New islanding detection method with adaptively threshold for microgrid

摘要

This paper proposes a new passive method with adaptively threshold to address islanding problem of microgrid. The recommended system for islanding analysis is introduced first, and then the rate of change of power factor angle is exploited as the islanding detection index. Under grid-connect state, detection index is higher for nonislanding event. But during islanding operation, detection index approaches zero. Therefore, the introduced detection index can be better distinguish islanding and non-islanding events. Finally, a new passive method considering the voltage/frequency behavior of load is proposed, and the adaptively threshold is given by analyzing the relationship between reactive power and the resonant frequency of load after islanding occurrence. The proposed method is compared with other passive methods against various scenarios of the single and multiple DG systems. Simulation and experiment results demonstrate that the passive method with adaptively threshold has high reliability against islanding and non-islanding events.