Strange interaction between cable losses 'In Detail' and SolarEdge MPP Voltage.

[Gejege]

I am running a simulation for a SolarEdge simulation using detailed cable losses and I am seeing some strange results when plotting the MPP voltage graph.

Example graph below, I have two near identical inverters with near identical strings, the only difference is one has 10m of string cable per string, the other has 200m of string cable per string. Why would the system be spiking at over 1400V when the losses are higher? This only occurs as the string losses increase, as when I set the DC cable to something large like 25mm2 the voltage spikes are eliminated.

Any ideas what is happening? Thank you,

[developer_fw]

Hello Gejege

On 2/23/2024 at 3:14 PM, Gejege said:

Any ideas what is happening? Thank you

Not yet.

Might you be so kind and send me the .pvprj file via private message here in the forum so we can have a look into it?

Thank you in advance and kind regards
Frederik

[Gejege]

3 hours ago, developer_fw said:

Hello Gejege

Not yet.

Might you be so kind and send me the .pvprj file via private message here in the forum so we can have a look into it?

Thank you in advance and kind regards
Frederik

Of course, I'll send it over now.

[developer_fw]

Hello Gejege

Thank you for your project.

I wanted to inform you that this peak is due to little artifacts within our characteristic calculation, which results in shifted MPPs:

To give a reference about the scale:

We're still investigating and are getting back to you.

Kind regards
Frederik

 

[developer_fw]

Hello Gejege

The reason for this jump are the SolarEdge power optimizers.

They have a feature that switches a bypass at the original MPP of the connected module, more precisely at the MPP voltage point, in which the actual power optimizer electronics are not active. The bypass comes with a (higher) constant efficiency of 99.5%. This always leads to these small bumps in the characteristic curve. Depending on the additional amount of cable losses, this results sometimes in the MPP or sometimes in the point where cable losses are minimal.

Kind regards
Frederik