New configurations for the three-phase asymmetrical multilevel inverter

This paper deals with cascade multilevel inverters. It focuses on asymmetrical topologies where the cell input voltages are of different values. These hybrid topologies might be used in several applications. Nevertheless, the need of DC-DC converters to supply the cells of reversible multilevel converters increases the cost and losses of such inverters. It limits their application field. Furthermore, the simultaneous-commutation problem, which increases the switching losses for some operating points, reduces the design choice to configurations of lower resolution. Combining in series a 3-phase 6-switch voltage source inverter with single phase H-bridges, we obtain an asymmetrical hybrid cascaded multilevel inverter with advantageous properties in terms of voltage resolution and energetic efficiency. This paper describes the design and use of such a structure, the way to increase the asymmetrical multilevel inverters resolution.