Allowable Pitch Angle of Aerodynamic Imbalance Due to Individual Pitch Movement for Ultimate Loads on Offshore Wind Turbine Using Artificial Neural Network

Abstract

This study aims to calculate the ultimate loads through integrated load analysis under aerodynamic imbalance by individual pitch movement of offshore wind turbines, and based on this, to identify the allowable region of the individual pitch angle of the blade. For this, 5 MW offshore wind turbines were modeled using GH-BladedTM based on jacket type substructure data of the NREL-5 MW generic model and Upwind reports. For integrated load analysis, wind speeds were selected: 11 m/s, 14 m/s, 17 m/s, 20 m/s, 22 m/s, and 24 m/s. Ultimate load analysis was performed through the fixed pitch control mode with the individual pitch angles at an interval of 2°, ranging from 0° to 30°. Analysis was performed for the collective pitch control under the same environmental conditions as IPC. Through the comparison of loads at hub for CPC and the individual pitch movement states calculated through integrated load analysis, we identified the allowable pitch angle region where the ultimate loads of the individual pitch movement conditions were less than those of the CPC conditions. Furthermore, pattern analysis was performed using the artificial neural network for numerical modeling of the allowable pitch angle region. The results confirmed a high success rate of over 99%. Based on these results, this study suggested a new model according to the wind speed for the allowable pitch angle region.

Keywords

• aerodynamic imbalance
• artificial neural network (ANN)
• collective pitch control (CPC)
• individual pitch control (IPC)
• ultimate load