International Journal of Engineering Trends and Technology (IJETT) – Volume 8 Number 6- Feb 2014
Performance Analysis of Z-Source Inverter for
Various Pulse Width Modulation Techniques
Gokarakonda Surya Nihanth1, Nerella Chaitanya Kumar2 , Balivada Jayanth3 , Charan Tej Yaadav4
1,2,3,4
Final Year B.Tech, EEE, KLUniversity, Vaddeswaram, Guntur
Abstract -The voltage source inverter is a buck (step
down) inverter for dc-to-ac power conversion and it is
a boost (step-up) rectifier (or boost converter) for ac
to-dc power conversion, i.e the voltage of VSI is
limited below or exceeded above its dc-rail voltage
this problem of voltage source inverter can be
overcome by using a z source network between
switching devices and dc-rail. In this paper various
pulse width modulation techniques like sine pwm,
third harmonic pwm, space vector pwm were applied
to z-source inverter. The simulation is done using
Simulink.
Keywords: z-source inverter, sinepwm,space vector
pwm, thirdharmonic pwm.
I.
INTRODUCTION
The Z-Source inverter refers to an inverter which
has the combined characteristics of both the
voltage source inverter and the current source
inverter to convert direct current feed to alternating
current feed. Generally the problem associated with
the voltage source inverter is that the ac output
voltage is limited below and cannot exceed the dcrail voltage or the dc-rail voltage has to be greater
than the ac input voltage. Therefore, the V-source
inverter is a buck (step-down) inverter for dc-to-ac
power conversion and it is a boost (step-up)
rectifier (or boost converter)
for ac-to-dc power conversion. For applications
where over drive is desirable and the available dc
voltage is limited, an additional dc-dc boost
converter is needed to obtain a desired ac output.
The problem relating to the current source inverter
is the ac output voltage has to be greater than the
original dc voltage that feeds the dc inductor or the
dc voltage produced is always smaller than the ac
input voltage. Therefore, the I source inverter is a
boost inverter for dc-to-ac power conversion and
the I-source converter is a buck rectifier (or buck
converter) for ac-to dc power conversion. For
applications where a wide voltage range is
desirable, an additional dc–dc buck (or boost)
converter is needed. So, to overcome these
problems we use Z-source inverter where
the crossover operation of two inductors (choke)
and two capacitors (condenser) is used for both the
step up (boost) operation and step down (buck)
operation is possible to get the desired output.
II.
SINUSOIDAL PULSE WIDTH
MODULATION
In single-pulse and multiple pulse modulation
techniques the width of all pulses are same but in
sinusoidal pulse width modulation the width of
each pulse is varied in proportion to the amplitude
of a sine wave. In this technique the gate signals
are generated by comparing a sinusoidal reference
signal with a triangular carrier wave. The DF and
LOH are reduced significantly. The output voltage
is obtained from the mat lab results. The DF and
LOH are measured by using FFT analysis. The gate
signal for the inverter is obtained by taking the
repeating sequence( triangular wave)as the control
signal and comparing it with the reference
wave(sinusoidal wave).In order to detect or
eliminate the zero sequence currents we use zero
hold circuit and by comparing the with the help of
greater than or equal to blocks.
Fig.1 sine pwm pulse generator
Fig.2 three phase z-source inverter
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International Journal of Engineering Trends and Technology (IJETT) – Volume 8 Number 6- Feb 2014
III.
THIRD INJECTION PWM
In sinusoidal pwm the dc bus in not completely
utilized as the peak of reference signal goes above
the carrier signal peak i.e reaching over modulation
region, in order to get the reference signal to
modulation region third harmonic is injected into
the fundamental signal and compared with carrier
signal. Injection of third harmonic does not affect
output because triplen harmonics are not present in
output.
Fig. 3 sine pwm three phase voltages
Fig.5 third harmonic pulse generator
Fig.6 third harmonic three phase voltages
Fig. 4 Sine pwm output FFT Analysis
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International Journal of Engineering Trends and Technology (IJETT) – Volume 8 Number 6- Feb 2014
STEPS TO IMPLEMENT SVPWM, THE
CONVENTIONAL METHOD:
1) The sector in which the tip of the reference
sector is situated is to be determined from the
instantaneous phase references Va *, Vb * and Vc*



Va *, Vb *, Vc * vα,vβ Θ= tan-1(vβ/vα)
α = Θ- k(600) ; k such that α < 600
Sector number = k + 1
2) Computation of T1 and T2; here lookup tables
are needed to know the values of Sin (600- α) and
Sin α
3) Determination of switching vectors.
Using the corresponding sector information the
actual switching time for each inverter leg is
generated from the combination of effective times
and zero sequence time. Equating volt-seconds
along the α -axis:
(ІVsrІcosα)* Ts = Vdc *T1 + (Vdccos600) * Ts
Equating volt-seconds along the β -axis:
(ІVsrІsinα) * Ts = (Vdcsin600) *T2
Solving the above two simultaneous equations, one
gets:
Fig.7 thirdharmonic pwm FFT analysis
IV.
SPACE VECTOR PULSE WIDTH
MODULATION
Space vector modulation is a PWM control
algorithm for multi-phase AC generation, in which
the reference signal is sampled regularly; after each
sample, non-zero active switching vectors adjacent
to the reference vector and one or more of the zero
switching vectors are selected for the appropriate
fraction of the sampling period in order to
synthesize the reference signal as the average of the
used vectors. The topology of a three-leg voltage
source inverter is Because of the constraint that
T1 
| v sr | Ts sin( / 3   )
Vdc sin( / 3)
T2 
| v sr | Ts sin 
Vdc sin( / 3)
|Vsr | represents the length of the reference Vector
and  is measured from the start of the vector.
4) Assert the appropriate control signals to affect
the required switching action.
the input lines must never be shorted and the
output current must always be continuous a
voltage source inverter can assume only eight
distinct topologies. Six out of these eight
topologies produce a nonzero output voltage and
are known as non-zero switching states and the
remaining two topologies produce zero output
voltage and are known as zero switching states.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 8 Number 6- Feb 2014
Fig.9 space vector pwm implementation
Fig.8 Switching sequence
TABLE I
Sector no.
1
2
3
4
5
6
On-sequence
8-1-2-7
8-3-2-7
8-3-4-7
8-5-4-7
8-5-6-7
8-1-6-7
Off-sequence
7-2-1-8
7-2-3-8
7-4-3-8
7-4-5-8
7-6-5-8
7-6-1-8
The above mentioned algorithm is implemented in
Simulink and is as shown
Fig.10 space vector pwm three phase voltages
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International Journal of Engineering Trends and Technology (IJETT) – Volume 8 Number 6- Feb 2014
Phase Voltage Source Inverter” IJERT, Vol.2
Issue-5.
[5]. Trzynadlowski, A.M. “An overview of
modern PWM techniques for three-phase, voltagecontrolled, voltage-source inverters”. Industrial
Electronics, 1996. ISIE '96., Proceedings of the
IEEE International Symposium on (Volume:1 )
[6]. B. K. Bose, Power Electronics and Variable
Frequency Drives:Technology and Applications.
IEEE Press, 1997
Fig. 11 space vector pwm FFT Analysis
V.
CONCLUSION
The pulse width modulation strategies like
sinusoidal pwm, third harmonic pwm, space
vector pwm are implemented by Simulink for
z-source inverter. The output voltages are
analysed , the dc-bus utilization improved for
each modulation techniques. The total
harmonic distortion got reduced to each
technique.
REFERENCES
[1]. Mohan, Undeland, Riobbins, “Power electronic
converters, applications and design” WILEY
STUDENT EDITION.
[2]. Muhammad H. Rashid, “Power electronic
circuits,devices, and applications. Low price
edition.
[3]. Md. Shahinur Islam, Nazmul Islam Raju,
Ahsan Uddin Ahmed “Sinusoidal PWM Signal
Generation Technique for Three Phase Voltage
Source Inverter with Analog Circuit & Simulation
of PWM Inverter for Standalone Load & Microgrid System” IJRER, Vol.3 No.3
[4]. Prachi S. Dharmadhikari, Gaurav N. Goyal
“Analysis & Hardware Implementation Of Three-
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