Topology for cascaded multilevel inverter

This study presents a topology for cascaded multilevel inverter (MLI). Each module is made up of H- and half-bridges, two isolated equal dc sources and a bidirectional auxiliary circuit. One leg of the H-bridge and the half-bridge are cut and the corresponding terminals are connected to the both ends of an equal split dc source. The free ends of the half-bridge are connected together to form a common output node of the inverter. The auxiliary circuit is inserted between the midpoint of the split dc sources and this very output node. The output point of the uncut leg of the H-bridge forms the remaining output node. With this circuit arrangement, proper control of the switches in the bridges and the auxiliary circuit, in each cascaded cell, can produce nine output voltage levels. A comparison is made between the proposed inverter, classical CHB and some of the recent developed MLI topologies with respect to specified figure of merits, as well as the per unit power losses. For two cascaded modules, simulation and experimental verifications are carried out on the proposed inverter topology for an R-L load; adequate results are presented.