Research On Joint Estimation Method Of Lithium-Ion Battery SOC And Capacity

Accurate estimation of battery SOC and SOH can effectively improve vehicle power and safety.In order to achieve accurate estimation of SOC and SOH,improving its estimation algorithm is a current research hotspot.This article focuses on the improvement of the EKF algorithm from the perspective of the battery model error,which realizes the real-time online estimation of battery capacity error and compensates the SOC estimation value at the same time,thereby improves the estimation accuracy of SOC,and corrects the available capacity information in time to know the battery aging status.The research of this paper starts with the working principle of the battery,studies the mechanism of the capacity attenuation phenomenon and the influence on the battery performance parameters,and understands the reasons and characteristics of the capacity error,which can provide a basis for the subsequent establishment of a model error observer to estimate the capacity error.The research studies the lithium-ion battery modeling problem.In the battery modeling stage,the ECM used for battery SOC estimation is summarized.After weighing the complexity and model accuracy,the firstorder RC model is selected for research.Subsequently,offline step-by-step parameter identification based on LSM and online parameter identification based on the idea of least squares with forgetting factor are proposed for parameter identification work,and the second method with a wider applicability is selected for parameter identification work.Finally,the research processes the DST working condition data for parameter identification and verifies the accuracy of parameter identification.Subsequently,the KF and EKF theories are introduced,and the influence of the battery capacity error on the accuracy of the SOC estimation is demonstrated through formula derivation and simulation verification,and also the research explained the importance of studying the capacity error.Then the research introduces the decoupling estimation algorithm based on the state quantity of KF and EKF and the model error quantity,and applies the decoupled parallel filtering algorithm to the battery SOC estimation problem for the battery capacity error,and obtains the standard EKF algorithm for SOC estimation with the model error observer used to estimate the capacity error.A simulation verification model is built on the Matlab/Simulink platform.Detailed verification and analysis are carried out.The verification results show that compared with the standard EKF algorithm,the improved algorithm can not only improve the estimation accuracy of the SOC,but also can track the capacity error and know the aging status of the battery in time.The algorithm proposed in this paper shows better prediction accuracy and robustness.