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Can a motor controller be seen as a Current controlled source?

mouch

Hi,

 

For a Simulink model I would like to use a very simplified model of a motor controller based on a capacitor and a current controlled source. I am assuming the use of an 3 phase induction motor with motor controller based on a DC to AC inverter.

From what I understand, under regenerative braking the motor generates current which via the inverter  is turned into a DC voltage and current source, which I think can be approached using an Current controlled source and an capacitor.

 

To speed up my simulation, I do not want to simulate the full motor control and motor. I want to assume that the motor and controller can deal with what is expected and that I only see the current and voltages at the DC bus - to which I connect my batteries.

 

To this end, I have calculated the power profile at the bus (as seen by the batteries) based on a drive cycle, vehicle parameters, etc. This powe demand I divide by the voltage I expect at the bus to get the current which I then supply to the current controlled source and capacitor which then get connected to the rest of my model. For example, the battery.

 

My question is:

1. Can a motor controller be seen as a Current controlled source?

2. Are there any oversights I need to take in account if I want to take this approach?

 

Cheers,

Parents

  • If i'm not mistaking regerative breaking requires a separate system from the motor's controller to capture and store the energy. This system need to know when the power to the motor has stopped so it can engage and take the power from the motor, rectify it back to DC and charge the batteries.

     

    A motor controller for a 3 Phase induction motor is not a current limiting source. That kind of controller pulses the coils in the motor to make it spin. Those pulses are at a constant current and voltage. What controls the speed is the amount of time between the pulses.

     

    If you use a basic DC motor then your motor controller could be a current controlled source but it wouldn't do well as a generator.

Reply

  • If i'm not mistaking regerative breaking requires a separate system from the motor's controller to capture and store the energy. This system need to know when the power to the motor has stopped so it can engage and take the power from the motor, rectify it back to DC and charge the batteries.

     

    A motor controller for a 3 Phase induction motor is not a current limiting source. That kind of controller pulses the coils in the motor to make it spin. Those pulses are at a constant current and voltage. What controls the speed is the amount of time between the pulses.

     

    If you use a basic DC motor then your motor controller could be a current controlled source but it wouldn't do well as a generator.

Children
  • in reply to Former Member

    Michael Pilcher wrote:

     

    If i'm not mistaking regerative breaking requires a separate system from the motor's controller to capture and store the energy. This system need to know when the power to the motor has stopped so it can engage and take the power from the motor, rectify it back to DC and charge the batteries.

     

    A motor controller for a 3 Phase induction motor is not a current limiting source. That kind of controller pulses the coils in the motor to make it spin. Those pulses are at a constant current and voltage. What controls the speed is the amount of time between the pulses.

     

    If you use a basic DC motor then your motor controller could be a current controlled source but it wouldn't do well as a generator.

    thanks for the reply. So, if I assume that a motor controller with a motor act like they can deal with the speed and torque I am demanding than this would translate to a power equivalent profile over time. This power profile can than be simulated using a fixed voltage and a changing current, right?

    If the same assumtions are true for the motor controller with motor under regen braking (not interested in how it works, but just that it works) I can then say that at a (assumed) fixed voltage the current follows a similar power profile (albeit with a different sign to indicate that it leaves the controller instead of entering).

     

    cheers