Abstract
Variability of wind profiles in both space and time is responsible for fatigue loading in wind turbine components. Advanced control methods for mitigating structural loading in these components have been proposed in previous works. These also incorporate other objectives like speed and power regulation for above-rated wind speed operation. In recent years, lifetime control and extension strategies have been proposed to guaranty power supply and operational reliability of wind turbines. These control strategies typically rely on a fatigue load evaluation criteria to determine the consumed lifetime of these components, subsequently varying the control set-point to guaranty a desired lifetime of the components. Most of these methods focus on controlling the lifetime of specific structural components of a wind turbine, typically the rotor blade or tower. Additionally, controllers are often designed to be valid about specific operating points, hence exhibit deteriorating performance in varying operating conditions. Therefore, they are not able to guaranty a desired lifetime in varying wind conditions. In this paper an adaptive lifetime control strategy is proposed for controlled ageing of rotor blades to guaranty a desired lifetime, while considering damage accumulation level in the tower. The method relies on an online structural health monitoring system to vary the lifetime controller gains based on a State of Health (SoH) measure by considering the desired lifetime at every time-step. For demonstration, a 1.5 MW National Renewable Energy Laboratory (NREL) reference wind turbine is used. The proposed adaptive lifetime controller regulates structural loading in the rotor blades to guaranty a predefined damage level at the desired lifetime without sacrificing on the speed regulation performance of the wind turbine. Additionally, significant reduction in the tower fatigue damage is observed.
Highlights
Advanced control methods for mitigating structural loading in these components have been proposed in previous works
To ensure utility-scale wind turbines operate with respect 20 to their design lifetime, advanced control strategies have been developed in recent years to reduce structural loading of blades and tower
The robust disturbance accommodating control (RDAC) controller (Do and Söffker, 2021), which is robust against modeling errors generates the primary CPC signal for rotor speed regulation and tower load mitigation, while adaptive independent pitch control (aIPC) is used as the lifetime controller to dynamically control the damage accumulation of the rotor blades
Summary
Growing demand for wind energy has led to the development of large wind turbines. these turbines are less tolerant to system performance degradation and faults (Gao and Liu, 2021). To ensure utility-scale wind turbines operate with respect 20 to their design lifetime, advanced control strategies have been developed in recent years to reduce structural loading of blades and tower Most of these incorporate additional objectives such as power optimization and rotor speed regulation. As an improvement to the approaches in the aforementioned contributions, the proposed adaptive lifetime control strategy regulates fatigue loading in the rotor blades to reach a predefined damage limit at the desired lifetime with subsequent reduction in tower damage accumulation. This is realized without trade-off in speed/power regulation performance. This section outlines the methods used for estimating the damage accumulation in wind turbine components
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