Hybrid Anti-Islanding Protection for Grid-Connected Inverter-Based Residential Microgrid

Abstract

This paper proposed an enhanced hybrid active anti-islanding protection technique for inverter-based microgrid (IBMG) to improve the protection and reliability of the microgrid operations. The proposed method combines passive and active detection techniques, namely voltage and frequency protections (OVP/UVP and OFP/UFP) and slip mode frequency shift (SMS). The passive protection method would serve as basic protection for the microgrid. Indeed, the IBMG stops injecting power to the grid as soon as the frequency or voltage amplitude at the PCC exceeds the prescribed thresholds. The active scheme is based on perturb and observe concept. Injection of disturbance locally to the IBMG P-Q dynamics-based phase-locked loop (PLL) synchronization allows protecting the microgrid from power mismatch during islanding. The applied SMS technique utilizes a positive feedback control to change the current–voltage phase angle and frequency at point of common coupling (PCC), monitoring frequency deviation to detect islanding. The proposed method performance was tested under MATLAB/Simulink software environment for different loading conditions and especially for load matching IBMG’s power condition. The method’s advantages regarding the time response was confirmed, and the effects on power quality degradation were proved to be negligible.