Research on energy management of dual energy storage system based on the simulation of urban driving schedules

Due to increasing concerns on environmental pollution and depleting fossil fuels, electric vehicles have recently been gaining increasing worldwide interest as a promising potential long-term solution to sustainable personal mobility. However, an energy storage system composed of battery and ultra capacitor can display a preferable performance for vehicle propulsion. As the ultra capacitor can fulfill the transient power demand fluctuations, the battery can be downsized to fit the average power demand without facing peak loads. Besides, braking energy can be recovered by the ultra capacitor. This study focuses on a vehicular system powered by two energy storage devices: battery and ultra capacitor. However, energy management strategy is necessary to split the power demand of a vehicle in a suitable way in order to maximize the performance while promoting the fuel economy and endurance of dual energy storage system components. In this paper, a dual energy storage system composed of ultra capacitor and the battery is introduced, the desire discharge current of the vehicular system under urban driving schedules is analyzed, and the working conditions of vehicular system are divided into four modes according to the state of energy storage system, a new hysteresis current control strategy is proposed for the developed vehicular system. The mathematical and electrical models of the vehicular system are developed in detail and simulated using MATLAB and Simulink environments.

► The inverter DC side current accords to the power demand curve under urban driving schedules.
► The battery can stay in the best state of low-current discharge.
► The energy management system improves the energy utilization rate of battery electric vehicle.
► The dual energy storage system has obvious advantages of high power density and high energy density.