A High-Gain DC Side Converter with a Ripple-Free Input Current for Offshore Wind Energy Systems

Abstract

Considering that the distance between offshore wind farms and onshore converters is getting farther and farther, dc transmission becomes increasingly more applicable than conventional ac transmission. To reduce the transmission loss, a feasible solution is using a high-gain dc/dc converter to boost the rectified output voltage to thousands of volts. Thus, a novel single-switch high-gain dc/dc converter with a ripple-free input current is presented in this paper. The structure consists of two cells—a coupled-inductor cell and a switched-capacitor cell. The coupled-inductor cell in the proposed converter provides a ripple-free input current. The switched-capacitor cell provides a high voltage gain. The converter has a simple control strategy due to the use of a single switch. Moreover, the output capacitor is charged and discharged continuously by a 180° phase shift to eliminate the output voltage ripple. A steady-state analysis of the converter is proposed to determine the parameters of the devices. In addition, a 240 W, 40/308 V laboratory prototype at 35 kHz switching frequency has been developed, in which the input current ripple is only 1.1% and a peak efficiency of 94.5% is reached. The experimental results verify the validity and feasibility of the proposed topology.