Towards a novel framework for power system stability: introducing system rigidity

Vokony, István and Taczi, Istvan and Hartmann, Bálint (2025) Towards a novel framework for power system stability: introducing system rigidity. E&Q JOURNAL, 3. pp. 56-61. ISSN 2659-8779

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Abstract

The transition from centralized synchronous generation to distributed renewable resources has introduced significant challenges for power system stability. Conventional stability metrics and methods, rooted in high-inertia systems, struggle to address the fast dynamics and control complexity of low-inertia grids. This paper proposes system rigidity as a new holistic stability metric, defined as the capacity of a power system to resist destabilizing forces (e.g. frequency fluctuations, voltage deviations, phase angle disturbances) within acceptable limits under varying conditions. We develop a theoretical framework for system rigidity, including a Rigidity Response Threshold (RRT) that quantifies the maximum disturbance a system can withstand without losing stability. The novelty of this approach lies in unifying transient, frequency, and voltage stability considerations into a single metric and extending classical Lyapunov-based stability analysis to modern low-inertia systems. The concept is supported by enhanced simulation techniques (combining electromechanical and electromagnetic transient analysis) and experimental validation on a microgrid test site. Main results demonstrate that system rigidity correlates with known stability margins and provides a more sensitive indicator for low-inertia scenarios than traditional inertia-based metrics. The experimental plans at the Fót test site will further validate these findings under real-world conditions. Conclusions: The introduction of system rigidity offers system operators a new tool to evaluate and enhance stability in renewable-dominated grids, guiding the integration of synthetic inertia, fast frequency response, and advanced control strategies to ensure reliable and resilient future power systems.

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