A Loss-Mitigating Scheme for DC/Pulsating-DC Converter of a High-Frequency-Link System

This paper outlines a soft-switching scheme based on zero-current-switching (ZCS) principle with extended range for the front-end isolated dc/pulsating-dc converter of an isolated three-phase rectifier-type high-frequency-link power converter. General modulation methodology and optimization conditions are presented, and with the help of linear programming, the optimum solution for a particular objective function can be achieved to implement the proposed ZCS scheme. In conjunction with a back-end ac/ac converter operating with a novel patent-filed hybrid modulation scheme [1], [2], which reduces the number of hard-switched commutation per switching cycle, the proposed ZCS scheme can also realize zero-voltage-switching on secondary-side rectifier to improve the overall efficiency further. With the nonzero pulsating-dc output, the proposed ZCS scheme is effective even without an active-clamp circuit, and it is suitable for applications where low-voltage dc to high-voltage three-phase ac power conversion is required.