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Sunny Island Setup for DC coupled utility interconnect

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  • Sunny Island Setup for DC coupled utility interconnect

    Anbody know how to setup a Sunny Island to export and import power without disrupting a DC coupled solar array?
    I have a customer with a large (10 year old 12kW array, 6 Outback inverters, 2 failing Trace SW inverters) that needs to replace the trace inverters in order to maintain his grid interconnection. I have been trying to do it with a Sunny Island, but as sophisticated as it is - am having trouble getting it to export excess power during the day (in order to keep the three charge controllers cranking) and import makeup power at night (she runs her A/C all night and does not have near enough battery). Obviously, these folks want to be "green" without sacrificing..... Lets not go there. I'm finding the Sunny Island has a lot of sophisticated operating modes, but it is hard to figure how they interact. So far the SMA techs tell me the only way to do a DC coupled setup is to use special internal codes to shut down the grid connection during the late afternoons to prevent it from exporting too much power, then reconnecting sometime in the night to help out the battery. Trouble is when it reconnects, it wants to do a full battery charge cycle and the next morning the batteries are full with no where to put the solar power. We can decrease the allowed charging current, but then may not be able to keep up with the night time load (depending on weather conditions).
    It just seems like there ought to be a way to export and import power to keep the battery with a certain SOC range.
    BSEE, R11, NABCEP, Chevy BoltEV, >3000kW installed

  • #2
    I would have simplified the system to all Outback.

    So are you trying to DC couple a Sunny island? To the same bank that you have Outbacks on?
    What Charge Controllers are you using? FlexMax?
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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    • solarix
      solarix commented
      Editing a comment
      yes, three FX60 charge controllers. Would a Radian be able to do this better? This is the usual hybrid problem where the inverter wants to keep the batteries fully charged whenever the grid is available which shuts down the charge controllers. We are way beyond simple here.

    • ButchDeal
      ButchDeal commented
      Editing a comment
      do they currently have Radians? (probably FX) In any case yes. mine does all day long. It charges batteries and exports all the rest of the power. That is the default grid tie mode.

      Having all Outback would allow the CC to talk to the Mate and inverters and battery monitor....

      You can contact Outback about the best solution.

  • #3
    My understanding of the Sunny Island is that if you indicate the AC source is grid it will maintain the batteries (charged) and only pull from them if the grid goes away. This will allow full backfeed when the solar inverters are active and the batteries are topped off. To use the battery power as grid replacement will only be possible when the grid is disconnected. There is no partial battery backup from what I can see. So if the batteries do not support night-time HVAC needs in summer then it could only be used for part of the night by using a timer to disconnect the grid for a specific interval. Delaying the charging until the array is active may take another creative solution, but I'll have to re-read the SI6048 manual to see if it's already in there somewhere.
    23,760W = 99x240W, 3 Sunny Boy 7000 grid tied

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