A comparison of smart rotor control approaches using trailing edge flaps and individual pitch control

Modern wind turbines are steadily increasing in size, with recent models boasting rotor diameters greater than 120 m. Wind turbines are subjected to significant and rapid fluctuating loads, which arise from a variety of sources including turbulence, tower shadow, wind shear and yawed flow. Reducing the loads experienced by the rotor blades can lower the cost of energy of wind turbines. 'Smart rotor control' concepts have emerged as a solution to reduce fatigue loads on wind turbines. In this approach, aerodynamic load control devices are distributed along the span of the blade, and through a combination of sensing, control and actuation, these devices dynamically control the blade loads. This research investigates the load reduction capabilities of smart rotor control devices, namely trailing edge flaps (TEFs), in the operation of a 5 MW wind turbine. A feedback control approach is implemented for load reduction, which utilizes a multiblade coordinate transformation. Single input single output control techniques are employed to determine the appropriate response of the TEFs based on the blade loads. The use of TEFs and this control approach is shown to effectively reduce the fatigue loads on the blades, relative to a baseline controller. The load reduction potential is also compared to an alternative individual pitch control (IPC) approach, in the time and frequency domain. The effects on the pitch and power systems are briefly evaluated, and the limitations of the analysis are assessed. Finally, a combined approach that uses both TEFs and IPC is evaluated. Copyright (C) 2009 John Wiley & Sons, Ltd.