Comparison of multi-carrier and SHE-PWM for a nine levels cascaded H-bridge inverter

Multilevel inverters are very important in renewable energy applications. Asymmetrical type of multilevel inverters is used for saving of the number of dc sources, gate drive circuits and bridges. It gives the number of levels for output voltage higher than from symmetrical type. Multi-carrier based sinusoidal pulse width modulation (MCB-SPWM) and the selective harmonic elimination pulse width modulation (SHE-PWM) are commonly types of modulation techniques. The comparison between MCB-SPWM and SHE-PWM is done for a nine levels cascaded H-bridge (CHB) inverter with asymmetrical type to show the advantages of two types of PWM techniques. The difficulty of SHE-PWM is a solution of the non-linear transcendental equations of SHE. To solve this difficulty, Evolutionary algorithms such as genetic algorithm are used to find optimal switching angles. MCB-SPWM and SHE-PWM are performed by MATLAB / SIMULINK software packages.