US Patent 7138728 Anti-islanding techniques for distributed power generation

Techniques for detecting an island in a system including a node that is operatively coupled to a primary power source (e.g., grid) and one or more distributed power generation sources are disclosed. In one embodiment, a current pulse is included in the output of a distributed power source. The grid voltage is monitored at the node to determine if a pulse-related disturbance occurs. If the grid is present, no pulse-related disturbance will manifest. If grid is down, then a pulse-related disturbance will manifest. Detection of the pulse-related disturbance is used to signal island detection.