ENHANCED FREQUENCY STABILITY IN AN INVERTER-DOMINATED MICROGRID USING VIRTUAL INERTIA TECHIQUE

Summary

This study investigates the enhancement of frequency stability in an inverter-dominated photovoltaic (PV) microgrid through the implementation of a Virtual Synchronous Generator (VSG)-based virtual inertia control strategy. The increasing penetration of inverter-based renewable energy sources has led to a significant reduction in system inertia, resulting in faster frequency deviations, higher rates of change of frequency (ROCOF), and reduced stability margins in modern power systems (Fang et al., 2022). These challenges are particularly critical in microgrids operating under weak-grid conditions with limited generation capacity. A model-based simulation approach was adopted to develop and analyse a 2 MW PV-dominated hybrid microgrid located at Nnamdi Azikiwe University, Awka. The system comprises a photovoltaic array, battery energy storage system (BESS), and diesel generator backup. A detailed dynamic model was implemented in MATLAB/Simulink, incorporating a VSG control framework designed to emulate both inertial and damping responses of conventional synchronous generators. The control strategy integrates virtual inertia, damping control, and state-of-charge (SOC)-based energy management within a unified structure. The performance of the proposed system was evaluated under step load disturbances of 2.2 MW, 2.5 MW, 2.8 MW, and 3.0 MW, and compared with a baseline system operating without virtual inertia support. Key performance indicators included frequency deviation, ROCOF, frequency nadir, and settling time. Simulation results demonstrate significant improvements in frequency stability with the implementation of VSG control. Specifically, ROCOF was reduced from −1.25 Hz/s to −0.093 Hz/s at 3.0 MW, while the effective system inertia increased from 0.2 s to approximately 2.7 s. The frequency deviation was also substantially minimised, with the system maintaining operation close to the nominal frequency across all test scenarios. The findings confirm that the proposed VSG-based virtual inertia control strategy effectively enhances the dynamic performance and stability of inverter-dominated microgrids. The relatively low energy requirement for transient support further demonstrates the practical feasibility of the approach. This study contributes to the development of reliable and sustainable microgrid operation, particularly in low-inertia and weak-grid environments typical of developing power systems.

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