I believe you can model a PV panel as a voltage source with a resistor in series. Anyway it's a start.
Example, if it is rated for 12V at 3A, then it can be modeled by a 24V source and an inline 4 ohm resistor. If you attach a 4 ohm load then it gets 12V at 3A, and that is also your condition of maximum power transfer (impedance matching).
I once did tests on some PV panels, with various loads. I took measurements of voltage and current.
For a panel designed to charge a 12V battery, I found it puts out 22V when a very light load is attached.
With a 0.3 ohm load, current output is 3.2 A but voltage drops to 1V or so.
By graphing all data, I saw that maximum power transfer is with a 6 to 8 ohm load.
When you attach a battery, things change. The internal resistance of the PV panel can be changed to a lesser value. Evidently this model needs more effort put into it, though I'm not sure just how to do it.