An auxiliary resonant soft switching matrix converter

Abstract

This paper is concerned with the design, construction and testing of a 3-phase to 3-phase soft switching matrix converter. Two auxiliary soft switching circuits are added to each output phase in order to achieve soft switching without significantly increasing the conduction losses. The converter operation is discussed with reference to theoretical waveforms. The distribution of the switching losses with respect to load current and commutation voltage is investigated. Using the proposed topology it is possible to disable the auxiliary switch when the current and/or voltage is low. This simplifies the design of the auxiliary circuit as the range of operating conditions is reduced, allowing better optimisation in terms of switching losses and commutation speed. We present results from a 3-phase to 3-phase prototype matrix converter showing switching waveforms for all commutation scenarios. Measurements of the overall power circuit losses are presented and comparisons are made with conventional hard switching matrix converters. The distribution of losses between the different loss mechanisms will be investigated for both converters. It is shown that the switching losses for the main switches is reduced by about 50% but this is compensated for by the losses in the auxiliary switches resulting in no significant increase in efficiency. Further research will be required to develop viable soft switching matrix converter structures.