Some thoughts on load control of a wind turbine, feed forward or feedback ?

[SparWeb]

Yes, I realize that a yacht can go faster then the wind speed, when close hauled, but I find it difficult to believe a wind turbine just keeps accelerating to infinity.

Infinity?  No.  Speed of sound?  Yes indeed.

A 3m (10 ft) set of blades will accelerate up to 2000 RPM if there is nothing else to resist the rotation but drag.
That is exactly what Paul experienced, including the noises (aircraft and helicopter propellor tip speeds are up to Mach 0.9).

I made the same mistake with the first propellor I built.  (Wow 20 years ago...) I put it on a fencepost to spin free and left it unattended.  It was a calm afternoon, and wind rose up later.  Came back after supper and picked up bent and broken pieces.

You always need a load on a turbine rotor, preferably with some redundancy.

[Warpspeed]

Well, I have definitely learned something I did not know.

I was well aware that high performance yachts can go faster than the wind (not when sailing straight down wind of course) but when sailing across the wind.
https://www.sail-world.com/Australia/How-DOES-a-sailboat-go-faster-than-the-wind/-54408?source=duckduckgo
But never thought to apply a similar effect to a blade profile on a turbine.
I should have figured that out myself, and later did, but only after my error was pointed out to me.

It does not really take anything away from the original proposed concept of trying to achieve optimum loading over the full usable range of wind speeds.
What you do with the recovered electrical power after that, is an entirely different matter.

[Mary B]

nothing low cost about reliable diy power electronics, unfortunately.

the lowest cost boost converter i could sell anyone here, would be to simply use the inductance of the transmission line and the turbine as the inductor and simply use 3, mosfets wired back to back (100 volt fets for a 48v system) and turn all of them on and off through a optical isolator. each source of the mosfet is connected together, each drain goes to the 3 phases. you turn them all on at the same time and turn them all off at the same time. regarding power factor? it won't meet the 5% THD requirement for industrial equipment but it is better than a simple rectifier.

you stick with the existing bridge rectifier and battery load. an additional capacitor would need to be added to buffer the inductance of the battery, and a small rectifier and energy recovery snubber could make it work pretty well.

the emi will be pretty incredible, since the entire distance from the rectifier to the turbine is an antenna running at say, 5 to 50Khz with rise times on the order of 1uS or less at around 100 volts peak to peak.

Do this and risk a visit from the FCC or your countries version of it... that is going to spew noise into the low microwave region.

[joestue]

an active or passive energy recovery snubber could keep the highest radiated frequency under 100 khz which might just work.

where as a simple boost converter has a 100 to 500ns rise time which would correspond to 10Mhz.

[Warpspeed]

If EMC is an absolutely vital issue, high frequency pwm is probably not the best solution anyway.

How about phase control combined with a buck/boost transformer ?
https://www.bristolwatch.com/sr/buck_boost.htm

If its single phase (very unlikely) a 600 Va transformer could boost the voltage by 20% at 3Kw power level.
If three phase, three 200 Va transformers would achieve the same thing.

SCRs ot triacs could switch at the frequency of the alternator, and only have one turn on event each half cycle per phase.

Many different ways to skin a cat.

[Mary B]

Countries are cracking down on RFI generators... cable company here got fined $50k for not repairing leaky connections and patches(I swear, this is one of their patches, lightning fried the cable so they exposed enough center conductor to weld it together then they wrapped it with aluminum foil and duct tape... yeah it leaked bad. Just one of many I found then the helicopter over flight found a bunch more) plus the electric utility got fined for 20 noisy connections... what years of neglect gets you.

To many complaints of cheap imported junk causing issues so they are starting overflights of most towns over 2,000 and smaller ones f there have been complaints. I have the local electric utility on speed dial to report issues close enough (1/2 mile) to my house to cause issues LOL FCC has a standing complaint form from me for bad noise generators. If I can hear my own radar return from a moon reflection on 144mhz I can hear these bad insulators 1/2 mile or more away!