| This paper presents a comparison of power electronics topology designs for implementation in a Series Hybrid Electric Bus project. This specific hybrid vehicle design uses an internal combustion diesel engine (ICE), an ac electric generator, a passive/active rectifier/inverter, power storage, a traction motor inverter, and a traction motor/brake. The value of the hybrid vehicle comes from its increased efficiencies. The hybrid system decouples the ICE's power and speed from that of the bus. This decoupling is accomplished by replacing the traditional mechanical or hydro mechanical transmission with power electronics and energy storage facilities. This decoupling allows ICE operation at its most efficient power versus speed point. During normal operation, the energy storage system can be used to handle the dynamic loads and the internal combustion engine can handle the steady loading. This hybrid system also recaptures braking energy which is lost with conventional bus systems. The power electronics facilitate the process via control of power flow, battery management, motor control and generator control. There are two presently existing inverter/converter configurations that can be designed to implement these power electronics solutions. There is also a new solution using the novel Z-Source inverter as a current source inverter. Each of these designs have specific operation modes, control methods and features that are analyzed and discussed in this paper. The advantages and disadvantages of each are discussed. The concepts are then demonstrated via simulation and experimental results. |
