Extended multilevel converters: an attempt to reduce the number of independent DC voltage sources in cascaded multilevel converters

The cascaded multilevel converters are the most favorable topologies of multilevel converters. However, they have the main disadvantage of using multiple independent dc voltage sources. This study proposes new cascaded multilevel converter topologies in which the number of independent dc voltage sources is reduced. In the proposed topologies, for a specific number of voltage levels, the number of dc voltage sources is halved. Beside the number of dc voltage sources, in one of the proposed topologies the number of switches is also reduced in comparison with that of the conventional cascaded multilevel converter. A new modified pulse-width modulation method is presented to control the proposed topologies. Also, a method for compensating non-ideality of the dc voltage sources is presented. Simulation results using PSCAD software as well as experimental results from a laboratory-scale prototype are presented to verify the proposed multilevel converters.