A High-Power MVAC-LVDC Rectifier Empowering Wide Voltage Range Operation

The increasing demand for dc power loads across various applications such as railway systems, data centers, electric vehicle charging stations, and hydrogen electrolyzers necessitates efficient rectifiers capable of converting medium-voltage ac (MVac) to low-voltage dc (LVdc) while accommodating a wide dc voltage range. This article presents a novel high-power MVac-LVdc rectifier that integrates submodule (SM) arms, thyristors, a monolithic medium-frequency transformer (MMFT), and a diode bridge. The SM arms enable precise control over thyristors commutation, MVac current, and dc current, while maintaining high waveform quality on both MVac and LVdc sides. By adjusting the arm voltage, the rectifier can achieve a wide dc voltage range from zero to its rated value. Compared to the conventional solid-state transformer, the use of MMFT and low-loss thyristors reduces the number of high-insulation transformers and IGBTs, enhancing both cost-effectiveness and efficiency with a 30% reduction in loss and a 24% decrease in cost the performance of the rectifier is validated through simulation at 6 MW and experimental testing with a 3 kW scale-down prototype.