International Conference on Advances in Engineering and Technology (ICAET'2014) March 29-30, 2014 Singapore
A Hybrid Multi Level Three Phase Inverter
Dr. V Siva Krishna Rao Gadi, N.CH.V. Chakravarthi Bobbili, Seshagiri Boppana,
and Dr. Suresh Kumar Tummala
Abstract—One of the most significant recent advances in
power electronics is the multilevel inverter. Using this concept the
power conversion is performed with enhanced power quality. In
this scenario the Cascade H-Bridge Multi Level Inverter
(CHBMLI) is an exceptional one and it has many inherent benefits
like: its modular structure, it can be easily implemented through
the series connection of identical H-bridges, generates stepped
sinusoidal voltages at fundamental frequency with small
harmonics and finally no electromagnetic interference . This
flexibility has resulted CHBMLI topology in various applications
like medium-voltage industrial drives, electric vehicles and the
grid connection of photovoltaic-cell generation systems. But one
of the major limitations of the cascade multilevel converters is
requirement of isolated dc voltage sources for each H-bridge and
more number of switches, this increases the converter cost and
reduces the reliability of the system. This drawback is the key
motivation for the present work. This paper investigates multilevel
inverter topology with reduced DC sources and Switches. A
conventional switching strategy is implemented to get the
multilevel output without using any PWM techniques. Finally the
proposed model reduces the THD and size of multilevel converter
when compared with the cascade H-bridge multilevel inverter
(CHBMLI). The performance of proposed architecture, simulation
results are presented in this paper.
Keywords—CHBMLI, Multilevel Inverter, THD.
I. INTRODUCTION
M
ULTILEVEL converter gives massive advantages
compared with conventional and very well known
two level converters like; high power quality waveforms,
low switching losses, high voltage capability, low
electromagnetic compatibility etc. [1]–[3]. One of the most
significant multilevel topology is Cascade H-Bridge Multi
Level-Inverter (CHBMLI) [4], [5]. CHBMLI has numerous
advantages over Diode-Clamped (DCMC), FlyingCapacitor (FCMC) and P2 Multilevel Converters (P2MC)
[6], [7]. All these
converters are compared in terms of feasibility of their
utilizations and applications [8].
Multilevel inverters are an attractive alternative to
improve the output by synthesizing a staircase waveform
imitating a sinusoidal waveform. Such a waveform not only
has a low distortion, but it also reduces the dv/dt stress [9].
Multilevel inverter topologies have the advantages of
overcoming voltage limit capability of semiconductor
switches, high voltage capability and better harmonic
profile [10]–[12].
Moreover, multilevel inverters can operate at both
fundamental switching frequency and high switching
frequency. Thus, for high power/high voltage applications a
multilevel inverter can achieve better output waveform
using medium voltage power switches and hence preferred
over classical two-level inverters.
As aforesaid discussion indicates, multilevel inverters
have been attracting lot of attention in high power and high
voltage applications because they allow to keep the voltage
stresses of power switches within rated limits and thus adds
to the reliability of the converter.
However, another reliability issue is ‘simplicity’, as in
electronics design, a system with more number of parts is
more likely to fail, all the difficulties stated above can
minimized by reducing the number of switches ,in this
paper the proposed topology having 8 number switches for
single phase connection.
II. BASIC MULTI LEVEL H-BRIDGE INVERTER TOPOLOGY
The concept adapted for the proposed MLI topology is
that the inverter should be capable of synthesizing all
possible additive and subtractive combinations of the DC
levels of the input sources.
Dr. V Siva Krishna Rao Gadi is with the, Electrical Engineering
Department, College of Engineering, Andhra University, Visakapatnam,
INDIA. (e-mail: gvskrishna_rao@yahoo.com).
N. CH.V. Chakravarthi Bobbili is with the Electrical Engineering
Department, Vishnu Institute of Technology, Vishnupur, Bhimavaram,
WG (Dt), INDIA, (e-mail: chakravarthi204@gmail.com).
Seshagiri Boppana is with the Electrical Engineering Department, ,
Vishnu Institute of Technology, Vishnupur, Bhimavaram, WG (Dt),
INDIA.(e-mail:seshu.boppana@gmail.com).
Dr. Suresh Kumar Tummala with the Electrical Engineering
Department, , Vishnu Institute of Technology, Vishnupur, Bhimavaram,
WG (Dt), INDIA.(e-mail: sureshkumar255@ieee.org).
http://dx.doi.org/10.15242/IIE.E0314115
Fig. 1 Cascaded H-Bridge Inverter Configuration.
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International Conference on Advances in Engineering and Technology (ICAET'2014) March 29-30, 2014 Singapore
Topologically, multilevel inverters are largely divided
into three configurations:[13] diode-clamped multilevel
(DCML) inverters, flying-capacitor multilevel (FCML)
inverters, and cascaded H-bridge (CHML) multilevel
inverters. Among them, a cascaded H-bridge inverter with
separate
dc
sources
is
useful
for
practical
applications.(Fig.,1), because of reduced number switches
and DC link sources. Multiple numbers of H-Bridges are
connected in cascade [15] to get number of levels at the
output voltage. (Fig. 1)
The "level" in a cascaded-inverters defined by M=2N+1,
where M is the output phase voltage level, and N is the
number of H-Bridges [16].
For example to obtain 11 level output voltage we need to
connect 5 H-Bridges in cascade., so to attain the higher
levels the circuit becomes complex .
By changing the magnitude of the DC input sources in
the proposed topology can attain different levels at the
output.
To obtain number of levels at the output side the values
of DC sources has to consider as per Table 1.The proposed
topology can easy to develop as compared to the cascaded
H-bridge multilevel inverters and THD also reduced as
compared to the cascade inverters.
TABLE I
LIST OF DC INPUT VOLTAGES WITH LEVEL NUMBER
S.NO
Level Number
DC Input Voltages
1
7
E,E,E
2
9
E,2E,E
3
11
E,2E,2E
4
13
E,3E,2E
This Paper presents a conventional Three-phase 11 and
13-level inverter with less number of power elements and
hence less gate drive circuits in addition to less circuit
layout complexity. As the number of output levels increases
the harmonic content can be reduced. In this inverter
without using any PWM techniques the THD level will
reduce.
TABLE II
SWITCHING PATTERN FOR PROPOSED 11-LEVEL INVERTER
Switching Pattern
Level
Voltages
S1
S2
S3
S4
S5
S6
S7
S8
+5E
1
0
0
1
1
0
0
1
+4E
0
1
0
1
1
0
0
1
+3E
1
0
0
1
1
0
1
0
+2E
0
1
0
1
1
0
1
0
+E
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
-E
0
1
1
0
1
0
1
0
-2E
1
0
1
0
0
1
0
1
-3E
0
1
1
0
0
1
0
1
-4E
1
0
1
0
0
1
1
0
-5E
0
1
1
0
0
1
1
0
Fig. 2 Three-phase Cascaded H-Bridge Inverter for 11-Level
III. PROPOSED THREE PHASE TOPOLOGY
In this paper, the proposed topology has been
investigated for various objectives such as minimum
number of switches and DC voltage sources.
The switching pattern for 11-level inverter is tabulated
in the Table II indicates switch is in ON position, 0
indicates switch is in OFF position. From the above table
the gate pulses are evaluated for each switch.
TABLE III
SWITCHING PATTERN FOR PROPOSED 13-LEVEL INVERTER
Level
Switching Pattern
Voltages S1
S2
S3
S4
S5
S6
S7
S8
+6E
+5E
+4E
+3E
+2E
+E
0
-E
-2E
-3E
-4E
-5E
-6E
Fig. 3 Three-Phase 11-Level Inverter.
http://dx.doi.org/10.15242/IIE.E0314115
1
0
1
0
1
1
1
0
0
1
0
1
0
0
1
0
1
0
0
0
1
1
0
1
0
1
0
0
0
0
1
0
1
1
0
1
1
1
1
1
1
1
1
0
1
0
0
1
0
0
0
0
1
1
1
1
1
0
1
1
0
0
0
0
0
0
0
0
0
0
1
0
0
1
1
1
1
1
0
0
1
1
0
0
1
1
1
0
0
1
1
1
1
0
0
1
1
0
0
0
1
1
0
0
The switching pattern for 13-level inverter is tabulated in
the table3.
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International Conference on Advances in Engineering and Technology (ICAET'2014) March 29-30, 2014 Singapore
IV SIMULATION RESULTS
For both 11 and 13 level inverters, the circuit
configuration remains same, but they are differed by DC
bus voltages and gating signals. Proposed 11 and 13-level
inverters are shown in Fig. 3, which are realized through the
SIMULINK / MATLAB. The input DC bus voltages for 11level and 13-level inverters are tabulated in Table III.
Fig. 5 shows the gating pulses for left leg of inverter and
the complementary gating pulses are applied to right leg of
proposed 11-level inverter.
Fig. 8 Three-Phase LL Voltages of proposed 11 Level Inverter
Fig. 8 shows the three phase line to line output voltages
of proposed 11-level inverter and output voltage waveforms
with small first order filter.
Fig. 5 Gating Pulses for Switches in one Leg of the proposed
Inverter.
Fig. 9 FFT analysis of 11-Level Proposed inverter
Fig. 6 Three- Phase Line to Line Voltages of 11-Level
Conventional H-Bridge Inverter
Fig. 9 Shows the FFT analysis of three proposed 11-level
inverter output voltage. The fundamental component of
inverter is 761.2V for an input DC bus voltage of 500V.
The total Harmonic Distortion (THD) value is reduced to
7.43% without using any pulse width modulation (PWM)
techniques.
Fig. 7 FFT analysis of 11-level conventional H-Bridge
Fig. 10 Three-Phase LL voltages of proposed 13 Level Inverter
Fig. 7 indicates the Harmonic spectra of Conventional HBridge Inverter. The Total harmonic Distortion (THD)
value is about 9.35%.
http://dx.doi.org/10.15242/IIE.E0314115
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International Conference on Advances in Engineering and Technology (ICAET'2014) March 29-30, 2014 Singapore
2008;2(2):28–39.
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[7] Sirisukprasert S, Xu Z, Zhang B, Lai JS, Huang AQ. A high-frequency
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http://dx.doi.org/10.1109/TIE.2009.2029579
Fig. 10 shows the three phase line to line output voltages of
proposed 13-level inverter and output voltage waveforms with
small first order filter
Fig. 11 FFT analysis of 13-level proposed inverter
Fig. 11 shows the FFT analysis of three proposed 13-level
inverter output voltage. The fundamental component of
inverter is 903.8V for an input DC bus voltage of 600V. The
Total Harmonic Distortion (THD) value is reduced to 6.83%
without using any Pulse Width Modulation (PWM)
techniques.
V. CONCLUSIONS
Technical aspects and Performance of proposed Multilevel
Inverters with reduced DC sources are presented. Proposed
three phase 11 & 13-level inverters are able to produce line
voltages at higher fundamental and lower THD as compared to
the CHBMLI. The effectiveness and validity of the proposed
approach are also demonstrated with results. Since less
number of components are utilized, the proposed structure is
reliable, efficient, cost-effective and compact. The attractive
features of the proposed converters are: low switching
frequency and reduce electromagnetic interference problems,
increase utilization rate because of less number of DC sources,
Consequently, this characteristic allows one to achieve high
quality output voltages and input currents. Also, it has
outstanding availability due to their intrinsic component
redundancy. Due to these features, proposed architecture is
superior over the conventional structures. Results presented in
this paper are line voltage, because the line voltage is able to
synthesize more levels compared to the phase voltage, thus
resembling a more desirable sinusoidal waveform. Besides
that, the line voltage yields better spectral performance, hence
reducing the need of an output filter.
Prof. G. V. Siva Krishna Rao received his
Bachelor Degree in Electrical and Electronics
Engineering from Sri Venkateswara university
Thirupathi Andhra Pradesh, India. He
completed his Master of Technology in Power
Systems from Sri Venkateswara university
Thirupathi Andhra Pradesh, India. He was
awarded with Doctorate (Ph.D.) degree in
Electrical Engineering from the Andhra
University in 2007.Presently Working as
Professor Depatment Of Electrical Engineering
college of Engineering Andhra University Vishakapatnam. Two research
scholars are guided and four are under process..He has published several
papers in his areas of interest. He is also a member of different professional
societies like IEEE, IGNOU, UGC Nominee and AICTE.
REFERENCES
[1] Rodriguez J, Lai JS, Peng FZ. Multilevel inverters: survey of topologies,
controls, and applications. IEEE Trans Ind Appl 2002;49(4):724–38.
[2] Franquelo LG, Rodriguez J, Leon JI, Kouro S, Portillo R, Prats MAM.
The age of multilevel converters arrives. IEEE Ind Electron Mag
http://dx.doi.org/10.15242/IIE.E0314115
539
International Conference on Advances in Engineering and Technology (ICAET'2014) March 29-30, 2014 Singapore
B.N.CH.V. Chakravarthi received his Bachelor
degree in Electrical and Electronics Engineering
from Akula Gopayya Engineering College,
Tadepalligudem, Andhra Pradesh, India in the
year 2006. He completed his Master of
Technology in Power Electronics at Nova
Engineering College, Jangareddigudem, Andhra
Pradesh, India in the year 2011. His area of
interests includes Power Industrial drives and
FACTS Controllers. He published two papers on
Multilevel Inverters. He is a member of ISTE, IAENG. He is currently
working as Assistant Professor in Electrical and Electronics Engineering
Department at Vishnu institute of Technology Bhimavaram, Andhra Pradesh,
India.
B. Seshagiri received his Bachelor Degree in
Electrical and Electronics Engineering from
Gudlavalleru Engineering College, Andhra
Pradesh, India in the year 2008. He completed
his Master of Technology in Power Electronics
stream
from
Swarnandhra
College of
Engineering and Technology, Narasapuram,
Andhra Pradesh, India in the year 2012. His area
of interests includes Power Industrial drives and
FACTS Controllers. He published two papers on
reduction of harmonics in Voltage source
Inverters. He is currently working as Assistant Professor in Electrical and
Electronics Engineering Department at Vishnu institute of Technology
Bhimavaram, Andhra Pradesh, India.
Dr. Suresh Kumar Tummala (M’08) was born
in Visakhapatnam. He received his Bachelor’s and
Maters degree in Electrical & Electronics
Engineering from Jawaharlal Nehru Technological
University, Hyd. in 2005 and 2007 respectively.
He was awarded with Doctorate (Ph.D.) degree in
Electrical Engineering from the JNTUA,
Ananthapur in 2013. Presently working as
Associate Professor & Head of EEE Department
with
Vishnu
Institute
of
Technology,
Bhimavaram, Andhra Pradesh, India. His areas of
interests include Power System Reliability, Renewable Energy, Power
Electronics, Drives and Electrical Machines. He has published several papers
in his areas of interest. He is also a member of different professional societies
like IEEE, IAENG, ISTE, ISEEE, ISES, and EDAS.
http://dx.doi.org/10.15242/IIE.E0314115
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