How can I remove the few peaks before the overshoot, so I only have the overshoot peak and then it directly transition into steady state?
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I built a buck converter ( circuit will be below):
The parameters are:
Vi = 12V, L = 33e-3, the R next to L =0.5, C = 680e-6 , R next to C= 5e-3, R = 10
This is the output voltage graph i got:
Currently I'm manually tuning the PI to achieve an overshoot of between 10% to 20% and a settling time of 0.01 to 0.1 these are no problem but I just can't remove the oscillations following the overshoot. Also when I change the value of D it mess up the whole graph. Is it possible to remove the oscillations so the overshoot follows directly into the steady state because no matter what I change p and I to it never removes the oscillation before the overshoot and changing d mess up everything
Hi Samuel. I found tuning the derivative to be difficult too. Eventually I settled in on P=3.5, I=850, D=0.01 and N=850. The default value of N was way too small. Here is the result.
More Answers (6)
Dr Narayanaswamy P R Iyer on 25 Feb 2022
You have NOT mentioned anything about triangle carrier frequency. First obtain output voltage response without PI controller. Then apply Ziegler-Nicholas chart to tune PI controller. Refine this kp and ki value for desired response.
TF is one method. You know the desired output voltage and duty-ratio D. Use this in the model to get open loop voltage response. Then apply Ziegler-Nicholas chart to obtain kp and ki. Then refine this PI controller parameters for desired output voltage closed loop response.
For 8 V output, your duty-ratio should be 2/3 (0.67) for given input voltage.
Zhao Wang on 26 Feb 2022
Since you have built a Simulink model for the buck converter, you may want to consider tune the PID controller based on the actual model behavior. For a switching buck converter, you will need to conduct frequency response estimation to identify a linear system description at the desired operating point. Using the linear plant model, you can use the PID Tuner App (can be opened from the PID controller block) to tune PID controller gains to achieve the performance you want.
Here is an example about the workflow above: https://www.mathworks.com/help/slcontrol/ug/design-controller-for-power-electronics-model-using-frequency-response-data.html
Antonino Riccobono on 28 Feb 2022
The difficulties you are encountering are understandable since when you tune a specific gain of your PID controller this will affect the other two. Therefore, manually tuning is not practical.
If you want to learn a systematic tuning workflow so that your feebback performance meets specific dynamic requirements, I invite you to consider the following training course:
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