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% while 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.