Nonlinear individual pitch control of large wind turbines for blade load reduction

Abstract

As wind turbines (WTs) become larger in size, they are experiencing increasing structural loads on their flexible components. This may shorten the working life of WTs or even cause damage to them. This work proposes a nonlinear individual pitch control (IPC) strategy to mitigate blade fatigue load for WTs operating in the above-rated wind speed region. The controller consists of a blade vibration damper and a pitch angle lead compensator for each blade. The damper is used to damp the vibration of the blades, which is designed by nonlinear dynamic inversion (NDI) method to deal with the non-affine nonlinearity of the WT model. The lead compensator is used to compensate the delay between pitch angle command and actual angle caused by the pitch actuator. The simulation results with the aero-elastic model of FAST show that the nonlinear controller has a better system performance, compared with several other IPC controllers. Besides, the proposed approach is able to work well in large wind speed range, and is easy to implement for industrial applications.

Reduction of Structural Loads in Wind Turbines Based on an Adapted Control Strategy Concerning Online Fatigue Damage Evaluation Models

“…A number of control strategies taking into consideration the mitigation of structural loads have been proposed [15][16][17][18][19][20][21][22]. In [15], the aforementioned structural loads on rotor blades were mitigated using a nonlinear Individual Pitch Control (IPC). The controller proposed in [15] consists of a "blade vibration damper and a pitch angle lead compensator" [15].…”

“…In [15], the aforementioned structural loads on rotor blades were mitigated using a nonlinear Individual Pitch Control (IPC). The controller proposed in [15] consists of a "blade vibration damper and a pitch angle lead compensator" [15]. The vibration damper mitigates the blade vibrations, whilst the angle lead compensator compensates for the delay between the desired/commanded and the real pitch angle.…”