question

@MMH

I had a similar problem when only one phase was missing (I think it was L3).

https://community.victronenergy.com/questions/129044/3-phase-system-and-1-phase-missing-what-should-hap.html

System switched to inverting.

Battery was not full (57%) but Fronius was frequency shifted off.

The only solution was to disconnect the system from grid on all 3 phases.

When I did that Fronius came back to life.

Later on, Victron Service confirmed that this is expected behavior.

Hi all, help appreciated again for this system running in a rural african hospital;

Following up on above, the issue seems to be more complicated then low voltage on one grid phase.

I checked the VE.Bus monitor when:

A. state 105 error appears on fronius and B. At the same time Quattro's refuse to connect AC-input 1 (grid in our case, genset sits on AC-input 2).

VE.Bus monitor in this case shows that AC1 voltage is perfectly normal 220V on 3 phases with normal frequency-in of 50.1 Hz. So we can't blame the utility company.

Frequency-out is 52.9 Hz - I suspect due to upregulation by the Quattro to reduce PV power.

Result: no PV (Fronius downregulated through frequency shifting) and no AC-1 (grid) input as frequency in and out do not match! this unhelpful situation exists for many hours every day mostly during sunny hours.

My only solution until now is to close main grid switch and make this an off-grid system, then everything works well.

All modbus settings in Fronius datamanager are correct, grid-feed in is not allowed on GX device settings (ESS) and works well.

System has 6x15Kw fronius symo on AC-output and 2x15Kw symo on AC-input.

6x Quattro 15kW, all properly sized cabling done by professionals.

1x Fronius and 1x Carlo Gavazzi grid meter and Cerbo as GX device.

Other details above.

I tried:

- allow grid feed-in with limit of 5000W, this made no difference

Considering now:

- Delete ESS assistent and use the ignore AC1-input virtual switch. However shame to lose all good ESS features, also not sure if this would help.

Any ideas?

A second problem is that our new 65kVA diesel genset is accepted on AC2-in, without the GX device (cerbo) connected. The moment I plug in the Cerbo, it disconnects. Suspecting again that the ESS assistent does this as there seems to be no physical issue with the genset.

Here I tried all options for genset issues as per documentation (weak AC input checked, UPS unchecked, accept wide frequency checked) but not yet 'disable LOM on AC-input 2.'

Comments on these two issues would be much appreciated. Thanks

@MMH Regarding the frequency shifting issue shutting down the PV inverter, have you come across this post https://community.victronenergy.com/questions/8792/multiplus-485000-with-pv-installed-45kw-output-hz.html

I found your post because I have a similar problem with a simpler system using a Multiplus 2 (ie only one ACinput). This morning I found his solution of reording the Assistants, ie move general flag to position 1 and ESS down to position 2. It has worked for me!

All the best,

David

Hi @assyntdavid assyntdavid

Thanks very much for your input, much appreciated. The issue was resolved for us by upgrading our connection to the transformer. We went from 3x16mm2 to 3x100m2 aluminum over a distance of 300m, renewed the fuses at the transformer and upgraded the connection to it. This solved the issue - so it was the poor quality grid connection is what caused it. We only run the ESS assistant, no others.

Since we very often have undervoltage in Malawi we also installed a contactor +voltage window regulator before the system around the same time. This effectively results in a grid-lost situation when there is undervoltage so that the PV inverters happily work for us on the micro-grid. All in all it took a lot of money and time but we're happy how it works now for our hospital.