Nigerian Journal of Technology

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Fundamentals of a Multi-Phase, Neutral-Point Clamped Multilevel Inverter

CI Odeh


The conventional five-level diode-clamped inverter suffers from the problem of many active power switches when extended to multiphase system. As a consequence, increasing number of gate drive circuits are required; resulting in complex system circuitry. This paper presents the fundamentals of a multiphase, neutral point clamped multilevel inverter configuration capable of reducing the number of active power switches in the conventional topology for multiphase system. The proposed multilevel inverter configuration generates five line-to-line voltage levels for multiphase systems. From the generalized model, an exemplary 5-phase, 5-level line-line NPC inverter supplying an RL load is considered. The operational and modulation principles and the switching patterns are outlined. The THD, as a performance index, of the line voltage output waveform of the proposed 5-phase, 5-level line-line NPC inverter is similar to that of the corresponding well-known conventional 5-phase, NPC diode-clamped inverter. The proposed inverter achieves this with fewer power circuit components and simplicity. The validity of the proposed multilevel inverter is verified through simulations and experimental results.
AJOL African Journals Online