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My Inverter has 3 MPPT inputs. For some design simplifications (Involving ATS), i would like the three arrays to have separate PV+ but join the PV- wires together at a bus-bar and take the Inverter negative DC input from there.effective layout of the setup

Will this have an effect on the performance of MPPT operating independently? or should i keep the PV- wires separate?

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Without seeing the inverter, if the maker provides 3 separate pv- then I would keep them separate. If they could be joined together, then the maker would have done so.

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  • $\begingroup$ i have an ATS that switches PV power between a Grid Tied inverter and a solar pumping inverter. there is a combiner box at the solar pumping inverter side where the arrays are made parallel. While i have contactors for the pv+ to switch between the Grid Tied inverter And the solar pumping inverter, I dont have the alloted budget to put contactors in ATS for the PV- as well. the diagram provided is simplified, what i have are multiple 36kW inverters where in such is the case. the Makers did separate the PV- but i wonder what will be the performance loss if any if pv- is made common. $\endgroup$
    – Ali Iqbal
    Commented Jan 21, 2020 at 17:18
  • $\begingroup$ So draw the correct diagram of yhe actual situation with the details necessary. $\endgroup$
    – Solar Mike
    Commented Jan 22, 2020 at 7:25
  • $\begingroup$ This question is a better fit for SE Electrical Engineering. | "Electrically" in an ideal situation, combining the -ve leads of three separate MPPT inverters would be without negative consequence. There MAY be code issues (although what they may be and why I know not). Trying to think ahead of Murphy, I'd look for what non idealities MIGHT exist to make a difference. eg combining the negatives at the panels and running a single connection to the inverters MAY result in some interactions. (I'd expect it to be small, but combining the negatives at the inverters seems liable to be better). $\endgroup$
    – Russell McMahon
    Commented Jan 22, 2020 at 21:00
  • $\begingroup$ Does each inverter connect PV -ve to output neutral and/or ground? If not then the PV array per inverter may float relative to output in some manner under inverter control. Combining the input -ves MAY influence this. || I'd expect the inverter manufacturer to have a clear statement on this. || I'd expect it t be OK but would look very hard at "what could possibly go wrong :-) ". $\endgroup$
    – Russell McMahon
    Commented Jan 22, 2020 at 21:02

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