Co-estimation Of SOC And SOH Of Li-ion Battery Based On Fractional Calculus Theory

At present,in the field of transportation,because electrical vehicles(ECS)have many advantages,such as energy-saving and environmentally friendly,which make it bccome a hot development target.However,The related technical of battery management system(BMS)is seriously imperfect,and it severely restrict the progress of Lithium-ion battery industry and ECS.The BMS can guarantee the safety and effectiveness of the battery,and improve the battery energy utilization rate because its own controllability and monitor of battery.In the battery management system,the important and difficult technical challenge are SOC and SOH.Based the University of Maryland battery data,this article estimates the battery SOC and SOH.The main research contents are as follows:For the modeling problem of the non-linear system of lithium-ion battery,in order to lay the foundation for subsequent modeling and state estimation,this paper analyzes the battery characteristics and summaries the factors that affect the battery characteristics.According to the battery’s fractional-order characteristics,by analyzing the electrochemical impedance spectrum of the battery,the fractional-order battery model is composed of fractional-order electrical devices,and it can estimate the battery state.Final,different battery dynamic condition experiment is use to test the precision and Effectiveness of the model.Aiming at the problem of accurate acquisition of model parameters.In order to resolve the parameter identification problem,the problem will be changed into an optimization problem,which can get precious results.On this basis,HGPSO is adopted to identify model parameters,which have the merits of the PSO algorithm and the GA algorithm.And in order to test the function of the HGPSO,a simulation is used.Bade on the experimental results,the method can validly evaluate the battery model parameters.For the state of charge(SOC)estimation problem of the fractional model of lithium-ion battery,this paper introduces the theory of fractional calculus into the Unscented kalman filter(UKF)algorithm,and proposes the fractional-order unscented Kalman filter algorithm to estimate the battery SOC.At the same time,in order to reduce the amount of calculation,the "short-term memory" effect is added.Finally,the simulation comparison with the integer-order unscented Kalman filter algorithm under DST and FUDS conditions shows that the fractionalorder unscented Kalman filter algorithm has higher accuracy and robustness.For the health status estimation of the fractional-order system of lithium-ion batteries,considering the complex coupling relationship between battery SOC and SOH,and the different rate of SOC and SOH change,this article will apply the time scale theory into SOH estimation based on the fractional-order model.In the macro time domain,the FUKF algorithm is used to estimate the slowly changing parameter SOH,and the FEKF algorithm is used to estimate the fast-changing parameter SOC of the battery in the micro time domain,their estimation results are mutually corrected.Finally,the proposed battery health monitoring method is verified and analyzed through simulation experiments.The experimental results show that it has better estimation performance.