Abstract
Active wake management (AWM) via yaw control has been discussed in recent years as a potential way to improve the power production of a wind farm. In such a technique, the wind turbines will be required to work frequently at misaligned yaw angles in order to reduce the vortices in the wake area behind the turbines. However, today, it is still not very clear about how yaw operation affects the dynamics and power generation performance of the wind turbines. To further understand the effects of yaw operation, numerical research is conducted in this paper. In the study, the optimal size of the flow field used in the computational fluid dynamics (CFD) calculation was specifically discussed in order to obtain an efficient numerical model to quickly and accurately predict the dynamics and the performance of the turbines. Through this research, the correlation between the blade loads during yaw and non-yaw operations is established for aiding yaw control, and the blade loads and power generation performances of the wind turbine during yaw operation under different wind shear and blade deflection conditions are analyzed for understanding the effects of yaw operation. It is found that the optimal size of the flow field for performing efficient and accurate CFD calculations does exist. The misaligned yaw operation generally tends to decrease the loads acting on the blade. However, the aerodynamic energy captured by the turbine rotor and blade loads during yaw operation is not only dependent on the yaw angle of the rotor but is also affected by wind speed, rotor speed, the pitch angle of the blades, blade deflection, and wind shear. Particularly, it is interestingly found that wind shear can cause undesirable fluctuation of the power, which will challenge the power quality of the wind farm if no measures are taken.
Highlights
Despite the booming market of the wind industry [1,2,3], the further exploitation of wind power is still challenged by many constraints, one of which is the high levelized cost
Through comparing the volumes of the flow field as well as the number of meshes obtained at different outlet diameter to inlet diameter ratios, it is found that a sharp cone-shaped flow field should be avoided in computational fluid dynamics (CFD) calculations especially when the inlet diameter of the flow field is not large enough
Mathematical models that reflect the mismatch of rotor speed and wind speed, and the flapwise moment decreases with the increase of relationship between the blade loads and wind speed, rotor speed, yaw angle, and pitch angle are the yaw angle
Summary
Despite the booming market of the wind industry [1,2,3], the further exploitation of wind power is still challenged by many constraints, one of which is the high levelized cost. In the implementation of the AWM technology, the wind turbines are required to work frequently at misaligned yaw angles in order to reduce the vortices in the wake area of the turbines. This may cause many uncertainties, to blade dynamics and to the power generation performance of the turbines. The characteristics of the power produced during yaw operation have been studied before based on wind farm supervisory control and data acquisition (SCADA) data [22,27] It is still not very clear of the power fluctuation during this process under combined conditions of wind shear, blade deflection, and turbine control.
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