A Three-Phase Single-Stage ac/dc Converter Based on Swiss Rectifier and Three-Level LLC Topology

LLCresonant converter is widely used due to its soft switching, high power density, and high efficiency. To incorporate the merits of theLLCresonant tank into a three-phase single-stage ac/dc converter, this article proposes a three-phase single-stage ac/dc converter based on Swiss rectifier and three-levelLLCtopology. It takes advantage of the high-efficiency Swiss rectifier to convert three-phase ac voltages into three variable dc voltages and interface a three-levelLLCresonant circuit. With help of theLLCresonant tank, all the high-frequency three-level switches achieve soft switching. To both regulate the output voltage and achieve three-phase power factor correction, the frequency modulation in combination with the duty cycle control strategy is employed by splitting the resonant current into three parts and then forming three phase sinusoidal currents. The proposed converter's detailed operation principles, steady-state characteristics, and design considerations are given. Finally, a 10 kW experimental prototype with three-phase 220 Vac inputs and 500 Vdc output is built to verify the effectiveness and feasibility of the proposed topology and its control strategy.