Coordinated under frequency load and capacitor shedding for bulk power systems

Coordinated under frequency load and capacitor shedding for bulk power systems

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Under frequency load shedding (UFLS) scheme has been widely implemented as a safety net to prevent system collapse following major disturbances which results in large mismatch between load and generation. However, voltage related issues post activation of UFLS stages are also vital concerns in preserving system stability and should be properly analysed. Fixed and switched shunt capacitors that are in service during normal operation for maintaining system voltage and dynamic MVAR reserve can generate surplus reactive power post operation of UFLS relays which may result in over voltage issues, generator under excitation and some undesirable conditions such as transformer saturation, ferro-resonance etc. This study addresses the need for coordinated under frequency load and capacitor shedding and its implementation approach to effectively preserve system stability following small and large disturbances. To confirm the feasibility of the approach, the proposed method has been used to design coordinated UFLS and under frequency capacitor shedding (UFCS) schemes for a real and actual power network. In addition, the proposed coordinated UFLS and UFCS scheme has been combined with automatic switching of shunt reactors to optimise the performance of the scheme.


    1. 1)
      • 1. Hong, Y.-Y., Wei, S.-F.: ‘Multi objective under frequency load shedding in an autonomous system using hierarchical genetic algorithm’, IEEE Trans. Power Deliv., 2010, 25, (3), pp. 13551362 (doi: 10.1109/TPWRD.2010.2046679).
    2. 2)
      • 2. Sigrist, L., Egido, I., Rouco, L.: ‘Performance analysis of UFLS schemes of small isolated power systems’, IEEE Trans. Power Syst., 2012, 99, pp. 16731680 (doi: 10.1109/TPWRS.2011.2182066).
    3. 3)
      • 3. Ahsan, M.Q., Chowdhury, A.H., Ahmed, S.S., Bhuyan, I.H., Haque, M.A., Rahman, H.: ‘Technique to develop auto load shedding and islanding scheme to prevent power system blackout’, IEEE Trans. Power Syst., 2012, 27, (1), pp. 198205 (doi: 10.1109/TPWRS.2011.2158594).
    4. 4)
      • 4. Hong, Y.-Y., Chen, P.-H.: ‘Genetic-based underfrequency load shedding in a stand-alone power system considering fuzzy loads’, IEEE Trans. Power Deliv., 2012, 27, (1), pp. 8795 (doi: 10.1109/TPWRD.2011.2170860).
    5. 5)
      • 5. Ghaleh, A.P., Sanaye-Pasand, M., Saffarian, A.: ‘Power system stability enhancement using a new combinational load-shedding algorithm’, IET Gener. Transm. Distrib., 2011, 5, (5), pp. 551560 (doi: 10.1049/iet-gtd.2010.0626).
    6. 6)
      • 6. Seethalekshmi, K., Singh, S.N., Srivastava, S.C.: ‘A synchrophasor assisted frequency and voltage stability based load shedding scheme for self-healing of power system’, IEEE Trans. Smart Grid, 2011, 2, (2), pp. 221230 (doi: 10.1109/TSG.2011.2113361).
    7. 7)
      • 7. Rudez, U., Mihalic, R.: ‘Monitoring the first frequency derivative to improve adaptive underfrequency load-shedding schemes’, IEEE Trans. Power Syst., 2011, 26, (2), pp. 839846 (doi: 10.1109/TPWRS.2010.2059715).
    8. 8)
      • 8. Rudez, U., Mihalic, R.: ‘Analysis of underfrequency load shedding using a frequency gradient’, IEEE Trans. Power Deliv., 2011, 26, (2), pp. 565575 (doi: 10.1109/TPWRD.2009.2036356).
    9. 9)
      • 9. Saffarian, A., Sanaye-Pasand, M.: ‘Enhancement of power system stability using adaptive combinational load shedding methods’, IEEE Trans. Power Syst., 2011, 26, (3), pp. 10101020 (doi: 10.1109/TPWRS.2010.2078525).
    10. 10)
      • 10. Sigrist, L., Egido, I., Sanchez-Ubeda, E.F., Rouco, L.: ‘Representative operating and contingency scenarios for the design of UFLS schemes’, IEEE Trans. Power Syst., 2010, 25, (2), pp. 906913 (doi: 10.1109/TPWRS.2009.2031839).
    11. 11)
      • 11. Mahat, P., Chen, Z., Bak-Jensen, B.: ‘Underfrequency load shedding for an islanded distribution system with distributed generators’, IEEE Trans. Power Deliv., 2010, 25, (2), pp. 911918 (doi: 10.1109/TPWRD.2009.2032327).
    12. 12)
      • 12. Hong, Y.-Y., Wei, S.-F.: ‘Multiobjective underfrequency load shedding in an autonomous system using hierarchical genetic algorithms’, IEEE Trans. Power Deliv., 2010, 25, (3), pp. 13551362 (doi: 10.1109/TPWRD.2010.2046679).
    13. 13)
      • 13. Seyedi, H., Sanaye-Pasand, M.: ‘New centralised adaptive load-shedding algorithms to mitigate power system blackouts’, IET Gener. Transm. Distrib., 2010, 3, (1), pp. 99114 (doi: 10.1049/iet-gtd:20080210).
    14. 14)
      • 14. Mingchui, D., Chinwang, L., Chikong, W.: ‘Adaptive under-frequency load shedding’, Tsinghua Sci. Technol., 2008, 13, (6), pp. 823828 (doi: 10.1016/S1007-0214(08)72207-7).
    15. 15)
      • 15. Miller, T.J.E.: ‘Reactive power control in electric system’, 1982.
    16. 16)
      • 16. PSS/E™ 32.0 User Manual, March 2009.
    17. 17)
      • 17. Kulkarni, A.V., Gao, W., Ning, J.: ‘Study of power system load shedding scheme based on dynamic simulation’. IEEE PES Transmission and Distribution Conf. and Exposition, 2010, pp. 17.
    18. 18)
      • 18. Lu, Y., Kao, W.-S., Chen, Y.-T.: ‘Study of applying load shedding scheme with dynamic D-factor values of various dynamic load models to Taiwan power system’, IEEE Trans. Power Syst., 2005, 20, (4), pp. 19761984 (doi: 10.1109/TPWRS.2005.856988).
    19. 19)
      • 19. Aik, D.L.H.: ‘A general-order system frequency response model incorporating load shedding: analytic modeling and applications’, IEEE Trans. Power Syst., 2006, 21, (4), pp. 709717 (doi: 10.1109/TPWRS.2006.873123).
    20. 20)
      • 20. Tan, W., Shen, C., Zhang, X., Ni, J.: ‘A new under-frequency load shedding scheme based on OBDD’. IEEE Int. Conf. on Sustainable Power Generation and Supply, 2009.
    21. 21)
      • 21. Omar, Y.R., Abidin, I.Z., Yusof, S., Hashim, H., Rashid, H.A.A.: ‘Under frequency load shedding (UFLS): principles and implementation’. IEEE Int. Conf. Power and Energy (PECon), 2010.
    22. 22)
      • 22. Jiang, H., Yan, G., Ji, H., Liu, L., Shan, D.: ‘An improved under frequency load shedding scheme based on rate of change of frequency’. Int. Conf. on Electrical and Control Engineering (ICECE), 2010.
    23. 23)
      • 23. Xiong, X., Li, W.: ‘A new under-frequency load shedding scheme considering load frequency characteristics’. IEEE Int. Conf. on Power System Technology, 2006 (PowerCon), 2006.
    24. 24)
      • 24. El Azab, R.M., Eldin, E.H.S., Lataire, P., Sallam, M.M.: ‘Optimal location of shedding load at the adaptive UFLS’. IEEE Int. Energy Conf. and Exhibition (EnergyCon), 2010.
    25. 25)
      • 25. Shan, X., Zhe, T.: ‘A load shedding method based on the power vacancy sensitivity analysis’. CICED, 2010.
    26. 26)
      • 26. Bevrani, H., Ledwich, G., Ford, J.J.: ‘On the use of df/dt in power system emergency control’. IEEE/PES Power Systems Conf. and Exposition, 2009.
    27. 27)
      • 27. Moh Zin, A.A., Mohd Hafiz, H., Womg, W.K.: ‘Static and dynamic under frequency load shedding’. POWERCON 2004, 2004, pp. 941945.
    28. 28)
      • 28. Thalassinakis, E.J., Dialynas, E.N.: ‘A Monte-Carlo simulation method for setting the underfrequency load shedding relays and selecting the spinning reserve policy in autonomous power systems’, IEEE Trans. Power Syst., 2004, 19, (4), pp. 13551362 (doi: 10.1109/TPWRS.2004.835674).
    29. 29)
      • 29. Terzija, V.V.: ‘Adaptive underfrequency load shedding based on the magnitude of the disturbance estimation’, IEEE Trans. Power Syst., 2006, 21, (3), pp. 12601266 (doi: 10.1109/TPWRS.2006.879315).
    30. 30)
      • 30. You, H., Vittal, V., Yang, Z.: ‘Self-healing in power systems: an approach using islanding and rate of frequency decline based load shedding’, IEEE Trans. Power Syst., 2003, 18, pp. 174181 (doi: 10.1109/TPWRS.2002.807111).

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