Snubbers in the Three-phase AC to DC Buck Converter

In this paper, investigation of effective snubber circuits in the three-phase AC to DC buck converter is presented. Based on the theoretical analysis and from the conventional matrix converters theory approach, the mathematical proof for an AC to DC power converter with unity input displacement factor (IDF) operation without current sensing, is provided. For the DC output current bulky inductance in the output filter is needed and appropriate modulation strategy without open circuit terminals must be assured. High inductance and very short switching times of the power switches are main source of the high and destroying dv/dt in the power converter. This problem can be overcome by proper driving circuits and by appropriate design of the effective snubber circuits not only at the switching power transistors but also at the series diodes as well. And finally, all theoretical considerations are verified by digital simulations and measurements on a low-power prototype of a three-phase buck rectifier.