A Single-phase AC-DC-AC Three-leg Converter Hybrid with Two and Three Level Legs

An AC-DC-AC unidirectional single-phase converter is presented in this paper. The configuration is composed of a unidirectional rectifier and full controlled inverter and it is made out of two-level and three-level legs, a total of six controlled switches. The three-level leg presents lower voltage stress on switches, when compared with the two-level one (for a same DC-link voltage). Furthermore, it can allow reduction in harmonic distortion for a same switching frequency. Suitable modeling of the systems is presented, as well as a control strategy for synchronization between modulated voltage at grid side and grid current. This control scheme is necessary due to the grid voltage dependence of the current polarity. The SV-PWM strategy is analyzed and balancing of capacitor in DC-link is also shown. Simulated and experimental results are presented as well.