A voltage stress reduction technique for three-phase single-switch buck-type ac-dc converters

A three-phase single-switch ac-dc buck converter can operate with an excellent input power factor if the voltage across the three input ac-side capacitors is made to be discontinuous with zero voltage states. The main drawback to operating the converter in this Discontinuous Voltage Mode (DVM) that the peak voltage stress of the switch can be extremely high. A new variable switching frequency technique that will allow the converter to operate with reduced peak stress will therefore be introduced in the paper. In the paper, the new technique will be explained and its implementation in a standard buck and a quadratic buck converter will be analyzed. Comparisons between the new technique and conventional DVM will be made for both types of converters, and the analysis will be confirmed with results obtained from computer simulation.