Hybrid converter topologies for dc transmission systems

Grain Philip Adam, Fahad Alsokhiry, Ibrahim Abdelsalam, John Fletcher, Lie Xu, Yusuf Al-Turki

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Abstract

This study presents types 1 and 2 hybrid converters with reduced power circuit complexity compared with the mixed cell modular multilevel converter (MC-MMC). The type 1 converter is formed by replacing the director switches of the alternate arm converter by high-voltage (HV) half-bridge (HB) cells rated for half of the dc-link voltage. Also, it resembles special case of MC-MMC, where the entire HB cells of each arm are lumped into a single HV HB cell, with both capacitors of the half- and fullbridge cells are exposed to fundamental current as in the conventional MMC. The upper and lower arms of the type 2 converter resemble a front-to-front connection of two three-phase hybrid cascaded two-level converters, where the cell capacitors of the three-phase two-level converters that act as director switches do not experience fundamental currents. Therefore, the type 2 converter offers compact design compared with type 1 converter and the MC-MMC. The technical viabilities of the proposed hybrid converters are assessed using simulations, with both converters modelled in MATLAB-Simulink using electromagnetic transient simulation approach, considering normal and transient conditions. Experimental results obtained from single-phase type 1 converter confirm the practical viability of the proposed converters.

Original languageEnglish
Pages (from-to)607-619
Number of pages13
JournalIET Power Electronics
Volume12
Issue number3
Early online date29 Nov 2018
DOIs
Publication statusPublished - 20 Mar 2019

Keywords

  • hybrid converters
  • mixed cell converter
  • MC-MMC

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