SOC Estimation For Battery Management System

With the development of technology and the environment pollution becoming more and more serious,for the purpose of reducing the dependence on non-renewable energy sources,such as coal and petroleum,and alleviating the energy crisis and pollution problem,the new energy industry is encouraged to develop rapidly.New energy vehicle is an important part of the new energy industry.Currently;as an energy storage device,the lithium battery serves as a core component of a pure electric automobile at present.Lithium battery’s estimation of state of charge(SOC)is of great significance to Batter Management System(BMS)to improve battery life and vehicle range,therefore,lithium battery’s estimation of state of charge(SOC)has become a hot topic in the present study.According to the established battery physical model,this paper selects the Kalman filtering method based on fuzzy control to make real-time online estimation of the battery’s SOC.The Federal Urban Driving(USC,FUDS)and Hybrid Pulse Power Characterization Test(HPPC)are used to verify the rationality and accuracy of the proposed algorithm.The main contents of this paper are as follows:First of all,this paper mainly introduces the current development status of lithium battery from three aspects which are battery model,SOC estimation method and battery management system.Secondly,we set up the battery experiment platform,and chose 9keaz64aml chip to design the hardware experiment circuit to develop the upper computer,and then conducted charge and discharge experiments on batteries.Thirdly,the main factors that influence the calculation accuracy of SOC were analyzed,and the physical model including internal resistance,RC and first-order model of lithium battery were established.Besides,we built the corresponding simulation platform based on Matlab/Simulink software,by comparing the simulation data and experimental data,determined the battery model to the first order model,and selected SOC estimation method for the Kalman estimation method based on fuzzy control.Finally,the parameters that the open-circuit voltage of the lithium battery,the internal resistance of the lithium battery,the polarization internal resistance and the polarization capacitance of the lithium battery under different temperatures and different SOC conditions were obtained by carrying out parameter identification on lithium battery experimental data.A first-order model of the lithium battery was corrected through these parameters.on the basis of MATLAB/simulink software,we built the simulation platform and verified the reasonability and the accuracy of the kalman estimation method of the fuzzy system.