Reserch On Modeling And SOC Estimation Of Lithium Battery Based On Fractional Calculus Theory

With the aggravation of the global energy crisis and the worsening of environmental pollution,all the countries in the world have been developing new-energy electric vehicles with green environmental protection.As one of the key components of electric vehicles,the performance of power battery has a great impact on the performance,safety performance and mileage of electric vehicles.Due to its large energy density,long cycle life,safe and reliable,and pollution-free,lithium-ion batteries will surely be greatly developed in future research and development.The State of Charge(SOC)of Lithium battery is the core of the battery management system,reflecting the power battery operating conditions of the main performance parameters.Accurately estimating the SOC of the battery can effectively control the battery and the entire vehicle,preventing overcharging and over discharging of the battery,providing a basis for battery balancing and energy distribution,and can prolong the service life of the battery and save the cost.In this paper,the battery model and SOC estimation method that affect the estimation accuracy of battery SOC are studied in detail.This dissertation firstly summarizes the development of pure electric vehicles,and evokes the importance of power batteries.Then it introduces the working principle of lithium batteries,and studies the characteristics of lithium batteries and the factors that influence the characteristics.Through the analysis of classical battery models,this paper proposes the innovative variable-temperature fractional-order PNGV model uses the statistical method of Design of Experiment(DOE)and Particle swarm Optimization(PSO)to fit the parameters in the battery model.Through the FUDS operating conditions,the accuracy of the variable-temperature fractional-order PNGV model is verified.The obtained model not only adapts to the continuously changing temperature,but also is more accurate than the integer-order model.It provides an accurate model for the following SOC estimation.The SOC estimation of the power battery,which is one of the core technologies for the development of electric vehicles,is the key to the industrialization and practical application of electric vehicles.In this dissertation,based on the model established in the previous section,a fractional stepless particle filter algorithm is proposed.The accuracy of the FUPF algorithm is verified using the cyclic discharge condition and the US06 operating condition comparison with other algorithms.The convergence of FUPF algorithm are verified under different initial errors using the US06 operating conditions.