A three phase 3-level inverter with reduced THD factor

Abstract

The paper presents an mathematical analysis of a stepped function denoted as fN=6 . This function describes precisely an output voltage waveform of a 3-level inverter. The analysis proves that cascaded inverters give a very good performance of the output voltage according to a criterion of minimal THD. Optimal parameters are indicated in the paper. They permit to diminish the THD factor to a level below 21% while in standard NPC inverters such a result requires special treatment.