Fronius/Sanyo/SMA compatability problems?

[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?

 

[Energetic]

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

I would be amazed if the SBXXXX series has a more sophisticated tracker than the HF range...

 

[Energetic]

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

Our experience is that this is hard shading such as a chimney in our case shading not more than a third of ONE panel but moving throughoutt the day causing the operation of the diode. The inverter 'sees' a step change in voltage as the diode reverse biases but to the human eye it looks like a very slow moving bit of shading...

 

[mdovey]

I would be amazed if the SBXXXX series has a more sophisticated tracker than the HF range...

Quite the opposite - it may be that the problem is because the tracker in the HF range is too sophisticated. I'm not an expert here, but I could quite see how a less sophisticated tracker might take a longer time to scan for peak movements, or is less precise in voltage measurements (and hence be looking at a broader voltage range for the peak), and the issue with Sanyo panels would not show up.

SMA tell me that the SB1200/1700/2500/3000 hardware is not compatible with optitrac so there will not be a firmware upgrade to support it (of course the firmware upgrade process on these inverters is more complicated than on the HF range).

 

[Energetic]

Quite the opposite - it may be that the problem is because the tracker in the HF range is too sophisticated. I'm not an expert here, but I could quite see how a less sophisticated tracker might take a longer time to scan for peak movements, or is less precise in voltage measurements (and hence be looking at a broader voltage range for the peak), and the issue with Sanyo panels would not show up.

SMA tell me that the SB1200/1700/2500/3000 hardware is not compatible with optitrac so there will not be a firmware upgrade to support it (of course the firmware upgrade process on these inverters is more complicated than on the HF range).

Hadn't considered that, quite possibly. One of the things we turned up it that the MPPT's SMA use were developed for wind turbines originally and then modified for solar, i guess it's possible that higher voltage fluctuations in turbines required a wider voltage scanning range which was trimmed for the HF range. I'm no expert either...

 

[ChasT]

I have a 3KW system which I have been having problems with since installation. Originally I had an SMA inverter but the problems were still the same.

The system works well in general but there are occasions when the system power will decrease over a period of time (30-45mins) in bright and sunny conditions. When I spot this occuring I have to shut the system down for a couple of minutes. When the system boots up again the output is good. The difference can be from 250w before shutdown to 2KW afterwards.

There is sometimes shading on the panels and I accept that there will be a drop in output because of shading but the shading is still in the same place after the system has booted up again so how can that be a problem, especially after only a couple of minutes?

I have contacted the installers who have been very helpful but I gather that Fronius and Sharp are not being very helpful. Whatever theories that people come up with all sound very reasonable until you add the arguement 'but why does the system suddenly work well after I turn it off and on again'.

Any help would be gratefully recieved.

I have pretty much the same problem. On a day of continuous, uninterrupted sunshine my Fronius will spend about 2 hours shutting down and will then suddenly reboot. The shutdown seems to start when the shadows reach a certain point but I haven't cracked what's the trigger for the reboot. Any passing cloud or turning off the panels will force a reboot. I got a smoke screen from Fronius, but I guess the mpp tracking software isn't up to the job.
If these things are liable to misfire in shaded conditions I feel we should have been warned. Were you? Let me know how you get one because I'm not too happy about being told that the only solution is to remove my chimney

ChaT

 

[Energetic]

Sounds like it's possible, what panels, how many and which fronius inverter?

 

[ChasT]

TL jnverter with 14 Sharpe 250s. Fronius' view is that the problem can only be fixed by removing the chimney.................
I still can't believe that a computer can spend 2.5 hours shutting itself down from 2.5 kw to 250 watt, without there being some check in the code to identify this.
ChasT

 

[Earthstore]

Change the inverter for an SMA and switch on the optitrac, that should cure your problem.

 

[Energetic]

Fronuis are developing their new range and so will not be doing any updates for the TL's. Optitrac may be the only way out of it. We managed to get fronius to take their inverter back so we could get an sma. PM me if you want details.