Voltronic hybrid vs off-grid

[LuxOfTheIrish]

Hello, I'm fairly new so apologies if this was discussed earlier, I searched and read relevant posts as best I could before posting this:

I contacted a company that sell victronic clones but didn't get a clear answer:

An off-grid voltronic "clone" has an AC input. Does that mean that it will take grid to supplement output but never backfeed? So is it operating on an unmatched sinewave?

Secondly, is there a way to operate a voltronic "hybrid" inverter with no back-feed to the grid? If I have the AC output not connected to the grid(?) or will it still always potentially backfeed throught the AC grid input?

I don't really trust the CT clamp option for the newest smart meter. I don't want any export.

Thanks in advance

 

[BentleyJ]

Is all about the Inverter with regard to being "Grid Interactive" or not. An Off-Grid Inverter may have an AC Input but this is only so AC can pass-thru and charge batteries if PV was insufficient. This type of inverter has an internal relay that will open if the grid goes down. This way the inverter can start up and supply the load but not back-feed the grid, Anti-Islanding provisions. Lastly, there is no unmatched sine wave because the inverter is never operating when the AC Input relay is closed to allow grid input.

The other type of inverter is more sophisticated and can match frequency and phase angle of incoming grid power so both inverter and grid can share the load or even sell excess PV production back to the utility.

 

[LuxOfTheIrish]

Thank you for your reply. Sorry just so I understand fully - the "off-grid" is essentially 'either/or' - only ever either PV OR GRID but never both at the same time? So if the PV was only providing 1kw and the load was 2kw what happens?

For the hybrid, do you know can export of surplus happen through the AC input/grid terminals of the inverter or only the AC output/load terminals (providing the output load circuit is also connected to the grid)?
Thanks

 

[kommando]

In the UK off grid means off grid, so a non approved off grid inverter can only have an AC genny connected to the AC input of an off grid inverter. A grid tied inverter needs G98/G99 approval. I believe the equivalent in Ireland is EN 50438. So do any of the inverters you are considering have EN 50438.

I have an approved grid tie inverter and have 2 options to limit export.

The one I use monitors the incoming mains using a CT clamp and if it detects export, it diverts that to an immersion heater and the inverter output is unchanged.

The other option is a CT clamp connected to the inverter, if that detects any export it throttles back the inverter output to eliminate the export.

On both a small amount can get exported but not enough to be bothered about.

 

[AntronX]

Voltronic type AIO internal inverter does sync up and connects in parallel with the grid input but it's designed to not generate more than AC load is consuming. This way it effectively prevents grid export. It works similar to those grid-tie inverters with limiter CT option but it's all done in the box.

 

[Mattb4]

Thank you for your reply. Sorry just so I understand fully - the "off-grid" is essentially 'either/or' - only ever either PV OR GRID but never both at the same time? So if the PV was only providing 1kw and the load was 2kw what happens?

For the hybrid, do you know can export of surplus happen through the AC input/grid terminals of the inverter or only the AC output/load terminals (providing the output load circuit is also connected to the grid)?
Thanks

In your first case if the load exceeds the AIO's capacity it will go to overload fault. Grid does not supplement because it is not in parallel with inverter. it is either or. Grid pass through or Inverter supply.

Hybrid or grid assist designs will parallel with the grid and increase load rating. They can be set such they do not backfeed and normally would not output on the AC in terminals

Hybrid grid tie models can export through the AC in. Typically the AIO's AC output would go to a dedicated critical load panel that would not shut down with anti-islanding.

 

[wattmatters]

In your first case if the load exceeds the AIO's capacity it will go to overload fault. Grid does not supplement because it is not in parallel with inverter. it is either or. Grid pass through or Inverter supply.

I think the problem is there are so many variants of AIO firmware it's hard to answer the OP definitively, they really need to read the user manual for the specific model in question.

For instance when my AIO (an EASun 8kW) is in Utility First mode, AC loads are supplied via pass through of grid power. Meanwhile the battery is being charged by the off-grid PV array connected to the AIO. It might also use some supplemental grid power to charge the battery (my automations look after if/when that happens).

However, when the AIO has finished fully charging the battery while is still operating in Utility First mode, then it will use the off-grid solar PV to supply loads blended with some grid power. It always keeps a little grid power flowing through to loads, never exports.

But once the unit switches over to SBU mode, then the grid no longer supplies any load, that's all the PV and battery.

Example, one nice sunny day in October:



Midnight to 06:58 the unit was in SBU mode, supplying the home from the battery, with a tiny bit of PV starting to contribute as the sun rose.

At 06:58 the unit was switched over to Utility First mode, so loads were now being supplied by the grid, passing straight through the AIO (I do this because my grid-tied PV array is much larger than my off-grid PV array).

At 14:33 the battery was fully charged and moved to a float mode. The AIO then changes tack. When it moves to float the off-grid solar PV is then used to cover loads, with an minimum amount of supplemental grid power blended in (it does that to ensure zero export). During this time it is frequency matching and blending off-grid with grid supply.

At 16:41 the unit was then switched to SBU mode at which time the grid no longer plays a role supplying loads and all loads are supplied by the off-grid PV and battery.

 

[LuxOfTheIrish]

Aha. Thank you for all the kind and excellent replies.

Unfortunately the after sales technical support hasn't been great but i took that chance when purchasing. The digital manual and the print one were for two different models. Other than that I'm pleased with the operation.

Following your replies I did some comparisons and found these pics on the website:



I purchased the inverter which has the image with no backfeed (Anenji 5.6kw). The one with the green backfeed arrows was slightly more expensive so my assumption is that it has functionality to match the wave while my version draws power and then outputs its own wave. It has a bypass mode function which kicks in when there is no PV or battery which I assume is actually the grid wave. As I understand it then it is a hybrid off-grid as opposed to a hybrid grid-tie.

Currently (pardon the pun) I am operating off-grid (I just didn't connect the AC input. The AC output is on a circuit isolated from the mains/utility). Do you think it is safe to connect the grid to supplement the (isolated from grid) loads without any backfeed? I can't have any at all, not even the occasional 20w when some large appliance powers on or off. Perhaps one way to test it is to disconnect PV and batteries, connect the utility and set the inverter frequency to something different from the grid then test the output... though I don't have an oscilloscope.

Another option is to connect the mains up to the batteries with a transformer as the DC conversion will certainly not backfeed. The DC conversion would be wasteful however.

Thanks for the help and advice, further thoughts on backfeeding appreciated.