Implementation and development of modulation strategies in asymmetric multilevel inverter

Abstract

In this thesis, an Asymmetric Trinary Multilevel Inverter (ATMLI) for induction motor drive is analyzed and the overall performance is investigated by various modulation strategies using mathematical analysis and simulation studies. Multilevel inverter is more efficient for medium voltage and high power applications with better harmonic spectrum of AC motor drives. Induction motor is used for constant speed applications due to newlineruggedness and robustness. The performance of the induction motor is affected by the newlineconventional inverter because of the high Total Harmonic Distortion (THD) it produces. Hence, this work focuses on cascaded MLI topology for AC drives. Cascaded multilevel inverter has a high modularity degree feature such that each inverter has a module with similar circuit, control structure, and modulation. As a result, these modules can be replaced quickly and easily in case of a fault. An asymmetric trinary MLI (ATMLI) with reduced number of switching devices is developed. Normally, n DC sources would be required for (2n+1) levels but here n/2 DC sources is required which reduces the newlineswitching loss, improves the efficiency of the system and voltage unbalance problem is eliminated newline newline newline