Did you try TIs simulator TINA?

They have also no AC Analysis Model.

Patrick Lenzen wrote:
> Hello,
> I would like to simulate the LLC converter with TL431 controller and
> UCC25600.  How do I get the plant of the LLC converter incl. UCC25600? I
> would like to design the TL431 with the bode plot.
>
> Thanks.
> Patrick

You can measure the plant gain in a test setup with various output 
loads.
Total plant gain is d(Iout) / d(VCOin).

On the other hand it I assume you can derive the plant gain from the 
transition modell as well.