Grid connected converters with enhanced low-voltage ride through capability

One of the main protection issues is the possible malfunctioning of protection devices under fault conditions in microgrids with integrated distributed energy resources (DERs). In this paper, a novel method of positive-negative sequence (PNS) compensation for grid connected distributed generator (DG) converters with enhanced low voltage ride-through (LVRT) capability in micro grid system is presented. The aim is to maintain the connection of the DGs by injecting the required reactive power considering the limitations imposed by grid codes. In the proposed scheme, a flexibility is provided in terms of active and reactive current injection such that the DGs can stay connected to the grid longer and produce more active power during the fault; while, in previous studies, usually a constant reactive current defined by grid codes was applied. The suitability of the proposed method in terms of utilization of current capacity of the converter is evaluated through comparative study with three other PNS current injection methods. Further, the time taken to disconnect the DGs from the grid in the event of fault is analyzed. The simulation results indicate that DGs can stay connected for longer with 99.98% utilization of converter current capacity compared to other methods.