Analytical calculation of the harmonic effects of single phase multilevel PWM inverters

This paper presents an analytical approach for determining the total harmonic distortion THD and its weighted value WTHD for multi level PWM inverters. The calculation considers one single phase having MVDC systems in mind. Although the analysis is based on the assumption of a high number of pulses, the developed equations can also be applied for lower frequency ratios fs/f1. The analytical formulas require the characteristic parameters of the PWM only, which are the modulation factor m, the switching frequency fs, the fundamental frequency f1, the effective inductance L and the DC link voltage Uo. Two, three and five voltage-level inverters are considered.