A novel method for real-time selective harmonic elimination in five-level converters

Multilevel converters are attractive solution for high-power high-voltage applications such as motor drive systems, active filters, and flexible AC transmission systems (FACTS). Several modulation techniques are proposed for multilevel converters. Among them, selective harmonic elimination (SHE) offers high quality voltage waveform with low switching frequency which is especially suitable for high-power applications. This paper proposes a novel method for real-time implementation of SHE modulation technique in five-level converters. Using this method, all possible sets of solutions and the exact value of switching angles are determined by a very simple formulation. Furthermore, this technique systematically suggests three-level output waveform to extend the minimum value of modulation index to zero for each eliminated harmonic. To verify the validity of the proposed algorithm, simulation and experimental results for a single phase five-level diode-clamped inverter are reported.