power curve

[Hans Zurne]

Hello
may be some one can help me to get my power curve perfect
i have a 3 kw wind turbine , grit connected , 3 phase , 380 volt ,4 meter wheel , dumpload starts at 390 volt
and a 5 kw ginlong inverter
the factory supplied the following output data for the turbine
windspeed working voltage power
3 108 251
4 142 672
5 183 1004
6 217 1506
7 251 1973
8 291 2198
9 374 2319
10 380 2650
11 380 3000
12 380 3400
13 380 3700
14 380 4000
15 380 3800
16 380 3600
17 380 3300
18 380 3000
from this i guessed and made a power curve , and the wind mill works reasenable well
but i feel that i have to changes some figures to make it perfect
hope someone can help me

kind regards

Hans

[Rob Beckers]

Hi Hans,

Is the diameter exactly 4.0 meters? What type is this, a HAWT?
Running the numbers you gave, the output power is somewhat optimistic and I suspect your turbine is being overloaded (resulting in turning slower than it should, at a lower TSR, which is less efficient).

Assuming 35% overall efficiency (pretty good for a small HAWT), 4.0m diameter, and 380V DC at 'rated' output with 10 m/s wind speed, I get the following:

Wind (m/s) RMP DC Volt Watt Out
3 95 125 25
3.5 110 145 63
4 126 164 113
4.5 142 184 176
5 158 203 255
6 189 240 465
7 221 277 756
8 252 312 1141
9 284 346 1632
10 315 380 2241

Ignore the RPM column, this is based on an assumed TSR of 6.6, and I don't know what yours was designed for.

The first point of the MPPT curve would be 120 Volt - 0 Watt, to give the turbine a chance to spin up without a load. Startup Voltage would be something around 110 Volt DC. You don't need all these points in the inverter, about 5 or 6 spaced reasonably to approximate the curve would be fine.

There is no point in adding any MPPT points above 380V if the Voltage is the same (or lower), the inverter doesn't use those. It has to be a continuously rising curve.

No guarantees... Hope this helps!

-RoB-

[Hans Zurne]

Hi Rob
Thank you very much for your reply, your input is a big help
my turbine is HAWT , bought from huaya, the wheel is exactly 4 meters
my inverter allow for 4 powercurves to be put in
so, i typed your suggested curve in, and it went heapes better
but it went to fast above 250 volts
so, i made adjustments and it is running pretty good now, may be still a bit fast

thanks again for putting me on the right path

kind regards

Hans

[Rob Beckers]

Good to hear Hans!

There is a way to optimize the MPPT curve. Ideally that's what the manufacturer should do, but I suspect many Chinese turbines are barely tested when they go in production...

If you mount an anemometer on an arm (to avoid tower interference) just under the blades you can measure wind speed, and at the same time power output from the inverter. Collect datapoints, and plot wind speed vs. power output (no need to calibrate the wind speed, as long as it gives the same value for the same wind speed). That plot is the turbine's power curve: output power vs. wind speed. The idea is to make this curve as high as possible, the highest power values for each wind speed, by changing the MPPT curve (gradually).

-RoB-

[Hans Zurne]

I might just do that
thank you Rob

Hans