Assessment and Performance Comparison of Positive Feedback Islanding Detection Methods in DC Distribution Systems

Due to the high penetration level of dc-based distributed generators (DGs) and dc loads, dc distribution systems are gaining widespread acceptance in modern power grids. Therefore, dc distribution systems are expected to operate parallel to the existing ac ones. However, the techniques of islanding detection in dc grids have not been fully studied in the current literature. This paper presents a detailed analysis, performance comparison, and design guidelines of four different positive feedback islanding detection methods in dc distribution systems. In each method, the range of control parameters that guarantee system stability is analytically obtained. The effects of system parameters, such as the dc system resistance and inductance, DG filter capacitance, and local load resistance, on each islanding detection method, are thoroughly addressed. Furthermore, the interactions between DGs connected at different locations of the distribution feeder and equipped with positive feedback islanding detection methods are studied and characterized. Detailed time-domain nonlinear simulations and experimental results validate the analytical results.