The Research Of SOC Estimation And Active Equalization Control Strategy In BMS

With the depletion of resources,global warming,air pollution and other environmental problems becoming increasingly serious,electric vehicles have become the focus of national technical research as environmentally friendly transportation tools.Electric vehicles are powered by batteries.Therefore,battery management system is an important part of electric vehicle technology.Battery management system includes battery status information detection,balarked management,battery SOC(State of Charge)estimation and other functions.Battery management system can extend battery life,improve battery utilization and ensure battery safe and stable operation.Firstly,this paper designed the method of battery SOC estimation.Based on the conparison of different battery SOC estimation methods,the correction coefficient of current time integral method was used to estimate the SOC of battery.The correction coefficient of current time integral method has the advantages of simplicity and ease of implementation.Through the analysis of various factors affecting the estimation of battery SOC,temperature,self-discharge rate and discharge rate were considered to modify current time integral method.The accuracy of SOC estimation was improved.Building model in Matlab/Simulink and simulation proved that the correction coefficient of current time integral method could accurately estimate battery SOC.Secondly,this paper designed a battery active equalization control strategy.The battery had individual differences in the process of productioa The different working environment would lead to the inconsistency of the battery.Thereby it woukl shorten the battery life and reduce the battery utilization.In order to ensure the consistency of the battery,an active equalization method using constant current source was presented after comparing several battery equalization methods.Battery simulation model and equilibrium simulation model were built in Matlab/Simulink.The effectiveness of the equalization strategy was verified by simulation The experimental results showed that the equilibrium strategy could be operated reliably and stably in practice.Finally,this paper optimized the hardware platform and software function of the battery management system Single cell voltage acquisition circuit was improved,and the acquisition accuracy was obviously improved.The relay adhesion detection circuit and the acquisition unit detection circuit were designed,which would ensure stable operation of equalization unit,collection unit and other functional units.Through the joint debugging hardware and software and the car test,the results showed that the battery management system could run stably on the electric vehicle.