Two-Stage Islanding Detection Method via High Frequency Impedance and Harmonic Distortion Evaluation in Multi-DG Networks

Islanding detection is essential for reliable and safe operation of systems with distributed generations (DG). In systems with multiple DGs, the interaction between DGs can make the islanding detection process more challenging. To address this concern, this paper proposes a two-stage islanding detection method for power systems equipped with multiple-DGs through estimation of high frequency impedance (Zf) and determination of the total harmonic distortion (THD). The impedances of the DGs are estimated at distinct frequencies to avoid interval overlaps. The concept of different frequency bands makes the proposed method applicable to multiple DG systems. To evaluate the effectiveness of the proposed method, a test system with multiple DGs is simulated through several case studies in PSCAD/EMTDC. The simulation results demonstrate the accuracy of the proposed islanding detection method in both single and multi-DG systems. It is also shown that the proposed method remains robust under different operating conditions and events.