Analysis and Design of PDM Converter with High Frequency Link for HEV Drive System

A discrete pulse density modulation (PDM) converter with high frequency (HF) link is introduced to improve the performance of hybrid electric vehicle (HEV) drive system requiring high power density. The drive system is made of HF resonant inverter, HF transformer and PDM converter. The inverter changes battery DC voltage into AC signal with 20kHz, which is distributed as power sources for different equipments in HEV by the transformer. By mean of zero-voltage switching technique, the PDM converter transfers the HFAC signal into the single phase AC power with low frequency to drive induction motor. Based on the vehicle dynamic characteristics, the mathematic analysis of the PDM converter is presented, the operation principle and control strategy are described. The theory analysis shows that the proposed system has the advantages of higher energy density, flexibility in the choice of voltage levels in the HEV, and freedom from acoustic noise. The simulation results prove that the system has the merit of easy control, faster system response, and the lower switch losses