Research On Intelligent Charging Technology For Vehicle Power Lithium Battery

With the constant consumption of fossil energy and the increasing pollution of the environment,a traditional fuel vehicle ban schedule was formulated in China,it was a trend of social development to use the electric vehicles.At present,the problems of electric vehicles were small charging efficiency,short mileage and low service life,and it was hard to meet the consumer's driving experience.In the existing charging technologies,the charging mode was single and the parameter was fixed.In the charging process,the real states and the charging characteristics of battery were not considered.And the charging efficiency and service life were affected.In this thesis,the charging characteristics of lithium battery were analyzed,and the intelligent charging technology of lithium battery was researched.According to the states of the charging process,the corresponding control strategy was taken.Under the condition of protecting service life and charging safety of battery,this method was helpful to improve the charging efficiency and the charging effect.This research work was very important significance for the promotion of electric vehicles.The research contents and innovative work of this thesis were as follows:(1)The charging process of lithium battery was a complex electrochemical reaction process,and the effect of charging was influenced by many factors.In this thesis,the performance parameters,the working principle,the battery model and the characteristics of charging and discharging were studied.With the simulation of 2RC equivalent circuit model,it was found that the charging process of lithium battery was accompanied by the characteristics of hysteresis,polarization and temperature rise,these phenomena should be take into account in the charging process.(2)Based on the charging characteristics of lithium battery,a four-stage intelligent charging method of lithium battery was proposed.In this thesis,the Mas charge theory and four kind of typical charging methods were studied,the charging effect was diverse in different charging stages.According to the states of charging and the actual characteristics,the optimum charging curve was divided into preprocessing,constant current charging,curve tracking charging and pulse charging,the corresponding control strategies were respectively taken in different stages.The fast calibration method and extended Kalman filter algorithm were used to estimate SOC,and the capacity of lithium battery was obtained.(3)The experimental platform for the charging system of lithium battery was designed and built,and the experiments were carried out.Firstly,the power circuit,control circuit,sampling circuit,equalization circuit and man-machine interface of the charging system were designed and made,the software control program was compiled,and the system joint debugging was implemented.Then the four-stage intelligent charging method was tested,and the value of voltage and current was monitored in real time during charging.By observing the experimental phenomenon,the charging method was feasible.Finally,the real circuit of 2RC battery model was built by separating components.The dynamic effect of charging process was observed,and the experimental waveform was consistent with the simulation results.