A Single Stage Multilevel Converter Based on Transformer Multi-tap Voltages Control Fed by Low DC Voltage Source

In photovoltaic power generation, UPS and other applications, DC/AC converters with a low input DC voltage are essentially used. However, this type of converter is commonly put to use the traditional two-level converting topology, which results problems of high harmonic content in the output voltage and large power loss. Therefore, a single stage multilevel converter based on transformer multi-tap voltages control fed by a low DC voltage source (MCMTVC) is proposed in this paper. The converter achieves multi levels by control different transformer tap voltages through the power switches connected to the taps, and the number of output levels can be conveniently expanded through the expansion of the transformer taps. During operation, the power switch branches that each branch is connected in series by at most two power transistors including power diodes take turns to serve power exchange, and the voltage stress upon the power switches active in PWM state is very low. The principle of the converter is described in this paper in the first, and then the corresponding control method is put forward, furthermore the characteristics of the converter are discussed. In final, A 9-level simulation platform with the mentioned topology and control strategy using the MATLAB / Simulink software is established, and then simulation research is carried out, whose results have verified the proposed control strategy and conclusions.