Multiplus 2 Limit Power Output ESS Mode 2 (Solved)

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gjones84 asked Aug 9, '21

Multiplus 2 Limit Power Output ESS Mode 2 (Solved)

Hi All,

I am currently running a Multiplus 2 3KW connected to a 15S65P 18650 base battery. My BMS is Batrium WM4 that talks over CANBUS to a Rpi4 running Venus OS. Im using a CT clamp to mains to try and keep the grid value at 0W. Set in link below.

https://community.victronenergy.com/questions/32828/can-current-transformer-replace-energy-meter.html

Everything has been running sweet as a nut for the last 18 months but there is one issue that I cannot appear to get to the bottom of and that is the power limit of the system. The intention was to never run it more than 1000W.

The issue I have is when a big load is switch on in the house such as a kettle, cooker heating element or iron. The inverter rams up to max invert of 3kw and then slowly ramps back down to 1000W. So it appears the power limit works but the inrush current of 50 to 60 Amps is something I want eliminate.

In the manual section 4.3.9. The manual states this:

The losses in the inverter/charger are not taken into account. If you want to limit the amount of power being drawn from the battery, you will have to set this limit slightly lower to compensate for those losses.
Power coming from the MPPTs is not taken into account. Using this feature in a system with MPPTs can cause the output power from the MPPT to be reduced.
This limit is with respect to power drawn from the battery and will affect the total of all phases.
This limit only applies while connected to AC-in: In inverter mode, the AC loads determine how much power is drawn from the battery.

BULLET POINT 1- Ihave tried setting the power limit to 700W but i sytill get a 50-60A inrush.

BULLET POINT 2- Im not using MPPT's.

BULLET POINT 3- N/A

BULLET POINT 4- I am only connected to AC IN using as a bidirectional inverter/charger. I have no loads connected to the AC out. When is sates 'inverter mode' does this mean this setting? inverter only? Or is there another setting?

I currently leave the switch in the ON position and do not run it 'inverter only'. This is because I want it to invert/charge when required.

Does anyone have any idea how I can limit it so it ramps up to 1000W when large loads are switched on? Or will I have to run mode 3 to eliminate this issues?

Any help would be much appreciated.

Thanks

Gareth

current limit

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Modifications Space

Node Red Space

Answer 1 · 2021-08-09T16:19:59Z

shaneyake answered · Aug 09, 2021 at 04:19 PM

You can not limit those ramp up currents when using the CT. If you switched to a grid meter this wouldn't be a problem.

I am going to use GX and Rpi4 interchangeable.

The problem you are seeing is due to control loop delay.
The GX is setting the AC-IN setpoint to 50W, this setpoint is then controlled by the inverter.
VE.BUS does not have anyway to limit inverter output.
When you plug in a CT, it replaces the inverters AC-IN CT.
The inverter sees the load turn on, inverter ramps up to keep grid at 50W, the gx then sees the inverter has gone over the 1000W and raises the setpoint to let's say 500W, another 5 secs go by it then raises the setpoint to 1000W and keeps going that till the inverter power is only 1000W.
You should also see a spike charging the battery when you turn off a big load.

Does that make sense?

If you use a grid meter the GX will change the setpoint based on the meters data, this normally means that it lags behind, Like load will come from grid for a few seconds will inverter is told to ramp up.

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Answer 2 · 2021-08-10T16:02:08Z

gjones84 answered · Aug 10, 2021 at 04:02 PM

Hi,

Thanks for your reply.

Yes that makes sense. I had gut feeling that would be the case.

I have considered a grid meter but to be honest now you have confirmed that I cannot tune out the inrush with my set up I might have a play running my multiplus in mode 3 external control, using node red as my software to control the import/export via modbus.

I think this way I will be able to control the ramp up/down speed and limit the inrush when large loads are switched on.

I wonder if anyone has a node red flow for external control using the multiplus in mode 3? I have done some searching but couldn't anything.

Cheers

Gareth

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shaneyake commented · Aug 10, 2021 at 11:13 PM

Yeah, you will need a meter of some sort. Mode 3 will have the same problem without a meter as you need to disconnect the CT to have it work the way you would like.

I use NodeRed to control my setup which is really complicated and has multiple inverters and GX's in the mix.

Victron has Nodes already
https://flows.nodered.org/node/@victronenergy/node-red-contrib-victron

My setup is running NodeRed on my main GX via the Large Project.
https://www.victronenergy.com/live/venus-os:large

I am currently running Mode 3 but with a CT as I wanted really fast response on my main inverter. My goal is to keep grid at 0W always unless SOC is too low.

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Answer 3 · 2021-08-19T10:02:24Z

gjones84 answered · Aug 19, 2021 at 10:02 AM

Hi,

Just a little update. To get around the inrush issue I have now set my GX to external control on my ESS in mode 3. Im running my own control looping node red. Need to tweek some time constants to reduce spill back but otherwise running really well.

This was before you can see when the oven was switched on the orange line (inverter output) ramps up to 3KW and then slowly ramps down to the inverter limiting valve of 700W.

Now. When the load is switched the first few seconds the load is pulled from grid and inverter ramps up to 500W. Then ramps back down again. There a little bit of spill back to grid which I will tune out eventually.

Here's my flow if anyone is interested in running mode 3 on a GX in ESS in mode 3 with no inrush.

Cheers

Gareth

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