Multilevel direct PWM AC-AC converters

Due to an increase in power demand, different direct AC-AC conversion structures were developed. Classical direct converters present the disadvantage of a high harmonic content and the consumption of reactive power. For these reasons, different classes of PWM AC choppers were developed during the last decade. Of these solutions, two-level and four-level PWM AC choppers are presented. Multilevel converters using the flying capacitor (FC) concept present the advantages of a lower voltage stress in the semiconductor devices, increased apparent frequency and lower output filters being useful for medium voltage static compensation (STATCOM) applications.