How does three phase full converter work?
The sinusoidal wave is positive for 180 degrees.

The switched half-cycle is stepped on at 30 derees, and stepped down at 150 degrees to align withe she sinusoidal wave.

The positive half cycle is from 0 to 180 in the diagram below.



Here is some ascii art depicting the stepped approximation of a sine wave:

    ____________
___|            |______               ___
                       |_____________|
0  30          150    210           330 360