Proactive Power Management Scheme for Hybrid Electric Storage System in EVs: An MPC Method

Abstract

Hybrid electric storage system (HESS) is a promising power supply for electric vehicles (EVs) to prolong battery cycling life. Battery longevity is affected by the magnitude and fluctuation of the charging/discharging power profiles. While vehicle driving, unexpected high power demand can cause battery degradation and should be supplied by the supercapacitor (SC) in the HESS. However, the limited capacity of SCs restricts the HESS benefit. Thus, one of the crucial while challenging issues for an HESS is how to effectively manage the power splitting between batteries and SCs to satisfy the vehicle’s driving demand as well as reducing battery degradation rate. In this paper, a proactive power management scheme is proposed to extend the EVs battery life with the HESS. First, we exploit a time-series forecasting method to predict the short-term vehicle velocity and calculate the future power demand based on prediction results. Next, due to the nonlinear dynamics of the HESS, the T-S fuzzy modeling method is adopted to approximate system nonlinearity and develop an empirical model. Finally, a model predictive control (MPC) based power management problem is formulated. Prediction errors are considered in MPC formulation to improve system robustness. Based on driving profile tests, simulation results demonstrate that the magnitude and fluctuation of battery current are both reduced and the battery life is prolonged by 17.81% compared with the existing methods.