Three phase grid tie system with SMA product

Hello every one,

I am design a generation system with solar panel and batteries, I have selected a group of important load for do the backup, but I don't sure how connected the sma component, the grid is three phase 208/120 @60Hz, and the'll connect:

  • Three Sunny boy 3000 TL in delta configuration connected from L1 and L2 of each one of them to the L1, L2, L3 of the electrical enclosure.
  • Three Sunny Island 4548 connected in Y configuration from L1 and N (AC1) of each one of them to the L1, L2, L3 of the electrical enclosure, and connected in Y configuration from L1 and N (AC2) of each one of them to the L1, L2, L3 of the grid.
  • The load will be distributed in a balanced way on L1, L2, L3 of the electrical enclosure.

I would like your opinion about this design and connections!


  • BB.BB. Super Moderators, Administrators Posts: 30,653 admin
    That is a fairly large system--And, I would suggest you really need help from the company and/or a local electrical engineer familiar with 3 phase power... SMA, while a good company, is not very common in the US--So I am not sure how many folks here have the experience needed.

    Just to give you an idea of what can happen:

    Good luck,

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    edited January 2017 #3
    On general principles I would try to avoid the mixture of delta and wye connections that you propose.
    If all components are working properly it is likely to be trouble free, but if you have mostly single phase line to neutral loads that you plan to balance roughly, consider what will happen if any one of the inverters fails:
    Because of the interconnection of delta to wye you are most likely going to lose production capacity on two phases  (or worse) instead of just the single phase loss that you would get with both parts of the system in wye.
    In addition, and possibly more concerning to me, the throttling effect exerted by the SIs on the SBs in case of overproduction compared to the connected load will be coupled badly to more than just the current generated in that leg of the wye.
    Although, for that matter, I would expect you to have to lock the SIs to the same exact frequency at all times. Otherwise the line to line SBs would not be able to work at all.

    The very first question is whether SMA even supports three phase generation with three independent SIs instead of a single three phase inverter.
    The situation in the other thread involves a generator which would serve to keep the frequency the same on all three phases as long as it was running. You do not have that component to organize your system.
    SMA SB 3000, old BP panels.
  • mvasmvas Registered Users Posts: 382 ✭✭✭
    edited January 2017 #4
    I do believe that the three properly inter-connected Sunny Island 4548 units will support 3-Phase.
    Then each Sunny Boy 3000 will supply power to just one of the 3 phases.

    You should contact SMA engineering for the details of a mixed wye-delta 3-Phase design.

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