Research On The Uni-polarity Phase-shifted Controlled Voltage Mode AC/AC Converters With High Frequency AC Link

Abstract:The uni-polarity phase-shifted controlled voltage mode AC/AC converters with high frequency ac link based on Forward converters are firstly proposed and deeply investigated.This kind of converters is constituted of input cycloconveter,high frequency transformer,output cycloconverter,input and output filters. It includes full bridge-full wave mode and full bridge-full bridge mode topologies,the former is suit for low output voltage field and the later is suit for high output voltage field. The unsteady input commercial frequency sinusoidal voltage with high harmonic is modulated into bi-polarity three-state high frequency ac volage by the input cycloconverter,bi-polarity three-state high frequency ac volage is demodulated into uni-polarity three-state SPWM wave by the output cycloconverter,and the uni-polarity three-state SPWM wave is filter into steady commercial frequency sinusoidal voltage with low harmonic. By using phase shifting control between right bridge leg and left bridge leg,the output cycloconverter commutating while the bi-polarity three-state high frequency ac volage from the input cycloconveter is zero,.and commutation overlap of the output cycloconverter and polarity selection of the input voltage,the leakage inductance energy and the output filtering inductance current are naturally commutated,and ZVS switching of the output cycloconverter are realized,the surge voltage and surge current of the output cycloconverters are overcome. The twelve kinds of modes and equivalent circuits within one high frequency switching period are carefully analyses.By using the state-space averaging approach,the converter's averaging model is presented,the output characteristic curve and design criterion of key circuit parameters such as output voltage,filtering inductance,common conduction time,uni-polarity SPWM waveform's duty cycle etc are given. This kind of converter has the advantages such as high frequency electrical isolation,simple topology,two-stage power conversion(LFAC/HFAC/LFAC),high power density,bi-directional power flow,soft commutation of output cycloconverter,uni-polarity SPWM waveform,no audio noise etc.The correction and advance of the new concept of the 220V + 10%(50Hz)/220V(50Hz) uni-polarity phase-shifted controlled voltage mode AC/AC converter with high frequency . ac link is fully verified by the simulation and the pricinple test.This kind of converter lay the key technical foundation on new type electronic transformer,regulated sinusoidal ac power supply,ac regulator.