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Proposition and Performance Analysis of a DC/DC
Boost Converter
Abstract—A DC/DC boost converter is designed in this
paper, and its performance is analyzed subsequently. The
scenario of a hybrid energy plant is considered. Two power
sources are integrated by the boost converter to provide a higher
voltage in the DC bus. In simulation, two DC cells are used as
power source. Each of the DC cells is driven by a switching
circuit to form an individual boost cell. Orcad Capture 9.2 is used
as simulator with a computer having Core-i3 processor. Circuit
parameters like inductance, pulse voltage frequency and duty
cycle of the switching circuits etc. were varied to observe their
effect on efficiency. Finally MATLAB is used to observe the
efficiency in a 3D plot with respect to the change of duty cycle
and frequency of the pulse voltages.
Keywords—Duty cycle, Boost converter cell, Auxiliary circuit,
Switching, Efficiency, Root mean square (RMS), Maximum
voltage.
I. INTRODUCTION
As we have found our fossil fuels are inevitably shrinking,
we are left with choosing no option but clean energies [1].
Studies have found that clean energy will provide 30%-50% of
world energy by 2050 [2-3]. Contemporary clean energies
comprises with Fuel Cell (FC), Photovoltaic (PV), wind energy
etc. To integrate them, some conversion and some storage
elements are required. Though, batteries or super capacitors
can be used as storage element [4], it is found unlikely as cost
effective. Hybrid power conversion systems (PCS) have
created a good share of interest for engineers and scientists.
The diversely expanded power conditioners that include
DC/DC and DC/AC are essential components for clean energy
application. A conventional integrated power sources and their
conversion can be depicted as Figure 1 [5].
High frequency DC/DC converters, also known as switch
mode power suppliers (SMPS), are increasingly used in power
supply of computers and electric equipment [6]. They are
classified in four basic types according to their voltage
regulation and configurations: (i) Buck converter, (ii) Boost
converter, (iii) Buck-Boost converter, and (iv) Ĉuk converter
[6]. In this paper, we will concentrate on designing and
performance analysis of a DC/DC boost converter. The key
feature of the design is not having any auxiliary switching
circuit. Rong-Jong and Chung-You [7] proposed a boost
converter of two input power source having an auxiliary
switching circuit. Dong-Yun Lee [8] showed no conduction
loss on the main switch during the resonance of auxiliary cell.
However, by avoiding an auxiliary switching circuit, the
efficiency of a boost converter can still be consistent.
Figure 1: Integrated power sources and their conversion scheme.
II. BOOST CONVERTER
The output voltage of a boost converter is greater than input
voltage. Consider a circuit diagram like Figure 2(a). Here,
is
a pulse voltage to switch the MOSFET M. is the time period
of the pulse voltage. is portion of time cycle when
remains equal to a voltage required to turn on the MOSFET,
and for the time period of , the MOSFET is kept turned off as
remains 0(Figure 2(b)).
Md Mostofa Kamal Tareq
Engineering department
Incepta Vaccine Ltd.
Savar, Dhaka
Email:
mostofakamaltareq@gmail.com
Md. Ashraful Islam
Lecturer, Dept. of
Electrical and
Electronic Engineering
Leading University, Sylhet
Email:
ashrafulislam.eece@gmail.com
Hasib Ahmed Mazumder
MS in Information and
Communication technology,
IICT,
Bangladesh University of
Engineering and Technology, Dhaka.
Email:
mazumderhasib@gmail.com
Ashraful Islam
Department of EECE
Military Institute of Science and
Technology, Dhaka
Email: ashrafulislam90@yahoo.com
978-1-5386-0814-2/17/$31.00 ©2017 IEEE
IEEE International Conference on Power, Control, Signals and Instrumentation Engineering (ICPCSI-2017)
39
So, duty cycle
=
+
Figure 2(a): Single boost converter cell.
Figure 2(b): Time vs pulse voltage (VP) and time vs inductor current (IL)
The circuit operation can be separated into two phases:
Phase I:
From =0to = , the MOSFET is switched on, and input
current rises through the inductor . If the rise of the current
is ∆, then,
=∆
(1)
Where, ∆ = −
Phase II:
From =
to = +
, the MOSFET is switched off;
hence, the input current will fall to again.
, =(−
)
−
, =∆
−
(2)
Dividing equation (1) by equation (2):
=
−
,
+
=
−
, .
=
−
,
=
1−
As duty cycle is always less than 1,
is greater
than
.
Though a boost converter steps up the source voltage, it
conserves the power (P=VI), and thus, the output current is
lower than the source current. The inductor’s tendency to resist
the change of current is the prime driver of the boost converter.
When the MOSFET is turned on, the load resistor R is short
circuited, and the inductor stores energy as a magnetic field.
Subsequently, when the MOSFET is turned off, the inductor
itself acts as a source along with the DC source, and their
polarity become same. The magnetic field in the inductor, that
was stored previously, dissipates as it provides current to the
load R [7]. Now, if the period of
is small enough, i.e. the
switching cycle is fast enough to let the inductor not to
discharge fully, then the inductor will act as a source, and the
load will get a greater voltage across it than the source voltage.
The capacitors are used to reduce the ripple voltage. In
addition, diode prevents the capacitor from being discharged
when the MOSFET is on. The efficiency of the converter
depends on the value of inductor, and on the selection of pulse
voltage period and its duty cycle. If the pulse width is too long,
i.e. the MOSFET is turned on for a long time, the inductor will
cause the short circuit of the source which, in result, will
reduce the efficiency of the converter [9-10].
III. CIRCUIT DESCRIPTION
Proposed circuit, shown in Figure 3, has two boost cells
with two DC sources. Each cell has a switch of MOSFET
driven by pulse voltage sources: VP1 and VP2. There is a
phase angle of 180 degree between two switching voltages.
The frequency and magnitude of the switching voltages are
kept identical. If the duty cycle of both pulse voltages is less
than 50%, then there would be some period for which both
MOSFETs would be turned off. Thus, if the duty cycle of pulse
voltages is greater than 50%, then there would be some period
for which both MOSFETs would be turned on. For further
simulations, the duty cycle is kept 50%. In that case, each
MOSFET would be turned off while the other one is on.
Figure 3: Proposed DC/DC boost converter
There are auxiliary circuits across the MOSFETs to
increase the switching performance [11]. As no additional
switching circuit is incorporated for selecting the boost cells,
the selection of time period (), duty cycle () and time delay
of the pulse voltages (VP1 and VP2) deliberately performs this
job. The values of the parameters used in the proposed circuit
are given in Table 1.
C2
R10
R3
D5
R9
D4
VP1
D1
C3
V2
C5
0
D2
12
L3
R6
D3
R7
R2
VP2
RL
M1 R5
12
L1
C4
R1
M2
12
L2
R4
R8
C1
V1
Vs
Vout
MCR
12
L
Vp
D
IEEE International Conference on Power, Control, Signals and Instrumentation Engineering (ICPCSI-2017)
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TABLE I. CIRCUIT PARAMETERS AN D VALUES
Parameter name
Value
Voltage Source (V1, V2)
24 V (DC)
Pulse Voltage (VP1,
VP2)
1
0 V, PER=100us, PW
=
5
0us
Resistor (R1, R2)
1 mΩ
Resis
to
r(R3,R4)
100Ω
Resistor (R5, R7)
1kΩ
Resistor (R6, R8)
50Ω
Resistor (R9, R10)
1 mΩ
Resistor (RL)
30Ω
MOSFETs & Diodes
Ideal
Inductor (L1, L2, L3)
500uH
Capacitor (C1, C2)
0.68uF
Capacitor (C3, C4, C5)
100uF
IV. SIMULATION AND RESULTS
Figure 4 shows the RMS currents of two input sources and
the load. It is seen from the figure that the load current is
almost half of the source currents. As both source voltages are
24 Volt, the input current plots are almost identical.
Figure 4: RMS current through V1, V2 and RL vs time
Figure 5(a) shows the RMS voltage across the load resistor
RL. Value of RMS voltage depends on the inductance of L1,
L2 and L3. The change of RMS voltage with respect to the
value of L1, L2 and L3 is shown in Figure 5(b).
Figure 5(a): RMS voltage cross load resistance RL vs time
Figure 5(b): RMS voltage across RL vs inductance of L1, L2 and L3
Maximum voltage is obtained when the value of L1, L2 and
L3 is 30 uH. A plot of efficiency is given in the Figure 6. It is
worth mentioning that the plot of Figure 6 is for duty cycle of
both pulse voltages (VP1 and VP2)
=0.5 and time
period = 100 . In addition, the power of two pulse
voltages are not considered because of their negligible values.
Efficiency varies with the change of and .
Figure 6: Efficiency of the boost converter vs time
After several simulations by changing the value of
and , the values of efficiency are used in MATLAB to form
the 3D plot shown in Figure 7. The magnitude, and of
VP1 and VP2 are identical except the 180 degree phase shift in
a given simulation. It is explicit from the Figure 7 that the
efficiency increases as the duty cycle decreases, and the
efficiency increases with the increase of frequency.
IEEE International Conference on Power, Control, Signals and Instrumentation Engineering (ICPCSI-2017)
1.00
0.95
0.90
RMS(W(RL) / (ABS(W(V1))+ABS(W(V2))))
200ms 300ms 400ms 500ms
Time
100V
50V
0V
RMS(V(RL:2))
0s 250ms 500ms
Time
20A
10A
0A
-10A
RMS(I(R1)) RMS(I(R2)) RMS(I(RL))
0s 250ms 500ms
Time
41
Figure 7: Efficiency of the boost converter with respect to duty cycle and time
period of the pulse voltages
V. CONCLUSION
From the 3D plot in Figure 7, it is perceived that highest
efficiency is 0.98 when the time period and the duty cycle of
VP1 and VP2 are 25ms and 0.2 respectively. The effect of
changing the values of inductors on efficiency is still to
observe. In this paper, two power sources are dealt with.
Further study can be on successfully integrating three or more
DC power sources. Besides, the power sources are considered
equal, and the value is 24 Volt; however, the practical scenario
may not be like this. In that case, suitable value of the
inductors, duty cycle of the pulse voltages and frequency of the
pulse voltages would have to be evaluated to maximize the
efficiency. What is more, a clean energy cell may have an
internal resistance. Thus, as two ideal DC cells are used in the
proposed circuit, the internal resistance of the clean energy
cells has to be brought into consideration for a practical
scenario.
REFERENCES
[1] M. A. Munjer, M. F. Hossain and M. A. Alim, "Performance analysis of
grid connected PV array with H-bridge inverter controlled b y angular
modulation scheme," 2016 2nd International Conference on Electrical,
Computer & Telecommunication Engineering (ICECTE), Rajshahi,
2016, pp. 1-4.
[2] Bimal K. Bose, Life Fellow, IEEE “Power Electronics –Why the Field
is so Exciting” IEEE Power Electronics Society NEWSLETTER, Fourth
Quarter 2007 Pages 11-18.
[3] N. Mohan, W. P. Robbin, and T. Undeland; “Power Electronics:
Converters, Application.
[4] S. Al-Hallaj, “More than enviro-friendly: Renewable energy is also good
for the bottom line,” IEEE Power Energy Mag., vol. 2, no. 3, pp. 16–22,
May/Jun. 2004.
[5] L. Zhang, D. Xu, H. Li, G. Shen and M. Chen, "Three-phase interleaved
high step-up boost converter with voltage multiplier for fuel cell power
system," 2015 IEEE Energy Conversion Congress and Exposition
(ECCE), Montreal, QC, 2015, pp. 4804-4811.
[6] “Efficient Voltage Regulation of Modified Hybrid Dc-Dc Converter”
BY Mohammad Ali Azom Khan, Student ID-040406172P, BUET.
[7] “High-Efficiency DC–DC Converter With Two Input Power Sources”,
Rong- Jong Wai, Senior Member, IEEE, Chung-You Lin, and Bo-Han
Chen.
[8] Dong-Yun Lee, Min-Kwang Lee, Dong-Seok Hyun and I. Choy, "New
zero-current-transition PWM DC/DC converters without current stress,"
in IEEE Transactions on Power Electronics, vol. 18, no. 1, pp. 95-104,
Jan 2003.
[9] Changchien Shih-Kuen; Liang Tsorng-Juu; Chen Jiann-Fuh; Yang
Lung- Sheng; "Novel High Step Up DC–DC Converter for Fuel Cell
Energy Conversion System," Industrial Electronics, IEEE Transactions
on , vol.57, no.6, pp.2007-2017, June 2010.
[10] W Li; X He; "Review of Non-Isolated High Step-Up DC/DC Converters
in Photovoltaic Grid-Connected Applications," Industrial Electronics,
IEEE Transactions on, vol.PP, no.99, pp.1-1, 2010.
[11] T. Noguchi and M. Murata, "Switching loss reduction of MOSFET
using switching assist circuit," 2015 IEEE International Conference on
Industrial Technology (ICIT), Seville, 2015, pp. 1198-1204.
IEEE International Conference on Power, Control, Signals and Instrumentation Engineering (ICPCSI-2017)
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