An improved differential protection scheme for micro-grid using time-frequency transform

This study presents an improved threshold-based differential protection scheme for micro-grids using time-frequency transform. Variational mode decomposition (VMD) in combination with Hilbert transform is used as the time-frequency transform. The improvements like insensitivity to noise and no modal aliasing effect makes VMD better over wavelet transform and empirical mode decomposition for fault studies. This protection scheme is applied to the currents retrieved at the two ends of the feeder to compute the differential energy for the micro-grid protection in grid connected and islanded modes. The proposed scheme is verified on a standard IEC microgrid test system operating in different configurations for various events like shunt faults, high impedance fault, and switching events. In addition, it is also validated using the real-time signals obtained through OPAL-RT as a real-time simulator. Comparative results validate that the proposed scheme performs accurately providing improved results than the state-of-the-art differential protection schemes.