Research On Single-state Boost-buck Inverter

Renewable energy sources, particularly solar energy and wind energy will gradually replacefossil energy to become the main energy supply of the human society with the gradual depletion offossil energy and the increasingly serious environmental problems. Renewable energy powergeneration become the focus of the study. The output voltage of renewable energy generating deviceis low and varies a lot due to environment, climate and other geographical factors, and converters needinversion and boost when used for power generationThis paper proposes a novel single-state inverter topology based on the structure of “virtualtransformer. The new topology is constituded by full-bridge and Boost AC/AC, and two parts sharethe same inductor and capacitor, which could achieve inversion and boost in single stage powerconversion. The “virtual transformer”(Boost AC/AC) composed of high frequency power switch withvoltage ratio determined by the relationship of the DC input voltage and the peak of output ACvoltage achieves a constant voltage boost, and the boost ratio continuously adjustable. There is nolarge capacitor in DC bus, and fewer capacitor and inductor compared with two-stage structure: boost+full-bridge. Thus the volume is reduced and power density is improved.Time-sharing dual mode of modulation maximizes the use of the DC input voltage and reducesthe number of high frequency devices, reducing the switching losses and improving efficiency. Itsoperation principle is based on relationship of the DC input voltage and the instantaneous AC outputvoltage. Through the carrier wave up or modulation wave down, the converter operates in the step-upor step-down modes with different equivalent circuit, and different modes are analyzed. Comparisonof the inductor current and current stress of switch with the constant voltage ratio modulation iscarried out.A500W experimental prototype is designed to verify the correctness of the theoretical analysis.Experimental is carried out, and the results show that the proposed topology is able to achieve a widerange of buck-boost inverter function in the two modulation methods.