Research On Electric Vehicle SOC Estimation And Energy Cooperative Control Technology

Since the 21st century,with the rapid development of the world economy and technology,the number of traditional fuel vehicles has been increasing day by day,which has brought serious energy crisis and environmental pollution to the world.Therefore,the state strongly advocates the development of new energy vehicle technologies.In this context,in order to provide an accurate basis for battery energy management strategy and ensure driving safety,this paper seeks accurate SOC estimation methods for lithium-ion battery.In addition,this paper combines lithium-ion battery and ultracapacitor into a hybrid energy storage system,and formulates a energy collaborative control strategy for the hybrid energy storage system to extend the life of electric vehicle power battery and improve energy utilization rate of electric vehicle.Firstly,this paper builds an experimental test platform.The working principle of the lithium-ion battery is analyzed.The charge-discharge experiments of lithium-ion battery were used to analyze nonlinear characteristics,and the pulse discharge experiments were used to analyze polarization response characteristics.The energy storage mechanism of the ultracapacitor is analyzed,and its linear characteristics are analyzed through charge and discharge experiments.Based on the linear characteristics of ultracapacitor,a state feature definition method is established.Secondly,this paper establishes a second-order RC equivalent circuit model for lithiumion battery.The FFRLS algorithm is used to improve the traditional recursive least squares method,and the model is decomposed for online parameter identification.The commonly used offline model parameter identification algorithm is optimized,and the FMEKF algorithm is used to identify the ohmic resistance in the battery model to improve the accuracy of SOC estimation.Thirdly,the discrete state space equation of the equivalent circuit model of the lithium-ion battery is established.The traditional EKF algorithm is improved by the SFEKF algorithm.The SOC estimation algorithm based on SFEKF is combined with the online model parameter identification algorithm based on FFRLS and the improved offline model parameter identification algorithm based on FMEKF.At the same time,the results of several SOC estimation schemes are compared to verify the accuracy and feasibility of the SOC estimation method designed in this paper.Finally,the semi-active structure is designed as the system topology of the hybrid energy storage system,and the vehicle parameter matching scheme of the hybrid energy storage system is formulated.The working mode of hybrid energy storage system is analyzed.The energy cooperative controller based on fuzzy logic control is established and optimized by genetic algorithm.In the MATLAB / Simulink environment,the ADVISOR software is used to build simulations for the secondary development of the hybrid energy storage system,and the optimization results of the energy collaborative control are obtained.