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Overmodulation

Javier Vara
Expert 1575 points

Hello,

I am using a custom made inverter with the F28069 Piccolo series microcontroller.

As far as I know, everywhere I have looked at I have seen that in order to use overmodulation, current reconstruction is needed. Nevertheless, I wonder that if I use hall sensors to measure the phase current of the motor directly, there is not going to be any problem with the sensor not been able to measure the current properly as it would happen using shunt sensors in the legs of the inverter. Therefore I guess I do not have to use the current reconstruction algorithm.

In such case I guess that the only thing I would have to change in the code to allow for overmodulation is to increase the variable USER_MAX_VS_MAG_PU over 1.0. Isn't it?

Thanks

Javier

  • 0
    Expert 1575 points
    Another problem that we have faced is that we have noticed that as the DC Bus Voltage varies, so it does the offset of the voltage sensors and this translates to vibrations and jerk at low speed values. Is that normal? Is there a way to avoid this behaviour?

    The problem goes away as soon as you re-estimate the offsets but I wonder if it is possible to do it at run-time.
  • 0
    TI__Guru** 118000 points
    this thread discusses the phase current sensor measurements a bit
    e2e.ti.com/.../1266441

    you certainly can use over-modulation as you will always have valid current measurements...and yes, I think you can just set the overmodulation to your new value >1.0 and use the standard SVGEN (you don't need to use SVGEN_CURRENT in proj_lab10).

    for the voltage offsets, there isn't a solution to this today. If the offsets are tied to the bus voltage when they were calculated...we are looking at a solution but haven't published anything yet.