Three-Phase Three-Level Reduced Switch Count Isolated AC/DC Neutral-Point Clamped Converter With High-Frequency DC-Link

This paper proposes a three-phase three-level reduced switch count isolated AC/DC Neutral-Point Clamped (NPC) converter, with high-frequency DC-link, for applications of unidirectional power flow. No bulky electrolytic capacitors are necessary in the DC-link, in contrast with conventional multi-level topologies. A Hybrid Sinusoidal Pulse Width Modulation (HSPWM) strategy is used to operate the proposed converter. The applied PWM technique is able to operate the AC-side converter stage with only one switch commuting in a switching period. The switches of the isolated pulsating DC/DC converter are commuted with half of the switching frequency of the AC side's converter. A dual-loop control strategy with voltage PI and current resonant PI controllers is adopted to guarantee the reference load voltage and almost sinusoidal grid currents. Simulation results are presented to validate the proposed converter operation.