A new three-phase soft-switched bridgeless AC/DC step-up converter with current fed voltage doubler modules for DC grid in wind systems

A new soft-switched, bridgeless rectifier is presented in this paper that is integrated with an isolated step-up resonant converter for step-up voltage conversion in medium voltage (MV) DC grid in wind energy applications. To reduce the number of conversion stages, the proposed bridgeless boost rectifier is integrated with a high-frequency step-up resonant converter with voltage doubler modules to form a single-stage AC/DC step-up converter. The proposed converter is able to reduce the number of semiconductors required for the front-end rectifier, thus simplifying the resulting controller. In addition, all the switches and diodes are able to achieve soft-switching to enhance the overall circuit efficiency. Simulation results are given on a 800kW, 690Vac/15kVDC system to highlight the merits of the proposed converter. To further validate the performance of the proposed converter, experimental results are provided on a laboratory scale 50Vac/1kVDC, 28kHz Silicon-Carbide based proof of concept prototype.