Islanding Detection Using Combined Algorithm Based on Rate of Change of Reactive Power and Current THD Techniques

Recently, the penetration of Distributed Generation (DG) at medium and low voltages in utility networks is increasing in developed countries and takes special place for them worldwide. Due to the DGs advantages, increasing of DGs add some problems in the system. One problem that encountered with it when using with DGs, is an unwanted Islanding phenomenon. Islanding phenomenon of a grid-connected independent generator like a photovoltaic (PV) system occurs when a section of a utility system is disconnected from the main utility voltage source, but the independent generator continues to energize the utility lines in the isolated section. In this paper, a new technique in order to detecting islanding conditions has been present, and the proposed method based on rate of change of reactive power and total harmonic distortion, its performance is much more appropriate than that of previous techniques. The simulation results performed in MATLAB, clearly show improved operation of this method.