New asymmetrical cascade multicell converter based on optimized symmetrical modules

Due to voltage limitation of available semiconductor switches, multicell converters are required for high-power medium-voltage applications. One of the most significant types of multicell converters is cascade multicell converter categorized into symmetrical and asymmetrical ones. This paper first presents a new symmetrical cascade multicell converter in which the number of switches is optimized. An advantage of the proposed symmetrical cascade multicell converter is that the number of required switches in comparison with the conventional symmetrical cascade multicell converter is decreased 50%. Afterwards, a novel asymmetrical cascade multicell converter constructed by the proposed modules of optimized symmetrical converter is presented. The proposed topologies, both symmetrical and asymmetrical cascade multicell converters, are simulated using PSCAD/EMTDC software and simulation results are presented to validate the effectiveness and advantages of the proposed configurations as well as their control strategy.