Paper Title
Comparative Study of the Suitable Modulation Methods for Cascade H-Bridge Multilevel Inverter

Abstract
Power quality is a very important issue, and it is of interest to researchers working to reduce its negative effects on power devices. Harmonics are one of the most important factors in power quality and play an important role in the stability of power supply, and therefore inverters that have less harmonics are very attractive. In this paper, several modulation methods for cascade H-bridge multi-level inverters such as multicarrier SPWM, specially the best one, phase opposite disposition and staircase modulation method are investigated. Load voltage and THD harmonic distortion are established and compared with each other to obtain the best modulation method for cascade multi-level inverters to provide high quality power. This conclusion is reached using Simulink/MATLAB simulation. The results shows that staircase modulation method is superior to phase opposite disposition method and in addition its hardware is simpler. The modularity of the staircase modulation implementation is also more flexible than the other method. There are also some technical considerations that are effective in improving power quality. Keywords - Triangular carrier waveform, Phase opposition disposition (POD), Total harmonics distortion, Photovoltaic system, multilevel inverter, 11-level CMLI.