Nonlinear Stability Analysis of High-Power Wind Turbines under Strong Wind Variations

This paper analyzes the nonlinear stability of high-power wind turbines with pitch regulation under strong wind variations. The focus is placed on identifying stability limits rather than energy efficiency, emphasizing how nonlinear effects influence the dynamic response. A nonlinear aero-mechanical model, calibrated with SCADA data from a 2.5 MW turbine in Dobrogea (Romania), is used to examine different wind profiles. Two scenarios are investigated: linear ramps with proportional pitch variation and exponential wind growth resembling gusts. Results indicate that above a critical threshold of about 14 m/s, linear pitch strategies fail to ensure stability due to actuator limitations and nonlinear displacement of the operating point. Exponential growth further accelerates instability, often leading to shutdown. The study highlights the necessity of nonlinear modeling and adaptive pitch control strategies to extend the stable operating range of modern wind turbines.