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martin24 avatar image
martin24 asked

Enhancement request: 2 different settings for "grid setpoint"

I have a Multigrid with Venus gx and a BYD B-Box 5.0 and a ET340 meter.

I am a bit disappointed about the regulation quality of this setup. If I leave the "grid setpoint" at 50W I can see a lot of spikes below 0 while the Battery is discharged, meaning there is energy fed into the grid.

Tickling around 0 means I am buying energy at 28ct/kwh and seconds later I am selling the same energy for 12ct/kWh out of the battery. This is bad.

If I increase the grid setpoint to e.g. 100W this becomes better but it also means I am buying more energy than necessary. I get energy out of the grid which could also be supplied by the battery.

It becomes really bad when there is PV power available and the battery is charged. Leaving grid setpoint at 100W I get around 100W out of the grid even though there is enough PV power available to run all loads and to charge the battery. In fact the battery is partially charged out of the grid.

Setting grid setpoint to e.g. -100W would solve this. While PV power is available then there is some of it fed into the grid (around 100W) and the rest is used to charge the battery.


I really would like to prevent the situation that the battery is discharged and some of its energy goes to the grid and also the other way round that the battery is charged and nevertheless some energy is taken from the grid at the same time.


Would it be possible to get two setting of grid setpoint depending on charging/discharging the battery?

So when battery is charges set gridpoint to e.g. -100W to prevent any power taken from the grid.

When battery is discharged set it to +100W to prevent any power fed into the grid.

Thanks

Martin


ESS
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dustdevyl avatar image dustdevyl commented ·

I would also love to have to some options for the grid setpoint. It could be linked to the battery charge as mentioned above or maybe setup with time of the day; eg from midmorning to end of afternoon; one setting. Then for when no solar production another setting.

For me i would use this to minimise the power drawn from the grid when my panels produce more than enough power and then when they dont i would optimise the battery discharge time so it will slowly discharge throughout the night. Well, as long as the wife doesnt use the hairdryer.....


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Rob Duthie avatar image Rob Duthie dustdevyl commented ·

Hi

The Mulitplus2 does this already under the ESS settings.

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Rob Duthie answered ·

Hi Martin24

I have a similar with Mulitgrid 2 in a single phase unit using a ET112 meter for the PV inverter, the Internal CTs are poor and way off calibration, they will always float around 20 to 55 watts when there is no load on the outputs, when i fitted a external to over ride the internal one it still reads about 10 to 15 watts, in there software they have not allowed for this.

As the internal power consumption is added to the readings, But on the AC 1 critical loads it does have another internal CT to measure the output, not sure if that is current protection of the inverter or can be used for inverter output power readings.

They have told me that is how it is.

They need to explain this better in there manuals, and brochures so people are aware what is going on with there units, so they would not asked all these questions?

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boekel avatar image
boekel answered ·

in ESS mode this is always so, if a load is turned on it first comes from the grid and the inverter will adjust to get back to the grid setpoint, the same goes for when a load is switched off, first energy will flow back into the grid, until the inverter output is reduced to reach setpoint.

A possible solutions:
when your inverter / battery combination is powerful enough to run all loads: use the 'generator assistant' to ignore AC-in when: battery is above x SOC, and you might choose to connect to grid when more than x power is being used.

something like this:


screenshot-2018-11-23-234433.png (16.5 KiB)
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Rob Duthie avatar image
Rob Duthie answered ·

May there should be a extra control added to the ESS assistant to allow for these situations.

And may be CT calibration assistant would be nice as to get the true current readings with zero loads?

Note: And the other thing is were they inject ripple relay control signals for water heating etc here in New Zealand, my Mulitplus 2 can pull up to form 250w to 1kw from the battery bank when they are pulsing, is this normal? Has the inverter got any filtering of the harmonic currents?

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arjanbijker86 avatar image
arjanbijker86 answered ·

hi,

I have the same request for different grid setpoints, but the application is different.

Grid setpoint to be changed based on the time of day or week / weekend profile.


During the week I need to set my grid setpoint to 20 000W. I have 3x 15kVA Quattro then effectively loadshaving, saving kVA demand charge.


During the weekend I want to set my grid setpoint to 0W. The load in the factory is then minimal and want to optimize solar production.


Can this be added as a enhancement request?


Regards,


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Meine_Energiewende avatar image Meine_Energiewende commented ·

My solution for this is: feeding everything into node-red and set the grid-setpoint via mqtt to the venus.

Works like a charm.

Jens

grid-setpoint-nodered.png(102.7 KiB)

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grid-setpoint-nodered.png (102.7 KiB)
arjanbijker86 avatar image arjanbijker86 Meine_Energiewende commented ·

Hi Thanks,

yes currently we are doing the same but via ModbusTCP and also works like a charm.


Do you use a device locally (on the same network) to control the Venus? What device are you using?


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