Investigação da influência do coeficiente de momento aerodinâmico no controle individual de passo de turbinas eólicas de eixo horizontal e três pás

Abstract

The growing demand for renewable energy drives wind exploration in Brazil and worldwide. This market calls wind turbines manufacturers for longer-lasting, more efficient and larger structures and equipment to harness more energy from the wind. A size growth consequence is the increase in intensity and asymmetry of rotor structural loads. Load reduction is always aimed to low the maintenance cost and increase durability. Individual pitch control (IPC) of wind turbine blades emerged as an alternative to reduce loads along the turbine structure. The effects of this type of pitch control can be verified through computational simulations. However, poorly detailed simulations with missing data can lead to bad predictions of the effects on a real turbine, causing imprecise results and analysis. Thus, this work aims to investigate the influence of the aerodynamic pitching moment coefficient on an individual pitch control in simulations of horizontal axis and three-bladed wind turbines performed in OpenFAST. As this software aerodynamic module requires lift, drag and pitching moment coefficients from -180 to +180 and the data provided was computed only for a short range of angles of attack, Du-Selig and Eggers correction and Viterna extrapolation models were used to process the data before simulations. Also, as the utilized IPC did not take into account the blade root torsion moment during hub loads calculation, new coordinates transformation equations were developed, implemented and tested. Following recommendations from IEC 61400 Part 13, the main variables analyzed in this work are blade root, tilt and yaw rotor moments. The simulation results indicated that accounting pitching moment coefficient and implementing more general equations did not lead to significant change in edgewise, flatwise blade root bending moments and tilt and yaw rotor moments, thus not affecting significantly the controller dynamics. However, the torsional blade root moment was largely affected by taking pitching moment coefficient into account. As this may impose constraints to the pitch system design, it was suggested to introduce this coefficient in the next individual pitch control studies to obtain more realistic results from aerodynamic simulations, open up space for more improvements and an even more robust controller.