Comparison of an island Wind Turbine Collective and Individual Pitch LQG Controllers Designed to Alleviate Fatigue Loads
Résumé
This paper aims to analyze different LQG controllers' performances in terms of reducing the fatigue load of Wind Turbines' (WT) most costly components caused by the spatial turbulence of wind speed. Five LQGs with increasing control model complexity and a greater number of objectives are designed, the first four with Collective Pitch Control (CPC), and the fifth with Individual Pitch Control (IPC). LQG0_CPC is only designed to regulate generator power and rotational speed in Full Load (FL). LQG1_CPC also endeavour to reduce drivetrain loads. LQG2_CPC, associated with an accelerometer placed in the nacelle, also aim to reduce fatigue related to tower fore-aft deflection. LQG3_CPC and LQG3_IPC are associated with sensors placed on the blades and also try to reduce fatigue loads related to the flap-wise deflection of blades. In the design of the controllers, firstly a linear control model is obtained in the operating point corresponding to a wind speed of 18 m/s. Then, the Kalman Filter (KF) and the rest of the controller are tuned with simulations in order to obtain the lowest possible fatigue loads while respecting certain generator power and speed variation limits. Finally, the five controllers are tested with Processor-In-the-Loop (PIL). Fatigue loads are evaluated by Rainflow Counting Algorithm and then applying the Palmgren-Miner rule. Tests results show that drive-train loads are significantly reduced from LQG1_CPC, that the complexity of the controllers does not have a significant influence on the reduction of tower loads, and that LQG3_IPC allows fatigue loads on blades to be alleviated considerably.