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TMS320F2800137: Questions about D/Q aixs current decoupling for PMSM control

A.W
Intellectual 430 points
Part Number: TMS320F2800137

Tool/software:

Hi

There are some questions about D/Q axis current decoupling when using F280013X for PMSM sensorless control.

1. How to limit the Id/Iq PI loop' max/min output value. For normal PI loop, we limit the Id pi loop out with max vs (0.667* Vdc), and Iq loop with sqrt(vs*vs - Vd*Vd)

    but with D/Q decoupling, how the limit the current PI loop output value first? It seems that the Id loop's out will be small with decoupling feed forward.

2. How to limit the value of feed forward equation with d/q compensation , which you can see as obj->Vdq_out_V.value[0]  and obj->Vdq_out_V.value[1] as below code:

#ifdef  MOTOR1_DECOUP
        // -We*Lq*Iq, SI unit: We(rad/s)*L(H)*I(A)
        obj->Vdq_decoup_V.value[0] = (-speed_rps * objUser->motor_Ls_q_H * obj->Idq_in_A.value[1]);
 
        // +We*(Ld*Id+flux), SI unit: We(rad/s)*L(H)*I(A), Flux(wb)
        obj->Vdq_decoup_V.value[1] = speed_rps * (objUser->motor_Ls_d_H * obj->Idq_in_A.value[0] + objUser->motor_ratedFlux_Wb);

        obj->Vdq_out_V.value[0] += obj->Vdq_decoup_V.value[0];

        obj->Vdq_out_V.value[1] += obj->Vdq_decoup_V.value[1];
#endif

3.  In normal svgen mode of TI's demo, the max vs is 0.667* Vdcbus, then should I scale the obj->Vdq_decoup_V.value[0] and obj->Vdq_decoup_V.value[1]  with coeffient, like *0.5， or *0.667?

Regards

Arrow

  • 0
    TI__Guru** 114200 points
    A.W said:

    1. How to limit the Id/Iq PI loop' max/min output value. For normal PI loop, we limit the Id pi loop out with max vs (0.667* Vdc), and Iq loop with sqrt(vs*vs - Vd*Vd)

        but with

    It's the same as PI, the decoupling items are as a feedforward input to the PI controller.

    A.W said:
    2. How to limit the value of feed forward equation with d/q compensation , which you can see as obj->Vdq_out_V.value[0]  and obj->Vdq_out_V.value[1] as below code:

    It's not necessary to limit it. The values are calculated according to the motor parameters, but it can be limited as mentioned above.

    A.W said:
    3.  In normal svgen mode of TI's demo, the max vs is 0.667* Vdcbus, then should I scale the obj->Vdq_decoup_V.value[0] and obj->Vdq_decoup_V.value[1]  with coeffient, like *0.5， or *0.667?

    Total different. It doesn't have any relationship. You can refer to the codes in the example lab.

  • 0 in reply to Yanming Luo
    Intellectual 430 points

    1. The decoupling items seem to be the feedforward input to the Vd/Vq, not the PI controller.

    So, the feedforward items will be huge when motor in high speed. It seems that if we limit the Id/q 's PI loop out as normal setting, it seems that will not have a big influence.

    Yanming Luo said:
    It's the same as PI, the decoupling items are as a feedforward input to the PI controller.

    2. Can you share the link of example lab? I can't find the demo codes in the lastest motorcontrol SDK.

    Yanming Luo said:
    Total different. It doesn't have any relationship. You can refer to the codes in the example lab.

    Regards

    Arrow

  • 0 in reply to A.W
    TI__Guru** 114200 points
    A.W said:
    So, the feedforward items will be huge when motor in high speed. It seems that if we limit the Id/q 's PI loop out as normal setting, it seems that will not have a big influence.

    You need to check if the parameters and formula are conrect. The values should be very small.

    A.W said:
    2. Can you share the link of example lab? I can't find the demo codes in the lastest motorcontrol SDK.

    It's in Universal motor control lab.

  • 0 in reply to Yanming Luo
    Intellectual 430 points

    1. For my application, motor para. with Ld=Lq= 0.001H, Rs = 0.25Ω，4 paris PMSM, Rated voltage 360VDC, max 11000rpm

    Let's see the decoupling item for Vd: -speed_rps * objUser->motor_Ls_q_H * obj->Idq_in_A.value[1],

    which is -4 * 11000rpm/60 *2pi *0.001H * 20A = 92V   (with 11000rpm/20A Iq)

    It's not very small, compared with the rated voltage.

    In fact, it's almost equal to the output of Id loop when decoupling not enabled.

    So, I think there is some mis-understanding of this point for you.

    Yanming Luo said:
    You need to check if the parameters and formula are conrect. The values should be very small.

    2. To be honest, I can't find the decoupling code in the universal motor control lab with the latest motorcontrol SDK 5_03_00.

    Below is the motor_drive.c file. There is no related code in this file.

    /cfs-file/__key/communityserver-discussions-components-files/171/motor1_5F00_drive.c

    Yanming Luo said:
    It's in Universal motor control lab.

    Regards

  • 0 in reply to A.W
    TI__Guru** 114200 points

    If you make sure that the parameters and unit are correct, seems like there is no any issue since the speed and current are so high under this condition.

    Any issue you found when running?

  • 0 in reply to Yanming Luo
    Intellectual 430 points

    1. Yes, the decoupling function should have much effection in high speed.

    2. The control loop is not stable in high speed, with  big overshoot. So I think the limitation should be not the same as the traditional PI loop.

    3. Can you share the demo file of univeral control lab , I truely can't find it.

  • 0 in reply to A.W
    TI__Guru** 114200 points
    A.W said:
    2. The control loop is not stable in high speed, with  big overshoot. So I think the limitation should be not the same as the traditional PI loop.

    You can limit the calculated decoupling value as you mentioned.

    A.W said:
    3. Can you share the demo file of univeral control lab , I truely can't find it.

    The same as you used. Just add a threshold limitation.