Uncoordinated charging of a large number of electric vehicles (EVs) may cause voltage limit violations at distribution network nodes, load imbalance, increased total load demand, and widened peak-to-valley load differences. However, properly scheduling the controllable EV charging load can not only effectively mitigate the adverse effects caused by uncoordinated charging but also improve the stable operation capability of the power system. This paper establishes an objective response potential model and a subjective response potential model for EVs, then combines them to develop an integrated response potential model based on fuzzy inference. The active response deviation rate is calculated to analyze the adjustable margin of EV charging/discharging power. Simulation results ultimately verify the effectiveness of the proposed model.