Lidar-assisted model predictive control of wind turbine fatigue via online rainflow counting considering stress history

Abstract

Abstract. The formulation of parametric online rainflow counting implements the standard fatigue estimation process and a stress history in the cost function of a model predictive controller. The formulation is tested in realistic simulation scenarios in which the states are estimated by a moving horizon estimator and the wind is predicted by a lidar simulator. The tuning procedure for the controller toolchain is carefully explained. In comparison to a conventional model predictive controller (MPC) in a turbulent wind setting, the novel formulation is especially superior with low lidar quality, benefits more from the availability of wind prediction, and exhibits a more robust performance with shorter prediction horizons. A simulation excerpt with the novel formulation provides deeper insight into the update of the stress history and the fatigue cost parameters. Finally, in a deterministic gust setting, both the conventional and the novel MPC – despite their completely different fatigue costs – exhibit similar pitch behavior and tower oscillations.

A wind turbine digital shadow with tower and blade degrees of freedom - Preliminary results and comparison with a simple tower fore-aft model

“…Fatigue loads in different wind turbine components, such as tower, blades, drivetrain, and others, cause permanent damage, in turn reducing lifetime and contributing to operational expenses [3]. As a consequence, fatigue reduction and lifetime estimation are of primary significance [4,5,6]. Thus, accurate fatigue estimation has become crucial in improving performance and reducing costs [7,8,9].…”

Robustness of LiDAR-assisted controller towards measurement uncertainty

“…[1], [2] and [3]. Most of the literature concerning LiDAR-assisted control employs a model predictive control (MPC) scheme like in [4], [5], [6]. The advantage is that the system disturbance, i.e., wind fluctuations, is known precisely in advance.…”

A Novel Load Extrapolation Method for Multiple Non-Stationary Loads on the Drill Pipe of a Rotary Rig

“…Online counting ensures the load sequence order, taking into account the effects of temperature gradients [4] and time-dependent damage mechanisms [5,6], but it may be limited by data storage and computational resources [7]. Moreover, online real-time counting may neglect the residual large loads, which can cause significant damage.…”