Computational Implementation of Different Anti-Islanding Techniques Based on Frequency Drift for Distributed Generation Systems

Abstract

Islanding is a subject of great concern in the Distributed Generation literature since it can lead to equipment losses and electrical accidents for the line workers during a maintenance procedure. The anti-islanding strategies are divided in two big groups: passive and active. The passive strategies preserve the power quality, nevertheless, they present a wide Non-Detection Zone (NDZ). Active methods, in its turn, reduces the NDZ by injecting small degradations into the inverter output parameters. This paper approaches a computational implementation of three different strategies of active anti-islanding based on frequency shift. These methods present reduced NDZ, which is one of the key parameters for measuring their effectiveness. Therefore, is presented the methodology for NDZ determination and THD of the current injected into the grid. For corroborating the presented theory, a PV system of 900Wp was connected to the grid through a VSI inverter, being possible to determine the time required for each method for detecting the islanding.