Abstract
M.Ing.
The purpose of this study is to introduce a new three-phase AC-DC-DC converter topology with low electromagnetic interference (EMI) and unity power factor. This converter topology is obtained by merging the three-phase boost-rectifier and the full-bridge resonant-transition converter into a single, unique converter topology. This converter's boost-stage is completely soft-switched, in contrast with conventional topologies. Thus, each switch in the converter is soft-switched, and therefore the converter
--is named the three-phase All Soft-Switching Unity Power Factor Converter (ASSUP). Due to the zerovoltage switching of each switch, this converter has lower switching losses as well as EMI-levels than the conventional design. In the conventional design, the boost-stage, used for power factor correction, and the actual power converter, i.e. the full-bridge DC-DC converter, are realized in two seperate stages with two separate controllers. In contrast, the converter proposed here consists of one stage only, with one controller. The first topic discussed is a theoretical background on both low-frequency power quality (power factor and THD), and high-frequency power quality (EMI). This background is necessary for comparing the proposed converter with the conventional converter.
Secondly, an in-depth analysis of both the three-phase boost-rectifier and the full-bridge resonanttransition converter is done. This analysis is crucial in the analysis of the three-phase ASSUP, which is discussed thirdly. For each of the converters, a typical switching waveform is divided into unique intervals, for which the appropriate expressions are derived. The design of the practical component values is also discussed, as well as the control method for each of the converters. The three-phase ASSUP, introduced here, is lastly experimentally compared with the cascade-connection of the three-phase boost-rectifier and the full-bridge resonant-transition converter.