I am using FAST through MATLAB, simulating the NREL 5MW reference turbine. My goal is to study the effect of wind farm control on an array of 3 aligned turbines. Right now I’m focusing on the impact of applying axial induction control strategies by changing the pitch on 1 turbine, on both energy production and loads.
To do so, I started with the Cert19 example, and changed the Simulink open loop model, so the pitch controller takes an input variable. Then, I ran several consecutive simulations with different pitch settings supplied to the blades, ranging from 0 to 5º, with steps of 0.5º. The simulations were done with a wind profile generated by TurbSim, with wind speed = 8 m/s and turbulence intensity = 6%. But I ran into a problem.
The next picture shows the results of such simulation. On the right is the labels of the columns of the left table. For pitch settings of 1.5º or higher, both the power and thrust coefficients drop tremendously. This is not expected at all, since based on figure 2 of article “Comparison of Actuation Methods for Wake Control in Wind Plants” (Gebraad 2015, attached), both coefficients should decrease as de pitch decreases, not drop abruptly.
To understand what is happening, I decided to plot the angle of attack along the blade, for pitch = 0º,1º and 1.5º. Below I show the plot for output node 3 on blade 1.
There are severe oscillations on the angle of attack along the blade. What is happening here? What should I do to properly test the effect axial induction control on control region 2?
I am thankful for the time taken reading this post, and any help you migth be able to provide.
Comparison of Actuation Methods for Wake Control in Wind Plants.pdf (1.12 MB)