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

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

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

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

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

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.

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

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

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

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

Matlab Model

Simulation Results—MATLAB Rotor Speed Time (sec) Speed (rad/s) Torque @ 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.

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).

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

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.

Synchronous reference Motor Model Electrical Sub-Model Synchronous reference

Motor Model Torque Sub-Model Mechanical Sub-Model

Matlab Model Matlab Motor internal structure My Motor

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

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

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

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

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

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

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

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

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

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-1041877 and the CURENT Industry Partnership  Program.