Hi jason
I just want to reproduce the controller test about OC4semi-sub. I chose the turbulent wind produced by turbsim with mean wind speed U=12m/s. I didn’t change the parameters about the turbsim and controller( Bladed-style pitch controller together with variable speed generator. When it comes to the wind speed near rated, i become confused. Turbulence intensity is 17%，turbulent model is IEC Kaimal. I don’t know why the turbulent wind velociy excursion is so large , the same with blade pitch angle（excursion is 10deg. Does it reasonable? The enabled DOF are drivetrain and generator, all other DOFs are disabled. I know here there is a frequent transition between two controllers. From the source code, i know the key parameter is generator speed. Different generator speed corresponding to different region. But in terms of pitch controller, i cannot understand the criterion. Could you help me clarify how the pitch controller works when in Region2, keep the minimum pitch angle? I didn’t find it in the source code. It seems in the code that the gains are a function of the speed error. To my understanding, the speed error could be positive or negative, that is to say it works in region2 and region3.
Also, the relation between wind speed and the generator speed may be linear or at least the same trend. I know it is calculated in aerodyn and elastodyn, but i found the theory a bit complex. Are there any simplified or conclusive assessment? I just want to check if the result make sense.
Besides, i checked some post. You mentioned during linearization we need use wake frozen assumption. Since here the controller is well documented, I don’t need to find the power sensitivity. When running the code, i chose the wake frozen assumption flag"false", is that right?
Thanks for your time. I really appreciate your patience and all the devotion to the forum.
Best regards
Lulu
Dear @Lulu.Liu,
Just a few comments/questions:
- Are you using the baseline controller for the NREL 5-MW baseline wind turbine atop the OC4-DeepCwind semisubmersible, i.e., DISCON_OC3Hywind.dll?
- The baseline controller for the NREL 5-MW baseline wind turbine is documented here: https://www.nrel.gov/docs/fy09osti/38060.pdf, with the OC3-Hywind updates used by the OC4-DeepCwind semisubmersible documented here: http://www.nrel.gov/docs/fy10osti/47535.pdf.
- The frozen wake model of AeroDyn is only used in the linearization process; it will not affect time-domain simulations.
Best regards,
Hi Jason
Thank you for your quick reply. Yes, I am using the baseline controller DISCON_OC3Hywind.dll. I think the source file is DISCON_OC3Hywind.f90. The updates for Hywind is a spar platform. I checked the source code. From the comment, it seems for Hywind we need some modification. For OC4 semi-sub, am I supposed to get my own Power sensitivity against pitch angle? The parameter obtained for the definition of 5MW-wind-turbine control system is just for the wind turbine without any platform. So i must calculate the Kp and KI for OC4 semi-sub rather than using the Hywind(atop on a spar) ? Otherwise the controller performance may not be correct? Sorry about my ignorance about controller at this moment.
Best regards
Lulu
Dear @Lulu.Liu,
The power sensitivity to pitch is a property of the rotor, not the support structure, and so, should not change for different support structures. We’ve used the same baseline controller for the OC4-DeepCwind semisubmersible that we used for the OC3-Hywind spar. It sounds like you are using the correct controller.
Best regards,
Hi Jason，
Thank you for your reply. I was just wondering about the large pitch excursion with the controller. But the generator speed error and control logic make sense.
Dear @Lulu.Liu,
Large pitch variations are expected in turbulent wind around the rated wind speed.
Best regards,
