Effect of SOC Uncertainty on MPC based Energy Management Strategy for HEVs

An optimal energy management strategy is a key to improve the Hybrid Electric Vehicle's fuel economy. Existing optimal energy management strategies consider the State of Charge (SOC) estimate to be accurate while solving the optimization problem. However, due to measurement noise and model inaccuracy, SOC estimation becomes uncertain which leads to a non-optimal solution of the optimization problem in practice. This paper targets to analyze the effect of SOC uncertainty in a Model Predictive Control based energy management strategy, for which the sensitivity of cost function with respect to SOC uncertainty is studied. Thereafter, with realistic simulation results obtained using a vehicle simulator with a validated HEV model, it is shown that the inaccuracy of SOC estimation can adversely affect the energy management performance.