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.

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Multilevel inverters have attractive features which make them one of the most popular fields of investigations. They can operate in high power and high voltage conditions. Multilevel inverters generate output voltage with high quality and low harmonic contents. As the number of output voltage levels increases, the quality of the output voltage is improved leading to reduction of the filtering requirements. However, multilevel inverters have the disadvantage of increased power electronic switches. This leads to higher cost, size and complication. Some advanced topologies have been introduced to reduce the number of power electronic switches, unfortunately, most of these topologies need high voltage switches on their structure making them unsuitable for high voltage conditions. In this study, an innovative topology for multilevel inverter is proposed which reduces the number of switches considerably without using high voltage switches. The proposed topology is a general topology which can be extended for any number of voltage levels. The authors call this topology as cross-switched multilevel inverter. The simulation results obtained in PSCAD/EMTDC as well as the experimental results verify the proposed topology.