1. Three Phase Induction Motor Dynamic Modeling and Behavior Estimation
Lauren Atwell
Jing Wang, Dr. Leon M. Tolbert
Auburn University, University of Tennessee
Final Presentation
July 17, 2014

2. Research Details and Schedule
Outline
Background
Research Purpose
Research Details and Schedule
Motor Model
Matlab Motor
Simulation Results
Conclusions

3. Background
Induction motors are widely used in industrial applications: they are rugged, reliable, and very efficient (from 85-97%).
Motor rotor speed / torque characteristics are controlled by motor drive for smooth transition / accurate behavior / stable operations.
While testing power electronics motor drive, induction motor dyno set requires mechanical load for different operating points, have a large footprint, and do not allow for variations in motor parameters.
Approximately $3200
Weigh 286 lbs. each

4. Research Purpose Induction motor modeling application:
Estimation of motor behavior for closed loop control in motor drive design
Induction motor behavior emulation for substituting dyno set with flexible converter
Verify my motor model with Matlab Simulink’s inherent integrated induction motor model
Matlab’s motor uses a dq reference frame that is more useful for motor drive design (rotor angle oriented, synchronous speed)
My model uses a dq reference frame that is easier for load emulation (voltage angle oriented, synchronous speed), while not different in abc domain behavior

5. Research Details and Schedule
Weeks 1-3
Background knowledge
Weeks 4-5
abc to dq coordinates
dq reference frames
Simulink
Week 6
Building my model
Verify with Matlab’s motor
Week 7
Simulation Structure
Simulation Results
Ideal Conditions
Load Variations
Vdq Filtering
Snchronous Frequency

6. Math behind a squirrel-cage induction motor
Background Knowledge
Layout
Stator and rotor
Math behind a squirrel-cage induction motor
Electrical
Mechanical
Torque
Need at least a graph showing the inside structure of induction motor, how is electrical circuit (motor drive or grid) connected in order to start it. Not necessarily have to show the equations here.

7. Schedule Weeks 1-3 Background knowledge Weeks 4-5
abc to dq coordinates
dq reference frames
Simulink
Week 6
Building my model
Verify with Matlab’s motor
Week 7
Simulation Structure
Simulation Results
Ideal Conditions
Load Variations
Vdq Filtering
Snchronous Frequency

8. Voltage is supplied with three-phase AC abc  αβ  dq
abc to dq Coordinates
Voltage is supplied with three-phase AC
abc  αβ  dq
dq coordinates allow all values to be constant 
Benefit of transforming abc to dq?
ϕ= angle
between dq and
αβ reference
frames

9. DQ Reference Frames Three reference frames: Synchronous
Reference is rotating at synchronous speed
Two types:
Rotor
Have to find the rotor angle (encoder or estimated)
More applicable for motor drive design
Matlab’s integrated model uses this reference frame
Stator synchronous
Use PLL to find the voltage angle
More applicable for load emulation
My model uses this reference frame
Stator (or Stationary)
d-axis is fixed to the stator phase-A winding
d-axis is rotating at the same relative speed as the rotor phase-A winding
Stationary-better when only concerned about stator variables (like in stator-fed induction motor drives) because the stator d-axis variables are identical to the stator phase A variables
Rotor-better when only concerned about rotor variables (like in speed rotor-fed induction motor drives) because the rotor d-axis variables are exactly the same as the rotor phase A variables
Synchronous-best because both the stator and rotor dq variables become steady DC quantities
When studying multimachine systems, the advantages of synchronous reference frame outweigh those of the other two

10. Simulink Learned to use Simulink
Building a simulation using Simulink’s integrated induction motor
Per-unit system
DQ coordinates
PWM block for voltage inputs
Simulink’s motor is in the rotor synchronous reference
Analyze the stator currents in dq, rotor speed and torque results

11. Matlab Model

12. Simulation Results—MATLAB
Rotor Speed
Time (sec)
Speed (rad/s)
no load
Time (sec)
Torque (Nm)
I think your waveform is right. For the direct line start of the motor with right Vabc 230 line to line rms, the time is around 0.9s, I double checked.

13. Simulation Results—MATLAB
Iabc
Time (sec)
Current (A)
Idq
Time (sec)
Current (A)
Be prepared you might be asked what’s the value of Vab (might be: duty cycle * Vdc * sqrt(3) for line to line rms, please double check).

14. Schedule Weeks 1-3 Background knowledge Weeks 4-5
abc to dq coordinates
dq reference frames
Simulink
Week 6
Building my model
Verify with Matlab’s motor
Week 7
Simulation Structure
Simulation Results
Ideal Conditions
Load Variations
Vdq Filtering
Snchronous Frequency

15. Building My Model
Mathematical manipulation to be able to use available inputs/outputs.
Uses ideal conditions (Vqs=1, Vds=0, Vqr=0, Vdr=0, wsyn = 1, no load) to verify it is producing expected waveforms compared with the simulation results from Matlab one.

16. Synchronous reference
Motor Model
Electrical
Sub-Model
Synchronous reference

17. Motor Model
Torque
Sub-Model
Mechanical
Sub-Model

18. Matlab Model Matlab Motor internal structure My Motor

19. Schedule Weeks 1-3 Background knowledge Weeks 4-5
abc to dq coordinates
dq reference frames
Simulink
Week 6
Building my model
Verify with Matlab’s motor
Week 7
Simulation Structure
Simulation Results
Ideal Conditions
Load Variations
Vdq Filtering
Snchronous Frequency

20. Simulation Structure Mathematical Model with PWM Inverter
Ideal Mathematical Model
MATLAB Model with PWM Inverter

21. Simulation Results—Ideal Conditions
Rotor Speed
Time (sec)
Speed (rad/s)
no load
Time (sec)
Torque (Nm)

22. Simulation Results—Ideal Conditions
Iabc
Time (sec)
Current (A)
Idq
Time (sec)
Current (A)

23. Simulation Results—Load Variations
Time (sec)
Speed (rad/s)
Time (sec)
Torque (Nm)

24. Simulation Results—Load Variations
Iabc
Time (sec)
Current (A)
Idq
Time (sec)
Current (A)

25. Simulation Results-Vdq Filtering
MATLAB
Model
Time (sec)
Voltage (V) My
Model
Time (sec)
Voltage (V)

26. Simulation Results—Synchronous Frequency
Frequency (Hz)
Time (sec)
ωfilter = 1730 rad/s

27. Conclusions
Established dynamic induction motor model behaviors have been verified for torque and rotor speed characteristics, regardless of supply
Established dynamic induction motor model enables flexible structure for various input conditions as well as dynamic behavior observation and estimation

28. Acknowledgements
This work was supported primarily by the Engineering Research Center  Program of the National Science Foundation and the Department of Energy  under NSF Award Number EEC and the CURENT Industry Partnership  Program.