Online Estimation for Equivalent Circuit Parameters of Lithium-Ion Batteries Based on Impedance Measurement

Parameters of the lithium-ion battery equivalent-circuit model (ECM) change with state of charge and temperature. Accurate online parameters identification of lithium-ion battery ECM can achieve high-precision online state estimation. In this paper, a new online parameters estimation method based on impedance measurement is proposed. The 1-RC Thevenin ECM is employed and the impedance is measured on line based on the second-order generalized integrating unit (SOGI) and equivalent reactive current injection technology. Then the parameters of the ECM are estimated based on the impedance by the recursive least squares (RLS) method. This parameter estimation method is verified by experiment results with the federal urban driving cycle (FUDS) operating conditions and the proposed method has high accuracy which can be used to realize state of charge and state of health estimation.