dependency to the grid in case of enough battery back up and PV energy production

[Morteza]

Hello dears
I couldn't find the answer of my question in other topics so I make a new one. In attached picture I have mentioned three points that represent I have enough battery charge or the energy production of PV is sufficient to cover my consumption, but still system takes the power from grid. it makes sense during Jan or Dec that I feed from grid, but I want to know can I make it zero in June or other months with same potential?

 

[developer_mh]

Hi morteza khaledabadi,

could you provide the project file, please? You can send it to me as a private message here in the forum. As the consumption values are very small, it might be that the inverter is not able to deliver the energy from the batteries to the consumers due to the starting voltages or power values.

Kind regards,

Martin

[Morteza]

Thank for your prompt answering
I couldn't upload the file directly, so I have uploaded it in an alternative server and here is the link:
https://filebin.net/tif3y5il4uvhjs5j

[Morteza]

Hello dears,
Is there any solution or suggestion? 

[developer_mh]

Hi Morteza,

sorry for the late answer. And I am afraid that I didn't have a chance to download the project file so far. Could you please upload it again. I am very sorry for the inconvenience caused.

Kind regards,

Martin

[Morteza]

Here you are

P20230001-Roberto Extended.pvprj

[developer_mh]

Hi Morteza,

thanks for the project and your patience It is like I suspected. The load profile has very low values in comparison to the nominal power of the PV inverter, in the range of under 5% utlisation. The points you marked with a blue X refer to load values of 100 to 300 W, with the nominal power of the Huawei SUN2000-8KTL-M1(380Vac) of 8 kW, it gives us utilisation ratios of 0.1/8 = 1.25% to 0.3/8 = 3.75%. This means, the PV inverter (to which the battery system is connected on the DC intermediate circuit) operates in a very suboptimal range in terms of efficiency:

What happens is that the load profile needs e.g. 100W from the battery system at night, and 100W are discharged from the batteries. But the PV inverter effiency is so low that a great part is lost on the way from the battery through the PV inverter to the loads on the AC side. All that is lost needs to be compensated for by the grid.

This is why there is often energy from grid in the simulation (and also in reality, depending on the specific setup and the location of the load sensors). Since we have a lot of questions in this regard, in the next major version we will modify the logic so that we take into account the effiency of the PV inverter beforehand, i.e. if the load needs 100 W, we will discharge a lot more from the battery, say 400 W, so that 100 W are still reaching the load in the end.

Hope that helps, kind regards,

Martin