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MOSFET (Si/SiC) Forum Discussions

Rakesh_rp
Level 3
First solution authored 10 replies posted 10 questions asked
Level 3

Hi,

I am trying to tune the cascaded PI controller for 3.3kW  PFC.  The cascaded PI controller has outer voltage Loop and a inner current loop. How  should I approach to choose the correct  Kp , Ki values for both Loops for  different load current and for Input RMS voltage  of 200 to 250v.

CASCADED PI CONTROLLER LOOP

Rakesh_rp_0-1651730883261.png

 

 

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1 Solution
Guru_Prasad
Moderator
Moderator 50 solutions authored 100 replies posted First question asked
Moderator

Hello @Rakesh_rp 

Thanks for posting your question in Infineon community.

The Kp,Ki calculation explained in the below steps 

Step:1 Model your system(converter and controller) and write equations in Continuous Domain(S-domain) and convert in Discrete Domain(Z-Domain).

Step:2 add if any delay is presented in the system and write an open-loop transfer function.

Step:3 Plot Bode plots (Magnitude and Phase Plot) and check the system stability. The stability can check by using the Phase margin.

Step-4 Kindly maintain a phase margin of 45 deg and accordingly tune your Kp and Ki Values.

Step-5 Try to model your outer voltage loop separately and your inner loop separately.

Note: Outer loop should be slower than the inner loop accordingly inner loop Kp, Ki should be selected 

Thank you

Guru

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Guru_Prasad
Moderator
Moderator 50 solutions authored 100 replies posted First question asked
Moderator

Hello @Rakesh_rp 

Thanks for posting your question in Infineon community.

The Kp,Ki calculation explained in the below steps 

Step:1 Model your system(converter and controller) and write equations in Continuous Domain(S-domain) and convert in Discrete Domain(Z-Domain).

Step:2 add if any delay is presented in the system and write an open-loop transfer function.

Step:3 Plot Bode plots (Magnitude and Phase Plot) and check the system stability. The stability can check by using the Phase margin.

Step-4 Kindly maintain a phase margin of 45 deg and accordingly tune your Kp and Ki Values.

Step-5 Try to model your outer voltage loop separately and your inner loop separately.

Note: Outer loop should be slower than the inner loop accordingly inner loop Kp, Ki should be selected 

Thank you

Guru

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