Sinusoidal Blade Pitching Causing Negative/Discontinuous Output

Wind & Water Computer-Aided Engineering Software Tools
1

I’m attempting to model sinusoidal pitching of turbine blades but am encountering negative outputs, namely in RtSpeed, GenTq, and GenPwr. I am using 5MW_Land_BD_DLL_WTurb as a starting point with a 400 second run time, 0.0015 DT, and 8 m/s inflow wind with low IECKAI turbulence. I am using simulink for the pitch controller and all other options in servoDyn uses default values. The pitching simulink is a simple sine wave generator set to O(t) = 0.044sin(2pi/63 *t) with identical outputs for each blade. My goal is to reproduce results from this paper.

Attached are the results; as you can see, RtSpeed, GenTq, and GenPwr all follow disjointed paths and have negative values.

output_forum_submission
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Debugging that I’ve tried

  1. Reducing the time step to 0.0009 but saw no change
  2. Doubling the inflow speed, that prevented negative values for GenTq and GenPwr and appeared normal but resulted in a tower strike error.

I can attach any additional input/source files if needed.

2

Dear @Ben.Pelson,

Can you clarify how you are computing the generator torque? I would guess the rotor speed fluctuations are commensurate with the torque control you are using. If you are continuing to use the baseline variable-speed torque controller, I would guess this could be problematic because the torque control region in this controller is impacted by the blade-pitch angle computed by the controller, which you are overriding by your Simulink signal. My guess is that you’ll need to change the torque control logic a bit.

Best regards,