Modeling, analysis, and improvement of anti-islanding relays for a radial distribution system embedding DFIG-DG wind turbines

This paper presents modeling and analysis of four passive relays used in distributed generation passive anti-islanding protection schemes. The passive Overcurrent (OC), OV/UV, OF/UF, and ROCOF (Rate of Change of Frequency) relays are commonly used for DG anti-islanding protection because of their low cost and relative simplicity. The relays modeling are based on the commercial digital relays hardware and considering Discrete Fourier Transform (DFT) as the phasor and frequency estimation algorithms in MATLAB environment. Then, the relay models are simulated on a practical radial distribution system embedding six-1.67 MW Doubly-Fed Induction Generators (DFIG) using PSCAD/EMTDC. The obtained results and analysis are reported and discussed. Finally, an intelligent scheme is suggested which takes advantage of an islanding-dedicated complementary system and improves the security of conventional ORed system of four relays.