Sunny Island Inverters

Toddlingham
Toddlingham Registered Users Posts: 7 ✭
in Solar Product Reviews & Opinions #1
Because of SMA inverters ability to link together the AC outputs of numerous systems and loads scattered here and there, they open up the potential of creating a mini grid of our own. Where I can use the power where I want and produce it where it's convenient. several PV arrays at different locations and wind turbines can tie directly into the AC transmission lines that the shop, house, wells, garage, neighbors place etc. are all running off of. It sounds just like what I've been wanting to do. Has anyone tried it? Are the SMA inverters performing well for anyone out there? Does anyone know how to force more than one Outback system to match phase? Get two hubs to follow one master or make something that reads the existing phase and convinces an outback hub-10 to match phase and contribute to the existing phase? How would you tell an array 1/2 mile away to back off when the batteries were full? How can I tell a well pump 1/2 mile away to turn on when I have power to spare? I want to link 9 stand alone PV systems and 11 Turbines to 27 loads. We have a lot invest in Outback already. Any ideas?
Sample system: 14850 Watt array, 3750 AH 48 V battery, 5 Outback MX-60, 5 Outback VFX-3648 inverters, 4 Whisper 200 turbines. Stand alone. We have three in that ballpark and the rest are smaller. I want to make our own off grid mini grid. I'd like to keep at least some of our Outback stuff. This is fun.
Thanks.
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Comments

  • tallgirl
    tallgirl Solar Expert Posts: 413 ✭✭
    #2
    Re: Sunny Island Inverters

    Some of what you've described is just plain hard with OutBack gear (it's also hard for other gear ...). Other of it can be made easier with "AC Coupling" and using G-series inverters, rather than V-series.

    I have access to some OutBack technology that will make this a much easier task than otherwise. I also have to be away from the office most of the day,. now that the snow has stopped and the sun is shining.

    The short answer is that yes, it can be done. It requires software, generally speaking. It may also require that your Mate's be reflashed.
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #3
    Re: Sunny Island Inverters

    using the SMA stuff to make a mini grid works great I have seen one such system done that way and there has been several articles in Home Power as well about doing just that. Kind of cool just one set of batteries but every house on the block has pv or wind and it is all tied together.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #4
    Re: Sunny Island Inverters

    Just thinking out loud here... given that you already have a bunch of Outback inverters, perhaps the following setup is possible:

    - Create a central mini-grid with 1 SMA Sunny Island inverter and its associated battery bank.
    - Connect all new shared power sources (wind, PV)to this mini-grid using SMA inverters. This will only make financial sense for the larger generators, e.g. bigger than 1kW wind turbines because of the high cost of the SMA inverters.

    Now for the tricky bit, that may or may not work :)

    - Convert your VFX inverters into GVFX inverters (I believe outback have a service to do this for $300 a pop).
    - Homes that already have their own VFX + batteries could now connect their GVFX to this mini-grid. The GVFX's would sync with the grid created by the SMA.
    - In theory you could have some homes with their own GVFX + batteries + solar + wind, where the solar and wind charge the local set of batteries in the home. Once the batteries are charged the GVFX will sell the excess to the mini-grid where it can be shared by the other loads.
    - Similarly, if the batteries in the home are undercharged the GVFX could draw from the mini-grid to charge them.

    So homes that want to invest in their own renewable energy system can do so, and the energy they create will go to charging their own batteries first, while the excess will be shared to everyone else on the mini-grid.

    Shared resources, like a big battery and large PV array can be connected to the mini-grid so that it's shared by everyone. You'd have the best of both worlds: the ability to buy and sell excess between consumers and the stability of a central mini-grid system that can augment the defiencies in individual systems.

    I don't know what the GVFX limits for the grid frequency are, but these will be critical if they are to work with the SMA because if there's excess power in the mini-grid, the SMA will increase the frequency, proportional to the excess. E.g. 60Hz means there's no excess and 62Hz means there's 100% excess. So the GVFX's will have to be configured to buy and sell based on the grid frequency. I.e. if there's too much power in the mini-grid, the GVFX must buy and stop selling. If it can't buy, then it must disconnect. AND importantly the GVFX must be able to support the full frequency range that the SMA will swing through. I believe it's 2Hz by default, but it may be adjustable.
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  • tallgirl
    tallgirl Solar Expert Posts: 413 ✭✭
    #5
    Re: Sunny Island Inverters
    stephendv wrote: »
    I don't know what the GVFX limits for the grid frequency are, but these will be critical if they are to work with the SMA because if there's excess power in the mini-grid, the SMA will increase the frequency, proportional to the excess. E.g. 60Hz means there's no excess and 62Hz means there's 100% excess. So the GVFX's will have to be configured to buy and sell based on the grid frequency. I.e. if there's too much power in the mini-grid, the GVFX must buy and stop selling. If it can't buy, then it must disconnect. AND importantly the GVFX must be able to support the full frequency range that the SMA will swing through. I believe it's 2Hz by default, but it may be adjustable.

    The G-series inverters can't be configured to buy and sell based on frequency -- they buy and sell based on battery voltage. Additionally, they have a fairly narrow frequency range (59.3 to 60.5Hz) and must disconnect when the frequency gets out of range. This makes the Sunny Island a poor choice.

    I'm able to turn sell and charge on and off based on the power balance on the micro-grid, but it's done with software. There's no way to do it with Mate settings.
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