question

Alexander Ushakov avatar image
Alexander Ushakov asked

Do I have to install ESS into each Multi? (I have 2 in parallel)

In "Changelog assistants" file I see, that ESS now suppports limitting FeedIn power:

Release date: January 24, 2020

Supports limiting the FeedIn power. (Starting from firmware revision 469)

I updated my MultiPlus 48/5000/70-100 to 2624469 firmware version, but I cannot find in ESS menu on CCGX panel the line, in which I could limit the FeedIn Power.

Maybe it does not work because I have 2 Multiplus devices in parallel?

What I have also found out, that though I disabled FeedIn, it still feeds energy in, taking it not only from my Solar panels, but also from my batteries. Isn't it strange?


firmware update
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2 Answers
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Alexander Ushakov

Can you please try swapping master and slave unit (in software) to see if the behavior changes?

for the rest, please check all that is written here:

https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems

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Alexander Ushakov avatar image Alexander Ushakov commented ·

That was an unusual behaviour during that one day only. I swapped Master and Slave units and updated to the last firmware 2624473.vff.

Now after I checked whatis written here (https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems), I find it strange the following saying:

Note: Do not over-dimension the AC cabling. Using extra thick cabling has negative side effects.

  • Technical background: In a parallel system the AC current should be evenly distributed through all paralleled units. When the resistance in the cabling is very low, a small difference in resistance results in a large relative difference.
    This results in bad current distribution.
    An exaggerated example:

    • Using 2 units (A and B) parallel and using extremely good cabling one might achieve a total resistance for Unit_A of 0.0001Ω and a total resistance for Unit_B of 0.0002Ω. This results in Unit_A carrying twice as much current as Unit_B although the resistance difference is very small.

    • Using the same 2 units in parallel with bad AC cabling one might end up with a total resistance for Unit_A of 15Ω and a total resistance for Unit_B of 16Ω. This results in a much better current distribution (Unit_A will carry 1.066 times more current than Unit_A) even if the absolute difference in resistance is much bigger than in the previous example (1Ω vs 0.0001Ω).

I have 2 Multis of 5KVA each and they are connected with each other with 6 mm^2 cables, each exactly half a meter long, through to the joint point. Is this 6 mm^2 cable too thick for my system, so that it may cause some unpredictable operation? And in order to prevent it I should use cables of different length. When I had one unit in my system it works a bit more better, than now two units work together (switching to inverting mode became more frequent - I have unstable and weak AC input).


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laurentiupitran avatar image laurentiupitran Alexander Ushakov commented ·

hello,

already seen this problem; is also in different topic here.

please,see attached file , in an ESS system with 0 injection( zero injection).

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grid-injection-0.png (68.6 KiB)
Alexander Ushakov avatar image Alexander Ushakov laurentiupitran commented ·

Where can I read about it? Could you give a direct shortcut, please?

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laurentiupitran avatar image laurentiupitran Alexander Ushakov commented ·

hello,


you can use my e-mail addres .

the 2 graphs are from today, from my system; second one is per phases R,S,T and total.

in ex 3 you can see how is react ESS system to a demand of house needed.

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ex-1.png (103.1 KiB)
ex-2.png (117.7 KiB)
ex-3.png (143.5 KiB)
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Yes, ESS assistant is required on all units in multi-unit installations.

Zero export from Victron MPPTs and Fronius PV inverters is currently supported.

Variable Feed in limiting still requires additional development work before available, the recent MultiPlus firmware update is only one part of the compatibly updates required. GX devices also need a new, as yet unreleased version as well.

More information, and a general announcement will be made on the blog, along with training and documentation when it is available and ready for use.

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Alexander Ushakov avatar image Alexander Ushakov commented ·

Ok, does it mean that behavior of my system is abnormal, and it is not supposed to feed in, taking energy from batteries?

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ Alexander Ushakov commented ·

If ESS is only installed on one MultiPlus in a parallel system then it is not configured correctly, and will not behave as expected.

Please make sure you have read and understood the 3 phase and parallel manual (this requirement is described there).

Making sure that everything is installed and configured correctly is the first step before investigating strange behaviour.

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Alexander Ushakov avatar image Alexander Ushakov Guy Stewart (Victron Community Manager) ♦♦ commented ·

My ESS is installed as written in Victron's manuals - in each Multi. Once again - do I understand it right that it is abnormal when Multis feed energy in, taking it from battery?

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