Research And Development Of Lithium Battery Management System Of The Pure Electric Vehicle

With the rapid development of global economy and the increasingly prominent problems of energy and environmental protection,electric vehicles with the advantages of zero emissions,good environmental protection and low energy consumption have become the main development direction of energy-saving and environmental protection green vehicles,and more and more attention by all countries in the world,and get rapid development in the 21 st century.Lithium-ion power battery is the bottle-neck of the development of electric vehicles,and battery management system(BMS)is a key technology to ensure the normal application of the power battery system.The efficient and well-functioning BMS can effectively use the power battery energy to make the power battery in the best working condition.Under the above background,this paper studies the battery management system of pure electric vehicles.The main work of the thesis includes the following aspects:(1)By analyzing various equivalent circuit models of lithium-ion batteries,a Thevenin equivalent circuit model is adopted and the model is built.Through SOC-OCV calibration experiment and high-order polynomial fitting function,it is determined that SOC and OCV have a certain proportion.The Thevenin circuit model was identified through multiple HPPC cycle charge and discharge experiments.(2)Aiming at the estimation problem of SOC(State of Charge,SOC)of lithium-ion battery packs,several typical SOC estimation methods are deeply analyzed.On this basis,combining the Thevenin equivalent circuit model and its identification parameters,the Matlab software was used to establish the EKF algorithm to estimate the SOC model of the lithium battery,and used it to estimate the SOC value of the lithium-ion battery,which verified the accuracy of the EKF estimation of the SOC of the lithium battery.(3)Through the analysis of the structure of electric vehicle BMS,a whole scheme of distributed BMS is adopted,and corresponding hardware and software are developed.The system uses the main control chip STM32f103vet6 to perform overall control of each functional module,to achieve battery pack charge and discharge management,battery information collection,fault detection,balance control and other functions.The MCU software of the main control board of the lower computer cooperates with the hardware circuit,ensuring the normal operation of the functions of the system.(4)By analyzing several typical balance control schemes,an actively combined balance scheme is proposed,and a brand new power battery energy balance structure and balance control strategy are designed.In order to verify the balanced effect of this scheme,an experimental platform for lithium battery management system was built and carried out.The experimental results show that the hybrid equalization scheme based on the SOC equalization strategy can effectively improve the service life of the battery pack and the range of electric vehicles.