My application of PI controllers lies in controlling dq components for developing control logic for PWM inverters. I find it really difficult to tune parameters of PI controllers as I am not getting the desired outputs.
Can any one suggest a proper method of handling tuning of multiple PI controllers for Inverter based systems ?
HI Amit,
For VSCs typically the d-q decoupled control system consists of outer control loop and inner control loop is used.
First try per-unitizing the controller inputs (i.e: [for outer loops Real power or DC voltage and Reactive power or the AC voltage], [for the inner loops direct current and quadrature current]).
Then try slow KI values for the outer control loops and fast Ki values for the inner control loops.
For example start with (for a per-unitized VSC control system)
Outer control loop ----- Kp = 1.5 and KI = 15
Inner control loop ----- Kp = 2.0 and KI = 60
NOTE: The controller parameters are highly sensitive to the AC system strength. So you may have to change the gains depending on your AC system.
Matlab Simulink :)
if you can mathematically model your plan simulink can tune the PI controllers
Greetings. A simple question before everything. What are you controlling? Power, Voltage, Power Factor...?
Maybe with more information, I can you relate some references in which modeling and PID tuning can be useful and will be robust for your system.
Obaidah AL-Sawalmeh: The automatic tune button do not work for complex systems. It gives error for the same.
@John Sandoval: Trying to control all the said parameters by vector control approach in PWM inverter.
Regards,
Amit
For vector control, usually there are 3 PI controllers:
2 inner current controllers for id and iq respectively, and 1 speed controller.
I am assuming that you are tuning for simulation. The simplest tuning will be the first order approximation approach. The tuning should start for the inner current controller. To do that, first disable the speed controller. This means that the iq reference should be manual (can use a step function in matlab for this), rather than from the speed controller. Set the Kp/Ki ratio to be equal to the effective L/R ratio of the machine. Give a step change to iq reference and observe the response of the current. Increase the value of Kp (while maintaining the ratio of Kp/Ki) until fast enough response is obtain. Take note that too high value for Kp will cause instability. Both PI controllers for id and iq can use the same Kp and Ki values.
After good current response is obtain, close the speed loop (include the speed controller). I do not have any good method for the speed PI tuning, but just bare in mind that the speed controller gains should be sufficiently slower than the gains for the inner current controllers.
Hope this helps.
@Hangseng Che : Thank you sir for your comments. I will try the same process as guided by you.
HI Amit,
For VSCs typically the d-q decoupled control system consists of outer control loop and inner control loop is used.
First try per-unitizing the controller inputs (i.e: [for outer loops Real power or DC voltage and Reactive power or the AC voltage], [for the inner loops direct current and quadrature current]).
Then try slow KI values for the outer control loops and fast Ki values for the inner control loops.
For example start with (for a per-unitized VSC control system)
Outer control loop ----- Kp = 1.5 and KI = 15
Inner control loop ----- Kp = 2.0 and KI = 60
NOTE: The controller parameters are highly sensitive to the AC system strength. So you may have to change the gains depending on your AC system.
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