Force disconnect from the grid when unstable - how to?

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footswitch asked Apr 10, '24

Force disconnect from the grid when unstable - how to?

Hi, we have an installation with 2 Quattros 15000/48 in parallel, with ESS assistant, controlled by Node Red on the Cerbo.
1x SmartSolar MPPT RS 450/100-Tr
1x SmartSolar MPPT 100/20
1x ABB/Fimer 4kW AC coupled PV (on AC-out)
LOM disabled (external Ziehl), the setting is Other: not compliant to any grid code standard.
Around 40kWh LiFePO4

Everything runs fine except 1-2 occasions every day or night, I can only deduce the grid becomes unstable and the Quattros really struggle with this (loud humming noises), but they don't disconnect from the grid. During these episodes, everything at the house dims/beeps/flickers. This goes on for 2-3 minutes and then returns to normal.

This is kind of random because it happens both with a 30% battery and sunny, or 60% battery at night. Battery SoC and PV power don't seem to matter.

If I disconnect from the grid manually, the system immediately becomes stable, and if I reconnect too soon, it becomes unstable again.

Is there a way to detect this and force disconnect for a few minutes?
I can't seem to detect this under Node Red because the readings aren't realtime as you must know, they only refresh every few seconds.

There are many variables at play and I'm not sure where to start, because I don't know how I could simulate these occurrences to test the behavior.

Thanks in advance for any input.
Cheers

MultiPlus Quattro Inverter Charger ongrid

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Answer 1 · 2024-04-10T17:56:17Z

CristiMV answered · Apr 10 at 05:56 PM

I would start by analyzing the advanced reports and see exactly what happens when the grid is unstable...voltage, frequency....

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footswitch commented · Apr 12 at 04:51 PM

Maybe I didn't understand what you are suggesting.
In the advanced reports the data is only 1 row per minute. Not enough resolution to see what's going on.

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Answer 2 · 2024-04-10T18:10:39Z

vicens answered · Apr 10 at 06:10 PM

Yo quitaria la funcion UPS. Que consumidores hay cuando passa esto?

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Answer 3 · 2024-04-10T19:25:25Z

Alexandra answered · Apr 10 at 07:25 PM

@footswitch

Ups function should not be checked with the ESS assistant as @Vicens mentioned.

I would first start with firmware upgrades on all Victron parts, then go from there.

Be aware that some parts of node red (depends on how far back you are in Venus OS) will be wiped out.

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Answer 4 · 2024-04-12T16:56:48Z

footswitch answered · Apr 12 at 04:56 PM

@Vicens and @Alexandra both of you are suggesting disabling the UPS function. Won't the switchover time be too long in case of a power failure?
How does this option affect the Quattro behavior with grid instability? The only descriptions I find are about switchover times.
The description also says it's likely that the inverter will be switching over if there is instability, which is what I wanted, but it doesn't switch over.

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Alexandra ♦ commented · Apr 12 at 06:09 PM

@footswitch

No. It does not, unless your battery or DC cannot do surge currents.

When the ESS assistant is run, you will see that UPS function is disabled. So you have basically re enabled something conflicting with it.

ESS really means the inverter system is your primary power already. Grid is there to fill in.

UPS now means grid is primary power, battery in case of failure to stay in parameters. And your voltage range is wide. Tighten those up as well it helps with faster rejection. The other thing is the LOM detection I assume you are using grid code other there?

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footswitch Alexandra ♦ commented · Apr 12 at 07:32 PM

Ok, makes sense, we will disable the UPS function and see how it goes.

We did have a problem with low [grid] voltage at night (pulling from the grid), but that went away last year; now it's ok to set maybe 200V as a minimum for AC in.

When it was first installed (4 years ago), the Quattro was misbehaving badly, so we were asked by Victron to disable LOM detection and install a Ziehl Anti-islanding relay UFR1001E. When this was done the grid code was set to "other"/"no code".

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