An Improved the High Voltage Boost Inversion Ability of Switched Inductor Quasi ZSI by PWM Technique

IJSRD - International Journal for Scientific Research & Development| Vol. 3, Issue 10, 2015 | ISSN (online): 2321-0613
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An Improved the High Voltage Boost Inversion Ability of Switched
Inductor Quasi ZSI by using PWM Technique
Srishti Ujjainiya1
J.S.Shakya2
1
M.E. (PE)
1,2
Department of Electrical Engineering
1,2
Samrat Ashok Technological Institute (SATI), Vidisha, Madhya Pradesh, India
Abstract— This paper presents an improved the high voltage
boost inversion ability of switched inductor quasi ZSI by
using Boost PWM technique. This presents a comparative
analysis of Boost Inversion Ability of Switched Inductor
Quasi z-source inverter (SL-QZSI) with conventional z-
source Inverter (ZSI). In comparison to conventional ZSI for
the same value of voltages in the input and output the
proposed SL-QZSI provides the less count on passive
component a dc-source with common ground less voltage
across the capacitors it gives the continuous input current
current shoot through is reduced and also the current stress
across the inductor and diodes are reduced. This thesis
presents the operating principle boost inversion ability
analysis simulation results and comparison of conventional
ZSI with SLQZSI The simulation results confirmed the
ability of high step up inversion by this proposed SL-QZSI.
An extended switched inductor quasi z-source inverter
(ESL-QZSI) with high boost voltage inversion ability is
presented which combines the SL-QZSI with the traditional
boost converter as well as improves the switched-inductor
cell. Compared with the classic SL-QZSI topologies the
proposed topology reduces the voltage stresses of capacitors
power devices and diodes for the same input. The operation
principle of the proposed topology is analyzed in detail. In
addition, the performance of the proposed topology is
verified by simulations and experiments.
Key words: ZSI, SL-QZSI, Boost inversion ability, ESL-
QZSI
I. INTRODUCTION
The z-source inverter (ZSI) has elicited much interest
recently because of its obvious advantages compared with
the classical voltage source inverter. First ZSIs utilize the
shoot-through of the inverter bridge to boost voltage and are
thus more suitable for application with low input voltages,
such as photovoltaic and fuel cells Second no dead time
exist b/w the conduction of the upper switch and that of the
lower switch thus, the distortion of the output waveform is
reduced 3rd boost and inversion of the voltage are realized
with single-stage power conversion; efficiency are thus
increases Lastly ZSIs exhibit better immunity against EMI
noise. However, classic ZSI have obvious disadvantage such
as high voltage stresses in the switches and capacitors, huge
inrush current, and weak boost ability. The most significant
drawback is the discontinuous i/t current, which limits the
use of ZSIs and causes lifetime damage to the DC source
pulse width modulation (PWM) method such as the
maximum boost control method and the constant boost
control method, have been developed to overcome these
drawbacks and obtain reduced voltage stress and increased
boost ability However these PWM method have yet to
extend the voltage gain without sacrificing the device cost as
well as avoid the discontinous input current the
improvement of circuit topology appears to be an
opportunity for ZSIs.
An improved ZSI was proposed to reduce the
capacitors voltage stress and start up inrush current;
however, boost ability remained unchanged and the i/t
current was still discontinuous. A novel family of extended
boost ZSIs was developed Diode or capacitor assistances
was applied to increase the boost ability and make the input
current continuous. However these extended boost ZSI have
obvious short coming such as small boost effect,
complicated structure, and large size. Compared with the
classic ZSI QZSI has a lower rating and fewer power
devices, continuous input current, and lower current stresses
for the DC source a common ground point also exists in
QZSI for the DC source and the inverter. The boost ability
of QZS Is remains limited.
Switched capacitor (SC), switched inductor (SL),
and hybrid SC/SL techniques are commonly used in DC–
DC converter to achieve high boost capability with
transformerless cascade structures thus size is reduced and
power density is increased. ZSI and SL techniques were
successfully combine to overcome the boost limitation of
the classical ZSI a switched-inductor z-source inverter (SL-
ZSI) was presented. Compared with 2 isolated DC sources
were embedded into the SL-ZSI topology to make the input
current continuous, suppress the voltage stress and improve
reliability. The modulation index and shoot through duty
ratio are the two independent control variables of the
conventional ZSI. By increasing the shoot through duty
ratio, voltage boost of the ZSI can be improved while the
output ac voltage is keeping up according to the modulation
index There is a concession among the shoot through duty
ratio and the modulation index: if a high modulation index is
used, only a small shoot through duty ratio can be utilized
and if a small modulation index is used only a high through
duty ratio can be utilized.
It is need to increase the duty ration of shoot
through of the inverter bridge voltage from a low voltage dc
source, to give a strong boost factor in the conventional ZSI.
A small modulation index is utilized for getting large shoot
through duty ratio. A small modulation index is reported for
reduced the amplitude of the ac output voltage and also
decreases ac output performance. Moreover, when a large
shoot through duty ratio is applied then a high voltage stress
imposed on inverter-bridge and z-source capacitor. Hence
the conventional z-source inverter has restriction to give
both a high boost factor and a high output voltage
simultaneously.
Dynamic modeling and boost control methods
pulse width modulation methods and other z-source network
topologies are analyzed QZSI is developed to overcome the
drawbacks in conventional ZSI is analyzed. Compared with
conventional ZSI QZSI have ability to provide improving

An Improved the High Voltage Boost Inversion Ability of Switched Inductor Quasi ZSI by using PWM Technique
(IJSRD/Vol. 3/Issue 10/2015/123)
input profiles reducing passive component ratings and but
there is no improvement on voltage boost ability.
The proposed SL-QZSI is based on the well-known
QZSI topology and adds only one inductor and three diodes.
This topology is studied under the assumption that all
components are ideal. The switched inductor quasi z-source
inverter (SL-QZSI) in not only has fewer passive
components but also produces lower stress on the capacitors,
inductors, and diodes. The typical switched inductors are
replaced by a bootstrap capacitor and boost inductors
derived from without increasing the complexity of the
circuit.
II. Z-SOURCE INVERTER
The traditional voltage and current inverters have been
seriously restrict due to their narrow obtainable output
voltage range short through problem causes by misgating
and some other theoretical difficulties due to their bridge
type structure. The topology of the z-source inverter was
proposed to overcome the problems in the traditional
inverters in which the function of the traditional dc-dc boost
converter has been successfully introduced into the inverter
by a unique x-shape impedance network z-source inverters
are recent inverter topology that can perform both buck and
boost functions as a single unit A unique feature of z-source
inverter is the shoot through states by which 2
semiconductor switches of the same phase leg can be turn
ON simultaneously Therefore no dead time is need and o/p
distortion is greatly reduced and thus reliability is greatly
improve This feature is not available in the voltage source
and current source inverters.
z-source inverter are mainly applied for load that
demand a high voltage gain such as motor drives and as a
power conditioning unit for renewable sources like solar
fuel cells etc to match the input source voltage differences
The development in z-source inverter topology provides a
consecutive enhancement in voltage gain and output
waveforms. A trade off between the boost capability and
component count is always a major concern to keep the cost
stable.
It is to be noted that increase in the component with
suitable modification can improve the performance of these
types of inverters The topology growth has been in terms of
addition or reduction of passive component inclusion of
extra semiconductor switches alteration two or inclusion of
dc sources and also changes of modulation schemes etc.
Voltage buck inversion ability is also provided for those
application that need low ac voltages.
The z-source concept is applicable on all direct
current to alternating current, ac-to-dc, ac-to-ac and dc-to-dc
power conversion.
The configuration of a ZSI consists of the
following components:
- Two Inductors
- Two Capacitors
- DC source
- Inverter or Converter
- Load or Converter
Fig. 1: Z-source Inverter
A ZSI structure use the series combinations of
IGBT and diode It overcomes all the theoretical barriers
and limitations of the VSI and CSI and give rise to power
conversion concept Figure depicts a two-port network that
consists of two split inductors L1 L2 and capacitors C1 C2
connected in X shape to provide an impedance source (z-
source) coupling the converters to the dc source load or
another converters. The dc source or load may be either a
voltage or a current source or load Hence the dc sources
can be a batteries diode rectifier thyristor converter fuel cell
an inductors a capacitors or any combinations of these
Series combinations of IGBTs and diode are used as
switches in the converter circuits The inductances can be
provided by a split inductors or two separate inductors.
A. The classical ZSI has some limitations:
1) In some applications, the current taken from the dc
input source is intermittent.
2) DC source and converter does not share the common
ground.
3) It needs a dc link coupling capacitor is connected
across the energy source to protect unwanted
discontinuity of current.
Boost factor B can be expressed as conversion relation
between dc-link voltage across the inverter bridge Vdc and
the input source voltage Vin.
Where To is the interval of shoot through zero state
during a switching cycle T and D is duty ratio of each cycle
D=To/T
From equation , it is observed that D should be
limited to minimum value zero to 0.5 the maximum value In
this range the impedance network can achieve step up dc-dc
conversion from Vdc to VPN But the large value of D needs
to be taken for a low voltage dc energy source to provide a
very high boost factor. Hence z-source converter should be
operated for a long interval of shoot through zero state.
III. SL-QZSI TOPOLOGY
The proposed inverter consists of three inductors (L1, L2
and L3 ), two capacitors (C1 and C2) and four diodes (Din
D1 D2 and D3). The combination of L2-L3-D1-D2-D3 acts
as a switched inductor cell The proposed topology provide
in rush current suppression however the inductors and
capacitors in proposed inverter still resonate. Compared
with a conventional QZSI the proposed inverter adds only

three diodes and one inductor. Like the classical ZSI the
proposed SL-QZSI has extra shoot through zero states
besides the traditional six active and two zero states as in
classic ZSI Thus the operating principle is same to classic
ZSI For the purpose of analysis the operating state are
classified into shoot through and non shoot through state.
Fig. 2: SL-QZSI circuit
IV. EXTENDED SWITCHED INDUCTOR QUASI Z-SOURCE
INVERTER
The general structure of ESL-QZSI, which consists of four
inductors (L1, L2, L3, L4), three capacitors (C1 C2 C3) five
diodes (D1 D2 D3 D4 D5) and one switch (S). The proposed
topology combines it with a typical boost circuit and one
inductor is replaced by an improved switched inductor cell.
Compared with SL-QZSI, one inductor, one capacitor & 1
switch are added Further more the proposed topology uses
only one more capacitor & one more switch As seen only a
few components are added in ESLQZSI The proposed
topology possesses much higher boost ability with the same
shoot through duty ratio than the other topology to improve
the output voltage profile For the same input.
V. SIMULATION RESULTS
The PWM of ZSI circuit is shown in fig.3.
Fig. 3: ZSI
To verify the improved boost ability of proposed
technology, The initial voltage is assumed to 0 volt in the
capacitor C1 and C2 of the both inverter. The 50hz assigned
the switching frequency (fs). The input dc source voltage is
48Vdc The line to line voltage and the Pulse Width
Modulation (PWM) control was used here in this simulation
and all components are ideal.
To produce the required L-L voltage of 190volts
(Vrms) from the dc input source with maximum boost
control for the main power circuit of SL-QZSI, we get
Vc1=94V Vc2=93V.
Fig. shows the proposed simulation diagram of SL-
QZSI circuit and the simulation results is shown in the Fig.
with maximum boost control the C1 and C2 voltages are
boosted to 95V and 90V in steady sate respectively peak
VPN is boosted to 190V. Due to the resonance created in the
quasi impedance-source inductors and capacitors inrush
current in the proposed SLQZSI appears. However, the less
inrush current is obtained in this SL-QZSI then the
conventional ZSI. Fig. is shows the simulation diagram of
conventional ZSI topology to obtained 125 volts of Vrms in
the output L-L voltage from the same 48 volts input dc
source with high boost control instead of the conventional
ZSI, Fig. shows the simulation results for the conventional
ZSI.Even though the proposed SL-QZSI needs more
inductors and diodes than the conventional one total
inductance used in the proposed SL-QZSI is equal or lower
than that of one inductor in the conventional ZSI. Thus
volume and cost of the proposed system are almost same as
those of the conventional one.
Fig. are shows that, to produce same output L-L
voltage of 190 volts (Vrms) from 48 volt of input dc voltage
develops low voltage stress across the capacitors higher
peak dc link voltage (Vpn), peak shoot through current is
low in the proposed circuit of SL-QZSI instead of
conventional ZSI.
Fig. shows the components voltage stress on z-
source capacitor versus voltage gain G of the proposed SL-
QZSI and the conventional ZSI Fig. shows the voltage stress
on inverter-bridge versus voltage gain G and from the under
the same voltage gain G, the voltage stress on the z-source
capacitor and the inverter bridge of the proposed SLQZSI
are much lesser than that of the conventional one.
Fig. 4: Input voltage

Fig. 5: Output voltage
Fig. 6: Circuit of proposed slqzsi
Fig. 7: Inductor current
Fig. 8: Output voltage
Fig. 9: Extended SL-QZSI
Fig. 10: Inductor current

Fig. 11: Capacitor Current
Fig. 12: Capacitor Current
Fig. 13: Output Voltage.
VI. CONCLUSION
An improved ZSI topology called switched inductor quasi z-
source inverter achieves the high boost voltage inversion
ability. It shares the dc common ground with continuous
input current and the Maximum boost control method is
used to obtain maximum voltage gain.
This method maximize the shoot-through period
and maximum output voltage without disturbing the active
states by turning all zero states into the shoot-through zero
state for a given modulation index.
The SL-QZSI is analyzed theoretically and
experimental modeling is performed in MATLAB/simulink
and the improved performances are compared with those of
the conventional ZSI. The proposed topology has a higher
voltage boost ratio and a lower voltage stress across the z-
source capacitors an inverter bridge compared to the
conventional topology The relationship between voltage
stress of the switches and the voltage gain shows that the
proposed SL-QZSI topology has superior than the
conventional ZSI Implementation with adding some
inductor, capacitor and diode in switched inductor z-source
inverter for more better result is known as an extended
switched inductor quasi z-source inverter with the high
voltage gain and boost inversion ability.
VII. REFERENCES
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An Improved the High Voltage Boost Inversion Ability of Switched Inductor Quasi ZSI by PWM Technique

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