Smart load control on large-scale wind turbine blades due to extreme coherent gust with direction change

Abstract

The control of a typical extreme load with varying velocity and direction, i.e., International Electro-technical Commission Extreme Coherent Gust with Direction Change (ECD) load, was investigated on an Upwind/National Renewable Energy Laboratory 5 MW reference wind turbine using a newly developed smart blade system. The control action was implemented through the local perturbation of the Deformable Trailing Edge Flap (DTEF) on the blade surface and thus flow-blade system. The investigations were separately conducted within four time zones, depending on the complex yaw or/and pitching functions of the turbine. It was found that, without DTEF control, the flapwise root moment and tip deflection of the blades experienced rather complicated fluctuations due to the ECD load, together with the influence of blade yaw and pitching. On the other hand, the smart rotor control was very effective to reduce both blade flapwise root moment and tip deflection up to 30% and even more. The good control performance lied in the altered nature of the flow-blade interactions by the local controllable DTEF perturbation to change the in-phased fluid-structure synchronization into anti-phased collision at dominant load frequencies, thus significantly enhancing the damping of fluid-structure system and impairing their correlations. Consequently, the ECD load on the rotor and even drive-chain components would be greatly suppressed.