjusted according to the current operating state of the cell (including temperature, state of charge, internal resistance and polarization state) so that the consumption rate of the balanced available capacity matches the actual aging stress and thermal risk.

[0238] For the donor cell, the first consumption factor for: .

[0239] For the acceptor cell, the second consumption factor for: .

[0240] The reference consumption amplification factor refers to the base value of the consumption amplification factor under standard operating conditions. , , The weighting coefficients for risk factors; This is a temperature risk function; For low SOC region risk function; For high SOC region risk function; It is the internal resistance / polarization amplification function.

[0241] , , , All can use a normalized risk function, whose output range is [0, 1].

[0242] In a preferred embodiment, the temperature risk function The temperature is segmented based on the current temperature of the battery cell and a preset temperature threshold. For example, when the battery cell temperature is below a first temperature threshold (e.g., 35°C), =0 indicates that the thermal risk is negligible within this temperature range and will not amplify the credit consumption; when the cell temperature is higher than the second temperature threshold (e.g., 50℃), =1 indicates a high thermal risk within this temperature range; when the cell temperature is between the first and second temperature thresholds... It increases linearly with temperature.

[0243] In a preferred embodiment, the risk function of the high SOC region A larger value is used when the state of charge (SOC) is above a preset high threshold (e.g., 85%), and a smaller value is used in the low SOC region. This is because when the cell is charging as a receiver at a high SOC, the anode potential may be close to or below the lithium plating potential, making it very easy for lithium plating side reactions to occur. At the same time, the electrolyte oxidation reaction is intensified under the high voltage platform, causing irreversible damage to the cell's lifespan.

[0244] In a preferred embodiment, the risk function in the low SOC region A larger value is used when the state of charge is below a preset low SOC threshold (e.g., 30%), and a smaller value is used in the high SOC region. This is because when the cell is discharged as a donor under a low state of charge, its terminal voltage is close to the discharge cutoff voltage, the internal resistance increases significantly, and the polarization effect intensifies. Continuing to discharge with a large current will easily cause the voltage to drop below the lower limit, and at the same time cause irreversible capacity loss to the cell.

[0245] In a preferred embodiment, the internal resistance / polarization amplification function It increases monotonically as the current DC internal resistance of the battery cell increases.

[0246] It should be noted that the aforementioned high SOC threshold, low SOC threshold, and temperature threshold can be adjusted according to the electrochemical system of the battery cell (such as lithium iron phosphate, ternary lithium, lithium titanate, etc.) in actual engineering applications.

[0247] Thus, the first consumption coefficient Second consumption coefficient Related to temperature, state of charge, and internal resistance, it achieves dynamic matching between the rate of charge consumption and the actual aging stress. Under high-risk operating conditions such as high temperature, high SOC reception, low SOC output, or high internal resistance, the rate of charge consumption automatically increases, allowing the battery cell to enter the rest and protection state more quickly, and avoiding the accumulation of excessive balancing load under adverse operating conditions.

[0248] In some embodiments, , , , It adopts a piecewise linear form.

[0249] In other embodiments, , , , Alternatively, the Logistic function (S-curve), exponential function, lookup table function, or function obtained through experimental calibration can be used.

[0250] In some embodiments, the first recovery coefficient Second coefficient of recovery Used to control the rate at which the available balance of a battery cell recovers during periods when it is not participating in the balancing process. In some implementations, the first recovery coefficient... Second coefficient of recovery It can be set to a fixed value; in other embodiments, the first recovery coefficient Second coefficient of recovery It is related to the cell's resting state, thermal margin, and degree of polarization recovery.

[0251] In this embodiment, the coefficient of recovery .

[0252] The maximum recovery coefficient; This is the heat recovery function; It is the polarization recovery function; This serves as a participation status identifier. Among them, This is the heat reserve.

[0253] Participation status identifier Indicates whether the i-th cell participates in the balancing process in the current control cycle: if it participates in the balancing process, The recovery term can be reduced or set to zero; if it is not involved in balancing Available credit will be restored over time.

[0254] In a preferred embodiment, the heat recovery function is:

[0255] ;

[0256] in, This is the minimum heat margin threshold. This is the safety margin threshold.

[0257] In a preferred embodiment, a relative internal resistance index is first defined:

[0258] ;

[0259] The polarization recovery function is:

[0260] ;

[0261] in, For low polarization threshold, This represents the high polarization threshold.

[0262] For example, Desirable , Desirable , 0.05 is acceptable. 0.30 is acceptable.

[0263] The above values ​​can be calibrated or corrected online based on cell system, thermal design, equalization current, and aging test data.

[0264] It should be noted that the above values ​​are only exemplary values. In actual engineering applications, the above thresholds can be calibrated or corrected based on the cell system (such as lithium iron phosphate, ternary lithium, lithium titanate, etc.), thermal design (such as heat dissipation conditions, air duct layout), equalization current amplitude, and aging test data.

[0265] In a preferred embodiment, the first recovery coefficient .

[0266] Second recovery coefficient .

[0267] in, This indicates whether the i-th cell participates in the balancing process as a donor during the current control cycle. This indicates whether the i-th cell participates in the equilibrium process as a receptor.

[0268] In some embodiments, in step S130 above, when the battery management system screens the candidate set of battery cells according to the available balance quota, it also adopts a hysteresis rule to avoid the battery cells frequently entering and leaving the candidate set due to small fluctuations in the available balance quota near the threshold, thereby causing frequent switching of the balancing channel and control instability.

[0269] The battery management system sets different thresholds for cells to enter and exit the candidate set. When the balanced available capacity of a cell falls below the lockout threshold... When the battery cell is removed from the candidate set, it enters a mandatory rest period; when the balanced available amount of the battery cell recovers to above the release threshold... Only when the cell is in this condition can it re-enter the candidate set. Among these, Through the aforementioned hysteresis rule, a hysteresis band is formed between the locking threshold and the releasing threshold. When the balanced available amount of the battery cell fluctuates within this hysteresis band, its candidate qualification status remains unchanged, thereby effectively avoiding frequent switching of the equalization channel and system oscillation caused by small fluctuations in the balanced available amount.

[0270] For example, locking threshold A value of 0.10 can be used as the release threshold. A value of 0.35 is acceptable. This applies when the average available balance of the battery cells drops below the lockout threshold. At that time, the cell is removed from the candidate set; thereafter, even if the cell's balanced available capacity rises back to the locked threshold during the resting recovery process. As long as the release threshold is not reached... The cell will remain in a non-balancing state and will not re-enter the candidate set; it will only re-enter when the cell's available balancing capacity recovers to above the release threshold. Only then can the battery cell regain its eligibility to participate in the balancing process.

[0271] Through the aforementioned hysteresis rules and adaptive threshold configuration, this embodiment effectively avoids frequent switching of the equalization channel and system oscillation caused by the frequent entry and exit of cells into the candidate set due to minor fluctuations in the available equalization quota, thereby improving the stability and robustness of the control system.

[0272] In a preferred embodiment, the first minimum available threshold for the output direction is... and the second lowest available threshold in the receiving direction It can be set based on the normalized balanced available credit limit range. Both the first and second balanced available credit limits are normalized to the [0,1] range. , The value can range from 0.15 to 0.40, preferably from 0.25 to 0.35, and can be 0.25 as an example.

[0273] Because the risks and aging mechanisms of battery cells differ when they act as donors and acceptors. and It can also be set separately according to the working conditions.

[0274] In a preferred embodiment, at the end of the charging process, the receiving cell is more likely to enter a high-charge state, high-voltage, and high-temperature region. When the cell is charging as a receiver, its anode potential may be close to or lower than the lithium plating potential. Under the high-voltage plateau, the electrolyte oxidation side reaction intensifies, causing irreversible damage to the cell's lifespan. Therefore, at the end of the charging process, a [further details are needed]. Greater than This involves increasing the requirements for battery cells in the receiving direction, requiring cells to have a higher available capacity in that direction to participate in balancing, thereby strengthening protection against the risks of high-SOC charging. For example, a setting can be made at the charging end... =0.30, =0.20.

[0275] In another preferred embodiment, at the end of the discharge process, the output cell (donor cell) is more likely to enter a low-charge state, low-voltage, and high-polarization region. At this point, when the cell discharges as a donor, its terminal voltage is close to the discharge cutoff voltage, its internal resistance increases significantly, and the polarization effect intensifies. Continuing to discharge will easily cause the voltage to drop below the lower limit, resulting in irreversible capacity loss for the cell. Therefore, at the end of the discharge process, a [further details are needed]. Greater than This means increasing the requirements for the battery cells in the output direction, requiring a higher available capacity for each cell to participate in balancing, thereby strengthening protection against the risk of low SOC discharge. For example, a setting can be made at the discharge end... =0.30, =0.20.

[0276] In some embodiments, step S120 above, determining when the energy storage terminal meets the first triggering condition and enters the first equalization mode based on the current operating status information of multiple battery cells, includes:

[0277] Step S121: Calculate the charge dispersion of multiple cells based on their state of charge, and calculate the aging dispersion of multiple cells based on their health status.

[0278] Among them, charge dispersion Where SOCmax is the maximum value of the state of charge (SOC) among all cells, and SOCmin is the minimum value of the state of charge (SOC) among all cells.

[0279] Aging dispersion Where SOHmax is the maximum value of the health status among all cells, SOHmin is the minimum value of the health status among all cells, and aging dispersion is used to measure the health difference between the cell with the strongest health status and the cell with the weakest health status.

[0280] Step S122: When the charge dispersion is less than or equal to the first preset threshold and the aging dispersion is greater than the second preset threshold, it is determined that the energy storage system meets the first triggering condition.

[0281] The first preset threshold is a preset state-of-charge dispersion threshold, used to determine whether the state of charge within the battery pack is severely unbalanced. For example, the first preset threshold can be 5%.

[0282] When the second preset threshold is a preset aging dispersion threshold, it is used to determine whether the aging degree within the battery pack has become severely unbalanced. For example, the second preset threshold can be 3%.

[0283] The battery management system determines that the energy storage system meets the first trigger condition, enters the first equalization mode, and executes the aging consistency active equalization control logic described in steps S130 to S150 above, so as to realize the aging consistency management of multiple cells throughout the entire life cycle.

[0284] In some embodiments, such as Figure 7 As shown, the method further includes step S210: when the charge dispersion is greater than a first preset threshold, a second balancing mode is entered to balance the charge states of multiple cells. The second balancing mode is the basic capacity maintenance mode. In the second balancing mode, the battery management system balances the charge states of multiple cells, using cells with higher charge states as donors and cells with lower charge states as acceptors, controlling the transfer of energy from donors to acceptors to quickly eliminate extreme voltage differences, prevent overcharging or over-discharging of individual cells, and prioritize maximizing the current available capacity of the battery pack. In the second balancing mode, the system bypasses or temporarily suspends the execution of the first balancing mode.

[0285] In some embodiments, the method further includes: when the current operating status information of multiple cells does not meet either the first balancing mode or the second balancing mode, entering a silent mode. That is, if the charge dispersion ΔSOCrange does not exceed the first preset threshold and the aging dispersion Daging does not exceed the second preset threshold, the battery management system determines that the current battery pack is in good condition, and no balancing intervention is required, maintaining silent standby without performing any balancing actions.

[0286] In some embodiments, such as Figure 7 As shown, in the second equalization mode, the following steps are performed to equalize the charges of multiple cells:

[0287] Step S220: Calculate the reference state of charge based on the state of charge of multiple cells.

[0288] In this embodiment, the battery management system calculates the reference value of the battery pack. : .

[0289] Where N is the total number of battery cells, and SOCi is the state of charge of the i-th battery cell. (Reference State of Charge) It characterizes the overall average charge level of the battery pack, serving as a benchmark value for judging whether the state of charge of each cell is too high or too low.

[0290] Step S230: Compare the state of charge of multiple cells with the reference state of charge to obtain the state of charge deviation of multiple cells.

[0291] The battery management system calculates the state-of-charge deviation of each cell. , .

[0292] in, This indicates that the state of charge of the battery cell is higher than the reference level within the group, making it suitable as an energy output (donor). This indicates that the cell's state of charge is lower than the group's reference level, making it suitable as an energy receiver (acceptor).

[0293] Step S240: Based on the state of charge deviation of multiple cells, construct a second set of output candidate cells and a second set of receiving candidate cells respectively.

[0294] Battery management system build output second output candidate set , .

[0295] The state of charge deviation is significantly higher than the preset output direction SOC difference threshold. And the first equalization available credit limit Meet the first minimum available threshold The battery cells can be included in the second output candidate set as energy output sources.

[0296] The battery management system constructs and outputs the second receiver candidate set. , .

[0297] The state of charge deviation is significantly lower than the preset SOC difference threshold in the receiving direction. And the second equilibrium available credit limit Meet the second minimum available threshold The battery cells can be included in the second set of receiving candidates as energy receivers.

[0298] In this embodiment, the second balancing mode also uses the superimposed balancing available quota as a constraint to prevent cells with insufficient balancing available quota from continuing to participate in balancing.

[0299] Step S250: Pair the cells in the second output candidate cell set with the cells in the second receiving candidate cell set, and control the paired cells to perform equalization.

[0300] The battery management system will use the second output candidate set. The cells in the middle are classified according to the state of charge deviation. Sort the second receiving candidate set in descending order from largest to smallest. The battery cells in the middle are according to Sort the data in ascending order from smallest to largest. The battery management system prioritizes the second output candidate set. The highest-performing battery cell and two receiver candidate sets between China and the Netherlands Pairing cells with the lowest state of charge transfers energy from the high-charge cells to the low-charge cells, thereby quickly reducing the difference in state of charge between the cells.

[0301] Under the conditions of satisfying the constraints of the number of hardware channels, the minimum SOC difference, and the equalization of available capacity, the battery management system can further pair cells with the second highest state of charge with cells with the second lowest state of charge to achieve multiple pairs of parallel peak shaving and valley filling, so as to accelerate the consistency convergence speed.

[0302] For any candidate pairing (p, q), where p is the donor and q is the recipient, only when... Only then will the balancing action be performed. Among these, The preset minimum SOC difference for pairing cells. If the SOC difference of a pair of cells is lower than... If the candidate pairing is deemed to have insufficient equilibrium benefit, then no equilibrium action will be performed to avoid ineffective energy transport and additional heat burden.

[0303] In some embodiments, in the second balancing mode, after balancing based on the state of charge of multiple cells, step S260 is further performed: updating the balancing available quota for each cell.

[0304] In this embodiment, the implementation of step S260 is the same as that of step S150 in the above embodiment, and will not be repeated.

[0305] In some embodiments, during the execution of the first balancing mode or the second balancing mode, the battery management system monitors the balancing status in real time, and terminates the current balancing operation when any of the following termination conditions are met:

[0306] (1) The SOC difference between the donor cell and the acceptor cell is lower than the termination threshold: .in, This is the preset termination threshold.

[0307] (2) The available balance of the donor cell or the recipient cell is lower than the locking threshold, that is, the available balance has been exhausted and a forced rest is required.

[0308] (3) Any cell triggers voltage protection, temperature protection, thermal margin protection or current protection, that is, the cell's terminal voltage, surface temperature or equalization current exceeds the safe operating range.

[0309] (4) When the maximum duration of a single balancing operation is reached, that is, the execution time of this balancing action has reached the preset upper limit, it is necessary to pause to prevent heat accumulation caused by long-term continuous balancing.

[0310] (5) The equilibrium benefit is lower than the minimum benefit threshold, meaning that the SOC consistency improvement obtained by continuing to perform equilibrium is insufficient to offset the energy conversion loss and aging cost.

[0311] When any of the above termination conditions are met, the battery management system immediately shuts down the equalization channel, stops energy transfer, and enters the state monitoring and mode arbitration of the next control cycle.

[0312] It is understood that the second equalization mode can serve as an alternative to the first equalization mode, as it is simpler to operate and has lower implementation costs. The battery management system can switch between the two strategies based on system state, model reliability, and control resources. For example, when the system is under normal operating conditions and the model parameters have been calibrated, the battery management system prioritizes the first equalization mode; when the system is under conditions with limited computing resources, or when running on a low-cost hardware platform, the battery management system switches to the second equalization mode, which reliably achieves basic state-of-charge equalization with lower computational overhead.

[0313] In one embodiment, this embodiment provides a balancing method for an energy storage system. The energy storage system includes multiple battery cells, and the multiple battery cells are connected in series or parallel to form a battery pack. The balancing method for the energy storage system is executed by a terminal of the energy storage system, which can be the battery management system of the energy storage system; such as Figure 8 As shown, the energy storage system balancing method includes the following steps:

[0314] Step S100: Collect the current operating status information of multiple battery cells, and calculate the charge dispersion and aging dispersion of multiple battery cells based on the current operating status information of multiple battery cells.

[0315] The battery management system (BMS) collects the terminal voltage, charging / discharging current, and surface temperature of each cell according to a preset sampling period using a voltage sampling circuit, a current Hall sensor, and a temperature sensor attached to the surface of each cell. Based on the collected voltage and current, the BMS estimates the current state of charge (SOCi) and state of health (SOHi) of each cell online.

[0316] Step S200: Based on the charge dispersion and aging dispersion of multiple cells, match the corresponding mode for the energy storage system.

[0317] Step S300: When the charge dispersion is greater than the first preset threshold, enter the second equalization mode and perform equalization based on the state of charge of multiple cells. Execute steps S220-S260 in the above embodiment.

[0318] Step S400: When the charge dispersion is less than or equal to the first preset threshold and the aging dispersion is greater than the second preset threshold, it is determined that the energy storage system meets the first triggering condition and enters the first equalization mode. Steps S130-S150 in the above embodiments are executed.

[0319] Step S500: When the charge dispersion and aging dispersion of multiple cells do not meet either the first equalization mode or the second equalization mode, the system enters a silent mode. That is, if the charge dispersion ΔSOCrange does not exceed the first preset threshold and the aging dispersion Daging does not exceed the second preset threshold, the battery management system determines that the current battery pack is in good condition and does not require equalization intervention, maintaining silent standby without performing any equalization actions.

[0320] This application employs a tiered arbitration system based on the charge dispersion and aging dispersion of multiple battery cells to match corresponding modes for the energy storage system. When the battery pack is operating under conditions of severely inconsistent state of charge, it prioritizes entering the second equalization mode, employing a peak-shaving and valley-filling strategy based on the difference in state of charge to quickly eliminate voltage drop. When the consistency of state of charge is within a controllable range but aging differences have become prominent, it switches to the first equalization mode, intervening in the aging process through thermal reliability screening, equalization of available capacity, and degradation deviation. This addresses both the urgent need for capacity under new battery conditions or abnormal operating conditions and the lifespan bottleneck in long-term operation. The tiered arbitration achieves adaptive equalization under all operating conditions, which is beneficial for coordinating short-term operational safety and improving the economic efficiency throughout the entire life cycle.

[0321] This application introduces a balance availability limit in the first equalization mode. Each time a cell participates in a equalization operation, it consumes a corresponding balance availability limit based on the amount of charge transferred. Cells whose balance availability limit is exhausted are forcibly removed from the candidate cell set and enter a rest period. During the rest period, the balance availability limit gradually recovers at a rate related to thermal recovery and polarization dissipation. Through this dynamic balance of balance availability consumption and recovery, the problem of cells in good health being over-consumed and degraded due to long-term balance throughput tasks is prevented. Therefore, balance throughput achieves fair rotation throughout its entire lifespan, thereby suppressing the Matthew effect.

[0322] Secondly, this application provides an energy storage system, which includes multiple battery cells; such as Figure 9 As shown, the energy storage system also includes:

[0323] The acquisition module 601 is used to acquire the current operating status information of multiple battery cells;

[0324] Arbitration module 602 is used to determine, based on the current operating status information of multiple cells, when the energy storage system meets the first trigger condition, to enter the first equalization mode;

[0325] The first screening module 603 is used to evaluate multiple battery cells based on their current operating status information, screen out battery cells that meet the thermal reliability conditions and equalization participation conditions, and construct a candidate battery cell set.

[0326] The first equalization module 604 is used to calculate the attenuation deviation of the candidate cells based on the health status and equalization available quota of the candidate cells in the candidate cell set, determine at least one pair of equalization cell cells according to the ranking of attenuation deviation, and control the donor cell in the at least one pair of equalization cell cells to perform active equalization action to the recipient cell.

[0327] In some embodiments, the current operating status information of the battery cell includes the state of charge and the health status.

[0328] The first screening module 603 determines the predicted temperature of the multiple cells after balancing based on the current operating status information of the multiple cells and the preset balancing current, and determines the current balancing available quota of the multiple cells based on the historical balancing participation data of the multiple cells; and constructs a candidate cell set by selecting cells whose predicted temperature is lower than the preset safe temperature threshold and whose balancing available quota is higher than the balancing participation benchmark value.

[0329] In some embodiments, the current operating status information of the battery cell also includes the surface temperature of the battery cell.

[0330] The first screening module 603 includes a thermal reliability screening unit. The thermal reliability screening unit is used to calculate the predicted temperature of multiple cells after performing active balancing based on the surface temperature, operating environment temperature and preset balancing current of multiple cells and a thermal reliability model. Cells whose predicted temperature is lower than the preset safe temperature threshold are determined to meet the thermal reliability conditions.

[0331] In some embodiments, the thermal reliability model calculates the temperature rise attenuation of the battery cell during the equalization period based on the cell's surface temperature, ambient operating temperature, preset equalization time, and thermal time constant; calculates the cumulative temperature rise of the battery cell during the equalization period based on the preset equalization current, the cell's DC internal resistance, and equivalent thermal resistance; and obtains the predicted temperature by superimposing the ambient operating temperature, temperature rise attenuation, and cumulative temperature rise.

[0332] In some embodiments, the first screening module 603 further includes a balance participation condition screening unit, which is used to predict the participation consumption value of multiple cells after performing active balancing actions based on the balance available quota of multiple cells; compare the balance available quota and participation consumption value of multiple cells respectively, and determine that the cells whose balance available quota is greater than or equal to the participation consumption value meet the balance participation condition.

[0333] In some embodiments, candidate cells include basic candidate cells and restricted candidate cells; the balanced available quota includes a disabled interval, a restricted interval, and an available interval.

[0334] The first screening module 603 includes battery cells with available balance quota in the available range as basic candidate battery cells in the candidate battery cell set; includes battery cells with available balance quota in the restricted range as restricted candidate battery cells in the candidate battery cell set; excludes battery cells with available balance quota in the disabled range from the candidate battery cell set; if a restricted candidate battery cell participates in the active balancing action, the first screening module 603 sets the balancing current of the restricted candidate battery cell to be less than the balancing current of the basic candidate battery cell.

[0335] In some embodiments, the first equalization module 604 includes an attenuation deviation calculation unit, which is used to calculate the average health status of the candidate cell set based on the health status of at least one candidate cell in the candidate cell set; and to calculate the attenuation deviation of the candidate cell based on the average health status, the health status of the candidate cell, and the available equalization quota, using an equalization tendency function; wherein the attenuation deviation is used to characterize the priority of the candidate cell as a donor cell or as a recipient cell, so that the difference in health status between multiple cells is reduced as the active equalization action is executed.

[0336] In some embodiments, the equilibrium tendency function determines the attenuation deviation of a candidate cell based on the degree of deviation of the candidate cell's health status from the mean of its health status and the remaining proportion of the candidate cell's equilibrium available capacity relative to the total available capacity.

[0337] In some embodiments, the equalization available quota includes a first equalization available quota and a second equalization available quota. The first equalization available quota is used to characterize the degree of equalization participation of the battery cell as a donor battery cell, and the second equalization available quota is used to characterize the degree of equalization participation of the battery cell as a recipient battery cell.

[0338] The first screening module 603 obtains the first and second balanced available quotas of multiple battery cells respectively; it screens the multiple battery cells according to the first balanced available quotas and includes the battery cells that meet the first output balancing condition into the first output candidate set; it screens the multiple battery cells according to the second balanced available quotas and includes the battery cells that meet the first receiving balancing condition into the first receiving candidate set; and it determines the candidate battery cell set according to the first output candidate set and the first receiving candidate set.

[0339] In some embodiments, the first equalization module 604 uses the candidate cell with the largest concentration attenuation deviation as the donor cell and the candidate cell with the smallest attenuation deviation as the recipient cell to form at least one pair of equalization cells.

[0340] In some embodiments, the first equalization module 604 generates an output candidate sequence based on the sorting of attenuation deviation from large to small, and generates a receiving candidate sequence based on the sorting of attenuation deviation from small to large; based on parallel constraints, the output candidate sequence is paired with candidate cells in the receiving candidate sequence that have the same sorting position and an attenuation deviation difference greater than or equal to a preset threshold, to form at least one pair of equalized cell pairs.

[0341] In some embodiments, the parallel constraints include parallel balancing capacity; the parallel balancing capacity is determined based on the available balancing resources of the energy storage system and the number of candidate cells in the candidate cell set; when the output candidate sequence is paired with the received candidate sequence, an upper limit for the number of pairs is set according to the parallel balancing capacity; the upper limit for the number of pairs is not greater than the parallel balancing capacity.

[0342] In some embodiments, the arbitration module calculates the charge dispersion of multiple cells based on their state of charge and calculates the aging dispersion of multiple cells based on their health status. When the charge dispersion is less than or equal to a first preset threshold and the aging dispersion is greater than a second preset threshold, the arbitration module determines that the energy storage system meets the first triggering condition.

[0343] In some embodiments, the energy storage system further includes a second balancing module. When the charge dispersion is greater than a first preset threshold, the arbitration module controls the energy storage system to enter a second balancing mode and invokes the second balancing module.

[0344] The second equalization module calculates a reference state of charge (SOC) based on the SOC of multiple battery cells; compares the SOC of multiple battery cells with the reference SOC to obtain the SOC deviation of the multiple battery cells; constructs a second output candidate battery cell set and a second receiving candidate battery cell set based on the SOC deviation of the multiple battery cells; pairs the battery cells in the second output candidate battery cell set with the battery cells in the second receiving candidate battery cell set, and controls the paired battery cells to perform equalization actions.

[0345] In some embodiments, the energy storage system further includes a quiescent control module. When the charge dispersion is less than or equal to the first preset threshold and the aging dispersion is less than or equal to the second preset threshold, the arbitration module controls the energy storage system to enter a quiescent mode and invokes the quiescent control module. The quiescent control module controls the energy storage system to not perform any balancing actions and remain quiescent.

[0346] In one exemplary embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 10As shown, the computer device includes a processor, memory, input / output interfaces, a communication interface, a display unit, and input devices. The processor, memory, and input / output interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the input / output interfaces. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The input / output interfaces are used for exchanging information between the processor and external devices. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, Near Field Communication (NFC), or other technologies. When the computer program is executed by the processor, it implements a method for balancing an energy storage system.

[0347] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, database, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0348] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0349] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for balancing an energy storage system, characterized in that, The energy storage system includes multiple battery cells; the method includes: Collect the current operating status information of the multiple battery cells; Based on the current operating status information of the multiple battery cells, when the energy storage system meets the first trigger condition, it enters the first equalization mode; Based on the current operating status information of the multiple battery cells, the multiple battery cells are evaluated, and battery cells that meet the thermal reliability conditions and equalization participation conditions are selected to construct a candidate battery cell set; Based on the health status and available balance of the candidate cells in the candidate cell set, the attenuation deviation of the candidate cells is calculated. At least one pair of equalizing cells is determined according to the order of the attenuation deviation, and the donor cell in the at least one pair of equalizing cells is controlled to perform an active equalization action to the recipient cell.

2. The energy storage system balancing method according to claim 1, characterized in that, The current operating status information of the battery cell includes its state of charge and health status; based on the current operating status information of the multiple battery cells, the multiple battery cells are evaluated to select those that meet the thermal reliability conditions and equalization participation conditions, and a candidate battery cell set is constructed, including: Based on the current operating status information of the multiple battery cells and the preset balancing current, the predicted temperature after balancing of the multiple battery cells is determined, and based on the historical balancing participation data of the multiple battery cells, the current available balancing quota of the multiple battery cells is determined. The candidate cell set is constructed by using cells whose predicted temperature is lower than a preset safe temperature threshold and whose available balance is higher than the balance participation benchmark value. The equilibrium participation benchmark value is the participation consumption value for performing the current equilibrium action.

3. The energy storage system balancing method according to claim 2, characterized in that, The current operating status information of the battery cell also includes the surface temperature of the battery cell; the evaluation of the multiple battery cells to select those that meet the thermal reliability and equalization participation conditions includes: Based on the surface temperature of the multiple battery cells, the ambient operating temperature, and the preset balancing current, the predicted temperature of the multiple battery cells after performing active balancing is calculated using a thermal reliability model. A battery cell whose predicted temperature is lower than the preset safe temperature threshold is determined to meet the thermal reliability condition.

4. The energy storage system balancing method according to claim 3, characterized in that, The thermal reliability model calculates the temperature rise decay of the battery cell during the equalization period based on the surface temperature of the battery cell, the operating environment temperature, the preset equalization time, and the thermal time constant. Based on the preset equalization current, the DC internal resistance and equivalent thermal resistance of the battery cell, the cumulative temperature rise of the battery cell during the equalization period is calculated. The predicted temperature is obtained by superimposing the ambient temperature, the temperature rise attenuation, and the temperature rise accumulation.

5. The energy storage system balancing method according to claim 3, characterized in that, The evaluation of the plurality of battery cells, and the selection of cells that meet the thermal reliability and equalization participation conditions, includes: Based on the balanced available amount of the multiple battery cells, predict the participation consumption value after the multiple battery cells perform the active balancing action; The balanced available amount of the multiple battery cells is compared with the participation consumption value. The battery cells whose balanced available amount is greater than or equal to the participation consumption value are determined to meet the balanced participation condition.

6. The energy storage system balancing method according to claim 5, characterized in that, The candidate battery cells include basic candidate battery cells and restricted candidate battery cells; the balanced available quota includes a disabled interval, a restricted interval, and an available interval. The battery cells whose balanced available quota is within the available range are included as the basic candidate battery cells in the candidate battery cell set; The battery cells whose balanced available quota is within the restricted usage range are included in the candidate battery cell set as the restricted usage candidate battery cells; Cells whose balanced available quota is in the disabled range are excluded from the candidate cell set; The method further includes: if the restricted candidate cell participates in the active balancing action, setting the balancing current of the restricted candidate cell to be less than the balancing current of the basic candidate cell.

7. The energy storage system balancing method according to claim 1, characterized in that, The step of calculating the attenuation deviation of the candidate cells based on the health status and balanced available quota of the candidate cells in the candidate cell set includes: Calculate the average health status of the candidate battery cell set based on the health status of at least one candidate battery cell in the candidate battery cell set; Based on the average health status, the health status and balanced available quota of the candidate cells, the attenuation deviation of the candidate cells is calculated using the balanced tendency function. The attenuation deviation is used to characterize the priority of the candidate cell as the donor cell or the recipient cell, so that the health status difference between the multiple cells is reduced as the active balancing action is performed.

8. The energy storage system balancing method according to claim 7, characterized in that, The equalization tendency function determines the attenuation deviation of the candidate battery cell based on the degree of deviation of the health status of the candidate battery cell from the mean of the health status, and the remaining proportion of the equalization available quota of the candidate battery cell relative to the total quota capacity.

9. The balancing method for an energy storage system according to any one of claims 1, 2, 5 or 7, characterized in that, The available balance quota includes a first available balance quota and a second available balance quota. The first available balance quota characterizes the degree of balance participation of the battery cell as the donor battery cell, and the second available balance quota characterizes the degree of balance participation of the battery cell as the recipient battery cell. The evaluation of the plurality of battery cells to select those that meet the thermal reliability and balance participation conditions includes: The first and second balanced available quotas of the plurality of battery cells are obtained respectively; The multiple battery cells are screened based on the first equalization available quota of the multiple battery cells, and the battery cells that meet the first output equalization condition are included in the first output candidate set; The multiple battery cells are screened according to the second equalization available quota of the multiple battery cells, and the battery cells that meet the first receiving equalization condition are included in the first receiving candidate set; The candidate cell set is determined based on the first output candidate set and the first received candidate set.

10. The energy storage system balancing method according to any one of claims 1, 2, or 7, characterized in that, The step of determining at least one pair of equalizing cells based on the sorting of attenuation deviation, and controlling the donor cell in at least one pair of equalizing cells to perform an active equalization action on the recipient cell, includes: The candidate cell with the largest attenuation deviation in the candidate cell set is used as the donor cell, and the candidate cell with the smallest attenuation deviation is used as the recipient cell, to form at least one pair of balanced cells.

11. The energy storage system balancing method according to any one of claims 1, 2, or 7, characterized in that, The step of determining at least one pair of equalizing cells based on the ranking of the attenuation deviation, and the step of evaluating the plurality of cells to select cells that meet the thermal reliability and equalization participation conditions, includes: An output candidate sequence is generated by sorting the attenuation deviations from largest to smallest, and a receiving candidate sequence is generated by sorting the attenuation deviations from smallest to largest. Based on parallel constraints, the output candidate sequence is paired with the candidate cells in the received candidate sequence that have the same sorting position and whose attenuation deviation difference is greater than or equal to a preset threshold, to form at least one pair of balanced cells.

12. The energy storage system balancing method according to claim 11, characterized in that, The parallel constraints include parallel balancing capacity; the parallel balancing capacity is determined based on the available balancing resources of the energy storage system and the number of candidate cells in the candidate cell set; When the output candidate sequence is paired with the received candidate sequence, the upper limit of the number of pairs is set according to the parallel equalization capacity; The maximum number of pairs is not greater than the parallel balancing capacity.

13. The energy storage system balancing method according to claim 11, characterized in that, The method further includes: The charge dispersion of the multiple cells is calculated based on their state of charge, and the aging dispersion of the multiple cells is calculated based on their health status. When the charge dispersion is less than or equal to a first preset threshold and the aging dispersion is greater than a second preset threshold, the energy storage system is determined to meet the first triggering condition.

14. The energy storage system balancing method according to claim 13, characterized in that, The method further includes: When the charge dispersion is greater than the first preset threshold, the system enters the second equalization mode: A reference state of charge is calculated based on the state of charge of the multiple battery cells. The state of charge (SOC) of the plurality of cells is compared with the reference SOC to obtain the SOC deviation of the plurality of cells. Based on the state of charge deviation of the multiple battery cells, a second set of output candidate battery cells and a second set of receiving candidate battery cells are constructed respectively. The cells in the second output candidate cell set are paired with the cells in the second receiving candidate cell set, and the paired cells are controlled to perform equalization operations.

15. An energy storage system, characterized in that, The energy storage system includes multiple battery cells; the energy storage system also includes: The data acquisition module is used to collect the current operating status information of the multiple battery cells; The arbitration module is used to determine, based on the current operating status information of the multiple battery cells, when the energy storage system meets the first trigger condition, to enter the first equalization mode; The first screening module is used to evaluate the multiple battery cells based on their current operating status information, screen out the battery cells that meet the thermal reliability conditions and the equalization participation conditions, and construct a candidate battery cell set. The first equalization module is used to calculate the attenuation deviation of the candidate cells based on the health status and equalization available quota of the candidate cells in the candidate cell set, determine at least one pair of equalization cell pairs based on the ranking of the attenuation deviation, and control the donor cell in at least one pair of equalization cell pairs to perform an active equalization action to the recipient cell.

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