Structural load mitigation control for wind turbines: A new performance measure

Abstract

Summary Structural loads of wind turbines are becoming critical because of the growing size of wind turbines in combination with the required dynamic output demands. Wind turbine tower and blades are therefore affected by structural loads. To mitigate the loads while maintaining other desired conditions such as the optimization of power generated or the regulation of rotor speed, advanced control schemes have been developed during the last decade. However, conflict and trade‐off between structural load reduction capacity of the controllers and other goals arise; when trying to reduce the structural loads, the power production or regulation performance may be also reduced. Suitable measures are needed when designing controllers to evaluate the control performance with respect to the conflicting control goals. Existing measures for structural loads only consider the loads without referring to the relationship between loads and other control performance aspects. In this contribution, the conflicts are clearly defined and expressed to evaluate the effectiveness of control methods by introducing novel measures. New measures considering structural loads, power production, and regulation to prove the control performance and to formulate criteria for controller design are proposed. The proposed measures allow graphical illustration and numerical criteria describing conflicting control goals and the relationship between goals. Two control approaches for wind turbines, PI and observer‐based state feedback, are defined and used to illustrate and to compare the newly introduced measures. The results are obtained by simulation using Fatigue, Aerodynamics, Structures, and Turbulence (FAST) tool, developed by the National Renewable Energy Laboratory (NREL), USA.

Wind turbine robust disturbance accommodating control using non‐smooth H∞ optimization

“…To evaluate both speed regulation and structural load reduction and the relationship between those objectives, a covariance distribution diagram measure 19 is used (Figure 14). The generated power (proportional to the rotor speed) and the corresponding structural load (here is tower performances in speed regulation and structural load reduction, respectively.…”

“…The simulation tool and wind turbine model used are identical to those in our published papers. 13,19 The FAST tool provides a numerical process to obtain linearized models for controller design. 17 The tool computes the state-space system matrices for different azimuth positions of a predefined operating point.…”

Analysis of Wind Turbine Distances Using a Novel Techno-Spatial Approach in Complex Wind Farm Terrains

“…where the turbine rotor is shown with r, the speed avoided by the turbine rotor is shown by w e [37].…”

“…where: w 0 is the wind speed before reaching the turbine rotor, (m/s), then, behind the rotor, the wind speed is shown by w 2 , (m/s), the obtained radius-as a result of the wind speed change, is shown by r w , for a distance of x (m), with r showing the wind turbine radius, in m [37]. Then, the entrainment constant is shown by X, (/) [37]. C T shows the coefficient of wind-speed pressure, (/).…”

“…C T shows the coefficient of wind-speed pressure, (/). w w is the wind speed in a distance of x, (m/s) [37]. α indicates the deviation angle of the wake-speed deficit during the passage through the rotor of the respective turbine [37].…”