Comparative Analysis between Five Level Conventional and Modified Cascaded H-Bridge Five Level Inverter Using Multicarrier Pulse width Modulation Techniques

International Journal of Modern Research in Engineering and Technology (IJMRET)
www.ijmret.org Volume 3 Issue 12 ǁ December 2018.
w w w . i j m r e t . o r g I S S N : 2 4 5 6 - 5 6 2 8 Page 25
Comparative Analysis between Five Level
Conventional and Modified Cascaded H-Bridge
Five Level Inverter Using Multicarrier Pulse
width Modulation Techniques.
Sayed Hadi Hussain1
, Jahangeer Soomro2
,Afshan Shah3
, Asif Ali Shah4
.
Department of Electrical Engineering, MUET University, IICT. Pakistan
Department of Electrical Engineering, SukkurIBA University, Sindh, Pakistan
Abstract: Multilevel Inverters are getting popular and have become more attractive to researchers in the
recent times for high power applications due to their better power quality and higher efficiency as compared to
two level inverters. This research work presents a detailed comparative analysis of various multicarrier
sinusoidal PWM schemes such as In Phase Disposition, Phase Opposition Disposition and Alternate Phase
Opposite Disposition implemented on five level conventional and modified cascaded h-bridge inverters in
MATLAB/SIMULINK software. Conventional five level topology uses eight switches and suffers from increased
switching complexity while modified five level topology uses only five switches and is recommended to reduce
switching complexity and switching losses. It also ensures less number of components, reduced size and overall
cost of the system. The effect of modulation index (Ma) on the output harmonic contents in various PWM
techniques is also analyzed.
Keywords:Pulse Width Modulation, Total Harmonic Distortion, Cascaded H-Bridge Multilevel Inverter, Modified
Multilevel Inverter, Level Shifted Modulation, Phase Shifted Modulation.
I. INTRODUCTION
Inverter is basically a power converter that
converts dc power to desired ac power. Square and
Quasi square wave (two level inverters) suffer from
high value of total harmonic distortion (Nayak et al.,
2014), also they include dominating lower order
harmonics which are difficult to filter and hence
filtering losses are increased, therefore they are
restricted for high power application (E. Baser et al.,
2010). Multilevel inverters are also called low
distorted sine wave inverters. They start from level
three and they are used to run sensitive devices such
as medical equipment (oxygen concentrator),
photocopier machines, laser printers, certain laptop
computers and industrial motors due to their better
power quality and low total harmonic distortions
(Y.M Park et al., 2010). Due to this fact, researchers
are highly attracted to multilevel inverters for high
power applications including adjustable speed drives
(ASD), flexible alternating current transmission
system (FACTS), Renewable energy systems,
uninterrupted power supply (UPS) and high voltage
direct current transmission (HVDC) (S. Kouro et al.,
2010).
The multilevel inverters (MLI) are classified into
Diode Clamped inverter, Flying Capacitor inverter
and Cascaded H Bridge inverter (Kumar et al., 2013).
Cascaded H Bridge multilevel inverter topology is
better than other two topologies as it does not require
any flying capacitor or clamping diode, thus least
number of
components is used (R. A. Ahmed et al., 2010). Also,
voltage sharing is automatic because of
separate dc sources (P. Tamilvani. et al., 2016)
Hence, cascaded h-bridge five level topology is
investigated in this research paper.
a. Multi Carrier Sinusoidal Pulse Width Modulation
Techniques
Pulse Width Modulation (PWM) techniques are used
to control the output voltage of inverter and such
inverters are known as PWM inverters (P. Tamilvani.
et al., 2016). One of the most commonly used PWM
technique is multicarrier sinusoidal PWM technique.
It is classified into phase shifted modulation and level
shifted modulation. Phase shifted modulation has

higher values of %THD as compared to level shifted
modulation (G. Varghese et al., 2015). Therefore,
level shifted modulation is considered and discussed
in this research work. It should be noted that for n-
level multilevel inverter using level shifted
modulation scheme requires (n-1) carrier waves, all
having same amplitude and frequency (B. Harish et
al., 2014). Thus for five level, four triangular signals
will be required. Level shifted modulation is further
classified into:
1.1 In Phase Disposition (IPD)
All the carrier signals are in phase with each other as
shown in Fig. 1.
Fig. 1 In Phase Disposition PWM
1.2 Phase Opposition Disposition (POD)
All the carrier signals above the sinusoidal reference
zero point are 180° out of phase with those below
reference point as shown in Fig. 2.
Fig. 2 Phase Opposition Disposition PWM
1.3 Alternate Phase Opposition Disposition (APOD)
All the carriers are 180° out of phase from its
adjacent carrier signal as shown in Fig. 3.
Fig. 3 Alternate Phase Opposition Disposition PWM
II. Materials and methodology:
This research will be performed using most
well-known Engineering software MATlab.
In which we will use simulation tool to get all results
of different types of inverters.
III. Results:
3.1 Simulation Results of Conventional Cascaded
H Bridge Multi-level Inverter using Level
Shifted SPWM
It should be noted that for n- level inverter topology,
n-1/2 h bridges are required B. Harish et al., 2014);
(D. Subramanian et al., 2013). Thus, for 5- level, 2 h
bridges (8 switches) will be required as shown in Fig.
4. The h bridges are cascaded such that its output
voltage will be addition of separate dc sources
applied. There can be 5 possible levels at output
including 2V, V, 0, -V, -2V. Due to separate dc
sources required, this topology is suitable for utilizing
energy from solar panels and fuel cells.
Fig. 4 MATLAB/SIMULINK Model of Conventional Cascaded
H-Bridge Inverter
Level shifted SPWM (IPD, POD and APOD) are
applied to control this topology having resistive load
(20 Ω) and its simulations results are compared and
analyzed below.
3.2 Five Level IPD PWM Technique
It should be noted that fundamental frequency of 50
Hz, Switching Frequency of 1 KHz and Modulation
Index of 1 is taken. Fig. 5 shows the output voltage of
topology using IPD and Fig. 6 represents total
harmonic distortion of output voltage.
Fig. 5 Output voltage of five level IPD

Fig. 6 Output voltage FFT analysis with m=1 and
Fswitching=1000Hz
3.3 Five Level POD PWM Technique:
All the parameters are taken same as were taken for
IPD PWM technique. Fig. 7 shows the output voltage
of topology using POD and Fig. 8 represents total
harmonic distortion of output voltage.
Fig. 7 Output voltage of five level POD
Fswitching=1000Hz
3.4 Five Level APOD PWM Technique:
All the parameters are taken same as were taken for
IPD PWM and POD techniques. Fig. 9 shows the
output voltage of topology using APOD and Fig. 10
represents total harmonic distortion of output voltage.
Fig. 9 Output voltage of five level APOD
Fswitching=1000Hz
3.5 Comparative analysis among IPD, POD and APOD PWM
at different Modulation Index
It is concluded from Table 1. That %THD is almost
same for all level shifted PWM techniques but it is
slightly lower in POD as compared to IPD and
APOD. Also, it is concluded from the obtained results
that increasing the modulation index decreases the
total harmonic distortion.
Table 1: Comparative analysis between Level Shifted SPWM
for five levels
Ma IPD THD
(%)
POD THD
(%)
APOD
THD (%)
1 27.47% 26.91% 28.44%
0.9 34.01% 33.78% 33.91%
0.8 39.00% 38.55% 38.73%
0.7 42.51% 42.24% 43.08%
0.6 44.81% 44.15% 45.51%
3.6 Simulation Results of Modified Cascaded H-
Bridge Inverter using Level Shifted SPWM:
As discussed earlier that for n level conventional
cascaded h bridge inverter, n-1/2 h bridges are
required. Thus usage of more switches increases
switching complexity as well as switching losses, also
overall cost and size of the topology increases due to
more number of switches. Due to this fact,
researchers are attracted towards modified multilevel
cascaded h bridge inverter to reduce the switching
complexity, size and overall cost of the topology (D.
Subramanian et al., 2013). The purpose of this
discussion is to propose modified multilevel inverter
topology where six numbers of switches are used as
shown in Fig. 11 whereas in conventional cascaded h
bridge eight numbers of switches are used.

Fig. 11 MATLAB/SIMULINK Model of Modified Cascaded H-
Bridge Inverter
Fig. 12 shows proposed IPD PWM technique for
modified five levels topology, similarly POD and
APOD PWM techniques can be designed with slight
changes in values of triangular wave.
Fig. 12 Proposed IPD PWM Technique for Modified 5 level
Topology
Level shifted SPWM (IPD, POD and APOD) are
applied to control this topology, all the parameters are
kept same as for conventional cascaded h bridge
inverter due to comparison purpose.
3.7 Five Level IPD PWM Technique
Fig. 13 shows output voltage of five levels IPD PWM
technique implemented on modified five levels
topology and Fig. 14 shows output voltage total
harmonics distortions.
Fig. 13 Output voltage of five level IPD
Fswitching=1000Hz
3.8 Five Level POD PWM Technique
Fig. 15 shows output voltage of five levels POD
PWM technique implemented on modified five levels
Fig. 15 Output voltage of five level POD
Fswitching=1000Hz
3.9 Five Level APOD PWM Technique
Fig. 17 shows output voltage of five levels APOD
PWM technique implemented on modified five levels
Fig. 17 Output voltage of five level APOD

Fswitching=1000Hz
3.10Comparative Analysis between Conventional
and Modified Five Level Inverter
It is concluded from the following table that modified
multilevel inverter uses less number of switches, thus
it has less switching complexity, low cost and
reduced size of the system. Also, %THD of
conventional and modified topologies is very close
and there is veryslight difference. Therefore,
modified multilevel inverter is considered to be better
choice than conventional multilevel inverters.
Table 2: Comparative analysis between Conventional and
Modified Cascaded MLI
Topology Ffundamental Fswitching Ma No: of
Switches
%THD
IPD POD APOD
Convention
al MLI
50 10 1 8
27.47 26.91 28.44
Modified
MLI
50 10 1 5
27.62 27.07 28.53
IV. Conclusions
It is observed that POD PWM technique has
slightly less %THD than IPD and APOD in
conventional as well modified MLI. Also, it is
concluded that increasing Modulation Index (Ma)
reduces %THD. Conventional and Modified MLI has
almost same total harmonic distortions but Modified
MLI uses only 5 switches whereas Conventional MLI
uses 8 switches, hence switching complexity,
switching losses and cost of the system is reduced
and Modified MLI is recommended to be better
choice.
V. Recommendations
 Hardware Implementation
Digital PWM techniques can be implemented
by using DSPs, Microcontrollers,
Microprocessors, ASICs and FPGAs. These
controllers can be compared and appropriate
controller can be suggested for various
applications.
 Implementation using Phil lab
The hardware results using software laboratory
which will save our cost and give validf results
 Space Vector PWM
In future days, we will use space vector
technique and we can compare its output with
the sinusoidal PWM technique.
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Comparative Analysis between Five Level Conventional and Modified Cascaded H-Bridge Five Level Inverter Using Multicarrier Pulse width Modulation Techniques

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Comparative Analysis between Five Level Conventional and Modified Cascaded H-Bridge Five Level Inverter Using Multicarrier Pulse width Modulation Techniques