Electromechanical Dynamics of Controlled Variable-Speed Wind Turbines

Variable-speed wind turbines are increasingly penetrating into the electrical grid, replacing the conventional synchronous-generator-based power plants and thus decreasing the available inertial response for primary frequency stability. This paper offers a deeper understanding of variable-speed wind turbine generators (WTGs) in the context of maximum power point tracking and obtaining primary frequency response. Linearized models have been obtained between the wind velocity and the system frequency versus the power output. System complexity has been studied from the point of view of modal analysis of a two-mass drive train model of a WTG, as well as Hankel singular values. Finally, individual WTG models have been combined to form wind farms, whose complexity has again been found to depend on the nature of modeling of the WTG drive trains.