Research On Online Estimationn Algorithm Of SOC Of Ternary Lithium Ion Battery

With the energy crisis and environmental pollution continue to increase,the development of clean energy in the automotive industry has been put on the agenda,especially the storage equipment represented by lithium-ion batteries.In order to ensure the safety,stability and efficient and accurate requirements of lithium-ion battery operation,it is especially important to study its battery management system(BMS)in the field of new energy vehicles.Therefore,this article takes Sony's model of VTC6 18650 lithium-ion battery as the research object,using the second-order equivalent circuit as the mathematical model of the battery,using the new Will charge and discharge tester,Germany DSPACE1104 and other equipment as the test device for lithium ion battery.The platform aims to study the real-time accurate estimation method of SOC.The main contents of the thesis include:Firstly,the working principle and main battery performance parameters of lithium-ion battery are introduced.Combined with relevant test data,the characteristics of current,voltage and internal resistance of ternary lithium-ion battery are studied,and the influence of the above factors in SOC estimation process is analyzed.Then,the characteristics of existing electrochemical,equivalent circuit and neural network models are analyzed,and the 2RC equivalent circuit model of lithium ion battery is established.In the HPPC cycle condition,the recursive least squares(RLS)method is used to identify the model parameters,and the accuracy of the identification parameters under static and dynamic test conditions is verified by the Simulink model of the battery.The advantages and disadvantages of the common estimation algorithm for lithium-ion battery SOC are analyzed and discussed.The principle and specific recursive steps of extended Kalman(EKF),unscented Kalman(UKF)and improved center differential Kalman(SRCDKF)are studied.Finally,according to the specific requirements of the real-time estimation experiment of lithium-ion battery SOC,a lithium-ion battery estimation experimental platform is built and a current acquisition module is designed.Under the pulse discharge condition and UDDS condition,real-time estimation of lithium-ion battery SOC and online calibration and calibration parameters can be realized through dSPACE's RTI software and ControlDesk experimental environment.The results show that the SRCCDF real-time estimation of SOC proposed in this paper has higher precision,faster convergence speed and better stability than EKF and UKF.