I have noticed an unexpected behavior of the NREL 5MW wind turbine in rated power production and I wonder if someone could give me an explanation.
As part of my Master thesis, I am doing simulations with FAST v7 and an external control in Matlab / Simulink. We are testing the performance of the wind turbine in high wind speed scenarios (above 21 m/s) and reducing the torque and speed of the generator.
We have observed that by slightly reducing the rotational speed reference, the pitch angle increases, which makes sense due to the implemented pitch control loop. The problem comes when the reduction of the rotational speed reference is bigger. In that case, the power production drops to 0 and the pitch angle goes to 90º. As a result, we would like to know if there is any condition in FAST whereby if the pitch angle reaches a certain value, the wind turbine is disconnected from the grid and goes to idle. Because our external control system does not consider such a condition.
If such a condition would exist, it would limit our capacity to reduce the rotational speed reference of the wind turbine at high wind speed scenarios.
There is nothing controls-related that is built-in within FAST v7 that is outside of the user-specified control settings. There are override pitch maneuver settings and settings to disable the generator that are user-specified. What control settings have you defined in the FAST v7 input file?
We have found the problematic logic inside our external control strategy, but thank you for your help and rapid response.