A Novel Active Islanding Detection Method Based on Real-Time Wavelet Analysis in DC Microgrids

Abstract

This thesis presents a novel real-time active scheme for fast and reliable identifcation of islanding events in DC microgrids (MGs). The scheme is applicable in scenarios with or without power exchange between the main DC grid and MGs. In this approach, the bidirectional Dual Active Bridge (DAB) DC-DC converter’s controller injects a distinct single-tone periodic perturbation signal at predetermined intervals. The discrete nature of the perturbation signal considerably reduces its impact on power quality. A real-time wavelet analyzer determines whether to maintain or disconnect connections based on critical parameters it receives from decentralized detectors. The proposed method disconnects the main grid and common DC bus through converters in case of islanding events eliminating the need for complex DC circuit breakers (CBs). Detailed mathematical stability analysis proves and demonstrates that the proposed method, unlike some other active methods, guarantees the system’s stability. This analysis aligns seamlessly with the IEEE 1547 Standard and is validated by extensive simulation results.