What is an efficient way to do PID tuning in a model with long computing time?
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I'm modeling PID control of a variable frequency drive (VFD) on a centrifugal pump system in Simulink/Simscape. As I want the system to properly be controlled, I need to tune the PID parameters. More specifically, I solely focus on PI parameters. An inital open-loop simulation of solely the VFD with a step function shows the behaviour of the system. See picture below.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1409599/image.png)
However, when applying the VFD to the hydraulic model, the computing time drastically increases. To be explicit, computing one second of simulation time takes about 500 seconds real time. Therefore, tuning the closed-loop PI parameters takes an immense amount of time.
I am not alllowed to use the automated PID tuner, and am therefore limited to manual tuning. What would be a good way to handle the PI tuning here?
14 Comments
Mathieu NOE
on 15 Jun 2023
I am confused
I didn't noticed that your second image
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1411619/image.png)
is simply a zoom on the tiny overshoot at the end of the step response of the motor plot
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1411624/image.png)
so at the end I am completely lost in what data we see and are talking about (VFD alone / VFD + pump ? open loop , closed loop ? )
Accepted Answer
Dr Narayanaswamy P R Iyer
on 14 Jun 2023
You may use Ziegler-Nicholas step response or else frequency response method for tuning PID controllers.
More Answers (1)
Mohamad Nazir
on 13 Jun 2023
You can identify a second order transfer function model of your VFD from the open-loop step response (using overshoot, response time, etc.) then open a new model and insert that transfer function with PI(D) and tune its parameters quickly. That might provide you with a good initial guess which you ultimately have to manually tune on your model (with the hydraulic system).
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