Modular multilevel structure of a high power dual active bridge DC transformer with stepped two-level output

Azmy Gowaid, G. P. Adam, A. M. Massoud, S. Ahmed, D. Holliday, B. W. Williams

Research output: Chapter in Book/Report/Conference proceedingConference contribution

21 Citations (Scopus)


This paper addresses the issues of dc voltage matching and dc fault protection in potential super-grids. An approach for high power dc-dc conversion is proposed and analyzed. A front-to-front connection of modular-multilevel converters (MMC) forms a dual active bridge (DAB)-like structure. Near two-level operation is achieved by sequential switching of half-bridge chopper cells. This alleviates dv/dt stress exercised by two-level DAB configurations on the ac stage. The operating mode, switching patterns necessary are distinct from conventional MMC. Furthermore, common-mode currents, cell capacitance size, arm inductances are significantly reduced. The considered structure is shown to be useful for high power applications due to the low switching frequency, modularity, reliability and dc fault isolation capability. Various operation aspects are illustrated using simulations. A reduced-scale test rig provides an experimental proof of the concept.
Original languageEnglish
Title of host publication2014 16th European Conference on Power Electronics and Applications, EPE-ECCE Europe 2014
Number of pages10
ISBN (Electronic)9781479930159
ISBN (Print)9781479930166, 9781479930142
Publication statusPublished - 29 Sep 2014


  • DC-DC power convertors
  • bridge circuits
  • choppers (circuits)
  • switching convertors
  • DC fault isolation
  • DC fault protection
  • DC voltage matching
  • DC-DC power conversion
  • dual active bridge-like structure
  • half bridge chopper cell
  • high power dual active bridge DC transformer
  • modular multilevel converters
  • modular multilevel structure
  • sequential switching
  • stepped two level output transformer
  • Bridge circuits
  • Capacitance
  • Capacitors
  • Inductance
  • Power transformer insulation
  • Switches
  • HVDC
  • High voltage power converters
  • Multilevel converters
  • Power transmission
  • Voltage Source Converter (VSC)


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