A Three-phase High Power Factor Two-switch Buck- Type Converter

The paper proposes a three phase, two switch buck type converter with high power factor.The key feature of the proposed converter is that a switch in the converter has a lower peak voltage stress than a switch in a conventional threephase, single-switch buck-converter. A switch in the converter sees a line to neutral voltage across it rather than a line to line voltage which is the case for the switch in the conventional converter. The voltage stress in the proposed converter is limited to the peak value of the phase voltage of the input capacitors rather than the peak value of the line-to-line voltage, as is the case in the conventional converter. Since a switch in the proposed converter sees a line to neutral voltage instead of a line to line voltage the peak voltage stress is almost half than that of the switch in the conventional converter as this stress is reduced by a factor of sqrt(3). This reduces switching losses and allows lower rated standard devices to be used in converters. In the paper, the operation of the proposed converter is given and general considerations that should be taken into account when trying to design it are discussed. The feasibility of the converter is confirmed with results obtained from computer simulation and from an experimental prototype.