Quasi two-level operation of modular multilevel converter for use in a high-power DC transformer with DC fault isolation capability

I. A. Gowaid, G. P. Adam, Ahmed M. Massoud, Shehab Ahmed, Derrick Holliday, B. W. Williams

Research output: Contribution to journalArticle

168 Citations (Scopus)

Abstract

DC fault protection is one challenge impeding the development of multi-terminal DC grids. The absence of manufacturing and operational standards has led to many point-to-point HVDC links built at different voltage levels, which creates another challenge. Therefore, the issues of voltage matching and DC fault isolation are undergoing extensive research and are addressed in this paper. A quasi two-level operating mode of the modular multilevel converter is proposed, where the converter generates a square wave with controllable dv/dt by employing the cell voltages to create transient intermediate voltage levels. Cell capacitance requirements diminish and the footprint of the converter is reduced. The common-mode DC component in the arm currents is not present in the proposed operating mode. The converter is proposed as the core of a DC to DC transformer where two converters operating in the proposed mode are coupled by an AC transformer for voltage matching and galvanic isolation. The proposed DC transformer is shown to be suitable for high-voltage high-power applications due to the low switching frequency, high efficiency, modularity, and reliability. The DC transformer facilitates DC voltage regulation and near instant isolation of DC faults within its protection zone. Analysis and simulations confirm these capabilities in a system-oriented approach.
LanguageEnglish
Pages108-123
Number of pages16
JournalIEEE Transactions on Power Electronics
Volume30
Issue number1
Early online date14 Feb 2014
DOIs
Publication statusPublished - 24 Aug 2014

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DC transformers
Electric potential
Switching frequency
Voltage control
Capacitance

Keywords

  • modular multilevel converter
  • DC fault protection
  • multi-terminal DC grids

Cite this

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abstract = "DC fault protection is one challenge impeding the development of multi-terminal DC grids. The absence of manufacturing and operational standards has led to many point-to-point HVDC links built at different voltage levels, which creates another challenge. Therefore, the issues of voltage matching and DC fault isolation are undergoing extensive research and are addressed in this paper. A quasi two-level operating mode of the modular multilevel converter is proposed, where the converter generates a square wave with controllable dv/dt by employing the cell voltages to create transient intermediate voltage levels. Cell capacitance requirements diminish and the footprint of the converter is reduced. The common-mode DC component in the arm currents is not present in the proposed operating mode. The converter is proposed as the core of a DC to DC transformer where two converters operating in the proposed mode are coupled by an AC transformer for voltage matching and galvanic isolation. The proposed DC transformer is shown to be suitable for high-voltage high-power applications due to the low switching frequency, high efficiency, modularity, and reliability. The DC transformer facilitates DC voltage regulation and near instant isolation of DC faults within its protection zone. Analysis and simulations confirm these capabilities in a system-oriented approach.",
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Quasi two-level operation of modular multilevel converter for use in a high-power DC transformer with DC fault isolation capability. / Gowaid, I. A.; Adam, G. P.; Massoud, Ahmed M.; Ahmed, Shehab; Holliday, Derrick; Williams, B. W.

In: IEEE Transactions on Power Electronics, Vol. 30, No. 1, 24.08.2014, p. 108-123.

Research output: Contribution to journalArticle

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