Active online voltage balancing method and system based on battery circulation of storage battery

Abstract

The invention discloses an active online voltage balancing method and system based on battery circulation of a storage battery, and the method comprises the steps: obtaining a voltage value, an SOC value and a temperature value of each single storage battery in a storage battery pack, and judging whether the storage battery pack needs to be balanced or not; if yes, determining a target equalization single storage battery in the storage battery pack and a source single storage battery in an equalization circuit; controlling the equalization circuit, and transmitting the electric energy of the source single storage battery to the target equalization single storage battery through the equalization circuit; in the electric energy transmission process, the transmission current and the transmission time of the equalization circuit are dynamically adjusted by adjusting the working state of the corresponding equalization module in the equalization circuit; after the equalization is completed, judging whether the voltage, the SOC value and the temperature of each single storage battery in the storage battery pack are equalized or not, and if so, stopping equalization; according to the invention, the equalization efficiency and precision are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of storage batteries, and in particular to an active online voltage equalization method and system based on battery circulation of storage batteries. Background Art

[0002] In the application field of batteries, multiple single cells are usually connected in series or in parallel to form a battery pack to meet the needs of high voltage and large capacity. However, due to differences in production processes and material properties of single cells, their parameters such as capacity and internal resistance are not completely consistent. During long-term charge and discharge cycles, this inconsistency will gradually accumulate, causing voltage imbalance between single cells in the battery pack.

[0003] Voltage imbalance can lead to problems such as reduced capacity, shortened cycle life and reduced safety of the battery pack. In order to extend the service life of the battery pack and ensure its safe and reliable operation, effective balancing measures need to be taken to reduce the voltage difference between single batteries.

[0004] Traditional balancing methods mainly include passive balancing and active balancing. Passive balancing dissipates the excess energy of single cells in the form of heat energy through parallel resistors and other components to achieve voltage balancing. This method has a simple structure and low cost, but low energy utilization efficiency and slow balancing speed. Active balancing transfers the energy of high-voltage single cells to low-voltage single cells through an energy transfer circuit to achieve voltage balancing. Compared with passive balancing, active balancing can achieve energy recycling and has the advantages of fast balancing speed and high energy utilization efficiency, but the circuit structure is relatively complex.

[0005] At present, active balancing circuits mainly include inductor balancing circuits, capacitor balancing circuits and transformer balancing circuits. Inductor balancing circuits and capacitor balancing circuits achieve energy transfer through switched capacitors or switched inductors. The circuit structure is relatively simple, but the balancing current is small and the balancing speed is limited. Transformer balancing circuits achieve energy transfer through multi-winding transformers. They have the advantages of large current and fast speed, but the transformer is large in size and weight, and the cost is high.

[0006] In addition, most existing active balancing methods use centralized control strategies, which require additional controllers and communication lines, increasing the complexity and cost of the system. At the same time, centralized control is susceptible to communication delays and single-point failures, reducing the reliability of the balancing system. Summary of the invention

[0007] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide an active online voltage equalization method and system based on battery circulation of a storage battery to solve the problems raised in the background technology.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: an active online voltage equalization method based on battery circulation of a battery, which comprises the following steps: S1, obtaining the voltage value, SOC value and temperature value of each single battery in the battery pack, and judging whether the battery pack needs to be balanced based on the preset voltage balance threshold, SOC balance threshold and temperature balance threshold; if so, determining the target balanced single battery in the battery pack and the source single battery in the balancing circuit according to the voltage value, SOC value and temperature value; S2, controlling the balancing circuit to transmit the electric energy of the source single battery to the target balancing single battery through the balancing circuit, so as to achieve voltage balancing between the target balancing single battery and other single batteries in the battery pack; S3. During the process of transmitting electric energy, the discharge current, discharge voltage and temperature of the source single battery, and the charging current, charging voltage and temperature of the target balanced single battery are monitored in real time. By adjusting the working state of the corresponding balancing module in the balancing circuit, the transmission current and transmission time of the balancing circuit are dynamically adjusted to avoid over-discharge of the source single battery and over-charging of the target balanced single battery. After the balancing is completed, it is determined whether the voltage, SOC value and temperature of each single battery in the battery pack are balanced. If so, the balancing is stopped. Furthermore, in S1, the port voltage, current and temperature parameters of each single battery are measured in real time through the acquisition circuit in the battery management system; based on the measured voltage, current and temperature data, the SOC value of each single battery is estimated by using Kalman filtering, extended Kalman filtering or particle filtering algorithm; the acquired voltage value, SOC value and temperature value are stored in the memory of the BMS for subsequent balancing judgment and control.

[0009] Further, in S1, it is determined whether the battery pack needs to be balanced, and a voltage balance threshold is set. When the absolute value of the voltage difference between any two single batteries in the battery pack exceeds the voltage balance threshold, it is considered that voltage balance is required; an SOC balance threshold is set. When the absolute value of the SOC difference between any two single batteries in the battery pack exceeds the SOC balance threshold, it is considered that SOC balance is required; a temperature balance threshold is set. When the absolute value of the temperature difference between any two single batteries in the battery pack exceeds the temperature balance threshold, it is considered that temperature balance is required; If the voltage difference, SOC difference or temperature difference exceeds the corresponding equalization threshold, it is determined that the battery pack needs to be equalized; otherwise, it is considered that the battery pack is in a balanced state and does not need to be equalized; For voltage balancing, the single battery with the lowest voltage is selected as the target balancing single battery, and the single battery with the highest voltage is selected as the source single battery; for SOC balancing, the single battery with the lowest SOC is selected as the target balancing single battery, and the single battery with the highest SOC is selected as the source single battery; for temperature balancing, the single battery with the lowest temperature is selected as the target balancing single battery, and the single battery with the highest temperature is selected as the source single battery; If voltage imbalance, SOC imbalance and temperature imbalance exist at the same time, the target balanced single battery and the source single battery are selected according to the principle of voltage balance first, SOC balance second and temperature balance last; According to the determined target balancing single battery and source single battery, the corresponding balancing module in the balancing circuit is controlled to work; PWM modulation, PFM modulation or other modulation methods are used to control the power switch tube in the balancing module to be turned on or off to realize the energy transfer from the source single battery to the target balancing single battery; according to the SOC value of the source single battery and the SOC value of the target balancing single battery, the transmission current and transmission time of the balancing circuit are dynamically adjusted to avoid over-discharge or over-charge; during the balancing process, the discharge current, discharge voltage and temperature of the source single battery, as well as the charging current, charging voltage and temperature of the target balancing single battery are monitored in real time to ensure the safety and reliability of the balancing process.

[0010] Further, in S1, determining the target balancing single battery in the battery pack and the source single battery in the balancing circuit according to the voltage value, the SOC value and the temperature value includes: For each single battery in the battery pack, extract its voltage value, SOC value and temperature value to form a sample data set; The fuzzy c-means clustering algorithm is used to cluster the sample data set to obtain the membership matrix and cluster center matrix of each sample point belonging to different cluster centers; According to the membership matrix, the average voltage value, average SOC value and average temperature value of the sample points in each cluster center are calculated, and the average voltage value, average SOC value and average temperature value are used as the clustering characteristic values ​​of the cluster center; For any single battery in the battery pack, the membership of the single battery to each cluster center is calculated according to the voltage value, SOC value and temperature value of the single battery, and the comprehensive evaluation index of the single battery is calculated according to the clustering characteristic value and membership degree of each cluster center and the clustering weight value corresponding to the clustering characteristic value; The single battery with the smallest comprehensive evaluation index is selected as the target balancing single battery, and the single battery with the largest comprehensive evaluation index is selected as the source single battery.

[0011] Furthermore, the comprehensive evaluation index of the single battery is calculated based on the clustering characteristic value and membership degree of each cluster center and the clustering weight value corresponding to the clustering characteristic value, including:

[0012] Among them, S i represents the comprehensive evaluation index of the ith single battery, C represents the number of cluster centers, u ij represents the membership degree of the i-th battery cell to the j-th cluster center, w1, w2, w3 represent the cluster weight values ​​corresponding to the voltage value, SOC value and temperature value respectively, V j , SOC j , T j They represent the average voltage, average SOC and average temperature of the jth cluster center, respectively. i , SOC i , T i Respectively represent the voltage value, SOC value and temperature value of the i-th single battery, SOC max , SOC min Respectively represent the maximum and minimum SOC values ​​of all single batteries, V max 、V min Respectively represent the maximum and minimum voltage values ​​of all single battery cells, T max , T min They respectively represent the maximum and minimum temperature values ​​of all single batteries.

[0013] Further, in S2, the method for controlling the equalization circuit includes: According to the voltage error of the target balanced single battery, the given value of the transmission current is calculated through the outer voltage control loop, and the outer voltage control loop adopts a PI controller; According to the given value and actual value of the transmission current, the conduction duty cycle of the power switch tube is adjusted through the inner current control loop, and the inner current control loop adopts a proportional controller; During the transmission of electric energy, the discharge current of the source single battery and the charging current of the target balancing single battery are monitored in real time; When the discharge current of the source single battery exceeds a preset safety threshold, the transmission current is reduced or the discharge of the source single battery is stopped; When the charging current of the target balancing single storage battery exceeds a preset safety threshold, the transmission current is reduced or the charging of the target balancing single storage battery is stopped.

[0014] Furthermore, the outer voltage control loop adopts a PI controller, and the transfer function corresponding to the PI controller is as follows:

[0015] Among them, G v represents the transfer value corresponding to the transfer function s of the PI controller, K pv represents the proportional coefficient of the voltage controller, T iv represents the integral time constant of the voltage controller, T fv represents the filtering time constant of the voltage controller, τv represents the lag time of the voltage control loop; The inner current control loop uses a proportional controller, and the transfer function corresponding to the proportional controller is as follows:

[0016] Among them, G i represents the transfer value of the proportional controller, K pi represents the proportionality factor of the current controller, K ii Indicates the integral coefficient of the current controller, K di represents the differential coefficient of the current controller, T fi Indicates the filter time constant of the current controller.

[0017] Furthermore, S3 specifically includes the following processes: During the process of transmitting electric energy, the discharge current, discharge voltage and temperature of the source single battery, as well as the charging current, charging voltage and temperature of the target balanced single battery are monitored in real time through the sensors in the balancing circuit; according to the monitored data, the working state of the corresponding balancing module, including the transmission current and transmission time, is dynamically adjusted through the controller in the balancing circuit; Calculate the adjustment amount of the transmission current according to the discharge current of the source single battery and the charging current of the target balancing single battery; update the given value of the transmission current according to the adjustment amount; make the actual transmission current track the given value by adjusting the conduction duty cycle of the power switch tube in the balancing circuit; Calculate the adjustment amount of the transmission time according to the discharge voltage of the source single battery and the charge voltage of the target balancing single battery; update the given value of the transmission time according to the adjustment amount; and make the actual transmission time track the given value by setting the conduction time of the power switch tube in the balancing circuit; To avoid overdischarge of the source single battery, when the discharge voltage of the source single battery is lower than the preset discharge cut-off voltage, the discharge of the source single battery is stopped and the connection between the source single battery and the balancing circuit is cut off; to avoid overcharging of the target balancing single battery, when the charging voltage of the target balancing single battery is higher than the preset charging cut-off voltage, the charging of the target balancing single battery is stopped and the connection between the balancing circuit and the target balancing single battery is cut off; During the process of source single battery discharging and target balanced single battery charging, their temperatures are monitored in real time. When the temperature exceeds the preset safety threshold, the transmission of power is stopped, the corresponding connection is cut off, and the thermal management system is started for cooling. After balancing is completed, BMS regularly monitors the status of the battery pack, including the voltage, SOC value and temperature of the single battery; when the balancing status of the battery pack changes and no longer meets the conditions for completing balancing, the balancing process is restarted to maintain the consistency and stability of the battery pack; during battery operation and charging and discharging, BMS adjusts the balancing strategy and parameters in a timely manner according to the usage and environmental conditions of the battery pack to ensure the optimization of the balancing effect.

[0018] Furthermore, S3 also includes the following processes: During the process of transmitting electric energy, if the discharge current of the source single battery is greater than a preset maximum discharge current threshold, or the discharge voltage of the source single battery is less than a preset minimum discharge voltage threshold, or the temperature of the source single battery is greater than a preset maximum temperature threshold, the discharge of the source single battery is stopped; During the process of transmitting electric energy, if the charging current of the target balancing single battery is greater than the preset maximum charging current threshold, or the charging voltage of the target balancing single battery is greater than the preset maximum charging voltage threshold, or the temperature of the target balancing single battery is greater than the preset maximum temperature threshold, the charging of the target balancing single battery is stopped.

[0019] The present invention also discloses an active online voltage equalization system based on battery circulation of a storage battery, which comprises: The first unit is used to obtain the voltage value, SOC value and temperature value of each single battery in the battery pack, and judge whether the battery pack needs to be balanced based on the preset voltage balance threshold, SOC balance threshold and temperature balance threshold; if so, determine the target balanced single battery in the battery pack and the source single battery in the balancing circuit according to the voltage value, SOC value and temperature value; The second unit is used to control the balancing circuit to transmit the electric energy of the source single storage battery to the target balancing single storage battery through the balancing circuit, so as to achieve voltage balancing between the target balancing single storage battery and other single storage batteries in the battery pack; The third unit is used to monitor the discharge current, discharge voltage and temperature of the source single battery, and the charging current, charging voltage and temperature of the target balanced single battery in real time during the process of transmitting electric energy, and dynamically adjust the transmission current and transmission time of the balancing circuit by adjusting the working state of the corresponding balancing module in the balancing circuit to avoid over-discharge of the source single battery and over-charging of the target balanced single battery; after the balancing is completed, it is determined whether the voltage, SOC value and temperature of each single battery in the battery group are balanced, and if so, the balancing is stopped.

[0020] Beneficial effects of the present invention: The present invention obtains the voltage value, SOC value and temperature value of each single battery in the battery pack, and determines whether equalization is needed based on a preset equalization threshold value, so as to monitor the state of the battery pack in real time, timely discover and solve the imbalance problem between the single batteries, and improve the performance and reliability of the battery pack. According to the voltage value, SOC value and temperature value, the target equalization single battery and the source single battery are determined, and multiple influencing factors can be comprehensively considered to select the optimal equalization path and strategy, thereby improving the efficiency and accuracy of equalization.

[0021] The present invention transmits the electric energy of the source single battery to the target balanced single battery by controlling the balanced circuit, so as to realize active transfer and reuse of energy, avoid energy waste in passive balancing, and improve energy utilization efficiency. In the process of transmitting electric energy, the discharge / charging current, voltage and temperature of the source single battery and the target balanced single battery are monitored in real time, and the transmission current and transmission time are dynamically adjusted by adjusting the working state of the balanced circuit, so as to avoid over-discharge and over-charge, and ensure the safety and reliability of the balanced process.

[0022] After the equalization is completed, the voltage, SOC value and temperature of each single battery in the battery pack are judged to be balanced, and the equalization effect can be verified to ensure that the performance of the battery pack after equalization meets the requirements, thereby improving the stability and reliability of the system. Compared with the traditional centralized control strategy, this technology adopts a distributed control strategy, and each equalization module can work independently, reducing the dependence on the central controller and communication lines, and improving the flexibility, scalability and robustness of the equalization system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2 It is a schematic diagram of the structure of the system of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] Example 1: Figure 1 As shown, an active online voltage equalization method based on battery circulation of a battery comprises the following steps: Obtaining the voltage value, SOC value and temperature value of each single battery in the battery pack, and judging whether the battery pack needs to be balanced based on the preset voltage balancing threshold, SOC balancing threshold and temperature balancing threshold; if so, determining the target balanced single battery in the battery pack and the source single battery in the balancing circuit according to the voltage value, SOC value and temperature value; For example, the acquisition circuit in the battery management system (BMS) measures the port voltage, current, temperature and other parameters of each single battery in real time. Based on the measured voltage, current and temperature data, the SOC value of each single battery is estimated by using algorithms such as Kalman filtering, extended Kalman filtering or particle filtering. The acquired voltage value, SOC value and temperature value are stored in the memory of the BMS for subsequent equalization judgment and control.

[0026] Determine whether the battery pack needs to be balanced, set the voltage balance threshold, when the absolute value of the voltage difference between any two single batteries in the battery pack exceeds the voltage balance threshold, it is considered that voltage balance is required. Set the SOC balance threshold, when the absolute value of the SOC difference between any two single batteries in the battery pack exceeds the SOC balance threshold, it is considered that SOC balance is required. Set the temperature balance threshold, when the absolute value of the temperature difference between any two single batteries in the battery pack exceeds the temperature balance threshold, it is considered that temperature balance is required.

[0027] If the voltage difference, SOC difference or temperature difference exceeds the corresponding equalization threshold, it is determined that the battery pack needs to be equalized; otherwise, it is considered that the battery pack is in a balanced state and does not need to be equalized.

[0028] For voltage balancing, select the single battery with the lowest voltage as the target balancing single battery, and select the single battery with the highest voltage as the source single battery. For SOC balancing, select the single battery with the lowest SOC as the target balancing single battery, and select the single battery with the highest SOC as the source single battery. For temperature balancing, select the single battery with the lowest temperature as the target balancing single battery, and select the single battery with the highest temperature as the source single battery.

[0029] If voltage imbalance, SOC imbalance and temperature imbalance exist at the same time, the target balanced single battery and the source single battery are selected according to the principle of voltage balance first, SOC balance second and temperature balance last.

[0030] According to the determined target balancing single battery and source single battery, control the corresponding balancing module in the balancing circuit to work. Use PWM modulation, PFM modulation or other modulation methods to control the power switch tube in the balancing module to turn on or off to achieve energy transfer from the source single battery to the target balancing single battery. According to the SOC value of the source single battery and the SOC value of the target balancing single battery, dynamically adjust the transmission current and transmission time of the balancing circuit to avoid over-discharge or over-charging. During the balancing process, monitor the discharge current, discharge voltage and temperature of the source single battery, as well as the charging current, charging voltage and temperature of the target balancing single battery in real time to ensure the safety and reliability of the balancing process.

[0031] In an optional embodiment, Determining the target balancing single battery in the battery pack and the source single battery in the balancing circuit according to the voltage value, the SOC value and the temperature value includes: For each single battery in the battery pack, extract its voltage value, SOC value and temperature value to form a sample data set; Performing cluster analysis on the sample data set using a fuzzy c-means clustering algorithm to obtain a membership matrix and a cluster center matrix in which each sample point belongs to a different cluster center; According to the membership matrix, the average voltage value, the average SOC value and the average temperature value of the sample points in each cluster center are calculated, and the average voltage value, the average SOC value and the average temperature value are used as clustering characteristic values ​​of the cluster center; For any single battery in the battery pack, the membership of the single battery to each cluster center is calculated according to the voltage value, SOC value and temperature value of the single battery, and the comprehensive evaluation index of the single battery is calculated according to the clustering characteristic value and the membership degree of each cluster center and the clustering weight value corresponding to the clustering characteristic value; The single storage battery with the smallest comprehensive evaluation index is selected as the target balancing single storage battery, and the single storage battery with the largest comprehensive evaluation index is selected as the source single storage battery.

[0032] In an optional embodiment, The comprehensive evaluation index of the single battery is calculated based on the clustering characteristic value and the degree of membership of each cluster center and the clustering weight value corresponding to the clustering characteristic value, including:

[0033] Among them, S i represents the comprehensive evaluation index of the ith single battery, C represents the number of cluster centers, u ij represents the membership degree of the i-th battery cell to the j-th cluster center, w1, w2, w3 represent the cluster weight values ​​corresponding to the voltage value, SOC value and temperature value respectively, V j , SOC j 、T j They represent the average voltage, average SOC and average temperature of the jth cluster center, respectively. i , SOC i 、T i Respectively represent the voltage value, SOC value and temperature value of the i-th single battery, SOC max , SOC min Respectively represent the maximum and minimum SOC values ​​of all single batteries, V max 、V minRespectively represent the maximum and minimum voltage values ​​of all single battery cells, T max , T min They respectively represent the maximum and minimum temperature values ​​of all single batteries.

[0034] Exemplarily, the voltage value, SOC value and temperature value of each single battery in the battery pack are collected by the BMS to construct an original sample data set. The original sample data is preprocessed, including data cleaning, outlier processing and data normalization, to obtain a standardized sample data set.

[0035] The standardized sample data set is clustered using the fuzzy c-means clustering algorithm, and the appropriate number of clusters and termination conditions are set. Through iterative optimization, the membership matrix and cluster center matrix of each sample point belonging to different cluster centers are obtained. The membership matrix indicates the degree to which each sample point belongs to each cluster center, and the cluster center matrix indicates the position of each cluster center in the sample space.

[0036] According to the membership matrix, the average voltage value, average SOC value and average temperature value of the sample points in each cluster center are calculated. The average voltage value, average SOC value and average temperature value are used as the clustering feature values ​​of the cluster center to reflect the overall characteristics of the single battery group represented by the cluster center.

[0037] For any single battery in the battery pack, extract its voltage value, SOC value and temperature value. According to the voltage value, SOC value and temperature value of the single battery, calculate the membership of the single battery to each cluster center. Combine the clustering eigenvalue and membership of each cluster center, and the clustering weight value corresponding to the preset clustering eigenvalue, calculate the comprehensive evaluation index of the single battery. The comprehensive evaluation index reflects the balanced state of the single battery relative to the entire battery pack. The smaller the index value, the more the single battery needs balanced charging, and the larger the index value, the more suitable the single battery is as the energy source of the balanced circuit.

[0038] Find the single battery with the smallest comprehensive evaluation index in the battery group and use it as the target balanced single battery, indicating that this single battery is most in need of balanced charging. Find the single battery with the largest comprehensive evaluation index in the battery group and use it as the source single battery, indicating that this single battery is most suitable as the energy source of the balancing circuit to provide balanced electric energy for the target balanced single battery.

[0039] According to the selected target balancing single battery and source single battery, control the corresponding switches and power electronic devices in the balancing circuit to achieve energy transmission and balancing. During the balancing process, monitor the status of the single battery in real time, and dynamically adjust the balancing strategy and parameters as needed to ensure the safety and effectiveness of the balancing process. After the balancing is completed, re-evaluate the balancing status of the battery group, and decide whether to continue the next round of balancing based on the evaluation results until the preset balancing target is reached.

[0040] The above detailed technical solution uses the fuzzy c-means clustering algorithm to perform cluster analysis on the single cells in the battery pack. By calculating the comprehensive evaluation index, the single cell that needs the most balanced charging is selected as the target balanced single cell, and the single cell that is most suitable as the energy source is selected as the source single cell, so as to realize the active balanced control of the battery pack. This solution comprehensively considers multiple characteristic quantities such as the voltage, SOC and temperature of the single cell, and can more comprehensively and accurately evaluate the balanced state of the single cell. At the same time, the fuzzy clustering method is used to effectively deal with the uncertainty and ambiguity of the battery pack state, and improve the robustness and adaptability of the balanced decision. Compared with the traditional balanced method, this solution has the advantages of high balanced efficiency, fast balanced speed and high control accuracy, which can effectively extend the service life of the battery pack and improve the energy utilization efficiency and mileage of the whole vehicle.

[0041] S102 controls the balancing circuit to transmit the electric energy of the source single battery to the target balanced single battery through the balancing circuit to achieve voltage balance between the target balanced single battery and other single batteries in the battery pack; In an optional embodiment, Controlling the balancing circuit to transmit the electric energy of the source single storage battery to the target balancing single storage battery through the balancing circuit to achieve voltage balancing between the target balancing single storage battery and other single storage batteries in the battery group includes: The balancing circuit includes a bidirectional DC-DC converter, which includes two power switch tubes, two inductors and one capacitor. By controlling the conduction state of the power switch tubes, bidirectional transmission of electric energy between the source single storage battery and the target balancing single storage battery is achieved; The method of controlling the equalization circuit comprises: According to the voltage error of the target balanced single battery, a given value of the transmission current is calculated through an outer voltage control loop, and the outer voltage control loop adopts a PI controller; According to the given value and the actual value of the transmission current, the conduction duty cycle of the power switch tube is adjusted through an inner current control loop, and the inner current control loop adopts a proportional controller; During the process of transmitting electric energy, the discharge current of the source single storage battery and the charge current of the target balancing single storage battery are monitored in real time; When the discharge current of the source single battery exceeds a preset safety threshold, reducing the transmission current or stopping the discharge of the source single battery; When the charging current of the target balancing single storage battery exceeds a preset safety threshold, the transmission current is reduced or the charging of the target balancing single storage battery is stopped.

[0042] In an optional embodiment, The outer voltage control loop adopts a PI controller, and the transfer function corresponding to the PI controller is as follows:

[0043] Among them, G v represents the transfer value corresponding to the transfer function s of the PI controller, K pv represents the proportional coefficient of the voltage controller, T iv represents the integral time constant of the voltage controller, T fv represents the filtering time constant of the voltage controller, τv represents the lag time of the voltage control loop; The inner current control loop adopts a proportional controller, and the transfer function corresponding to the proportional controller is as follows:

[0044] Among them, G i represents the transfer value of the proportional controller, K pi represents the proportionality factor of the current controller, K ii Indicates the integral coefficient of the current controller, K di represents the differential coefficient of the current controller, T fi Indicates the filter time constant of the current controller.

[0045] Exemplarily, the balancing circuit adopts a bidirectional DC-DC converter topology to realize bidirectional transmission of electric energy between the source single battery and the target balancing single battery. The bidirectional DC-DC converter includes two power switch tubes, two inductors and a capacitor. The power switch tube adopts a field effect tube (MOSFET) or an insulated gate bipolar transistor (IGBT) to realize high-frequency switching control. The inductor is used to limit the current ripple, reduce the switching loss and improve the transmission efficiency. The capacitor is used to suppress the voltage ripple, stabilize the output voltage and ensure the safety of the transmission process.

[0046] A dual closed-loop control strategy is adopted, with the outer layer being the voltage control loop and the inner layer being the current control loop, to achieve accurate voltage tracking and current limiting. The voltage error is calculated based on the voltage set value and actual value of the target balanced single battery. A PI controller is used to calculate the set value of the transmission current based on the voltage error: The current error is calculated based on the given value and actual value of the transmission current. A proportional controller is used to adjust the on-duty cycle of the power switch tube according to the current error. A PWM signal is generated based on the duty cycle to control the on and off of the power switch tube to achieve current tracking and energy transmission.

[0047] In the process of transmitting electric energy, the discharge current of the source single battery and the charging current of the target balancing single battery are monitored in real time. The discharge current safety threshold of the source single battery and the charging current safety threshold of the target balancing single battery are set. When the discharge current of the source single battery exceeds the safety threshold, the discharge of the source single battery is stopped by reducing the given value of the transmission current or directly turning off the power switch tube to protect the safety of the source single battery.

[0048] When the charging current of the target balanced single battery exceeds the safety threshold, the charging of the target balanced single battery is stopped by reducing the given value of the transmission current or directly turning off the power switch tube to protect the safety of the target balanced single battery.

[0049] During the balancing process, the voltage of the target balancing single battery is monitored in real time. When the voltage of the target balancing single battery reaches a given value, or the SOC of the source single battery drops to the minimum allowable value, the balancing process is stopped and the power switch is turned off. After the balancing is completed, the BMS updates the status information of the battery pack and enters the next balancing cycle or other working mode.

[0050] The above detailed technical solution realizes bidirectional transmission of electric energy between the source single battery and the target balanced single battery through a bidirectional DC-DC converter, adopts a double closed-loop control strategy to achieve accurate voltage tracking and current limiting, and introduces current protection measures to ensure the safety and reliability of the balancing process. Compared with the traditional passive balancing method, this solution has the advantages of high energy utilization efficiency, fast balancing speed, and high control accuracy, and is suitable for the balancing needs of large-capacity and high-power battery packs.

[0051] S103. In the process of transmitting electric energy, the discharge current, discharge voltage and temperature of the source single battery, and the charging current, charging voltage and temperature of the target balanced single battery are monitored in real time, and the transmission current and transmission time of the balanced circuit are dynamically adjusted by adjusting the working state of the corresponding balanced module in the balanced circuit to avoid over-discharge of the source single battery and over-charge of the target balanced single battery; after the balancing is completed, it is determined whether the voltage, SOC value and temperature of each single battery in the battery group are balanced, and if so, the balancing is stopped.

[0052] For example, during the process of transmitting electric energy, the discharge current, discharge voltage and temperature of the source single battery, and the charging current, charging voltage and temperature of the target balanced single battery are monitored in real time by sensors in the balancing circuit. According to the monitored data, the working state of the corresponding balancing module is dynamically adjusted by the controller in the balancing circuit, including the transmission current and transmission time.

[0053] The regulation amount of the transmission current is calculated according to the discharge current of the source single battery and the charging current of the target balancing single battery; the given value of the transmission current is updated according to the regulation amount; and the actual transmission current tracks the given value by adjusting the conduction duty cycle of the power switch tube in the balancing circuit.

[0054] The adjustment amount of the transmission time is calculated according to the discharge voltage of the source single battery and the charge voltage of the target balancing single battery; the given value of the transmission time is updated according to the adjustment amount; and the actual transmission time tracks the given value by setting the conduction time of the power switch tube in the balancing circuit.

[0055] To avoid overdischarge of the source single battery, when the discharge voltage of the source single battery is lower than the preset discharge cut-off voltage, the discharge of the source single battery is stopped and the connection between the source single battery and the balancing circuit is cut off. To avoid overcharging of the target balancing single battery, when the charging voltage of the target balancing single battery is higher than the preset charging cut-off voltage, the charging of the target balancing single battery is stopped and the connection between the balancing circuit and the target balancing single battery is cut off.

[0056] During the discharge of the source single battery and the charging of the target balancing single battery, their temperatures are monitored in real time. When the temperature exceeds the preset safety threshold, the power transmission is stopped, the corresponding connection is cut off, and the thermal management system is started for cooling.

[0057] After balancing is completed, the BMS regularly monitors the status of the battery pack, including the voltage, SOC value and temperature of the single battery. When the balancing status of the battery pack changes and no longer meets the conditions for balancing completion, the balancing process is restarted to maintain the consistency and stability of the battery pack. During battery operation and charging and discharging, the BMS adjusts the balancing strategy and parameters in a timely manner according to the usage and environmental conditions of the battery pack to ensure the optimization of the balancing effect.

[0058] In an optional embodiment, The method further comprises: During the process of transmitting electric energy, if the discharge current of the source single battery is greater than a preset maximum discharge current threshold, or the discharge voltage of the source single battery is less than a preset minimum discharge voltage threshold, or the temperature of the source single battery is greater than a preset maximum temperature threshold, the discharge of the source single battery is stopped; During the process of transmitting electric energy, if the charging current of the target balancing single storage battery is greater than a preset maximum charging current threshold, or the charging voltage of the target balancing single storage battery is greater than a preset maximum charging voltage threshold, or the temperature of the target balancing single storage battery is greater than a preset maximum temperature threshold, the charging of the target balancing single storage battery is stopped.

[0059] Exemplarily, the setting of the maximum discharge current threshold and the maximum charge current threshold should comprehensively consider the rated discharge current of the single battery, the current transmission capacity of the equalization circuit, and the safety margin of the system, and is usually 0.5 to 0.8 times the rated value. The setting of the minimum discharge voltage threshold should be higher than the discharge cut-off voltage of the single battery, usually 1.05 to 1.1 times the discharge cut-off voltage, to avoid irreversible capacity loss and performance degradation caused by over-discharge. The setting of the maximum charge voltage threshold should be lower than the charge cut-off voltage of the single battery, usually 0.95 to 0.98 times the charge cut-off voltage, to avoid safety hazards such as gas precipitation and electrolyte decomposition caused by overcharging.

[0060] The maximum temperature threshold should be set lower than the thermal runaway temperature of the single battery, usually 50~60℃, to avoid accelerated aging, capacity decay and safety accidents caused by high temperature.

[0061] When the source single battery or the target balanced single battery has a discharge / charge abnormality, the BMS should handle the abnormality in a timely manner, record the abnormal information, and send a warning to the host computer or user when necessary. For abnormalities of different types and severity, the BMS should take corresponding processing measures, including suspending balancing, reducing transmission current, replacing balancing objects, entering fault protection state, etc. After the abnormality is eliminated, the BMS should evaluate the status of the battery pack and decide whether to resume the balancing process. If the abnormality causes the battery pack to deteriorate in performance or cause safety hazards, maintenance or replacement should be carried out to ensure the reliable operation of the system.

[0062] The above detailed technical solution sets the threshold conditions for source single battery discharge protection and target balanced single battery charge protection, monitors key parameters in real time, stops abnormal discharge / charge behavior in time, and ensures the safety and reliability of the balancing process. At the same time, it provides a complete abnormal handling and recovery mechanism for abnormal situations to improve the fault tolerance and stability of the system. This solution can effectively prevent overcharging, overdischarging, overheating and other problems during the balancing process, extend the service life of the battery pack, and ensure the safe operation of the vehicle.

[0063] Embodiment 2: Figure 2 FIG. 1 is a structural diagram of an active online voltage equalization system based on battery circulation of an embodiment of the present invention, such as Figure 2 As shown, the system comprises: The first unit is used to obtain the voltage value, SOC value and temperature value of each single storage battery in the battery pack, and judge whether the battery pack needs to be balanced based on the preset voltage balance threshold, SOC balance threshold and temperature balance threshold; if so, determine the target balanced single storage battery in the battery pack and the source single storage battery in the balancing circuit according to the voltage value, SOC value and temperature value; The second unit is used to control the balancing circuit to transmit the electric energy of the source single storage battery to the target balancing single storage battery through the balancing circuit, so as to achieve voltage balancing between the target balancing single storage battery and other single storage batteries in the battery group; The third unit is used to monitor the discharge current, discharge voltage and temperature of the source single battery, and the charging current, charging voltage and temperature of the target balanced single battery in real time during the process of transmitting electric energy, and dynamically adjust the transmission current and transmission time of the balanced circuit by adjusting the working state of the corresponding balanced module in the balanced circuit to avoid over-discharge of the source single battery and over-charge of the target balanced single battery; after the balancing is completed, it is determined whether the voltage, SOC value and temperature of each single battery in the battery group are balanced, and if so, the balancing is stopped.

[0064] Embodiment 3: An electronic device is provided, comprising: processor; a memory for storing processor-executable instructions; The processor is configured to call the instructions stored in the memory to execute the aforementioned method.

[0065] Embodiment 4: A computer-readable storage medium is provided, on which computer program instructions are stored. When the computer program instructions are executed by a processor, the aforementioned method is implemented.

[0066] The present invention may be a method, an apparatus, a system and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for executing various aspects of the present invention.

[0067] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. An active online voltage equalization method based on battery circulation of a battery, characterized in that: It includes the following steps: S1. Obtain the voltage value, SOC value and temperature value of each single battery in the battery pack, and determine whether the battery pack needs to be balanced based on the preset voltage balance threshold, SOC balance threshold and temperature balance threshold; If so, determine the target balancing single battery in the battery pack and the source single battery in the balancing circuit according to the voltage value, the SOC value and the temperature value; S2, controlling the balancing circuit to transmit the electric energy of the source single battery to the target balancing single battery through the balancing circuit, so as to achieve voltage balancing between the target balancing single battery and other single batteries in the battery pack; S3. During the process of transmitting electric energy, the discharge current, discharge voltage and temperature of the source single battery, and the charging current, charging voltage and temperature of the target balanced single battery are monitored in real time, and the transmission current and transmission time of the balanced circuit are dynamically adjusted by adjusting the working state of the corresponding balanced module in the balanced circuit to avoid over-discharge of the source single battery and over-charge of the target balanced single battery; After the balancing is completed, it is determined whether the voltage, SOC value and temperature of each single battery in the battery pack are balanced. If so, the balancing is stopped.

2. An active online voltage equalization method based on battery circulation according to claim 1, characterized in that: In S1, the terminal voltage, current and temperature parameters of each single battery are measured in real time through the acquisition circuit in the battery management system; the SOC value of each single battery is estimated based on the measured voltage, current and temperature data using Kalman filtering, extended Kalman filtering or particle filtering algorithm; the acquired voltage value, SOC value and temperature value are stored in the memory of the BMS for subsequent balancing judgment and control.

3. An active online voltage equalization method based on battery circulation according to claim 1, characterized in that: In S1, it is determined whether the battery pack needs to be balanced, and a voltage balance threshold is set. When the absolute value of the voltage difference between any two single batteries in the battery pack exceeds the voltage balance threshold, it is considered that voltage balance is required; an SOC balance threshold is set. When the absolute value of the SOC difference between any two single batteries in the battery pack exceeds the SOC balance threshold, it is considered that SOC balance is required; a temperature balance threshold is set. When the absolute value of the temperature difference between any two single batteries in the battery pack exceeds the temperature balance threshold, it is considered that temperature balance is required; If the voltage difference, SOC difference or temperature difference exceeds the corresponding equalization threshold, it is determined that the battery pack needs to be equalized; Otherwise, it is considered that the battery pack is in balanced state and does not need to be balanced; For voltage balancing, the single battery with the lowest voltage is selected as the target balancing single battery, and the single battery with the highest voltage is selected as the source single battery; For SOC balancing, the single battery with the lowest SOC is selected as the target balancing single battery, and the single battery with the highest SOC is selected as the source single battery; For temperature balancing, the single battery with the lowest temperature is selected as the target balancing single battery, and the single battery with the highest temperature is selected as the source single battery; If voltage imbalance, SOC imbalance and temperature imbalance exist at the same time, the target balanced single battery and the source single battery are selected according to the principle of voltage balance first, SOC balance second and temperature balance last; According to the determined target balanced single storage battery and source single storage battery, control the corresponding balanced module in the balanced circuit to work; Using PWM modulation, PFM modulation or other modulation methods to control the power switch tube in the balancing module to turn on or off, so as to realize the energy transfer from the source single battery to the target balancing single battery; According to the SOC value of the source single battery and the SOC value of the target balanced single battery, the transmission current and transmission time of the balancing circuit are dynamically adjusted to avoid over-discharge or over-charging; during the balancing process, the discharge current, discharge voltage and temperature of the source single battery, as well as the charging current, charging voltage and temperature of the target balanced single battery are monitored in real time to ensure the safety and reliability of the balancing process.

4. An active online voltage equalization method based on battery circulation according to claim 1, characterized in that: In S1, determining the target balancing single battery in the battery pack and the source single battery in the balancing circuit according to the voltage value, SOC value and temperature value includes: For each single battery in the battery pack, extract its voltage value, SOC value and temperature value to form a sample data set; The fuzzy c-means clustering algorithm is used to cluster the sample data set to obtain the membership matrix and cluster center matrix of each sample point belonging to different cluster centers; According to the membership matrix, the average voltage value, average SOC value and average temperature value of the sample points in each cluster center are calculated, and the average voltage value, average SOC value and average temperature value are used as the clustering characteristic values ​​of the cluster center; For any single battery in the battery pack, the membership of the single battery to each cluster center is calculated according to the voltage value, SOC value and temperature value of the single battery, and the comprehensive evaluation index of the single battery is calculated according to the clustering characteristic value and membership degree of each cluster center and the clustering weight value corresponding to the clustering characteristic value; The single battery with the smallest comprehensive evaluation index is selected as the target balancing single battery, and the single battery with the largest comprehensive evaluation index is selected as the source single battery.

5. An active online voltage equalization method based on battery circulation according to claim 4, characterized in that: The comprehensive evaluation indexes of the single battery are calculated based on the clustering eigenvalues ​​and membership degrees of each cluster center and the clustering weight values ​​corresponding to the clustering eigenvalues, including: ； Among them, S i represents the comprehensive evaluation index of the ith single battery, C represents the number of cluster centers, u ij represents the membership degree of the i-th battery cell to the j-th cluster center, w1, w2, w3 represent the cluster weight values ​​corresponding to the voltage value, SOC value and temperature value respectively, V j , SOC j 、T j They represent the average voltage, average SOC and average temperature of the jth cluster center, respectively. i , SOC i 、T i Respectively represent the voltage value, SOC value and temperature value of the i-th single battery, SOC max , SOC min Respectively represent the maximum and minimum SOC values ​​of all single batteries, V max 、V min Respectively represent the maximum and minimum voltage values ​​of all single battery cells, T max 、T min They respectively represent the maximum and minimum temperature values ​​of all single batteries.

6. An active online voltage equalization method based on battery circulation according to claim 1, characterized in that: In S2, the method for controlling the equalization circuit includes: According to the voltage error of the target balanced single battery, the given value of the transmission current is calculated through the outer voltage control loop, and the outer voltage control loop adopts a PI controller; According to the given value and actual value of the transmission current, the conduction duty cycle of the power switch tube is adjusted through the inner current control loop, and the inner current control loop adopts a proportional controller; During the transmission of electric energy, the discharge current of the source single battery and the charging current of the target balancing single battery are monitored in real time; When the discharge current of the source single battery exceeds a preset safety threshold, the transmission current is reduced or the discharge of the source single battery is stopped; When the charging current of the target balancing single storage battery exceeds a preset safety threshold, the transmission current is reduced or the charging of the target balancing single storage battery is stopped.

7. An active online voltage equalization method based on battery circulation according to claim 6, characterized in that: The outer voltage control loop uses a PI controller, and the transfer function corresponding to the PI controller is as follows: ； Among them, G v represents the transfer value corresponding to the transfer function s of the PI controller, K pv represents the proportional coefficient of the voltage controller, T iv represents the integral time constant of the voltage controller, T fv represents the filtering time constant of the voltage controller, τv represents the lag time of the voltage control loop; The inner current control loop uses a proportional controller, and the transfer function corresponding to the proportional controller is as follows: ； Among them, G i represents the transfer value of the proportional controller, K pi represents the proportionality factor of the current controller, K ii Indicates the integral coefficient of the current controller, K di represents the differential coefficient of the current controller, T fi Indicates the filter time constant of the current controller.

8. An active online voltage equalization method based on battery circulation according to claim 1, characterized in that: S3 specifically includes the following processes: During the process of transmitting electric energy, the discharge current, discharge voltage and temperature of the source single battery, as well as the charging current, charging voltage and temperature of the target balanced single battery are monitored in real time through the sensors in the balancing circuit; according to the monitored data, the working state of the corresponding balancing module, including the transmission current and transmission time, is dynamically adjusted through the controller in the balancing circuit; Calculate the adjustment amount of the transmission current according to the discharge current of the source single storage battery and the charging current of the target balancing single storage battery; updating a given value of the transmission current according to the adjustment amount; By adjusting the on-duty ratio of the power switch tube in the balancing circuit, the actual transmission current is made to track the given value; Calculate the adjustment amount of the transmission time according to the discharge voltage of the source single storage battery and the charge voltage of the target balancing single storage battery; updating a given value of the transmission time according to the adjustment amount; By setting the conduction time of the power switch tube in the balancing circuit, the actual transmission time can track the given value; To avoid overdischarge of the source single battery, when the discharge voltage of the source single battery is lower than the preset discharge cut-off voltage, the discharge of the source single battery is stopped and the connection between the source single battery and the balancing circuit is cut off; to avoid overcharging of the target balancing single battery, when the charging voltage of the target balancing single battery is higher than the preset charging cut-off voltage, the charging of the target balancing single battery is stopped and the connection between the balancing circuit and the target balancing single battery is cut off; During the process of source single battery discharging and target balanced single battery charging, their temperatures are monitored in real time. When the temperature exceeds the preset safety threshold, the transmission of power is stopped, the corresponding connection is cut off, and the thermal management system is started for cooling. After the equalization is completed, the BMS regularly monitors the status of the battery pack, including the voltage, SOC value and temperature of the single battery; when the equalization status of the battery pack changes and no longer meets the conditions for the completion of equalization, the equalization process is restarted to maintain the consistency and stability of the battery pack; During battery operation and charging and discharging, BMS adjusts the balancing strategy and parameters in a timely manner according to the usage and environmental conditions of the battery pack to ensure the optimization of the balancing effect.

9. An active online voltage equalization method based on battery circulation according to claim 8, characterized in that: S3 also includes the following processes: During the process of transmitting electric energy, if the discharge current of the source single battery is greater than a preset maximum discharge current threshold, or the discharge voltage of the source single battery is less than a preset minimum discharge voltage threshold, or the temperature of the source single battery is greater than a preset maximum temperature threshold, the discharge of the source single battery is stopped; During the process of transmitting electric energy, if the charging current of the target balancing single battery is greater than the preset maximum charging current threshold, or the charging voltage of the target balancing single battery is greater than the preset maximum charging voltage threshold, or the temperature of the target balancing single battery is greater than the preset maximum temperature threshold, the charging of the target balancing single battery is stopped.

10. An active online voltage equalization system based on battery circulation of a battery, characterized in that: It includes: The first unit is used to obtain the voltage value, SOC value and temperature value of each single battery in the battery pack, and determine whether the battery pack needs to be balanced based on a preset voltage balance threshold, SOC balance threshold and temperature balance threshold; If so, determine the target balancing single battery in the battery pack and the source single battery in the balancing circuit according to the voltage value, the SOC value and the temperature value; The second unit is used to control the balancing circuit to transmit the electric energy of the source single storage battery to the target balancing single storage battery through the balancing circuit, so as to achieve voltage balancing between the target balancing single storage battery and other single storage batteries in the battery pack; The third unit is used to monitor the discharge current, discharge voltage and temperature of the source single battery, and the charging current, charging voltage and temperature of the target balanced single battery in real time during the process of transmitting electric energy, and dynamically adjust the transmission current and transmission time of the balanced circuit by adjusting the working state of the corresponding balanced module in the balanced circuit to avoid over-discharge of the source single battery and over-charge of the target balanced single battery; After the balancing is completed, it is determined whether the voltage, SOC value and temperature of each single battery in the battery pack are balanced. If so, the balancing is stopped.

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