Underfrequency Load Shedding using Locally Estimated RoCoF of the Center of Inertia

Mingyu Sun, Gaoyuan Liu, Marjan Popov, Vladimir Terzija, Sadegh Azizi

Research output: Contribution to journalArticleScientificpeer-review

33 Citations (Scopus)
45 Downloads (Pure)


The conventional Under Frequency Load Shedding (UFLS) scheme could result in unacceptably low frequency nadirs or overshedding in power systems with volatile inertia. This paper proposes a novel UFLS scheme for modern power systems whose inertia may vary in a wide range due to high penetration of renewable energy sources (RESs). The proposed scheme estimates the rate of change of frequency (RoCoF) of the center of inertia (CoI), and consequently, the loss of generation (LoG) size, using local frequency measurements only. An innovative inflection point detector technique is presented to remove the effect of local frequency oscillations. This enables fast and accurate LoG size calculation, thereby more effective load shedding. The proposed UFLS scheme also accounts for the effect of the inertia change resulting from LoG events. The performance of the proposed scheme is validated by conducting extensive dynamic simulations on the IEEE 39-bus test system using Real Time Digital Simulator (RTDS). Simulation results confirm that the proposed UFLS scheme outperforms the conventional UFLS scheme in terms of both arresting frequency deviations and the amount of load shed.
Original languageEnglish
Article number9362316
Pages (from-to)4212-4222
Number of pages11
JournalIEEE Transactions on Power Systems
Issue number5
Publication statusPublished - 2021

Bibliographical note

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care
Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.


  • Center of inertia (CoI)
  • Rate of change of frequency (RoCoF)
  • Underfrequency load shedding (UFLS)


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