A transient voltage based DC fault line protection scheme for MMC based DC grid embedding DC breakers

Wang Xiang, Junjie Zhan, Lie Xu, Saizhao Yang, Weixing Lin, Jinyu Wen

Research output: Contribution to journalArticlepeer-review

214 Citations (Scopus)
36 Downloads (Pure)


Fast and reliable DC fault detection is one of the main challenges for modular multilevel converter (MMC) based DC grid with DC circuit breakers (DCCBs). This paper extracts the high frequency components of transient voltages by wavelet transform and proposes a fault identification method based on the difference of transient voltages to identify the faulted lines for DC grids using overhead lines. Meanwhile, a faulted pole discrimination method based on the difference between the change of positive and negative pole voltages is presented. A line protection scheme including detection activation, fault identification, faulted pole discrimination and post-fault re-closing is designed. Using only the local measurements, the scheme can realize the protection of the whole line without communication and has the capability of fault resistance endurance and anti-disturbance. The proposed method is tested with a four-terminal MMC based DC grid in PSCAD/EMTDC. The selection methods of threshold values are presented and the impact of DCCB operation on the reliability of DC fault protection is analysed. Simulation results verify the fast detection and reliability of the designed DC line protection scheme.
Original languageEnglish
Pages (from-to)1-12
Number of pages12
JournalIEEE Transactions on Power Delivery
Early online date8 Oct 2018
Publication statusE-pub ahead of print - 8 Oct 2018


  • DC fault protection
  • fault identification
  • transient voltage
  • hybrid DC breaker
  • modular multilevel converter (MMC)
  • post-fault re-closing


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