PROJECT REPORT ON SIMULATION AND STUDY OF MULTILEVEL INVERTER.

1. SIMULATION AND STUDY OF
MULTILEVEL INVERTER
UNDER THE GUIDANCE
OF:
PROJECT SUBMITTED BY:
ELECTRICAL ENGINEERING DEPARTMENT

2. LIST OF TOPICS
1. Abstract
2. Introduction
3. Literature Review
4. Objectives
5. Problem formulation
6. Solution Methodologies
7. Multi Level Inverter
8. Results & Conclusion
9. Future Scope
10. References

3. ABSTRACT
Nowadays multilevel inverters are a very attractive solution for medium-voltage high-
power conversion applications; they convert DC power to AC power at required output
voltage and frequency level. Three-phase Multi Level Inverter (MLI) are used in many
medium and high-power applications such as motor drives and grid connected systems.
There are numerous Pulse Width Modulation (PWM) techniques for MLIs. In this
project, a three phase five level inverter has been simulated using Sinusoidal PWM
technique using MATLAB/Simulink. This technique is recommended to improve the
performance of inverter and to eliminate the filtering requirements.
The topology used here is that of cascaded H bridge inverter. In this, separate DC sources
are used for each H bridge. If the value of DC voltage is same in all the bridges, then it
can simply be called as a cascaded multilevel inverter. In case of different DC voltage
being used in different H bridges, then it is called a Hybrid multilevel inverter.

4. INTRODUCTION
 An inverter is an electrical device which converts the DC voltage into
AC voltage so that it can be used by common appliances.
 The inverter output can be single phase or polyphase and it can be
two level or multilevel.
 The concept of multilevel Inverter (MLI) is a kind of modification in
two-level inverter.
 In high-power and high-voltage applications two-level inverters
however have some.
 This is where multilevel inverters are advantageous.

5. Sr. No. Paper Author Name Year Contribution Gap/Scope
1 Generalized
structure of a
Multilevel PWM
inverter
Pradeep M. Bhagwat 1983 A generalized
structure of a
multilevel voltage
source thyristor
inverter is
proposed.
Multilevel
Inverter
Topologies.
2 High performance
current control
techniques for
applications to
multilevel high-
power voltage
source inverters,
university of
Genova (Italy)
M. Marchesoni 1989 High-performance
current control
techniques have
been developed.
Extension to three
phase system is
possible.
LITERATURE REVIEW

6. Sr. No. Paper Author
Name
Year Contribution Gap/Scope
3 Cascade Multilevel
Inverters for Utility
Applications, Oak
Ridge National
Laboratory, Tennessee
F. Z. Peng, J. W.
McKeever & D.
J. Adams
1997 Cascade multilevel
inverters have been
developed.
Lower output
voltage rating than
conventional
multilevel Inverter,
that can be raised
further.
4 Novel Multilevel
Inverter Carrier-Based
PWM Methods,
School of Electrical
and Computer
Engineering Atlanta
Leon M. Tolbert
& Thomas G.
Habetler
1998 Two novel carrier-
based multilevel
PWM schemes are
presented.
This topology can
be used to enable
better switch
utilization.
5 Extension of PWM
Space Vector
Technique for Voltage
Source Inverters
Multilevel Current-
Controlled
J. Mahdavi', A.
Agah, A. M.
Ranjbar & H.
A. Toliyat'
1999 A current control
method using SV
for voltage source
inverters was
discussed.
The proposed
method can be
implemented by
application of
microprocessor-
based controllers.

7. Sr.
No.
Paper Author
Name
Year Contribution Gap/Scope
6 Multilevel Inverter
with Series
Connection of H-
Bridge Cells, Power
Electronics Research
laboratory, National
Yunlin University of
Science and
Technology
Bor-Ren Lin,
Yuan-Po Chien &
Hsin-Hung Lu
1999 A novel converter
topology, a three-
phase switching
mode rectifier
(SMR) and a
three-phase
multilevel inverter
with separately dc
power supplies, is
proposed.
Different circuit
topologies can
used for switching
mode dc/dc
converters.
7 A Generalized
Multilevel Inverter
Topology with Self
Voltage Balancing,
Oak Ridge, Tennessee
Fang Z. Peng 2000 Generalized
inverter topology.
The existing
multilevel inverter
topologies can be
derived from
generalized
inverter topology.

8. Sr. No. Paper Author Name Year Contribution Gap/Scope
8 New Multilevel
Inverter Topology
with reduced number
of Switches using
Advanced Modulation
Strategies
S. Nagaraja Rao,
D.V. Ashok Kumar
& Ch. Sai Babu
2013 New class of three
phase seven level
inverter based on a
multilevel DC link
(MLDCL) and a bridge
inverter to reduce the
number of switches.
MLDCL can be used
for both Flying
capacitor and Diode
clamped inverter for
their performance
enhancement.
9 A Brief review on
multilevel inverter
topologies
Amol K. Koshti &
M. N.Rao
2017 The brief review of
multilevel inverter
topologies and
introduction to control
strategies used for
MLI’S.
Reduction of
switches in case of
various types of
Multilevel Inverter.

9. OBJECTIVES
 In order to overcome the problem of distortion in the output voltage
waveform caused due to the presence of harmonics, this project
proposes the modelling of a Five-Level Inverter using
MATLAB/SIMULINK. The objectives of the work are:
 To study and simulate a three phase five level Voltage Source
Inverter.
 Comparison in performance of three-level and five-level inverters.
 To understand and implement Pulse Width Modulation for
minimization of filtering requirements.

10. PROBLEM FORMULATION
 In high-power and high-voltage applications three-level inverters
have some limitations in operating at high frequency.
 Three-level inverter incorporates considerable values of Total
Harmonic Distortion (THD).

11. SOLUTION METHODOLOGIES
 Implementation of Five-Level Inverter so as to overcome the
limitations associated with the use of low-level inverters:
 1)Increasing the inverter levels will result in an output waveform
which is closer to the sinusoidal waveform.
 2) The unique structure of Multi-Level inverter allows them to reach
high voltages with low harmonic distortion without the use of
transformers.

12.  The concept of multilevel converters has been introduced since 1975.
 The term multilevel began with the three-level converter.
 Capable of producing output in stepped staircase form.
 Produces output with low distortion.
 Subsequently, several multilevel converter topologies have been
developed.
MULTILEVEL INVERTER

13. 1) Diode clamped (neutral-clamped)
2) Flying capacitors (capacitor clamped) and
3) Cascaded H-bridges converter with separate dc sources.
Three major multilevel converter structures are:

14. A three-level inverter is a modification of basic two-level inverter.
The topology used here is that of cascaded H bridge inverter. In this,
separate DC sources are used for each H bridge.
 If the value of DC voltage is same in all the bridges, then it can
simply be called as a cascaded multilevel inverter.
 In case of different DC voltage being used in different H bridges,
then it is called a Hybrid multilevel inverter.
THREE LEVEL INVERTER

15. SIMULATION MODEL
(Fig.6- Simulation model of three-level inverter)

16.  Sinusoidal PWM technique has been utilized.
Switching Scheme
(Fig.5 -Switching scheme for three level inverter)

17. SIMULATION RESULT
(Fig.7-Output Voltage Waveform of three level inverter) Ref.

18. FFT ANALYSIS
(Fig.9 – FFT Analysis of voltage signal)

19. FIVE LEVEL INVERTER
In the Five level Inverter model, the following scheme has been implemented:
 Switching Scheme– Sinusoidal PWM
 Power Supply – 100V DC each
 Switches – IGBT
 Load – R-L load
 Measurements

20. SIMULATION MODEL
(Fig.9-Simulation model of three phase five-level inverter)

21.  Sinusoidal PWM technique has been utilized.
Switching Scheme
(Fig.10- Switching scheme for the five-level inverter)

22. SIMULATION RESULT
(Fig.11- Output voltage waveform of five-level inverter)
Ref.

23. FFT ANALYSIS
(Fig.9 – FFT Analysis of voltage signal)

24. Advantages:
 Better waveform quality of output voltage (more sinusoidal).
 Reduced dV/dt, leading to reduction in EMI.
 Multilevel converters produce smaller CM voltage; therefore, the stress in the bearings of a
motor connected to a multilevel motor drive can be reduced.
 Lower voltage rating devices can be used.
Disadvantage:
 More number of power semiconductor switches are needed.
 Some configurations need more than one isolated DC supply.

25. RESULTS & CONCLUSION
Comparison:
Two Level Inverter Three Level Inverter Five LevelInverter
THD was around 72.86%. THD is around 35.41%. THD is around 27.91%
Applicable for low power
ratings.
For higher power ratings. Application in high power ratings.
Less number of switches
required.
Requirement of more number
of switches.
Requirement of circuit
components increases with
increase in levels of the inverter.
Efficiency is around % Efficiency is around 93.75% Efficiency is around 96.19%

26.  Earlier simulated Three-phase Three level Inverter results has been compared to
three phase five level inverter and it is found that the total harmonic distortion
has been reduced by 21.1%.
 The efficiency from three level to five level inverter has increased by 2.44%.
 As the number of level increases, THD decreases and active power increases.
 The output waveforms of the voltage and load current are also approximated
sine wave.
 Increasing the number of voltage levels in the inverter without requiring higher
rating on individual devices can increase power rating.
CONCLUSION & DISCUSSION:

27.  The THD can be further reduced by increasing the number of inverter levels.
 More efficient control Techniques such as Space Vector modulation can be implemented.
 Suitable filter design for further improvement of output voltage.
 Implementation of hardware circuits .
FUTURE SCOPE

28. REFERENCES
 A. K. Panda, Y. Suresh, “Research on Cascade Multilevel Inverter with Single DC Source by using
Three-phase Transformers”, Electrical Power and Energy System, Vol 40, March 2012, pp. 9-20.
 Rodriguez J, Lai S, and Peng FZ. Multilevel inverters: A survey of topologies, controls, and
applications. IEEE Trans. Ind. Electron; vol. 49, no. 4, pp. 724–738: Aug. 2002.
 Carrara et al G. A new multilevel PWM method: A theoretical Analysis. IEEE Trans Power Electronics;
Vol. 7, No. 3, pp. 497- 505: July 1992.
 Fang Lin Luo Hong Ye, Advanced DC/AC Inverters(Applications in renewable energy),2013:140-149.

29.  Tolbert L, Peng FZ, Habetler T. Multilevel converters for large electric drives. IEEE Trans.
Ind. Applicat; vol. 35, pp. 36–44: Jan.-Feb. 1999.
 Kouro S,Rebolledo J,Rodriguez J. Reduced Switching Frequency Modulation Algorithm for
High Power Multilevel Inverter. IEEE Trans on industrial Electronics; vol 54, no.5: Oct 2007
 Maynard TA, Foch H. Multilevel conversion: high voltage choppers and voltage source
inverters. In Proc. of IEEE Power Electron. Spec. Conf., 1992; Vol. 1, pp. 397-403.
 Fukuda S, Suzuki K. Harmonic evaluations of carrier based pwm methods using harmonics
distortion determining factor. IEEE Trans. Power Electr.; Vol. 24, No.2, pp. 1: Nov. 2009.

30. THANKYOU !