Hi sudhaa30,
Which microcontroller do you have in mind? PIC? AVR? ARM? or other?
For transformerless, at 80W power, it is possible. First step up the dc 12v to about 300vdc using the microcontroller or PWM IC and MOSFET/IGBT with BOOST topology and then use microcontroller to pulse the 3phase MOSFET/IGBT bridge. I'm guessing it should be sine wave output, so you have to implement sinusoidal PWM. Hope you have an idea on this, if not there are plenty of resources out there explaining it.