A Stability Assessment Framework for Standalone Hybrid Renewable Energy Systems Under High Renewable Penetration

Abstract

High penetration of renewable energy sources in standalone power systems provides a sustainable pathway for supplying electricity to remote and underserved communities, but it also introduces technical challenges associated with voltage and frequency stability. The variability of renewable generation and the reduction in system inertia can cause significant voltage deviations and frequency fluctuations if not properly managed. This paper presents a comprehensive voltage–frequency stability assessment framework for standalone hybrid renewable energy systems operating under high renewable energy penetration, using Ikere community in Iseyin, Oyo State, Nigeria. The framework integrates dynamic voltage deviation indices and frequency response metrics optimized using the Energy Valley Optimizer (EVO) to evaluate system robustness and identify stability-constrained operating limits. A stability constrained renewable penetration threshold of approximately 85% is identified, beyond which voltage and frequency deviations become increasingly pronounced. The proposed framework provides a practical and transferable tool for assessing stability limits in inverter-dominated standalone hybrid systems and offers valuable guidance for the planning, design, and operation of reliable off-grid power systems.