Islanding phenomenon of grid connected PV systems

Appropriate islanding prevention measures are a must for grid connected PV systems. A great variety of methods are used to prevent islanding of grid connected PV systems. Detecting native islanding characteristics in the power grid then dealing with the phenomenon is the passive method. Constantly adding some light disturbance to the grid and detecting their obvious effects during islanding is the active method. Also combinations of these methods have appeared. Any of them is effective to some extent, but none of them could be described as perfect. Based on numerous tests conducted at the Rokko Demonstrative Test Center, after shedding light on the substance of islanding, the causes of that imperfection were investigated.