+ Post New Thread
Results 1 to 4 of 4
  1. #1
    Advanced Member level 5
    Points: 30,053, Level: 42
    Achievements:
    7 years registered

    Join Date
    Sep 2008
    Location
    cambridge
    Posts
    6,284
    Helped
    466 / 466
    Points
    30,053
    Level
    42

    Overvoltage due to solar inverters

    If many solar inverters on the same phase all switch on at the same time, and this phase is lightly loaded, then there will be a high voltage spike on this mains phase. This voltage spike could go up to 500V or more.
    Do you agree?
    The inverters do have overvoltage shutdown, but this is “reactive”, and the overvoltage needs to occur before the shutdown occurs.

    •   AltAdvertisment

        
       

  2. #2
    Super Moderator
    Points: 73,223, Level: 66
    Achievements:
    7 years registered
    Awards:
    2nd Helpful Member
    betwixt's Avatar
    Join Date
    Jul 2009
    Location
    Aberdyfi, West Wales, UK
    Posts
    11,990
    Helped
    3968 / 3968
    Points
    73,223
    Level
    66

    Re: Overvoltage due to solar inverters

    If many solar inverters on the same phase all switch on at the same time
    This is exceedingly unlikely, the 'kick-in' point for most inverters is only at a few Watts of output and their geographic spread and range of types means the start up for them would be widely spread over at least several minutes.

    Also think of the distribution of the 'phase' you are talking about. The phase connection to individual premises and equipment usually originates at a sub-station transformer in close proximity, on the generator side of the AC it is distributed differently. The interaction of delta-wye transformation will in any case spread the load across all phases. If you are concerned about grid-tied installations, which in most cases are < 10KW, they are not allowed to hot switch to the line, by law they have to monitor and synchronize exactly to the 'background' AC before connecting so the chance of a spike is very unlikely. My own inverters here take three minutes each to sync before connecting.

    There would be little point in inverters having over-voltage shutdown, although some may in case of a fault occurring, they are only designed to match or slightly exceed the natural line voltage.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.


    1 members found this post helpful.

    •   AltAdvertisment

        
       

  3. #3
    Super Moderator
    Points: 64,830, Level: 62
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    13,161
    Helped
    3040 / 3040
    Points
    64,830
    Level
    62

    Re: Overvoltage due to solar inverters

    Hi,

    Earlier invertes had fixed timing, but then one recognized the probkem when a lot if inverters seitch ON or OFF at almost the same time.
    Thus - afaik - they included some random delays.
    Also modern inverters react on mains frequency, because this (still) is a measure wheter there is too much or too few energy in the grid.
    Older solar inverters switched OFF when the mains frequency was too low, ...this means they switched OFF when there already was too few energy in the grid...this is counterproductive.
    Nowadays solar inverters may reduce power when mains frequency is too high and may increase power when frequency is too low.
    For sure there are limits... when mains frequency further is reduced ... thdn there is no other way than switching OFF.

    Klaus

    About mains voltage:
    Here in our region we have a lot of solar power. Private systems on the houses as well as large solar plants.
    I measured mains voltage over a couple of weeks. With 230V RMS one expects 325V peak. I think there never was a sample (fs = 3600Hz with about 1200Hz LPF) that was higher than 335V. Very far away from 500V.
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.


    1 members found this post helpful.

    •   AltAdvertisment

        
       

  4. #4
    Super Moderator
    Points: 247,256, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    42,987
    Helped
    13082 / 13082
    Points
    247,256
    Level
    100

    Re: Overvoltage due to solar inverters

    I'm reluctant to discuss the poorly elaborated question without referring to inverter design and specification. Solar inverters that I know are three-phase connected, so the prerequisite of a "light loaded phase" already misses the point.


    1 members found this post helpful.

--[[ ]]--