Towards a novel framework for power system stability: introducing system rigidity
I. Vokony, I. Taczi, B. Hartmann Department of Electric Power Engineering. Budapest University of Technology and Economics. Egry Jozsef 18. Budapest - Hungary 2025-07-25

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.

Key words: Power system stability; low-inertia grids; synthetic inertia; system rigidity; renewable energy integration

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