Selective harmonic elimination in a seven level cascaded multilevel inverter based on graphical analysis

One of the big concerns in power conversion systems is the amount of harmonic content. This paper considers a seven level cascaded inverter and proposes a simple graphical approach, useful to obtain three switching angles which, if applied to the inverter, eliminates two harmonics. The method has been further improved for mitigating some additional harmonics. The effect of modulation index on variation of angles is also investigated and total harmonic distortion (THD) is calculated for selected modulation indexes. The proposed modulation operates at fundamental frequency, which means high inverter efficiency due to reduced power losses. Simulation and experimental results are obtained to show the effectiveness of the proposed procedure.