Influence of third harmonic injection on MMC-based HVDC transmission systems

Rui Li, John E. Fletcher, Barry W. Williams

Research output: Contribution to journalArticlepeer-review

73 Citations (Scopus)
351 Downloads (Pure)


Whilst third harmonic injection is extensively used in modular multilevel converter (MMC) control, its significant advantages over sinusoidal modulation have not been fully explored. This paper evaluates the influence of third harmonic injection on system power losses, submodule capacitance, circulating current, and fault current and mathematical models are derived. Station conduction losses are reduced by 11%, yielding higher efficiency and lowering cooling system capacity. The submodule capacitance is reduced by 24%, which significantly lowers the capital cost, weight, and volume of the station converter. Additionally, the phase energy variation is reduced by around 18%, which benefits circulating current control. Due to the lower AC currents, the semiconductor current stresses are correspondingly reduced. In addition to the performance improvement in normal operation, the third harmonic injection reduces the DC fault currents by 13.4% and thus the fault current stresses on semiconductors and DC circuit breakers are lowered. Simulation of a point-to-point HVDC system demonstrates the effectiveness of the above analysis.
Original languageEnglish
Pages (from-to)5764-2770
Number of pages7
JournalIET Generation, Transmission and Distribution
Issue number11
Publication statusPublished - 4 Aug 2016


  • DC fault current
  • HVDC transmission
  • modular multilevel converter (MMC)
  • power loss
  • submodule capacitance
  • third harmonic injection


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  • University of New South Wales (UNSW)

    Rui Li (Visiting researcher)

    Nov 2015Jan 2016

    Activity: Visiting an external institution typesVisiting an external academic institution

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