Quasi-two-level and three-level operation of a diode-clamped multilevel inverter using space vector modulation

Adam, Grain Philip and Finney, Stephen and Ojo, O. and Williams, Barry (2012) Quasi-two-level and three-level operation of a diode-clamped multilevel inverter using space vector modulation. IET Power Electronics, 5 (5). 542 - 551. ISSN 1755-4535

Abstract

This study presents space vector-based quasi-two-level operation of a diode-clamped multilevel inverter which improves dc link utilisation and output voltage quality, and avoids the dc link capacitor voltage balancing problem experienced with standard multilevel operation. Beside a review of quasi-two-level operation and the capacitor voltage balancing method, the study presents a detailed discussion on the implementation of space vector modulation and the selection of switching sequence for a five-level inverter. Additionally, the condition for maximum theoretical modulation index for space vector modulation is established. A prototype five-level diode-clamped inverter is to experimentally validate the approach. Also this study extends the concept of quasi-two-level-to-three-level operation of the diode-clamped multilevel inverter in order to address the shortcomings experienced with quasi-two-level operation, such as low waveform quality and high switching losses. The validity of three-level inverter operation is confirmed experimentally on a prototype of a five-level diode-clamped inverter. The study also highlights the limitations of three-level operation of a diode-clamped multilevel inverter.

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