Hi to all,
for the purposes of my research project I am trying to develop an effective wind speed estimator in Simulink for the 5 MW Fast Wind Turbine, in line with the work iopscience.iop.org/1742-6596/75/1/012082 appearing in the above post. My progress so far, is summarized as follows:
-
Assuming rigid drive-train (DrTrDOF=False in ElastoDyn ), the Aerodynamic torque Ta (Qa in the paper above) is computed in Simulink through a Matlab function block by the following relation:
Ta=Jr*omegar_dot+LSShftTq,
where Jr denotes the rotor inertia (I took Jr=115.926 kg*m^2, hub inertia about low speed shaft found in “Definition of a 5-MW Reference Wind Turbine for Offshore System Development”), omegar_dot is the acceleration of the rotor (I take RotSpeed as output from FAST convert it to rad/sec by multiplying with pi/30 and then taking the derivative using a derivative block in Simulink), and LSShftTq is given, again, as output from FAST.
- Then from
2Ta/rhopiR^5omegar^2=cp(beta,TSR)/TSR^3=F(beta,TSR)
if one computes Ta and omegar (aerodynamic torque and rotor speed), the left-side term of the quation above is known and F (beta,TSR) is computed.
The table F vs TSR can be computed offline, using the knowledge of Cp(beta,TSR), thus for a given F, the tip-spped ratio TSR can be computed.To compute F=Cp/TSR^3 i have used the tables found in "NREL 5-MW reference turbine - CP, CQ, CT Coefficients - #13 by Sebastian.Hippel My results for Cp and F, for beta=0 when the wind turbine operates below rated power, are attached.
- Then, with TSR known the effective wind speed is given from V=omegar*R/TSR. I have developed all the previous steps in Simulink using a stepwise changing simulated wind speed, with wind speed below the rated wind speed. My concern is that, although the estimated wind speed converges to the simulated one there is a significant delay for the actual convergence which I can not explain. I have attached the comparison between the simulated wind speed and the estimated one. The actual response of the estimated wind speed resembles a lot the actual behavior of a low-pass filter- could dynamic inflow explain this behavior? Do you see any mistake i have done in my modelling design? I have also attached the AeroDyn file I have used for the simulations.
I am looking forward to your responses, thank you in advance for your comments.
Bart
