Isolated buck H bridge control system design
You can model it in a simulator and, you don't need to model it as a switching converter because a linear model will work. If your switching frequency is (say) 100 kHz you could make an argument that modelling a delay of 10 us is useful to add.

Modelling it as a linear regulator has the main advantage that you can run an AC analysis and produce a bode plot.

May I recommend Micro-cap 11 student edition or if you want to go down to the bargain basement try LTSpice.

In Micro-cap you can model in the s-plane directly using formulae. I'm not sure if it will model in the z-plane because I've never tried but if you do go this route please make an answer to your own question. It will be useful to others I'm sure.