Scirocco MPPT settings

[Tom Dixon]

Hi,

I've recently brought a Scirocco back online after it was out of action for over a year due to various issues. I've had a stab at programming the MPPT table of it's Aurora 6kW inverter from some maths and a bit of trial/error.

I was wondering whether anyone has any suggestions for this? I'm particularly out of my depth on the parameters such as Vout Ramp etc.

It's currently working - in that it is making around 40kWh on a good day - but I'm nervous that I'm loading it incorrectly and causing both loss of output and potentially unecassy vibrations. There are quite a few growls at various RPMs which make me think somethings not right.

Many thanks,

Tom

[Rob Beckers]

Hi Tom,

This is the latest curve for the Scirocco:


Data # F (Hz) P (W)

1 22 0
2 25 200
3 30 600
4 34 1300
5 38 2600
6 40 3600
7 43 5200
8 45 6050
9 60 6100


MPPT mode : frequency

Pout Ramp : 5000 W/s
Vin Start : 100 V
UV Tprot : 180 s
Vgrid Nom : 245 V



I don't know where you are located; if in Europe that Voltage for the grid would be 230V, the value listed is for North America.

Let me know if you have any more questions. I've programmed quite a few inverters for this turbine.

-RoB-

[Tom Dixon]

Hi Rob,

That's amazing, thank you very much.

Unfortunately I tried it and it doesn't look like the frequency counter is working - those figures yielded a very disappointing output - do I perhaps have to wait for it - I waited over a minute and it just seemed to be stalling the machine.

I don't suppose you've worked out the V/Hz relationship? Is it linear?

Is it significant that the turbine is roughly 200m away from the inverter (with 10mm diameter conductors for each of the 3 phases)?

We're in the Scottish borders - it's blowing really hard tonight so I'm seeing between 4800 and 6100 with gusts - this is with my guessed numbers for the table combined with your other parameters.

Once again thanks for your help so far!

Tom

[Rob Beckers]

Tom, did you switch over to "Frequency vs. Power" for the MPPT curve? The default is "Voltage vs. Power" in the AuroraInstaller settings, it's a radio button right under the table that holds the MPPT values.

The next one to look at would be if the inverter is receiving the frequency signal from the PVI-Wind-Interface box (you should have two frequency wires connecting the two).

-RoB-

[Tom Dixon]

Hi,

I had to switch the radio button over in order to input frequency data into the table - so yes, it was switched. It doesn't look like the inverter is getting frequency data. There's a cable linking the "turbine speed" terminals in the power-one "wind interface box" with the "wind" terminals (near to the rs485 sockets) in the inverter. There's a switch called inputmode which is currently set to "par" (other option is ind)

I've not even got a multimeter out here let alone a scope so I've no way of checking what it's doing (unless I can use my laptops soundcard input safely?!?)

Due to be quite windy tomorrow so I'll have a chance to edit the table again - dead calm today so not able to have a play.

Thanks again,

Tom

[Rob Beckers]

Hmmmm... That MPPT curve is the correct one (direct from Eoltec). Trying other numbers isn't going to fix it. I'm sure you already tried this but just in case: Read in the values from the inverter into AuroraInstaller, to make sure they were actually stored in the inverter. I've once or twice had it not save settings despite pressing the 'send' button.

The polarity of the frequency signal wires matters. There is a (+) and (-) next to the terminals on both sides; the positives on both sides need to be connected, as well as negative to negative.

It would be hard to figure out with a multimeter if the signal is working or not. You'd need an oscilloscope for that. The voltage on the terminals shouldn't be very high (it hooks up to the output of an opto-coupler in the wind box).

Just to make sure; check that all three phase wires coming from the turbine actually produce voltage, and all three have current flowing when the turbine is producing power (a multimeter with a current clamp would be handy for that). The frequency signal is made from phase 1 and phase 2 of the wind box input, if either one of those is not connected you wouldn't get a signal.

Thinking this over, your turbine is producing energy. Without a frequency signal the inverter output would be exactly zero at all times, if it's using frequency vs. power for MPPT. So, in all likelihood the signal is working fine. You wouldn't have an anemometer on the tower to measure wind speed? That would tell if the turbine output is out of line with the wind speeds that it's seeing. Checking all three phases for output would be a good thing to do too.

-RoB-

[Andy Rhody]

Forgive me but what do you guys mean by "frenquency" in the MPPT table? Is that something used instead of "RPM's"?

Andy R, Aurora wind guy.

[Tom Dixon]

Andy - yes, there's the option of using either V vs W or Hz vs W to set the MPPT table.

Rob,

The installer software is warning of "low Freq" and reading zero so I guess it's not getting the signal.

I don't have a clamp meter with me so cant do current readings, all three have the same voltage between them.
If I was missing a phase would it be possible to get to 6100W? the big winds that came through the other day were holding it up above 6kW for prolonged periods.

I'll have a go at checking the terminal connetions I guess (polarity is correct)and then consider replacing the octocoupler? Do you know anything about that switch in the inverter? I might also try swapping phases around to see if there's a combination that does create a frequency.

The output when using frequency vs power are always very low (around 15W) which I suspect is just the capacitors discharging?

For completeness here are my voltage numbers - they're currently giving good output results and no vibrations of concern...



Cheers

data V W
1 100 0
2 125 170
3 150 500
4 200 1500
5 220 2600
6 240 3600
7 260 5200
8 280 6050
9 300 6100


MPPT mode : frequency

Pout Ramp : 5000 W/s
Vin Start : 100 V
UV Tprot : 180 s
Vgrid Nom : 230 V

[Rob Beckers]

Tom, I'm not quite following: Your table says "MPPT mode: frequency" but your table has voltage vs. power values in it. I assume you've been running in voltage mode with those values? That would explain the output power; without a frequency signal the output would be zero at all times.

Not sure how electronics savvy you are, but if you send me an E-mail I'll return a copy of the schematic diagram of the wind box, so you can see how that works.

Voltage vs. power is not quite as precise as frequency, and this matters for the higher output values where the turbine is close to activating the flyweights to repitch the blades to stall. If you want to run voltage mode, this is a table that is close to the frequency values:


Pout (W) Vdc (Volt)
0 135
150 149
350 163
850 192
1600 227
2500 256
3600 284
4500 302
5400 316
6100 327


This was derived from a slightly older version of the frequency MPPT table, I've not done it for the latest version, but it should be close enough.

-RoB-

[Tom Dixon]

Yes, sorry, those figures are running in voltage mode - I just copied your table from your first post and forgot to change that!

I'll run on your suggested voltages and see what happens!

Cheers,

Tom