I'm doing a project on the NREL 5-MW Baseline wind turbine with TLP Configuration. I tried to extract linearized models with FAST v8 and I realized that whenever the first side-to-side tower bending-mode DOF is on, an RHP zero appears in the 2*2 transfer function matrix from inputs [generator torque; collective blade pitch] to outputs [High-speed shaft power; Platform pitch tilt rotation]. Moreover, with turning the second side-to-side tower bending-mode on, an RHP pole appears in the transfer function matrix.
By applying the GSPI controller (when second side-to-side tower bending-mode is on), FAST encounters an error:
Code: Select all
FAST_Solution:FAST_AdvanceStates:ED_ABM4:ED_CalcContStateDeriv:SetCoordSy:Small angle assumption
violated in SUBROUTINE SmllRotTrans() due to a large tower deflection (ElastoDyn SetCoordSy). The
solution may be inaccurate. Simulation continuing, but future warnings from SmllRotTrans() will
Additional debugging message from SUBROUTINE SmllRotTrans(): 3.25 s
FWind_CalcOutput [position=(3.77776E+08, -2.79132E+09, 2.71944E+05) in wind-file coordinates]:
Error: FF wind array was exhausted at 3.35 seconds (trying to access data at -2.07569E+07
CalcOutputs_And_SolveForInputs:SolveOption1:ED_HD_InputOutputSolve:HydroDyn_CalcOutput: Angles in
GetSmllRotAngs() are larger than 0.4 radians.
ED_HD_InputOutputSolve:HydroDyn_CalcOutput: Angles in GetSmllRotAngs() are larger than 0.4
FAST encountered an error at simulation time 3.3 of 300 seconds.
Simulation error level: FATAL ERROR