Fronius/Sanyo/SMA compatability problems?

[FB.]

Here’s my take on this:

12x 250W Sanyo panels in one string.

Sun comes up. One panel is shaded by the chimney, so its bypass diodes/circuits are active, with only eleven panels actually functioning. This would be especially true if installers had not appreciated the way the bypass diodes are laid out on a given panel.
Inverter tracks up and down the voltages on startup andfinds the optimum for the 11 unshaded panels – the optimum (Vmp) being about 34Volts.
11 panels at 34Volts, in one string, gives 374V.
The inverter sets up for harvesting at 374V and the system then happily hums along at 374V, with minor checks a few volts either side, tosee if there’s a slightly better voltage to extract maximum power.
Then a second panel also gets shaded by the moving shadow ofthe chimney, so we have two shaded panels. The inverter then tries to run the remaining ten panels at 374V. This bumps up each panel’s voltage to 37.4V,dropping off the end of the voltage: efficiency curve, resulting in inferior efficicency.

 

[FB.]

Moral of the story:

Set up the inverter to occasionally track a much wider range of voltages at various times in the day (or perhaps get the inverter to check a wide range of voltages if the inverter's kW output drops sharply).

Avoid installing shaded panels.
- or -
Wire panels in two strings, so that potentially shaded panels are in one string and those which will never be shaded are in a separate string.
- or -
Use larger strings of lower-voltage panels (e.g. 15x30V rather than 12x37V)
- or -
Install 20x175W panels instead of 14x250W, so that a single panel (or two) has less influence on the whole string, therefore less movement off the optimum voltage.

 

[nothappy]

FB,

Thank you.

I am waiting to see if Fronius has the software upgrade to track to wider voltage range as you suggested. I should have an answer by tomorrow.

What we are actually getting later on in the day is 3 partially shaded panels and turning the system off/on now makes sense. Later on in the afternoon we move from shading on 3 panels down to 2 so would this have the same effect?

The installers used measurements of the chimney, pitch of the roof and computer software to set up the most efficient system. The software, to my knowledge, did not expect this shading to be a problem.

As mentioned earlier, we did have this problem with our original SMA inverter but that was swapped for the Fronius when we identified that this was happening. Our original SMA did not have optitrac.

John

 

[Gavin A]

FB - coming up with that diagnosis after the pictures have been posted up is cheating...

but yes, that's about right I think.

 

[nothappy]

A resolution

Fronius have offered a full refund on the inverter as they do not have the software to update the existing one and deal with the voltage changes due to shading.

A new SMA with optitrac is being fitted tomorrow.

Many thanks to all who have contributed on my thread - your comments have been a great help.

I will give the new system a few days and report back on any issues. Hopefully it will be good news.

John

 

[topcat1]

Hi, I have similar problem with 14 Sanyo panels and Fronius IG-TL3.0 Inverter single string. Roof Central Heating flue causes shading morning and afternoon. Output drops dramtically when shade from flu goes over one panel. Comes up again after an hour or so. If system shut down full expected power restored. Fronius not interested saying overall output is good. Look forwar to hearing results with different Inverter.

 

[nothappy]

So far the results have been very good. We have had a few days of constant sunshine and with the Fronius inverter we would have had to shut the system down 2 or 3 times. With this SMA inverter with Optitrac we haven't had to do it once.

I understand that the output may be good but it's not good enough as it's obvious that more power is available.

I am not in this trade, I am just a customer who has a bit of knowledge of electronics (City & Guilds) so I have been able to monitor my system and keep in touch with the installers to let them know how the system is performing.

John

 

[topcat1]

So far the results have been very good. We have had a few days of constant sunshine and with the Fronius inverter we would have had to shut the system down 2 or 3 times. With this SMA inverter with Optitrac we haven't had to do it once.

I understand that the output may be good but it's not good enough as it's obvious that more power is available.

I am not in this trade, I am just a customer who has a bit of knowledge of electronics (City & Guilds) so I have been able to monitor my system and keep in touch with the installers to let them know how the system is performing.

John

Hi, thanks for the info. I'm in the same situation as you little knowlwedge but hopefully some common sense and logic. Hope to receive more info from you on performance.

 

[nothappy]

Was your system installed by a company? They should be your first port of call for any problems.

I believe that this shading issue is more widespread than you think but, unless you monitor your system, you'll probably never notice as long as the number on your meter keeps going up.

Regarding performance issues, my system is performing well so I probably won't be posting more information unless it's bad news.

John

 

[topcat1]

Was your system installed by a company? They should be your first port of call for any problems.

I believe that this shading issue is more widespread than you think but, unless you monitor your system, you'll probably never notice as long as the number on your meter keeps going up.

Regarding performance issues, my system is performing well so I probably won't be posting more information unless it's bad news.

John

Yes it was installed a company who are doing the best they can - Fronius not giving any advice. Hope your system continues to perform well. Thanks

 

[Energetic]

Righto, my last word on this (i sincerely hope). I'll post it in both threads so subscribers to both will see it.

After some great advice from member of this forum and some further digging with Sanyo, SMA and Fronuis we have been able to close this issue off.

As has been suggested by members here the large instantaneous drop in voltage caused by the operation of the by-pass diode on the Sanyo H-Series panel drops the array voltage outside the MPP trackers scanning range causing it to get stuck on a false peak. Its is particularly problematic with the H-series due to the large number of cells in the two end sections. See image:

View attachment 11808

I have been told that SMA's opti-trac was developed as a direct result of this known issue with their tracker. It is worth noting that this information did not come from SMA, they denied all along that the problem was anything to do with their product, they did not advise us to try optitrac when it became available and as far as i know did not release any info publicly in response to a problem that was being reported several time a day at its peak.

Fronuis were unable to offer an update similar to optitrac as they have not had the problem frequently enough to warrant it. We have now installed the third 3000HF, this time with opti-trac and the problem has been resolved.

I must be clear that this is not a fault with the panels or inverters as such, they work as they are designed to. The problem is one of compatibility, a specific panel, inverter and shade combination is the cause and removing any one of the three will resolve the issue. Opti-trac rescans at set intervals and therefor doesn't allow the tracking of a false peak.

I'm glad to have this resolved finally and would like to thank everyone of the forum who offered advice and also SMA, Fronuis and Sanyo for taking it seriously and coming up with some answers.

Finally i would advise anyone with H series panels and hard shading to monitor their system closely, part shading doesn't automatically mean poor performance and we have seen the system perform at near peak with the shading when the tracker is working correctly.

If you are considering PV and you have a shading issue get a quote from an installer who uses PV-Sol or equivalent who can model the system and quantify the imact the shading will have. I do wonder how many other systems are out there with this issue that has yet to be noticed.

Over and out...

 

[Gavin A]

So far the results have been very good. We have had a few days of constant sunshine and with the Fronius inverter we would have had to shut the system down 2 or 3 times. With this SMA inverter with Optitrac we haven't had to do it once.

I understand that the output may be good but it's not good enough as it's obvious that more power is available.

I am not in this trade, I am just a customer who has a bit of knowledge of electronics (City & Guilds) so I have been able to monitor my system and keep in touch with the installers to let them know how the system is performing.

John

Hi John,

just wondering if you could take some pictures and output readings at similar times next time it's sunny for a before and after comparison?

 

[danesol]

So ... is this issue only present with somekind of partial moving shade on panels ??

 

[nothappy]

Gavin,

So far I have not taken any output readings because I have not had any problems. The alarm bells went off before when we started to see a steady drop in power during certian times of the day (as per photos). We would see a drop from 1.5kw to 250w over a period of about half an hour but this was only confirmed by looking at the Fronius software. We have not had any drop in output power, even with the same shading and on bright sunny days we have not had to turn the system off/on to reset.

What we have avoided with Optitrac is the drop off and we have maintained the same 1.5kw which we would have previously lost.

I am quite confident now that, like most other customers, we can forget about close monitoring and just keep an eye on it from time to time. I suppose we could turn Optitrac off and see what happens on a sunny day..............................then again maybe not!!!

Danesol,

Yes, for us this problem was caused by partial slow moving shading over 2/3 panels,

John

 

[mdovey]

Does this issue occur on the SB 1200/1700/2500/3000 inverters or is it just a problem with the HF (and TL?) ranges?