Optimal Operation of Soft Open Points in Active Distribution Networks Under Three-Phase Unbalanced Conditions

Fei Ding, Peng Li, Haoran Ji, Chengshan Wang, Jinli Zhao, Guanyu Song, Jianzhong Wu

Research output: Contribution to journalArticlepeer-review

150 Scopus Citations


The asymmetric integration of distributed generators (DGs) exacerbates the three-phase unbalanced condition in distribution systems. The serious unbalanced operation causes inefficient utilization of network assets and security risks in the system. Soft open point (SOP) is a flexible power electronic device which can achieve accurate active and reactive power flow control to balance the power flow among phases. This paper proposes an SOPs-based operation strategy for unbalanced active distribution networks. By regulating the operation of SOPs, the strategy can reduce power losses and simultaneously mitigate the three-phase unbalance of the upper-level grid. Semidefinite programming (SDP) relaxation is advocated to convert the original non-convex, nonlinear optimization model into an SDP formulation, which can be efficiently solved to meet the requirement of rapid adjustment. Case studies are conducted on the modified IEEE 33-node and IEEE 123-node distribution system to verify the effectiveness and efficiency of the proposed strategy.

Original languageAmerican English
Article number8010861
Pages (from-to)380-391
Number of pages12
JournalIEEE Transactions on Smart Grid
Issue number1
StatePublished - Jan 2019

Bibliographical note

Publisher Copyright:
© 2010-2012 IEEE.

NREL Publication Number

  • NREL/JA-5D00-68305


  • Active distribution network
  • distributed generator (DG)
  • semidefinite programming
  • soft open point (SOP)
  • unbalanced operation


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