IEA 15 MW on UMaine Semi-Sub Floater: Reason for Maximum Thrust Value in the Peak Shaver Routine

Wind & Water Controls
1

Dear all,

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.
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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?

Best regards,
Ioannis Voultsos.

2

Hi Ioannis,

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.

During the tuning, ps_percent=0.8 was used. You can see this in the ROSCO toolbox tuning .yaml file here:
https://github.com/IEAWindTask37/IEA-15-240-RWT/blob/master/OpenFAST/IEA-15-240-RWT-UMaineSemi/ServoData/IEA15MW-UMaineSemi.yaml

Hope this helps,
Nikhar

3

Dear @Nikhar.Abbas

Do we have the controller discon.dll for 15MW Umaine Semi somewhere?

Best regards
Ramesh

4

Dear @Ramesh.Kumar,

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.

Best regards,

5

Dear @Jason.Jonkman

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.

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Is floating feedback affecting the blade pitch and we don’t achieve the same power as in Monopile case?

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Best regards
Ramesh

6

Hi Ramesh,

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.

Best, Dan