Modeling and analysis of passive networks using dynamic phasors for study of islanded inverters

Grid integration of renewable energy based distributed energy resources (DERs) through pulse-width modulated (PWM) grid-tie inverters (GTI), is gaining importance owing to ever-increasing energy demand. Study of islanding behavior of such GTIs is critical for detecting island formation and for subsequently ceasing DER operation. The grid-interface structure of a GTI considered for islanding study typically consists of a parallel RLC network forming the load bank, along with grid and grid-impedance. Existing models for analysis of grid-interface are based on time-domain differential equations and are less insightful for analytical study of the ac phenomena occurring during and after island formation. In this paper, a dynamic-phasor based approach is investigated for modeling and analysis of grid-interface passive network system of a DER. A generic and simplified framework is proposed for developing polar coordinates based dynamic phasor models of passive networks, which are verified through simulation and experiments.