A combined active anti-islanding method for photovoltaic systems

In a modern power system, photovoltaic as distributed generated source is growing larger and it can cause a variety of problems. The most important problem is that of the islanding phenomenon. In order to prevent islanding phenomenon, three kinds of active islanding detection methods have been studied. These are, respectively, to change magnitude, frequency, and the start phase of inverter output current. Among those, both a frequency variation method and a start-phase variation anti-islanding method make the islanding frequency drift away from the trip window of the frequency relay if islanding occurs. This paper presents a novel combined active anti-islanding method, which consists of a frequency variation method active frequency drift (AFD) and a start-phase variation method slip-mode frequency shift (SMS). Clearly, the proposed anti-islanding method shows the islanding detection ability to IEEE 1547 Standard. To validate the performance of the proposed method, simulations and experiments were performed. Possible islanding conditions are implemented with a unity quality factor by the IEEE Standard 1547. The methodology presented can be extended to the other active anti-islanding methods. (c) 2007 Elsevier Ltd. All rights reserved.