Research on improving energy regeneration efficiency of super-capacitors electric bus

Based on the research about the bidirectional buck-boost driver, reasonable projects were proposed to solve the problem that it was hard to recover the braking energy when low speed for super-capacitor electric bus. First, a passive lossless snubber project was designed to reduce the switch loss and protected the switch; the energy during switching transient process was transferred to charge the super-capacitor bank, which was helpful to improve the braking energy regeneration efficiency. The simulation and experimental results gave out the effect of snubber and improving efficiency. After analyzing the working principle of the equivalent braking circuit, this paper explained why braking current could not meet its given reference value when low speed. Then, the PWM+PFM control project was found out to increase the braking current. Simulation results demonstrated that the PWM+PFM project could make a great improvement on the efficiency of recovering braking energy compared with original PWM project.