Harmonic distortion of multicarrier PWM strategies in cascaded multilevel converters with unequal DC sources

Calculating in an analytical way the influence of modulation strategies for multilevel converters is a challenging topic, especially if the theoretical and ideal assumptions are not valid. In this paper, a modular multilevel converter, consisting of three H-Bridges is analysed. Based on analytical formulas, a numerical approach is shown to handle the risen complexity due to the risen number of output levels. The influence on the harmonic content of the output voltage is investigated assuming non-ideal DC sources.