a comparitve study between vector control and … · a comparitve study between vector control and...
TRANSCRIPT
A COMPARITVE STUDY BETWEEN
VECTOR CONTROL AND DIRECT
TORQUE CONTROL OF INDUCTION
MOTOR USING MATLAB SIMULINK
Submitted by
Fathalla Eldali
Department of Electrical and Computer Engineering
For the Degree of Master of Science
Colorado State University
Fall 2012
1
WHEN HAVE I BEEN INTERESTED IN
MOTOR DRIVE AND MATLAB?
BSC Senior Design
LIM + PLC
MATLAB/Simulink as A Modeling TOOL
2
THESIS OUTLINES Introduction
Induction Motor Principles
Induction Motor Modeling
Electric Motor Drives
Vector Control of Induction Motor
Direct Torque Control
Theoretical Comparison Vector Control and Direct Torque Control
Simulation Results
Simulation Results in the normal operation case
The effect of Voltage sags and short interruption on driven
induction motors
The characteristics of the voltage sag and short interruption
Conclusion & Future Work
3
INTRODUCTION Motors are needed
Un driven Motors and power consumption
Power Electronics, DSP revolution help
Rectifiers
Inverters
Sensors
Control Systems Theories
4
OLD STUDIES & MOTIVATION
Many studies have been done about FOC & DTC
individually
Few studies were published as a comparison
studies as [17-19]
Voltage Sag & Short Interruption faults were not
considered in the comparison
5
INDUCTION MOTOR PRINCIPLES
Nikola Tesla first AC motors 1888
AC motors
-Induction Motors
-Permanent Magnet Motors
Why are Induction Motors are mostly used ?
Supplied through stator only
Easy to manufacture and maintain
Cheap
6
INDUCTION MOTOR CONSTRUCTION
Stator :
laminated sheet steel (eddy current loses reduction) attached to
an iron frame
stator consists of mechanical slots
insulated copper conductors are buried inside the slots and then Y
or Delta connected to the source.
7
Two Types of Rotor
A-wound rotor:
-Three electrical phases just as the stator does and they
(coils) are connected wye or delta.
B-squirrel-cage’s rotor
-contains bars of aluminum or copper imbedded in the
rotor, which are short circuited at the end of each bar by an end
disc
8
INDUCTION MOTOR ROTOR TYPES (A)
WOUNDED ROTOR (B) SQUIRREL-CAGE
ROTOR.
9
ELECTRIC AC MOTOR DRIVES Practically, induction motor doesn’t work at its rated speed
Switching the (motor) on/off is possible by mechanically
stressful
decreasing the rotation speed is a better way to save energy
and reduce mechanical stress
10
PURPOSES OF ELECTRIC AC MOTOR DRIVES
11
INDUCTION MOTOR MODELING To model IM, We should know the electrical and mechanical
equations that describe it in the transient and steady state
The Electrical equations are for the Voltage, current, Flux
The Mechanical equations for the speed, position and Torque
12
IDEALIZED CIRCUIT MODEL OF THREE PHASE
INDUCTION MACHINE
13
ELECTRICAL EQUATIONS
14
MECHANICAL EQUATIONS
15
MACHINE MODEL IN ARBITRARY REFERENCE
FRAMES
Purpose of those Transformations:
Eliminate the effect of inductance changing with time
It is more convenient to be used in Unbalanced voltage
cases.
The other advantage is that we can observe any variable
at any instance.
16
17
RELATIONSHIP BETWEEN ABC AND QD
ARBITRARY COORDINATE REFERENCE FRAMES.
18
INDUCTION MOTOR MODELING
MATLAB/SIMULINK
Three phase to d-q stationary reference frame
d-q stationary frame to d-q synchronous frame
Electromagnetic Torque Equation modeling
19
THREE PHASE TO D-Q STATIONARY
REFERENCE FRAME
2
Vds_s
1
Vqs_s
u[1]
Vqs-s
f(u)
Vds-sVcs
Vbs
Vas
20
D-Q STATIONARY FRAME TO D-Q
SYNCHRONOUS FRAME
2
Vds_e
1
Vqs_e
Repeating
Sequence
Mux
Mux
f(u)
Fcn1
f(u)
Fcn
2
Vqs_s
1
Vds_s
21
ELECTROMAGNETIC TORQUE AND SPEED
EQUATION MODELING
22
1
Te
Product1
Product
-K-
Gain4
Add
4
Iqr-e
3
Ids-e
2
Idr-e
1
Iqs-e
Te
1
Speed
TL
1
s
Integrator
B
Gain2
-K-
1/J
1
Te
Wm
23
Vqs_s
Vds_s
Vqs_e
Vds_e
d-q (S) To d-q (E) Transformation
Wr
u[1]
Vqs-s
f(u)
Vds-s
Vcs
Vbs
Vas
Te
Vqr-e
d(Iqs-e)/dt
Ids-e
Wr
Idr-e
d(Iqr-e)/dt
Iqr-e
Subsystem3
Vds-e
Iqs-e
Iqr-e
d(Idr-e)/dt
d(Ids-e)/dt
Ids-e
Subsystem2
Vqs-e
d(Iqr-e)/dt
Ids-e
Idr-e
d(Iqs-e)/dt
Iqs-e
Subsystem1
Vdr-e
Iqs-e
Wr
Iqr-e
d(Ids-e)/dt
d(Idr-e)/dt
Idr-e
Subsystem
Step
1
s
Integrator
B
Gain2
-K-
Gain1
Iqs-e
Idr-e
Ids-e
Iqr-e
Te
Electromagnetic Torque
Calculation
0
Constant
Iqs-e
Iqs-e
Ids-eIds-e
Overall IM Model 24
1-VECTOR CONTROL OF INDUCTION MOTOR
Torque in separately excited dc motor
Principles of vector control of Induction motor
Torque equations for Vector Control
Vector Control MATLAB/SIMULINK
25
TORQUE IN SEPARATELY EXCITED DC MOTOR
26
SIMPLE REPRESENTATION OF SEPARATELY
EXCITED DC MOTOR.
27
PRINCIPLES OF VECTOR CONTROL OF
INDUCTION MOTOR
28
PRINCIPLES OF VECTOR CONTROL
(DECOUPLING BETWEEN ROTOR FLUX
AND TORQUE)
29
DERIVATION OF THE ORIENTATION CONDITION
30
PROCEDURE IN THREE MAIN POINTS
31
THE PROCEDURE USING MATLAB/SIMULINK
32
33
The last step is to convert the gotten component of stator current
in stationary reference frame to the desired three phase currents
to be the base of control the inverter
34
THE SIMULINK MODEL OF THE FIELD
ORIENTATION CONTROL (FOC) OF
INDUCTION MOTOR.
ids
iqs
Rotor flux angle
Actual speed
Stator currents
Output
To Workspace
Time
Terminator
Scope
Reference
Speed
ev iqs*
PI
Load
0.8
Landa_r*
Vabc
TL
iabc
N
Te
Landa_s
th
Landa_dr
Landa_qr
IM1
iabc*
iabc
Vabc
Determing the state
of the PWM
ids
iqs
th
iabc*
Current decoupling
controller
-K-
.
Overall FOC Model
35
2-DIRECT TORQUE CONTROL
The basic concept of (DTC) method was proposed by
Takahashi and Noguchi in 1986
It is more used in controlling the induction motor because it is
considered a simple and robust method
It has a very fast response and simple structure which makes it
to be more popular used in industrial world
It implies a comparative control of the torque and the stator
fluxes which must fall into two separate certain bands (limits)
to be applicable
36
SPACE VECTOR MODULATION OF
THREE PHASE VOLTAGE SOURCE
INVERTER WITH DTC
voltage vector is shifted (lag or lead) with respect to the
stator flux vector by an angle which is not more than 90°,
this causes the flux to increase and vice versa
The torque is then directly controlled by selecting the
inverter situation in order to boost the stator flux up or
buck it down.
37
SV-PWM
38
SV-PWM
39
BASIC PRINCIPLES OF SWITCHING TABLE
40
THE HYSTERESIS BAND CONTROLS THE STATOR
FLUX VOLTAGE AND
Increase Increase
Increase Decrease
Decrease Decrease
Decrease Increase
41
THE SIMULINK MODEL OF DIRECT TORQUE
CONTROL (DTC) OF INDUCTION MOTOR.
Step
Scope3
Repeating
Sequence
Relay1
Relayev Te*
PI
Output
Interpreted
MATLAB Fcn
MATLAB Fcn
0.8
Landa_s*
Vabc
TL
iabc
N
Te
Landa_s
th
IM
Overall DTC Model
42
LOOK-UP TABLE (SWITCHING TABLE)
Sectors
I II III IV V VI
FU TU V2 V3 V4 V5 V6 V1
FU TD V6 V1 V2 V3 V4 V5
FD TN V7 V0 V7 V0 V7 V0
FD TU V3 V4 V5 V6 V1 V2
FD TD V5 V6 V1 V2 V3 V4
FD TN V0 V7 V0 V7 V0 V7
43
THEORETICAL COMPARISON VECTOR CONTROL
AND DIRECT TORQUE CONTROL
44
SIMULATION RESULTS DTC Vs. FOC
Speed
Electromagnetic Torque
Flux
Three phase current
45
MOTOR SPEED RESPONSE.
0 1 2 3 4 5 6 70
50
100
150
200
250
300
350
400
Time (sec)
Moto
r speed (
r.p.m
)
FOC DTC
46
TORQUE RESPONSE
FOC DTC
47
FLUX RESPONSE
0 1 2 3 4 5 6 70
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Time (sec)
Sta
tor
Flu
x (
Wb)
0 1 2 3 4 5 6 70
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Time (sec)
Sta
tor
Flu
x (
Wb)
FOC DTC
48
THREE PHASE MOTOR CURRENT
0 1 2 3 4 5 6 7-4
-3
-2
-1
0
1
2
3
4
Time (sec)
Thre
e p
hase m
oto
r curr
ent
(Am
p)
0 1 2 3 4 5 6 7-15
-10
-5
0
5
10
15
20
Time (sec)
Thre
e p
hase m
oto
r curr
enr
(Am
p)
FOC DTC
49
THE DISTORTION OF THREE PHASE CURRENT
FOC DTC
50
THE EFFECT OF VOLTAGE SAGS AND SHORT
INTERRUPTION ON DRIVEN INDUCTION
MOTORS
(ASD) is considered as one of the sensitive loads to the
voltage sag and short interruption
That might cause the motor protection relay to trip,
because the undervoltage of the DC link
The ac current, which is feeding the motor, increases.
The speed usually deviates and the torque varies [29]
51
THE CHARACTERISTICS OF THE VOLTAGE SAG
AND SHORT INTERRUPTION
Two main types of Voltage Sag and interruptions
Balanced and Unbalanced
7 types of sags could happen as shown
52
SIMULATION RESULTS FOR THE CHOSEN PQ
ISSUES
The voltage sag types, which are used in this project thesis, are
Type A (Balanced) and Type B (Unbalanced). The short
interruption is applied on the two driving techniques too.
53
SIMULATION RESULTS FOR THE CHOSEN PQ
ISSUES
The affected DC Link Voltage
For FOC Vs. DTC , I observe the following:
Speed Variation
Three Phase Current
54
THE AFFECTED DC LINK VOLTAGE
One phase short
interruption’s effect on DC
link voltage (Type B)
55
DC VOLTAGE WAVE SHAPE UNDER THE
EFFECT OF TWO TYPES OF VOLTAGE SAG
CONDITION
56
TABLE THE DC LINK VOLTAGE IN
DIFFERENT VOLTAGE SAG PERCENTAGES AND
DIFFERENT DURATIONS (TYPE A)
Sag Duration (Cycles) 18 cycles 22 cycles 26 cycles 30 cycles
Voltages Sag (%)
20 % 314.75 314.6 314.51 314.2
40 % 236.5 236.4 236.4 236.4
60 % 159.7 156.28 156.26 156.26
80 % 155.4 126.2 102.49 83.55
100 % (interruption) 155.3 126.15 102.4 83.15 57
THE DC LINK VOLTAGE IN DIFFERENT
VOLTAGE SAG PERCENTAGES AND DIFFERENT
DURATIONS (TYPE A)
20 30 40 50 60 70 80 90 10050
100
150
200
250
300
350
Voltage Dip (Sag) %
DC
lin
k V
oltage
(Volt)
18 cycles
22 cycles
26 cycles
30 cycles
DC link in the normal operation is 400 Volt
58
SPEED VARIATION (DEVIATION) VOLTAGE
SAG TYPE A
20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
Voltage Dip (Sag) %
Speed D
rop
from
the d
esired s
peed %
18 cycles
22 cycles
26 cycles
30 cycles
20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
100
Voltage Dip (Sag) %
Speed D
rop f
rom
the d
esired s
peed %
18 cycles
22 cycles
26cycles
30cycles Motor Stall
FOC DTC
59
SPEED VARIATION TYPE A
Sag Duration
(Cycles)
18 cycles 22 cycles 26 cycles 30 cycles
Voltages Sag (%)
20 % 0% 0% 0% 0%
40 % 0% 0% 0% 0%
60 %
80 % (-15, +19) % (-43,+54) % (-66, +85) %
100 %
(interruption)
(-16, +19) % (-43,68) % (-67, +170) %
Sag Duration
(Cycles)
18 cycles 22 cycles 26 cycles 30 cycles
Voltages Sag (%)
20 % 0% 0% 0% 0%
40 % (0,+0.5)% (0,+0.5)% (0,+0.5)%
60 % (0,+0.5)% (0,+0.5)%
80 % STALLS
100 %
(interruption)
STALLS
FOC DTC
60
PEAK CURRENT DURING VOLTAGE SAG TYPE A
20 30 40 50 60 70 80 90 1000
5
10
15
20
25
30
Voltage Dip (Sag) %
Thre
e p
hase c
urr
ent
(Am
p)
18 cycles
22 cycles
26 cycles
30 cycles
3.67A "Normal current"
20 30 40 50 60 70 80 90 1000
1
2
3
4
5
6
7
Voltage Dip (sag) %
Moto
r C
urr
ent
(Am
p)
18 Cycles
22 Cycles
26 Cycles
30 Cycles
4.5A "normal current"Motor stalls
FOC DTC
61
PEAK CURRENT DURING VOLTAGE SAG TYPE A
Sag Duration
(Cycles)
18 cycles 22 cycles 26 cycles 30 cycles
Voltages Sag (%)
20 % 3.67 3.67 3.67 3.67
40% 3.67 3.67 3.67 3.67
60 % 3.95 3.98 4.1 4.06
80% 4.17 13.28 27.8 25.6
100 %
(interruption)
4.19 13.34 27.84 26.45
Sag Duration
(Cycles)
18 cycles 22 cycles 26 cycles 30 cycles
Voltages Sag (%)
20 % 4.5 4.5 4.5 4.5
40 % 4.5 4.5 4.5 4.5
60 % 4.6 4.84 4.5 4.5
80 % 4.7 4.84 6.8 1.5-3
100 %
(interruption)
4.84 4.87 6.8 1.5-3
FOC DTC
62
CONCLUSION Comparison Aspects FOC DTC
Speed Response Faster and more robust
Torque response Faster but spiky better torque response
flux response Slower and it is affected by the
load
Faster and stable
easiness of
implementation
Complicated because of the
transformation
Easy
V-sag/ Interruptions
Speed deviates gradually
Current increases gradually
Speed reaches 0 at certain point
Current doesn’t increase and it
falls suddenly
General Good Good 63
RECOMMENDED FUTURE WORK
Detailed analysis in comparing those two important methods
RT simulation should be done for full analysis of the other
power quality issues
In addition simulation should consider the protection system
for both under voltage and overvoltage
64
REFERENCES
[1] A. M. Trzynadlowski, Control of induction motors: Academic Pr, 2001.
[2] C. M. Ong, Dynamic simulation of electric machinery: using MATLAB/SIMULINK vol. 5: Prentice Hall
PTR Upper Saddle River, NJ, 1998.
[3] W. Theodore, Electrical Machines, Drives And Power Systems, 6/E: Pearson Education India, 2007.
[4] P. Vas, Vector control of AC machines: Clarendon press Oxford, 1990.
[5] N. Mohan and T. M. Undeland, Power electronics: converters, applications, and design: Wiley-India,
2007.
[6] T. Gonen, Electrical Machines With Matlab: CRC Press, 2011.
[7] K. S. Gaeid, H. W. Ping, and H. A. F. Mohamed, "Simulink representation of induction motor reference
frames," 2009, pp. 1-4.
[8] J. A. Santisteban and R. M. Stephan, "Vector control methods for induction machines: an overview,"
Education, IEEE Transactions on, vol. 44, pp. 170-175, 2001.
[9] X. Wang, Y. Yang, and W. Liu, "Simulation of vector controlled adjustable speed System of induction
motor based on Simulink," 2011, pp. 2563-2566.
[10] R. Lee, P. Pillay, and R. Harley, "D, Q reference frames for the simulation of induction motors," Electric
power systems research, vol. 8, pp. 15-26, 1984.
65
REFERENCES
[11] S. Masoudi, M. R. Feyzi, and M. Sharifian, "Speed control in vector controlled induction motors," 2009, pp. 1-5.
[12] K. Shi, T. Chan, and Y. Wong, "Modelling of the three-phase induction motor using SIMULINK," 1997, pp.
WB3/6.1-WB3/6.3
[13] A. Diaz, R. Saltares, C. Rodriguez, R. Nunez, E. Ortiz-Rivera, and J. Gonzalez-Llorente, "Induction motor
equivalent circuit for dynamic simulation," 2009, pp. 858-863.
[14] A. Iqbal, A. Lamine, and I. Ashra, "Matlab/Simulink Model of Space Vector PWM for Three-Phase Voltage
Source Inverter," 2006, pp. 1096-1100.
[15] F. M. Abdel-kader, A. El-Saadawi, A. Kalas, and O. M. EL-baksawi, "Study in direct torque control of induction
motor by using space vector modulation," 2008, pp. 224-229.
[16] S. Allirani and V. Jagannathan, "High Performance Direct Torque Control of Induction Motor Drives Using
Space Vector Modulation," International Journal of Computer Science, vol. 7.
[17] Y. Tang and G. Lin, "Direct torque control of induction motor based on self-adaptive PI controller," 2010, pp.
1230-1234.
[18] J. N. Nash, "Direct torque control, induction motor vector control without an encoder," Industry Applications,
IEEE Transactions on, vol. 33, pp. 333-341, 1997.
[19] H. Le-Huy, "Comparison of field-oriented control and direct torque control for induction motor drives," 1999, pp.
1245-1252 vol. 2.
[20] S. Vaez-Zadeh and E. Jalali, "Combined vector control and direct torque control method for high performance
induction motor drives," Energy conversion and management, vol. 48, pp. 3095-3101, 2007.
66
REFERENCES
[21] N.Mohan, “First Course on Electric Machines and Drives Videos,” 2010:
http://cusp.umn.edu/electric_drives.php
[22] B. M. Wilamowski and J. D. Irwin, "The Industrial Electronics Handbook-Power Electronics and
Motor Drives," ed: Taylor and Francis Group, LLC, 2011
[23] P. Tiitinen and M. Surandra, "The next generation motor control method, DTC direct torque
control," 1996, pp. 37-43 vol. 1.
[24] S. K. Sul, Control of electric machine drive systems vol. 88: Wiley-IEEE Press, 2011.
[25] A. Ansari and D. Deshpande, "Mathematical Model of Asynchronous Machine in MATLAB
Simulink," 2010.
[26] P. Wach, Dynamics and Control of Electrical Drives: Springer, 2011.
[27] D. Telford, M. Dunnigan, and B. Williams, "A comparison of vector control and direct torque
control of an induction machine," 2000, pp. 421-426 vol. 1.
[28] J. C. Gomez, M. M. Morcos, C. A. Reineri, and G. N. Campetelli, "Behavior of induction motor
due to voltage sags and short interruptions," Power Delivery, IEEE Transactions on, vol. 17, pp. 434-
440, 2002.
[29] J. Pedra, F. Córcoles, and F. Suelves, "Effects of balanced and unbalanced voltage sags on VSI-
fed adjustable-speed drives," Power Delivery, IEEE Transactions on, vol. 20, pp. 224-233, 2005.
[30] J. Gomez, M. Morcos, C. Reineri, and G. Campetelli, "Induction motor behavior under short
interruptions and voltage sags," Power Engineering Review, IEEE, vol. 21, pp. 11-15, 2001.
[31] M. H. Bollen and I. Gu, Signal processing of power quality disturbances vol. 30: Wiley-IEEE
Press, 2006.
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