Hi guys, im new to 3-phase VFDs and i need advice.

Right now i only know how to design a 3-phase speed controller with square waves which looks like the follwing description: 120 degrees full +RMS, 60 degrees 0V, 120 degrees full -RMS, 60 degrees 0V, and so on, per phase. Is this sufficient to drive the induction motor or will it cause torque ripple and overheating?
Right now im superimposing PWM gating signals to overlap the totem pole IGBTs 3-phase gating signal in order to control voltage. The PWM gating signal is on the order of 10-20 times higher frequency than the three phase signal. Is this a very crude design? How do you produce sine waves with this on-off IGBTs, while having real time variable frequency/rpm and well as having variable torque-load on the motor? Dont mind using plc's. Thanks