Cascaded Multilevel Inverter Using Quasi Resonant Switched Capacitor Units

Abstract

In this research, two novel topologies made up of combined customary H-bridge and quasi-resonant switched-capacitor inverter units are introduced for multi-level inverters. Compared to conventional topologies, the proposed topologies need a lower quantity of dc voltage sources and switches and smaller system size and cost. Furthermore, the proposed topologies do not require a transformer to enhance the input voltage. In the proposed topologies, the series-connected capacitors divide the voltage input equally, and the desired voltage may be attained via increasing the basic unit. With respect to the frequency of switching and the consequent loss, fundamental frequency modulation is preferable. In order to simultaneously prevent the current spikes due to the instantaneous parallel connection between the input source and the capacitors connected in series, reduce the capacitance, decrease the electromagnetic interference, and improve capacitor lifetime, the quasi-resonance method is utilized. To demonstrate the correct working of the proposed topologies, simulation results corresponding to 13-level and 17-level single-phase inverters are provided.