actually i know sir that i need to use a comparator for comparison but form realization through software .....how it can be done by....is is like that we need to store the pulse widths and than issuing than again and again.
It is not clear what you are talking about. Where does the triangular wave come from, is the sinus the 3 phase power or something you create. Since you are doing AC to DC what are the IGBTs doing? What are the pulse withs doing and howare they generated are they for driving a DC motor,are they for sipping from the 3 phase.

6 IGBTs sound as if you are making a drive for a 3 phase AC motor, is that it?

Spend some time and tell us EXACTLY what you are doing.

Erik

Erik