Research On Modeling Strategy Of Ternary Lithium-ion Batteries For Electric Vehicle

In recent years,with the energy crisis,environmental pollution and other issues becoming increasingly serious,hybrid and pure electric new energy vehicles began to step on the stage of history and become the key industries of various countries.Power lithium battery is one of the core components of electric vehicles,and it is the main energy storage component.Power battery technology has also become a key factor restricting the development of new energy vehicles.Accurate and reliable battery management system can guarantee and improve the function of battery system,ensure the stable,reliable and accurate operation of battery system,improve the advantages of electric vehicles,and meet the needs of consumers.It is very important to establish an accurate battery model for the accurate estimation of state of charge.In this paper,the modeling scheme and SOC estimation strategy of ternary lithium-ion battery are studied.This paper analyzes the structure and working principle of lithium battery and the charge discharge reaction process of ternary lithium battery.In this paper,the equivalent circuit model of 18650 ternary lithium battery is summarized and analyzed.The capacity,open circuit voltage characteristics and the influencing factors of 18650 ternary lithium battery are tested and analyzed.A new parameter identification condition is designed based on the current common vehicle identification condition,which provides scheme support for the subsequent battery modeling and parameter identification.The basic functions,definitions and properties of fractional order theory are summarized.According to the working characteristics of lithium battery,an improved Thevenin model is proposed based on the traditional Thevenin equivalent circuit model,a new fractional order model is proposed based on the electrochemical impedance spectrum and the spectrum obtained from the fast Fourier transform of common vehicle working conditions,and a fractional order model based on the second-order RC model is proposed combining the second-order RC model with the electrochemical reaction and electrochemical impedance spectrum.Three parameter identification strategies are proposed: differential evolution algorithm based on piecewise evolution,adaptive particle swarm based on PSO Optimization,and adaptive hybrid multi swarm particle swarm optimization,which combines adaptive particle swarm optimization and differential evolution.Based on the lithium-ion battery experiment and the data of different working conditions,the accuracy difference of different models,the accuracy difference of different algorithms and the influence of two influencing factors on the accuracy of the model are analyzed and verified from four angles.The experimental results show that the fractional modeling scheme has high accuracy and adaptability,and can better reflect the battery characteristics;self-adaptive hybrid multi groups Hybrid particle swarm optimization algorithm can find the global optimal solution more quickly and accurately,and it is the best parameter identification strategy.Based on the second-order RC model and the fractional order system respectively,the sufficient conditions for the stability of the two systems are proved by mathematical analysis.According to the experimental data,it is proved that the integer order model and the fractional order model are feasible and robust in practical application.Because the fractional order model can be better anti Due to the battery characteristics,its anti-interference ability is higher.