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problem with control using PID controller

ashish ahir
Expert 1020 points
Other Parts Discussed in Thread: CONTROLSUITE

I am using simulink and TI F28335 to implement close loop control logic via PID control.
Inverter output voltage drops by 4V when i connect resistive load.
How to overcome this?

  • 0
    Guru 192875 points
    Hi Ashish,

    I'm not sure what blocks you're using and how they function, also how it is realized in simulink. Simulink support is very bleak on this forum.
    This drop in voltage has to do with the control loop settings as its unable to maintain the output voltage. Hence the gain values have to be tuned correctly to achieve the same. Are you tuning the gain values using PSIM or similar simulators first or are you doing theoretical calculations?

    Regards,
    Gautam
  • 0 in reply to Gautam Iyer
    Expert 1020 points

    i am taking output voltage feedback to do control. Do i need output current feedback also?
    it is full bridge inverter. i am taking output voltage between cross lags using voltage divider.
    DC input for test is 30V.
    R=300Ohm only.
    I want to maintain its level at 20V peak.(coming 30V in open loop)

  • 0 in reply to Gautam Iyer
    Expert 1020 points
    i am doing manual tuning.
  • 0 in reply to ashish ahir
    TI__Mastermind 27200 points
    Ashish,
    Assuming your power stage can deliver the current you need, an inner current control loop will probably help. I recommend you look at the controller descriptions in the user's guides for the solar inverters on the C2000 application kits web page.
    From a control perspective you'll need to get high gain into the voltage loop at the inverter frequency. Some people use a P+R (Proportional plus Resonant) controller to achieve this. If current control doesn't completely solve the problem you may like to investigate that separately.
    Regards,
    Richard
  • 0 in reply to Richard Poley
    Expert 1020 points
    i have following difficulties.
    1)how to implement current loop logic
    2)i am not getting user's guides for the solar inverters on the C2000 application kits web page.
    3)"From a control perspective you'll need to get high gain into the voltage loop at the inverter frequency". why?
    4)is there any paper describing P+R method?
  • 0 in reply to ashish ahir
    Guru 192875 points

    ashish ahir said:
    1)how to implement current loop logic

    The PI loop libraries are available in controlSuite under : C:\ti\controlSUITE\libs\app_libs\motor_control\math_blocks\v4.3

    ashish ahir said:
    2)i am not getting user's guides for the solar inverters on the C2000 application kits web page.

    You can either refer to this doc: C:\ti\controlSUITE\development_kits\SolarExplorer_v1.0\SolarExplorer_PVInverter_F2803x\~Docs

    This has the info on current control.

    I didn't understand the rest of the 2 questions.

    ashish ahir said:
    4)is there any paper describing P+R method?

    Are you seeking info on designing a PR controller? If yes then refer this doc: http://www.mdpi.com/1996-1073/7/6/3934/pdf

    Regards,

    Guatam

  • 0 in reply to Gautam Iyer
    TI__Mastermind 27200 points

    3)"From a control perspective you'll need to get high gain into the voltage loop at the inverter frequency". why?

    Ashish,

    You will only get good control if you have high loop gain over the frequency range of interest.  The integral term in your PI controller will provide high loop gain at low frequencies, and therefore good DC performance, but this may not be true at the inverter frequency.  PR control is popular in inverter applications for this reason.

    Also, see this thread: https://e2e.ti.com/support/microcontrollers/c2000/f/171/t/451917

    Regards,

    Richard

  • 0 in reply to Gautam Iyer
    Expert 1020 points
    "You can either refer to this doc: C:\ti\controlSUITE\development_kits\SolarExplorer_v1.0\SolarExplorer_PVInverter_F2803x\~Docs"
    1)i have gone through this doc.
    2)still double loop control method is unclear.
    3)is there any doc which explains it in detail?
    4)why voltage is dipping in single loop control?
  • 0 in reply to ashish ahir
    Guru 192875 points
    According to my knowledge that's the only doc available for reference as of now but yes, if Ric has any he'll surely share with you :)
  • 0 in reply to Richard Poley
    Expert 1020 points
    i have attatched basic diagram of design for sigle loop control.