Damping of Torsional Vibrations in a Type-IV Wind Turbine Interfaced to a Grid-Forming Converter

This paper introduces a Type-IV wind turbine interfaced to a grid-forming converter. In order to retain the stable operation of a wind turbine in the presence of a grid-forming control, the classical control of a back-to-back converter has to be modified. The modification of this control creates a strong link between a wind turbine and grid dynamics. From the grid side perspective, this link allows provision of the inertial response from a wind turbine during transient events. On the wind turbine side, this coupling causes the appearance of the torsional vibrations within the drivetrain structure. These vibrations are then propagated to the grid as power oscillations. As a result, there is a negative impact on the mechanical components of a wind turbine as well as on the power system operation. In this work, a solution is introduced in order to suppress the undesired vibrations by applying a damping technique to the control of a back-to-back converter combined with a grid-forming control. Based on the conducted analysis, the addition of a damping filter results in the mitigation of torsional vibrations.