An Investigation on Variational Mode Decomposition for Synchronization of Power Converters in Future Power Grids

A primary investigation on variational mode decomposition (VMD) technique extended as a grid synchronizer for power converters in emerging electric grids with nonlinear characteristics is presented. Number of modes and data-fidelity parameter of VMD are tailored to achieve finer separation of the fundamental frequency in spite of the spectral band variations and minor frequency deviations of the grid voltage signals. The test cases are formulated based on CIGRE and IEEE Task Force 1159.2 repository on the foreseen power quality issues in the emerging power utilities. Two statistical indices viz. absolute error in percentage and RMS error are chosen to assess the compliance of extracted fundamental frequency signals with the applied values at cycle as well as sample level. A significant reduction in the tracking time across all the test conditions has been observed in simulation when compared to the conventional grid synchronizers. Appreciable accuracy levels are obtained in tracking the required signal attributes of the input signals even with multiple power quality issues. The frequency decomposition approach of VMD synchronizer exhibited an immunity toward random transient events like voltage surges, zero crossing disorders, phase and frequency jump, etc. Further, the validation in hardware has been conducted with emulated grid signals that represented mulitple power quality issues and wide range of transient events, and the results are analyzed and compared with those of the simulation.