I am simulating the IEA 15 MW RWT on the UMaine semi-submersible floater in order to understand the power variations due to the platform pitch angle and the peak shaver routine.
As stated in Figure 9, p.65 of the paper of Abbas et al(2022),“A reference open-source controller for fixed and floating offshore wind turbines”, the maximum rotor thrust, considered in the peak shaving routine of the associated controller is nearly 1.95 MN.
Is there a particular reason for choosing this value as the maximum rotor thrust? In addition, is it possible to know what peak shaving percentage was taken into account into designing the peak shaver routine?
I wouldn’t say that there was a specific reason for choosing this value for the maximum rotor thrust other than using sort of “rule of thumb” guidelines and a subsequent analysis by the designers to ensure that the results are reasonable. One could certainly do a more extensive loads and power analysis to try to define a peak shaving percentage that has some sort of optimality associated with it.
You can find precompiled versions of the ROSCO DISCON DLL for Windows (libdiscon.dll) on the ROSCO GitHub site: Releases · NREL/ROSCO · GitHub. The same DLL can be used for all variations of the IEA Wind 15-MW RWT; it is only the ROSCO input file (DISCON.IN) that changes.
Thanks for the prompt response and confirming that we have same .dll. My concern is around getting different power at same inflow condition and initial rpm in the ED to simulate the rated condition. V=10.59m/s at 7.55RPM.
In steady state, the floating feedback should not create a pitch offset. There is about a 5-6 degree offset in the platform pitch that reduces power. The difference in blade pitch (due to peak shaving) will also reduce the power.
I recommend looking at the OpenFAST outputs for a clearer comparison.
SD_MaxPit - Maximum blade pitch angle to initiate shutdown [rad]
is set to approximately 0.6981 rad (39.99°). This parameter defines the pitch angle threshold beyond which the controller commands a turbine shutdown sequence, ultimately driving the blades to 90°.
According to the IEA 15 MW RWT technical report, the controller pitch demand at the rated maximum wind speed (25 m/s) is about 23°.
Based on this, one would expect the SD_MaxPit threshold in the DISCON file to be set slightly above that operational value, so that if the controller were to exceed this pitch angle, it would indicate that the 25 m/s wind speed has been surpassed and the controller should then initiate a shutdown procedure. Instead, the value is set nearly twice as high (~40°), which appears considerably larger than necessary.
Is there any particular reason I may have lost behind selecting ~40° for this parameter? Is this intended as a highly conservative safeguard, or is there another design consideration involved?
Dear @Daniel.Zalkind ,
Thank you for your reply and clarification. I lost the latest example of the 15MW IEA with the new version of ROSCO along the way.
