Three Phase Induction Motor Dynamic Modeling and Behavior

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

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

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 3

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 4

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 5

Background Knowledge • Layout Stator and rotor • Math behind a squirrel-cage induction motor Electrical Mechanical Torque 6

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 7

abc to dq Coordinates • Voltage is supplied with three-phase AC • abc αβ dq • dq coordinates allow all values to be constant ϕ= angle between dq and αβ reference frames 8

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 Rotor § d-axis is rotating at the same relative speed as the rotor phase-A winding 9

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 10

Matlab Model 11

Speed (rad/s) Simulation Results—MATLAB Rotor Speed Time (sec) Torque (N m) Torque @ no load Time (sec) 12

Simulation Results—MATLAB Current (A) Iabc Time (sec) Current (A) Idq Time (sec) 13

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 14

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. 15

Motor Model Electrical Sub-Model Synchronous reference 16

Motor Model Torque Sub-Model Mechanical Sub-Model 17

Matlab Model Matlab Motor internal structure My Motor Internal structure 18

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 19

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

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

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

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

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

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

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

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 27

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. 28