A robust observer based on the nonlinear descriptor systems application to estimate the state of charge of lithium-ion batteries

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A robust observer based on nonlinear descriptor systems is applied to estimate lithium-ion batteries’ state of charge (SOC). We creatively take the relationship between the battery’s open circuit voltage (OCV) and SOC as a nonlinear algebraic constraint, thereby modeling the battery as a nonlinear descriptor system. This model can effectively trade off accuracy and complexity. The robust convergence, even in the presence of uncertainties, is proven through a combination of the Lyapunov stability theorem and linear matrix inequality (LMI) techniques. Experimental results showcase the effectiveness of the proposed SOC estimation technique, offering enhanced convergence speed, estimation accuracy, and robustness compared to conventional sliding mode observers.