Power Curve for Scratch Made Hugh Piggott Turbine

[Jake Konieczka]

Hello! I've recently been helping out an individual who built the 14' Hugh Piggott turbine model and he's been having trouble getting close to the expected power output.... It could be a range of factors but I believe the main contributor to it is the power curve settings on his inverter. His invertor is a ginlong GCI-3K-2G-W-US and from my knowledge he has not tweaked the factory settings on the invertor (Partly because the language on the invertor is also in Mandarin). From my understanding from reading different posts, we need a way to measure loaded DC voltage and the power output from the invertor to generate a power curve. I have also read about the use of an onsite anemometer to aid in tweaking power curve settings.

My main and general question is how do we approach the process for collecting relevant data to optimize his power curve? We recently purchased a data logger for the inverter that can track his power output, input voltage, etc. Would this information only be enough? I also want to understand the theory behind this as well so I can generate my own models.
Thanks

[Rob Beckers]

Hi Jake,

The default MPPT curve in the inverter is not likely to be a match of any kind to your friend's wind turbine. That would be sheer coincidence. Best case it overloads the turbine, keeps it stalled, and it just doesn't produce. Worst case the turbine is grossly underloaded, runs away, and self-destructs.

To create a better-matching MPPT curve I would need the following parameters:


Exact rotor diameter
The target TSR it is supposed to run at
Number of poles in the alternator rotor
The (unloaded) alternator AC Voltage at some RPM
The phase-to-phase resistance of the alternator


I think that's it, but will find out once I plug it into my spreadsheet.

-RoB-

[Jake Konieczka]

Thanks for the reply,

I actually do not know the phase resistance of the alternator or the unloaded AC voltage since I have not yet done a site visit. I was hoping when I do arrive on site in a couple weeks to have a plan to adjust the MPPT curve myself. I have a rough analytical model of his turbine in an equation solver program using dimensions from Hugh Piggott's book. Using the model, I have a rough idea of alternator resistance, unloaded AC voltage, and some other parameters. I do know that the person I am helping remade the blades and upgraded them to 8' (so a rotor diameter of 16') and the operating tip speed ratio given in the book is between 7-8.

Again, I am sort of asking if you could teach me how I can generate this MPPT curve myself and learn your methodology so I can continuously optimize his inverter settings when I do site visits. If this requires to detailed of a response, could you point me towards some sources that I could read up on? Thanks

[Rob Beckers]

Jake, I've attached the spreadsheet I wrote to do the heavy lifting. It's not pretty, ignores a bunch of things, but it does give you an MPPT curve that should be in the ballpark.

For refinements an anemometer, and data logger is needed. With an anemometer near hub-height the wind speed and turbine output power values can be logged. This is the turbine's power curve, and that's what needs optimizing; highest output power values for each wind speed. Them move the MPPT curve 20% down and repeat, 20% up and repeat. That will quickly give an idea in what direction MPPT values need to move for better output at various wind speeds.

All that said, actual energy production seems to be quite tolerant of MPPT curves that are a bit off. I know a number of people that are happy to run the stock curve that I generated with this spreadsheet.

-RoB-

[Jake Konieczka]

Thank you! I will let you know how things go. So far his power production in the month of January was 112 kW-hr but Hugh Piggott's book predicts somewhere around 300-400 kW-hr so hopefully we will see improvement after altering the MPPT. One last quick question, what is the "cube efficiency" you have in your spreadsheet?

[Rob Beckers]

"Cube efficiency" is a simplified attempt at capturing that the (base) energy produced by a rotor does not quite increase with the cube of the wind speed, but a bit less than that. Due to inefficiencies. That came about after observing that power curves of real-life wind turbines don't follow the cube of the wind speed.

-RoB-