Mode Of Oscillation Based Islanding Detection Of Inverter Interfaced Dg

Islanding detection of Inverter Interfaced Distributed Generators (IIDGs) is a major aspect of microgrid automation. Most islanding detection techniques, either active or passive, are developed based on threshold settings, and hence, have limited application. Detection of the mode of oscillation in frequency signal measured at the Point of Common Coupling (PCC) using the Estimation of Signal Parameter via Rotational Invariance Technique (ESPRIT) is presented in this paper for islanding detection of IIDGs. A low-frequency current injection disturbance is injected in the conventional dq controller of the IIDG. The frequency deviation is estimated using ESPRIT for signal parameter estimation. The Total Harmonic Distortion (THD) due to the low-frequency disturbance injection is also evaluated for both d axis and q axis. The proposed method is tested in Real-Time Digital Simulator (RTDS) on a test system with multiple DGs, and an unbalanced microgrid, at various operating conditions, such as, different quality factors of loads, random loading, faults, and switching transients in the microgrid. The simulation results indicate that the proposed method for islanding detection of IIDGs completely eliminates the Non-Detection Zone (NDZ), with negligible impact on Power Quality (PQ), and is independent of any threshold settings.