Hybrid PV/Battery/Generator [RE-wrenches]

Wed Jun 12 14:50:07 PDT 2002

I'd be curious to know how a batteryless inverter would act with one of the
new "inverter" generators.  The ones that I've seen were all under 3kW.  I
almost suspect that a batteryless inverter would not trip off line until it
overloaded the generator.  My crude testing showed that they output some
really nice voltage and frequency.  I don't know about the waveform though. 
Testing my 2800 watt Yamaha unit under various loads my Fluke 87 never saw
anything other than 60.0 Hz and never got outside of 118 to 122 volts. 
Those measurements were taken continuously as I changed loads.  Very
impressive little units.

Travis Creswell
Ozark Energy Services
----------
>From: Kent Sheldon <kentsheldon at sbcglobal.net>
>To: RE-wrenches at topica.com
>Subject: RE: Hybrid PV/Battery/Generator [RE-wrenches]
>Date: Wed, Jun 12, 2002, 3:15 PM
>

>Brad, I know of a handful of installations that have tied SMA Sunny Boy
>inverters to generators. We haven't had any follow up phone calls saying
>they didn't work. The SB inverters rectify the AC voltage sense to DC,
>so this will normalize any error caused by ripple or harmonic
>distortion, assuming it isn't bad enough to skew the true RMS value
>greater than +/- 10%. One thing to watch out for: The SB inverter will
>attempt to deliver current up to the limit of the inverter(s) tied to
>the generator. If the load is not large enough to consume the current,
>the excess will backfeed the generator, causing it to trip offline on an
>over-voltage, or reverse current fault. This generally means that
>grid-tied inverters are only tied to very large generators where the
>load is known never to dip below the output of the available PV power.
>In general, the larger the generator, the better its voltage fidelity.
>
>Regards,
>
>____________________________________________
>Kent Sheldon
>Manager, Industrial Power Systems
>SMA America
>ksheldon at sma-america.com
>925 513 8813 Brentwood Office (Primary)
>530 273 4848 Grass Valley Office
>
>
>
>
>-----Original Message-----
>From: Brad Bassett [mailto:bsbassett at earthlink.net] 
>Sent: Wednesday, June 12, 2002 12:53 PM
>To: RE-wrenches at topica.com
>Subject: RE: Hybrid PV/Battery/Generator [RE-wrenches]
>
>Antony,
>
>The window of operation for a grid tied inverter is so tight now that 
>the chances of one synchronizing with a generator is about nil. I saw an
>
>attempt to get a 20 kW trace tech inverter to synch with a new 100 kW 
>Kohler top of the line generator, and it never even came close. The 
>longest I saw it try before an error on voltage (high and low) or 
>frequency was about 3 seconds, and it takes 5 minutes of good power to 
>synch. 
>
>With a smaller generator such as would be used for a residence the 
>chances would be even smaller. Still it might not be a bad idea to 
>disconnect the inverter while on generator power to prevent any possible
>
>backfeed of dirty power from the generator into the inverter (JB could 
>this be an issue with SMA?).
>
>Another option is to use a battery based backup system for critical 
>loads, and grid tie inverters for the solar. I wonder if you could get 
>them to synchonize with each other!? (Put the grid tie on utility side 
>of backup inverter). Or a combination of battery based and straight grid
>
>tie systems. With some musical relays you could transfer the solar aray 
>from the grid tie to the batteries during an outage. I'll let someone 
>else do that science project!
>
>You also mentioned using a larger inverter, let me know if you find one 
>that's not a scince project in itself.
>
>Brad
>
>
>Antony Tersol wrote:
>
>> 1. If we go with straight grid-tie batteryless PV, we would need a
>> transfer switch downstream, so that the PV wouldn't be running in
>outage
>> situation when generator is on.
>> 
>
>
>
>Brad Bassett
>Schott Applied Power 
>Tumwater, WA office
>bsbassett at earthlink.net
>
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