Three-Phase Hybrid Cascaded Multilevel Inverter Using Topological Modules With 1:7 Ratio of Asymmetry

Asymmetrical cascaded topology can produce more number of levels. This can be further boosted by using level doubling networks (LDNs). An LDN is a floating capacitor fed two-switch topology that almost doubles the number of levels without necessitating any closed-loop control for the voltage balancing of the floating capacitors. Topological modules (TMs) are formed by using LDN. This paper shows the uniqueness of 1:7 ratio of asymmetry (between the TMs) to maximize the number of levels without having any loss in the intermittent voltage levels for the line-to-line voltage in a three-phase system. A new control technique to select the right space vector without generating any dc component in the output phase voltage is reported. Step-by-step description of the controller is presented in this paper. Extensive simulations using MATLAB/Simulink and supporting experimental results using a laboratory prototype have confirmed the usefulness of the proposed controller.