Anti-Islanding Protection Method for Ratio Measurement by Voltage Signal Synchronization

Anti-islanding protection based on impedance measurement can effectively avoid the problems of refusal and maloperation. But existing methods fail to establish a unified identification criterion in different islanding systems, and the mutual interference of the detection signals in the multi-DG system will lead to the protection failure. In this regard, a new islanding identification method is constructed by utilizing the ratio of the islanding detection signal to the grid voltage, which frees the criterion setting from the dependence on the system impedance parameter. In addition, the self-synchronization strategy proposed in this method allows each DG to synchronize the injected signals spontaneously by using the islanding detection signal and the voltage crossing point. Finally, simulation experiments based on a real-time digital simulation system (RTDS) verify the feasibility and effectiveness of the present methods.