Islanding Detection Using a Coordinate Transformation Based Phase-Locked Loop

The acceptance rate at which distributed generation (DG) resources are being allowed to connect to the electric utility grid is rapidly increasing. To ensure the proper and safe usage of these resources, protection schemes known as islanding detection algorithms must be implemented to disconnect a DG from the grid such that they do not inadvertently feed a fault or other islanding events. This paper proposes a quasi-active islanding detection algorithm to minimize/eliminate non-detection zones (NDZs), as well as to further mitigate any perturbations needed to detect an islanding event. Simulations confirmed by experimental results show the feasibility and effectiveness of the scheme.