Grid-Tie inverters don't like to ac couple to Hybrid inverter

[keepsake]

Looking for Grid-Tie inverter recommendation or observations ...

Have Xantrex 4548 hybrid inverter.
Also Fronius IG5100 grid-tie inverters
The Fronius do not like to ac couple to the Xantrex, they will but cycle every minute or so.
Fronius will not support this configuration.

I am looking to get different grid-tie inverters to will willingly ac couple to Xantrex output.

Any thoughts or anyone have contacts at other manufacturers that will work with customer to better allow off-grid usage?

 

[GoldDigger]

1. Do you have enough load on the system to consume the full output of the GTIs? If not the setup you describe will not work.
2. It is best to use components like the SMA SunnyBoy and SunnyIsland which are meant to work together AC coupled.
What those combinations bring to the game is a mechanism by which the battery inverter can throttle back the GTIs without just knocking them offline.
If the GTIs are producing more power than your local loads consume, the Xantrex may be able to cope for awhile by charging the batteries, but once that load is exhausted (batteries in Float or Absorb, limiting the power they can accept) the Xantrex will let the voltage or frequency go out of the GTIs input range, forcing them to turn off.
By the time the Fronius requalifies the input (five minutes) the Xantrex has pulled the batteries down some.
The above is a neat hypothetical scenario that would produce your symptoms. It may have no relation at all to your problem.
But you can be sure that if the Fronius trips out either the voltage or frequency is going out of spec or another anti-islanding test is failing.

 

[keepsake]

you are very well versed with Hybrids

you are very well versed with Hybrids

Your assessment is so right on the money.
Now I have procured engineering codes to extend voltage cut offs and frequency range limits and even reducing the 5 minute lockout from Fronius. Electric codes on the 5 minute window only apply to grid-tie operations. It is loads off-grid like the well pump or hvac compressor starting that 'annoys' the Fronius inv. My goal is to find another manuf that allows off-grid config of a unit and operation without the islanding restrictions, while still achieving the grid-tie acceptance. Such manuf cooperation may not exist for political reasons.

 

[jaggedben]

I could be wrong, but I believe that in your configuration the Xantrex is designed to cut off the Fronius with a frequency shift if the batteries are charged and there's no load to consume the power. So it could be that the system is working as designed if the batteries are charged.

As Golddigger said, the SMA system is much better suited to AC coupling. Or, if you have no connection whatsoever to a utility grid, use all off-grid inverters. Outback is the other most prominent brand to consider.

 

[GoldDigger]

Your assessment is so right on the money.
Now I have procured engineering codes to extend voltage cut offs and frequency range limits and even reducing the 5 minute lockout from Fronius. Electric codes on the 5 minute window only apply to grid-tie operations. It is loads off-grid like the well pump or hvac compressor starting that 'annoys' the Fronius inv. My goal is to find another manuf that allows off-grid config of a unit and operation without the islanding restrictions, while still achieving the grid-tie acceptance. Such manuf cooperation may not exist for political reasons.

I think that the lack of the product you want is the result of UL listing requirements. Some may call that political, but I call it basic safety.
The SMA system works because the SI is designed to satisfy all of the anti-islanding conditions that the SB checks for, rather than defeating those tests. Turning off anti-islanding might not even fly in a managed industrial environment, let alone a consumer environment. The effect of surge loads from pumps, etc., dropping the voltage is something I had not thought of. The only solutions I can think of for that are VFD or sizing the battery inverter to handle the entire surge without excess deviation.

 

[SolarPro]

If you haven't already done so, you might want to check out this article about AC Coupling, which includes info about SMA and Schneider Electric's (Xantrex) product platforms. It also covers some general challenges associated with using dissimilar products.

 

[GoldDigger]

If you haven't already done so, you might want to check out this article about AC Coupling, which includes info about SMA and Schneider Electric's (Xantrex) product platforms. It also covers some general challenges associated with using dissimilar products.

An excellent compilation of diverse input! Thank you for the link.
Three things particularly caught my attention:
1. Outback's comment that the battery inverter needs to be capable of driving motor starting and other surges without voltage sag or spike. In the OP's case this condition may not be met.
2. One of the panel member's comments stated that without the comm cable the SMA SunnyIsland could not exercise proportional control over SunnyBoy output while the SMA rep specifically states the exact opposite.
3. Any scheme that uses frequency shift cannot work in conjunction with the currently available generators, since the battery inverter must follow the generator frequency. Only selective shutdown and diversion loads can currently support this.

 

[jaggedben]

...
3. Any scheme that uses frequency shift cannot work in conjunction with the currently available generators, ....

Well, not at the same time. But a system can use frequency shifting when batteries are charged and interactive power is surplus, then shift modes and run at the generator frequency when those two things are not the case. Since the point of these systems is generally to limit ICE generator use to times when renewable sources are not available, that's generally fine.

 

[GoldDigger]

Well, not at the same time. But a system can use frequency shifting when batteries are charged and interactive power is surplus, then shift modes and run at the generator frequency when those two things are not the case. Since the point of these systems is generally to limit ICE generator use to times when renewable sources are not available, that's generally fine.

A good point, just requiring more switching and control that the two inverter components may not support on their own. No one size fits all by any means.
Also good if the battery inverter includes generator support logic.

 

[ggunn]

A good point, just requiring more switching and control that the two inverter components may not support on their own. No one size fits all by any means.
Also good if the battery inverter includes generator support logic.

The Sunny Island/Sunny Boy system can coexist with a generator, starting it and stopping it at programmable battery SOC states. The SI has a LOT of programming ability in addition to its capability to gracefully throttle the SB(s) that share the AC bus. One cool thing it can do is to sometimes shift frequency higher to control the SB output and sometimes lower so that the net effect cancels; AC clocks and timers don't drift far off their setpoints.