Thanks everyone.
I do know how MPPT works. I'm actually planning to impliment P&O so it's not quite the differential. That would be incremental conductance though. As asdf44 mentioned, a PV panel can be modeled using a diode and an antiparallel voltage controlled current source. The voltage being your irradiance. Of course, you can also add a parallel and series resistor to model your shunt and series resistance. I have the PV model down, I was hoping someone knew a way to implement an MPPT algorithm to vary the duty cycle and find the MPP. This is mainly about the circuit modeling, not the controls, but I will keep PSIM in mind for future needs. I've never used that so that's good info. I guess I'm going to have to figure out a clever way to use the algebraic functions as asdf44 mentioned.
I don't understand how I will be able to use a NMOS for the high side switch if Vds is so large (hundreds of volts). Vgs > Vds +Vth to turn on, correct?