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The multilevel inverters are one of the great solutions that are proposed to satisfy the demand for high-power application and the significant integration of renewable energy. The conversion process from DC to AC must be done at high efficiency to decrease the energy loss and to ensure the electric grid power quality. The Total Harmonic Distortion (THD) is the most important feature that indicates the efficiency of the conversion process. In this research, due to the advantages of the cascade H-bridge inverter over other topologies, it has been used with the virtual stage PWM technique to investigate two different methods for selective harmonics elimination. The first method is looking from the single-phase perspective, and the second method is looking from the three-phase perspective. A comparison has been done on a wide range of modulation indices using five- and seven- level inverters. The three-phase method provides better results in terms of the THD and the fundamental component. Also, it guarantees the amplitude and shape of output voltage signal in the three-phase application.
Advisor: Mahmoud Alahmad