A Modular Multilevel Converter with Ripple-Power Decoupling Channels for Three-Phase MV Adjustable-Speed Drives

Mohamed S. Diab*, Ahmed M. Massoud, Shehab Ahmed, Barry W. Williams

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


This paper presents a drive system based on a modular multilevel converter (MMC) with high-frequency magnetic channels between adjacent-arm submodules (SMs), suitable for medium-voltage, high-power three-phase variable-speed machines. The configuration employs chains of dual half-bridge (DHB) modules linking adjacent SMs of three-phase symmetrical arms. The DHB modules are operating as power channels enabling energy exchange to restore the power imbalance among the SM capacitors. This allows arms' ripple-powers to be entirely decoupled through bidirectional power transfer between adjacent-arm SMs, resulting in a near ripple-free SM capacitor voltage profile. Therefore, the MMC common problem of wide voltage fluctuation across SM capacitors is comprehensively solved, independent of the operating frequency. Additionally, a significant reduction in the sizing requirement of SM capacitance is achieved. The configuration is able to drive multimegawatt machines from standstill to the rated speed at the rated torque operating condition. The operating principle of the proposed MMC configuration is explained and necessary mathematical analysis is derived. Features and viability of the proposed drive system are verified through simulation and experimentation.

Original languageEnglish (US)
Article number8416763
Pages (from-to)4048-4063
Number of pages16
JournalIEEE Transactions on Power Electronics
Issue number5
StatePublished - May 2019

Bibliographical note

Publisher Copyright:
© 2018 IEEE.


  • Dual half-bridge (DHB)
  • high-frequency (HF) transformer
  • low motor speed
  • medium-voltage (MV) variable-speed drives
  • modular multilevel converter (MMC)
  • power decoupling
  • submodule (SM) capacitor voltage-ripple

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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