Something about single-phase Spwm inverter

Help! I have two questions. Later I will upload my simulation file. First, why I set the reference current of 5coswt (the same phase as the grid voltage) and set the PI controller but the current is not as expected of 5coswt but of 20coswt? As I inspect, the current is affected by the amplitude of the carrier wave and the coefficient of the saturation. The second question is why the amplitude of the current is affected by the amplitude of the carrier wave? I changed the set of the saturation and the result of the PI controller changed but the output of the Pi was always sine (amplitude was always below the saturation. Eg: saturation:-5 5 pi output: 4.8 saturation:-10 10 pi output:8.5). Also I moved the saturation away and change the amplitude of the carrier wave, the current changed too. I am so confused. Thanks!!!!

[Haotian Qiao]

waiting for your reply! It will be very helpful for me!!!

[Haotian Qiao]

COME ON  !HELP

Answer 1

[Charan Jadigam]

Hi,

I feel that the PI controller coefficients are not correctly tuned (as the error is not converging) using PID tuner as the model cannot be linearized. So instead change tuning method to ‘Frequency Response Based’ and tune the coefficients. But first make the system open loop in order to tune the coefficients and then later make it close loop and run the model.