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philr-1 asked

Parallel Multiplus in ESS not accepting the grid

New install consists of two Multiplus 2 (5000W 48v) with six Pylontech US3000 and Cerbo. Output will be from AC Out 1.

Configured for single phase parallel operation, with ESS assistant set up on each inverter. Starts up and runs correctly with both AC outputs connected via equal length cable.

Problem starts when i try to connect the grid to AC In. I have used two equal length cables to take grid power to each Multiplus AC in, but applying grid power causes inverters to slowly cycle through connecting and disconnecting, or at least a sequence of relay cluncks that continue to cycle with a variety of flashing LED front panel lights. Obviously something is wrong.

Q1. When using this setup, ie parallel Multi's and ESS, should grid be connected to both Multi's AC input or only to the Master Multi?


Q2. If I have connected the grid correctly, any suggestions where to look to get the system working correctly?

Thanks in advance

ESSmultiplus in parallel
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Alexandra avatar image Alexandra ♦ commented ·
@phil.r
If something was wrong the cerbo would give out an error.


It may be just simple grid rejection as it is out of range, or the wiring has an issue.


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philr-1 avatar image philr-1 commented ·

I am re-opening this issue.

The system has been working fine, after pulling the data cable linking the two Multiplus 5000's out of the trunking and putting it in its own trunking. All worked fine, indicating just how ropy Victron's really are.

But then the grid went down for a few days. The system continued to operate without grid, drawing energy from solar during the day, then batteries at night.

And then grid came back again, and the Multiplus's would not sync with the grid. I was called out to investigate, I checked gridvoltage 220vac with a variation of around 5v over time, frequency 49.8 Hz, steady. Could not do anything to get it to connect.

Eventually, I removed the ESS Assistants from each Multiplus, fired it back up again, it went into charge mode to top up the batteries when I turned on the grid supply.


Nothing else changed, exact same wiring, just without ESS Assistant works fine, add in the ESS Assistants, what had been working for a couple of weeks, now no longer works


I have one solution which I intend to implement going forward, that is simple and effective, not to use any more Victrons. But if Victron technical staff have a better solution, now is the time to communicate

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Kaspars avatar image Kaspars philr-1 commented ·
Hello. Have you found a solution or at least a reason to this issue ?

i am having exactly same issue with two multiplus-ii 5000 48v in parallel with ess.



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14 Answers
philr-1 avatar image
philr-1 answered ·

Thanks Alexandra. I have checked and double checked the wiring, also disconnected both AC inputs (from grid) and turned on grid power and checked both have 230vac and are line and neutral as expected. All good. It may be grid is out of range, but I checked both the voltage and the frequency of the grid, they measure correct and close expected.

I assume from your reply that grid should be to both Multi's at their AC input via equal length lines, which is how I have connected them.

I have thought to remove the parallel settings, run just one Multi reconfigured for ESS and test again. This would verify if its related to the ESS assistant setting or if related to the parallel Multi's setting.

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Rob Duthie avatar image Rob Duthie commented ·

Have you setup the grid parameters settings in the Multiplus using VE configure?

Both AC inputs should be connected in parallel with the same lenght input cables to the supply feed as well just like the outputs are done.

Regards

Rob D

NZ

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philr-1 avatar image
philr-1 answered ·

Another question related to above: how important is the equal length cabling when running more than one Multi? I ask in terms of accuracy and also power. For example, I have relatively short cables from Multi's to batteries and Multi's to AC inputs and outputs. All are typically less than 0.8 meters. To what accuracy should the cables be matched? 5cm? 1cm? 0.1cm?

Also would it be correct to say that any ill effects resulting from cabling of enough difference in length to cause problems, would only be present when significant power is being drawn from the system, in other words, ill effects would not be noticeable when system is in idle and there is no, or minimal load ?

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Alexandra avatar image Alexandra ♦ commented ·
@phil.r

Because of VIR relationship and its workings in the whole setup, longer (and sometimes thinner) AC cabling helps with balancing wiring.

And it will also help to have them as close as possible. Lay them out with each other, you have to be pretty close for a good setup with awesome current sharing.

DC and AC need to be balanced.

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philr-1 avatar image
philr-1 answered ·

I have read this: https://www.victronenergy.com/live/_media/ve.bus:rva_-_theory_on_wiring_large_systems.pdf

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marekp avatar image
marekp answered ·

@phil.r

You should start simple.

Try u run one MP at a time and as a plain system without ESS assistant.

Than make it parallel and load ESS assistant only when everything works.

Cable lengths diferences on AC-in and on AC-out in parallel setup would not hinder the system work. They will cause power transfer imbalance between master and slave. To have imbalance it must work first.

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philr-1 avatar image philr-1 commented ·

Hi Marekp

Good idea. I have run Multi's in parallel and they function fine. Problem arises only when applying AC in. I can remove the ESS Assistants and try running them in charge mode. This will verify the problem is with ESS Assistant or related to parallel single phase setup. Thanks, will try this when next at site and report back. I suspect the issue is with ESS, but thats just a gut feeling :-)

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philr-1 answered ·

Dear Marekp. I have now been able to run some more tests. Reset one of the Multi's as a stand alone single device. Installed ESS assistant, and configured for Pylontech batteries, all works just fine. No problems.

I then reconfigured for two Multi's single phase, both with ESS assistant, but this time, they run for about 15 - 20 seconds, then some relays change over, the slave warns of overload, the fan comes on, and relays clunk about, and it tries again.

I then removed the ESS assistants and ran them just as two parallel Multi's without ESS. but with AC In to both. This time all worked until I applied AC in which then attempted to charge the batteries (which are fully charged so no appreciable current drawn) and similar problem arose, overload warning and fan, and then relays. No notifications anywhere, no error messages.

System is very simple, AC in connected together by equal length cables of same rating, same for AC out and same for battery in, coming from nearby common bus bar.

It seems this is not an ESS issue, but a parallel Multi config issue

I used VE Bus System Config to set up the two Multis in parallel single phase and also to then set up each with ESS Assistant.

Settings for all the above were identical, ie BMS external, all voltage settings the same for all above situations.

Phil

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marekp avatar image marekp commented ·

@phil.r

Did you try seting up single MP-II without ESS assistant but with AC-in, battery and AC-out connected?

Can describe all your steps that you took connecting two MP-II in parallel?

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philr-1 avatar image philr-1 commented ·

Yes, I reset one of the Multi's to single MP-ll, removed data and all power cables from the second Multi, then set up as normal inverter. All good. i then applied power to the AC in and it functioned correctly. This is a factory setting single Multi-ll set up for Pylontech batteries.

I then added ESS Assistant, and configured for the one Multi in usual way, setting for the Pylontechs. All worked well, no problems, it functioned perfectly in ESS mode.

I then removed the ESS assistant, used VE bus Config to set up two Mult's in parallel (single phase same Firmware) both without ESS Config. I mirrored the settings on the slave multi by accessing VE Config by selecting the appropriate Multi via the VE Bus Config app.

All worked well until I turned on the grid supply (AC In) which was connected to both Multi's via equal length cables. This is when the problem takes place, as if they are trying to deliver excessive load or powering each other, but only when AC In is supplied.

Same AC in with just one Multi works fine, its 50Hz and 229v, well within spec


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marekp avatar image marekp commented ·

@phil.r

Did you connect them with RJ cable between VE.bus sockets?

Did you run ESS setup individually on each MP-II or did you set one up and copy setting to the other one?

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philr-1 answered ·

Yes, when running both Multi's I use Victron RJ45 cable to connect data together, as per recommendations, ie, nothing else on end of the string

Yes, run the ESS set up individually, starting with the Master. Upon configuration of ESS Assistant, there is an option to write to both devices, but it it fails to write to both with error message, so I have to write to one, then config ESS second time on the Slave

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marekp avatar image
marekp answered ·

@phil.r

Just to be sure that both MP-IIs are working, maybe try the single setup with the other MP-II as well.

How you know which one is master and which one is slave?

How are the LEDs when you have them connected as a parallel?

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philr-1 avatar image
philr-1 answered ·

I can try the other in single set up, will do that next site visit.

Master and Slave are easily identified in set up and also by test in VE Bus Config - ie flash the led's

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marekp avatar image marekp commented ·
@phil.r

When you have them parallel, what LEDs show on each MP-II?

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philr-1 answered ·

I am not at site now, but from memory, the Master has inverter green LED on continuous and the Slave has same LED flashing, but that is my memory which I know is prone to error :-)

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marekp avatar image marekp commented ·

@phil.r

Master's LEDs shows status (mains on or inverter on constant and battery status constant) but slave is alternate blinking mains on and inverter on.

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philr-1 avatar image philr-1 marekp commented ·
It may have been Slave alternate blinking mains and inverter - I know there was blinking and no orange or red LED's, but I cannot be certain. BUt now I know and will check when back at site on Saturday. BTW, thanks so much for your patience and help. I install a few systems just for friends locally, usually no problem, I have installed a couple of single Multi's with ESS Assistants without problems. I have also installed a few Studer systems, I know a little more expensive, but seem to have fewer set up issues
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marekp avatar image marekp philr-1 commented ·
@phil.r

I have 3-phase system with 2 MP-ll parallel in each phase. I had some problems with load balancing in each pair. Problem was with different hardware revision between MP-lls in a pair. Never had a problem with two MP-ll cooperating in the pair.

Now I am getting from time to time errors #11, #8 and #17.

#11 and #8 are phantom errors in my system caused by the glitch in the MP-ll relay testing procedure in multi inverter setup (6 in my case).

#17 I fixed by moving RJ cables away from AC wires. I hope. :)

Do you have a reason for going parallel with two MP-lls 5k instead installing one MP-ll 10k.

It would be more stable system.

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philr-1 answered ·

Probably should have done the Multi 10k, but I bought was was available from local supplier

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Rob Duthie avatar image
Rob Duthie answered ·

Multiplus2 10k not grid approved?

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philr-1 answered ·

The solution turned out to be the proximity of the data cable connecting the two Multiplus inverters to their power cables. I had placed data cable in same trunking as the AC in and AC out cables, a rather too small trunking. After endless faultfinding exercises, finding nothing setup incorrectly, I tried this suggestion and took the data cable out of the trunking and let it lie away from the power cables, and all is now working as it should. Thanks everyone

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Kaspars avatar image
Kaspars answered ·

Hello @phil.r did get to the solution for this issue? i am having almost identical setup with the same problem.

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philr-1 answered ·

kaspars - see my comment dated 4th May 2022 at 12.29. I found this allowed the system to work, I took very great care to ensure linking cables were same length, exact same length. I reduced cable size on AC side to borderline schedule, I read this helps due to increasing linkage resistance, and I removed the data cable from the trunking carrying the power and DC cables. It worked, and has been working, but I cannot say I am satisfied - the victrons make a lot of varying humming noise. Lack of support from Victron, a very iffy performance and terrible patchwork of data protocols have led me to make the decision to abandon Victron, I now install other brands, Studer being my favorite. A Studer parallel system in ESS type mode is so simple, seamless and solid to set up, I would never go back to Victron


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