PAN file: Different Rs(sometimes Rshunt also) in Model parameters and Additional data

[leeel]

Hi all,

Is there anyone who knows how to solve the problem below?

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I used "Optimize Rs" in Additional data and got Rs = 0.186 ohm/ Rshunt 700 ohm. At this step, both Rs and Rshunt in Model parameters and Additional data are the same.

(Model parameters_1.PNG and Additional data_1.PNG)

Then, I saved the file.

However, when I opened the file again, Rs became 0.192 ohm in Additional data while Rs still remained 0.186 ohm in Model parameters.

(Model parameters_2.PNG and Additional data_2.PNG)

Anyone knows why this happened?

[André Mermoud]

Remember that the  "Additional data => Measured data" page is a tool for analyzing the low-light data, usually recorded according to the IEC61853 norm.

This tool allows to import measured data, but it is completely independent of the "edited" PV module.  After importing, you can play with the parameters for adjusting at best the model  to the measured data.  When exiting this tool you can ask for adjusting the parameters of the "father" PV module, in order to get the same low-light behaviour at 25°C that you have chosen. This will not necessarily result in the same Rserie,  as the STC values of the "father" model are not necessarily identical to the values measured at 1000 W/m2 and 25°C.  In your case the Rserie is indeed identical  (0.186 ohm).

However the parameters chosen for the "measured" module are not saved on the file. When you reread the module, the Rserie/Rshunt values are set to an initial value defined by PVsyst (i.e. default rel. efficiency@200W/m2 = -3%).  You can observe that on the second image, the mention "RSerie optimized" appears, when it is not present on the last image.