Quite a logical approach, Peter.  You've always got the problem of getting
12V (or other solar cell voltage) to be 120V (or 240 take your pick).
Either you have to solve this with a transformer, or an upconverter as you
suggest.  An upconverter might be a really efficient way to do the job, with
less weight and cost than a bulky high amperage transformer.

Now, switching 240V*1.414 puts you in the realm of IGFETs, and out of the
realm of super-efficeint mosfets, which wimp out pretty much above 100V.
OTOH, you are switching much smaller currents, so the efficiency may wash
out.

You also have less isolation from input to output with this scheme vs a
transformer.  You probably want to tie your grounds together anyway.  Uh-oh
I just thought of something.  Your upconverter is going to make 340VDC.
Your output H-Bridge is going to flip this from one side to the other.  One
pole of your output is neutral, which is connected to earth.  So your solar
cells CANNOT be referenced to ground, in fact they will have 340V AC riding
on top of them.  ouch, this does not sound good.  What is a good way to
handle the grounds in this system?


Would a shorted output transistor expose your solar cells to a 240VAC main
voltage?  Maybe some good fusing*, crowbars, and transorbs are a good idea
on the low voltage side.

--Lawrence

*Fuse (definition) - a device usually protected by semiconductors.  Often
found intact in melted-down electronics.



>
> Does it not make a lot of sense to use a high voltage DC storage battery
> and a sine former (using magic sine etc) and to charge it with a dc/dc
> upconverter from the solar panels and/or a wind generator and/or mains
> grid and/or generator for such power levels ? Because I think that it
> *significantly* reduces switching and I^2R losses at high load time. With
> ~8-10 24V batteries in series and charge equalization control this could
> supply significantly more than 5kW for a short time. The lower current per
> battery would mean that inexpensive smaller batteries could be bought in
> bulk. At 5kW the current would be somewhere near 60A (120V system,
> including something for efficiency). This is permissible even for small
> tractor starting batteries. The upconverting solar charger could be of the
> optimal energy transfer type (easy with this config). A failed battery can
> be removed from the system and its place shorted over with very little
> change in output parameters (though not without a short power break).
>
> Peter
>
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