you mean DC to 3phase AC inverter...
make a waveform diagrams of what you need.
to generate them you need clock, counter and decoder. depending on resolution you need decoder can be simple gates or ROM.
for example, suppose we use base 6 counter and each waveform has pattern with:
two positive clock cycles,
off cycle,
two negative clock cycles,
off cycle (then repeat).
your decoder would need to drive 6 gates (IGBTs):
(L1+)=gate1a=1,1,0,0,0,0
(L2+)=gate2a=0,0,1,1,0,0
(L3+)=gate3a=0,0,0,0,1,1
(L1-)=gate1b=0,0,0,1,1,0
(L2-)=gate2b=1,0,0,0,0,1
(L3-)=gate3b=0,1,1,0,0,0