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TIDA-010054: Reverse power flow, sec to prim does not work in closed loop.

Rob Hudson
Prodigy 30 points

Part Number: TIDA-010054

Tool/software:

Hi,

I have successfully implemented the LAB 3 exercise by implementing closed loop voltage mode control on my DAB, only when selecting closed loop operation after applying input power to the DAB. The voltage conversion/transformer ratio is 1:1. The SW version I am working with is Release: TIDA_010054 v2.00.00.00.

I have two problems that I would appreciate your assistance with.

1. The DAB does not start up properly if I set the DAB_clearTrip variable to 1 and DAB_closedGvLoop variable to 1 before applying input power to the DAB (closed loop). However, the DAB does start up correctly if I set the DAB_clearTrip variable to 1 before applying input power to the DAB (open loop). It appears as if the DAB_pwmPhaseShiftPrimSec_pu variable "latches" if the DAB is started up in closed loop. Is this perhaps related to the slew rate parameter DAB_VOLTS_PER_SECOND_SLEW that is used to determine the reference for the DAB in closed loop operation?

2. When I implement the closed loop reverse power flow test in LAB 5, the DAB does not start up properly either. Where in the code is the error measurement/calculation swapped from Vsec to Vprim for reverse power flow operation? It appears as if Vsec is always used as the voltage feedback parameter for DAB_gv controller.

Regards

Rob 

  • 0
    Prodigy 30 points

    Hi,

    I have a solution for point 2 mentioned above. I have been using v2 of the SW and v3 addresses the reverse power flow issue. I have implemented the reverse power flow and it works as expected.

    However, I am still not able to start-up the DAB in closed loop by ramping up the input supply from 0V as explained in point 1 above.

    Regards

    Rob

  • +1 in reply to Rob Hudson
    TI__Expert 5145 points

    Hi Rob,

    Sorry for the delayed response. I was out due to a public holiday here in Germany.

    The correct procedure for startup is to apply input power, then set DAB_clearTrip to 1 and then set DAB_closeGvLoop to 1.
    If you set DAB_closeGvLoop to 1 before input power is applied, the control loop will try to achieve the requested output voltage by increasing the phase shift. Since no input is applied the phase shift will saturate at the maximum. Now if input is applied, and the phase shift is already at the maximum you will push a lot of power immediately and will trip the system.

    You can add some additional checks to the software to avoid this behavior. For example a check that the input voltage needs to be greater than the requested output voltage before the control loop is executed.

    I hope this helps.

    Best regards,
    Andreas

  • 0 in reply to Andreas Lechner
    Prodigy 30 points

    Hi Andreas

    I have implemented a start-up procedure based on your recommendation.

    Regards

    Rob