power curve

[Shaun Burgess]

hi rob more questions sorry . i have my power curve set at 180v to start and so up the 16 points . but what i have notice is that the I vin is reading 0.6amps at around 125v up to 180v but the I grid does not read any amps until 180v should i start my curve lower i no were talking about a small amps but its a shame to be losing it . have the resister in now and inverter is turning of now . and once the turbine is at the 70v to power up inverter is the inverter using no grid power at this point this time of year with low wind my turbine is just powering up inverter around 70 to 80v thats why at wondering thanks shaun

[Rob Beckers]

Shaun, please post your MPPT curve (by the way, you don't have to use all 16 points, for most cases half that number is plenty).

What does the output power on the inverter's display read for that range of 125V - 180V? What about input power?

It takes about 40 Watt to run the inverter itself, so there won't be any power to the grid until the turbine produces at least that much. However, 0.6A at 180V is over 100 Watt, so there should be some going out.

-RoB-

[Shaun Burgess]

here the curve at min
180v = 100watts
190 = 300
200 = 520
210 = 770
218 = 1140
230 = 1550
250 = 2000
273 = 2700
300 = 3400
328 = 3900
350 = 4450
376 = 4900
390 = 5400
398 = 5650
400 = 5800
420 = 6500
and the pout ramp is 9906.4
vinstart is 100
tprot uv 544 . rob could you explain these please . wind is up today.. if the curve starts at 180v does that mean dont export until i hit 180v thanks rob

[Rob Beckers]

The first point on the curve should be '0 Watt'. So, 100V - 0W if that is where you want it to start. For a 6kW turbine I would put the 100W point very close to the starting voltage though, so something like 170V - 0W, and Vstart = 170V in that case (no point in firing up before).

Without a 0 Watt point at the start of the curve I don't know what the inverter does. My guess (from what you're saying) is that it always regards that first point as zero output.

For the 6kW inverter I would not go above 6,200 Watt. That is a safe maximum that the inverter can do long-term without damage. You can program higher values, and I believe the inverter will output more than 6.2kW, Power-One suggests sticking to a maximum of 6.2kW.

When I plot your MPPT curve, I get what is more-or-less a straight line from 0 Watt at 180 Volt to 6.5kW at 420 Volt (in fact, you could leave all the intermediate points out and it would do the exact same thing, the turbine won't see the difference with this curve). For wind turbines the MPPT table almost always follows a cube-curve, where output power goes up with (nearly) the cube of the voltage (i.e. voltage * voltage * voltage * factor).

-RoB-

[Shaun Burgess]

thanks rob will change it this evening. thats the curve that fortis gave maybe i should play around with it not sure what to do ..what is the pout ramp and tprot should i change them to thank you shaun

[Rob Beckers]

"Pout Ramp" tells the inverter how fast the output power should react to changing in the input voltage. It's in "Watt per second". For example, say it's set at 500 Watt/s, and the turbine goes from standing still to full speed (sudden gust), making the voltage rise from zero to 400V DC. That value of 400V means 5800 Watt output according to the table, so it will take the inverter a full 5800/500 = 11.6 seconds to ramp up the output power to that level.

In general you want the inverter to follow the turbine as closely as possible; it keeps the turbine from overspeeding, and loads up the blades better (controlling the voltage/power translates to controlling the TSR of the turbine, and the closer it runs to optimal the more energy it will generate). So, we normally set this as high as it will go, up to 10,000 Watt/s in AuroraInstaller (this is rounded down to 9,9xx after saving it, but that doesn't matter).

"Tprot" is the time the inverter will stay switched on and connected to the grid after the voltage drops below Vstart. Setting this very short means the inverter is constantly dropping out, and has to re-handshake with the grid (takes a minute or so) when the wind is light and variable. Setting it very long means the inverter stays on a long time after the wind died down, using up around 40 Watt in the process to power the electronics. We normally set this to 3 to 5 minutes, or 180 to 300 seconds (it's stored in seconds).

Since you're messing around with AuroraInstaller: If you post the spec sheet of the turbine I'll make a better MPPT curve. It's not unusual for manufacturers that they do not understand how MPPT for wind turbines work (in fact, it's the norm, I've seen some weird curves). The (nearly) straight line that Fortis came up with isn't the worst, in fact, it probably works pretty decently (WindyBoy inverters all run a straight line as the MPPT 'curve'). Assuming they got the upper segment right, it means that the turbine is running faster than needed for the lower wind speeds, and you could make a little more energy at those low wind speeds with a better curve (with the turbine making less noise by spinning slower at the same time). You could try both and see what works better for you.

-RoB-

[Shaun Burgess]

hi rob i changed curve last nite . i think its better here a link to montana power output http://www.ason.ro/Fortis_product_overview.pdf thanks sb

[Rob Beckers]

Shaun, here is a proposed curve that I come up with when I plug the numbers. This includes 'following' the turbine through furling. The top-end is not that much different from the original, but the bottom-end is, and it may work a little better at getting energy out of low wind speeds. How well this works is something I don't know; I have to make assumptions, especially when it comes to voltage vs. RPM, but it's easy to give it a try.


Volt Watt Out
70 0
86 40
100 85
113 145
126 220
139 315
165 570
190 920
215 1400
261 2700
305 4000
345 5000
365 5400
383 5700
401 5800
420 6200


-RoB-

[Shaun Burgess]

brillant. what will i set vin start at . will get that in today thanks rob

[Rob Beckers]

Vstart = 70V

[Shaun Burgess]

hi rob power curve is working great alot better. the omron controller is working great had to conect to 14 on omron . . but am still having trouble with inverter staying powered up i checked resister across the dc in and am getting 100komhs its sits around 50vdc now . i also changed the time out for 300second in curve with no joy any ideas thanks shaun

[Rob Beckers]

Shaun, so Vstart is set to 70V, you measure just 50V on the input, and the inverter still will not switch off after the 300 seconds have expired? That's odd...

What's the exact type number of the Omron you're using; is this a K8AB-VW3 or K8AB-VS3? I'll change my diagram once I'm sure we got the right type.

-RoB-

[Shaun Burgess]

yes rob vstart is 70v. suppose it not the end of the world if it does not power off could i try 2 resisters on it .. i used a k8ab vs3 omron and a schneider gc4004m5 nc relay and paired up contacts . when powered up it uses around 3.1 watts think thats around 27units a year. thanks shaun