Descriptor system observer-based state-of-charge estimation for batteries

A new method for battery state-of-charge (SOC) estimation was proposed. To avoid the difficulties in treating the piecewise linear relationship between the open-circuit voltage (OCV) of the battery and the SOC, the popular approach for the observer design is to take the time derivative of the equation of the output voltage. It shows that the design of the observer by taking the time derivative of the voltage equation is incorrect. It is pointed out that the piecewise linear relationship can be considered as a linear constraint of a descriptor system. So the descriptor system approach was proposed to cope with this piecewise linear constraint. And the descriptor system observer was then designed. Simulation shows the effectiveness of the proposed method.