Real-Time Volt/VAr Control Based on the Difference between the Measured and Forecasted Loads in Distribution Systems

  • Park, Jong-Young (Electric Power System & Economics Lab., Seoul National University) ;
  • Nam, Soon-Ryul (Next-Generation Power Technology Center (NPTC) and the Department of Electrical Engineering, Myongji University) ;
  • Park, Jong-Keun (Electric Power System & Economics Lab., Seoul National University)
  • Published : 2007.06.01


This paper proposes a method for real-time control of both capacitors and ULTC in a distribution system to reduce the total power loss and to improve the voltage profile over the course of a day. The multi-stage consists of the off-line stage to determine dispatch schedule based on a load forecast and the on-line stage generates the time and control sequences at each sampling time. It is then determined whether one of the control actions in the control sequence is performed at the present sampling time. The proposed method is presented for a typical radial distribution system with a single ULTC and capacitors.


Capacitor;Load forecast;Real-time control;Under-load tap changer (ULTC)


  1. F. Lu and Y. Hsu, 'Reactive power/voltage control in a distributions substation using dynamic programming', IEE Proc. Gener. Transm. Distrib., vol. 142, no. 6, pp. 636-645, 1995
  2. R. Liang and C. Cheng, 'Dispatch of main transformer ULTC and capacitors in a distribution system', IEEE Trans. Power Deliv., vol. 16, no. 4, pp. 626-630, 2001
  3. Y. Liu and X. Qui, 'Optimal reactive power and voltage control for radial distribution system', Proc. IEEE PES Summer Meeting, vol. 1, pp. 85-90, 2000
  4. N. I. Santoso and O. T. Tan, 'Neural-net based realtime control of capacitors installed on distribution systems', IEEE Trans. Power Deliv., vol. 5, no. 1, pp. 266-272, 1990
  5. Y. Y. Hsu and C. C. Yang, 'A hybrid artificial neural network-dynamic programming approach for feeder capacitor scheduling', IEEE Trans. Power Syst., vol. 9, no. 2, pp. 1069-1075, 1994
  6. A. Saric, M. Calovic, and M. Djucanovic, 'Neuralnet based coordinated control of capacitors and ULTC transformer in daily operation of radial distribution systems', Elect. Power Syst. Res., vol. 43, pp. 169-177, 1997
  7. Z. Hu, X. Wang, H. Chen and G. Taylor, 'Volt/VAr control in distribution systems using a time-interval based approach', IEE Proc. Gener. Transm, Distrib., vol. 150, no. 5, pp. 548-554, 2003

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