Analysis of modified ROCOF relays for islanding detection of distribution systems with DFIG

Wind power has evolved as a primary source of sustainable energy for bulk generation as well as small scale units. Power distribution systems with wind generation units like Doubly Fed Induction Generator (DFIG) are bound by the standards like IEEE 1547 to detect formation of power islands and disconnect the DFIG from the system. This approach is not an economically viable option as the DFIG system with appropriate control may successfully continue to supply power to the local loads and hence operate as an islanded Microgrid. However, this decreases the time frame within which islanding detection relays (IDR) must operate. This paper presents a comparative study of advanced techniques based on the principle of a classic Rate of Change of Frequency (ROCOF) relay that has been proposed in recent research works for utilization in distribution systems with DFIG. This work evaluates these IDRs in terms of their operating characteristics. Simulations have been carried out in PSCAD to obtain the operating curves and to assess the vulnerability of these IDRs to non-islanding transient. The effect of these techniques on power quality is also highlighted.