question

ianp avatar image

MuMultiPlus 2 does not accept mains grid connection to AC IN - goes immediately to Disconnect state.


System comprises MultiPlus-II 48/5000/70-50, MPPT 150/100, Battery Monitor BMV-712, Venus GX. This is a new installation, and have upgraded everything to latest firmware.

The final system will be entirely off grid in a remote location, but is being initially commissioned in a residential area for convenience. As the backup generator is at the remote site, am attempting to use a plug in connection to the mains grid to simulate the generator, but this is being rejected by the Multiplus 2.

The AC connections currently around the Multiplus 2 are:

Multiplus 2 earth stud and the Battery 0V both connected to a stake in the ground (no connection with the grid installation)

AC OUT 1 Only connected to a 3 pin socket via and RCD, no connections to anything else

AC IN connected to a mains GPO via a 3 pin plug. This lead is about 8 m of 15 A rated caravan extension lead , no more than 1.5 mm2 conductors. I am aware this may be an issue with Loss of Mains (LOM) detection.


When the mains (within the allowed limits) is connected to AC IN,

1. If the inverter is running, it syncs the inverter frequency to the AC IN frequency over a few seconds then it tries to connect. AC OUT 1 output goes off for a fraction of a second as it tries to transfer and reverts back to inverter mode. AC IN goes to disconnect state, with no indications why it failed.

2. If the inverter was not running (due to low battery volts, or inverter turned off) the AC OUT1 comes on for a fraction of a second as it tries to transfer , then drops , and goes to AC in disconnect mode, and the Multiplus 2 is then in off state . Also no indication as to why it failed.


I have looked extensively at VeConfigure3, Victron Connect, Venus GX and VRM., and nothing indicates anything is wrong, other than the AC IN is disconnected.

Independent monitoring of volts and frequency at the Multiplus 2 AC IN terminal agrees quite well with the values indicated from Multi, and the AC current always stays very low – ie the charger never starts (it should as the batteries are quite low now), as confirmed by nothing indicated on the front panel LEDs. There are no dips or spikes obvious on the AC voltage. Grid AC voltage for my testing on AC IN has always been within a couple of volts of 245 VAC , well within the allowable limits set in the parameters.

Things I have tried include:

  1. Searching other community posts
  2. UPS feature on and off, no difference.
  3. Loss of Mains detection temporarily disabled (to prove the relatively small diameter cable to AC IN isn’t the issue)
  4. Monitoring the AC voltage at AC IN terminals – no dips or spikes found
  5. Confirmed the AC IN neutral is within a volt or so of earth potential
  6. Temporarily disconnected various parts of the earthing system
  7. Disconnected the VE bus from the Multiplus 2 , so it is independent of Venus GX
  8. On the Venus GX, System Setup, AC input 1 - tried all possibilities – Grid, Generator, Shore Power ( I suspect it is only text, and doesn’t change parameters in the MultiPlus 2)


I cannot find a comprehensive list of the causes of AC in disconnect. The ones I am aware of are average ACV too low or too high, Instantaneous ACV too high (265V) , frequency out of acceptable range , Loss of Mains Detection.

Are there any other causes of AC disconnect ?


What should I do next ?

Thanks in advance for community assistance.

Regards

Ian




Multiplus-II
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Did you monitor it with VE Configure 3 while doing this? No clues there?

8 Answers
ianp avatar image
ianp answered ·

Today I tried the following tests, but none of them solved the problem, outcomes were unchanged.

  • · Dynamic Current Limiter both enabled and disabled.
  • · ‘Weak AC Input’ enabled
  • · Tried the following combination ‘Weak AC Input’ enabled, ‘UPS feature’ turned off, ‘Loss of Mains detection’ disabled, Multiplus 2 isolated from VE.Bus (ie MPPT and Venus GX), and dynamic current limiter both enabled and disabled.

Other observations:

In VE.config the NS protection log on the ‘Grid code selection’ tab gets an ‘Under voltage’ entry when 48V is applied to the Multiplus 2 before 230 VAC into AC IN. This makes sense.

The current drawn by AC IN from the AC mains supply stays around 170 mA. I don’t have a way of measuring what it does the instant it tries to connect.

Today the mains supply was stable around 245 VAC, 50.1 Hz for the duration of the tests.

Undervoltage trip condition is <180VAC / 1s

Overvoltage trip conditions are >260VAC / 1s , > 265 instantaneous, 10 min mean > 255 VAC

Under frequency Trip is < 47 Hz / 1s

Over Frequency trip is > 52 Hz instantaneous


What should I do next ?


Thanks and Regards

Ian


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@IanP

You mentioned earlier this was for an "entirely off grid" application. So no ESS needed nor wanted. And your Grid Code should be "None". In that state the Multi can't feed back, and it just becomes like another appliance in a household. If you need to change that you'll need a password from your dealer.

Just a coupla little things you've said suggests this as an issue, but maybe I've misconstrued something. I'm running out of ideas if it isn't so.

Thanks very much JohnC, Grid Code set to "None" solved my problem. I had been looking at all the detail and missing the big picture.

All working as it should now. Thanks again

Regards

Ian

ianp avatar image
ianp answered ·

@JohnC @Seb71 @renz Thanks everyone again for your excellent help. This is my first use of this great community, and I am still finding out how to use it. I now realise the way I was accessing it directly via my browser didn't always show me the latest updates, and I missed a couple along the way that had the right clues to help me solve the problem. Thanks for your persistance with me. Regards Ian

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raymiller avatar image
raymiller answered ·

I've had a similar problem with my test setup/commissioning, a MulitPlus 2 24/3000, anyway long story short my problem was related to grid codes (which required the Neutrals on the electrical board to be all connected), as this was a test setup I needed to add the Neutral wire ACIN to ACout hard-wired for my testing.

Ray from Australia

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Lyndsay Cotton avatar image
Lyndsay Cotton answered ·

Evening everyone. I have just posted a similar question and this particular thread confirms my understanding however, in my scenario I do not want to disable the Grid code. I want to just move the cut off higher. I THINK this will solve my problem

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renz avatar image
renz answered ·

Thanks for your advice JohnC, it seems like Ian is now sorted.

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renz avatar image
renz answered ·

@JohnC Is there a way to get the attention of a Victron person?

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Hi @Renz

You can't post here without being seen by a Victron staffer. And there's even a couple of they who don't use a Victron tag (not me). If you need a particular one, use the "@" function, but please consider seriously before doing this.

Now of course you've just tried this with me (I don't mind), but there's an intermittent fault with this platform (which isn't a Victron product) and very occasionally it won't work. Usually accompanied with loss of the 'line return' function, but an edit will usually fix it. I have to do the same with this post.

Also, sometimes questions can slip through the cracks, and if that happens edit it or add a plea as a comment. But please don't abuse this advice.

It sounds a bit complex to me as a software hater, but thanks for your attempt to clarify.

ianp avatar image
ianp answered ·

Hi JohnC, thanks for your helpful reference. I have read it carefully and it reinforced my understanding of how things interact. It also explained that the moving blue bar on VEconfig is the waiting timer, before attempting another re connection. I have spent a long time watching this blue bar repetitively go through it's in my case cylic routine.

Two things in it I haven't tried-

  1. enabling Dynamic Current limiter, because I don't have any load connected to the AC OUT1 while doing the testing. I did do some load testing with a 1700 W heater, and that worked fine from the inverter and the 48 V battery, but didn't do that for too long because currently have no easy way of recharging my 48 V battery. My current issue is can't get AC IN to allow battery charging, and solar panels are all at target off-grid site (not at my initial test location). Now the 48V battery is is discharged to the point where the inverter won't start.
  2. Weak AC input - this is to allow for waveform distortion from a generator, but I was thinking the AC mains I am using to simulate the generator should be clean. One possible source of distortion is a 3kW grid interative PV system at the test location, but if that was the issue, everything should have worked fine the times I was testing in the evening when it was off. I have tried testing all hours of the day and evening.

I will try these 2 tomorrow.

Another thought that occurs to me - I have been trying things one at a time, then reverting back to what I think should be the correct way before trying the next thing. Maybe I should try them all at once.

Thanks again JohnC for your help and increasing my understanding.


Regards

Ian

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So no clues in VE Configure 3's VE.Bus Monitor panel?


Which grid code do you use?

@IanP

I wish I could help more with this. I've seen most of the issues with my own generator(s), but I've never tried on mains. And who knows what else they may be transmitting down power lines.

I'm not so sure the all-in approach would be wise. My old 6kVA needs WeakAC selected, but then baulks at DCL. A 2.2kW donated to me recently (good neighbour) is the opposite - it goes without WeakAC, but must have DCL.

A heavy throttle on the input Amps at the start of your tests I'd advise, then work up.

Leave the Multi's battV shutdown setting as low as it can go, the warnings suffice, at least at testing time. If your batts are really low, you may need to charge them up individually if necessary.

Good luck. Let us know how you go..

JohnC avatar image
JohnC answered ·

Hi @IanP

Have a look through this. It isn't specifically for mains power, but the issue is similar: https://www.victronenergy.com/live/multiplus_faq


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