A high-efficiency regenerative braking for electric vehicles

To improve energy efficiency of electric vehicles, a method, which uses variable voltage system as electric motor driving system to implement energy recovery is proposed. Combining the ultra-capacitor (UC) banks, which is series-parallelly switchable, with bi-directional DC/DC power converter (BDPC) and adopting the control strategy containing two regenerative braking modes, the transferring efficiency and conversion efficiency of energy flow between electric motor and supply of driving system are improved, thus the energy recovery within wide speed range is attained. Comparing with conventional breaking methods, the proposed method possesses the features of small size of driving system, low cost and high energy recovery efficiency. By means of simulation on Matlab/Simulink platform, the comparative analysis on three situations adopting different regenerative braking ways is performed, and the feasibility and effectiveness of the proposed method are verified by simulation results.