# 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
26
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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.

Jul 22, 2007
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3. ### Roderick Young Member

Feb 22, 2015
408
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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
10,340
1,850
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.