Buck-Boost single-stage three-level AC/AC converter

A novel circuit topology of buck-boost three-level single-stage AC/AC converter is proposed in this paper. The voltage stress of power switches of this converter is half of that of two-level converter. The transient voltage feedback control strategy of the converter is investigated. According to the polarity of the output voltage and the output current, the converter contains four kinds of operation modes. Each operation mode is equal to a three-level DC/DC buck-boost converter. The operation principle of the converter is analyzed in details. The external characteristic of this converter is analyzed in CCM mode and DCM mode. This converter, which is suit for high input voltage field, has many advantages such as low voltage stress of the switches, single-stage power conversion, three-level voltage waveform of the inductor for storing energy, boost and buck continuously adjustable output voltage, low THD of output voltage, strong load adapting ability, etc. The correction and advance of the kind of converters are verified by experiment.