1. Sinewave

2. Simulation result
263.4V

3. Square wave
With this source of power, the pfc circuit needs to rectify the square wave and add a small filter to remove the high dV/dt from the high voltage signal. This will give an almost DC signal as input to the pfc. With this small filter and rectifier the UCC28180 will work as required. If you don't have a filter on the input, the boost MOSFET may see large inductive voltage spikes which will damage the device. It may be enough to just add a small capacitor after the bridge rectifier.
This Cap?
This Cap?

4. Simulation result
263.4V

5. Vds
Sinewave
Square wave
317V
340V

6. Square wave
With this source of power, the pfc circuit needs to rectify the square wave and add a small filter to remove the high dV/dt from the high voltage signal. This will give an almost DC signal as input to the pfc. With this small filter and rectifier the UCC28180 will work as required. If you don't have a filter on the input, the boost MOSFET may see large inductive voltage spikes which will damage the device. It may be enough to just add a small capacitor after the bridge rectifier.
This Cap?
This Cap?

7. Vds
No change even if adding cap
Add cap
Sweep from 0 to 100nF