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A Unidirectional Hybrid HVDC Transmission System Based on Diode Rectifier and Full-Bridge MMC

  • Rui Li*
  • , Lie Xu
  • *Corresponding author for this work
  • University of Strathclyde

Research output: Contribution to journalArticlepeer-review

Abstract

To reduce the cost of bulk power transmission using voltage source converter high-voltage DC (HVDC) technology, a unidirectional hybrid converter is proposed, where a diode rectifier (DR) and a modular multilevel converter (MMC) based on full-bridge (FB) submodules are connected in series on DC side. The FB-MMC controls its DC voltage to regulate the transmitted power. The majority of the power transmission is via the DR considering its cost and efficiency superiority and only low power rating FB-MMC is required. A thyristor valve is equipped at the DC side of the FB-MMC to prevent potential overcharge of the FB submodules during DC faults. Compared to conventional MMCs, losses can potentially be reduced by around 20%. An active power controller is proposed to regulate the DC voltage of the FB-MMC so as to control the transmitted power. With the inverter station controlling its DC terminal voltage constant, the FB-MMC increases the output DC voltage to increase the transmitted power and vice versa. To alleviate overvoltage of the HVDC link during AC grid faults of the inverter station, a dynamic DC voltage limiter is designed to actively reduce the DC output voltage of the FB-MMC. Simulation results confirm the proposed converter operation and control.

Original languageEnglish
Pages (from-to)6974-6984
Number of pages11
JournalIEEE Journal of Emerging and Selected Topics in Power Electronics
Volume9
Issue number6
DOIs
StatePublished - 1 Dec 2021
Externally publishedYes

Keywords

  • Active power control
  • HVDC transmission
  • diode rectifier high-voltage DC HVDC (DR-HVDC)
  • fault ride-through
  • full-bridge (FB)-based modular multilevel converter (MMC)

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