An integrated control and protection scheme based on FBSM-MMC active current limiting strategy for DC distribution network

Tao Zheng, Wenxuan Lv, Qiong Wu, Rui Li, Xiaoxiao Liu, Chengqi Zhang, Lie Xu

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Abstract

DC faults can easily lead to overcurrent in DC distribution networks; these faults pose serious threats to the safe operation of the system. The blocking of modular multilevel converters based on the full-bridge sub-modules (FBSM-MMC) is mostly utilized to cut off the fault current. However, the blocking causes short-term blackouts in the entire DC distribution network and there are presently no effective solutions to address this problem. In this study, an integrated control and protection scheme based on the FBSM-MMC active current limiting strategy is proposed. The project includes three stages: first, MMC active current limiting strategy is used to limit the output current of the converter to about 1.2 p.u. after the occurrence of the fault (Stage 1); next, faulty lines are identified based on the asynchronous zero-crossing features of the DC currents of the two ends of the line (Stage 2); then, a fault isolation scheme based on the cooperation of converters, DC circuit breakers, and high-speed switches is proposed to isolate the faulty line (Stage 3). The distribution network can restart quickly via control of the converters. Finally, the simulation of a four-terminal flexible DC distribution network in PSCAD/EMTDC demonstrates the effectiveness of the proposed integrated scheme.
Original languageEnglish
Number of pages11
JournalIEEE Journal of Emerging and Selected Topics in Power Electronics
Early online date6 Aug 2020
DOIs
Publication statusE-pub ahead of print - 6 Aug 2020

Keywords

  • flexible DC distribution network
  • full-bridge sub-modules
  • converter active current limiting control
  • current zero-crossing detection
  • integrated control and protection scheme

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