Operating DC voltage

Hi,

I am simulating a real system in SAM using measured data and then comparing the output with the measured variables of the real system. The only thing not matching the measured variables are the DC operating voltage and DC gross power (both are somehow related so it makes sense that they differ from the real data in the same proportion). On the other hand, the current (not provided by SAM directly, but I have calculated it as I=DC gross power/operating DC voltage) does match the measured current. I am only comparing the results of June 6th at 23:00 to June 7th at 22:00 (winter time). The graphs in the Excel file are with respect to the summertime, but the weather file and output of SAM are referred to wintertime.

I would like to understand what should I do in SAM to get DC operating voltage and power values closer to the real ones. Here you can find an Excel with the compared data, SAM file, weather file, and data sheets of the installed PV modules (295 Wp TSM-DD05.05 (II)) and inverter (Symo hybrid 3.0-3-S). There are 10 modules/string and only 1 string.

This is really important for me, hope you can help me. Please, let me know if you need any additional information to better understand my problem.

Thanks in advance,

Hi Alejandra,

SAM is designed to give reasonable predictions of total annual and monthly output in kWh.

The discussion in the PV Case Studies and Validation papers may provide some insight into how to calibrate SAM inputs for comparison with measured data: sam.nrel.gov/photovoltaic/pv-validation.html

The module voltage model is sensitive to ambient temperature, so for your comparison, the solar irradiance, ambient temperature, and wind speed data in the weather file should be data measured at the system's location.

Best regards,
Paul.