Aeroservoelastic Pitch Control of Stall-Induced Flap/Lag Flutter of Wind Turbine Blade Section

Tingrui Liu

doi:10.1155/2015/692567

Abstract

The aim of this paper is to analyze aeroelastic stability, especially flutter suppression for aeroelastic instability. Effects of aeroservoelastic pitch control for flutter suppression on wind turbine blade section subjected to combined flap and lag motions are rarely studied. The work is dedicated to solving destructive flapwise and edgewise instability of stall-induced flutter of wind turbine blade by aeroservoelastic pitch control. The aeroelastic governing equations combine a flap/lag structural model and an unsteady nonlinear aerodynamic model. The nonlinear resulting equations are linearized by small perturbation about the equilibrium point. The instability characteristics of stall-induced flap/lag flutter are investigated. Pitch actuator is described by a second-order model. The aeroservoelastic control is analyzed by three types of optimal PID controllers, two types of fuzzy PID controllers, and neural network PID controllers. The fuzzy controllers are developed based on Sugeno model and intuition method with good results achieved. A single neuron PID control strategy with improved Hebb learning algorithm and a radial basic function neural network PID algorithm are applied and performed well in the range of extreme wind speeds.

Highlights

Stall flutter denotes unstable aeroelastic performance in stall conditions
The simplified stall-induced flap/lag flutter investigation of typical blade section plays an important role in this area due to its simplicity and convenience, so in this study, researches on aeroelastic instability and aeroservoelastic control will be depicted based on typical blade section
Aeroelastic stability of stall-induced flutter of special blade section with flap and lag motions based on unsteady dynamic stall nonlinear aerodynamic model is investigated

Summary

Introduction

Stall flutter denotes unstable aeroelastic performance in stall conditions. Stall-induced nonlinear flutter of wind turbine blade, as a typical nonlinear aeroelastic instable phenomenon, is an important reason of fatigue damage for wind turbine. The simplified stall-induced flap/lag flutter investigation of typical blade section plays an important role in this area due to its simplicity and convenience, so in this study, researches on aeroelastic instability and aeroservoelastic control will be depicted based on typical blade section. Structure modeling and aeroelastic stability analysis of individual blade section subjected to combined flap/lag motion are investigated [1]. The emphasis of pitch control is not on power and efficiency but on improving flutter suppression effect for destructive flapwise and edgewise motions of stallinduced flutter for wind turbine blade in large angle of attack behavior. Each of ΔCL and ΔCD represents the deviation of the linear static curve from the quasistatic curve for the lift and drag, respectively

System Linearization and Stability Analysis

Aeroservoelastic Control

Output

Output 1 2 Output 2

Conclusions

The Related Coefficients and Parameters of the Linearized Equation