Analysis and simulation of even-level quasi-Z-source inverter

International Journal of Electrical and Computer Engineering (IJECE)
Vol. 12, No. 4, August 2022, pp. 3477~3484
ISSN: 2088-8708, DOI: 10.11591/ijece.v12i4.pp3477-3484  3477
Journal homepage: http://ijece.iaescore.com
Analysis and simulation of even-level quasi-Z-source inverter
Niltala Sai Shanmukha Akshath1
, Avugaddi Naresh1
, Matcha Nikesh kumar1
, Mayur Barman1
,
Durgesh Nandan2
, Tripuathi Abhilash3
1
Department of Electrical and Electronics Engineering, Aditya Engineering College, Surampalem, India
2
Department of Electronics and Telecommunication, Symbiosis Institute of Technology, Symbiosis International (Deemed University),
Pune, India
3
Accendere Knowledge Management Services Pvt. Ltd., CL Educate Ltd., New Delhi, India
Article Info ABSTRACT
Article history:
Received Feb 19, 2021
Revised Mar 16, 2022
Accepted Mar 29, 2022
This research proposes a seven-level inverter with quasi-Z-source boost
converters. The proposed topology employs a packed U-cell asymmetrical
type multilevel inverter along with front-end quasi-Z-source networks. The
quasi networks provide high gain compared to a conventional boost
converter. This topology is the most suitable for photovoltaic multi-string
applications. The proposed topology has the potential to supply both the
alternating current (AC) and direct current (DC) type load. The inverter
structure has a lower number of active switches which helps in the reduction
of losses and improvement in efficiency. In this paper, the operation
principle of a quasi-network and inverter circuit are explained in detail. In
addition, the simulation results for various modulation indices are presented.
In the MATLAB/Simulink environment, the architecture is proposed by
using gated sinusoidal “Pulse width modulation”.
Keywords:
Duty cycle
Harmonic spectra
Multilevel inverter
Quasi Z-source
Seven-level
This is an open access article under the CC BY-SA license.
Corresponding Author:
Tirupathi Abhilash
Accendere Knowledge Management Services Pvt. Ltd., CL Educate Ltd.
New Delhi, India
Email: abhilash.tripuathi@accendere.co.in
1. INTRODUCTION
Latest developments have seen considerable rise in the utilization of Z-sources based converters in
possible solutions such as environmentally ecofriendly fuel cell-based generations/photovoltaic (PV) to fulfil
expanding energy demands, flexible alternating current (AC) transmission systems (FACTs), energy storage,
electric and electric vehicles as well as in wind energy conversions [1]. In comparison by the direct current
(DC-DC) two-stage conversions, the effectiveness of single-stage conversion improves as a result of this. The
Z-source inverters (ZSI) alleviate the failure of outdated current source inverters and voltage supply by using
a network of two inductors and two condensers in the shape of a Z [2]. This impedance network introduction
eliminates inverters failure due to the lack of dead band in the absence of the leg switches and thus reduces
the waveform distance. By changing the duty cycle D0, the output voltage is controlled phase switches or all
phases to be activated over the cycle duration.
A review of various strategies is presented [3]. To achieve the appropriate output tension, traditional
pulse-width modulation (PWM) methods are modified to include a zero-status shoot-through without
changing the active circumstances. The optimal positioning of the screw is, however, obligatory as it takes a
prominent place in the evaluation of the current ripple, number of switch switches, minimization of switching
loss and softness. In this aspect, a new control system [4] is investigated, which uses zero voltage switching
(ZVS) to effectively reduce commutations for simple control and enhanced efficiency. A better control
system is being investigated in the same area [5]. Both legs are used to shoot, reducing the current stress

 ISSN: 2088-8708
Int J Elec & Comp Eng, Vol. 12, No. 4, August 2022: 3477-3484
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between the switches. The higher as well as lower frequencies of the switch’s fs and 2fs are different, which
increases the loss. The technique is modified in this paper to allow all switches to operate at the same
frequency (s) to reduce the loss of switching. In comparison to ZSIs, the benefits of constant input current,
reduced capacitor voltage stress, and smaller C2 make quasi Zsource inverters (qZSI) highly attractive for
renewable applications. Multi-level inverters (MLIs) for low-power applications have recently gained the
benefits of low dv/dt, minimal button stress, improved voltage and current profiles, and reduced filter
size [6]. H-bridges in cascade (CHB), neutrally point clamped (NPC), and flying condensers are three
prominent topologies utilized in industrial applications (FCs). CHB is the most suitable of these due to its
adaptability, lack of clamping diodes, and lack of FC-voltage balance issues. Switch counts, condenser
reduction, diodes, condenser equilibrium, simplicity of control, and the quantity of DC sources have all been
studied in MLIs [7]. Although MLIs provide a number of advantages, one of the most significant drawbacks
is the low output voltage gain. In order to achieve improved voltage control and output quality, MLIs must be
properly upgraded with appropriate power conditioners [8]–[14]. The power conditioner for MLI integration
is a Z source-based converter.
The recent growth in the adoption of Z-Source converters has revolutionized renewable energy
system including power electronic application, hybrid cars, uninterruptable power supplies, and distributed
energy [15]. Inverter capitalizes on the problems that traditional current source and voltage source inverters
[16]. This reduces wave form distortions and improves dependability. It reduces DC power consumption
when combined with a buck-boost circuit, resulting in a more efficient single-stage. In order to maximize the
amplitude of the shoot-through voltage, the service series is boosted by the output voltage. The beam-through
can be obtained by turning on the switches for DT. The different methods for shoot-through control are
described in the literature [17], [18]. In general, the Z-source converters are more common with conversions
from DC to alternating current (AC) as well as AC to DC. Because of the numerous Z-sources topologies
[19]–[22], most systems use quasi-Z inverters, which minimize the capacitor size, thus offering continuous
input current, as well as having DC input, but are not common-rail devices.
In contrast, a multi-level inverter (MLI) delivers better voltage and current with lower total
harmonics distortion (THD), which reduces switching losses and increases efficiency. A number of more
advanced MLI topologies, including neutral point (NP) capacitor, switch count (SC) capacitor, and the
cascaded chronic myeloid leukemia blast crisis (CML BC), have been employed in order to resolve the issues
of switching, capacitor voltage balancing, and the difficulty of managing complexity [23]. For another
important effort, MLI is also being made to comply with lower voltage distributed energy sources, which
means the biggest issue with MLI is low output voltage gain, however [24], [25].
Higher voltage gains and seven-level AC output with fewer switching devices, fewer DC power
supply, as well as minimum off state voltages pressure acrossed the converting device are all advantages of
the proposed converter. The rest of the manuscript is laid out: under second subpart of paper explain
proposed approach of inverter and operating modes, under third subpart of paper explains the modulation
principle used to generate the required output voltage waveform, under fourth subpart of paper shows how
the new converter design which proposed by author is validated using simulation results for various
modulation indices, and section 5 finally concludes all pros and corn of this research.
2. PROPOSED INVERTER
Figure 1 represents the developed quasi of Z-source single phase seven levels created MLI using a
packed u-cell structure. The z-source network is formed by the elements called inductors, diodes capacitors
and an active switch. The inverter circuit consists of 6 active switching devices with bi-directional
conducting capability. Impact of anti-parallel diodes, the switching device has bi-directional leading
capability but only block voltages in uni-directional. In the suggested topology, three different DC source can
be generated after batteries bank, PV system, or rectifiers circuits. The major contribution of this paper is the
cascaded connection of packed U-cell (PUC) inverter to the quasi-Z-source. This cascaded connection gives
the higher output voltage, better performance and improved harmonic profile which is shown with the
simulation results.
Figures 2(a) and 2(b) represent the switching conditions through negative along with positive zeroes
crossings of the output voltage. V0=0+
is the positive zero-crossing through the output voltage. V0=0-
is the
negative zero-crossing at output voltage. To keep the temperature escalation in entire switches at the same
level, both switching states are used equally.
Figure 3 shows the recommended converter, which operates to create a positive level voltage
transversely the output terminal. Figure 3(a) generated V0=V1, and the power semiconductor devices
insulated gate bipolar transistors (IGBTs) S5, S7, and S10 operate in this manner. As illustrated in, the

Int J Elec & Comp Eng ISSN: 2088-8708 
Analysis and simulation of even-level quasi-Z-source inverter (Niltala Sai shanmukha Akshath)
3479
IGBTs S6, S7, and S9 operate in this manner Figure 3(b). The peak voltage of V0=V1+V2 is shown in
Figure 3(c), and the IGBTs S5, S7, and S9 conducted in these operating modes.
Figure 1. Proposed Z-source inverter the schematic circuit diagram
(a) (b)
Figure 2. Zero switching states: (a) V0=0+
and (b) V0=0-
Figure 4 depicts the converter’s employed mode for producing negative output voltage levels.
V0=-V1 is generated in Figure 4(a), and the IGBTs S6, S8, and S9 turn on in this operating mode. The output
voltage V0=-V2 is shown in Figure 4(b), and the IGBTs S5, S8, and S10 turn on during this time. The output
voltage VL=-(V1+V2) is shown in Figure 4(c), and the IGBTs S6, S8, and S10 are turned on at this time.

 ISSN: 2088-8708
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(a) (b) (c)
Figure 3. Positive switching states (a) V0=V1, (b) V0=V2, and (c) V0=V1+V2
(a) (b) (c)
Figure 4. Negative switching states (a) VL=-Vdc/2, (b) VL=-3 Vdc/2, and (c) VL=-2 Vdc
3. METHOD
3.1. Modulation technique
Table 1 shows the off and on conditions of the switching devices in the planned convertors on
various output voltage value to help understand the switching states. The numerals 1 and 0 in Table 1
represent the off and on state of the IGBT in the Figure 1 based results. Lower switching frequencies appear
to be used by switches S7 and S8, resulting in lower switching losses. In the designed architecture, the
modulation technique working for generation of gate pulse to the IGBT is depicted in Figure 5. A sine wave
is placed over six trilateral waveforms. The carrier waveform is known by way of the triangle waves,
whereas the reference waveform is known as the sinusoidal waves shown configuration constraints in
Table 2. Respectively carrier waveform interrelates with the reference waveform at certain intermissions, as
specified by the digits 1, 2, 3, 1', 2', and 3'. As a result of these connections among the carrier waves and
reference, the Produced pulsations are N1-N3 and P1-P3. These pulsations are successfully used in logical
gate circuit uses to produce the mandatory output voltages of seven-level. The modulation index (M.I.)
regulates the amount of output stages that is explained using (1).
M.I.=
𝑉0𝑝𝑒𝑎𝑘
3×𝑉𝑑𝑐
(1)

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Table 1. Switching sequences of inverter
Output Voltage Level (V0) S1 S2 S3 S4 S5 S6 S7 S8 S9 S10
V1+V2 0 0 0 0 1 0 1 0 1 0
V2 0 0 0 0 0 1 1 0 1 0
V1 0 0 0 0 1 0 1 0 0 1
0+
0 0 0 0 1 0 0 1 1 0
0-
0 0 0 0 0 1 1 0 0 1
-V1 0 0 0 0 0 1 0 1 1 0
-V2 0 0 0 0 1 0 0 1 0 1
-(V1+V2) 0 0 0 0 0 1 0 1 0 1
Figure 5. Sin-triangle evaluation of PWM system
Table 2. Configuration constraints
Parameters Values
“Vdc (V)” 240 V
“Poutput (W)” 730
“V0 (V)” 230
“I0 (A)” 3.5
“Switching frequency (fsw)” 4 kHz
“Fundamental frequency (fm)” 50 Hz
4. RESULTS AND DISCUSSION
To demonstrate its performance, the proposed configuration is evaluated in a MATLAB simulation.
The simulation settings are adjusted to 230 V and 50 Hz for a single-phase output voltage. Figure 6(a) shows
that currents waveforms and the inverter output voltage intended for an M.I. of 0.6 and 0.9 respectively.
Figure 6(a) depicts a corresponding current and the 9-level output voltage waveforms. Figure 6(b) depicts a
seven-level output voltage waveforms and the comparable load currents. Lowering M.I. lowers the output
voltage’s peak value, which is self-evident (V0 peak). For various values of M.I., the fast Fourier transform
spectrum of the inverter’s output voltages is revealed in Figure 7(a) as well as Figure 7(b). V0 peak is seen to
be 361 V, at the condition of the inverter is modulation value is 0.9 and the THD is 16.6%. As demonstrated
in, a M.I. is invertional proportional of THD as a result of a decreasing in the amount of output voltage level.
Figures 8(a) and 8(b) represented the harmonic spectrum of the output current waveform. The rate of
I0 peak is 6.4 A at an inflection of 0.9, and the THD is about 0.5%. The I0 peak value reduces in the same
way as the voltage decreases when the MI decreases. The THD is coarsely 0.6%, besides the I0 peak value is
5 A.

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3482
(a) (b)
Figure 6. MATLAB based results at (a) MI=0.9 and (b) MI=0.6
(a) (b)
Figure 7. Fast Fourier transform analysis of (a) V0 for (MI=0.9) and (b) V0 for (MI=0.6)
(a) (b)
Figure 8. Fast Fourier transform analysis of (a) I0 for (MI=0.9) and (b) I0 for (MI=0.6)
5. CONCLUSION
Presented research work gives a comprehensive investigation of the seven-level operational methods
of the proposed quasi-Z-sources constructed multi-level inverter (MLI) with a concentrated constituent
amount. The proposed network topology is a two-stage circuit that provides independent control of the output
variables. The modulation technique for generating inverter switch firing pulses has been refined. The
simulation results are shown for a variety of M.I. values and power ratings. The output parameters were
subjected to a fast fourier transform (FFT) analysis, and the percent THD of the current waveforms was
found to be within the IEEE 1547 grid standard’s restrictions.
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BIOGRAPHIES OF AUTHORS
Niltala Sai shanmukha Akshath is U. G. student of the B. Tech. program in
electrical and electronic engineering branch from Aditya Engineering College, Surrampalem,
East Godavari District, Andhra Pradesh, India. His research interests include renewable
energy, and power electronics. He can be contacted at email: 18a91a0233@aec.edu.in.

 ISSN: 2088-8708
3484
Avugaddi Naresh is U. G. student of the B. Tech. program in electrical and
electronic engineering branch from Aditya Engineering College, Surrampalem, East Godavari
District, Andhra Pradesh, India. His research interests include renewable energy, and power
electronics. He can be contacted at email: 18a91a0202@aec.edu.in.
Matcha Nikesh kumar is U. G. student of the B. Tech. program in electrical and
electronic engineering branch from Aditya Engineering College, Surrampalem, East Godavari
District, Andhra Pradesh, India. His research interests include renewable energy, and power
electronics. He can be contacted at email: 19a95a0214@aec.edu.in.
Mayur Barman received the M. Tech degrees in electrical engineering from
Tezpur University, Assam, India, and the Ph.D. degree in electrical engineering from NIT
Slicher, Assam, India 2019. He has been an Assistant professor of electrical and electronic
engineering with Aditya Engineering College, since 2019. His research interests include to
power system demand analysis, and Power electronics. He can be contacted at email:
barman.mayur@yahoo.com.
Durgesh Nandan did his Doctor of Philosophy (Ph.D.) from Department of
E.C.E., Jaypee University of Engineering and Technology, Guna, Madhya Pradesh, India in
year 2018 with the specialization in VLSI. He found various prestigious awards like JSS
fellowship, Young Personality of the Year Award (below 40 years)” and I2OR Preeminent
Researcher Award 2019”. He awarded IEEE senior membership in 2020. He is inventor/Co-
inventor of 4 Indian patent. He is the author or a co-author of 2 books. His research interest’s
extent in number of areas like computer arithmetic, VLSI architecture for signal processing
applications, Speech Processing, Hardware architecture of real time big data/AI applications,
and Internet on Things. He can be contacted at email: durgeshnandano51@gmail.com.
Tripuathi Abhilash received the B. Tech. and M. Tech. degrees in electrical
engineering in 2009 and 2012, respectively, and the Ph.D. degree in electrical engineering
according from National Institute of Technology, Warangal, India, in 2020. He has been a
Research Mentor of electrical engineering with AKMS, since 2020. He has authored or
coauthored more than 20 refereed journal and conference papers. His research interests include
the applications of power electronics, and control. He can be contacted at email:
abhilash.tripuathi@accendere.co.in.

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