Feeding a DC Grid Tie inverter

[craigcurtin]

Guys, As part of the Australian version of your Stimulus package we are getting heavily discounted solar panel installation systems. Also a number of our states have gone to a gross feed in tarrif of 60 cents per KWH

I intend to purchase a Grid Tie solar system - these use a Fronius Grid Tie inverter with MPPT - the unit i am looking at will have a max input of 2800w- the supplier will provide 9 solar panels which will generate somewhere around the 160v DC - the entry level voltage for the MPPT is 150v withthe sweet spot being 280v

My thoughts were to use the output from my ST head (whicc will be powering the rest of the house) to provide some additional DC input into the Fronius to effectively keep my load up on my ST for extended run times. I would essentially use this as a "load shedding" option whilst holding power in reserve to start up larger loads as required on AC - there are no batteries involved in this system

I will be getting an st 7.5. head.

What would be the best way to generate say 120vdc (in Australia our AC voltage is 230/240v) at around 20AMPs (max) but more like 10amps sustained. Esentially this would let me choose the optimum run point for my engine whilst being paid 60c KWH from the grid.

Any ideas ?

Craig

[mike90045]

the entry level voltage for the MPPT is 150v with the sweet spot being 280v

Why not try to directly rectify ST 240VAC output, and get yourself real close to the 280VDC sweet spot?    The inverter won't fire up, without 150VDC.  You may need some capacitive filtering, and a way to disconnect the PV array, so your generator doe snot back feed the PV's.  340 peak Vdc, best bet is some 400V AC Motor Run Capacitors.