An unfixed piecewise-optimal reactive power-flow model and its algorithm for AC-DC systems

Juan Yu, Wei Yan, Wenyuan Li, C. Y. Chung, K. P. Wong

Research output: Journal article publicationJournal articleAcademic researchpeer-review

51 Citations (Scopus)


A novel ac-dc optimal reactive power flow (ORPF) model with the generator capability limits is proposed. The objective is to minimize the total cost of generator reactive and active power outputs paid by an independent transmission company. In the model, the generator operation area is divided into four parts with each one having a different reactive output cost function. The boundaries between the four parts change with operation states of generators and are unfixed. The model is an unfixed piecewise mixed-integer nonlinear programming problem. A heuristic approach is introduced into the interior point method to solve the unfixed piecewise problem. The numerical results of six test systems that range in size from 14 to 2572 buses demonstrate the effectiveness of the proposed method.

Original languageEnglish
Pages (from-to)170-176
Number of pages7
JournalIEEE Transactions on Power Systems
Issue number1
Publication statusPublished - Feb 2008


  • AC-DC power system
  • Capability limits of synchronous generator
  • Generator reactive power costs
  • Interior point method (IPM)
  • Optimal reactive power flow (ORPF)

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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