System Rigidity: A Comprehensive Approach to Enhancing Power System Stability
I. Vokony Department of Electric Power Engineering, Budapest University of Technology and Economics, Budapest, (Hungary)   2026-06-27

Abstract

The shift toward renewable-dominated power systems has significantly reduced inertia, challenging traditional stability metrics. This paper introduces system rigidity as a unified measure capturing frequency, voltage, and angle stability in low-inertia grids. A Rigidity Response Threshold (RRT) is defined as the maximum disturbance a system can endure without instability, derived using a Lyapunov-based framework. Validation through field tests on the Fót microgrid – including pump motor switching and PV disconnection – confirms that system rigidity aligns with known stability boundaries and outperforms inertia- or RoCoF-based indicators in sensitivity. The proposed rigidity metric and RRT offer operators a holistic tool to assess and enhance stability, supporting the deployment of synthetic inertia, fast frequency response, and advanced control strategies for future resilient power systems.

Key words: frequency stability, low-inertia systems, renewable energy integration, synthetic inertia, system rigidity

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