Grid Tied and Generators

Philip C
Philip C Solar Expert Posts: 45 ✭
in Advanced Solar Electric Technical Forum #1
I have a small problem, I need to wire in a 10kW PV system into a building with an existing 22kW generator, usually not a big issue, just tie in on the line side. Well here is the problem; the generator ties in at the transformer/meter about 300ft away from the building.

How can I backfeed the panel without concerns of backfeeding the generator? Can one adjust the frequency tolerance on the inverter to be more sensitive to swings?


Thanks,
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Re: Grid Tied and Generators

    You should be able to find a connection upstream, between the generator transfer switch, and the grid feed. Larger generators tend to have pretty good fq regulation, so I don't think you can rely on that to drop the PV inverter.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #3
    Re: Grid Tied and Generators
    mike90045 wrote: »
    You should be able to find a connection upstream, between the generator transfer switch, and the grid feed. Larger generators tend to have pretty good fq regulation, so I don't think you can rely on that to drop the PV inverter.
    I have a similar question over on another sub-forum. I have a couple of customers who want to run a system like this and have the PV keep running when the grid is down by letting the generator supply the grid to the inverter.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    Re: Grid Tied and Generators

    I don't recomend anyone try to use their PV to asssist a generator, unless it's through a hybrid GT/battery inverter. Without battery to take any overload, it's just a matter of time, till the loads become less than the PV is generating, When that happens, the system voltage will suddenly climb, and you have a race to see what happens first:
    Generator fries from overvoltage
    inverter senses overvoltage and shuts off.

    Using only PV inverters and gensets, you have no room for error, or edge of cloud surge.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • Philip C
    Philip C Solar Expert Posts: 45 ✭
    #5
    Re: Grid Tied and Generators

    Mike,
    To tie in upstream of the gen set would require trenching through a parking lot. So in this case even the Hybrid XP/Sunny Island would not work as you still have to tie upstream (Well at least to sell extra power back to grid)

    I was thinking by tighting up the tolarance of the freguency settings, when the PV starts to produce to much power, the frequency will speed up causing the inverter to shut down. But one could never guarantee.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #6
    Re: Grid Tied and Generators

    Is there any ac wiring at all (even a single circuit that comes from the utility power?

    Run that back to the gt inverter to inhibit the inverter or turn off a solid state relay..

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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