Passive islanding detection method based on virtual PCC voltage phase-shift in microgrid

This paper presents a fast passive islanding detection method based on virtual phase-shift between the real voltage seen at the point of common coupling and its created image in a Microgrid. The proposed algorithm consists of extracting the positive and negative sequences of the voltage at this point using a second order generalized integrator in two-way; to synchronize properly the system with the utility grid and to differentiate the islanding condition from other grid disturbance. Then, calculate the phase-shift between the real positive voltage and its image. In one way, once a grid fault occurs, hence leading to additional grid fault impedance emerging, the phase-shift varies. According to this variation duration and level, Microgrid can take the decision of disconnecting from the utility grid to operate autonomously or staying in connected-mode. In the other way, under unintentional islanding condition Microgrid can detect the phase-shift occurrence even in non-detection zone. A simple and efficient phase-shift calculator is proposed. Theoretical analysis, simulation and experimental results are presented to validate the proposed method.