Islanding of grid-connected AC module inverters

A major safety issue about grid-connected photovoltaics is to avoid non-intentional operation in islanding mode, the grid being tripped. This paper presents detailed measurements on the islanding behavior of four module inverters with a maximum rated power of 200 W. Although applying active anti-islanding measures each inverter could be forced into islanding. It could be observed experimentally what recently has been shown analytically, that some methods against islanding fail if inverters are loaded with considerable parallel capacitance. As most distribution grids contain a considerable capacitance, those methods are to be improved. One of the inverters failed totally what illustrates the need for standardized type approvals. The outcomes show where to put accents in the development and implementation of efficient protection algorithms.