Performance of Reactive Power Variation Using Positive Feedback for Detecting Unintentional Islanding Operation

摘要

This paper proposed reactive power variation (RPV)strategy using positive feedback (PF)to identify unintentional islanding condition of distributed generations (DGs)and cease the successive operation of them. The concept in this paper uses the relationship between the shift of point of common coupling (PCC)frequency and the injected reactive power after islanding occurrence. The structure of the proposed RPV method has a constant reactive power component and a certain reactive power term due to PF using the frequency deviation between the rated frequency and the measured frequency. When islanding occurs, PF increases continuously the positive or negative reactive power in order to deviate PCC frequency outside over/under threshold levels, where PF reduces significantly detection time. The proposed RPV strategy is verified in experiments through 1.7kW 3-level T-type inverter. Detection times of islanding are measured to 53ms and 150ms in over/under threshold levels, respectively.