[RE-wrenches] PID

boB at midnitesolar.com boB at midnitesolar.com
Fri Dec 27 11:22:08 PST 2013



My 2 cents worth here says that this PID problem is the same as the 
negative ground problem that occurred with the
Sun  Power modules that wanted to be positive grounded.  Last I heard, 
from Sun Power was that they
have basically gotten around that issue and  are "ground agnostic" as 
either Sun Power or Bill Brooks
says.   Transformer-less or non-isolated inverters are used with an 
un-grounded PV array and I
think that is what Zachary Strassman  is talking about in his reply to 
the question.

I do not see the answer to the question about AC line frequency ripple 
though which
would be 120 Hz (US) or 100 Hz for a 50 Hz grid system at the PV module.

The ungrounded part makes sense but as far as TL inverters vs. inverters 
with transformers,
both topologies should try to keep the PV voltage right at maximum power 
point voltage.  If they
do that to extract as much energy as possible from the array, there will 
be little to no 120Hz or 100Hz
ripple...  If the inverter is designed correctly anyway.

boB



On 12/27/2013 8:39 AM, Drake wrote:
> Hello Wrenches,
>
> Attached is an article from Home Power that came in my email. It says 
> module degradation is increased by PID (Potential Induced Degradation) 
> by the use of transformerless inverters.  It says power degradation 
> can occur over days or weeks and cause a 10% to 60% loss of efficiency.
>
> I called Power One and SMA and their tech support people have not had 
> any reports of problems. Is this something we need to be concerned about?
>
>
> Thanks,
>
>
> Drake
>
>
> Drake Chamberlin
> /Athens Electric LLC
> OH License 44810
> CO License 3773
> NABCEP Certified Solar PV
> 740-448-7328
> /http://athens-electric.com/

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