Hello,
When you model a PV system in SAM, you choose from a few different options for how SAM will model the system. The equations that SAM uses depend on the options you choose.
For a description of the different PV models in SAM, see the references on the
Performance Models
page.
We are working on a reference manual for SAM that describes the details of the PV model. It should be ready for publication this winter (2013/2014).
Best regards,
Paul.