Distributed Synchronous generation ride-through enhancement by anti-islanding protection blocking

Abstract

Fault and other perturbations in the distribution or subtransmission system can change the system voltage and frequency, leading to improper operation of anti-islanding protections. This causes disconnections of distributed generations (DG) and, consequently, financial losses and degradation of Bulk Power System performance. This paper proposes a blocking scheme for an islanding detection function, based on impedance and rate of change of frequency. Several methods have been recently proposed for islanding detection in synchronous generators. However, commercial relays still use functions such as Rate of Change of Frequency. Even though it poses problems that are explored in this paper, it is consolidated and easy to implement. Thus, the proposed method is aimed at improving the performance of DG anti-islanding protection. The method has been tested through simulations using the IEEE 34 node test system. The results show that the proposed method is able to discriminate islanding from other transients, and it has operated properly in all non-islanding events, which include single-phase and three-phase short-circuits, load and capacitor switching, and outages of other DGs. Tolerance to transients allows the use of a small frequency threshold which ensures a small non-detection zone and faster disconnection in case of islanding.