Wind Turbine power curve help

[Tony Thoreson]

Glad to be a new member.

I acquired my first wind turbine (4kw) and grid tie inverter and am looking for help on a wind curve. Pretty excited I have a lot of wind here in North Dakota.

I fell into a DTI Gale 6kw grid tie inverter. I have the software to program the inverter and have been trying to figure out how to program it. Beefy unit, but doesn't appear to be super user friendly to program.


It looks like I need to input "watts/DC voltage" and the wind curve from the turbine manufacturer is "watts/wind speed".


I have the following information

Wind speed (in m/s) outpower power (watts) DC240V

1 0
2 0
3 0
4 100
5 250
6 500
7 800
8 1100
9 1670
10 2200
11 2640
12 3100
13 3400
14 3600
15 3800
16 4100
17 4200
18 3900
19 3600
20 3200
21 3000
22 2700
23 2500
24 2300
25 2000


10.5 feet rotor diameter
3 blades
4000 rates power
400 r/min rated rotate speed
17 m/s rated wind speed
working voltage DC380V


Any help would be greatly appreciate. From what I have seen looking around, there is a lot of expertise here! Excited to soon be part of the wind turbine community!

[Rob Beckers]

Hi Tony,

Based on the parameters you listed, this should be an approximate MPPT curve:


Wind (m/s) RMP DC Volt Watt Out
3 72 81 0
3.5 84 94 0
4 95 107 17
4.5 107 120 41
5 119 132 71
6 143 156 149
7 167 180 259
8 191 203 403
9 215 225 587
10 239 247 815
11 263 268 1093
12 286 288 1424
13 310 308 1814
14 334 327 2267
15 358 345 2788
16 382 363 3381
17 406 380 4051
18 430 396 4802


However, the values you listed may be off. Your rated wind speed of 17 m/s is very high, usually turbines use around 11 m/s. Going by 17 m/s and just 4kW out, the efficiency is very low, barely 20% overall, and the TSR is also very low for a regular HAWT, just 4 (normally would be around 6).

So, take these numbers with a grain of salt. They could well be off since the values from the spec sheet sound fishy.

-RoB-

[Tony Thoreson]

thanks im sure it will need tweaking, but at least it will be a starting point.

[Ellen Thomas]

Hi,

I'm also new to the list and would be very grateful to get some help with a power curve.

I had a 10KW Redriven you can read about my sad story :sad2:on my Blog (https://smallwindy.blogspot.com)

Now I'm downsizing to a WHISPER 200 HV

I purchased it from Ethan Brush ( also on this forum) and he recommend this list.

Here is the info I have:


rated power 1000 watts at 11.6 m/s (26 mph)

( I Pulled these two points off a graphic on a brochure)
300 Watts at 7.5 mph
500 Watts at 15mph



start-up wind speed 3.1 m/s (7mph)
Voltage. 230V
 survival wind speed. 55m/s (120) 


Rotor Diameter. 2.7 m. ( 9ft)



I have 2 Aurora 6000s that currently have a MPPT for a 10KW wind turbine and are grid connected. I need to program the auroras for this new-to-me turbine.

I've got a dump load too. Will the Auroras divert the turbine to the dump load if the RPMs get too high?

The whisper 200 furls at high wind. Is there any other equipment I need to protect from overspeed? The Redriven had brakes and a yaw motor to keep it safe.

Thanks for any help you can provide.

Ellen

[Rob Beckers]

Hi Ellen,

Welcome to the forums!

A little Whisper on a 10kW Redriven tower... That should look interesting!

If I recall these turbines were meant for battery charging and had a transformer on the other end taking it down to battery Voltage, before going through a rectifier to charge the batteries. The power curve and behavior of a grid-tie turbine will very different from a battery charger though; when batteries are charged the Voltage is clamped to the battery Voltage, while a grid-tie turbine runs at the Voltage that produces the most power. That means the 230 Volt is probably nowhere near the actual Voltage at 11.6 m/s and 1kW out.

On the bright side, the turbine can produce much more power than 1kW at 11.6 m/s when it is used with an MPPT curve!

To make a power curve I'll need some more basic parameters/measurements from the alternator and turbine:

The resistance from phase to phase, in Ohm. So, with an Ohm meter (most multimeters can do this) measure between 2 of the 3 wires that come from the alternator. I'm assuming 3 wires come out, so it's a 3-phase alternator?

The RPM-to-Voltage ratio. This could be harder to measure. You'll have to find a way to spin up the alternator to an RPM that you can measure, and then measure the AC Voltage coming out from phase to phase (be careful, this could be a pretty high Voltage!). It doesn't have to be a high RPM for measuring, even 10 RPM is fine as long as you can accurately measure that RPM and Voltage.

To make this work with the Power-One Aurora inverter you will need a 3-phase rectifier to turn the AC coming from the alternator into DC. You will also have to provide good overspeed/over-Voltage protection for the inverter. At the same time you will likely need something to switch on the dump load when the grid falls away or the Voltage gets too high. The inverter doesn't provide any of this.

There is a schematic of over-Voltage protection with a means to switch on a dump load at my Web site: https://www.solacity.com/power-one-abb-aurora-solar-wind-inverters/ (scroll down to the bottom for the wind inverter files).

-RoB-

[QED Wind Power]

Hi all,
Ellen contacted me a while back to try and assist with their installation. I'm planning on using one of her ABB/Power One PVI-6000 Wind inverters with a custom MPPT.

Since the wind turbine is rated for 1000W and the PVI is able to load 6400W I think I can safely use the PVI's loading as a regulator with a safety 3PH NCC in parallel with PVI to engage and shunt the 3PH in the case of the inverter disconnecting.

One big piece to the puzzle is knowing what the voltage off the generator is when the system is at rated power. Depending on how low that voltage is will determine if there is enough headroom to safely keep the PVI-6000 well below 600V (preferably below 500V).

Otherwise I'm going to need to include a voltage divider circuit coupled with a small PLC to engage their dump load actively if the turbine needs load assist prior to furling.

If anyone has contacts of info that might point me toward a V vs W it would greatly help me!

[Rob Beckers]

QED, it should be no problem to use a 6kW Aurora inverter with the Whisper. To make a decent MPPT table I will need those parameters as listed in my previous post though.

There's nothing 'safe' in the inverter being 6kW while the turbine is just 1kW; it's the Voltage that kills the inverter. The moment it goes over 600V DC the magic smoke goes out and that's the end of the inverter. The challenge is therefore to make absolutely 100% sure that the inverter is protected.

To illustrate this, I've had a customer with a 25kW (Chinese) wind turbine and 5 Power-One Aurora 6kW inverters connected in parallel. All of those inverters went up in smoke within 1 minute of switching on the turbine. The customer was certain the turbine could not overspeed or produce more than 600V. I had warned him beforehand...

-RoB-

[QED Wind Power]

Rob,
Thank for the response. I'm 100% familiar with all the nuances of the PVI-6000 models having worked with about a thousand of them. The 600V number is very understood.

I'm looking for a Volt v Watts matrix for the small turbine they have purchased so that I can design the mppt for them. If you can help me obtain that, it would be great.
Scott

[Rob Beckers]

Hi QED,

Unless someone else already made an MPPT curve for a Whisper 200HV there is none (yet). This was originally a battery charging turbine, that's now being put to use for grid-tie. That's a very different situation and the numbers from the brochure no longer apply.

As I wrote before, I'll need the phase-to-phase resistance of the alternator and the RPM-to-Voltage ratio to calculate the numbers for Voltage vs. Watt at various wind speeds.

-RoB-

[Ellen Thomas]

We were able to get some RPMs and Voltages this weekend

Is the resistance measure by just measuring the ohm between two of the three wires with the turbine at rest?

Here are the points we could get with our 10 dollar ebay tachometer and volt meter. Do they seem believable?:unsure:

RPM Voltage
36 14
68 30
88 40
106 49
144 70
183 90
201 100
228 110

Thanks for any advice you can provide.

Ellen

[Rob Beckers]

Ellen, I can't tell if they're accurate, but the numbers look good from the perspective that Voltage vs. RPM is linear: Twice the RPM should be twice the (unloaded) Voltage, and your numbers bear that out. So that's good!

Regarding resistance, yes, just measure between two of the three wires. They should all be equal (i.e. regardless which two alternator wires you use), though you may want to verify that they indeed are. If anything is wrong with the alternator windings it would show in those resistance measurements.

-RoB-

[Ellen Thomas]

Good news the resistance between each of the leads is the same 39.7 ohms

With that info, can you make a curve?

Thanks,
Ellen

[Rob Beckers]

Hi Ellen,

That is a pretty high resistance for the alternator! The only way to get decent power out of such an alternator is to spin it pretty fast, which means the blades have to spin pretty fast compared to the wind speed. That keeps the Voltage up, current low, and losses therefore reasonable.

The table below is calculated for a TSR (Tip-Speed-Ratio) of 9, which is pretty high for a turbine! It is the ratio between the tips of the blades and the wind speed, so with this the tips will move at 9 x 11 = 99 m/s (= 356 km/hr = 221 mph!) when the wind blows at 11 m/s. It's bound to be noisy at that speed!

Most wind turbines have a TSR of 5 through 7, so this is faster than usual. Then again, Southwest Wind Power had a tradition of high-TSR and quite noisy turbines. I don't know (and couldn't find any info) what the official TSR is supposed to be for a Whisper 200, so this may be off.

I'll explain below what the values in this table represent.


Wind (m/s) RPM Heat (W) Eff. (%) Idc(A) DC (V) P (W)
5 316 22 86% 0.5 173 95
6 379 45 84% 0.9 201 184
7 442 83 81% 1.3 226 302
8 506 140 79% 1.8 249 451
9 569 221 76% 2.3 270 633
10 632 333 74% 2.9 288 849
11 695 483 71% 3.6 305 1098
12 758 679 69% 4.3 319 1379
13 822 927 66% 5.1 332 1693
14 885 1238 64% 5.9 342 2036
15 948 1620 61% 6.9 351 2407
16 1011 2084 59% 7.8 357 2803
17 1074 2640 57% 8.9 362 3219
18 1138 3299 54% 10.0 365 3652


The first column is wind speed, should be obvious. You can pretty much ignore the values above 12 m/s. The turbine should be furling at this point, and in fact, you probably don't even want to use the 12 m/s value either, capping it at 11 m/s.

Second column is the RPM, as calculated from the diameter and TSR. As you can see it's whipping along pretty good at 11 m/s!

The "Heat" column is how much heat is produced and dissipated by the alternator. There is a limit how much it can handle (even if the wind cools it down), and at 11 m/s with nearly 500 Watt in heat it will get very toasty in there! At some point insulation melts and things go wrong in a big way. The heat is calculated from the current in the windings and the resistance.

The "Efficiency" column lists the alternator efficiency, how much energy it puts out vs. what's going up in heat. That is the reason I would cap the MPPT table at 11 m/s. The alternator should be able to do 71% efficiency, but I'm not sure once things dip below that and heat numbers rise quickly.

The "Idc" column is the DC current coming from the alternator.

Next is "DC (V)", the DC Voltage after rectifying it (under load), this is what is used with the MPPT table.

The last column is output power "P (W)" in Watt, coming from the inverter. This too is what's used with the MPPT table.

So, your MPPT table would be those Voltage - Watt pairs of the last two columns, and I would let 11 m/s be the last value to be used. So, 1100 Watt is the maximum coming out of the inverter, even if the turbine spins faster.

The first point for the MPPT table would be 130 Volt and 0 Watt output. That happens around 3.5 m/s. This gives the turbine a chance to spin up, and the inverter time to switch on.

In short, this would be the complete MPPT table:


DC (V) P (W)
130 0
175 95
200 190
225 300
250 450
270 640
290 850
305 1100

Pout Ramp = 3000 W/s
Vin Start = 130 Volt
Tprot = 180 seconds
Vgrid Nom = 245 Volt


Those last 4 values are numbers also programmed into the inverter with the AuroraInstaller program. You'll see them once you open up that screen on the computer.

Hope this helps!

-RoB-

[Ellen Thomas]

Rob,
Thanks so much for all of your calculations.
Our old Redriven wind turbine was noisy too. It sounded like a large plane was landing in our yard on a windy day. The good news is we don't have any neighbors close enough to hear it. I bet this one will sound like a smaller plane buzzing us.
I can't wait to hear it!

Several local officials have pledged that our wind permit would be the last one ever in the area, so it is our duty to getting working again!

Ellen

[Rob Beckers]

Ellen, please let us know how it ends, and post back once it's up & running! Pictures would be good too.

-RoB-

[Ellen Thomas]

Rob,

Thank you so much for your help with the south west whisper 200 power curve. we have the south west now on the top of my ReDriven hydraulic tower and it is spinning away. As you predicted, the tower is over powering but at least it is not wasted just sitting there any more.


https://2.bp.blogspot.com/-TKiWTgIYPnI/XCakDTjEkdI/AAAAAAAAAYo/QMJGdKjILpw4AJ95XDfhp5wN7V5YktdFgCLcBGAs/s1600/swOnTower.jpg

I've got a blog that journaled all my trial and tribulations with the Redriven and now with the South West. Luckily there is much less drama so far with the South West.
http://smallwindy.blogspot.com