Research On Battery Equalization Technique Of Electric Vehicle Battery Pack Based On Reasoning Model Of Credibility Factor

Battery equalization technique is an important way to relieve the battery inconsistency problem,which can improve the capability of battery pack.Currently,the criterion of battery equalization is still based on parameters such as voltage,state of charge(SOC),and remaining capacity.However,due to the uncertainty and coupling effect of internal and external environment,there has always been great disagreement about balancing target and degree criterion.The uncertainty and fuzziness of balancing judgments affect the effect and stability of the equalization system and hinder the practical application of equalization technique.Therefore,the dissertation proposes a new type of equalization method by making the terminal voltage and SOC as a comprehensive balancing judgment.Firstly,the thesis studies the performance parameters and their variation,analyzes the cause,the performance and impact of inconsistency.The comparatively studies of the common balancing target decides to estimate balancing target and degree by the terminal voltage and SOC.Secondly,based on the analysis of the traditional balancing method,the article take the terminal voltage and SOC as the statistic,and proposes the concept of imbalance credibility.By the model of credibility factor,the inconsistency of the terminal voltage and SOC are combined to credibility factor of Overall Imbalance Degree,which can characterize the battery's overall energy status,and determine the inconsistency of the battery state.In the process of charging and discharging,the voltage and SOC of the battery are detected,and their imbalance credibility factor are reduced by controlling the battery imbalance credibility factor so as to improve the energy efficiency of the battery pack.Then through the analysis of the existing active equalization topology,develops a new equalization structure based on the single-core transformer and bidirectional Cuk circuit.This structure divides the equalization operation into two groups: intra-group equalization and inter-group equalization.The state of pack and module coefficient are characterized by overall imbalance credibility factor and module coefficient,so that they can determine the equalization operation of all layers and achieve packet equalization.Finally,the thesis validates the equalization scheme through independently designed experimental platform.The comparative experiment shows the feasibility of the new equalization method.It can reduce the difference between the voltage and the SOC of the battery pack and improve the energy efficiency of the battery pack.