question

baxter avatar image
baxter asked

ESS grid set point changed if PV Inverter in use

Dear all,

me and a other user (@energy-hobby) are observing the following ESS behaviour if an PV Inverter (at ACout) is in use.

Grid set point is at 100W (just as example, you can configure any value). During night, with no PV production, the grid consumption is quite ok around 100W. BUT as soon PV production starts, the set point is shifted upwards (to around 175W)

1654662705641.png


My setting, 3phase ESS with MP2 5000 (494), Fronius Symo 6 (ACout1) , Cerbo (2.85) and EM24.

Is this behaviour known? If yes, why does the ESS shifts the set point?



Tia

Br

Michael

ESS
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4 Answers
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Baxter

what is the VRM name or id of affected systems, and what date/time can we observe this?

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baxter avatar image baxter commented ·

I can see that behaviour every day in the morning when PV Inverter starts production. For example, yesterday:

1654849304681.png


Here is a more detailed description:


https://community.victronenergy.com/questions/138432/nulleinspeisung-mit-pv-nicht-null.html

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baxter avatar image baxter baxter commented ·

@Daniël Boekel (Victron Energy Staff)


I tested a different grid set Point (50W), same shift of about +70W as soon as PV Inverter starts


img-20220611-061956.jpg


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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ baxter commented ·

Hi @Baxter


What is the VRM name or id of affected systems?

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baxter avatar image baxter Daniël Boekel (Victron Energy Staff) ♦♦ commented ·
@Daniël Boekel (Victron Energy Staff) may i ask you for an update? tia
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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ baxter commented ·
Hi @Baxter I see what you mean, but is this a problem?
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baxter avatar image baxter Daniël Boekel (Victron Energy Staff) ♦♦ commented ·
Yes it is. The grid set point shall be the same value, regardless if a PV Inverter is in use or not. The current system behaviour either ends up in more consumption from the grid as needed or if a set a negative value to compensate the pv inverter to more feed in from the battery during night.



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ponzoa avatar image
ponzoa answered ·

I seem to be having a similar behavior in my ESS instalations also.

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energie-hobby avatar image
energie-hobby answered ·

Hello everyone.

I tested and played a bit more =)

It really seems to be a shift but i think most people probably don´t even notice the 70W, especially with large PV systems the problem almost disappears.

During the day the PV delivers more than enough power and at night it works properly.

Although Victron is open source and I have also adapted a little program to use the Fronius Smartmeter insead of the EM24, my programming "skills" stop there. I hope one of you can dig a little deeper into what the original victron software actually does.


Greetings from Bavaria

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derlang avatar image
derlang answered ·

Hello,


basically I am facing the same issue. My setup is the clean way. 3 Multiplus II connected to Grid at AC-IN (no external power meter as multis are the only on the grid), all loads on AC-Out. At the moment only one MPPT250/100 (Fronius Symo will come later on AC-OUT) and only 5 panels out of 15 on the MPPT, will change soon as well.

So I set the Grid setpoint to 30W (from original 50W). But still my setup uses constantly more than the 30/50W. Interestingly L3 seems to be the problem:

"Idle"-Mode:

idlemode.jpg

"HVAC to full power"

increaseload.jpg

Just realizing that ESS#1 info disappeared.

No Feed-In defined; L3 in goes up with more consumption on L3 out...


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increaseload.jpg (46.5 KiB)
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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·
Hi @DerLang I think you are expecting a little bit too much here, the system is dynamically reacting to loads and other factors, the grid setpoint is a goal it's trying to reach.
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derlang avatar image derlang Daniël Boekel (Victron Energy Staff) ♦♦ commented ·
Hi Daniel,

I see and understand this but never ever meeting a goal in certain tolerances (those are usually less than 50% than setpoint), it is an expensive setting and behaviour. I've calucated this for my setup (total of all phases vs. individual phases) I spend approx. 1.4kWh/day with total of all phases to 0.24kWh/day using individual phase resulting in savings of ~150€ per year. Quite a lot of money.

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baxter avatar image baxter Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Are we really arguing if my reported behaviour is a bug or not? I hope not so. Without the PV Inverter the grid set point is working quite well, of course it is reacting on loads but predictable. The only thing we need is, that the set value is always as configured and not depending on the PV Inverter. I think thats not asking too much.

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nickdb avatar image nickdb ♦♦ commented ·

The setpoint is not a destination, as Daniel has said. It will all average out around the setpoint with time, but it will constantly vary based on AC demands and transients.

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derlang avatar image derlang commented ·

@Both: This might be, but I haven't investigated during the last two days that it has been met +/- 30%. It was always more than double which is way to far away. In the meantime I think I solved this in my own thread (German Part of Forum). As I have a very clean setup - I think - I switched from Total of all phases to Individual phase. I think that the drawback of this solution will - if ever - only happen in rare circumstances but I reduced my expensive consumption to a minimum saving approx. 150€ per year.

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