Soft Start-up Method for Grid-connected Grid-forming Converter

Inverter-based resources connected to the power system have increased rapidly in recent years. However, this trend weakens grid strength, which is maintained by the inertia of synchronous generators. Therefore, grid-forming converters have attracted much attention owing to their ability to maintain stable connections with weak grids compared with conventional grid-following converters. Various control methods have been proposed for configuring virtual synchronous generators to control grid-forming converters. However, the stable grid integration and initial operation for each of these methods require further research. In this paper, the start-up characteristics of grid-forming converters were examined. The proposed method implements a soft start-up method in a synchronous power control-based grid-forming converter. The validity of the proposed method was verified with 250 kW simulation and hardware-in-the-loop simulation.