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arXiv · 2505.21461

Quasi Steady-State Frequency

Joan Gutierrez-Florensa·Alvaro Ortega·Lukas Sigrist·Federico Milano
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Abstract

Accurate frequency estimation is critical for the control, monitoring and protection of electrical power systems, in particular, of systems with a high penetration of power electronics. This paper introduces the novel concept of Quasi Steady-State (QSS) frequency as a quantity that fills the gap between stationary and instantaneous frequency. QSS frequency coincides with the fundamental frequency of an AC voltage in any stationary conditions, including unbalanced and non-sinusoidal, and is able to capture the time-varying fundamental frequency in transient conditions. The paper also proposes a metric borrowed from fluid dynamics, namely, the time derivative of the circulation, to define the scope of validity of the QSS frequency. Analytical examples as well as a case study based on a fully-fledged EMT model of the IEEE 39-bus system serve to illustrate, respectively, the properties of the QSS frequency and its behavior in transient conditions.

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BibTeXRIS

Joan Gutierrez-Florensa, Alvaro Ortega, Lukas Sigrist, Federico Milano. 2025-09-22. Quasi Steady-State Frequency. https://arxiv.org/abs/2505.21461

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