A comparative study of observer design techniques for state of charge estimation in electric vehicles

A well-known Luenburger observer and two sliding mode observers (SMO) for battery state of charge (SOC) estimation based on an improved battery equivalent circuit are presented. The comparison of their SOC estimation results is discussed. The testing data under different discharge current profiles generated by DUALFOIL battery simulation program are used to extract the circuit model parameters and verify the effectiveness of the observers for the SOC estimation. It shows that two sliding mode based SOC observers have robust tracking performance and provide more accurate SOC estimation in electric vehicle driving conditions.