International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)
High-efficiency Step-Up Converter by using PV system with
Reduced Diode Stresses Sharing
V. Thirumurugan M.E., (PhD). 1, S.Sugumar B.E., (M.E). 2
1
AP, EEE, The Kavery Engineering College, Salem, Tamilnadu, India
PG Scholars, EEE, The Kavery Engineering College, Salem, Tamilnadu, India
2
Abstract- High-efficiency Step-Up Converter by using PV
system with Reduced Diode Stresses sharing is proposed in
this paper. Through employ of coupled inductor and
switched capacitor, the proposed converters attain high
step-up conversion ratio without operating at extreme duty
ratio. Due to reutilize of leakage energy, the efficiency is
developed and the large voltage spike on switch is
improved, This kinds a low-voltage-rated MOSFET with
low RDS(ON) can be implemented for decreases of
conduction losses .Now adding, the selection of diodes is
useful and inexpensive because all the reduced voltage
strains on diodes are the same. Finally, a 700 W prototype
circuit with 12 V input and 400 output V output is employed
to prove the performance, and the maximum efficiency is
99%.
Fig.1.Typical renewable energy system
II. P ROPOSED CONVERTERS AND OPERATING
P RINCIPLES
Keywords- Coupled inductor, Switched Capacitor, high
step-up converter.
The circuit configurations of the proposed converters
are shown in Fig. 2. The proposed converter I and
proposed converter II have same the number of
apparatuses, step-up gain and voltage stresses. The
proposed converter III is integrated and derived from the
both proposed converters I and II.
I. INTRODUCTION
Renewable energy systems commonly make low
Voltage output, hence, high step-up dc/dc converters
have been usually valued and working in many
renewable energy applications [1]-[5]. Such systems
transfer energy from renewable sources into electrical
energy, and convert low voltage into high voltage via a
step-up converter, which can convert energy into
electricity using a DC-Micro grid. Therefore, a high stepup converter achieves highly between the systems
because such system requires a suitably high step-up
conversion with high efficiency. Fig. 1 shows a typical
renewable energy system. Due to leakage inductance,
conventional step-up converters, such as the boost
converter and fly back converter, cannot attain a high
step-up conversion with high efficiency. So, various high
step-up converters with methods of coupled inductor and
switched capacitor, which have features of
leakage
energy reutilize, low voltage stress, and high efficiency
are proposed [6]-[10].
(a)
(b)
319
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)
(c)
Fig.2.The proposed step-up converters.
(b) Converter II.
(c) Converter III.
(a)
(a) Converter I.
The primary winding and secondary winding of
coupled inductor have Np turns and Ns turns respectively,
and n is equal to Ns/Np, which is defined as turns ratio
and can be controlled to extend step-up gain. In primary
side, Lm and Lkp denote the magnetizing inductor and
leakage inductor respectively, and the secondary leakage
inductor is Lks. The boosting capacitor and switched
capacitor are denoted as Cb and Cs, respectively. In the
circuit analysis, the simulation results of proposed
converters I and II are almost near apart from the voltage
on capacitors. The proposed converter III is the main
importance of operating analysis, which is operated in
continuous conduction mode (CCM).The key steady
waveform as well as operating modes of proposed
converter III, are plotted in Fig. 3 and Fig. 4 respectively.
(b)
(c)
(d)
Fig.3.Steady waveform of the proposed converter III in CCM.
(e)
320
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)
Mode VI [t5, t6]
At t=t5, the output diode Do activates to turn on, and
the output capacitor Co get replacement, as shown in Fig.
4(f). For the meantime, input voltage source Vi, coupled
inductor, switched capacitors Cs1 and Cs2 provide energy
with high voltage gain to output capacitor Co and load Ro.
III. STEADY -S TATE ANALYSIS
The transient characteristics of integrated circuit are
marginalized to make simpler the circuit performance
analysis of the proposed converter in CCM, and some
formulated assumptions are as follows:
(1) All of the components in the proposed converter
are ideal.
(2) Leakage inductors Lkp and Lks are ignored.
(3) Voltages on all capacitors are measured to be
constant because of substantially large
capacitance.
By applying the voltage-second balance to the
magnetizing inductor based on KVL, the voltage gains
and voltage stresses of proposed converters can be
calculated.
(f)
Fig.4.The operating modes of the proposed converter III. (a) Mode
I [to, t1]. (b) Mode II [t1, t2]. (c) Mode III [t2, t3]. (d) Mode IV [t3, t4].
(e) Mode V [t4, t5]. (f) Mode VI [t5, t6].
Mode I [t0, t1]
At t=t0, the power switch S starts to turn on, and
diodes Ds1 and Ds2keep on reversed-biased state, as
shown in Fig. 4(a). The magnetizing inductor Lm still
transfers energy to the boosting capacitors Cb1 and Cb2.
Also, the high voltage energy still provides to output
terminal
Mode II [t1, t2]
At t=t1, all semiconductor devices continue before
state, as shown in Fig. 4(b).The output capacitor Co
variations from discharging state to charging state, this
mode is related to before mode.
A. Voltage Gain
The voltage gains of proposed converters I and II are
the same and all of voltage gains can be given by
Mode III [t2, t3]
At t=t2, all diodes are reversed-biased state apart from
diode Ds2, as shown in Fig. 4(c).The magnetizing current
and primary leakage current increase linearly. The
switched capacitor Cs2 boosts the voltage from the
induced voltage of secondary winding and the boosting
capacitor Cb2, which kinds the switched capacitor
Cs2capable to have a high voltage.
MV ( I )  MV ( II ) 
MV ( III ) 
3  n(2  D)
1 D
2  n( D  1)
(1)
1 D
(2)
Equation (1) and (2) confirms that the proposed
converters possess high step-up voltage gains without an
extreme duty cycle. The curve of all the voltage gains
related to duty cycle lower than turns ratio n= 2, is shown
in Fig. 5.
Mode IV [t3, t4]
At t=t3, the diodesDs1 and Ds2 are forward-biased state,
as shown in Fig. 4(d).The switched capacitor Cs2arises to
boost the voltage from the induced voltage of secondary
winding, the boosting capacitor Cb1 and input voltage
source Vi, which kinds the switched capacitor Cs1capable
to have a high voltage.
B. Voltage Stress
The voltage stresses on semiconductor devices of
proposed converter I are equal to proposed converter II.
All of switch stresses can be given by
Mode V [t4, t5]
At t=t4, the power switch S activates to turn on, and
the diodes Ds1 and Ds2turn off certainly, as shown in Fig.
4(e). For the meantime, the primary and secondary
windings of coupled inductor are consistently connected
in series, and the magnetizing inductor Lm starts to
transfer energy to the boosting capacitors Cb1 and Cb2.
VS ( I )  VS ( II ) 
VS ( III ) 
321
Vi
Vo

1  D 2  n(1  D)
Vi
Vo

1  D 3  n( 2  D )
(4)
(3)
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)
Its converts the heat energy to electrical energy means
DC voltage. This electrical voltage and current are
viewed by both voltage and current measurement
separately. This electrical signal is given to DC – DC
converter. The MOSFET also connect to this section to
improve the efficiency of the converter. The converter
converts the low level signal to required level with pure
DC signal. The coupled inductor is used to increase the
voltage level and capacitor is mainly filtering the DC
signal. This pure DC signals are very high efficiency and
these are measured by both voltage and current
measurement and viewed by scope. The part of output
signals are given to fuzzy logic controller and rule
viewer. This section contains some standard reference
values and rules. The incoming output signal and
reference signal are compared and produce the difference
output is given to PWM generator. The PWM generator
is convert the output value of fuzzy controller to pulse
signal and given to MOSFET. Depending upon pulse
signal the MOSFET is switched the electrical signal and
the high efficiency of pure DC voltage. In this system is
closed loop system of step-up converter with fuzzy
controller.
Fig.5.The voltage gains versus duty cycle under n = 2.
Equations (3) and (4) approve that low-voltage-rated
MOSFET with low RDS(ON) can be implemented for
the proposed converters to decrease conduction losses.
All of diode stresses of any proposed converter are equal
to each other and can be given by
VD, all ( I )  VD, all ( II ) 
n 1
n 1
Vi 
Vo
1 D
2  n(1  D)
(5)
VD, all ( III ) 
n 1
n 1
Vi 
Vo (6)
1 D
3  n(2  D)
Product1
Product
Scope11
Ca2
Scope10
Discrete,
Ts = 5e-005 s.
Scope1
powergui
Equations (5) and (6) denote that all of diode stresses
of proposed converters are considerable lower than
output voltage, and the diode stresses of any proposed
converter get reduced and usual. The correlation between
all the comparative voltage stresses and the turns ratio n
lower than duty cycle D = 0.5 is showed in Fig. 6.
+v
-
Vo1
i
+
1
2
Parallel RLC Branch1
Io1
Ca3
g
PV System1
+v
-
D
???
Ca
ra1
S
Mosfet1
Vo
Scope
360
G
25
SVPWM Generator
T
T
Fuzzy Logic
Controller
with Ruleviewer
Pulses
Scope3
Scope4
Product2
Fig.7.Simulation model of step-up converter with fuzzy controller
V. S IMULATION RESULTS
A 700 W prototype of the proposed high step-up
converter III is verified. The electrical specifications are
Vi = 12 V, Vo = 400 V, fs = 45 kHz. The major
components have been selected as magnetizing inductors
Lm = 11µH, turns ratio n = 6.8, power switches
SisBUK965R8-100E, all diodes are MBR10200FCT,
capacitorCb1, Cb2 and Cs2= 22 µF, Cs1 = 56µF, input filter
capacitors = 2200µF * 2, output filter capacitor =82µF.
Fig.6.The relative voltage stresses versus turns ratio lower than D =
0.5.
IV. S IMULATION MODEL
The simulation model of step-up converter with fuzzy
controller as shown in fig.7 the two inputs like radiation
and temperature are given to solar PV system.
322
Scope12
+ i
-
-
Scope2
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)
Fig.8 shows the measured waveforms at full load
700W. Fig.6.4 (a) shows the PWM signals V gs and the
voltage stress on the power switch, as well as the current
through the primary leakage. The switch stress much
lower than output voltage (400V) show the voltage
stresses on all diodes and output voltage Vo, and all of
the diode stresses are properly 178V which are lower
than the half of output voltage (400V). From the
experimental results, the per voltage stress, reduced
voltage stresses step-up conversion are effectively
implemented.
From the proposed system, step-up converter without
fuzzy controller gives desired output ranges.
(a)
(b)
(a)
(c)
Fig.9.Output Waveform
VI. CONCLUSION
The conclusion of High-efficiency Step-Up Converter
by using PV system with Reduced Diode Stresses
Sharing is proposed in this paper. Through employ of
coupled inductor and switched capacitor, the proposed
converters attain high step-up conversion ratio without
operating at extreme duty ratio. Due to reutilize of
leakage energy, the efficiency is developed and the large
voltage spike on switch is improved, This kinds a lowvoltage-rated MOSFET with low RDS(ON) can be
implemented for decreases of conduction losses .Now
adding, the selection of diodes is useful and inexpensive
because all the reduced voltage strains on diodes are the
same. The derived converters have the advantages of
high voltage conversion ratio, low power switch voltage
strain, small input current ripple. The steady-state process
of the resultant converter is analyzed, and the circuit
performance is brief to explore its advantages in the highstep-up, high-output-voltage exchange systems. In
addition, the reutilize of leakage energy increases the
conversion efficiency.
(b)
(c)
Fig.8.The measured waveforms at full load 700 W
323
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)
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For the meantime, the voltage stress on the power
switch is controlled and much lower than the output
voltage (400 V). Finally a 12-V input and 400-V output
voltages is implement and test to show the efficiency via
MAT LAB simulation. Furthermore, the highest
efficiency is 99% at Po= 700 W. Thus, the proposed
converter is suitable for high step-up conversion
applications.
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