After completing the following series of exercises, the student will understand the design of controllers for a doubly fed induction machine.
Real-time simulation results are shown in the laboratory panel.

Subsynchronous mode

• Load the model with the default settings.
• Apply an input torque of 0.2 p.u., then a reference speed of 240 rpm.
  • Does the measured torque follow the input torque?
  • Does the measured speed follow the reference speed?
    Hint: Look at waveforms under DFIM Control and Triggering Scopes to answer the questions above.

• Increase the input torque to 0.4 p.u.
  • How does the increase in input torque impact the rotor and stator currents?
    Explain your observation.
  • Does the measured torque follow the input torque?

Synchronous mode

• Set the input torque to zero.
• Set the reference speed to its nominal value of 277 rpm.
  • Does the measured speed follow the reference speed?
    Show your result.
• Increase the input torque to 0.2 p.u.
  • Observe the waveforms of rotor currents and explain their non-sinusoidal shapes.
  • Does the measured torque follow the input torque?
    Show your result.

Hypersynchronous mode

• Set the input torque to zero.
  • What do you expect as values for rotor currents?
    Explain.
• Set the reference speed to 280 rpm.
  • Does the measured torque follow the input torque?
  • Does the measured speed follow the reference speed?
• Increase the input torque to 0.5 p.u., then the reference speed to 304 rpm.
  • Show that the torque and speed controllers are working properly.
  • Show the current controllers for I_d and I_q are working properly.
    Hint: Showing the waveforms is enough as a solution.
• Increase the reference current I_d to 0.2 p.u.
  • Does the measured current I_d follow the reference?
    Show your result.
  • Waveforms 1: Save the waveforms of rotor and stator currents, via a screenshot, for example.
• Increase the reference current I_d to 0.4 p.u.
  • Waveforms 2: Save the waveforms of rotor and stator currents.
  • How does the increase in current I_d impact the rotor and stator currents.
    Hint: Analyze the results of Waveforms 1 and 2.