Energy management strategy of dual planetary hybrid electric vehicle based on optimal transmission efficiency

A power split hybrid electric vehicle with dual planetary gear sets is studied in this paper. Firstly, the power split and circulation phenomenon are further described by analyzing a speed and torque relationship between the engine, motors and the output shaft based on the lever analogy. The transmission efficiency and the electric power ratio are then obtained. The working modes of the hybrid electric vehicle (HEV) are divided according to the system operation mechanism. On this basis, the engine optimal operating line (OOL) control strategy and the mechanical point (MP) control strategy are designed. Furthermore, a fuzzy controller is designed to realize the optimal torque distribution of the engine and the motors in the MP control strategy. Simulation results demonstrate that the MP control strategy can guarantee a higher efficiency of the transmission system, which also shows good performance in improving fuel economy of the HEV by adjusting the engine operating point.