"Sharpening Skills.....
Serving Nation"
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459 (Online), Volume 4, Special Issue 1, February 2014)
International Conference on Advanced Developments in Engineering and Technology (ICADET-14), INDIA.
Application of Multilevel Inverter Using Modulation
Technique For Running Induction Motor Smoothly
Sandeep Kumar1, Ishtiyaque Ahmed2
1
Student, M.Tech, 2Assistant Professor, Dehradun Institute of Technology, Dehradun
Abstract - The Multilevel Inverter topology is advantageous
in high-power and power-quality demanding application
without use of transformer with reduced harmonic distortion.
This paper explain the basic type of Multilevel Inverter such
as diode clamped multilevel inverter (neutral point clamped),
flywheel capacitor multilevel inverter (capacitor clamped),
cascade multilevel inverter also the modulation and control
technique like Pulse Width Modulation, Space Vector
Modulation, Selective Harmonic Elimination are applied on
MLI and the gate signal through modulation technique is
given to MLI in such a way to reduce Harmonic Distortion
with the fact that when Induction Motor are fed through MLI,
motor run smother. Induction motor has advantage like
reduced total harmonic distortion and higher torque. The
effectiveness of the system is verified through simulation using
MATLAB / SIMULINK package
Keywords--Induction
Modulation technique
Motor,
Multi-Level
3- Reduce the stress in motor bearing by generating
smaller common mode voltage
4- Produce voltage with reduce harmonic content and
near sinusoidal waveform
The term Multilevel was first introduced by Nable el
al;[5] 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 [6] developed
for multilevel inverter.
Inverter,
I. INTRODUCTION
In two inverter technology output waveform is of two
values (level) include increase harmonic distortion, ripple
factor, higher voltage derivative, torque pulsation in
induction motor. Multilevel inverter [1]-[4] is considered as
a state of art power conversion from DC to AC for high
power and power quality demanding applications.
Multilevel inverter is useful in some application as
transport, mining, manufacturing and others. Recently they
have been proposed to enable new possibility for other
important applications like electronic and hybrid vehicle,
wind energy conversion, UPS, photovoltaic energy
conversion and others. Multilevel is suitable for high power
and power quality demanding application.
Some of the other feather of Multilevel Inverter is as
follows
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
Fig 1. (a) two levels, (b) three levels, (c) n levels
This paper emphasizes on the fact that when induction
motor are fed with Multilevel Inverter [7]-[9] it torque
pulsation are reduced and motor run smoothly. In this
manner efficiency of induction motor are also increase and
losses are reduced.
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
switching losses.
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"Sharpening Skills.....
Serving Nation"
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459 (Online), Volume 4, Special Issue 1, February 2014)
International Conference on Advanced Developments in Engineering and Technology (ICADET-14), INDIA.
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
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.
Diode Clamped Multilevel Inverter
In fig 3 three level and five level Multilevel Inverter are
shown. N is the neutral point [5]. Vdc is the input and C1 and
C2 are the two capacitor voltage connected to this input. For
three level the output voltage Van has three states: Vdc/2 , 0,
and –Vdc/2 . For voltage level Vdc/2 , switches S1 and S2
need to be turned on; for –Vdc/2 , switches S1’ and S need
to be turned on; and for the 0 level,S2 and S1’ need to be
turned on. Diode clamped inverter[5] have some advantage
over other type of multilevel inverter such as when number
of level are high enough harmonic content are low enough.
Inverter efficiency are high and control method are low. It
has some major drawback also like excessive clamping
diode are required when the number of level are high also
it’s difficult to control real power flow of the individual
converter in multi converter system.
Fig 3. Diode clamped multilevel inverter circuit (a) three level (b) five
level
Capacitor Clamped Multilevel Inverter
Fig 4 show the capacitor clamped multilevel inverter
[10]-[11]. It is also called flywheel capacitor inverter. The
basic difference between capacitor clamped multilevel
inverter and diode clamped multilevel inverter is that in
capacitor clamped multilevel inverter diode is replaced by
capacitor. In capacitor clamped multilevel inverter also Van
has three output voltage level that is Vdc/2 , 0, and – Vdc/2.
For voltage level Vdc/2, switches S1 and S2 need to be
turned on; for – Vdc/2, switches S1’ and S2’ need to be
turned on; and for the 0 level, either pair (S1,S1’ ) or
(S2,S2’) needs to be turned on.
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"Sharpening Skills.....
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459 (Online), Volume 4, Special Issue 1, February 2014)
International Conference on Advanced Developments in Engineering and Technology (ICADET-14), INDIA.
Clamping capacitor C1 is charged when S1 and S1’ are
turned on, and is discharged when S2 and S2’ are turned on.
Its advantage is large amount of capacitor can provide
capability during power outage and it provide switch
combination redundancy for balancing different voltage
level. The major disadvantage is large number of capacitor
is required when level is high also inverter control is very
complicated.
Fig 6. Cascade multilevel inverter with its waveform
Modulation and control strategies
Fig 4. Capacitor clamped multilevel inverter (a) three level (b) five
level
Cascade Multilevel Inverter
Cascade H-Bridge multilevel inverter [12]-[14] are
formed by series connection of two or more single phase
H-Bridge inverter. Fig 5 shows the basic diagram of
cascade multilevel inverter. Each single phase full bridge
inverter generates three voltage at the output +Vdc, 0, and –
Vdc. The H-Bridge inverter that are connected in series do
not necessarily need to have the same dc input voltage in
such manner we can generate different combination of
voltage levels and eliminate redundancies. Some
advantages of cascade multilevel inverter are that compared
to other it require least number of component to achieve
same number of voltage level also no extra clamping diode
and voltage balancing capacitor is required and it has less
switching loss, device stress. It drawback is that it need
separate DC sources for real power conversion.
Fig 6. Modulation technique for multilevel inverter
Switching state of a converter is a set of signal used to
control each switching device of power circuit. The above
control technique [15]-[21] are use to reduce harmonic
content by giving proper pulses to multilevel inverter.
There is inherent additional complexity of having more
power electronic device but it create possibility to take
advantage of the extra degree of freedom with the help of
these modulation and control technique. A very popular
method is the classic carrier based sinusoidal PWM which
use phase shifting technique to reduce the harmonic.
Another alternative is SVM, SHE, DTC etc.
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"Sharpening Skills.....
Serving Nation"
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459 (Online), Volume 4, Special Issue 1, February 2014)
International Conference on Advanced Developments in Engineering and Technology (ICADET-14), INDIA.
III. S IMULATION MODAL AND R ESULTS
For the validation of previously discussed approach,
simulation on three level diode clamped multilevel inverter
fed induction motor is carried out using Matlab Simulink.
Induction motor parameter are given below Motor typesquirrel-cage, 10 hp, 7.5 kw, 400 V, 50 Hz, 1440 RPM
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IV. CONCLUSION
Multilevel inverter are very useful in high power and
power quality application. Modulation method are getting
trend on multilevel inverter for better performance. When
these topology are applied on induction motor its
performance get increase compared to conventional
inverter. Torque pulsation get reduced and motor run
smoothly.
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Serving Nation"
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International Conference on Advanced Developments in Engineering and Technology (ICADET-14), INDIA.
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