Hybrid PV/Battery/Generator [RE-wrenches]

[Brad Bassett]

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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