Switching Frequency Analysis of Staircase-Modulated Modular Multilevel Converters and Equivalent PWM Techniques

G. Konstantinou, J. Pou, Salvador Ceballos, R. Darus, V.G. Agelidis

Research output: Contribution to journalArticlepeer-review

63 Citations (Scopus)

Abstract

The large number of voltage levels in a modular multilevel converter (MMC) make staircase modulation a feasible alternative, particularly in high-power applications. However, staircase waveforms do not necessarily mean operation of the MMC submodules (SMs) at the fundamental frequency. This paper presents an analysis of SM switching frequencies in staircase-modulated MMCs and their correlation to the modulation index and load phase angle. A carrier-based pulsewidth-modulation (CB-PWM) equivalent technique is also developed. This analysis demonstrates that CB-PWM techniques provide a similar switching frequency with superior harmonic performance and improved voltage balancing characteristics at all modulation indices compared to staircase modulation. The theoretical analysis is verified with extensive simulation results for MMCs with different SMs and experimental results from a laboratory prototype.
Original languageEnglish
Article number7070753
Pages (from-to)28-36
Number of pages9
Journalunknown
Volumeunknown
Issue number1
DOIs
Publication statusPublished - Feb 2016

Keywords

  • Modular multilevel converter (MMC)
  • Multilevel converters
  • Pulsewidth modulation (PWM)

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