Island Detection Based on Improved Sandia Frequency-Shift Method

To reduce the disturbance to the power quality that the traditional active island detecting causes, this paper present a new method to detect islanding which is based on Sandia frequency-shift method, and then simulate the method combining with passive island detecting in RTDS. The method is based on frequency positive feedback to reactive current to increase reference value of reactive current. And then design appropriate filter to keep the system steady. The increase of the reactive current reference value causes more reactive power which will make the system frequency larger and fasten the system reaching the protecting limit and then leave the grid. This method only disturbs reactive current which will improve power quality.