Full bridge HVDC to modfied square sine - random half side MOSFET burn
You would need something more sophisticated than TL494, a complete H bridge wit four outputs and dead time setting, to prevent conduction at once. Also with bootstrapping there is a possibility that you can't have 100% duty cycle (not sure on that). Furher there is no need both to switch both HI an LO side with PWM frequency, one can be ON/OFF and the other half is doing hard switching, you will get less loses.