The Uni-polarity Phase-shifted Controlled Buck Mode AC/AC Converters with High Frequency Link

A circuit configuration and circuit topological family of Buck mode AC/AC converters with high frequency link, and uni-polarity phase-shifted control strategy are proposed and deeply investigated. This kind of converters is constituted of input cycloconveter, high frequency transformer, output cycloconverter, input and output filters, and can transfer an unsteady ac voltage with high harmonic into steady same frequency ac sinusoidal voltage with low harmonic. By using uni-polarity phase-shifted control strategy, output filtering inductance current are naturally commutated, and ZVS of the output cycloconverter are realized. The converters' averaging model, the output characteristic curve, and design criteria for the key circuit parameters are given. The theoretical analysis and test result of 1 kVA 220 Vplusmn10%50 HzAC/110 V 50 HzAC prototype have shown that the converters have the advantages such as high frequency electrical isolation, simple topology, two-stage power conversion(LFAC/HFAC/LFAC), bi-directional power flow, uni-polarity SPWM waveform, high efficiency, high power density, high steady precision, low THD of the output voltage, strong adaptability to various loads, high line power factor and low audio noise etc.