An LLC-resonant Power Decoupling Strategy for a Quad-active-bridge Power Channel based AC/DC Power Electronics Transformer

This paper proposed a modular power electronic transformer (PET) with LLC type quad-active-bridge (LLC-QAB), in order to serve as an efficient interface between three-phase high/medium voltage (HV/MV) AC grids and low voltage DC bus. The LLC-QAB is featured with a four-winding high-frequency transformer (FHFT) that is intended to be a power channel for AC ripple powers cancelation. The power density is thus promoted. The pulse frequency modulation (PFM) combined with ripple power decoupling control strategy is then proposed to realize power decoupling and soft-switching of power devices. The power conversion efficiency is also improved. Simulation and experimental results verified the effectiveness of the proposed techniques.