Mechanical impact of wind turbine frequency support strategies

New regulations require wind power plants to contribute to grid frequency control. Wind turbine droop control, inertia emulation and the use of a washout filter are compared in this paper in order to ascertain the influence of such methods on the mechanical components of the wind turbine. When wind generators operate below rated power, these methods use the stored kinetic energy to provide extra energy during a short period of time and hence enhance overall system frequency response. This paper includes the evaluation of the impact on the wind turbines of the aforementioned technologies, in a variety of scenarios, with a detailed model of the wind turbine. It is concluded that techniques that include a washout filter have similar performance to inertia emulation, but with without exciting lightly damped drive train modes.