Feasibility of Aerodynamic Flap Hinge Moment Measurements as Input for Load Alleviation Control

摘要

This paper reports a feasibility study on flap hinge moments as sensor input for load alleviation control on smart wind turbine rotors. We designed a controller that used an indicial response method to predict the flap hinge moment assuming constant inflow. The controller compared the predicted with a measured hinge moment in disturbed inflow. The difference of the two values defined a flap deflection set point. To study the controller's performance, we carried out two-dimensional flow simulations with an unsteady incompressible Reynolds averaged Navier-Stokes code. We investigated a NACA63-200 type airfoil with a trailing edge flap of 16% chord length at a Reynolds number of Re=10~6. The results showed a reduction in lift coefficient variance, compared to the uncontrolled simulation, of 71.76% for a pitch oscillation amplitude of two degrees at a reduced frequency of k=0.1. For an amplitude of one degree and a reduced frequency of k=0.033 the controller could reduce the variance of the lift coefficient by 83.40%. The maximum flap deflection was four degrees in both directions. To prove the robustness of the control concept, we assessed the individual impacts of signal-to-noise ratio, first order sensor lag, incorrect flow velocity estimation, and increased angle of attack. We concluded that using the hinge moment as an input for load alleviation control was feasible.