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How to Tune PID Loop

ytan
Intellectual 325 points


Hi,

How do I tune the PID loop for the TMDSHVMTRPFCKIT, or digital motor controller in general?

I am at Incremental Build Level 3. 

The motor primer says while testing the PID, the dc bus voltage should not be too low, otherwise the outputs of the PID modules saturate. How do I tell what is the minimum voltage that I should run the test at?

Thanks !

 

  • 0
    TI__Mastermind 43730 points

    ytan,

    to know the DC bus voltage you need to know the motor DC power rating,

    Motor AC rating * 1.414 is a good ball park number for the DC bus value.

    Regards

    Manish Bhardwaj

  • 0 in reply to Manish Bhardwaj
    Intellectual 580 points

    Manish

    I am trying to implement a double loop PI controller for half bridge inverter and I am facing problems while I try to cascade the loops. The outer voltage PI seems to work OK. But can not cascade with inner current loop. To be more precise, I can even have the Kp term alone in current loop working (producing the low modulation ratio sine output). As we see in simulations, it is the integral  term  which is bigger produces the hi modulation ratio sine output and also produces the required 90 degrees phase shift that is needed for the proper closing of the loop.

    I thought of sending my implementation to you for your review to get a feedback of what is really wrong. The 'C' implementation is just about 20 lines. Can you help to fix the problem? Can you send a mail to "tetraups at yahoo.com " so that I can share the code with you?

    Awaiting your reply.

    Thanks

    Sayee

     

  • 0 in reply to Manish Bhardwaj
    Intellectual 325 points

    Hi Manish,

    If I know the DC power rating, how can I relate that to what is the minimum dc bus voltage that I can apply so that the PID modules will not saturate?

    Looks like Motor AC rating*1.414 is the peak voltage value. Since the bus voltage can be very high, can I modify some part of the code so that  I can test with lower dc bus voltage during initial bring up? Say, half the nominal dc bus voltage? 

    Thanks !!

     

  • 0 in reply to ytan
    TI__Mastermind 43730 points

    every motor behaves differently, no other way than testing it.

    At light loads it is possible to use low DC voltage,

    Regards

    Manish Bhardwaj