Research On Energy Balancing Control Strategy Of Electric Vehicle Battery Pack Based On Fuzzy Threshold

As the battery inconsistency problem makes the battery capacity utilization is low,the cycle life is not as good as the single cell,the balanced management is the effective way to improve the battery inconsistency,has important research significance.However,the current equilibrium control strategy is in the initial stage,the precision of the control process is relatively rough,and the factors considered when the equilibrium control parameters are set in the equilibrium process are not comprehensive,which makes the equilibrium strategy difficult to achieve good results in practical application,In the process of improving the equilibrium effect,there are many problems that need to be improved and solved.Therefore,the dissertation study the optimization of the parameters such as the control parameters and the equalization process based on the traditional equilibrium strategy with the working voltage as the equilibrium target.Firstly,the main factors of battery inconsistency and the solution are discussed.The advantages and disadvantages of different equalization variables for equalization control are discussed,the equilibrium target variable is determined;Then,the characteristics and application of the main battery equivalent circuit model are compared and analyzed.The equivalent circuit model of the battery is chosen as the battery equivalent circuit model to analyze the working state of the battery.The characteristics of the main performance parameters of lithiumion batteries and their variation were analyzed experimentally under different charge and discharge conditions.Secondly,the paper analyzes the variation law of the working voltage during the process of charging and discharging the battery,finds out the main factors that affect the working voltage change of the lithium ion battery,establishes the corresponding relation formula through the equivalent circuit model,and puts forward the idea of dynamic fuzzy threshold,The fuzzy control algorithm is used to quantitatively analyze the influencing factors,In the whole process of charging and discharging the battery pack,The operating voltage difference between the individual cells is controlled within a reasonable range.And then design the equalization control strategy for the whole process according to the goal.Based on the proposed equilibrium strategy,the main parameters are identified before the battery is working.In the process of charging and discharging of the battery pack,the battery operating voltage is detected and the equilibrium threshold of this stage is calculated according to the identified parameters.In this way,the inconsistency judgment and the equalization operation are carried out.Combined with the equalization + hysteresis control method,The voltage tends to be consistent.Finally,the equilibrium strategy is tested by experiment.The performance of the optimized equalization strategy is evaluated from the voltage during the discharge of the battery pack and the final voltage distribution at the end of the discharge and the ratio of the remaining capacity of the discharge and the number of equalization movements,compared with the traditional fixed-threshold voltage-center equalization strategy.Through the comparative analysis of the two strategies,it is shown that the equilibrium strategy designed in this paper can effectively improve the energy utilization of the battery and reduce the energy consumption caused by the misjudgment of the battery inconsistency.