A Centralized Injection Method for Islanding Detection in Micro-Grids

A desired islanding detection method applied in microgrid not only can detect islanding correctly within acceptable duration as same as that in distributed generation system, but also ensures the smooth transition from grid-connected mode to islanded mode. In the paper an islanding detection method is presented, which considers the characteristics of system equivalent impedance that varies with the microgrid connecting main grid or not, with the help of the negative current injection into the point of common coupling (PCC), and then identifies the negative voltage variations near PCC. The method is able to avoid the negative impact on the operation stability of the microgrid. Through the Matlab/Simulink simulation, the rapidity and affectivity of these principles are verified.