[RE-wrenches] grid-tie inverters & generators

[Jeff Clearwater, Village Power Design]

Hi Folks,

We burnt up a gen set's voltage regulator on an off-grid system sunny 
island/sunny boy system when we took the sunny island's off-line but 
didn't shut off the sunny boy.  So the SB backfed the genny and fried 
the very expensive voltage regulator on a 30 KW system.  SMA had us 
install a relay to tell the SB to shut down as soon as the AC 
reference from the SI was gone.  Same situation as grid-tie really in 
terms of your question.

Jeff



>Hi Kelly
>
>It is an interesting issue and was just dicussing this the other day.
>
>I think what happens if the inverter backfeeds the genny, the 
>generator voltage will go up, if it goes up enough, it will go 
>outside the window of the inverter and the inverter will drop out, 
>voltage will them return to normal, inverter will reconnect and 
>repeat.
>
>But I sure wouldn't want to fix the generator.  A relay powered from 
>the grid will take care of the problem.
>
>jay
>
>peltz power
>On Nov 19, 2008, at 5:24 PM, Kelly Keilwitz, Whidbey Sun & Wind wrote:
>
>>Wrenches,
>>I'm dredging up this subject again (previous postings 6/08) with a 
>>simple question that doesn't seem to have been answered:
>>
>>Is there any issue connecting a batteryless grid-tie PV system to 
>>the load side of a panel that is backed-up by a generator on an 
>>automatic transfer switch, when the grid is down and the generator 
>>running?
>>
>>In this case the PV is 5.7kW, the inverter an SMA 6000, the 
>>generator unknown size/type, but propane, automatic start, and 
>>backing up the entire main panel.
>>
>>SMA tech support first said it's OK, then that the generator will 
>>blow up. I can imagine, if the inverter tries to sync with the 
>>inverter, that the voltage could rise, causing the inverter to 
>>disconnect, wait 5 minutes, repeat. Is there anything nasty that 
>>could happen?
>>
>>Thanks,
>>-Kelly
>>
>>
>>Kelly Keilwitz, P.E.
>>Whidbey Sun & Wind, LLC
>>Renewable Energy Systems
>>NABCEP Certified PV Installer
>>987 Wanamaker Rd,
>>Coupeville, WA 98239
>>PH & FAX 360-678-7131
>><>sunwind at whidbeysunwind.com
>>
>>
>>
>>
>>
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-- 
~~~~~~~~~~~~~
Jeff Clearwater
Senior Design Engineer
NABCEP (tm) Certified Solar PV Installer
http://www.nabcep.org/
Village Power Design/NorthEast Solar Design
Turnkey Solar Design & Installation for the Commercial Sector
http://www.villagepower.com
gosolar at villagepower.com

Voice: 413-259-3750
Fax: 413-825-0703
65 Schoolhouse Rd
Amherst, MA 01002
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