Researching On Electric Bus Auxiliary Power Supply System

Electric vehicle has being the most approachable way to solve the problems of energy source shortage and environment pollution. Development of electric vehicle with low energy consumption and emission is being under-way by automobile industry and research institute, which is encouraged by government policy. Now there is no battery with all the excellences viz. high specific power, high specific energy, long cycle life, low price security and pollution-free.In the past few years, the ultracapacitors, however new, are an attractive option in electric vehicles due to their high specific power, long cycle life and high efficiency during discharge and re-charging. A hybrid electric power system composed of fuel cells and ultracapacitors is considered as the best concept for electric vehicle propulsion problem.The content of this paper is the preliminary searching for the electric vehicle power supply technique, first of all, analyzing characters of accumulators and ultracapacitors as well as the industrialization condition and researching the dominance during discharge and re-charging of hybrid power supply system compared with single accumulators. A hybrid power supply system is designed which structure is composed of ultracapacitors and fuel cells with the control strategy. The focus is the auxiliary power supply system using ultracapacitor as energy storage buffers. Then designed an auxiliary power supply control system, using the state space average method to model the designed bi-directional non-isolation DC-DC converter, analysis the performance of every state, simulated the hardware topology structure and the PID controllers based on the mathematical model are given. The simulation results prove the good control performance. Aimed at the electromagnetic interference problem of the designed bi-directional non-isolation DC-DC converter, a three-level bi-directional non-isolation DC-DC converter is presented, and the relationship between the output voltage and input voltage is given as well as the simulation of the hardware topology structure. The simulation results prove the new topology structure gains the ends of decrease the EMI and reduce the voltage stress and the output voltage harmonic wave. At last select each part of the hybrid power supply systemaccording to the optional bus model parameters and the quantitative calculation method is given, it's the theoretical prepare for the experiment of developing electric bus.