State-of-Charge Estimation for Lithium-Ion Batteries Based on a Nonlinear Fractional Model

This paper presents a new battery state-of-charge (SOC) estimation method for lithium-ion batteries (LIBs) based on a nonlinear fractional model with incommensurate differentiation orders. A continuous frequency distributed model is used to describe the incommensurate fractional system. A Luenberger-type observer is designed for battery SOCestimation. The observer gain that can stabilize the zero equilibrium of the estimation error system is derived by Lyapunov's direct method. The proposed SOC observer is examined using the real-time experimental data of LIBs. The robustness of the observer under different test conditions, including different aging levels, different driving cycles, and different cells, is also presented.