Energy management strategy of a novel mechanical–electro–hydraulic power coupling electric vehicle under smooth switching conditions

Abstract

To increase the transient power limit, and reduce the impact of operating condition changes on the electric vehicles’ powerful battery, it is essential to stabilize the working condition, enhance the vehicle’s dynamic performance and energy utilization. In this paper, a novel mechanical–electro–hydraulic power coupling system for electric vehicles is proposed. It integrates a planetary gear mechanism as a power coupling component with an accumulator, a hydraulic pump/motor, which efficiently converts electrical, mechanical, and hydraulic energy. A rule-based dynamic energy management strategy is established to control the energy distribution and the dynamic switching of working conditions in real time. By analyzing the system’s operating mode, a new vehicle model is established. First, the feasibility and superiority of the new model are verified compared with the pure electric vehicle model. Simultaneously, the vehicle speed jitter problem during electro–hydraulic power switching is eliminated by altering the inclination angle of the secondary element. Ultimately, the verification results illustrate that the battery power consumption is reduced by 14.7%, and the energy recovery rate of the accumulator is as high as 94.3%. Furthermore, reasonable distribution of the torque in two motors through fuzzy control strategy significantly stabilizes the main motor’s working state and improves its overall efficiency.

Keywords

• Mechanical–electro–hydraulic power coupling system
• Electric vehicle
• Energy management strategy
• Smooth power switching
• Fuzzy control strategy