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Victron QUATTRO 48/5000VA with SMA 5000TL Inverter in Island mode

Hi, I have an existing grid-tied SMA inverter (SMA 5000TL) and 2 strings of 13 panels for total of 6.5kW. I want to add storage and am considering the QUATTRO with 4 x Pylontech US3000 batteries (@48V nom).

The main aim of the exercise is to be self-sufficient in case of extended/indefinate grid outage. I am no expert, but my reading suggests that the Victron QUATTRO would provide a mini-grid on the AC-OUT-1 and that the SMA solar inverter would run 'normally' on this channel regardless of whether the grid was connected or not.

Assuming that the above is correct, would the SMA inverter connected in this way be a stable and reliable configuration. I ask this because I have read some posts/articles that indicate that there are situations where the inverter may go over-voltage and shutdown the QUATTRO.

Is this a potential problem, and what would be the recommended way to deal with this?


Note, the loads would include 1000W and 1500W pumps (bore pump etc), inverter aircon, fridges and freezers, lighting and misc.


thank you,


Ron


ESSsolarAC PV Coupling
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ejrossouw avatar image
ejrossouw answered ·

Hi @rrroonn "When connected on the AC out, the factor 1.0 rule must be adhered to. There are no exceptions to this. Also use the factor 1.0 rule in countries where the utility grid rarely fails; and also when connecting a Fronius grid-tie inverter on the AC out, and employ- ing 'Zero feed-in'." Also note, the Quattro is 4000W at 25 degrees C and derates the higher the temperature.

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rrroonn avatar image
rrroonn answered ·

FYI,


Had this happen today.

SMA was outputting 5000W, battery SOC was 100% and grid supply dropped. Shortly thereafter the battery issued a high voltage alarm and shutdown leading to total loss of power.

As I have an independent automation system, I added a single 12V contactor to the SMA inverter A/C feed; with the control logic implemented in node-red. Hopefully the last time this happens now.

It seems like something that is worthy of implementing as an "assistant" so that a single contactor solution can be used.

Anyway, thank you @Riaan for the prior advice.

Ron

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Riaan Barkhuizen avatar image
Riaan Barkhuizen answered ·

Hi @rrroonn

In essence, you have a plan that can work. Please note that overvoltage issues on the battery may develop when the batteries are fully charged and the building load drops away leaving the system with an over-supply of solar power. Running in off-grid mode frequency shifting will kick-in if set up correctly, but oftentimes this control is not fast enough.

To overcome any control issues relating to overvoltage you need to use the output relay to physically switch on/off the connection to the grid-tie inverter. The output relay contact itself cannot be used as part of the main circuit but the output relay contact can be used to drive a coil on a contactor with an adequate amp rating (say 30-40amp in your case). You can setup that contactor to be controlled by the output relay in a generator start/stop configuration. Essentially you would have the relay output on whenever the battery is below 99% SoC and switch it off again once the battery is above 99% SoC. WIth this method you would lose 1% battery capacity but you can be sure that the pylontechs will not be over-charged.

Hope this helps.

Best Regards

Riaan


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Thanks @Riaan for the quick and helpful response.

I would assume that your proposed solution could be implemented to only switch this inverter relay" off when in the grid is not connected? Otherwise I would lose the feed-in ability? I guess that this is a programmable/scriptable relay that can essentially do whatever you want (within reason)?


thank you,


Ron


Correct, if you still want to feed we, while controlling you can install two contactors in parallel. One contactor is supplied from the backup side (this one runs from the generator start stop as a control). The other contactor coil is supplied from the grid side, so if the grid is on the pv inverter is also on.