Distributed generation (DG) units such as photovoltaic and wind farm have been increasingly used to address environmental problems, and increase capacity of the electric grid. A DG unit is often connected in parallel with a host grid and injects power to the utility system by means of a power electronics converter. Under normal conditions, both the DG unit and its local load operate in a grid-connected mode. When the DG unit and its local load are disconnected from the grid, an islanded system is created. High depth of penetration of DG units, the economical considerations, and the continuity...