DC - DC converter simulation ( Multisim or Ltspice )

We are building test 400W dc / dc converter and we created schematics for it. The schematics is tested in real world but circuit protection is activated most of the time. Our goal is to see why is this protection activated so i want to simulate whole circuit to see what is error. The simulation must be tested with or without load and this topology will be used for much greater powers. I will explain in detail what should be done but basically, schematics should be tested in multisim or ltspice.