Continuous grid frequency support with variable synthetic inertia and feedforward pitch angle adjustment

Abstract

Abstract Grid frequency support by wind turbines is increasingly demanded by grid operators around the globe. By meeting these requirements, the wind turbines leave their optimal operating point and may even be pushed out of their safe operating range during severe grid events. In the past years, the Wind Energy Technology Institute developed a controller for grid frequency support in collaboration with Suzlon Energy. This work seeks to improve this controller by adding a pitch angle adjustment depending on the operating point of the wind turbine and the power adjustment for grid support. The controller performance is analysed for three scenarios and for the whole operating range of the NREL 5 MW WT. Simulations show, that the adjustment lowers the risk for overspeed at the cost of an increased pitch rate. By contrast, the aerodynamic efficiency is not increased by the additional control loop. The effect on the tower depends heavily on the wind situation during and shortly after the grid frequency support event.