Jacob,
We do not currently have a model for the UCC2818. We do not have many models for PFC devices. We usually have PSpice or TINA-TI models available, and both would be encrypted and could only run in the appropriate simulator.
I do not have any hints for the internals of the device. Perhaps a post to the AC/DC and Isolated DC/DC Power forum could provide you some insight:
http://e2e.ti.com/support/power_management/isolated_controllers/f/188.aspx
Britt