Islanding Detection Methods Based on Self-oscillation of Particular Frequency in DC Distribution Systems

Detecting the DC-based island is essential for safe operation of DC distribution system. State-of-the-art of islanding detection methods in DC systems mainly utilize the positive feedback principle to shift the voltage amplitude out of the normal range and then trigger over/under voltage protection. However, this has the negative consequences of deteriorating of power quality and causing blackouts in the islanding event. This paper proposes the methods of oscillation of particular frequency as an indicator to detect islanding conditions quickly with less deterioration of power quality and no blackouts. Firstly, the paper establishes the model of the DC distribution system for the purpose of analyzing DC-based islanding mechanism. This paper then introduces two islanding-detection methods that implement the voltage oscillation at particular frequency as an indication of islanding conditions. Finally, the proposed methods are validated through time-domain nonlinear simulations and experimental results from a laboratory-scale DC distribution system.