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TMS320F28027F: how to make Dead time distortion correction

Dave Hunson
Expert 1760 points

Part Number: TMS320F28027F
Other Parts Discussed in Thread: CONTROLSUITE

Hi everyone!

I am using C:\ti\controlSUITE2_DMC Rev\development_kits\HVMotorCtrl+PfcKit_v2.1\HVACI_Scalar

DC voltage =550VDC

Poles =2 (1500RPM)

fmin =0.1  fmid=60Hertz  fmax =120Hz

V min= 3Volt  V max =550v

Dead time is 2.5us.

at the beginning of Start motor smoothly rotate but when motor speed up  (600RPM)  motor starts to  vibrate. and in 1300RPM we have vibration .

and current of leg shunt Resistors changes between 1A to 12 A ! 

it turns out that this problem happened because of  Dead time distortion.

in year of 1997 Mr. Dave Wilson published one Application note about that ,  it is so old method ,I am wondering if  TI has any solution for this problem.

How to detect the region of  current polarity in order to -DT of +DT?

would it be possible to detect it by current leg-shunt Resistor sensors? if so How to do it . 

is there any better way to do it?

thanks for attention.
Dave.

  • 0
    Expert 1760 points

    BTW,I read  AN form  dear Dave Wilson around 10 years ago in some section he pointed out that we can have distortion correction by LEM sensor ,since we used the Leg-Shunt resistor 

    I could get the current wave form and subtract and add (DT/2 ) to main PWM

    which my code goes some thing like this 

      gDeadTimeCorrection.DT[AdcCnt]=(_IQtoF(gAdcData.I.value[AdcCnt])>0)? -DeadTime:DeadTime;

    by doing that I could solve my problem about %70

    but  I want my motor rotate smoothly (now I sense vibration on my motor and current will change from 1A~ 4A in every rotation) 
    I don't know how to fine low magnitude region in order to apply +(DT/2 ) or -(DT/2 ).

    does  TI have any better solution  or code to solve these problem?

    please explain more about that.

    thanks

    Dave. 

  • 0 in reply to Dave Hunson
    TI__Guru** 116860 points

    Sorry, there is no new solution and code for dead time compensation except the using method in controlSUIET.

    Generally, the right dead time compensation value is based on the current direction.

  • 0 in reply to Yanming Luo
    Expert 1760 points

    hi dear Luo
    you mentioned "using method in controlSUIET."

    Q1:what method do you mean?

    Q2: please  tell me where can I find that method?

    regards.

    Dave.

    Yanming Luo said:
    using method in controlSUIET.
  • +1 in reply to Dave Hunson
    TI__Guru** 116860 points

    1. Install  ControlSUITE https://www.ti.com/tool/controlsuite

    2. Find the example project at the folder C:\ti\controlSUITE\development_kits\HVMotorCtrl+PfcKit_v2.1\HVPM_eSensorles

    3. Find the code below in the project.

    dbc1.scale = _IQdiv(_IQdiv2(pwm1.Deadband), dbc1.Ith); // uncomment to tune in debug
    dbc1.Kdtc = _IQmpy(dbc1.scale, dbc1.gain); // uncomment to tune " "
    PWMwDBC_MACRO(1,2,3,pwm1,clarke1,dbc1);

  • 0 in reply to Yanming Luo
    Expert 1760 points

    thanks dear Luo,

    I analyze the code and I have a question

    _iq type can't be more than -127 to 127 but dbc1.scale  is more than 60000 how to solve this problem.

    _IQdiv(_IQdiv2(pwm1.Deadband), dbc1.Ith);

    _IQdiv(_IQdiv2(120), 0.001); it is supposed to be 60000 but it is 127 because of limitation !!!

    Am I right ,would you please  explain about it?

    thanks 

    Dave.

  • +1 in reply to Dave Hunson
    TI__Guru** 116860 points

    dbc1.Ith is an _IQ value also, it is not equal to 0.001, should be _IQ(0.001), and the pwm1.Deadband will be converted to _IQ format also, not equal to 120.