Design of a High-Power Resonant Converter for DC Wind Turbines

This paper presents a design procedure and loss estimation for a high-power, medium-voltage series resonant converter (entitled SRC#), intended for application in megawatt medium-voltage dc wind turbines. The converter is operated with a novel method of operation, entitled pulse removal technique, characterized by variable frequency and phase-shift modulation, below the resonant point of the LC tank. A step-by-step design procedure is proposed and circuit component ratings and efficiency are compared for two variants. The new method of operation reduces transformer size to below 50%, whereas losses are kept below 1.5% from zero to nominal power, due to soft-switching characteristics. An experimental setup, rated for 10 kW and 5 kV output was assembled to extract losses and validate the semiconductor loss model.