set PS_Mode to 3

[ptrbortolotti]

Purpose

Allow pitch to vary in reg I1/2, consistently with WISDEM

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
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Testing

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Checklist

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• I have run existing tests which pass locally with my changes
• I have added new tests or examples that prove my fix is effective or that my feature works
• I have added necessary documentation

[dzalkind]

I just pushed updated DISCONs. There were some minor numerical updates to the gains.

A major change is that we are now peak shaving at 80% of rated thrust near rated in the monopile model. This will change the thrust-based loads near rated operation.

Note that :

• PS_Mode in the DISCON is 0 or 1: whether or not is uses a lower pitch limit.
• PS_Mode in the tuning yaml is 0 to 3: Pitch saturation mode {0: no pitch saturation, 1: peak shaving, 2: Cp-maximizing pitch saturation, 3: peak shaving and Cp-maximizing pitch saturation}

This is an old, inherited naming convention that makes sense when you consider that the ROSCO dynamic library only uses the lower pitch limit, which is determined by the ROSCO toolbox tuning.

[gbarter]

@jennirinker - While looking into the pitch scheduling, we noticed a discrepancy in the peak thrust shaving input in WISDEM vs OpenFAST. What do you see in HAWC2?

[jennirinker]

Sorry, I need a bit more context to weigh in here.

My understanding is that you are proposing two different changes in the same MR:

1. Updating DISCON so the optimal pitch is maintained in minimum-rotor-speed regions
2. Adding in peak shaving

Is this a correct understanding?

Regarding the addition of peak shaving: this is a rather substantial change to the model. Why are we adding it now? It's not in the original docs, so this might confuse people unnecessarily. And if you add peak shaving with ROSCO, I don't know how we can mimic the same behaviour in the HAWC2 model with DTU WEC. So I'm a bit hesitant to greenlight this change without alignment.

[gbarter]

Sorry, I need a bit more context to weigh in here.

My understanding is that you are proposing two different changes in the same MR:

1. Updating DISCON so the optimal pitch is maintained in minimum-rotor-speed regions
2. Adding in peak shaving

Is this a correct understanding?

Regarding the addition of peak shaving: this is a rather substantial change to the model. Why are we adding it now? It's not in the original docs, so this might confuse people unnecessarily. And if you add peak shaving with ROSCO, I don't know how we can mimic the same behaviour in the HAWC2 model with DTU WEC. So I'm a bit hesitant to greenlight this change without alignment.

Ah, I think you are correct again, Jenni. I was confusing the details of the 15 and 22 ref turbines. Let's get together to discuss in real-time.

[dzalkind]

I think the decision around peak shaving was made because that parameter affects peak blade loading, and it should be shared for both substructures because the rotors are the same. @ptrbortolotti, feel free to weigh in.

Peak shaving can be implemented in the DTU WEC through this table: https://github.com/IEAWindTask37/IEA-15-240-RWT/blob/master/HAWC2/IEA-15-240-RWT-Monopile/control/wpdata.101

I reverted ps_percent to 1.0 for now, and am happy to go with the consensus.

1. Updating DISCON so the optimal pitch is maintained in minimum-rotor-speed regions

^ Technically, this hasn't changed, but the ROSCO DISCONs were due for an update.

[ptrbortolotti]

Should PS_Mode 0, 1, 2, or 3? And should it be the same for monopile and platform @dzalkind ?

[dzalkind]

PS_Mode should be 3 in the tuning yaml for both models.

ps_percent is a design decision based on the trade off for power/loading. It's been

• 0.8 for the floating substructure and
• 1.0 for the fixed bottom.

[gbarter]

Merging this in with a comment that we are setting ps_percent = 1.0, meaning there is no peak thrust shaving per discussion.