Online Parameters Idantification Of Fractional Order Model And SOH Estimation For Lithium-ion Battery

The structure of the fractional order model for battery and the method of obtaining model parameters determine the accuracy of the terminal voltage estimation based on the model.Compared with the offline parameter identification,the online parameter identification of fractional order model has higher identification accuracy.In this paper,the measures to improve the simulation accuracy of fractional order model are analyzed from the aspects of both frequency domain and time domain.Based on the fractional order model with high impedance simulation accuracy and the online parameter identification algorithm,the high-precision model parameters are obtained.The open circuit voltage identification,voltage simulation and health state estimation are realized.the online application of fractional model is realized.The simulation accuracy of the fractional order models of different impedance components is analyzed by establishing the impedance simulation model in the frequency domain,whose feasibility of the application in time domain is investigated.The parameters of two fractional order models were identified online by Forgetting Factor Recursive Least Square method in time domain.The parameters identification accuracy and terminal voltage estimation accuracy of the fractional order model were analyzed.Using the parameters which can be obtained by online identification algorithm to replace the calculation of historical data,which simplifies the fractional order model.The simplified fractional order model combined with online parameters identification algorithm was used to estimate the battery health status.The results show that using the Forgetting Factor Recursive Least Square method to obtain the parameters of the fractional order model online can ensure the high terminal voltage estimation accuracy and open circuit voltage identification accuracy under dynamic conditions.Improving the simulation accuracy of fractional order model is helpful to improve the accuracy of terminal voltage estimation and open circuit voltage identification based on online identification algorithm.The dynamic stress test is tested for online parameters identification of the simplified fractional order model.The error of terminal voltage estimation is within 5m V.The state of health estimation accuracy based on the coupling parameters of the simplified fractional model is higher than that based on the ohmic internal resistance of the simplified fractional model alone.The online application of fractional order model is realized by online identification of parameters and simplification.