anti-Islanding Detection The islanding phenomenon for gridconnected PV systems occurs when the PV inverter does not disconnect
after the grid has tripped and continues to provide power to the local load [10]. In the conventional case of a residential electrical system cosupplied by a rooftop PV system, the grid disconnection can appear as a result of a local equipment failure detected by the ground fault protection or of an intentional disconnection of the line for servicing. In both situations, if the PV inverter does not disconnect, some hazardous situations can occur, such as ■ retripping the line with an out-ofphase closure, damaging some equipment ■ a safety hazard for utility line workers who assume that the lines are de-energized. To avoid these serious situations, safety measures and detection methods called anti-islanding requirements have been required in standards. In IEEE 1574, it is defined that after an unintentional islanding where the PV system continues to energize a portion of the power system (island) through the point of common coupling, the PV system shall detect the islanding and stop to energize the area within 2 s [11].