Fronius MPP Hunting

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Comments

  • a0128958
    a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Fronius MPP Hunting
    rsl360 wrote: »
    ... Recording data at a two second interval shows this well....

    Can you show us this in chart or graph form?

    Best regards,

    Bill
  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    Re: Fronius MPP Hunting
    rsl360 wrote: »
    Hmm, maybe I should have started a new thread. I posted on this thread because I have the same problem as the original poster and wanted to continue the discussion of what seems to be a flaw in at least one model of Fronius inverter. I'd like to be able to say that Fronius fixed it, but that does not seem to be the case.

    To solarvic: I'm not in Phoenix, that's the original poster. And it any case, it's not a hot weather issue, the hunting occurs in very cold or moderate weather. Not sure about hot weather.
    I think both of you guys have the same problem of running too low of voltage. It would be nice if you said whar part of the country you are inso we could try to figure tempatures, But in my area I wouldn, run that small of a string of panels. Voltage is too low. AT 110F you only get 15.3 v per panel. That is only 183.6 at 100 sun. All 24 panels in 1 string would only be 367.2 v.
    In my area @-26f I could still run 18 modules and would. I would think Fronuis would catch it that them inverters don,t work well at such a low voltage you guys want to run them at. S:Dlarvic
  • rsl360
    rsl360 Registered Users Posts: 14 ✭✭
    Re: Fronius MPP Hunting

    My location is on Cape Cod, Massachusetts. The hottest weather we are going to see is about 100f, coldest is about -15f

    The setup of 2x12 panels is within the recommendations of Evergreen for the Fronius inverter. It is also within the recommendations of Fronius with for the Evergreen panels. I don't see that low voltage is an issue. And it's neither hot nor cold here at this time, so I don't see what it would have to do with hunting.

    I'll put some images in, but I see that I have to have them hosted somewhere.

    Originally posted by windsun
    My "authority" is the simple fact that if you have two or more strings, you can have two different MPP's if the strings are not matched. In some cases the inverter will try to pick the best overall point, but some will settle on the highest peak.
    Yes, absolutely true. The inverter might pick the wrong peak, yes. But that's not hunting.

    Before we get too far off track: My issue is that the system was/is hunting. Fronius agreed that this was the case, there was no dispute. They did not say I have too few panels, or that it's too hot or too cold. The new inverter does the same thing. So, is the Fronius MPP algorithm faulty? Perhaps there is nothing wrong with the inverter, but Fronius is unable to diagnose a system problem properly? (I say that facetiously, as it seems unlikely)

    rsl
  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    Re: Fronius MPP Hunting

    I have to admit that given your conditions and setup, it is something I have not seen before. The few instances I have heard of it you have eliminated.

    There are not many possibilities left, aside from a 2nd bad inverter - I assume you checked the Fronius site for any software upgrades?

    What is left to look for might be out in left field - birds sitting on the panels, a loose wire connection, voodoo.... :confused:

    One more remote possible is wind - which would cool the panels temporarily, but I have never seen that happen anyplace but hot zones.
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    Your correct, 12 panels is fine, for some reason I thought I read 10, but can see that's not the case.

    If this system was installed by a contractor, I'd insist they install different manufactures inverter. Xantrex and SMA are both well vetted designs
  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    Re: Fronius MPP Hunting

    Not sure I would recommend the Xantrex right now - they are backordered 8-16 weeks for most models.
  • rsl360
    rsl360 Registered Users Posts: 14 ✭✭
    Re: Fronius MPP Hunting

    Lets see if I can get some pictures of my system performance up here.

    This is a day of normal performance from the "new" (replacement) inverter. The green line is voltage*10 and the red line is the AC output of the system, in watts. The numbers on the bottom are a form of decimal date and time. (makes plotting easier) (click on the image for a larger view. I think you will then have to click on it again to get the full view)
    th_solar-normal.jpg

    This image is the system hunting for the first part of the day, then it stops on it's own. This is also from the replacement inverter. Again, green is array voltage*10, red is AC output in watts. I'd estimate that I'm losing over 10% of my output when this is happening.
    th_solar-hunting.jpg

    This is a detail of the prior image. The tick marks are at about 2 second intervals. Thus you can see that the hunting period is about 45 seconds.
    th_solar-hunting-detail.jpg
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    Thanks for the graphs ...

    Looks to me like your problem days are when its colder and the vmp is higher, its right at or just above the switch point in the inverter. Fronius has a very odd design that in order to get a larger operational range they have internally a multi-tap transformer and switch it based on the input voltage. On the IG2000/3000 is recall it was about ~200V and ~250V ( this is from memory of testing 6 years ago )

    On the day you have a good harvest, notice the voltage is about 20-30V lower than the problem day. I would say the inverter on the colder day, switches to a different tap in the early morning and as the temperature rises, then unit is either switch the tap causing efficiency changes confusing the tracking or the software is struggling between the hysteresis or vmp ( mppt ) algorithms.

    This is definitely the inverter and has been seen before. Likely as the temperatures warm up towards summer you will not see this issue.

    Two things you can do for proof,

    First when its ramping / mis-tracking, listen for audible clicks ( relays switching the transformer winding )

    Second, pull one panel out of each string ( lower the voltage of the string ), the unit will not be near a transition point, which is likely the root cause of the hunting
  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    Re: Fronius MPP Hunting

    Looks to me like your problem days are when its colder and the vmp is higher, its right at or just above the switch point in the inverter. Fronius has a very odd design that in order to get a larger operational range they have internally a multi-tap transformer and switch it based on the input voltage. On the IG2000/3000 is recall it was about ~230V and ~330V ( this is from memory of testing 6 years ago.

    Did you mean that the switching voltage is 230 v for the IG 2000 and 330 v for the
    IG 3000? If this is right I shouldn,t have any problems with the IG-2000. Might have a problem with the IG 3000 as I estimate about 325 v at STC VMP. Really can,t tell for sure as It has a mixed array. 12 sharp 167 u3a and 2 Kyocera KC 158g and some panels are aged and some not aged. Glad to know these switching voltages. So far I am not having the problems the guys with the IG-5100 inverters are having and I am just guessing, but have a hunch that they are operating at the switching voltages and agree that they should try changeing the number of panels in thier string to see if inverter stops the searching. S:Dlarvic
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    I had to do some digging around, here is what Fronius sent me back in 2004

    The voltage ranges for the different taps are 150V-200V, 200V-270V, and 270V-450V.
    This is for both the IG2000 & IG3000, they both have three ranges ajustable by software and relays inside the units

    Now keep in mind, the unit doesn't switch at 200V/270V , that's the operational limit of the inverter and software has a threshold window of about ~20V as I recall so its likely 180-200V 250-270V are the transition windows to the next tap.

    In the posted logs, its pretty clear something is happening near 250V that's causing the issue.

    For the record I found a couple of issue with the IG2000 & IG3000, I had DOA units, lose screws, over poor build quality, optimistic reported watts and grid disconnects that I proved was their software. Fronius was very open and helpful and I had communication to their engineers in Austria ( through US sales ) and verified improvements they made, so I know more than most about how these units work.

    I'm sure issue with the IG5100 could easily be replicated and I'm disappointed that multiple users are not getting through to Austria its a real problem. The other OP had the installer replace the Fronius with a Power one inverter ... and no issues since

    My contact at Fronius left and went to Xantrex a few years ago, so I have no inside name to recommend for help.

  • rsl360
    rsl360 Registered Users Posts: 14 ✭✭
    Re: Fronius MPP Hunting

    I've checked to see if the inverter is switching transformer taps when it's hunting and it's not. (and I do know what the clicks sound like.) I was pretty sure this was not the case, but I wanted to double check before posting anything.

    What I see when I look at the inverter's behavior is that it lowers the array voltage, the power goes up, but before the power maxs out (and maybe starts to drop), it gives up, raises the voltage, and starts over again. Another strange thing, seen occasionally, is the average array voltage will suddenly drop about 5% (215v to 203) with no significant change in the output. All I can make from this is that the inverter was running on the "higher" end of the MPP voltage, and then it switches to the lower end. Not that this makes much sense.

    rsl
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    rsl,

    I am the originator of this chain and you can see that there is a lot of information in it, most of which I have forgotten now that my system is performing flawlessly.

    I read your posts through a couple of times and looked at your graphs. I believe that you have exactly the same problem that I had with my IG5100 and Fronius has treated you in a similar fashion. There are probably a range of conditions that cause the problem, but in my case the two key things were a low panel voltage of about 230 volts and a high AC ;ine voltage of about 240 volts. I don't know the exact numbers, but one Fronius engineer that I accidentally spoke to readily confirmed that my voltages triggered the error, and that it indeed was a known error.

    When Fronius finally admitted the problem, my installer checked another local Fronius IG5100 installation that used a low panel voltage against the typical Phoenix high line voltage. Although the customer wasn't aware of it, this system was hunting as well.

    I agree that the issue is with the transformer taps, but my inverter was not switching taps either. I am only guessing this, but I think that the software loads the panels while searching for the MPP until it triggers the algorithm that says it's time to switch taps. The software then shuts down the inverter to prepare for a zero current change of the transformer tap. Another software routine is then run to choose the tap. However, during this instant, the panels are open circuit and the software is probably using a different algorithm. Instead of choosing an adjacent tap, the software chooses the same tap again. The inverter is restarted, and the cycle repeats.

    While Fronius declined to fix the problem with their inverter, they did work with my installer to fix the problem. In the case of the other local system with the problem, Fronius bought the customer an additional panel per string to move the DC voltage out of the problem area. I had no room for extra panels, but they bought me a competitive inverter from Power One to replace the IG5100.

    Now, more than a year later, I am very pleased with the Power One inverter. It is a "transformerless" design which improves the efficiency 2-3% over the Fronius. In addition, the Power One has dual independent MPP seeking inputs. I have two arrays with different orientations, so I picked up a little more efficiency with this feature as well. And lastly, the Power One is convection cooled and thus is very quiet compared to the Fronius.

    My advice to you is remind Fronius of this chain. Have them read it again and ask them to either add panels to your system, or buy you a competitive inverter that actually meets its published specifications.

    If you think that I can be of assistance in resolving this, please just ask.

    Thanks,
    Mike
  • rsl360
    rsl360 Registered Users Posts: 14 ✭✭
    Re: Fronius MPP Hunting

    Hello mradtke. Thanks for the interest. I thought from the start that you and I had exactly the same problem. Fronius is now sending me the equipment to log more data, which is also similar to your tale. (Although I think you did some logging, then they sent the new inverter?) Fronius seem interested in solving the problem, not sure why it's so difficult. The new inverter seems to have a different algorithm than the previous one, although as I said, it still has issues. But I believe that fronius is doing their best to solve this, and I think they are entitled to keep trying to do so, at least for now.

    rsl
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Hello rsl,

    Yes, I agree that Fronius should have their chance to sort this out..

    Both I, and my installer spent a lot of time doing measurements at Fronius's request. I was happy to do this because I expected that Fronius would use these data to find and resolve the problem. This all changed when Fronius inadvertently revealed that the problem was already well known. I was further disillusioned when Fronius refused to either fix the problem or update their specifications to reflect the performance gap.

    Have you referred Fronius to this forum chain?

    Thanks,
    Mike
  • rsl360
    rsl360 Registered Users Posts: 14 ✭✭
    Re: Fronius MPP Hunting

    Well, here it is almost a year later. It's cold again and the hunting has returned. When the system is hunting, I'm loosing about 10% of my output. I've heard nothing from Fronius in regards to the measurement that were taken on my inverter, nor have I heard anything as to how to resolve the hunting issue. I've emailed Fronius three times recently, I've heard noting back. This is very disapointing. Fronius KNOWS that there is an issue. I'm willing to work with Fronius on this, but they no longer seem interested. So at this point, I'd have to say that Fronius IG5100 inverters have a problem that Fronius can not, or will not, resolve. It's probably not an issue in all installations, but it's definitely an issue for some. That is, it's not just me.
  • autoxsteve
    autoxsteve Solar Expert Posts: 114 ✭✭✭✭
    Re: Fronius MPP Hunting

    Bummer.

    I have had almost 3 trouble free years with my Fronius inverter. I did have one day where things acted up a bit, and my installer was all over providing a replacement unit but the odd performance only occurred on one day and has not returned in over 6 months.

    Good luck on your situation - your installer should be standing behind the product - and I'd be all over them if they didn't.
  • rsl360
    rsl360 Registered Users Posts: 14 ✭✭
    Re: Fronius MPP Hunting

    Well, you probably would not see this problem in Southern California. Overall, the inverter seems to be pretty good, except when I'm losing 20% of my power from hunting.

    I did manage to contact someone new at Fronius, and to their credit, they are still interested in fixing this. And they still have the information about the first inverter swap, and seem to have some idea as to how to get in touch with the guy who was working on the problem. So the potential to do the right thing is still there.

    And my installer is standing behind the product. I'm pretty technically oriented, so I've been dealing direct with the factory, but the installer is well aware of what's happening. I've got my own data collection system, so it's easier for me to get the information to the factory.
  • tampasolar
    tampasolar Registered Users Posts: 65 ✭✭
    Re: Fronius MPP Hunting

    Fronius IS hiding this from new purchasers. I asked their sales rep UP FRONT whether I should buy the newest IG Plus model or the older IG5100. They did not divulge this hunting concern at all.

    Now that I got the system built, I now have this very hunting issue and would never have bought Fronius if they were a honest company.

    Do they care -- doubtful.
    hybrid: xw6848 pro with two mppt60, 6 kw pv
    17 cell 280ah LiFePO4 storage  14 kw
    gridtie: sunny boy sma 2x 5k
    gridtie: fronius ag5100 5k
    Gateway / Insight Local
    xw4548 backup
  • Macaw
    Macaw Solar Expert Posts: 36
    Re: Fronius MPP Hunting

    Here it is is another year later-- And I noticed the same problem with my Fronius IG3000 and a high AC line voltage. I'm in the process of debugging the solar.access software so I can formally document the problem but in the meantime can watch the built in display and see the massive power fluctuations on a cloudless day.