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Transient response of the flexible blade of horizontal-axis wind turbines in wind gusts and rapid yaw changes

Ebrahimi, A ; Sharif University of Technology | 2018

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  1. Type of Document: Article
  2. DOI: 10.1016/j.energy.2017.12.115
  3. Publisher: Elsevier Ltd , 2018
  4. Abstract:
  5. In this paper, the aeroelastic analysis of a large scale wind turbine rotor is performed with the aim of studying transient performance of turbine in extreme wind conditions, such as wind gusts and rapid yaw changes. The effect of the presence and/or lack of blade pitch control system on output power, rotor thrust, and blade deformation in sudden change of wind speed are investigated. The NREL 5 MW offshore wind turbine is used as the baseline case. In this regard, the modal approach is implemented for modeling the flexible blade structure with tension, bending and torsion degrees of freedom. The unsteady vortex lattice method is employed to obtain the aerodynamic loads. Moreover, the Lagrange equation is utilized to derive the governing dynamic equations and the yielded nonlinear system of equations is solved in time domain. Structure and aerodynamic models are validated by using standard cases. Wind turbine response to different scenarios for sudden change of wind speed and direction are investigated. The results show that the sudden change in wind speed leads to the emergence of overshoots (or undershoots) in output power as high as 40% (and 20%) for active pitch control case and nearly 25% and 20% gradual increment of thrust and tip deformations for inactive case. Time delay of recovering to the new steady-state output power is about 4 s (corresponding to one rotor revolution) and independent from the state of pitch control system. With sudden change of yaw angle, the turbine transient response gradually attains a new steady-state after a time delay of about 5 s. Moreover, results indicate that the output power and rotor thrust have a cyclical variation with the frequency of rotor rotation due to the asymmetric wake configuration. © 2017 Elsevier Ltd
  6. Keywords:
  7. Transient response ; Unsteady vortex lattice method ; Wind turbine blade ; Aerodynamics ; Aeroelasticity ; Control systems ; Crystal lattices ; Deformation ; Degrees of freedom (mechanics) ; Delay control systems ; Equations of motion ; Nonlinear equations ; Offshore wind turbines ; Superconducting materials ; Time delay ; Time domain analysis ; Transient analysis ; Turbomachine blades ; Vortex flow ; Wind ; Wind turbines ; Extreme wind conditions ; Horizontal axis wind turbines ; Large scale wind turbines ; Nonlinear system of equations ; Transient performance ; Unsteady vortex-lattice methods ; Wind speed and directions ; Wind turbine blades ; Turbine components ; Control system ; Elasticity ; Equipment component ; Steady-state equilibrium ; Unsteady flow ; Vortex ; Wind turbine ; Wind velocity
  8. Source: Energy ; Volume 145 , 2018 , Pages 261-275 ; 03605442 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S0360544217321588