question

diederik avatar image
diederik asked

Turn grid on/off

Hi,

I have a Multiplus-II GX and working on a Node Red flow to control my setup.


The PV inverter is a Sunny Boy 3.0. When the grid fails I switch the Multiplus to Inverter only. That way the Sunny Boy can keep charging my battery.


The problem is when there is a lot of sun and the grid reaches 253V, the Sunny Boy will stop working. My idea was to turn the Multiplus to Inverter Only too. So far so good. But, when the grid drops again to, let's say 230V, I'm not able to measure that voltage. And I'm not able to turn the Multiplus back on.


Any ideas how to deal with this?

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Multiplus-IIgridvoltage
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matt1309 avatar image matt1309 commented ·
Hi @Diederik


Is there a reason you're not using ESS and having the sunboy wired on ACOut side of inverter? Assuming sunnyboy supports frequency shifting it'll work without needing manual control.


Is your setup safe. What happens to sunnyboy power output when grid goes down and you've turned on inverter only mode and the batteries are full?

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diederik avatar image diederik matt1309 commented ·

At first I had only the Sunny Boy and wanted to be 100% sure that I always can charge the battery, even without grid.


About your second question, to be honest, I have no idea. Won't it just be balanced?

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matt1309 avatar image matt1309 diederik commented ·

You must already have it wired on ACOUT side but I would just use ESS. It'll get what you're looking for without any need for manual work. Assuming you have frequency shifting and factor 1:1 followed (im guessing you do based on 3 in sunnyboy 3)


Give this a read. It'll cover everything you need/why folk are flagging concerns with your setup at the moment:

1. ESS Introduction & Features (victronenergy.com)


Particularly system design tab


Balance with what? Say battery is at 100%, loads are 100w, PV is 1000W and there's no grid. Where does the 900w of sunnyboy power go? You need frequency shifting enabled for this to be safe. So victron system can tell sunnyboy system to reduce it's output. Otherwise that 900w has no where to go and bad stuff can happen...

Also good points below to make sure the sunnyboy meets the factor of one rule if you move to ACOUT. (I suspect it is given the 3 in the name, guessing that's 3kw?)


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diederik avatar image diederik matt1309 commented ·

Thanks for your input. I'll look into this.

I did not made this setup, so I guess everything is safe.

I want to achieve 2 goals.

  1. Use the grid as little as possible.
  2. Avoid high grid load (capacity rate?). The average consumption during 15 minutes determines what we pay for the entire month.

I'm using Node Red for the capacity rate which works perfectly.

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matt1309 avatar image matt1309 diederik commented ·
A standard ESS setup should manage this. It will prioritise solar/battery over grid usage so if you have enough battery/PV you'll use no grid.


I dont quite get the capacity element? Is it an average of 15mins and then they change you the highest 15min average?



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diederik avatar image diederik matt1309 commented ·

Everyone pays a capacity rate per month for a minimum of 2500W. If during 15 minutes you use more you have to pay extra for that month. It doesn't matter if you used extra power for 15 minutes of 20 days, you have to pay the same among.


I use ESS, DVCC and Node Red to keep the grid load below 2500W.

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matt1309 avatar image matt1309 diederik commented ·
I wouldve guessed just setting it VEConfig to set max grid usage to under 10amps wouldve done the trick (10amps incase the voltage drops low in your area if not increase slightly)
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diederik avatar image diederik matt1309 commented ·

I'm calculating de max. current in DVCC.


setpoint = (maxGrid-acLoad+pvLoad+dcLoad)/batteryVoltage;

Maybe I'm making things unnecessarily complicated but it works great.

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matt1309 avatar image matt1309 diederik commented ·

Are you recreating ESS yourself? If not then this feels like it's not needed and just setting grid connection to 10amps is the same. Unless you want to allow max exporting but not importing. Then might need something custom.

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diederik avatar image diederik matt1309 commented ·

If I set the grid connection to 10A, and I need 5A AC-Loads, the total grid load would be 15A?

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3 Answers
Duivert NL avatar image
Duivert NL answered ·

hi, why dont you use ESS, then everything works automatic, also if grid voltage is above settings in multiplus grid, then it disconnects and runs in inverter mode automatically

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diederik avatar image diederik commented ·
This is all pretty new to me.


I'm using ESS. Where can I check the settings that it will disconnects automatically?
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Duivert NL avatar image Duivert NL diederik commented ·
you can set that up in VE config - grid


also: is your sunnyboy PV considering the factor 1 rule?

and have you setup the frequency shift for the sunnyboy, thats what matt1309 meant

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sharpener avatar image
sharpener answered ·

Eastron multifunction meter on grid connection would have many uses inc measuring the voltage, interfaced via ModBus.

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daza avatar image
daza answered ·

@Diederik as everyone has said just use ESS on another not OP I would look at your input voltage as a separate thing if in the UK get your DNO to sort out the over voltage that’s if it is as they deem 253volts acceptable limits.

I got mine tapped as my Shelly EM logged multiple spikes going back a year or so where it got to 256volts at around 2pm and another at 8pm took them months to sort it and a lot of call and 6months worth of Shelly data and a week of there device being installed.

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diederik avatar image diederik commented ·

I tried to be as detailed as possible when asking this question but now I realize I forgot some details.


I use ESS, DVCC and Node Red to control things.
So when the grid is off or I put the MultiPlus in Inverter Only, ESS will do some frequency shifting and all will be safe.

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Duivert NL avatar image Duivert NL diederik commented ·
yes, if everything is set up right (ESS, PV and freq shift, 1 factor rule) and you let just ESS run the system, it will work fine


if you turn it to inverter only ess and the rest can work unexpected


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Related Resources

MultiPlus-II Product page 

MultiPlus-II Manual

Multiplus-II GX Online Manual

MultiPlus-II 230V Datasheet 

VE.Bus Error codes

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