Research On Lithium Ion Battery Management System For Electric Vehicle

In order to reduce greenhouse gas emissions and avoid energy shortage,green energy power and clean cars have attracted much attention.As the power source of electric vehicles,lithium battery has many advantages compared with other energy storage devices,including energy density,health status,etc.,which makes lithium battery have a broad development prospect in the application of energy storage,but due to its own limitations,it cannot meet the needs of practical applications.As a result,it is necessary to connect them into battery packs,and the design of the balanced structure leads to inconsistencies between battery packs,which limits the charging and discharging process.During the charging and discharging process,a large amount of heat will be generated inside the battery,which will accumulate over time,leading to the intensification of electrochemical reactions.Therefore,it is very important to develop efficient,scientific and reasonable lithium battery management system for the performance of battery pack.Taking lithium ion as the research object,this paper will carry out research from three aspects: SOC estimation,balance control and thermal management,and explore the problems of balance and heat dissipation under the condition of SOC inconsistency of single battery.Specific research contents are as follows:First,based on the comprehensive analysis results of applicability and performance,the second-order RC cell model was selected,and Recursive Least Squares(RLS)was used to identify the parameters of the cells online by using the measured data of UDDS working conditions as reference data.The results show that the algorithm has good feasibility.GA-LEM neural network algorithm is used to accurately estimate the SOC of battery.Simulation experiments prove that the algorithm has better accuracy than ELM,and the maximum error of the result is less than 2.6%.Secondly,Buck-Boost active balancing circuit topology was built,SOC was used as balancing variable,fuzzy logic control algorithm was used to control the input variable and output current was obtained with fuzzy domain assignment,so as to balance the battery pack quickly.The simulation model is established in MATLAB,and the equalization experiment is carried out under three working conditions respectively.The result shows that the equalization time under three working conditions is shortened by about 12.97% on average.Finally,in the case of inconsistent initial SOC of the battery pack,thermal management of the battery pack is carried out.A physical model of wind cooling and heat is built,and the two variables of the gap size of a single battery in the battery pack structure and the wind speed of the air inlet are compared and simulated separately,and the heat dissipation effect is analyzed.Considering the limited influence of air cooling on heat dissipation,a liquid cooling plate was installed to form a coupled air-liquid cooling thermal model.The flow rate of the coolant inlet and the initial temperature of the coolant at high temperature were compared and simulated separately,and the optimal combination in the thermal management experiment was obtained.