Decimal MaximumFeedGrid

[FelixVNA]

Hi,

i tried to control the feed to grid value today and it is working overall. But it does not accept decimal numbers like 7.5. I tried "," and "." but no success. Interestingly the original value was a decimal number, which i can't get back to now.
Is this a limitation on the adapter or the inverter or modbus?

EDIT1:
Also i noticed if i set the limit to e.g. 7.5 kW and then check the feed to grid, the actual value was a little lower ~ 150W. Sun was shining bright, so not an energy input from sun issue.

Best regards
Felix

[bolliy]

Which specific control value (state) do you mean?
It is used with the inverter in the same way as with the EMMA. I need to process the value in watts rather than kilowatts—so, for example, entering 7500 W instead of 7.5 kW. The 150 W discrepancy is likely due to how the Huawei inverter processes the data. What do you think?

[FelixVNA]

This one here: sun2000.0.inverter.0.control.grid.maximumFeedGridPower
I will observe the difference (~150) during the day and see if it changes with load in the house or different sun positions. Not an issue, but i just noticed it.

[bolliy]

done!
Please install beta v2.7.1

Description in German: https://forum.iobroker.net/post/1357408

Stephan

[FelixVNA]

Thank you for fixing this so fast. I am impressed by your support.
I installed the beta and it works like described. I can enter 3 decimals and the value is being written to the register.

The delta of ~150W still applies, no idea why, but i will just offset by 150 W.

Otherwise there was a popup window when installing the beta and it said something like this "Please beware, units for grid.feedPower changed to W instead of kW" But this is actually not true, since i still used kW with decimals as input.

[bolliy]

Please ignore the pop-up; the information is incorrect. It will be removed again ;)

Stephan

[bolliy]

I ask the AI ;)
Thanks for the report. This is most likely not an adapter issue. The adapter only writes the limit to the inverter (register 47416) and does no regulation itself. The control loop runs inside the inverter, based on the reading from its grid meter. A small gap below the limit is normal for this kind of closed-loop control:

1. Safety margin: The inverter regulates slightly below the setpoint so the limit is never exceeded. Exceeding a grid operator's limit is worse than losing a few watts, so a constant offset of ~100-200 W is plausible.
2. Control lag: The meter is polled about once per second and the inverter reacts conservatively. When house load fluctuates, the inverter approaches the limit from below to avoid overshooting, so the average ends up slightly under the limit.
3. Measurement differences: The inverter regulates on its own meter value (DTSU/DDSU or the EMMA sensor). If you compare against a different meter, such as your utility's meter, tolerances (±0.5-1 % of 7.5 kW is already 40-75 W) and CT errors add up.
4. Battery systems: With a LUNA, the inverter also has to balance PV, battery and house load dynamically, which adds some regulation error.

I haven't found an official Huawei specification describing a deadband for this, so this is a plausible explanation rather than a confirmed one.

How to narrow it down:

• Average meter.activePower over several minutes instead of looking at instantaneous values. A constant gap suggests an offset, while oscillation around the value suggests control behavior.
• Test other limits (e.g. 3 kW and 5 kW). A constant gap points to a regulator offset, a proportional gap to measurement accuracy.
• Compare the inverter's meter reading with an external meter.

If you want to use the full limit, you can set the value slightly higher, as long as you stay within your grid operator's requirements.

[bolliy]

I researched this and described it in the wiki. The Active Power Derating does not take household consumption into account!
https://github.com/bolliy/ioBroker.sun2000/wiki/Wirkleistungsbegrenzung-(Active-Power-Derating)