Wanting to build a grid tie inverter.

Discussion in 'The Projects Forum' started by Chacabucogod, Mar 31, 2015.

  1. Chacabucogod

    Thread Starter New Member

    Nov 16, 2013
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    Problem is I don't know much about control theory. First things first. It'll be fed by 24 Vdc and will output 120 Vrms. I have to control phase, frequency and amplitude. In this initial stage I'll use a trasnformer and an array of opamps to get the signal using SPWM. That way I'll get the phase and the frequency.

    Problem is amplitude. I've read the amplitude of the 60Hz signal that you get after filtering is m_a*Vdc/2 where m_a is the division between the amplitude of the sine wave and the triangular wave you are comparing. I don't know wether to use a boost converter to get the Vdc real high and the just filter it, or get it to a somewhat good level and the use a transformer. Any questions, please feel free to make 'em. I would highly value suggestions.
     
  2. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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  3. Roderick Young

    Member

    Feb 22, 2015
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    Just to make sure, is this a senior or master's project for college, or did you just want to make one? If the latter, it's a dangerous thing to build, and illegal to connect in every location that I'm aware of in the US. You'd be better off just buying a microinverter from Enphase. And even if you get the commercial microinverter, you'll still need a permit to install it, generally - it's not generally legal to simply connect it without permission from your power company.
     
  4. Chacabucogod

    Thread Starter New Member

    Nov 16, 2013
    26
    1
    Yeah this is a senior project. Don't worry about that! haha. Any thoughts about my questions?
     
  5. Papabravo

    Expert

    Feb 24, 2006
    10,137
    1,786
    The problem with a boost converter is that you must go from low voltage high current to high voltage low current with some losses. Assume for example you want to go from 24V @ 6A to 170 V. How much current would be available if the conversion was 80% efficient?
    24V * 6 A = 144 Watts input power
    144 Watts @ 80% Efficiency produces 115.2 watts output power
    115.2 Watts / 170 V ≈ 0.677 Amps

    And you begin to see the problem. The more output current you want the bigger the draw from the primary source.
    You may have to get some AWG #6 wire to hook things together.
     
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