A New Approach on Development of Power System Operational Flexibility Index by Combination of Generation Unit Flexibility Indices

Document Type : Research Article


1 Electrical engineering department, Amir kabir university, Tehran, Iran

2 Department of Electrical Engineering, Amirkabir University, Tehran, Iran

3 Amirkabir University of Technology


Power system flexibility is the ability of power system to cope with the uncertainty and variability of generation and load sides. This ability should be quantified and measured by a suitable index to show the level of system flexibility in different situations. Flexibility area index, proposed by the authors, is a suitable metric for power system flexibility evaluation, especially in the presence of renewable sources as large scale wind and solar farms. Similar to other system flexibility indices, this index is defined first for one generation unit and then, extended to the power system by combination of the unit indices. In this way, an accurate and meaningful combination routine should be established to reflect the effect of each unit flexibility index correctly in the combined system flexibility index. This paper proposes a suitable and justified method to combine the unit flexibility indices, achieving the system flexibility index. The performance of the proposed index is verified by the wind/load curtailment in economic load dispatch incorporated wind power. Achieving this purpose, the mentioned index is decomposed into two components, one for ramp up and maximum generation system capabilities (upper component) and another for ramp down and minimum generation system capabilities (lower component), each related to the load or wind curtailment respectively which is another contribution of this paper. Finally, by establishment of a correlation between upper/lower component and load/wind curtailment, a suitable validity evaluation for the proposed system flexibility index is performed, which is another contribution of this paper.


Main Subjects

[1] - Danish Energy Agency, Flexibility in the Power System, [Online],
Available: https:// ens.dk/ sites/ ens.dk/ files/ Globalcooperation/ flexibility_in_the_power_system_v23-lri. pdf , 2015.
[2] – A. Ulbig,G. Andersson, “Analyzing Operational Flexibility of Electric Power Systems”, Elsevier, International Journal of Electrical Power & Energy Systems November 2015
[3] - H. Berahmandpour, S. M. Kouhsari and H. Rastegar, "A New Flexibility Index in Real Time Operation Incorporating Wind Farms" 2019 27th Iranian Conference on Electrical Engineering (ICEE), Yazd, Iran, 2019, pp. 549-553, doi: 10.1109/IranianCEE.2019.8786492.
[4] – H. Berahmandpour, S. M. Kuhsari and H. Rastegar, "Development the Flexibility Metric Incorporating Wind Power in the Presence of Energy Storage," 2019 International Power System Conference (PSC), Tehran, Iran, 2019, pp. 548-556, doi: 10.1109/PSC49016.2019.9081515.
[5] - Makarov Y, Loutan C, Ma J, de Mello P. “Operational Impacts of Wind Generation on California Power Systems”, IEEE Trans Power System, 2009; 24(2):1039–50.
[6] - M. Juan, S. Vera, B. Régine, S. Kirschen Daniel, and F. Ochoa Luis, “Exploring the use of flexibility indices in low carbon power systems,” presented at the 2012 3rd IEEE PES Innovative Smart Grid Technologies Europe (ISGT Europe), Berlin, Germany, 2012.
[7] - B. Mohandes, M. S. E. Moursi, N. Hatziargyriou and S. E. Khatib, "A Review of Power System Flexibility with High Penetration of Renewables", IEEE Transactions on Power Systems, vol. 34, no. 4, pp. 3140-3155, July 2019, doi: 10.1109/TPWRS.2019.2897727.
[8] – “Flexitranstore: Special Session in the 21st International Symposium on High Voltage Engineering”, Editors: Bálint Németh, Lambros Ekonomou, Springer International Publishing, 2020, ISBN: 3030378179, 9783030378172
[9] - A. Akrami, M. Doostizadeh, and F. Aminifar, “Power system flexibility: an overview of emergence to evolution,” Journal of Modern Power Systems and Clean Energy, vol. 7, no. 5, pp. 987-1007, 2019.
[10] - J. Zhao, T. Zheng, and E. Litvinov, “A unified framework for defining and measuring flexibility in power system,” IEEE Transactions on Power Systems, vol. 31, no. 1, pp. 339-347, Jan. 2016.
[11] - G. Papaefthymiou, E. Haesen, and T. Sach, “Power system flexibility tracker: Indicators to track flexibility progress towards high-res systems,” Renewable Energy, vol. 127, pp. 1026-1035, 2018.
[12] - J. Kiviluoma, E. Rinne, and N. Helistö, “Comparison of flexibility options to improve the value of variable power generation,” International Journal of Sustainable Energy, vol. 37, no. 8, pp. 761-781, 2018.
[13] - V. Oree and S. Z. S. Hassen, “A composite metric for assessing flexibility available in conventional generators of power systems,” Appl. Energy, vol. 177, pp. 683–691, 2016.
[14] - T. Guo, Y. Gao, X. Zhou, Y. Li, and J. Liu, “Optimal scheduling of power system incorporating the flexibility of thermal units,” Energies, vol. 11, no. 9, 2195, 2018.
[15] - E. Lannoye, D. Flynn, and M. O'Malley, “Evaluation of power system flexibility,” IEEE Transactions on Power Systems, vol. 27, no. 2, pp. 922-931, 2012.
[16] - Islam Abdin, Enrico Zio. “Integrated framework for operational flexibility assessment in multi period power system planning with renewable energy production” Applied Energy, Elsevier, 2018, 222, pp.898-914.
[17] - J. Cochran, M. Miller, O. Zinaman, M. Milligan, D. Arent, B. Palmintier, M. O’Malley, S. Mueller, E. Lannoye, A. Tuohy, B. Kujala, M. Sommer, H. Holttinen, J. Kiviluoma, and S. K. Soonee, “Flexibility in 21st Century Power Systems,” 21st Century Power Partnership, [Online], Available: https://www.nrel.gov/docs/fy14osti/61721.pdf.
[18] - A. A. S. Shetaya, R. El-Azab, A. Amin, and O. H. Abdalla, “Flexibility measurement of power system generation for real-time applications using analytical hierarchy process,” presented at the IEEE Green Technologies Conference (GreenTech), Austin, TX, USA, 2018.
[19] - A. A. Thatte and L. Xie, “A metric and market construct of inter-temporal flexibility in time-coupled economic dispatch,” IEEE Transactions on Power Systems, vol. 31, no. 5, pp. 3437-3446, 2016.
[20] - C. G Min and M. K. Kim, “Flexibility-based evaluation of variable generation acceptability in Korean power system,” Energies, vol. 10, no. 6, 825, 2017.
[21] - C. G. Min, J. K. Park, D. Hur, and M. K. Kim, “A risk evaluation method for ramping capability shortage in power systems,” Energy, vol. 113, pp. 1316–1324, 2016.
[22] - C. G. Min, “Analyzing the impact of variability and uncertainty on power system flexibility”, Appl. Sci. vol. 9, no. 3, pp. 1-13, 2019.
[23] - Surekha P, “Investigation of Efficient Bio-Inspired Intelligent Paradigms for Solving Unique Constraint Based Optimization Problems”, A thesis submitted to the Faulty of Electrical Engineering ANNA University for the award of the degree of doctor of philosophy. Chennai (India) Auguest-2014,