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1. POWER QUALITY IMPROVEMENT USING MULTILEVEL INVETERS
DEPT. OF ELECTRICAL AND ELECTRONICS Page1
ABSTRACT
Multilevel inverter are widely used in field of Industrial application. Harmonics contents in
different electronics application can be reduced. In case of multilevel inverters they are
extremely capable of achieving high power quality output voltage waveform and higher
frequency rating with help of structure of inverter. Here we are comparing the Total Harmonic
Distortion of two levels. By applying this concept, harmonics can be eliminated, and in the
output voltage, the Total Harmonic Distortion (THD) can be improved. A procedure to achieve
the appropriate level shifting is presented.
Keywords— cascaded H-bridge, diode clamped, flying capacitor multilevel inverter (FCMLI),
Multilevel inverter (MLI) topology

2. POWER QUALITY IMPROVEMENT USING MULTILEVEL INVETERS
DEPT. OF ELECTRICAL AND ELECTRONICS Page2
CONTENTS
SL.NO TITLE PAGE NO
01 INTRODUCTION 03
02 BLOCK DIAGRAM FOR GENERAL MULTILEVEL
INVERTER
04
03 MODULATION TECHNIQUES 05
04 ADVANTAGES, APPLICATIONS, EXPECTED OUTPUT 06
05 LITERATURE REVIEW 07

3. POWER QUALITY IMPROVEMENT USING MULTILEVEL INVETERS
DEPT. OF ELECTRICAL AND ELECTRONICS Page3
INTRODUCTION:
A power inverter, or inverter, is an electronic device or circuitry that changes direct current (DC)
to alternating current (AC).The input voltage, output voltage and frequency, and
overall power handling depend on the design of the specific device or circuitry. The inverter does
not produce any power; the power is provided by the DC source.
MULTILEVEL INVERTER :
• It is advanced power electronic inverter circuit, which is most commonly used for
producing higher output voltage levels for the drive system applications.
• MLI’s were invented mainly to overcome the limitations of voltage ratings of the power
devices so they can generate nearly sinusoidal voltage waveform.
• Block diagram of MLI Topology has given below:

4. POWER QUALITY IMPROVEMENT USING MULTILEVEL INVETERS
DEPT. OF ELECTRICAL AND ELECTRONICS Page4
BLOCK DIAGRAM FOR GENERALMULTILEVEL INVERTER

5. POWER QUALITY IMPROVEMENT USING MULTILEVEL INVETERS
DEPT. OF ELECTRICAL AND ELECTRONICS Page5
MODULATION TECHNIQUES
The main aims to be achieved by the modulation techniques are,
 Reduced total harmonic distortion (THD) in the output.
 Lower switching losses.
 Less computation time.
 Easy implementation.
 High power quality.
 Operates at both fundamental and high switching frequency PWM.

6. POWER QUALITY IMPROVEMENT USING MULTILEVEL INVETERS
DEPT. OF ELECTRICAL AND ELECTRONICS Page6
ADVANTAGES:
• MLI’S results in highly efficient power conversion.
• Added advantages are high efficiency, low electromagnetic interference and also scaled
and modular system.
• MLI’s offers enhanced output waveform with minimum THD.
• Better waveform quality of output voltage (more sinusoidal).
• Reduced dV/dt, leading to reduction in EMI.
• Lower voltage rating devices can be used
• lower voltage stress on power switches
APPLICATIONS:
• MLI is used as an adjustable speed drive.
• Used in Electric vehicles, UPS, Harmonic current. compensation, AC motor drives, so
on.
• The MLI is used in the area of Distributed Power Generation.
• Multilevel inverter are used in hybrid electric vehicles.
EXPECTED OUTPUT
We are expecting a sinusoidal waveform with reduced Total Harmonic Distortion level
between 15 – 25%, according to IEEE standards.

7. POWER QUALITY IMPROVEMENT USING MULTILEVEL INVETERS
DEPT. OF ELECTRICAL AND ELECTRONICS Page7
LITERATURE REVIEW:
 AUTHOR: Monoj A.Waghmare, Prachi A.Salodkar,
TITLE: Modulation techniques
• This paper presents MLI topology with less number of switches for generation of high
level AC out voltage.
• A multilevel single carrier modulation technique is proposed in this paper.
• Modes of operation is explained and concept is validated with experimental results.
PUBLISH: IEEE 978-1-5090-4679-9/17/$31.00 ©2017
•
 AUTHOR: Amol K. Koshti, M. N.Rao
TITLE: A Brief review on multilevel inverter topologies
• This paper discusses the brief review of different strategies used for MLI’S
PUBLISH: IEEE 978-1-5090-4083-4/17/$31.00 ©2017
 AUTHOR: Shailendra Jain, senior member
TITLE: Introduction to H-bridge inverter .
• A new hexagon(H-type) sub-block for multilevel inverter (MLI) is introduced suitable
for both symmetrical and asymmetrical configurations.
• The proposed MLI consist cascade hexagon type sub-blocks to generate more levels in
output. The working of topology is presented in detail along with generate modulation
analysis.
PUBLISH: : IEEE 978-1-5090-4530-3/16/$31.00 ©2016
 AUTHOR: M. Trabelsi et. al.
TITLE: An improved SVPWM method for Multilevel inverters
• This paper proposes a new general SpaceVector PWM (SVPWM) method for Multi-
Level Inverters(MLI) based on a generalization of dwell-times calculation.
• A very simple mapping is used to achieve the SVPWM for any n-level inverter.
PUBLISH: IEEE 978-1-5090-4530-3/16/$31.00 ©20176