Based on hybrid algorithm of micro-grid islanding detection

Micro-grids are being developed as a building block for future smart grid system. Islanding detection is a great challenge in connecting distributed generation (DG) in electrical power systems. Islanding detection methods are categorized into three groups, i.e., communication based methods, active, and passive methods. Communication based methods are established upon communication between utilities and DGs and have the inconvenience of being expensive and are limited in use. Active methods perturb the system with a disturbance and the system response to the disturbance is analyzed. This paper proposes a hybrid islanding detection method which uses voltage unbalance (VU) and high-frequency (HF) impedance. The proposed method merges the advantages of both active and passive techniques. In addition, since the active method used in this paper does not change any of the system variables as a disturbance, it will not lead to any instability.