Energy Reports (Nov 2022)
Energy management and nonlinear control strategy of hybrid energy storage system for electric vehicle
Abstract
The energy management of hybrid energy storage system (HESS) and the nonlinear control strategy of the interface circuit are studied in this paper. In order to realize the reasonable distribution of load power between the battery and the supercapacitor, the energy management strategies (EMS) are used to decompose the load power required for electric vehicles under different driving cycle conditions, aiming at choosing an optimal power allocation strategy. Based on the local modeling, the global mathematical model of two bidirectional DC/DC converters under the HESS with active control topology is established, and the nonlinear control strategies are studied for the interface circuit and then the target controller is designed to realize the EMS. The current inner loop controller based on synergetic control theory is to track the battery current and supercapacitor current. The voltage outer loop controller takes power conservation as the criterion and adds the DC bus voltage PI controller to construct the Lyapunov function, where the connection between the DC bus voltage stability and the supercapacitor reference current is established. The supercapacitor replaces the battery to overcome the fluctuation of the DC bus voltage caused by the sudden change of the load power, maintaining the stability of the entire control system, and at the same time the case that the power allocated by the supercapacitor is consistent with the EMS is ensured. Two typical vehicle driving cycle conditions, IM240 and ECE-15, are selected to test the effectiveness of the current controller and the voltage controller. The experimental platform of a small-capacity HESS is built to conduct experimental verification. The simulation and experimental results show that the nonlinear controllers are feasible and have strong robustness and good adaptability under different driving conditions.
