New efficient sub-module for modular multilevel converter in multi-terminal HVDC networks

Grain Philip Adam, Ibrahim Abdelsalam, John Edward Fletcher, Graeme Burt, Derrick Holliday, Stephen Jon Finney

Research output: Contribution to journalArticlepeer-review

44 Citations (Scopus)
154 Downloads (Pure)


In high-voltage applications, the magnitude of total semiconductor losses (on-state and switching) determines the viability of modular type multilevel converters. Therefore, this paper presents a new cell arrangement that aims to lower total semiconductor loss of the modular multilevel converter (MMC) to less than that of the half-bridge modular multilevel converter (HB-MMC). Additional attributes of the proposed cell are: it eliminates the protective thyristors used in conventional half-bridge cells that deviate part of the dc fault current away from the anti-parallel diode of the main switch when the converter is blocked during a dc short circuit fault; and it can facilitate continued operation of the MMC during cell failures without the need for a mechanical bypass switch. Thus; the MMC that uses the proposed cell retains all advantages of the HB-MMC such as full modularity of the power circuit and internal fault management. The claimed attributes of the proposed cell are verified using illustrative simulations and reduced scale experimentations. Additionally, this paper provides brief and critical discussions that highlight the attributes and limitations of popular MMC control methods and different MMC cells structures proposed in the literature, considering the power electronic system perspective.
Original languageEnglish
Pages (from-to)4258-4278
Number of pages21
JournalIEEE Transactions on Power Electronics
Issue number6
Early online date25 Aug 2016
Publication statusE-pub ahead of print - 25 Aug 2016


  • flying capacitor cell
  • half and full bridge modular multilevel converter
  • mixed - cell commutation ce lls
  • voltage source converter high - voltage direct current transmission systems
  • HB-MMC

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