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Forward ualpha/ubeta, ud/uq and backward ualpha/ubeta, ud/uq

Ronnie
Intellectual 750 points
Other Parts Discussed in Thread: CONTROLSUITE

The following figure is the typical and simple sketch for PMSM control, the forward ualpha/ubeta, ud/uq in the red ellipse are used for calculating SVPWM duty.

The three phase voltage ua,ub,uc of motor are sampled. Through Clarke and park transform, the backward ualpha/ubeta, ud/uq are generated.

1, What are the differences between the forward ones and backward ones?

2, Are their amplitude the same ?

3, If using sliding model observer to control motor, which ualpha/ubeta can be used for the observer, the forward one or the backward one?

  • 0
    TI__Guru** 119480 points
    alpha and beta are just values in the 2-phase coordinate system. you go from 3-ph (a,b,c) to 2-ph (alpha, beta) by using the Clark transform.
    backward are measured voltages from the system
    forward are voltages to apply to the system

    amplitude is not necessarily the same

    an observer uses the backward voltages to estimate the state of the rotor
    the controller creates and applies the forward voltages to the inverter to put the stator into an optimum state
  • 0
    TI__Mastermind 27200 points

    Ronnie,


    1, What are the differences between the forward ones and backward ones?

    Forward path variables represent the control effort imparted by the loop to achieve the desired response. These are voltages, represented in different co-ordinate systems and reference frames. The return path ("backward") variables represent the measured behaviour of the motor. These are currents, in the same co-ordinate systems and reference frames. The PI controllers compare the measured d-q variables with reference values and compute control action in terms of d-q voltages.


    2, Are their amplitude the same ?

    Not necessarily.

    3, If using sliding model observer to control motor, which ualpha/ubeta can be used for the observer, the forward one or the backward one?

    A sliding mode observer would use return path currents (Ialpha, Ibeta) and the forward path phase voltages (Valpha, Vbeta). For a more complete description, see the HVPM sensorless project for the HV motro control kit in controlSUITE:
    C:\ti\controlSUITE\development_kits\HVMotorCtrl+PfcKit_v2.1\HVPM_Sensorless_2805x - CCS5

    Also, you may find the DMC library documentation helpful:  C:\ti\controlSUITE\libs\app_libs\motor_control\math_blocks\v4.3\~Docs


    Regards,

    Richard