An anti-islanding protection scheme for grid-connected distributed power generation systems

This paper presents an active islanding detection method for grid-connected distributed power generation systems. The proposed scheme is based on an invasive current injection. An impedance estimation module in the frequency domain is introduced to estimate the equivalent impedance seen from the point of common coupling. To do so, a fast and accurate adaptive notch filter is used to extract the ambient components of the voltages and the currents. The accuracy of the proposed technique and its ability to detect islanding events even for purely resistive and nearly resonant loads are verified in this paper.