Blade pitching for below rated turbulent speed.

[QusayHawari]

Hi,

I am running a closed loop response for the 15MW floater using a turbulent mean speed of 14m/s.

I set the following in Servodyn:

5 = PCMode,
5 = VSContrl,
0 = HSSBrMode
0 = YCMode.

Below you can see the wind speed [m/s] and the response of blade 1 pitch [degs]. Occasionally, the wind speed dips below rated. In that case the blade pitch should attempt to drop to 0 degs, but looking at the pitching, it seems that it's trying to maintain the blade pitch at around 10 degs, which is the operating point at 14m/s. Is this accurate?

Thanks in advance,
Qusay.

[dzalkind]

This looks about right for the steady-state values. Not sure why you're getting the 1 deg oscillations, but it seems like you were expecting that?

[QusayHawari]

Hi, Thank you for your response. Yes, the 1 deg oscillation is because I set 5 m of wave elevation to the structure. My question was that since the wind speed drops below the rated speed, shouldn’t the blade pitch try to dip down a little or approach zero to switch to region 2 /2.5. I can see that the average of the pitch is exactly the operating point value at the mean of the turbulent speed. Thanks, Qusay. Get Outlook for iOS<https://aka.ms/o0ukef>

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________________________________ From: dzalkind ***@***.***> Sent: Monday, March 28, 2022 6:23:59 PM To: NREL/ROSCO ***@***.***> Cc: Qusay Hawari ***@***.***>; Author ***@***.***> Subject: Re: [NREL/ROSCO] Blade pitching for below rated turbulent speed. (Discussion #120) ** THIS MESSAGE ORIGINATED OUTSIDE LOUGHBOROUGH UNIVERSITY ** ** Be wary of links or attachments, especially if the email is unsolicited or you don't recognise the sender's email address. ** This looks about right for the steady-state values. Not sure why you're getting the 1 deg oscillations, but it seems like you were expecting that? — Reply to this email directly, view it on GitHub<#120 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AV5GZZDOUKBMJ4EPEAZYHADVCHTK7ANCNFSM5RU6ZN6A>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[QusayHawari]

Hi Dan,

Thanks for your quick response.

I checked the operation for WE_Mode = 2 and compared that with WE_Mode = 0. In both cases PS_Mode = 1 for pitch saturation. All other settings are the same.

I think with WE_Mode = 0, the blade pitching relates better to the wind speed as it attempts to drop when the relative speed drops below rated, whereas when setting WE_mode = 2, the blade pitch is attempting to be fixed at the operating pitch point of 10.5m/s (mean of turbulent input).

Thanks,
Qusay.

[dzalkind]

When WE_Mode = 0, ROSCO is using the hub height wind speed, which might not be indicative of the rotor average wind speed (and the estimated wind speed). We typically only use WE_Mode = 0 for debugging the torque controller or to isolate issues in the wind speed estimator.

[QusayHawari]

Thanks,

Yes, I see, so for the correct closed loop operation WE_Mode should be set to 2 (EKF)?

Thanks,

[dzalkind]

That is correct.

[QusayHawari]

Great!

Thank you so much.

Qusay.