PVsyst red error message not aligning with calculations.

[Vera]

Our client has specified the following design conditions with 30 modules in series. PVsyst will not allow me to execute the simulations do to it determining that the array Voc at -10 degrees is greater than the inverter absolute maximum input voltage. However my calculations show that this system should be feasible and the clients engineering team determined it to be feasible as well.

Here are my calculations:

Standard Voc= 45.9V
Voc at -10°c≈ 46.29 V
String Voltage=30 (mod. in series) ×46.29 V = 1,388.7V
Max PV input voltage of the inverter=1500 V

Since the string voltage (1,388.7 V) is lower than the inverter's maximum input voltage (1500 V), the system should not encounter overvoltage issues at -10°C with the specified number of modules in series.

Why is Pvsyst giving me this error message and what does it use to make this determination? I assumed it maybe due to weather data but the values did not change when I used weather data from a much hotter climate to verify if that was the factor causing this issue.

Thank you!

[Linda Thoren]

The dimensioning messages are based on the data and limitations in the panel and inverter file and the main electrical characteristics are calculated under chosen operation conditions using the one-diode-model. Verify that the temperature coefficient under the Model parameters in the panel file is correct, see the following help page regarding the temperature coefficients:
https://www.pvsyst.com/help/pvmodule_tempcoefficients.htm
https://www.pvsyst.com/help/pvmodule_corrtemper.htm

The limit of Voc at -10 degrees is set in the project settings, where the threshold of -10 degrees can be changed to reflect the coldest temperature observed at the site. 
You can read more about the Array voltage sizing in the following help page:
https://www.pvsyst.com/help/systemgrid_vocond.htm 

Kind regards