A Fault Detection Scheme for Islanded-Microgrid with Grid-Forming Inverters

This paper proposes a fault detection scheme for microgrids with grid-forming inverters. In this paper, a superimposed phase-current scheme with a voltage-restraint element is proposed which identifies the faults in an islanded microgrid with grid-forming inverters. In the proposed method, different factors including the implemented fault-ride-through strategy, the fault current limiting scheme, and the control structure of the grid-forming inverter are considered. Furthermore, the moving window concept is included, which considerably increases the detection speed. The severity and type of short circuit fault do not affect the functionality of the proposed method, and both symmetrical/asymmetrical short circuit faults are properly identified by the proposed scheme. Finally, the performance of the proposed scheme is demonstrated by applying different symmetrical/asymmetrical faults in a test system.