Effects analysis of model parameters uncertainties on battery SOC estimation using H-infinity observer

The accurate estimation of the state-of-charge (SOC) of battery is the basic premise for the effective energy management and the important guarantee for the safe and efficient operation in electric vehicles. To improve SOC estimation accuracy and robustness, the paper analyzes the effects of different initial SOC errors and parameters variation on SOC estimation accuracy and robustness with H-infinity observer. A model in Matlab/Simulink is established to make calculation process come true, which is based on a new battery with nominal capacity of 90Ah. The simulation and experiment al results indicate that the H-infinity observer based SOC estimation can converge to the true values quickly even if at the set maximum initial error and its steady error can be controlled within 2%. The effects of model parameters change resulted from battery degradation including SOC-OCV relationship, capacity and internal resistance on H-infinity observer are investigated. It is concluded that SOC estimation accuracy with H-infinity observer largely depends on the accurate of the curve of SOC-OCV (Open circuit voltage, OCV), which provide a foundation for battery management.