A new bidirectional ZVS switch for direct AC/AC converter applications

This paper introduces a new bidirectional soft commutation switching cell aimed at use in direct AC/AC converters. The proposed technique features no dead time between commutations of different switches and overcurrent protection thanks to the use of the principles of the dual thyristors. Because all the switches are driven at the same time, this cell allows design of a simple gate signal drive circuitry. As a consequence, all types of AC modulations can be used and the bidirectional switches can operate at high frequency of commutation. Another advantage of this technique is that only two power switches are conducting at the same time with no increase of the conduction losses. A prototype of an AC chopper operating at 20 kHz using IGBT was implemented in the laboratory. Analysis and design are also presented in the paper