Hi,
Oh man, not again.....
What is with this inverter/VFD/UPS stuff, it seems to be a common "beginner project" around here, yet it's NOT (I repeat NOT) a simple project, I don't get it.
Is it possible that this is a school assignment at a certain class/school somewhere and whoever gets assigned the project "this year" always ends up here?

Anyway, as before, there are several ways of making the PIC output a frequency.
Generally speaking using a PIC with a CCP or ECCP or even PCPWM module is the way to go for these sort of things. The PWM feature of the these modules can often, but not always, be configured in half bridge mode. The 16F72 does not have this feature.