Vector control of three-phase induction motor using artificial ...

VOL. 4, NO. 4, JUNE 2009 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences

©2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

VECTOR CONTROL OF THREE-PHASE INDUCTION MOTOR
USING ARTIFICIAL INTELLIGENT TECHNIQUE

Arunima Dey1, Bhim Singh2, Bharti Dwivedi1 and Dinesh Chandra3
1Department of Electrical Engineering, Institute of Engineering and Technology, Sitapur Road, Lucknow, India
2Department of Electrical Engineering, IIT, Delhi, India
3Department of Electrical Engineering, MNNIT, Allahabad, India
E-Mail: arunimadey@gmail.com

ABSTRACT
The controllability of torque in an induction motor without any peak overshoot and less ripples with good
transient and steady state responses form the main criteria in the designing of a controller. Though, PI controller is able to
achieve these but with certain drawbacks. The gains can not be increased beyond certain limit so as to have an improved
response. Moreover, it introduces non linearity into the system making it more complex for analysis. Also it deteriorates
the controller performance. With the advent of artificial intelligent techniques, these drawbacks can be mitigated. One such
technique is the use of Fuzzy Logic in the design of controller either independently or in hybrid with PI controller. This
paper proposes a unique set of fuzzy logics for the speed controller design to be used in vector controlled three phase
induction motor. The results obtained from the model using proposed Fuzzy Logic Controller and PI Controller are
compared. It can be concluded that use of Fuzzy logic improves and smoothens out the ripples in the motor torque and
stator currents. It also facilitates in limiting the magnitude of the torque and current values within the specified range in any
kind of disturbance, either provided by the speed removal or by sudden application and removal of load torque. This has
been verified through the simulation results of the model built completely in a MATLAB/SIMULINK environment.

Keywords: fuzzy inference system (FIS), fuzzy logic controller (FLC), membership function, vector control.

1. INTRODUCTION
The model of induction motor uses vector control and

The design of fuzzy logic as the name suggests is
Space Vector Modulated (SVM) voltage source inverter
unique in itself [1-3]. Depending on the speed and torque
(VSI). The simulated results thus obtained show improved
performances requirement of the three-phase induction
transients and steady state torque and speed performances
motor for various industrial application fuzzy controller
when compared with those of PI controller. The FLC is
with a unique inference system is designed. The
developed in MATLAB using Fuzzy logic toolbox.
performances of PI and fuzzy controller are compared in

[4] but it has considered only 15 rules for designing. It is
2. VECTOR CONTROL OF INDUCTION MOTOR
considered that more the rules, better is the performance of
Induction motor speed control methods are varied
the controller. The same has been projected in [5, 6]. Abad
in number of which vector or field oriented control is the
et al., in [5] have taken 49 rules for FLC and then
most widely accepted method. In vector control, the same
compared the results with that of PI controller. [6] Has
performance characteristics are obtainable as is the case
incorporated 21 rules and simulated the results. All the
with a dc motor. This is achieved by decoupling the three-
results obtained are for the step response of speed. Most of
phase winding into two windings (90° apart) so as to
the papers have not included sudden changes in speed or
facilitate independent control of torque and flux. A lot of
load. The proposed FLC in this paper incorporates all the
literature is available in this regard. The model of the
characteristics viz,
induction motor is a result of standard mathematical

equations described in [7, 8]. The model incorporates the
a) The starting of motor
non-linear blocks of induction machine and inverter as
b) Speed reversal
used in real time mode. Figure-1 shows the complete
c) Load application
model in which FLC has been introduced.
d) Load removal




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VOL. 4, NO. 4, JUNE 2009 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences

©2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com






Figure-1. Vector control of a variable-frequency induction motor drive incorporating FLC.

3. DESIGN OF FUZZY LOGIC CONTROLLER
according to the requirement of the speed. More number

of rules more accurate is the speed and torque
3.1 Fuzzy Inference System (FIS)
performance. Figure-2 explains the design of fuzzy
FIS consists of input block, output block and their
system.
respective membership functions. The rules are framed



Figure-2. Design of fuzzy system in MATLAB environment.



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VOL. 4, NO. 4, JUNE 2009 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences

©2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com

In this induction machine model, normalized
shows the b) and c) processes. For defuzzification centroid
values of two inputs in the form of speed error (e) and
method and for fuzzification mamdani method is used.
change in speed error (ce) and defuzzified value of torque
The normalized membership functions with 7 in number
command (du) as an output are considered. Basically,
for each and the 3-D surface view of the two inputs and
Fuzzy system includes three processes: a) Normalization
output are shown in Figure-3
b) Fuzzification and c) Defuzzification. The above figure




Figure-3. Normalized membership functions and 3-D surface view of the two inputs and output variables.

The control of the speed is done by the FLC taking into
4. RESULTS AND DISCUSSIONS
consideration following rules given in Table-1.


4.1 Starting
Table-1. Control expression of FLC.
Figures 4a and 4b show the starting characteristic

using FLC and PI controller respectively. Since the motor
ce
DB DM DS Z IS IM
IB
is started on no load, the currents of the stator gradually
e
picks up the values to full magnitude with reduced
DB
DB DB DB DB DM DS
Z
frequency as soon as the motor starts running, the speed
DM
DB DB DB DM DS Z IS
attained by it is the ref. speed and full frequency of the
currents are obtained. The electromechanical torque
DS
DB DB DM DS Z IS IM becomes zero, as the load torque is zero. The net flux both
Z
DB DM DS Z IS IM
IB
at stator and rotor remains constant.

IS
DM DS Z IS IM IB IB

IM
DS Z IS IM IB IB IB
IB
Z IS IM
IB IB IB
IB



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VOL. 4, NO. 4, JUNE 2009 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences

©2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.

www.arpnjournals.com




Figure-4a. Output through FLC.

ref torque n speed vs time
1

ref speed
0
ref torque
-1 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
actual torque n speed vs time
2

act speed
0
act torque
-2 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
stator currents vs time
i alpha
5

s
i beta
s
0
-5 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
stotor fluxes vs time
2

psi alpha
s
0
psi beta
s
-2 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
rotor fluxes vs time
1

psi alpha
r
0
psi beta
r
-1 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
starting characteristic


Figure-4b. Output through PI controller.

4.2 Speed reversal
actual speed follows it and tries to attain the reference
Figures 4c and 4d show the speed reversal
value at the minimum possible time. The torque Tem also
characteristic using FLC and PI controller respectively,
reduces drastically only to attain its reference value in the
when the reference speed is reversed at 0.30 seconds, the
minimum time. The current waveforms show a sharp


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VOL. 4, NO. 4, JUNE 2009 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences

©2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.

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increase in the magnitude with low frequency at the
and current performance characteristics of the motor
reversal of speed. The rotor and stator fluxes also have
especially during speed reversal. The peak-over shoot in
their frequency reduced for reversal speed. The
case of torque and current magnitude is very less and
implementation of FLC drastically improves the torque
restricted within limit using FLC unlike PI output.

1
ref speed
0
-1
ref torque
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
1
actual speed
0
-1
actual torque
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
6
Stator Currents
4
2
0
-20
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
1
Stator Flux
0
-1
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
1
Rotor Flux
0
-10
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45


Figure 4c. FLC output showing speed reversal at t = 0.3 seconds.

ref & actual torque,speed vs time
1.5
ref speed
1
actual speed(wm)
0.5
0
-0.5
actual torque(Tem)
-1
-1.5
-2
-2.5
-3
ref torque
-3.50
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
time in secs




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VOL. 4, NO. 4, JUNE 2009 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences

©2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.

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stator currents vs time
5
4
3
is alpha
s
2
1
0
-1
is beta
-2
s
-30
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45


stator fluxes vs time
1.5
psi alpha
s
1
0.5
0
psi beta
-0.5
s
-1
-1.50
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45




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VOL. 4, NO. 4, JUNE 2009 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences

©2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.

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rotor fluxes vs time
1
0.8
0.6
psi alpha
r
0.4
0.2
0
-0.2
-0.4
psi beta
r
-0.6
-0.8
-10
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45


Figure-4d. PI controller output showing speed reversal at t = 0.3 seconds.

4.3 Load application and load removal
Load removal

After the application of load torque at t = 0.12
Load application
seconds, the effect of load removal is considered on the
When the load is suddenly applied at t = 0.12
various parameters of the motor. When the load is
seconds, the Tem i.e. actual torque which was following
suddenly removed at t = 0.35secs, the Tem reduces
the reference torque earlier, now jumps to the value of
drastically and attains its settled value finally. The speed
load torque and settles to a magnitude of nearly 0.65.
follows the inverse law of torque Tem and hence ωm
Since, torque and speed are related to each other, so the
increases to settle down to its reference value. The
actual speed ωm too decreases when the load is applied.
magnitudes of stator currents face the consequences of
The nature of the stator currents have to face the
load removal by decreasing. The stator flux and rotor
effect of application of load and thus increases in
fluxes still remain unaffected.
magnitude at 0.12 seconds to meet out the sudden load
The waveforms are shown in Figures 4e and 4f
demand. The stator and rotor fluxes remain unaffected by
using FLC and PI controller, respectively. From the
the load application.
waveforms it is inferred that the constancy of flux is

maintained under any load condition.



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VOL. 4, NO. 4, JUNE 2009 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences

©2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.

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Load Application and Load Removal Characteristics
1
0.5
ref torque
ref speed
00
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
1
actual torque
actual speed
0.5
0
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
4
Stator Currents
2
0
-20
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Stator Flux
1
0
-1
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Rotor Flux
1
0
-1
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45


Figure-4e. Output Using FLC for load application and load removal characteristics.

ref torque n speed vs time
1.2

ref speed
ref torque
1
0.8
0.6
load removed at 0.35 secs
0.4
0.2
0
load applied at 0.12 secs
-0.2 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45




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VOL. 4, NO. 4, JUNE 2009 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences

©2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.

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actual torque n speed vs time
1.2

actual speed
data2
1
wm
Tem
0.8
0.6
0.4
0.2
load removed at 0.35secs
0
load applied at 0.12secs
-0.2 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45


stator currents vs time
5

i alpha
s
4
i beta
s
3
2
1
0
-1
-2 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45




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VOL. 4, NO. 4, JUNE 2009 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences

©2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.

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stator fluxes vs time
1.5

psi alpha
s
data2
1
0.5
0
-0.5
-1
-1.5 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45


rotor fluxes vs time
1

0.8
psi alpha
r
data2
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45


Figure- 4f. PI Controller output for load application and load removal characteristics.






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