Two-Level Energy Control Strategy Based on ADP and A-ECMS for Series Hybrid Electric Vehicles

The number of vehicles is rapidly increasing. An effective control strategy for Hybrid Electric Vehicles (HEVs) is important. In this paper, we present a two-level control strategy that combines the Adaptive-Equivalent Consumption Minimization Strategy (A-ECMS) and the Adaptive Dynamic Programming (ADP). At the lower level, the A-ECMS is used to convert the consumed charge into Equivalent Fuel Consumption (EFC) for every sample moment, and a PI controller is used to adjust the values of the equivalent factor of the A-ECMS. At the upper level, the ADP is used to find the minimum of EFC corresponding to equivalent factor for every sample moment, and it maintains the State of Charge (SOC) of battery to charge and discharge smoothly in a high-efficiency field for the HEV. As by the ADP, we look into the future and then we can have a better estimate for the equivalent factor than the ordinary A-ECMS. In this way, we can save energy as well as calculate instantaneous parameters for the control strategy. Compared with a typical rule-based control strategy, the proposed control method saves EFC up to 10.3% and the stability of the SOC is increased by more than 60%, tested on benchmarks.