Hi Xingguang Yu,
This guidance from the National Electric Code is a vague on how to use the Sandia Photovoltaic Array Performance Model for this purpose. There are several online articles on this subject that might be helpful, and this informative webinar recording from Terrabase Energy:
www.terabase.energy/post/webinar-recording-increasing-string-length-using-advanced-voltage-modeling-techniques
We are working to update SAM's System Sizing macro (click
Macros under the Simulate button to see a list of macros) to follow these guidelines. The current version is based on older string sizing approaches.
Note that SAM does not report the array operating current, but it does report the array DC power (Subarray x DC power gross) and both the operating voltage (Subarray x Operating DC voltage) and open circuit voltage (Subarray x Open circuit DC voltage), so you can calculate the current from those values.
Best regards,
Paul.
Best regards,
Paul.