Three Phase Induction Motor Dynamic

Modeling and Behavior Estimation

Lauren AtwellJing Wang, Dr. Leon M. Tolbert

Auburn University, University of Tennessee

Final PresentationJuly 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

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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

8

c

b

f

f

f

f

f a

2

3

2

30

2

1

2

11

3

2

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

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

winding

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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

Simulation Results—MATLAB

12

Torque @ no load

Time (sec)

Rotor Speed

Time (sec)

Spe

ed

(ra

d/s

)To

rqu

e (

Nm

)

Simulation Results—MATLAB

13

Iabc

Time (sec)

Cur

ren

t (A

)

Idq

Time (sec)

Cur

ren

t (A

)

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

16

Electrical Sub-Model

Synchronous reference

Motor Model

17

Torque Sub-Model

Mechanical Sub-Model

Matlab Model

18

Matlab Motor internal structure

My MotorInternal structure

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

20

Ideal Mathematical Model

Mathematical Model with

PWM Inverter

MATLAB Model with PWM Inverter

Simulation Results—Ideal Conditions

21

Torque @ no load

Time (sec)

Torq

ue

(Nm

)

Rotor Speed

Time (sec)

Spe

ed

(ra

d/s

)

Simulation Results—Ideal Conditions

22

Iabc

Time (sec)

Cur

ren

t (A

)

Idq

Time (sec)

Cur

ren

t (A

)

Simulation Results—Load Variations

23

Time (sec)

Torq

ue

(Nm

)

Time (sec)

Spe

ed

(ra

d/s

)

Simulation Results—Load Variations

24

Iabc

Time (sec)

Cur

ren

t (A

)

Idq

Time (sec)

Cur

ren

t (A

)

Simulation Results-Vdq Filtering

25

MATLABModel

Time (sec)

Vo

ltag

e (

V)

MyModel

Time (sec)

Vo

ltag

e (

V)

Simulation Results—Synchronous Frequency

26

Fre

qu

en

cy (

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

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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.

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