Multiplus-II 10000kva AC Input random overload and negative amps

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hanco asked Mar 6, '23

Multiplus-II 10000kva AC Input random overload and negative amps

I have a Multiplus-II 10000kva, 4x BYD batteries (400ah), RS450/100, Cerbo GX.
All devices are on the latest firmware.
ESS is activated with all VEConfig settings done as per Victron/BYD specifications.
Grid feed-in is off, grid setpoint is currently at 200W.
I'm in South Africa, Cape Town.
This is a new installation (1 week old).

About once a day when AC Input is connected, I get an "Overload L1" warning, and from inspecting VRM it appears to coincide with negative amps reported on the AC Input. This normally results in swings in the AC Input current between positive and negative Amps. At the same time the Multiplus's state changes to passthrough, even though there is ample battery and PV available to handle the AC Output load. In the example below the AC Output load was only about 500W when the Overload warning came up.

In the example above, the system returned back to normal operation on its own, but I've had other cases where this happened where the AC swings from negative to positive continued and seemed to get worse, resulting in loud noises from the multiplus and lights flickering in my house. When this happens, I disconnect AC Input, and the system then becomes stable immediately. When I then reconnect AC Input, the system typically behaves fine again.

Does anyone know what could be causing this behaviour ?

Multiplus-II input current

vrm-img1.jpg (37.6 KiB)

vrm-img2.jpg (209.8 KiB)

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Alexandra ♦ commented · Mar 06, 2023 at 05:03 PM

@Hanco

What is the LOM setting for the input you are using?

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hanco Alexandra ♦ commented · Mar 07, 2023 at 07:50 AM

@Alexandra

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veconfig-grid-setting.png (50.5 KiB)

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Node Red Space

Answer 1 · 2023-03-07T08:19:27Z

myvicrocks answered · Mar 07, 2023 at 08:19 AM

Try rather using the OTHER grid code for ZA (from ZA as well) - whilst the grid code does provide the "correct" settings with all the loadshedding those values are not really accurate. Those NRS codes for ZA is when the grid is stable - which you well know ours is far from that.

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hanco commented · Mar 07, 2023 at 09:03 AM

@myvicrocks what would you then recommend for the AC Input related settings ? frequency range, AC low/high connect/disconnect.

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myvicrocks hanco commented · Mar 07, 2023 at 10:19 AM

I use the "other" option in that drop down as instructed by my installer. It has a broader range of parameters going off memory but... example:

1. Grid drop is 185V

2. Grid over voltage 265V

3. Frequency range 47hz to 67z

Its very broad and also potentially very dangerous the problem with our grid in ZA is its not stable as per the ZA code thats in the system.

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hanco myvicrocks commented · Mar 07, 2023 at 10:40 AM

I see. I was actually thinking of making the ranges narrower if anything, rather than wider. Since I'd rather switch to Inverter mode earlier if the grid gets unstable at any point.

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