the STATCOM has 4 PI controllers:
i) one PI for ac voltage regulation
ii) one PI for dc voltage regulation
iii) two PI for d and q axis current controllers.
If the MATLAB PID-tune tool is used for tuning of PI controllers, all the PI controllers cannot be tuned simulataneously. Even if 1 PI controller is tuned to give desired response, while tuning of other PI controller, the response of the first PI controller is affected.
Tuning using trial and error method also doesnt work.
What are he other ways of tuning these PI controllers? Can any algorithm be used for tuning all the controllers?
try SUI PID controller explained in detailed in rhe following paper
https://www.researchgate.net/publication/276911267_A_Novel_Simplified_intelligent_Universal_PID_Controller?ev=prf_pub
Conference Paper A Novel Simplified intelligent Universal PID Controller
Dear Tushar M,
Look the link. May be useful.
https://www.youtube.com/watch?v=U4oQH-9Yj-Q
http://maxwellsci.com/print/rjaset/v4-768-774.pdf
Regards, Shafagat
Dear Tushar,
First of all, I think the tuning is not just a numerical problem and you should put your focus on system modeling and then control design.
The STATCOM problem you mention is a typical cascaded loop system. In your case the outer loops are dc and ac voltage and the current controllers the inner ones. The basic rule to tune cascaded controllers is that inner loops should be much faster than outer loops. Fast means that the closed loop bandwidth frequency is bigger. An usual rule is to make 10 times faster the inner loop, but in practice this is not always feasible, since the IGBTs PWM frequency also limits the bandwidth of inner current controllers: the one tenth rule also applies for current controller bandwidth and PWM/control frequencies.
Many of the most releveant papers/books in power electronics applications such as wind turbines, FACTs, HVDC etc well address the tuning procedure.
Generally, there is two major method for your problem: Optimization methods, and system modeling methods.
By optimization, you may use an intelligent optimization methods (e.g. GA, PSO and so on), to find the optimum point for all of your 8 parameters (4 P and 4 I).
Or you can identify and model your system first, and then try to design the controller based on the model. For instance, if you have obtained a linear control, you can simply select P and I parameters based on linear control rules, or otherwise, little more complex nonlinear control...
Practically speaking, these two ways are useful to find the best parameters for STATCOM. I suggest not to search in the control methods such as step-by-step design, and so on.
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