Implementation of Overmodulation in svpwm

I implemented FOC of PMSM with SVPWM. I tried to implement overmodulation in it with two zone overmodulation. The reference voltage magnitude from the current controller is 0.64 during rated speed and torque, at that time the modulating waveform reaches 1.05. so if we calculate MI it is approimately 1, (0.64/(2/pi)). But MI calculated with output voltage is 0.907. when i try to implement ovm then the MI goes till 0.957, ie.320V output. how to make to work in sixstep mode. whether my circuit is right

Answer 1

[Ayush]

Hi priya,

I understand that you are using FOC with SVPWM and trying to implement two-zone overmodulation where you want to enable six-step operation when MI exceeds linear/overmodulation limits.

From the give information above, I can defer that following could be the issues with SVPWM not switching to six-step even at high MI:

• Reference voltage might be clamped or mis-scaled.
• PWM generator might not be configured for full six-step logic.

You can try the following measures to move into six-step at high MI:

1. You can try switching to six-step mode when MI>1.0-1.05, else stick to SVPWM. This detects the overmodulation region.

2. Implement six-step using 6 sectors (60* each) based on rotor angle with hard switching of phase voltages.

3. You can verify that your system ensures full 0-100% duty cycle and that dead time is active.

You can read more about "SVPWM" here: https://www.mathworks.com/help/sps/powersys/ref/svpwmgenerator2level.html

You can read more about Field-oriented Control ("FOC") here: https://www.mathworks.com/help/mcb/gs/implement-motor-speed-control-by-using-field-oriented-control-foc.html?searchHighlight=FOC&s_tid=srchtitle_support_results_1_FOC

Hope it helps!