F28069 scalar (V/F) control of ACIM motor phase current distortion issue

This is not distortion but control instability.

You need tuning of closed loop control parameters, PI or whatever.

Hi Joy,

Open loop is used in my project. Anyway, Thanks.

Biao

Hi Biao,

Sensored or sensorless closed loop control is the cure for this kind of behaviour. Seems like mechanical instability caused by slot harmonics (combined with dead time effects).

Regards

Ibrahim

Hi Ibrahim,

Thanks for you reply. I agree to your analysis on the issue.

A sensorless V/F mode is used in my product. According to Ti's F2803x/6x scalar (V/F) reference code, I could not find any clue for a sensorless V/F with closed loop control. Could you please let me know how to do it?

The following is Ti's F2803x/6x scalar (V/F) reference code. I think there is only sensored closed loop can be selected.

// ------------------------------------------------------------------------------
//  Connect inputs of the RMP module and call the ramp control macro
// ------------------------------------------------------------------------------
    rc1.TargetValue = SpeedRef;        
    RC_MACRO(rc1)
    
// ------------------------------------------------------------------------------
//    Connect inputs of the PI modules and compute the PI speed
//    controller.
// ------------------------------------------------------------------------------  
    if (SpeedLoopCount == SpeedLoopPrescaler)
    {
      pi_spd.Ref = rc1.SetpointValue;
      pi_spd.Fbk = speed1.Speed;
      PI_MACRO(pi_spd);
      SpeedLoopCount = 1;
    }
    else SpeedLoopCount ++;
    
// ------------------------------------------------------------------------------
//    Connect inputs of the VOLT_PROF module for open-loop or closed-loop
// ------------------------------------------------------------------------------
    if (ClosedLoopFlag==FALSE)
     {    
          vhz1.Freq = rc1.SetpointValue;                    // Open-loop V/f control
          pi_spd.ui=0;
          pi_spd.i1=0;
      }
     else
          vhz1.Freq = rc1.SetpointValue + pi_spd.Out;    // Speed closed-loop V/f control

// ------------------------------------------------------------------------------
//    Call the volt profile macro
// ------------------------------------------------------------------------------
       VHZ_PROF_MACRO(vhz1);

// ------------------------------------------------------------------------------
//    Connect inputs of the SVGEN_MF module and call the space-vector gen. macro
// ------------------------------------------------------------------------------
    svgen_mf1.Gain = vhz1.VoltOut;     
    svgen_mf1.Freq = vhz1.Freq;  
    SVGENMF_MACRO(svgen_mf1);

// ------------------------------------------------------------------------------
//  Call the QEP macro (if incremental encoder used for speed sensing)
//  Connect inputs of the SPEED_FR module and call the speed calculation macro
// ------------------------------------------------------------------------------
    QEP_MACRO(1,qep1)

    speed1.ElecTheta = _IQ24toIQ((int32)qep1.ElecTheta);
    speed1.DirectionQep = (int32)(qep1.DirectionQep);
    SPEED_FR_MACRO(speed1)

// ------------------------------------------------------------------------------
//  Call the CAP macro (if sprocket or spur gear used for speed sensing)
//  Connect inputs of the SPEED_PR module and call the speed calculation macro
// ------------------------------------------------------------------------------
    CAP_MACRO(1,cap1)

    if(cap1.CapReturn ==0)                                 // Check the capture return
    {
        speed2.EventPeriod=(int32)(cap1.EventPeriod);    // Read out new event period
        SPEED_PR_MACRO(speed2)                              // Call the speed macro      
    }

// ------------------------------------------------------------------------------
//    Connect inputs of the PWM_DRV module and call the PWM signal generation
//    update function.
// ------------------------------------------------------------------------------
    pwm1.MfuncC1 = svgen_mf1.Ta;  
    pwm1.MfuncC2 = svgen_mf1.Tb;   
    pwm1.MfuncC3 = svgen_mf1.Tc;
    PWM_MACRO(1,2,3,pwm1)                            // Calculate the new PWM compare values   

Thank you for your help.

Biao

Yes.