Formulation of the line voltage THD, case I: Multilevel inverter with equal DC sources

A new generation of DC to AC inverters which is called Multilevel Inverter, has many industrial applications, especially in high-voltage and high-power. In spite of nearly sinusoidal waveform, multilevel inverters produce noticeable harmonic content. THD is normally used as a benchmark to evaluate harmonic contents. THD is one of important factors to produce losses in devices such as induction motors, transformers and etc. Also the Losses play an important role in determining the size of distribution cables, so calculation of the exact amount of THD is important. In previous studies, a formula to calculate exact THD of phase voltage has been emerged for multilevel inverter with equal DC sources. In this paper, line to line voltage THD formula for 3 and 5-level inverter instead of the past approximate methods is offered. For writing codes and simulations MATLAB software is used.