International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014)
Maximum Constant Boost Control of SL-Z-Source Inverter
Gaurav Sharma1, Ankita Kosti2
1
2
M-Tech Student, S.R.I.T. Jabalpur (M.P)
Assistant Professor, Dept of Electrical Engineering, S.R.I.T. Jabalpur (M.P)
Abstract — This paper explores Switched Inductor (SL) Zsource inverter which adjusts the voltage and have
application in Fuel cells (FCs) which have achieved global
attention as an alternative power source for hybrid electric
vehicles (HEVs). The proposed inverter uses inductor and
capacitor circuit to join the source and load circuit. On
comparing with the initial Z-source inverter, the explored
circuit and the new inverter increases the reliability and the
performance of the circuit by finding the solution between M
and D. A Maximum Constant Boost which is used as a
controlling strategy for the system which gives the benefit
that the output voltage can be increased or decreased both.
Constant boost control also reduces the voltages stress and
cost of inverter .The results are verified and analysed in
MATLAB/Simulink environment.
Fig.1. Traditional I -Source converter
Index terms— Duty Ratio, Inverter, Maximum Constant
Boost, Modulation Index .
I. INTRODUCTION
Voltage and current-source inverters [1], [3] are widely
used in industries for various purposes like for ac motor
drives, distributed power systems, uninterruptible power
supplies, hybrid electric vehicles etc. However, these
inverters suffer from some major problems such as a
voltage source inverter cannot have an ac output voltage
higher than dc source voltage . Moreover it can only
provide buck dc-ac power conversion. Similarly, a currentsource inverter cannot have an ac output voltage lower than
dc source voltage and hence can only provides only voltage
boost dc-ac power conversion .
So, for applications where both buck and boost voltage
are demanded, there two-stage power conversion is
performed by both voltage- and current-source inverter and
this leads to high cost and low efficiency [2].
Fig.2. Traditional V- source converter
As there are certain limitations in case of VSI and CSI,
so Z-source (impedance source) power converter come into
existence which employs a unique impedance network or
circuit to couple the converter main circuit to the power
source, load or other features that cannot be observed in the
traditional V- and I-source converters. Z-source converter
overcome the limitations of VSI and CSI.
406
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014)
In this paper, the techniques of SL are integrated into
classical Z-source impedance network and hence new SL
Z-source impedance network is proposed and its maximum
constant boost control is done through simulation [4].
Fig.4. Equivalent circuit of the SL Z-source inverter viewed from the
dc-link bus.
1) Shoot- Through State: In this substate, S is ON, while
both Do and Din are OFF. D1 and D2 are ON and D3 is OFF
for the top SL cell. L2 and L4 are charged by C2 in parallel.
This state leads to additional zero state produced by the
shoot-through actions of the top and bottom arms. The
equivalent circuit is shown in Fig.6(a). Both top and bottom
SL cells perform the same function of absorbing the energy
stored in the capacitors.
2) Non-Shoot-Through State: This state has two zero states
and six active states of the main circuit as shown in
Fig.6(b). During this substate, S is OFF, while both D o and
Din are ON. D1and D3 are OFF, and D5 is ON for the top SL
cell. L1 and L2 are connected in series and the energy stored
is transferred to the main circuit. D4 and D5 are OFF and D6
is ON for the bottom SL cell, L3 and L4 are connected in
series and the energy stored is transferred to the main
circuit. During the shoot-through state, C1 is charged by Vin
via bottom SL cell, and C2 is charged by Vin via top SL
cell.
Fig.3. Topology of proposed SL Z source inverter.
II. ANALYSIS OF TOPOLOGY OF SL Z-SOURCE INVERTER
The proposed SL Z-source inverter shown in fig.4.
consists of four inductors (L1, L2, L3 and L4), two
capacitors (C1 and C2), and six diodes ( D1, D2, D3, D4, D5
and D6). The combination of L1-L3-D1-D3-D5 performs the
function of top SL cell and the combination of L2-L4-D2D4-D6 performs the function of bottom SL cell. Both of
these cells are meant for storing and transferring energy
from the capacitors to the dc bus under the switching action
of the main circuit [5].
A. Operating Principle :
On the basis of switching states of the main circuit
connected with SL impedance network, the operating
principles of SL-ZSI are similar to that of classical ZSI
network as viewed from the dc bus as shown in Fig.5 in
which an active switch S and a passive switch Do are used
for the simulation of the practical shoot-through actions of
the top and bottom arms. Thus the proposed impedance
network has the sub-states which are classified into shootthrough state and non-shoot-through state, respectively.
(a)
(b)
Fig.5. Equivalent circuits.
407
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014)
Table1 .
Stress Comparison in case of same D and Vin
(a) Shoot-through zero state (i.e., switching ON).
(b) Non-shoot-through states (i.e., switching OFF).
B. Boost Ability Analysis of SL-Z Source Inverter:
III. SIMULATION AND EXPERIMENTAL VERIFICATION
Parameters used for the simulation of maximum constant
boost control of SL-ZSI is shown in the Table 2.
Fig.6. Boost ability comparison of the classical Z-source and the
proposed SL Z- source
Table.2
Simulation Parameters
For the comparison of individual boost ability ,the
curves of boost factor B versus duty ratio D for classical Zsource impedance network and the proposed network is
compared in fig 7. As seen boost ability of the proposed
impedance network has increased .
Input DC voltage
Output Line –Line voltage
L1=L2=L3=L4
C1=C2
Carrier frequency
Lf
Cf
Resistive Load
C. Stress Comparison of inverters :
The current stresses of the impedance-type power
converters are different under different control and load
conditions, and the exact current analysis results on the
classical Z-source inverter are still a topic to be explored
[6]–[8]. By considering the same value of D and V in we
can compare stress for classical and proposed inverter
through the Table 1.
48V
100 V
20mH
1mF
10KHz
20mH
30uF
1000W
Maximum Constant Boost Control
In order to reduce volume and cost it is important to
keep the shoot through duty ratio constant . Fig 8 shows
the sketch map of maximum voltage while always keeping
the shoot through duty ratio constant .Because the boost
factor is determined by shoot through duty cycle as
expressed in in order to maintain the constant boost shoot
through duty cycle must be kept same .
408
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 5, May 2014)
Fig .9. Filtered Output line voltages Vab,Vbc and Vca
IV. CONCLUSION
In the paper the focus is on rapidly changing z- source
network .SL-ZSI improves the input current ,reduces
passive count . To control maximum constant boost is used
which has been verified by simulation .It is clear from the
simulation results the ripples in maximum constant boost
control is used and peak value of shoot through current
decreases.
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Fig .7. Waveforms of Maximum Constant Boost Control
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[8]
Fig .8. Output line voltages Vab,Vbc and Vca
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