Good evening,
I’m trying to make a model for a synchronous generator with gearbox ratio equal to one (with permanent magnets) using the DISCON subroutine and I’m having a few problems.
For this task, I’m using the “Test26” files that are attached in FAST v8.15 just changing the RotSpeed to 12.2 (the rated rotational speed that I want to have), the GBRatio to 1 and the GenIner from 534.116 to 200000 (due to the greater mass of this kind of generator) in the ElastoDyn Input File. Moreover, in the DISCON subroutine file I have changed the following values:
PC_RefSpd = 123.9254 → 1.27758 (value for 12.2 rpm)
VS_CtInSp = 70.16224 → 0.723322
VS_MaxRat = 15000.0 → 1455000.0 (is just a order of magnitude)
VS_MaxTq = 47402.91 → 4560396.2
VS_Rgn2K = 2.332287 → 2128615.4
VS_Rgn2Sp = 91.21091 → 0.940319
VS_RtGnSp = 122.6861 → 1.27758
The other inputs of DISCON file remain unchanged.
After compiling, the main problem is that the solution appears to fail between the 150 and the 200 seconds of simulation (more or less), giving the following message:
“Timestep: 158 of 300 seconds. Estimated final completion at 00:20:11.
Warning: Turning off Unsteady Aerodynamics due to high angle-of-attack. BladeNode = 7, Blade = 3
Warning: Turning off Unsteady Aerodynamics due to high angle-of-attack. BladeNode = 6, Blade = 3 […]”
On the other hand, the system seems to become unstable when I decrease the VS_Slpc value (that should be zero).
I’ve attached a phew graphics in this post with the results obtained just to show the problems after changes. The graphics shows the WindVelocity, PwrGen, RotSpeed and PitchAngle in this order.
You can see how the power for some values in the range 150-200 sec become negative.
For all of this, I would like to know if someone has tryed to use the DISCON subroutine for generators with GBRatio = 1 before and, if it ran ok, what am I doing wrong?
Thank you in advance,
Marcos