question

Can I recommend isolation by turning off all breakers that are not the lights.

I have a similar issue with my house, pulsing lights but it’s definitely because of one device in my setup. The device has a technology called power pulse, but even with that drivable it still occurs as the loads kick in/out.

it might be in your situation that there’s more than one device.

failing that, check your neutral lines maybe a common loose cable.

Hi @jleverf

The first thing I would think of with the low voltage state getting to 200V is that the inverters are hanging on to an AC input for too long. Adjust the AC input voltage acceptance limit to increase the minimum AC input voltage higher, say 215V for example. I don't think that's related to the core issue at hand, but still a good idea.

You've isolated the most common cause of flickering which is the AC PV. This is most common when the AC PV production is equal to the AC load, and the Quattros and Fronius are 'hunting' between idle and inverting (which they do by raising the voltage slightly), which leads to shifting of the voltage around. But I will rule that out for further troubleshooting for now as you are saying that it's already been isolated.

The next step, which is annoying but necessary, is to physically switch the units so that they are driving different phases.

This will help to isolate the issue between a physical hardware problem inside one of the Quattros, or some interaction between any arbitrary Quattro with the site wiring.

If the lights continue to pulse on phase 1 after physically connecting the Quattro from phase 2 to the phase 1 AC wiring, then it's far less likely to be a physical hardware issue, and far more likely to be something else (a bad connection or some other interference).

If switching the units resolves the issue, it hopefully solves your immediate problem. I could still be a wiring issue, that was resolved when re-wiring, or an issue inside the Quattro itself. It doesn't necessarily arise to the level of a replacement, report back with the results.

Be aware of all the safety implications on this sort of procedure, I am not sure what kind of loads you're running, but make sure everything is programmed correctly so that the correct phase sync is maintained if that is necessary.

Also agree with the comment above that the neutrals should all be checked around the site (depending how you isolated your loads in your other troubleshooting, this might not have isolated a loose or neutral wiring issue).

@jleverf

Besides the suggestions by @Guy Stewart (Victron Community Manager) and @h2009 ...

The thing I see there is it is not inverting only? I see grid feedback. It can only do that when connected to grid. So synchronised to grid voltages.

LED lights with some of the cheaper power supplies don't like anything but 220v to 235v. So related to voltages definitely.

If you switch off the input breaker does it stop? That is true inverting where the system gets to decide for itself what to do instead of synchronization. They system should output 230v per phase when physically disconnected from grid. If not. Dig deeper.

@Guy Stewart (Victron Community Manager) - Posting here as I couldn't post as a comment at this time.

Hi Guy, thanks for getting back to me! Apologies for the essay, I'm just trying to provide as much context as possible. Please see my comments below.

AC Input Voltage ~215V:

• We previously had this set as standard at 215V, however it was causing issues in installations with Quattro's installed. We found that with some load transitions on the genset, the volts would tank down below 215. The inverters would follow it the genset down to 215, then reject it for an undervoltage when it dropped under and try and carry the load themselves. Since they were working in power assist, they couldn't carry the load, and so they tripped on overload.
• From what I've seen there appears to be a difference in the recovery of Quattro's vs. Multiplus II.
• With the Multiplus', if this happens, and then the load is dropped down to a non-overload level, the inverters will come back online and recommence powering the load.
• With the Quattro's, they appear to seize up when they go into a fault state, and the load needs to be dropped and all inverters reset (with the switch) for them to come back online. This would happen in the genset undervoltage case, and site power couldn't be restored until the inverters were reset manually.
• By allowing the inverters to ride through the transition, they could keep the genset online and maintain power.

AC PV:

• We haven't come across this specific case yet, but we were having a similar case where we needed to have the genset running to handle peaks, but the batteries were at 100%. The load was bouncing around the input current limit, so the inverters were constantly jumping between charge and discharge which seemed to be making the lights flicker.
• So far I've only been able to solve this manually by reducing the input current limit during these times so the inverters have to discharge a little (~1kW/phase). I'm considering trying to automate this with node-red when I find some time, with something like: when SOC>95%; input current = 0.8 x output current; until SOC<80%, but that's work for the future!

The next step, which is annoying but necessary, is to physically switch the units so that they are driving different phases.

• I was thinking that it could be a hardware issue with the master, that was potentially shifting downstream to the remote units.
  • Do you know what data is passed by the master? I.e. do the remote units try to track the master voltage, or does the master just send a delayed firing signal for the remote's FETs?
• On this point, there are no three-phase loads on site, would it be possible to just re-program the units to shift the master across?
  • Noting that the AC Input and Fronius Inverters would be locked-out when doing this, so it would only be the inverters driving the loads.
• As another possibility, since they are all single-phase loads, would it be possible to shut down 2 inverters and reprogram the remaining one as single-phase to see if the problem persists in isolation? If this is possible, I could cycle through each inverter to see if this isolated the issue.

If the lights continue to pulse on phase 1 after physically connecting the Quattro from phase 2 to the phase 1 AC wiring, then it's far less likely to be a physical hardware issue, and far more likely to be something else (a bad connection or some other interference).

• Just a note on this point: the pulsing appears to be happening on all phases but at different times. For instance, Lunch Room 1 will be pulsing for ~1min, then everything might be stable for ~5 mins, then Lunch Room 3 will be pulsing for ~1min. I didn't manage to get a load-phase map, but I had the feeling this was phase-related as it was switching between random huts at different times. I've got high hopes this is the case, because if huts on the same phase are pulsing like this at different times, there's a chance the site is possessed by a ghost.

If switching the units resolves the issue, it hopefully solves your immediate problem. I could still be a wiring issue, that was resolved when re-wiring, or an issue inside the Quattro itself. It doesn't necessarily arise to the level of a replacement, report back with the results.

• Physically switching the inverters might be quite difficult under the site conditions. In trying to avoid this, I'd hope a solution might be too:
  1. Get our tech to re-torque all power cabling, specific attention provided to the neutrals.
  2. Ask site to double-check/re-torque all their neutral connections.
  3. Reprogram/shift the master inverter across and run the inverters in isolation to see if this delivers the desired solution.
     1. Test whether the issue is with the master.
  4. If 3 fails to provide any insight, run each inverter as a single-phase in isolation.
     1. Verify each inverter works in isolation.

Be aware of all the safety implications on this sort of procedure, I am not sure what kind of loads you're running, but make sure everything is programmed correctly so that the correct phase sync is maintained if that is necessary.

• There shouldn't be any issue on this point as site loads are very simple and no three-phase loads. Ideally, when this work is being done there will be no one on site anyhow.