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Cascaded H-bridge Multilevel Inverter Using New Phase Shifted Carrier Pulse Width Modulation Technique

Ch.Lokeshwar Reddy, P.Satish Kumar, M.Sushama

This paper presents a new Phase shifted carrier PWM technique for Cascaded Multilevel Inverter. The main objective of this technique is to reduce the THD of inverter output voltage. This strategy leads to the cancellation of all carrier and associated sideband harmonics up to 2Nc th carrier group where Ncis the number of H-bridges in a phase. In this modulation process, the switching frequency preferably high to reduce the undesired side effects of discontinuous power flow at switching and to reduce lower harmonics in the output voltage. Comparison of harmonic spectrum for different carrier frequencies and different modulation indexes for a eleven inverter is presented in this paper. This technique can be extended to any number of levels.