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Motion control of AC Induction Motors

Catwell

Controlling AC Induction Motors is a difficult task. A new project of mine will have me controlling the speed of an AC motor as well as direction. Anyone out there do this? And can you give me a push in the right direction?
 
 
UPDATE: I attached a PDF to this post that has been invaluable to my learning. Hope it helps.
 
 
Cabe
Attachments:
imageIM98VC1[1].pdf
imageflux observer.pdf
imagealexandru flux calculations.pdf
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  • 0

    Hi,

     

    At the moment I am modeling various components of the electric vehicle drive train and am stuck with my model of the Induction motor with Vector Control. My main problem is with the simulation of the vector control side. I am modeling in Matlab / simulink.
     
    The problem specifically relates to the rotor flux estimation. I worked my way through various books and papers (including the Ohm paper) to model an induction motor and a basic indirect vector control scheme (using clarke and park transform etc). And all references show models that can basically be imported into Matlab without too much problem. The input variables are often presented as the Torque or speed to define the quadrature reference and the rotor flux to define the direct reference. Both values together are then used to estimate the slip and are transformed using the Park inverse transform to come to the reference values for the pwm inverter.
     
    Now, all is reasonably clear but 1 thing:  how is the rotor flux value estimated? And I mean the value used as reference, like a speed value is used as reference.
    It is my understanding that this value is a constant and non zero (in a permanent magnet synchronous machine this value can be set to zero), but I am not sure about this. But it is a generated value (generated as a consequence of the stator current interaction with the squirrel cage rotor bars) so how can it be a constant (or kept constant)?
    I use a basic speed PI controller to calculate the iq_ref but how would I calculate the rotor flux reference value which I need to calculate id_ref?
     
    Any help would be much appreciated.
  • 0 in reply to mouch

    Are you running the motor in an open-loop or close-loop? I recommend closed-loop for a more accurate calculation.

     

    Rather than explaining what to do, I am going to attach a few documents I have regarding rotor flux estimation in the original post in this thread. You will need to reference, I am sure.

     

    Also, I believe what you are trying to accomplish has been done before: http://eprints.iisc.ernet.in/38226/

     

    Cabe

    Attachments:
    imageflux observer.pdf
    imagealexandru flux calculations.pdf
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