Grid tie inverter

Possibly.  Several important questions first:

• What control board & firmware revision is your GS 6kw inverter?  (Rev. A.1 / B / C, and 1.1r??)
• What's the make/model on the grid-tie inverter?

I would be a little concerned about connecting 12kw of grid-tie to the output of a 6kw inverter...particularly as grid-tie inverters exist to blast as much power at the infinite grid as they can.  Yes, we've designed GS inverters to handle grid-tie systems operations (via automated frequency shift)--but if your grid-tie system doesn't support frequency shift (older ones generally don't), that might be a bit problematic.

Worth noting that the batteries can be charged through the GS inverter when grid-ties are connected to the output.  This actually is a side effect of the hardware design of an LF inverter--and the only thing the GS inverter can do to stop it is to frequency-shift "throttle" and/or shut down.  (This is why I'm a little concerned about connecting 12kw of power to a 6kw inverter.)

Honestly, while I've designed/written firmware for grid-tie support (GTM status = grid-tie master), nobody I personally know has a grid-tie system that we can test and tweak GS firmware on!  So if you don't mind being dev help with lots of diagnostics/testing (GS and grid-tie hardware permitting), we should be able to get this working.

It's already tied to the meter and I am net metering. I understand the ramifications of backfiring the grid which is why I had the meter box upgraded to have a main disconnect to the meter.

The grid tied inverter is only about 6 months old and as was explained to me it sees the sine wave and sync up with it prior to connecting to the grid.

The make is Solar Edge, the model is SE10000H-US.

Oh and I'm running Rev c 1.1r6

I'll look up the grid-tie inverter later today, see if it supports linear frequency shift throttling.  I believe all newer grid-ties do--but if you got a NOS ("new old stock"), it might not.

Standard grid-tie inverter 😉.

Got a fault this morning.  Had plugged it in to charge my semi batteries and run the fridge. Nothing is hooked to the output side. I do have extension cords plugged into the recepticals though. 

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Output receptacles = output side, they're just one step beyond the output terminal strip.

If you can reliably reproduce this error, I will need to dig into it a bit further.  Basically, if the inverter measured AC voltage on the output at startup for ~0.5 seconds, it'll throw that error (instead of starting the FETs and blowing itself out).  A screenshot of the "DVLT" and "DAMP" oscilloscope channels (debug volt / debug amps) would be very handy for seeing what the inverter actually saw when it tripped out (all of the others continue refreshing regardless of whether it's running or not).

As a company, they're as tight-lipped as could be--or whether or not they have lips should be the question.

The absolute most I could find was from this forum post:

https://teslamotorsclub.com/tmc/threads/hd-wave-with-frequency-shift-power-control.253395/

While the SE10000H is UL1741 SA and IEEE1547 compliant (which include frequency-shift throttling), said standards do not necessarily require that frequency-shift throttling is included to be certified.  The Solar Edge documentation provides absolutely no indication of whether or not frequency shift throttling is included--or if it is, what the specifications are.

With these uncertainties in mind, I would be very hesitant to connect it to your GS inverter--ESPECIALLY as you have a 12v unit.  If the grid-tie inverter mercilessly dumps 10kw into the GS inverter, it's going to very quickly blow the GS inverter's FETs out with brute overcurrent (not to mention your batteries getting the 10kw of power dumped into them...until the FETs explode).  Which that is how grid-tie systems function: after a required "startup delay", they will usually put the pedal to the metal and dump as much power out as possible--and while the GS inverter is programmed to react and shift the frequency upwards (to throttle down/shut down) the grid-tie unit, that process takes time (1-2 sec to avoid oscillations).  And the one thing the FETs don't have in that case IS time.

If you knew for sure that the Solar Edge inverter supports frequency shift throttling AND if you could reduce the maximum output power down to <6kw--yes, we could get it working.

In order to test frequency shifting support, could he just put a ~20A breaker in front of it?
Should trip the breaker if it starts shoving power through it. Not sure if that would be fast enough to save the fets, though...

18 hours ago, NotMario said:

Not sure if that would be fast enough to save the fets, though...

Probably not...especially considering most breakers are thermal, not magnetic.

The biggest issue is that 12,000W / 12v = 1,000A (not including efficiencies).......and the FETs in the 6kw inverter are conservatively rated for 600A.  If he was at 24v or higher, they would probably survive.

Would diodes work? I don't need the GS to do anything other than provide a sine wave signal so it thinks the grid is up.

No.  Two reasons:

• We're working with AC, not DC.  Diodes aren't an option here.
• The grid-tie inverter NEEDS a load on the output OR else it needs to be throttled down some way or another.

If the GS inverter did not dump power into the battery, the grid-tie inverter's output voltage will go through the roof and/or possibly blow itself up.  The reason the GS inverter would dump the power into the battery is because the GS inverter will throttle down to regulate the output voltage...and all that power has to go somewhere.

It's a lot like trying to use an engine that has the throttle stuck wide-open.  You either have to get the brick off the pedal, or load the output down.  If neither happens, the engine will over-rev and blow itself to pieces (after it's been "started" by the grid).

The biggest issue is that 12,000W / 12v = 1,000A (not including efficiencies).......and the FETs in the 6kw inverter are conservatively rated for 600A.  If he was at 24v higher, they would probably survive.

If the GS inverter is 36 v  then  using a fast blow 20 amp  glass fuse  the FETs   can be saved  ?         

My bad, I missed a word in that post...if he was at 24v OR higher, the FETs would probably survive a 12kw blast from a grid-tie inverter.

My bad, I missed a word in that post...if he was at 24v OR higher, the FETs would probably survive a 12kw blast from a grid-tie inverter.

Your  48v  GS 6kw  with the rev C2 control board will  survive  a backfeed to the  grid  ?      Then if I   use  FETs rated for 600A  and 2  fast blow glass fuse instead of breaker to the output of my  15kw  Powerjack it will  also  survive a backfeed to the grid  ?        I  have not try to backfeed  to the output of my inverter   but Sean in the youtube say he did it by mistake  and the GS inverter survive .