Performance Evaluation of Asymmetrical Cascaded H-Bridge Multilevel Inverter

A power electronic converters are becoming more and more popular for medium voltage & high power applications. To overcome the limitation of semiconductors current and voltage ratings in high power applications, multilevel inverter is often considered an effective solution. In addition, stepped waveform in the output of multilevel inverter has better harmonic spectrum than 2-level inverter in low switching frequencies. So, in recent years multilevel inverters have gained great interest in industry. Among the different solutions available for multilevel converters, the cascaded H-Bridge multilevel inverter are modular in nature and its asymmetric topologies allow to generate more voltage levels with less number of semiconductors and thus increase of output performance and system reliability. For these reasons, this kind of topology has attracted a lot of attention both from the customers and manufacturers view.This paper presents an asymmetrical cascaded H-Bridge multilevel inverter in three phase configuration using fixed frequency level shifted carrier based pulse width modulation technique feeding a three phase squirrel cage induction motor. This new control scheme is applied to 7, 9, 15 and 27 level asymmetrical cascaded H-Bridge multilevel inverter. Simulation using MATLAB/SIMULINK is done to verify the performance of all levels of an asymmetrical cascaded H-Bridge multilevel inverter.