Affection Of Pitch Control On Wind Turbine Noise Reduction

Noise from wind turbines makes a big challenge for the wind turbine industry to develop onshore wind energy further.The traditional way of reducing noise is to design low noise wind turbine airfoils and blades.New noise measurements reveal that noise level changes for wind turbines during wind shear and yaw operation,which gives more annoyance to the people living nearby.In this MSc project,noise emission from wind turbines in wind shear and yaw operation is studied by a solver combined with aerodynamics and aeroacoustic programmes.The numerical tools are the fluid field solver EllipSys3D,the aerodynamic solver FLEX5 and an existing noise prediction model BPM.This coupled solver makes a good match to experimental data.All simulations and tests were made on an NM80-2.75MW wind turbine equipped with blades from LM companyIn this Master thesis,the aerodynamic and noise characteristics of NM80 wind turbine under different yaw and wind shear conditions are compared.The study shows that the existence of wind shear and yaw decrease the aerodynamic characteristics of the wind turbine,and wind shear can lead to an increase of wind turbine's aerodynamic noise while yawing results in a reduction of aerodynamic noise.This thesis proposes two pitch control methods for the present solver based on the traditional pitch control strategy.By calculating and comparing the aerodynamic noise of the wind turbine under four different inflow conditions with pitch control strategies,the research illustrates that the sound pressure level(SPL)of wind turbine aerodynamic noise can be reduced by approximately 0.3 dB under a 0.3 wind shear exponential coefficient condition.At the same time,no significant difference of SPL can be noticed under a 10-degree Yaw condition.There is also no significant difference in A-weighted SPL with or without the pitch control.It is because the main reduction of wind turbine aerodynamic noise happened in the low-frequency region(below 315Hz),which A-weighted method focus on the frequency region humans are more sensitive.