Progress In Science and Engineering Research Journal
ISSN 2347-6680 (E)
FIELD ORIENTED CONTROL OF MULTILEVEL FED
INDUCTION MOTOR FOR DIFFERENT SPEED
Sandeep Kumar1, Ishtiyaque Ahamad2, Vinay Bhardwaj3, Neha Choudhary4
1,3.4
PG Student, 2Assistant Professor,
Department of Electrical and Electronic Engineering, Dehradun Institute of Technology, Dehradun
Abstract: This paper presents Induction Motor fed
independently thus to increase its transient response. In
through Neutral Point Clamped (NPC) or Diode Clamped
the rotating frame of reference the frame of reference in
Multilevel Inverter using Field Oriented Control. Field
regard to the phase A is named the d-axis (for direct
Oriented Control technique is used as it allows torque and
axis) and the other axis is named the q-axis (for
speed to be nearly controlled. Field Oriented Control
quadrature axis).
explains Induction Motor in relative simple term by using dq variable. Induction Motor when driven by Field Oriented
Controller, behaves as separately excited DC Motor to
control torque and flux independently and also to generate
pulses for Multilevel Inverter.
Multilevel Inverter is
advantageous then conventional Inverter as it synthesized
waveform near about sinusoidal waveform to reduce
harmonic
distortion.
This
paper
shows
Fig.1: Two reference model for rotating machine
IMPLEMENTATION and SIMULATION when Induction
Motor are driven at different speed.
When induction motors are controlled by a vector drive,
control computation is often done in the synchronous
Index Terms: Multilevel Inverter, Field Oriented Control,
Modulation Technique, D-Q transformation
frame. Since actual stator variables either to be
generated or to be measured are all in stationary a-b-c
I. INTRODUCTION
frame, frame transform should be executed in the
Field Oriented Control or Vector Control explains
control. The most popular transform is between
Induction Motor in relative simple term by using d-q
stationary a-b-c frame quantities to synchronously
variable. Three-phase induction motor can be modeled
rotating d-q quantities.
in an arbitrary two axis (d & q-axis) rotating reference
frame. It will be shown that when we choose a
synchronous reference frame in which rotor flux lies on
the d-axis, this model can estimate the stator current
along the direction of two-reference axis as shown in
fig.1 along D & Q axis. Induction Motor when driven
by Field Oriented Controller, behaves as separately
excited DC Motor to control torque and flux
Corresponding Author: Mr. Sandeep Kumar, PG Student,
Department of Electrical and Electronic Engineering, Dehradun
Institute of Technology, Dehradun
Email Id: sandeep.om.nain@gmail.com
Fig.2 Rotor Flux Oriented control scheme
Diode Clamped Multilevel is used in this paper. In
conventional Inverter technology output waveform is of
two values (level) include increase harmonic distortion,
© 2014 PISER Journal
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PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 075-080
Progress In Science and Engineering Research Journal
ISSN 2347-6680 (E)
ripple factor, higher voltage derivative, torque pulsation
purpose of speed control. In this paper induction motor
in induction motor. Multilevel Inverter is considered as
has been modeled by MATLAB program.
a state of art power conversion from DC to AC for high
power and power quality demanding applications.
Some of the other features of Multi level Inverter are as
fallow
II. MULTILEVEL INVERTER
Voltage source inverter produces an output voltage or
current with two levels. Two levels inverter have some
limitation in operating due to harmonic content and
1- The output generated voltage is of extremely low
distortion and lower voltage derivative
2- The switching frequency on which they are
operated are of lower order
3- Reduce the stress in motor bearing by generating
smaller common mode voltage
4- Produce voltage with reduce harmonic content
and near sinusoidal waveform
switching losses. Now it is easy to produce a high
power, high voltage inverter with multilevel structure
increasing the number of voltage or current level at
output terminals. Various PWM strategies are to be
applied on multilevel inverter to obtain quality output
voltage or current. The general purpose of multilevel
inverter is to synthesize a near sinusoidal voltage and to
reduce harmonic content and ripple factor. The number
of level of inverter can be defined as the number of
The term Multilevel was first introduced by Nable el al;
as number of levels increase in inverter the output
voltage has more steps generating a staircase waveform
with a reduced harmonic distortion but a higher number
increase the control complexity. PWM, SVM, SHE,
DTC etc are the modulation and control strategies
developed for multilevel inverter.
steps or constant voltage that is generated by inverter at
output terminal. Minimum three different voltage levels
have to be generated at output terminal to be called as
multilevel inverter. This is the basic difference between
two level inverter and multilevel inverter. Multilevel
inverter has an array of power semiconductor and
capacitor voltage sources thus generate output with
stepped waveform when proper switching is performed.
It eliminates the use of step up transformer. With this
phenomenon KV rating can be extended and it is
suitable for high voltage high current application. There
are three type of Multilevel Inverter named as Diode
Clamped Multilevel Inverter, Capacitor Clamped
Multilevel Inverter and Cascade Multilevel Inverter.
Diode Clamped Multilevel Inverter have same major
Fig 3. (a) Two levels, (b) three levels, (c) n levels
advantage then other topology in a manner that is does
not require separate DC source as in Cascade Multilevel
This paper emphasizes on the fact that when induction
motor are fed with Multilevel Inverter it torque
Inverter also does not require charging of capacitor as
in Capacitor Clamped Multilevel inverter.
pulsation are reduced and motor run smoothly. In this
manner efficiency of induction motor are also increase
In fig. three levels and five levels Multilevel Inverter
and losses are reduced. The dynamic model of the
are shown. N is the neutral point . Vdc is the input and
induction motor is necessary for understanding and
C1 and C2 are the two capacitor voltage connected to
analyzing the three-phase inductor motor for the
this input. For three level the output voltage Van has
© 2014 PISER Journal
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PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 075-080
Progress In Science and Engineering Research Journal
ISSN 2347-6680 (E)
three states: Vdc/2 , 0, and –Vdc/2 . For voltage level
above control technique are use to reduce harmonic
Vdc/2 , switches S1 and S2 need to be turned on; for –
content by giving proper pulses to multilevel inverter.
Vdc/2 , switches S1’ and S need to be turned on; and for
There is inherent additional complexity of having more
the 0 level,S2 and S1’ need to be turned on. Diode
power electronic device but it create possibility to take
clamped inverter have some advantage over other type
advantage of the extra degree of freedom with the help
of multilevel inverter such as when number of level are
of these modulation and control technique. A very
high enough harmonic content are low enough. Inverter
popular method is the classic carrier based sinusoidal
efficiency is high and control method is low. It has
PWM which use phase shifting technique to reduce the
some major drawback also like excessive clamping
harmonic. Another alternative is SVM, SHE, DTC etc.
diode are required when the number of level are high
also its difficult to control real power flow of the
individual converter in multi converter system
Current control PWM, as is used, because both flux and
torque are directly related to the current.
Fig.5 Modulation technique for multilevel inverter
IV.FIELD ORIENTED CONTROL
Field Oriented Control allows torque and speed to be
nearly controlled. Scalar Control is simple to implement
but have instability because of coupling effect which
indicate that if torque is changed flux change and vice
versa. This coupling effect must be decoupled to get
better performance. In Vector Control, Rotor Flux
Orientation gives natural decoupling control whereas
Stator Flux Orientation gives a coupling effect which
has to be compensated by decoupling compensation
current. Voltage modal flux estimation is better at
Fig.4 Diode clamped multilevel inverter circuit (a) three level (b)
five level
higher speed whereas current modal is made at any
speed. It is also possible to have hybrid modal where
III. MODULATION AND CONTROL
STRATEGIES
voltage modal is effective at higher speed and current
Switching state of a converter is a set of signal used to
explains Induction Motor in relative simple term by
control each switching device of power circuit. The
using d-q variable. Vector Control Induction Motor
modal at lower speed range. Field Oriented Control
© 2014 PISER Journal
http://.piserjournal.org/
PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 075-080
Progress In Science and Engineering Research Journal
ISSN 2347-6680 (E)
operates as separately excited DC Motor to get better
Where ids
response.
current, ψdr and ψqr are the d-axis and q-axis rotor flux
The three-phase induction is modeled into a two-phase
and iqs are the d-axis and q-axis stator
linkage. Rr is the rotor resistance, Lr and Lm is the rotar
model. We can look at the motor as a 2-phase machine.
inductance and mutual inductance respectively.
Utilizing of the 2-phase motor model reduces the
the slip frequency. Torque can be expressed in terms of
number of equations and simplifies the control design.
stator currents and rotor flux linkages as
Such a model is valid for any instantaneous variation of
T= ( ) Lm/Lr (ψdrsiqss – ψqrsidss)
voltage and current, and adequately describes the
performance of the machine under both steady-state and
is
Motor Parameter
transient operations. Vector control methods of the
induction motor permit independent control of the
torque and flux by decoupling the stator current into
two orthogonal component, a torque producing
Motor Type- Squirrel Cage, nominal power- 50*746,
voltage-460, frequency-60, stator resistance-0.087,
stator inductance- 0.8, rotar resistance- 0.228, rotar
inductance- 0.8, mutual inductance- 34.7
component iqs and a flux producing component ids.
The goal is to transform the three phase stationary
reference frame variable into two phase stationary
reference frame variable and then transform these to
synchronously rotating reference frame.
PI Controller Parameter
Kp-550, Ki- 150, Torque Limit- 350
V.SIMULATION MODAL AND
RESULTS
Transformation of three phase axes to two phase
stationary axes
For the validation of previously discussed approach,
[
inverter fed induction motor controlled by Field
]
simulation on three level diode clamped multilevel
Oriented Controller, is carried out using MATLAB
= [
][
]
Simulink.
Transformation of stationary axes to synchronously
rotating axes
Vqs = Vqss
- Vdss
Vds = Vqss
+ Vdss
Flux is expressed as
© 2014 PISER Journal
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PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 075-080
Progress In Science and Engineering Research Journal
ISSN 2347-6680 (E)
[6]. J Rodriguez, J.S. Lai and F.Z. Peng, “Multilevel Inverter: A
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Reddy
and
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Multilevel Inverter fed Induction Motor,controlled by
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harmonic content. Torque and Flux can be control
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1423.
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© 2014 PISER Journal
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PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 075-080
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© 2014 PISER Journal
http://.piserjournal.org/
PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 075-080