P.R.Sivaraman et al., International Journal of Advanced Engineering Technology
E-ISSN 0976-3945
Research Paper
ANALYSIS AND DESIGN OF DUAL SWITCH Z-SOURCE
CONVERTER WITH REGENERATIVE SNUBBER
1
P.R.Sivaraman, 2S.Bhuwaneshwari, 3C.Kamalakannan
Address for Correspondence
Research Scholar, Department of EEE, St. Peter’s University, Chennai, India
2
PG Scholar, Department of EEE, Rajalakshmi Engineering College, Chennai, India
1,3
Department of EEE, Rajalakshmi Engineering College, Chennai, India
1
ABSTRACTThis paper presents a dual switch Z-Source Converter with regenerative snubber. The existing system has reverse recovery of
current in diode, large input current and leakage inductance. The proposed Z-Source Converter has no reverse recovery problem
and highly boosted DC voltage can be achieved using its impedance network. The leakage inductance in the impedance
circuit can be fed to the switch using regenerative snubber circuit to reduce switching loss, voltage stress and conduction loss.
Then obtained DC voltage can be converted into AC voltage using single phase full bridge inverter and fed to the resistive load.
The diode gets replacement with one additional semiconductor switch to avoid reverse recovery problem in the proposed
system. In the closed loop operation the DC link voltage can be controlled using PI controller to avoid damage of the load. The
results of simulation and hardware of the proposed system were shown and compared to obtain the system performance which
validates its design and working.
KEYWORDS - Dual Switch Z-Source Converter, Regenerative snubber, Single Phase Full Bridge Inverter, PI controller.
1. INTRODUCTION
In recent days, DC to DC converters are majorly
preferred in renewable energy systems, single phase
grid connected alternative energy sources. The voltage
gains of non isolated converters such as boost and
buck–boost converters are limited due to the losses on
the components used. Diodes will have reverse
recovery of current in case of high duty cycle. The
voltage gain can be increased using switched inductor,
switched capacitor, voltage lift techniques. But, this
causes complexity and lower efficiency because of
cascade connections. Even resonant converters increase
the control complexity and stresses on the switching
devices.
To overcome all these drawbacks Z-Source converters
introduced. So far there is an analysis only for Z-source
inverter and single switch Z-Source converter and it has
component stress, switching loss and diode reverse
recovery current and MOSFET Drain source voltage
resulting in low reliability. Here the proposed topology
has dual switch Z-Source Converter which gives highly
boosted DC output voltage. This high step up converter
has no reverse recovery problem of diode and the
leakage inductance from the impedance network can be
reduced .This is possible by raising the current up so
that it can reduce their peak current and which in turn it
reduces voltage spike.
2. OBJECTIVE
The main objective is to analysis, design and simulate
high step up dual switch Z-Source Converter. To
reduce switching loss, voltage stress and leakage
inductance.
3. SYSTEM OVERVIEW
Z-Source Converter is connected with the full bridge
inverter. The DC link capacitor is placed in between
the converter and inverter. The regenerative snubber
circuit is used to avoid voltage stress and switching loss
by reducing leakage inductance. The inverter is used to
control the transit power is controlled across the DClink to maintain voltage constant.
This converted AC voltage given to run an Induction
Motor. Also using the PI controller, voltage of the load
can be maintained. The PI controller tunes the
converter circuit to maintain a constant input voltage to
the inverter by producing corresponding pulses. The
brief discussion of Fig 1 is as follows.
4. DUAL SWITCH Z-SOURCE CONVERTER
The Z-Source Converter unit has its own impedance
network which has boosting capacity. The existing
single switch Z-Source Converter has drawbacks of
reverse recovery of diode current, leakage inductance
leads to high voltage spike and switching loss. The
proposed dual switch Z-Source Converter has the
replacement of diode by MOSFET switch. Here, there
is no problem of reverse recovery of diode. The duty
cycle of the switches are controlled here so that the
level of the input for the converter can be decided.
The proposed topology has no dead time of switching
loss. Due to leakage inductance of the impedance
network results in high voltage spike during switch
transition. The leakage inductance can be reduced by
raising its current level up so that it reduces their
current difference and which in turn reduces voltage
spike too.
Fig 2 Circuit diagram of the proposed converter
Fig 1Block diagram of proposed system
Fig 1 illustrates the schematic diagram of the proposed
system. From the Fig 1, it is seen that the dual switch
Int J Adv Engg Tech/Vol. VII/Issue II/April-June,2016/1080-1082
5. REGENERATIVE SNUBBER
The snubber circuit is kept across the switch to reduce
voltage stress. The capacitance of the snubber capacitor
should be chosen as small as possible (to minimize
conduction losses in the auxiliary components) but still
large enough to slow down the voltage rise across the
main switch to the extent that the turn-off losses are
significantly reduced in Fig 3.
P.R.Sivaraman et al., International Journal of Advanced Engineering Technology
The snubber circuit not only reduces the voltage spikes
but also relieves the high voltage and high current
stresses inflict on switches at both turn on and turn off.
The snubber design is the last step in the power stage
design and is attempted after the values of other circuit
parameters were obtained. One possible design
approach is as follows. As a first pass design, choose a
switch with a reasonable maximum voltage for a given
application. Result in lowest maximum snubber
capacitor voltage.
Fig 3 Regenerative snubber
6. DC LINK
DC link is used to reduce ripples from DC output
voltage and supplies ripple free DC as input to the full
bridge inverter.
7. SINGLE PHASE INVERTER
A single phase full bridge inverter has four switches
which are connected to the load. When transistors S1
and S2 are turned on simultaneously, the positive
voltage Vs appears across the load. When Switches S3
and S4 are turned on, the voltage across the load is
reversed and is –Vs. The rms output voltage can be
found from, A single phase full bridge circuit has peak
reverse blocking voltage of each switch and the
quality of output voltage as same as half bridge
circuit.
E-ISSN 0976-3945
condition gets measured. In closed loop operation the
PI controller is used to maintain the constant input
voltage to the load. The voltage across the switch
without regenerative snubber ranges from 42 V in peak
is shown in this Fig 9. This make the switch to be
damaged has switching loss. The input voltage of the
dual switch Z-Source Converter is 16 V is shown Fig 6.
The proposed converter will step up this input voltage
using its unique impedance network.
Fig 6 DC input voltage
The input DC voltage is shown in Fig 6. Here the
Regenerative snubber recycles the leakage inductance
to the switch itself. This certainly reduces voltage stress
during the turn off state and also switching loss. The PI
controller constantly maintains the DC link supply
voltage. The single phase inverter converts this DC
voltage into AC voltage and feeds the load. The
simulation results are shown here. From the results the
voltage stress across the switch can be analysed that
regenerative snubber reduces the voltage stress. The
results are given below.
Fig 7 DC output voltage
The dual switch Z-Source Converter gives 48V is
shown in Fig 7. The DC input voltage gets boosted
into 48V and this voltage gets maintained using PI
controller. Here the proposed converter has no reverse
recovery of current since duty cycle can be controlled.
Fig 4 Mode I operation
Fig 5 Mode II operation
8. DESIGN OF THE CONVERTER
Table 1 Design of the Converter
Parameters
Voltage gain
Input DC voltage
Capacitor voltage in impedance
circuit
Output voltage
Magnetizing inductance
Capacitor in impedance circuit
Inductance in impedance circuit
Stray capacitor
DC link capacitor
Value
3
16V
12.75V
48V
15
150
1
50
50
9. SIMULATION RESULTS
The dual switch Z-Source Converter is connected with
the single phase full bridge inverter feeding resistive
load. The input DC voltage gets converted into AC
voltage. The voltage across the switch during turn off
Int J Adv Engg Tech/Vol. VII/Issue II/April-June,2016/
Fig 8 AC output voltage
Fig 9 Voltage across the switch without snubber
P.R.Sivaraman et al., International Journal of Advanced Engineering Technology
E-ISSN 0976-3945
Table 2 Comparison of simulation and hardware results
Parameters
Input voltage
DC output voltage
AC output voltage
Voltage gain
Fig 10 Voltage across the switch with snubber
The dual switch Z-Source Converter with regenerative
snubber reduces the stress to 32V is shown in Fig
10.The snubber not only reduces stress also recycles
the leakage inductance to the as an input. This
improves the reliable operation of the dual switch ZSource Converter.
The resistor 80 ohm is connected as a load. The
proposed system has the closed loop operation using
Proportional Integral controller reduces steady state
error. The reference voltage is set as 48V since the
system is single phase operation.
10. HARDWARE RESULTS
Fig 11 Experimental setup of the system
The proposed system has been implemented in
hardware is shown in Fig 11. The results of the kit are
also shown below and the comparison of simulation
and hardware results were also compared in table 2.
Fig 11 DC input voltage
Fig 12 DC output voltage
Fig 13 AC output voltage
Int J Adv Engg Tech/Vol. VII/Issue II/April-June,2016/
Simulation results
16 V
48 V
48 V
3
Hardware results
16V
48.1 V
44.8 V
3
11. CONCLUSION
This project has proposed a dual switch Z-Source
Converter to achieve a highly boosted DC output
voltage. Then regenerative snubber circuit is used not
only to reduce voltage stress also it recycles the leakage
inductance and give this as supply to the switch. This
efficient DC output voltage is converted into AC
voltage using full bridge inverter circuit and it is
connected with capacitor DC link. The closed loop
operation does the voltage regulation in order to avoid
damage of the load. The proposed topology can be used
to any AC load applications like domestic appliances,
Induction Motor, computer peripherals.
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