INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY
VOLUME 5 ISSUE 2 – MAY 2015 - ISSN: 2349 - 9303
Improved Trans-Z-source Inverter for Automobile
Application
Aiswarya P R1
Calicut University, EEE
Aiswarya.kollora@gmail.com
Abstract—In this paper a new technology is proposed with a replacement of conventional voltage source/current
source inverter with Improved Trans-Z-source inverter in automobile applications. The improved Trans-Z-source
inverter has a high boost inversion capability and continues input current. Also this new inverter can suppress the
resonant current at the startup; this resonant current in the startup may lead the device to permanent damage. In
improved Trans-Z-source inverter a couple inductor is needed, instead of this coupled inductor a transformer is used.
By using a transformer with sufficient turns ratio the size can be reduced. The turn’s ratio of the transformer decides
the input voltage of the inverter. In this paper operating principle, comparison with conventional inverters, working
with automobiles simulation results, THD analysis, Hardware implementation using ATMEGA 328 P are included.
Index Terms— Boost inversion Capability, Coupled inductor, Improved Trans-Z-Source Inverter, Resonant current
suppression, transformer
a combination of switching devices and diodes in an
antiparallel combination. L1,L2 are separate inductors but
proposed system it is a coupled inductor. In figure.1 the DC
source is a fuel cell stack[3].
1 INTRODUCTION
T
HE Z-source inverter is a three phase 3 leg 6 switch
inverter with an impedance network at the source side
of the inverter followed by the DC source. This
impedance network may contain several capacitors an
inverters, value of this capacitors/inductors are varying the
DC input voltage level to the inverter. The Improved trans-Zsource inverter proposed in [1] which can be worked as both
voltage source inverter and current source inverter. In
addition to that this Improved trans-Z-source inverter is
capable of working in both boost and buck conditions. It
functions as a buck-boost inverter without making use of DCDC Converter Bridge due to its unique circuit topology.
Different types of Z source inverter topologies using Pulse
Width Modulation strategies have been published in [3]-[5]
and their applications in [7],[8]. Three level neural-pointclamped topology is published in [9] and[10],direct ac–ac
converters [11], [12], and other Z-network topologies [13]–
[14]. Quasi-Z-source inverters are used to overcome the
disadvantages of the conventional Z-source inverter [15]–
[17], and have advantages such as a reduction in the passive
component ratings and an improvement in the input profiles.
Some researchers have recently focused on improving the
boost factor of the Z-source inverter. This can be achieved
using a very high modulation index in order to achieve an
improvement in the output waveform [18]–[25].
Fig 1 Conventional Z-source inverter
The conventional Z source can work even the upper and
lower switches are active at the same time. This can be for
only one leg among three legs or for all three legs. This
switching period is known as shoot through (ST).When either
1 switch from a leg is gated then this switching period is
known as non- shoot through (NST)[4],[5].The equivalent
circuit of figure 1 is redrawn in figure 2 and 3 for shoot
through and non shoot through respectively. Non shoot
through has 6 switching states depending upon different
switching combinations. Z-source inverter shown in figure 1
can be drawn as in figure 2 for shoot through period, the
inverter side is acting as a voltage source. The circuit can be
redrawn as shown in figure 3 non-shoot through period (for 6
switching combinations).Here the inverter is acting as a
current source.
2 CONVENTIONAL Z-SOURCE INVERTER
To overcome the drawbacks of the conventional voltage
source inverter and current source invert the Z-source inverter
is introduced. It consists of a unique impedance network. In
figure.1 two inductors L1,L2 and capacitors C1,C2 are
connected in X shape which is coupling a three phase inverter
and a DC source. The Z source can be used to either connect
DC source or another converter circuit. Therefore, the dc
source can be a battery, switches used in the converter can be
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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY
VOLUME 5 ISSUE 2 – MAY 2015 - ISSN: 2349 - 9303
TABLE 1
COMPARISON OF ZSI WITH CONVENTIONAL
VSI&CSI
Fig 2 Equivalent circuit of Z-source inverter
during shoot through
ZSI
Conventional
Inverter
Can function as both as
VSI and CSI
Has buck-boost capability
Can function as either VSI
or CSI
Either Buck or Boost
Shoot through is present
Shoot through is absent
Output Voltage can be
varied by varying the
boost factor/modulation
index
Output voltage depend
upon the firing pulses and
the input dc voltage
3 IMPROVED TRANS-Z SOURCE
INVERTER
The Improved trans-Z source inverter is shown in figure 4.
It consists of inductor L1, for the function of coupled
inductors L2 and L3 a transformer of turn’s ratio 1: n two
capacitors C1 and C2, a main diode D1 are connected.
Fig 3 Equivalent circuit of Z-source inverter
during non-shoot through
The ratio between the input voltage of the inverter v i and
the DC input voltage V0 is defined as the boost factor (B) of
the Z-source inverter. Boost ratio can be written as
B=
𝑣𝑖
𝑉0
Fig 4 Improved trans-Z-source
(1)
Main advantages of improved trans-Z source inverter over
conventional z source inverters are the boost inversion
capability, continuous input current and resonant current
suppression.
This can be rewritten in terms of duty ratio/ turn on time,
turn off time
1
1
B = 2𝑇 0 =
(2)
1−
𝑇
1−2𝐷
2.1 Operating Principle
The Improved trans-Z-source inverter has shoot through
states and non-shoot through states same as that of the Z
source inverter. Shoot through state is the condition when
both upper and lower switches are gated together, during the
shoot-through state, the diode D is OFF[1]. In non shoot
through state inverter may be either in six active stages or
two zero stage, during non-shoot through diode D is ON.
Equivalent circuit of improved trans-Z-source inverter is
shown in figure 5. Equivalent circuit for shoot through state
is shown in figure 6. Equivalent circuit of non-shoot through
state is shown in figure 7. The boost factor is defined as the
ratio of input voltage of the inverter to the DC input[1].
The boost factor (B) is given by
Where T0 = turn on time
T=turn off time off time
D= duty ratio
Z-source inverter is compared with conventional
inverters and tabulated in table 1.From this comparison it is
clear that further studies can result a efficient Z-source
inverter. The voltage boost capability can be changed by
changing the boost factor (B) with the help of varying the
impedance value of the Z-source network[3]-[6].
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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY
VOLUME 5 ISSUE 2 – MAY 2015 - ISSN: 2349 - 9303
𝐵=
=
with ITZSI a three phase induction motor is represented with
a three phase inverter. When the application changes or in
other words when the inverter is feeding servo motor or
stepper motor a single phase inverter is used. Automobile
application with improved trans-Z source inverter
arrangement is as shown in figure 8.
1
1− 2+𝑛 𝐷
1
𝑇
1−(2+𝑛 ) 0
(3)
𝑇
Where T0 = turn on time
T=turn off time off time
D= duty ratio
Fig 8 Arrangement Of Automobile Application With Improved
Trans-Z Source Inverter
If an induction motor is used the speed of the induction
motor can be controlled by changing the impedance of the Znetwork. In order to make a change in impedance turn’s ratio
n is varied [7].
Fig 5 Equivalent Circuit Of Improved Trans-Z-Source Inverter
4 SIMULATION RESULTS
To analyze the usage of Improved trans-Z source inverter
in automobile application the circuit is simulated using
MATLAB R2014a SIMULINK. selected the simulation
parameters L3 =1 mH,C1=C2 =1000 μF, Lf =1.5 mH, Cf =10
μF, and R = 50 Ω/phase. The turn ratio of the transformer is
2. The magnetic inductance measured from the primary side
was set to 0.737 mH. The leakage inductance was set to 0.5
μH. The switching frequency was 10 kHz, the input was 100
Vdc, and the output phase voltage was 115 Vrms to meet the
grid-tied requirement. Constant boost control was used [1].
The simulation diagram is shown in figure 9.
Simulation parameters details are given in table2.Also the
simulation of the control circuit providing pulses for the
power switching devices are done with ISIS schematic
capture. For this the controller ATMEGA 328 P from the
manufacturers ATMEL is used. The pulse generated using
ISIS schematic capture is shown in figure 10. This is
displayed in a digital oscilloscope.
The simulation results are represented in figure 11 and
figure 12 respectively. Speed and torque characteristics are
represented in figure 11.Phase voltage and phase current are
represented in figure 12.
The FFT analysis is also done to understand the Total
Harmonic Distortion of the circuit. The total harmonic
distortion is defined as the measure of closeness of the
Fig 6 Equivalent Circuit Shoot-Through State
Fig 7 Equivalent Circuit Non-Shoot-Through State
2.2 Automobile Application
The boost factor of improved trans-Z-source inverter is
higher as compared to the conventional Z-source inverter.
The boost capability depends upon the term n in equation (3)
which is representing the turn’s ratio of the transformer
which is replacing the coupled inductor[7]. As discussed
earlier the boost inversion capability and the continues input
current are the reason for opting the improved tans-Source
inverter for an automobile application. This new inverter
technology can drive several motors in an automobile which
is running under AC condition. Servomotor driving the power
window and stepper motor driving the power steering
commonly found in electric vehicles are example for them.
For the purpose of explaining the working with motor along
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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY
VOLUME 5 ISSUE 2 – MAY 2015 - ISSN: 2349 - 9303
Fig 9 simulation diagram of improved trans-Z source inverter
TABLE 2
SIMULATION TABLE OF IMPROVED TRANS-ZSOURCE INVERTER FOR SPEED CONTROL OF
INDUCTION MOTOR
Input DC voltage
100V
Output phase voltage
115 Vrms
Capacitors
1000µF
Turn ratio
1:2
Primary
Transformer
0.737mH
inductance
Fig 10 Pulses For Six Switching Devices
Leakage
0.5µH
inductance
Inductor L3
1mH
Switching Frequency
10kHz
Three-Phase
Lf
1.5mH
output Filter
Cf
10µF
50Ω/phase
Three-phase resistive load
Fig 11 Speed And Torque Characteristics
obtained waveform to the shape of its fundamental
waveform. And is given by the equation
1
𝑇𝐻𝐷 =
𝑉1
∞
𝑉𝑛2
𝑛=1,2,3….
Where,
𝑉1 =voltage of the fundamental voltage
𝑉𝑛 =voltage of the nth wave
The amount of Total Harmonic Distortion (THD) is found
2.15% which is an appreciably low value for such a circuit
with six power switching devices and an impedance network.
FFT analysis for the circuit is shown in figure 13. So this
improved trans-Z source inverter has a very fair value for
THD. Along with other advantages like boost inversion
Fig 12 Phase Voltage And Phase Current
capability, continuous input current, suppression of startup
current this can be added.
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VOLUME 5 ISSUE 2 – MAY 2015 - ISSN: 2349 - 9303
the speed and torque characteristics, phase voltage and
current.
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Fig 13 FFT Analysis for the Circuit
5 HARDWARE IMPLEMENTATION
The prototype of improved trans-Z source inverter for
automobile application is shown in figure 15. The switching
devices are commercially available 600-V MOSFET
(IRFZ44N) modules. The controller used for giving gate
pulses to the switching device is ATMEGA 328 P from the
manufacturers ATMEL. And other parameter values are same
as that mentioned in simulation result’s session. The proto
type is running a 6V servo motor.
Fig 14 Prototype Of Improved Trans-Z Source Inverter For
Automobile Application
6 FUTURE SCOPE
This technology can also be used for driving the main
motor drive in an electric vehicle which is using a three phase
induction motor instead of driving auxiliary drives like power
window, power steering, and wipers. This technology can
also be used with a matrix converter. Trans-Z source with
matrix converter for automobile application this can reduce
DC link and the power conversion can be done in a single
stage.
7 CONCLUSION
A new topology was proposed to improve the trans-Zsource inverter for automobile application, which is driving
auxiliary drives in automobiles with the following main
advantages: high boost voltage inversion ability, continuous
input current, and resonance suppression at start-up.
The experimental results for dc 100 V input and ac 115
Vrms phase output verified the high step-up inversion ability,
and the simulation and experimental results show that the
proposed inverter has high boost inversion ability with
continuous input current. Also the simulation results shows
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VOLUME 5 ISSUE 2 – MAY 2015 - ISSN: 2349 - 9303
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Author’s Profiles
Aiswarya P R has obtained
B.Tech degree in Electrical and
Electronics Engineering from
Veda
Vyasa
institute
of
Technology,Malappuram,Kerala
.She
is
pursuing
4th
semester,M.Tech
in
Power
Electronics at Veda Vyasa
institute
of
Technology
Malappuram,Kerala.Life
time
Member in ISTE
M.no: LM86920. Her current research interests are in Z source
inverters applications in Electric vehicles, Multi Level inverters
simulation and modelling
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