A soft switched direct frequency changer

Development in power semiconductors and commutation techniques has brought back the interest in direct frequency changers. A soft switched three-phase to single-phase direct frequency changer is introduced adopting the bidirectional ZVS cell proposed by the authors (see IEEE APEC, 1995). Hence, the proposed converter does not need dead time between gate signals, presents natural protection against overcurrent, uses a simple gate signal drive circuitry and the commutation losses are reduced with no increase of the conduction losses. All types of AC modulation can be used and the bidirectional switches can operate in high frequency of commutation. A prototype operating at a high commutation frequency using IGBT is assembled and the results obtained are discussed. Analysis and design are also presented.