Distributed generation operation: Grid-connected vs. Islanded

There are reasons when it might be desirable to utilize one or more DG resources to continue to provide power to a facility or group of facilities when the utility is unavailable, such as during major storms. There is an increased demand for formation of microgrids having their own self-contained generation that can continue to operate as an island in the event of an interruption in the utility grid. Not all DG resources are up to the task of operating an islanded system. We discuss the characteristics of each type of DG resource, as well as the critical design considerations that must be addressed to produce reliable power in the absence of the utility grid.