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sgrigor1 avatar image
sgrigor1 asked

Parallel Multiplus II problem while AC IN is connected

Hi, I'm facing an issue in parallel configuration of EasySolar II GX and Multiplus II invertors. When the Grid is connected, the invertors started to inject in grid. I played w/ different values of Grid Set Point but no change in behavior.


Hardware system:

- 1 EasySolar II 48V 5000/70

- 1 MultiPlus II 48V 5000/70

- 1 SmartSolar MPPT 250 70 Ve.CAN, connected thorough VE.Direct

- 1 SmartSolar MPPt 150 35 connected thorough VE.Direct

- 1 battery LiIon 48V with Can BMS ranges (53V - 60.8V)

In standalone, both invertors are working well.

I played w/ different ESS assistant configs w/ and w/o BMS but still injecting.

multiplus in parallel
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nickdb avatar image
nickdb answered ·

What are the serial numbers of the two inverters?

If they are far apart (look at first four numbers which represent year and week of manufacture) then this is most likely caused by hardware revisions being too far apart.

Change the master to be the newest inverter, this sometimes helps.

Also, make sure all cabling is symmetrical between inverters, grid, loads and batteries.

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Michelle Konzack avatar image
Michelle Konzack answered ·

Maybe you should show us the schematic how the stuff is connected to each other


Do you realy run the EasySolar and the Multiplus parallel?

How did you connect them to each other?


Rewireing the EasySolar?

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sgrigor1 avatar image
sgrigor1 answered ·

parallel system.jpg

I configured them w/ VictronConnect and VE.bus Quick Config. I'm sure they are in parallel other wise you can't connect AC-IN and AC OUT together. Moreover, they are working OK w/o grid, I increased the load to 7000KW and they were OK.

All the cables have the same lenght between inverters. I measured the amps and are similar.

I'll look to serial number and try to asing the new one as master. Currently I have EasySolar as master and I bought it last year compared to Multiplus II that was purchesed few weeks ago.


parallel-system.jpg (100.0 KiB)
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sgrigor1 avatar image
sgrigor1 answered ·

These are S/Ns

EasySolar HQ2105279IV

MultiPlus HQ2314MYP6A

There are 2 years difference

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nickdb avatar image nickdb ♦♦ commented ·
Those are a bit far apart, if changing masters doesn't help, you may have a problem.

There was a powerpack change from HQ2116 and old and new don't always play nicely together. Yours is older than this so you have two different revisions of the powerpack.


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sgrigor1 avatar image
sgrigor1 answered ·

I swaped the roles but there still is a power consuption from grid this time.

1693489250784.png


1693489250784.png (134.2 KiB)
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nickdb avatar image nickdb ♦♦ commented ·

Yours is behaving the same way my mixed powerpacks did. If you drop the setpoint to negative you should be able to cancel a lot of that out.

Only solution is to get two units that are on the same powerpack, I suggest you discuss with your supplier.

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sgrigor1 avatar image
sgrigor1 answered ·

if I set the grid setpoint to -200, the oscilation is between -100W +100W, somethimes more, sometimes one digit. But not sure if it's OK to put this value.

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nickdb avatar image nickdb ♦♦ commented ·
There’s no issue setting it negative.
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sgrigor1 avatar image
sgrigor1 answered ·

I think I have an issue w/ parallel AC cables connection. I use 0.8m of 6mm2 segment wires for parallel connection. The resistents is too low so the invertors are unbalanced.

I'm thinking to use 2m of 4mm2 segments, is it good enought?

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nickdb avatar image nickdb ♦♦ commented ·
That can affect balance, would be surprised if it changes the backfeed. You could always use a longer run of the existing gauge.
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Michelle Konzack avatar image Michelle Konzack commented ·
What make you believe that 2m are better then 0,8m?


I have at a customer 5 MultiPlus-2 24/5000 installed. Each suck up to 250A on the DC side if under full load the battery voltage drop under 24V.


All DC cables H01N2-D 70mm2 have the same lenght (130cm) to the DC PowerRail.


All AC wires H07Z-K 4mm2 have the same lenght (~70cm) to the AC collector and from there I go to the FuseBox with a H07VV-U 3x10mm2 of 18m.


There is nothing unbalanced.


Did you connect the two inverters with the 6mm2 directly and then from onevof the inverters to the FuseBox?


I had this issue already several times with peoples installing the victron system them self and then struggling for weeks or month (on even more then on year) because of simple installation errors.

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nickdb avatar image nickdb ♦♦ Michelle Konzack commented ·
For parallel systems to work right you mustn't have too low a resistance cabling. Short, thick gauge runs aren't ideal for maintaining symmetry. This is documented in the guide for parallel systems.
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sgrigor1 avatar image sgrigor1 Michelle Konzack commented ·

No, I connected them through 3x pole 32A fuse per circuit (AC-IN, AC-OUT1, AC-OUT2). After it, I have separate automated fuses in the white box from the right of the picture. It's OK?

The cables are CYY 5x6 (AC-IN, AC-OUT1) and CYY 3x4 (AC-OUT2)

Still these short AC segments cables are influenceing the functionality becasue some time one inverter goes in overload and the system is unstable.

2m of 4mm2 wire has incresed resistence compared to 0.8m of 6mm2. Right?


1693562767768.png

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sgrigor1 answered ·

Finally, I identified the root cases for the issues .

1. System stability - after I changed the wires segments for parallel connections , the system becomes more stable and balanced . I replaced the 0.8m length CYY 6mm2 cables to 1.6m H07RN-F 4mm2. It’s a must to have more resistive on AC path. I loaded the system to 9.5KW and it worked perfectly. Probably, due to unbalance it loss mains and facing 2nd issue. It was my mistake to don’t follow the guidelines.


2. AC-in connection triggers the multiplus 2 to generate a lot of noises , feed-in and consumes a lot of power, overload warning, then after a while everything enter in normal. After some research, I discovered that this behavior is due to LOM detection. I disabled it and no issue after. That means that my utility line has more than accepted impedances and LOM algorithm is not able to detect the line.

I need to double check my grid line in my home because I have several fuses that could affect the impedance. Then I need to ask an electrician to double check the joins outside of home. If it’s not from there, another solution is to keep the LOM disable and install an anti-islanding safety device. The recommended Zeith device is very expensive , do you know a chipper one for single L1 phase?

What I don’t understand, why LOM detection is working ok on single Invertor configuration and not in parallel inventors configuration?

Thanks for your support, certainly the recommendations from here help me to detect and fix the issues.

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