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Feeding solar power back into municipal grid: Issues and finger-pointing - Page 22

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Posted by trader4@optonline.net on April 19, 2011, 2:02 am
 
wrote:

        !

        !

    !

        !

OK, got the drawing straightened out and it plus the analysis are
above.  Just to add some clarification, I said the only way for
the PV array to start delivering power is for it to raise it's
voltage, which in turn raises the grid voltage.   That assumes
that both the load and the other power source remain constant.
As I stated in other posts, the other ways for the PV array to
deliver power without it's voltage going up would be for the
load to increase, ie Rload gets smaller,  or for the other power
 source V2 to decrease in voltage.

Posted by Mho on April 19, 2011, 2:13 am
 
Adding another source lowers the net impedance of the supply to the load.

This is simple network theorem. Even ohm's law can tell you the voltage
requirements.

The voltage at the grid connection (assuming where Rg is) will not be the
same as the V2 source.

In DC theorem what you are saying would be basically all true but in AC we
have waveform phase angle and waveform distortion.

As an extreme example: consider a PV co-gen that is 180 degrees out of phase
from the grid. Now we can have a 10 volt PV source hooked to a 240V grid and
still supply current from it.
--------------------

wrote in message

wrote:

OK, got the drawing straightened out and it plus the analysis are
above.  Just to add some clarification, I said the only way for
the PV array to start delivering power is for it to raise it's
voltage, which in turn raises the grid voltage.   That assumes
that both the load and the other power source remain constant.
As I stated in other posts, the other ways for the PV array to
deliver power without it's voltage going up would be for the
load to increase, ie Rload gets smaller,  or for the other power
source V2 to decrease in voltage.


Posted by trader4@optonline.net on April 19, 2011, 2:18 am
 
Well, duh!  I think everyone here, on both sides of the discussion
acknowledge that.



Not just basically, it is ALL exactly true with the equations to back
it up.
As for the complications of AC, there wouldn't appear to be much
point in discussing that until there is agreement on what happens
with a simple DC distribution system voltage example.





Posted by Mho on April 19, 2011, 3:00 am
 I guess I went too fast for you with the AC stuff.

The whole point is regarding AC connections and different rules apply. The
DC basics are mostly valid no matter how much you want to disagree with
something but still  moot and established by the discussing people about 100
posts ago. Your ASCII schematic was nice.

I will let you disagree with yourself a little more  for the next while.
----------------

wrote in message


Well, duh!  I think everyone here, on both sides of the discussion
acknowledge that.



Not just basically, it is ALL exactly true with the equations to back
it up.
As for the complications of AC, there wouldn't appear to be much
point in discussing that until there is agreement on what happens
with a simple DC distribution system voltage example.





Posted by David Nebenzahl on April 19, 2011, 7:00 pm
 On 4/18/2011 7:02 PM trader4@optonline.net spake thus:


ohm

             !

             !

          !

             !

Sorry, it's still a hopeless hash.

I really do want to follow your example, but I can't until I can see
your circuit diagram properly. This ASCII-art thing clearly isn't
working; any chance you can post a picture somewhere? Then I'll be able
to follow along.


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   wassup
   nuttin
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   k
   where
   here
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