A Global Optimization Control Method for SOC Equalization of Series Lithium-ion Battery Packs

Abstract

This invention relates to the field of lithium battery equalization control technology, and discloses a globally optimized control method for the SOC equalization control of a series lithium battery pack. The method first allows the series lithium battery pack to perform SOC equalization management according to preset equalization parameters. Simultaneously, it initiates real-time acquisition of the state of charge (SOC) of each individual battery cell within the pack. The acquired SOC data is converted into an SOC equalization curve and then divided into intervals to obtain SOC curve segments for different equalization control stages. The equalization deviation at each stage is calculated using these curve segments. The operating status data of the series lithium battery pack is collected to determine the parameter interference degree when implementing equalization management under preset equalization parameters. The equalization adjustment amount for each stage is determined based on the equalization deviation. Finally, the equalization strategy for different equalization control stages is dynamically adjusted according to the corresponding adjustment amount. Through staged analysis and dynamic adjustment, global equalization control of the SOC of the series lithium battery pack is achieved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery equalization control technology, specifically to a global optimization control method for the SOC equalization control of a series lithium battery pack. Background Technology

[0002] In the rapid development of the new energy field, series lithium battery packs are widely used in electric vehicles, energy storage systems, and other scenarios due to their high energy density and long cycle life. However, due to slight differences in material properties and structural processes in the manufacturing of individual cells, coupled with environmental factors such as uneven temperature distribution and fluctuations in charge and discharge rates during use, the state of charge (SOC) of each individual cell in a series lithium battery pack is prone to inconsistencies.

[0003] This SOC imbalance leads to a decline in the overall performance of the battery pack, making it difficult to synchronize the depth of charge and discharge of individual cells. Some cells may age prematurely due to overcharging and over-discharging, thus shortening the lifespan of the entire battery pack. Currently, there are various methods for SOC balancing control of series lithium battery packs. Traditional balancing control strategies are mostly based on preset fixed parameters for balancing management, which can only achieve a certain degree of balancing effect under specific operating conditions.

[0004] However, in actual operation, the battery pack's operating state changes constantly, such as load fluctuations and changes in ambient temperature. Fixed-parameter balancing strategies struggle to adapt to these dynamic changes. Furthermore, existing methods often lack fine-grained segmentation of different balancing stages during the balancing control process, failing to accurately capture the changing characteristics of State of Charge (SOC) at each stage, resulting in insufficient targeting of balancing adjustments. In addition, when calculating balancing adjustment amounts, most methods only consider the degree of SOC deviation, ignoring parameter interference from operating state data, thus affecting the accuracy of balancing adjustments and hindering the achievement of efficient global balancing control. Summary of the Invention

[0005] The purpose of this invention is to provide a globally optimized control method for the SOC equalization of series lithium battery packs, in order to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides a globally optimized control method for SOC equalization control of a series lithium battery pack, the method comprising:

[0007] The series-connected lithium battery pack implements SOC equalization management based on preset equalization parameters, and simultaneously starts real-time acquisition of the state of charge of each individual cell in the battery pack.

[0008] The collected state of charge data is converted into the SOC equalization curve of the battery pack. The SOC equalization curve is divided into intervals to obtain SOC curve segments of the series lithium battery pack at different equalization control stages. The equalization deviation of each equalization control stage is calculated through the corresponding SOC curve segments.

[0009] Collect the operating status data of the series lithium battery pack, obtain the parameter interference degree when the series lithium battery pack implements balance management according to the preset balance parameters based on the operating status data, and determine the balance adjustment amount of each balance control stage according to the parameter interference degree and the corresponding balance deviation.

[0010] The balancing strategy of each balancing control stage in the series lithium battery pack is dynamically adjusted according to the corresponding balancing adjustment amount.

[0011] Preferably, preset balancing parameters are set according to the number of individual cells and nominal capacity of the series-connected lithium battery pack.

[0012] Preferably, the real-time acquisition of the state of charge of each individual cell in the battery pack is initiated by collecting the state of charge of each individual cell through voltage and current sensors integrated into the battery management system.

[0013] Preferably, converting the collected state of charge (SOC) data into the SOC equilibrium curve of the battery pack involves performing a moving average filter on the collected SOC data to obtain the SOC equilibrium curve of the battery pack.

[0014] Preferably, the SOC equilibrium curve is divided into intervals based on a preset SOC difference threshold.

[0015] Preferably, the calculation of the equilibrium deviation at each equilibrium control stage using the corresponding SOC curve segment specifically includes:

[0016] For each equilibrium control stage, extract the SOC curve segment for that stage;

[0017] Obtain the target SOC value corresponding to the preset equalization parameters in the equalization control stage;

[0018] Calculate the arithmetic mean of the SOC curve segments;

[0019] The deviation coefficient of each state of charge data point in the SOC curve segment is determined based on the arithmetic mean and the target SOC value.

[0020] The equilibrium deviation of the equilibrium control stage is calculated by using all the deviation coefficients, and then the equilibrium deviation of each equilibrium control stage is obtained.

[0021] Preferably, the operating status data of the series lithium battery pack is collected through the communication interface of the battery management system.

[0022] Preferably, determining the balance adjustment amount for each balance control stage based on the parameter disturbance degree and the corresponding balance deviation degree specifically includes:

[0023] For each equalization control stage, extract the benchmark adjustment coefficient corresponding to that stage from the preset equalization parameters;

[0024] The balance adjustment amount of the balance control stage is calculated based on the benchmark adjustment coefficient, the parameter disturbance degree, and the balance deviation degree of the balance control stage, thereby obtaining the balance adjustment amount of each balance control stage.

[0025] Preferably, dynamically adjusting the balancing strategy for each balancing control stage in the series lithium battery pack according to the corresponding balancing adjustment amount specifically includes:

[0026] For each equalization control stage in the series lithium battery pack, the actual adjustment coefficient of the stage is determined based on the benchmark adjustment coefficient corresponding to the preset equalization parameters and the equalization adjustment amount of the stage, thereby completing the dynamic adjustment of the equalization strategy for each equalization control stage in the series lithium battery pack.

[0027] Preferably, obtaining the parameter interference degree of the series lithium battery pack when implementing equalization management according to preset equalization parameters based on the operating status data specifically includes: obtaining the temperature fluctuation value and current fluctuation value in the operating status data, calculating the product of the temperature fluctuation value and current fluctuation value, and using the product as the parameter interference degree;

[0028] After determining the balance adjustment amount for each balance control stage, the balance adjustment amount is limited to the preset maximum adjustment range. If the balance adjustment amount exceeds the maximum adjustment range, the boundary value of the maximum adjustment range is used as the actual adjustment amount.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] While implementing SOC balancing management by pre-setting balancing parameters, the system simultaneously collects the state of charge (SOC) of each individual battery cell, enabling real-time monitoring and control of the battery pack's state. This provides a foundation for dynamic response in balancing management from the outset. The collected SOC data is converted into SOC balancing curves and divided into intervals to obtain SOC curve segments for different balancing control stages. This segmented processing method accurately captures the SOC change characteristics at each stage, making the balancing analysis for each stage more targeted and avoiding the crude management approach of treating the overall battery pack state in a one-size-fits-all manner.

[0031] The balance deviation at each stage of the equalization control is calculated using corresponding SOC curve segments, providing a specific quantitative basis for subsequent equalization adjustments and making the adjustment direction clearer. Operating status data of the series-connected lithium battery pack is collected, and parameter interference is obtained. This data is combined with the balance deviation to determine the equalization adjustment amount. This fully considers the impact of various factors on the equalization effect during operation, making the calculation of the equalization adjustment amount more consistent with actual operating conditions and reducing adjustment deviations caused by considering only a single factor.

[0032] The balancing strategy is dynamically adjusted based on the balancing adjustment amount at each balancing control stage, enabling the balancing strategy to flexibly change according to the real-time state of the battery pack and adapt to the balancing needs of different stages. This phased, multi-factor-considered dynamic adjustment method can cover the entire process of battery pack operation, achieving global control over the SOC balancing of the series lithium battery pack. This ensures that the SOC of each individual battery cell maintains good consistency in different operating stages, delays the performance degradation of individual cells caused by imbalance, extends the overall service life of the battery pack, and improves the battery pack's performance in various application scenarios. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating the working principle of the global optimization control method for SOC equalization control of series lithium battery packs described in this invention.

[0034] Figure 2 A flowchart for the method of calculating the equilibrium deviation;

[0035] Figure 3 This is a flowchart of the method for calculating and adjusting the interference degree of parameters. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Please see Figure 1 This invention provides a globally optimized control method for the state-of-charge (SOC) equalization of a series lithium battery pack, the method comprising:

[0038] The series-connected lithium battery pack implements SOC equalization management based on preset equalization parameters, and simultaneously initiates real-time acquisition of the state of charge (SOC) of each individual cell within the battery pack. The preset equalization parameters are pre-set based on the actual configuration of the series-connected lithium battery pack and are used to guide the initial equalization management operation; while real-time acquisition of SOC is to obtain the current state of each individual cell.

[0039] The collected state of charge (SOC) data is converted into a SOC balancing curve for the battery pack. This SOC balancing curve is then divided into intervals to obtain SOC curve segments for the series-connected lithium battery pack at different balancing control stages. The balancing deviation is calculated for each balancing control stage using these corresponding SOC curve segments. Converting the SOC data into an SOC balancing curve provides a clear picture of the overall balancing state of the battery pack. The interval division breaks down the entire balancing process into multiple stages, facilitating fine-grained control at each stage. The calculation of the balancing deviation quantifies the difference between the actual state and the target state at each stage.

[0040] The system collects operational status data of a series-connected lithium battery pack. Based on this data, it obtains the parameter interference degree when the battery pack implements equalization management according to preset equalization parameters. Then, it determines the equalization adjustment amount for each equalization control stage based on the parameter interference degree and the corresponding equalization deviation. The operational status data includes external factors affecting battery equalization. The parameter interference degree reflects the extent to which these factors interfere with the equalization effect. Combining this with the equalization deviation allows for a more accurate determination of the required adjustment range, i.e., the equalization adjustment amount.

[0041] The balancing strategy for each stage of the series-connected lithium battery pack is dynamically adjusted based on the corresponding balancing adjustment amount. By dynamically adjusting the balancing strategy, the battery pack can maintain a good balance state at different stages, achieving the goal of global optimization control.

[0042] Example 1: Setting preset balancing parameters requires consideration of the number and nominal capacity of individual cells in the series-connected lithium battery pack. The number of individual cells directly relates to the complexity of the series structure of the battery pack. Different numbers of individual cells result in differences in energy distribution and current conduction. For example, a series-connected pack consisting of 10 individual cells differs from a series-connected pack consisting of 20 individual cells in terms of internal energy flow paths and the number of nodes for balancing management. The nominal capacity reflects the upper limit of energy storage for each individual cell. There may be slight differences in the nominal capacity of individual cells within the same series-connected pack, and these differences will affect the rate of change of the state of charge of each cell during charging and discharging. When setting preset balancing parameters, it is necessary to first count the specific number of individual cells in the series-connected lithium battery pack and record the nominal capacity value of each individual cell. Then, based on these data, the initial balancing start threshold, balancing current range, and other parameters should be determined. For example, for individual cells with a larger nominal capacity, the initial setting of the balancing current may be relatively larger to accommodate their energy throughput requirements; while for series-connected packs with a larger number of individual cells, the balancing start threshold may be set more finely to cope with the state differences between more individual cells.

[0043] The state of charge (SOC) of each individual cell within the battery pack is acquired in real time through voltage and current sensors integrated into the battery management system (BMS). The BMS is the core control unit of the series-connected lithium-ion battery pack, integrating multiple voltage and current sensors. Each individual cell is connected to at least one voltage sensor and one current sensor. The voltage sensors are connected to the positive and negative terminals of the individual cell via probes or wires, monitoring voltage changes across the cell in real time. The sampling frequency can be set according to actual needs, typically between 10 and 100 times per second. The current sensors are connected in series in the main circuit of the battery pack or in the branch circuits of each individual cell, detecting the magnitude and direction of the current flowing through the cell, accurately capturing both forward current during charging and reverse current during discharging. The voltage and current signals acquired by the sensors are converted into electrical signals and transmitted to the processing module of the BMS. The processing module calculates the real-time SOC of each individual cell based on a preset algorithm, combined with historical parameters such as voltage, current, battery internal resistance, and temperature. During the acquisition process, the sensors operate continuously to ensure that SOC data is acquired promptly, providing a continuous data stream for subsequent equalization control.

[0044] When converting the collected state of charge (SOC) data into a battery pack's SOC equilibrium curve, a moving average filter is first applied to the data. The collected SOC data may contain various noises, which could originate from sensor accuracy errors, electromagnetic interference in the circuitry, or instantaneous fluctuations in the battery itself. Directly using the raw data to plot the curve would result in irregular jitter and spikes, failing to accurately reflect the battery pack's true equilibrium state. The moving average filter, by setting a fixed window size, calculates the arithmetic mean of multiple consecutive SOC data points within the window, using this average as the filtered data at the center of the window. For example, setting the window size to 5 means averaging the SOC data at times n-2, n-1, n, n+1, and n+2, using this average as the filtered data at time n. This method smooths out high-frequency noise in the data, making the volatile raw data more gradual. After completing the moving average filter for all SOC data, the processed data is sequentially connected with time on the horizontal axis and SOC value on the vertical axis to form the battery pack's SOC equilibrium curve. This curve clearly shows the overall state of charge (SOC) trend of the entire series-connected lithium battery pack at different times, as well as the concentrated distribution of the SOC of each individual cell.

[0045] The SOC (State of Charge) equalization curve is divided into intervals based on a preset SOC difference threshold. The SOC difference threshold is a pre-defined difference in state of charge used to determine whether the battery pack's equalization state has entered a new stage. After plotting the SOC equalization curve, the changes in the state of charge value at adjacent moments are analyzed point by point, starting from the curve's starting point. When the difference between the state of charge value at multiple consecutive moments and the average state of charge value of the previous stage is consistently less than the SOC difference threshold, these curve segments belong to the same equalization control stage. When the difference between the state of charge value at a certain moment and the average state of charge value of the previous stage exceeds the SOC difference threshold, a new equalization control stage is defined from that moment. For example, if the preset SOC difference threshold is 2%, and the average state of charge value of the previous stage is 80%, when the curve shows continuous fluctuations in the state of charge value between 78% and 82%, it still belongs to that stage; when the state of charge value drops to 77% and persists for multiple moments, a new equalization control stage is defined from that moment. This interval division allows the entire SOC balancing curve to be divided into multiple continuous curve segments, each corresponding to a balancing control stage. The state of charge (SOC) changes within each stage exhibit relatively stable characteristics, facilitating subsequent balancing adjustments tailored to the specific characteristics of each stage. During the interval division process, the curve changes must be continuously tracked to ensure that each stage accurately reflects the actual transition in the battery pack's balancing state. After division, the SOC curve segment for each balancing control stage will serve as the basis for calculating the balancing deviation for that stage.

[0046] Example 2: See Figure 2 To calculate the equilibrium deviation of each equilibrium control stage using the corresponding SOC curve segments, the following procedure must be followed: For each equilibrium control stage, first extract the SOC curve segment for that stage. Each equilibrium control stage corresponds to a continuous time interval. The state of charge data collected within this time interval forms the corresponding SOC curve segment. During extraction, it is necessary to ensure that the segment contains the state of charge data at all times within that stage, without omitting any data points, to guarantee the completeness of subsequent calculations.

[0047] Obtain the target SOC value corresponding to this equalization control stage within the preset equalization parameters. The target SOC value is the ideal state of charge value set for each equalization control stage within the preset equalization parameters. This value is determined based on the overall performance requirements of the series lithium battery pack and the functional positioning of each stage. Different equalization control stages may correspond to different target SOC values; for example, the target SOC value will differ between the initial and middle stages of charging.

[0048] Calculate the arithmetic mean of the SOC curve segment. Sum the values ​​of all state of charge (SOC) data points within that SOC curve segment, then divide by the number of data points. The result is the arithmetic mean. This mean comprehensively reflects the overall SOC level within that segment, avoiding the influence of abnormal fluctuations in a single data point on the overall assessment.

[0049] Based on the calculated arithmetic mean and the target SOC value, the deviation coefficient for each state of charge data point in the SOC curve segment is determined. The determination of the deviation coefficient needs to consider the difference between each data point and the target SOC value, while also taking into account the relationship between the arithmetic mean and the target SOC value. For example, when the arithmetic mean is higher than the target SOC value, the calculation method for the deviation coefficient of a data point that is higher than the arithmetic mean will differ from that when it is lower than the arithmetic mean, thus reflecting the different impacts of deviations in different directions on the overall equilibrium state.

[0050] The equilibrium deviation of this equilibrium control stage is calculated by using the deviation coefficients of all state-of-charge (SOC) data points during this stage. All deviation coefficients are then aggregated, using methods such as summation or averaging. The resulting equilibrium deviation quantifies the overall deviation between the actual SOC of the battery pack and the target SOC value during this stage. A larger deviation indicates a greater gap between the equilibrium effect of this stage and the expected target.

[0051] The battery management system (BMS) collects operational status data from the series-connected lithium-ion battery pack via its communication interface. This interface provides data transmission capabilities, enabling connections with various monitoring devices within the battery pack. These devices are distributed across different locations within the pack, each responsible for collecting specific operational parameters. For example, temperature sensors are installed on or near individual cells to monitor their real-time temperature; current sensors are connected in series in the main circuit to monitor the charging and discharging current of the entire battery pack; and voltage sensors are connected to individual cells or battery modules to monitor voltage changes.

[0052] The operational status data collected by the monitoring device is transmitted to the communication interface of the battery management system via wired or wireless means. Wired transmission typically uses dedicated data cables, which are characterized by stable transmission and strong anti-interference capabilities; wireless transmission uses wireless communication technologies such as Bluetooth and WiFi, which are suitable for scenarios where wiring is inconvenient. When receiving data, the communication interface performs preliminary format conversion to make it conform to the internal data processing standards of the battery management system, ensuring that subsequent data processing units can correctly recognize and process it.

[0053] The acquisition frequency of operational status data is kept consistent with that of state of charge (SOC) data to ensure their correspondence in the time dimension. For example, if SOC data is acquired once per second, operational status data is also acquired once per second. This allows for the correlation between SOC data and operational status data at the same moment in subsequent data analysis, enabling accurate analysis of the impact of operational status on SOC.

[0054] The collected operational status data is diverse, including not only temperature, current, and voltage, but also parameters such as battery pack operating time and cycle count. These data reflect the operation of the series-connected lithium battery pack from different perspectives: temperature data reflects the battery pack's heat dissipation performance and the intensity of internal chemical reactions; current data reflects the intensity of energy flow; and voltage data is directly related to the battery's state of charge.

[0055] During data transmission, the communication interface performs real-time data verification. If a data transmission error or loss is detected, the monitoring device will be immediately requested to retransmit the data to ensure the accuracy and integrity of the operational status data. The collected operational status data is temporarily stored in the battery management system's cache, awaiting subsequent processing and analysis, providing comprehensive and reliable raw data for calculating parameter interference.

[0056] The operational status data collected through the above methods can comprehensively reflect the operating status of the series lithium battery pack at different times, providing rich information for subsequent analysis of parameter interference. This allows the calculation of parameter interference to be based on real and accurate operating status, thereby better reflecting the impact of external factors on battery equalization management.

[0057] Example 3: Determining the balance adjustment amount for each balance control stage based on parameter interference and corresponding balance deviation requires the following procedure: For each balance control stage, first extract the corresponding reference adjustment coefficient in the preset balance parameters. The reference adjustment coefficient is the initial adjustment reference value set for each balance control stage in the preset balance parameters, and its value is related to the balance target and structural characteristics of the battery pack for that stage. Different balance control stages have different reference adjustment coefficients. For example, in stages with a high state of charge (SOC) of the battery pack, the reference adjustment coefficient may be set relatively small, while in stages with a low SOC, the reference adjustment coefficient may be set relatively large. During the extraction process, it is necessary to accurately match each balance control stage with its corresponding reference adjustment coefficient to avoid confusing the parameters of different stages.

[0058] Obtain the parameter disturbance degree for this equalization control phase. The parameter disturbance degree is calculated based on the operating status data of the series-connected lithium battery pack and reflects the degree of interference from internal and external factors on equalization management during this phase. The magnitude of the parameter disturbance degree is related to factors such as temperature fluctuations and current fluctuations in the operating status data. When these fluctuations are more severe, the parameter disturbance degree is larger; when the operating status is relatively stable, the parameter disturbance degree is smaller. When determining the equalization adjustment amount, the parameter disturbance degree data corresponding to this phase must be retrieved to ensure the timeliness and relevance of the data.

[0059] Extract the balance deviation for this balance control stage. The balance deviation is calculated from the SOC curve segment of this stage and is used to quantify the overall difference between the actual state of charge (SOC) of the battery pack and the target SOC value within this stage. A larger balance deviation indicates a more significant difference between the actual and target states in this stage; a smaller balance deviation indicates that the balance effect in this stage is closer to expectations. When extracting the balance deviation, it is necessary to ensure that it strictly corresponds to the current balance control stage being processed, avoiding data retrieval across stages.

[0060] The balance adjustment amount is calculated based on the benchmark adjustment coefficient, parameter disturbance degree, and balance deviation degree. The calculation formula is as follows:

[0061] ΔE=k×(d1+d2)

[0062] Where ΔE represents the equalization adjustment amount, k represents the baseline adjustment coefficient, d1 represents the parameter disturbance degree, and d2 represents the equalization deviation degree.

[0063] During the calculation, the values ​​of the benchmark adjustment coefficient, parameter disturbance degree, and equilibrium deviation degree need to be substituted into the above formula. The calculation should be performed in the following order: first calculate the sum of the parameter disturbance degree and the equilibrium deviation degree (within parentheses), and then multiply the result by the benchmark adjustment coefficient. During the calculation, attention should be paid to the consistency of units for each parameter. If there are unit differences, unit conversion must be performed first to ensure the accuracy of the calculation results.

[0064] The calculated equalization adjustment amount reflects the magnitude of adjustment required to achieve the ideal equalization state of the battery pack at the current stage. When the parameter disturbance or equalization deviation is large, the calculated equalization adjustment amount is correspondingly large, indicating that a significant adjustment to the equalization strategy is needed; when the parameter disturbance and equalization deviation are small, the equalization adjustment amount is also small, indicating that only a fine-tuning of the equalization strategy is required.

[0065] After the calculation is completed, the value of the equilibrium adjustment amount needs to be recorded and stored in association with this equilibrium control stage for retrieval during subsequent equilibrium strategy adjustments. Simultaneously, it is necessary to check for data input errors or calculation errors during the calculation process. If errors are found, the calculation must be recalculated to ensure the accuracy of the equilibrium adjustment amount.

[0066] Through the above process, a suitable equalization adjustment amount can be determined for each equalization control stage. This adjustment amount comprehensively considers the influence of the reference adjustment coefficient, parameter disturbance degree, and equalization deviation degree, making the adjustment of the equalization strategy more in line with the actual operating state and equalization requirements of the battery pack. The equalization adjustment amount may differ in different equalization control stages, reflecting the different requirements for equalization adjustment in different stages. By calculating and applying the equalization adjustment amount in stages, fine-grained control of the SOC equalization of series lithium battery packs can be achieved.

[0067] Example 4: The balancing strategy for each balancing control stage in a series-connected lithium battery pack is dynamically adjusted based on the corresponding balancing adjustment amount. This requires following a step-by-step procedure. For each balancing control stage of the series-connected lithium battery pack, the corresponding baseline adjustment coefficient in the preset balancing parameters must first be determined. The baseline adjustment coefficient is preset before balancing control begins, based on the design parameters of the series-connected lithium battery pack, the operating environment, and the balancing objectives for each stage. Different balancing control stages will have different baseline adjustment coefficients. These coefficients are stored in the parameter library of the battery management system and can be directly accessed.

[0068] After obtaining the baseline adjustment coefficient, it is necessary to extract the balance adjustment amount calculated for this balance control stage. The balance adjustment amount is determined by combining the parameter disturbance degree and balance deviation degree of this stage, reflecting the specific magnitude of adjustment required to achieve the ideal balance state. Its value is closely related to the actual operating state of this stage, and may be positive or negative, corresponding to the adjustment direction that needs to be strengthened or weakened, respectively.

[0069] Next, the baseline adjustment coefficient and the balance adjustment amount are combined to determine the actual adjustment coefficient. The calculation method needs to be determined according to the logic of balance control. For example, when the balance adjustment amount is positive, the baseline adjustment coefficient is added to the balance adjustment amount. The resulting actual adjustment coefficient is greater than the baseline adjustment coefficient, which means that the intensity of the balance operation needs to be increased. When the balance adjustment amount is negative, the absolute value of the balance adjustment amount is subtracted from the baseline adjustment coefficient. The resulting actual adjustment coefficient is less than the baseline adjustment coefficient, which indicates that the intensity of the balance operation needs to be reduced. This calculation must ensure that the result meets the basic requirements of balance control at this stage and does not contradict the balance objective.

[0070] Once the actual adjustment coefficient is determined, the balancing strategy for this balancing control stage can be adjusted accordingly. Adjusting the balancing strategy involves several aspects, including the magnitude of the balancing current, the duration of the balancing time, and the threshold for balancing initiation. Taking the balancing current as an example, if the actual adjustment coefficient is greater than the reference adjustment coefficient, it indicates that the balancing current needs to be increased. In this case, the power devices in the balancing circuit can be controlled by the battery management system, such as adjusting the conduction time or frequency of the MOSFET, to increase the balancing current flowing through the individual battery cells and accelerate the energy transfer speed. If the actual adjustment coefficient is less than the reference adjustment coefficient, the balancing current should be reduced by decreasing the duty cycle of the MOSFET to avoid energy loss caused by over-balancing.

[0071] Regarding the adjustment of the equalization time, when the actual adjustment coefficient is large, the duration of each equalization cycle can be extended, allowing individual cells more time for energy exchange and promoting rapid state of charge (SOC) equalization. When the actual adjustment coefficient is small, the equalization time should be shortened to reduce unnecessary energy consumption. Adjusting the equalization initiation threshold refers to changing the SOC difference condition that triggers the equalization operation. When the actual adjustment coefficient is large, the initiation threshold can be lowered, allowing the equalization operation to intervene earlier and preventing the SOC difference from widening. When the actual adjustment coefficient is small, the initiation threshold should be increased to reduce the frequency of equalization initiation.

[0072] During dynamic adjustment, it is necessary to monitor the state of charge (SOC) changes of each individual battery cell in real time to ensure that the adjusted balancing strategy can function effectively. The monitored SOC data is continuously fed back to the battery management system, which recalculates the balancing deviation and adjustment amount based on the new data, providing a basis for the next balancing strategy adjustment. This iterative adjustment process is carried out throughout the entire balancing control phase, enabling the balancing strategy to always adapt to the real-time state of the battery pack.

[0073] The focus of dynamic adjustments may differ at different stages of equalization control. For example, in the stage where the battery pack has a low state of charge (SOC), the equalization strategy adjustment may prioritize the stability of the equalization current to avoid high current impacting the battery; while in the stage where the SOC is high, the adjustment focuses more on the precise control of the equalization time to prevent overcharging. Adjustments for each stage must be tailored to its specific characteristics to ensure that the adjusted equalization strategy matches the battery state at that stage.

[0074] The entire adjustment process must be carried out in an orderly manner under the coordination of the battery management system. The system executes calculation and control instructions through its internal microprocessor and sends control signals to each equalization module through the communication bus. Each module performs corresponding operations according to the instructions. At the same time, the system records the parameters and corresponding time points of each adjustment, forming an adjustment log, which facilitates subsequent traceability and analysis of the equalization control process. Through this dynamic adjustment mechanism, the series-connected lithium battery pack can maintain good consistency of state of charge in each equalization control stage, achieving a globally optimized equalization control effect.

[0075] Example 5: See Figure 3 To obtain the parameter interference level of a series lithium battery pack under equalization management based on preset equalization parameters, based on operational status data, the following procedure must be followed: Extract temperature and current fluctuation values ​​from the collected operational status data. The operational status data contains temperature and current data at multiple points in time. The temperature fluctuation value is obtained by calculating the change in temperature data within a certain time range. Specifically, first determine the highest and lowest temperature values ​​within that time range, and the difference between them is the temperature fluctuation value. The current fluctuation value is obtained similarly; find the maximum and minimum current values ​​within the same time range, and the difference between them is the current fluctuation value. During the extraction process, the selection of the time range must match the division of the equalization control stage to ensure that the temperature and current fluctuation values ​​can reflect the actual fluctuation situation within that stage.

[0076] The product of temperature fluctuation and current fluctuation is calculated and used as the parameter disturbance degree. The calculation of the product must ensure that the units of temperature and current fluctuation values ​​are consistent; if there are unit differences, they must be converted first. The magnitude of the parameter disturbance degree is directly related to the degree of temperature and current fluctuation. When both fluctuations are relatively severe, the parameter disturbance degree is large; when both are relatively stable, the parameter disturbance degree is small. The parameter disturbance degree obtained in this way can comprehensively reflect the combined impact of temperature and current fluctuations on equilibrium management.

[0077] After determining the equalization adjustment amount for each equalization control stage, the equalization adjustment amount needs to be limited within a preset maximum adjustment range. This preset maximum adjustment range is set based on the hardware performance, safety characteristics, and actual equalization control requirements of the series-connected lithium battery pack. This range includes an upper limit and a lower limit. The upper limit represents the maximum positive value that the equalization adjustment amount can achieve, and the lower limit represents the minimum negative value (or zero, depending on the actual situation) that the equalization adjustment amount can achieve. The setting of the maximum adjustment range must consider the battery pack's tolerance. For example, excessive equalization adjustment can lead to excessive current in the equalization circuit, potentially exceeding the rated load capacity of power devices, causing overheating or damage. Therefore, it is necessary to constrain this range using the maximum adjustment range.

[0078] If the calculated equilibrium adjustment amount is within the preset maximum adjustment range (i.e., greater than or equal to the lower limit and less than or equal to the upper limit), then this equilibrium adjustment amount is directly used as the actual adjustment amount for subsequent equilibrium strategy adjustments. In this case, the equilibrium adjustment amount can function normally according to the calculation results, achieving precise adjustment of the equilibrium strategy.

[0079] If the equalization adjustment exceeds the preset maximum adjustment range (i.e., greater than the upper limit or less than the lower limit), the boundary value of the maximum adjustment range is used as the actual adjustment amount. When the equalization adjustment is greater than the upper limit, the upper limit is used as the actual adjustment amount; when the equalization adjustment is less than the lower limit, the lower limit is used as the actual adjustment amount. This method avoids damage to the battery pack or equalization circuit due to excessive adjustment, ensuring the safety of the equalization control process. For example, if the calculated equalization adjustment is 15, and the preset maximum adjustment range upper limit is 10, the actual adjustment amount is 10; if the calculated equalization adjustment is -8, and the preset maximum adjustment range lower limit is -5, the actual adjustment amount is -5.

[0080] After determining the actual adjustment amount, it needs to be associated with and stored in relation to the corresponding equalization control stage for later use when dynamically adjusting the equalization strategy. Simultaneously, it's necessary to record whether the equalization adjustment amount exceeds the maximum adjustment range and the actual boundary values ​​used, providing raw information for subsequent data analysis and parameter optimization. This limitation on the range of the equalization adjustment amount is a crucial step in the equalization control process, ensuring both the equalization effect and the safe and stable operation of the battery pack and related circuits.

[0081] Each equalization control stage requires executing the above process: first, calculating the parameter disturbance degree; then, determining the equalization adjustment amount based on the equalization deviation degree; and finally, determining the actual adjustment amount based on the maximum adjustment range. The maximum adjustment range may be the same or different in different stages, depending on the equalization target and the state of the battery pack at that stage. For example, in stages where the battery pack is close to full charge or full discharge, the maximum adjustment range may be set smaller to avoid over-adjustment and damage to the battery. This staged approach ensures that the equalization adjustment in each stage is performed within a safe and reasonable range, thereby achieving global optimized control of the SOC equalization of the series lithium battery pack.

[0082] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0083] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A globally optimized control method for SOC equalization control of a series lithium battery pack, characterized in that, The control method includes the following operations: The series-connected lithium battery pack implements SOC equalization management based on preset equalization parameters, and simultaneously starts real-time acquisition of the state of charge of each individual cell in the battery pack. The collected state of charge data is converted into the SOC equalization curve of the battery pack. The SOC equalization curve is divided into intervals to obtain SOC curve segments of the series lithium battery pack at different equalization control stages. The equalization deviation of each equalization control stage is calculated through the corresponding SOC curve segments. Collect the operating status data of the series lithium battery pack, obtain the parameter interference degree when the series lithium battery pack implements balance management according to the preset balance parameters based on the operating status data, and determine the balance adjustment amount of each balance control stage according to the parameter interference degree and the corresponding balance deviation. The equalization strategy of each equalization control stage in the series lithium battery pack is dynamically adjusted according to the corresponding equalization adjustment amount. The determination of the balance adjustment amount for each balance control stage based on the aforementioned parameter disturbance degree and the corresponding balance deviation degree specifically includes: For each equalization control stage, extract the benchmark adjustment coefficient corresponding to that stage from the preset equalization parameters; The balance adjustment amount of the balance control stage is calculated based on the benchmark adjustment coefficient, the parameter disturbance degree, and the balance deviation degree of the balance control stage, thereby obtaining the balance adjustment amount of each balance control stage. The balance adjustment amount is calculated based on the benchmark adjustment coefficient, parameter disturbance degree, and balance deviation degree. The calculation formula is as follows: in, This indicates the balance adjustment amount. Indicates the benchmark adjustment coefficient. Indicates the parameter interference degree. Indicates the degree of imbalance; The dynamic adjustment of the balancing strategy for each balancing control stage in the series lithium battery pack based on the corresponding balancing adjustment amount specifically includes: For each equalization control stage in the series lithium battery pack, the actual adjustment coefficient of the stage is determined based on the benchmark adjustment coefficient corresponding to the preset equalization parameters and the equalization adjustment amount of the stage, thereby completing the dynamic adjustment of the equalization strategy for each equalization control stage in the series lithium battery pack.

2. The global optimization control method for SOC equalization of a series lithium battery pack as described in claim 1, characterized in that, Set preset equalization parameters based on the number of individual cells and nominal capacity of the series lithium battery pack.

3. The global optimization control method for SOC equalization of a series lithium battery pack as described in claim 1, characterized in that, Real-time acquisition of the state of charge (SOC) of each individual cell within the battery pack is achieved by collecting the SOC of each individual cell using voltage and current sensors integrated into the battery management system.

4. The global optimization control method for SOC equalization of a series lithium battery pack as described in claim 1, characterized in that, Converting the collected state of charge (SOC) data into the SOC equilibrium curve of the battery pack involves performing a moving average filter on the collected SOC data to obtain the SOC equilibrium curve of the battery pack.

5. The globally optimized control method for SOC equalization of a series lithium battery pack as described in claim 1, characterized in that, The SOC equilibrium curve is divided into intervals based on a preset SOC difference threshold.

6. The global optimization control method for SOC equalization of a series lithium battery pack as described in claim 1, characterized in that, The calculation of the equilibrium deviation at each equilibrium control stage using the corresponding SOC curve segment specifically includes: For each equilibrium control stage, extract the SOC curve segment for that stage; Obtain the target SOC value corresponding to the preset equalization parameters in the equalization control stage; Calculate the arithmetic mean of the SOC curve segments; The deviation coefficient of each state of charge data point in the SOC curve segment is determined based on the arithmetic mean and the target SOC value. The equilibrium deviation of the equilibrium control stage is calculated by using all the deviation coefficients, and then the equilibrium deviation of each equilibrium control stage is obtained.

7. The globally optimized control method for SOC equalization of a series lithium battery pack as described in claim 1, characterized in that, The operating status data of the series lithium battery pack is collected through the communication interface of the battery management system.

8. The global optimization control method for SOC equalization of a series lithium battery pack as described in claim 1, characterized in that, The parameter interference degree of the series lithium battery pack when implementing equalization management according to the preset equalization parameters based on the operating status data specifically includes: obtaining the temperature fluctuation value and current fluctuation value in the operating status data, calculating the product of the temperature fluctuation value and current fluctuation value, and using the product as the parameter interference degree. After determining the balance adjustment amount for each balance control stage, the balance adjustment amount is limited to the preset maximum adjustment range. If the balance adjustment amount exceeds the maximum adjustment range, the boundary value of the maximum adjustment range is used as the actual adjustment amount.

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