Research On The Forward AC-AC Mode Three-level AC/AC Converter

A circuit topology of the Forward AC-AC mode three-level AC/AC converter is proposed, and this topology has applied for patents for inventions in China(Number of applications: 200710020946.4). The kind of circuit topologies are constituted of input filter, three-level converter, high frequency transformer, output cycloconverter, output filter and so on. The converter has the advantages such as simple topology, two-stage power conversions(LFAC/HFAC/LFAC), bidirectional power flow, high frequency electrical isolation, three-level voltage across the output filter and so on. The circuit structure is used for transferring the unstable ac voltage with high THD (Total Harmonic Distortion) into a regulated constant frequency sinusoidal voltage.The control strategy, operation modes and steady principles of the proposed converter are investigated in the paper. The time condition of magnetic reset, output voltage harmonic, stress of power switches of the proposed converter are also analysed. Compared with the Forward AC-AC mode two-level AC/AC converter, it could obtain the three-level voltage waveforms across the output filter, reduce the output inductor, and the voltage stress of the power switch could be also lowered. The correction and advance of the new concept of the 1000VA220V±10%50HzAC/110V50HzAC Forward AC-AC mode three-level AC/AC converter is fully verified by PSPICE simulation and principle test. This kind of converter lays the key technical foundation on new-type electronic transformers, regulated sinusoidal ac power supplies and ac regulators.