Fronius/Sanyo/SMA compatability problems?

[Gavin A]

hi, if you prefer you can email them to me direct to info at Leeds-Solar.co.uk and I'll upload them. It'd also help me to have some better resolution images than you tend to be able to upload so I can zoom on on the shading etc.

If anyone else has an pictures and / or data they'd be prepared to email to me as well, I'd be quite interested in investigating this a bit further to see if we can nail the problem and solve it - I'm expecting to have a little time on my hands in April. We've also got a couple of web box's currently on loan at a couple of sites that could be used for monitoring purposes with SMA inverters, and to allow me to remotely monitor the systems and adjust the settings etc.

Happy to discuss this with fronius to see if there is any method of extending the range of the MPPT tracking system or something similar as well.

There are a couple of other possibilities that could be causing this, but I'm hoping it is as I described above as that ought to be fairly simple to solve now that optitrac is available (I have the firmware upgrade for HF inverters if anyone needs it), plus maybe extra care being taken around designing around shading with Sanyo panels.

 

[FB.]

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.

On the following topic > link here < I said:

"....Perhaps it is occurring because quite a lot of inverters - even different makes - are using the same programming algorithm to run the (M)PPT? Perhaps the MPPT has not been properly tested in a part-shaded situation...."

 

[yoz7241]

Fronius ig tl wat??? there should be an error code!!! the country setting one is error code 102 i think, grid voltage to high!!! but the inverter usally works between 220 and 270!! To reset country setting you need to ring fronius and they will give you the codes and walk you thou it!!!
But if you can tell me your error code, because it must have one i might be able to help, ive fitted tons of the fronius range and hardly get any problems, sometimes they sort them selves out!!!

 

[liquidity]

there's another thread on here about this issue.

I'm fairly sure I know what it is, but would need some photo's of the array taken at the time the problem occurs to confirm it.

Basically I believe this is a problem relating to shading of the panels, and the inverters MPPT's inability to cope with the rapid change in the peak point on the votage curve, which causes a more rapid drop in the MPP with sanyos than other panels when the bypass diodes ought to be kicking in, due to the individual voltage of each string in the panels being higher (or to be more precise, in the H series panels the 2 strings of cells on either end of the panel are significantly higher voltage than the middle string).

The problem is likely exacerbated because the Sanyo H series panels have the bypass diodes / strings running across the long side of the panel, not the short side as virtually all other panels do, so your installer may not have appreciated this when installing the system.

The reason this happens in peak sunlight is that that is when the shading is the hardest / difference between shaded and unshaded cells is highest.

the reason it sorts itself out when the inverter is switched off and on is that at this point the inverter MPPT system traverses the entire voltage range to check where the actual MPP is on the voltage curve, instead of getting stuck on a false peak. This is also the reason that the optitrac global peak function on the SMA inverters has been shown to sort this issue out, as it makes the inverter regularly track up and down the full voltage curve to check for other higher peak points every few minutes, instead of just searching around the local voltage peak it's sat at.

Sorry, I don't know if fronius have anything similar to the optitrac global peak function.

I wonder if this can be simulated/repeated by sliding a large sheet of cardboard across the array?

 

[FB.]

I wonder if this can be simulated/repeated by sliding a large sheet of cardboard across the array?

Or find an array without any shading and then experiment with fixing a pole to cast some shadow, with the shadow moving at a natural (very slow) rate as the sun moves across the sky.

 

[nothappy]

A simulation might work but you would have to be patient. There's no way I could do it without scaffolding but I can be fairly confident that on a cloud free bright day it would happen anyway.

There were no error codes on the inverter after that last failure/shut down.

 

[nothappy]

Still going on I'm afraid, sometimes twice a day. There doesn't seem to be anyone who can give an answer to my problem which seems to be caused just by a bit of shading.

There must be other systems out there with similar shading. Maybe it's just that I keep an eye on it and have spotted something that others have missed.

I am amazed that huge companies like Sanyo and Fronius haven't come up with a solution to this problem which I don't believe is just happening to me. One correction from earlier, my panels are laid out in portrait (upright) not landscape (longways).

WHY DOES MY SYSTEM SLOWLY FAIL AND THEN SUDDENLY WORK PROPERLY IF I TURN IT OFF AND ON AGAIN???

I am beginning to wish I hadn't bothered with the system at all and I tell anyone who will listen that PV has hidden problems that you should be speaking to your installers about before parting with your money. If this was any other product that you had spent £1000's on you would expect it to perform.

Any advice on my next step would be gratefully recieved. PM me if your advice isn't something that you want to be aired publically,

John

 

[Gavin A]

Hi John,

Sorry I didn't reply to your email, but I'm 99.99% certain that your problem is as I described it earlier as it occurs when the chimney moves from shading just one string on one panel to shading 1 strong on 3 panels pretty much at the same time, which would be a virtually instantaneous change in the MPP of something like 26V.

It's a situation that would be resolved automatically on the Sunnyboy inverters through the use of the optitrac global peak software. Or more accurately it would still exist, but only for at most 6 minutes at a time before the software kicked in and found the new MPP point again.

I don't know if such a feature exists on the Fronius inverters, but at least you can now ask them directly if they have any function similar to the optitrac global peak, or the ability to widen the range on the standard MPPT tracking system so it scans further up and down the voltage range from it's current peak.

I've hopefully attached your document so others can see what I mean.

 

[nothappy]

Gavin,

Thank you very much for the time you spent on this. The document attachment works fine.

I believe that the installers of my system are trying to speak to Fronius and obtain an upgrade, just as you stated. If there is no upgrade then I don't know what will happen.

It seems to me that Fronius are behind the times with their inverter if SMA have already solved what seems to be a recognised problem. If there wasn't a problem then surely SMA wouldn't have written the Optitrack upgrade?

I am hoping to hear some good news tomorrow - I will let everyone know the response from Fronius.

John

 

[jupestar]

Hi, this is surely a shading issue as Gavin has stated. Regarding other people having the same problem - i'm sure they do but probably don't monitor it quite as closely. what i would be interested in knowing is without user intervention how long does it take for the system to correct itself. and if you are meeting sap estimates without user intervention. SMA optitrac will do doubt cure this quicker than most inverters as my understanding is it will continually search for the global optimal solution, rather than the local. regarding the photo that gavin uploaded, i would consider this to be significant shading on a string system.

 

[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