Pspice giving wrong results
It's never a bad idea to avoid blaming a tool that's widely used in the world by engineers all over and, instead, to doubt your actions. In this case you used an opamp instead of a comparator, while in PSIM you used a buffer to condition the signal. That can result in widely changing output. Be sure to use a comparator, and also that it uses the correct output levels to drive your switch. In other words, make sure the two schematics are the same, if you want similar results.
And if the sawtooth is not working, try using a PULSE source with V1=0, V2=3, Ton=4.99u, and T=5u. Not lastly, are you sure you want those values for the loop filter: 10 Ω, 24 Ω, 6 μF, 20 μF?