Research On Equilibrium Method Of Power Battery Based On Fuzzy Comprehensive Evaluation System

In recent years,research and application of battery balancing technology has made great progress.However,in the balancing speed,balancing efficiency,balancing cost,charge and discharge time,expansion performance,balancing real-time,balancing accuracy,the degree of influence on battery life,the realization of balancing and other aspects,it is found that all kinds of balancing technology have different performance.It is of practical significance to seek the optimal battery balance scheme.In this thesis,the optimization of the balancing topology type is chosen as the starting point of the research,and from the perspective of multiple evaluation evaluates the type of balancing topology.Then,selecting the optimal estimation algorithm of SOC based on the optimal method,and improving the corresponding traditional balancing algorithm and constructing the simplest structure of the optimal balancing topology type based on the optimal balancing topology type further improve the overall performance of the balancing solution.Firstly,a comprehensive evaluation system of balancing technology based on fuzzy theory is established,which includes the evaluation model of the evaluation index and the mathematical model of the evaluation index,the evaluation index weighting model,the membership function and the establishment of the comprehensive evaluation function.among them:(1)Based on the analysis of the traditional balancing algorithm corresponding to the balancing topology type,the main factors influencing the balancing effect of the balancing topology type are obtained,and the balancing topology type evaluation index is extracted.(2)Based on the gray relational degree theory,the weight of the evaluation index is solved by the six experts scoring,and the validity of the weight selection is enhanced.(3)According to the ranking of the rank of the balancing topology in the evaluation index and the resolution of the membership degree,the membership function of the evaluation index is established to ensure the rationality of the membership function.Secondly,from the "software" point of view to enhance the comprehensive performance of the balancing program.This section includes two aspects:(1)Using the information contained in the comprehensive evaluation system of balancing topology,the traditional balancing algorithm is improved,and the traditional "peak-cutting" and "valley-filling" balancing algorithms are combined to establish a new "peak-filling" balancing algorithm.(2)Applying the balancing technology comprehensive evaluation system to the optimization of SOC estimation algorithm,an SOC estimation algorithm of extended Kalman filter based on first-order RC improved model of lithium ion cell is developed.Thirdly,with the simple structure,good operating performance,low operating energy consumption as a starting point,the balance of hardware system is designed,which from the "hardware" point of view to improve the overall performance of the balancing program.This section contains three aspects:(1)Using the knowledge of graph theory and permutation,all the balancing technology structures corresponding to the optimal balancing technology are listed.Using the feature that multi-winding transformer can simplify the connection relationship,the simplest structure of the balancing topology is established.(2)Using the feature of mosfet on-state resistance much lower than the Xiaoji diodes and mosfet body diode characteristics,the energy loss is reduced during the balancing process by synchronizing the rectification operation.(3)The single-cycle control technology makes the balancing input current constant,which improves the balance and controllability.Finally,the balancing strategy is introduced into the balancing hardware system,and an experiment for the series of battery cells is performed.The results show that the scheme is feasible and efficient.