Study of high efficiency DC drive system of ultra-capacitor electric city bus

The ultra-capacitor electric bus (UCEB) direct currentdrive system uses the permanent magnetic direct current (PMDC) motor with the electrical enhanced magnetism windings as its traction motor, which could regulate the output torque linearly. The main circuit is the current two-quadrant topology. A snubber soft switch based on the characteristic that the ultra-capacitor could be charged fast is designed to heighten the converter's efficiency and reliability, which could be validated by simulations and experiments. Even when the UC voltage varies large-scalely, the converter could insure that the drive system works in its reasonable modes. Nonstandard dual closed loop control reduces the converter's current overshoot and insures that it is comfortable to drive the bus. The high efficiency DC drive system increases the one time traveling mileage when it is used in the limited energy UCEB system.