“EFFICIENT UTILIZATION OF RENEWABLE
ENERGY FOR MULTIPLE UTILITIES BY BUCKBOOST CONVERTER”
PROJECT REFERENCE NO. : 37S0438
COLLEGE
: S.G.BALEKUNDRI INSTITUTE OF TECHNOLOGY, BELGAUM
BRANCH
: ELECTRICAL AND ELECTRONICS ENGINEERING
GUIDE
: LALITHA DARBHA
STUDENTS : SHRIVATSAV. P. MADABAL
SNEHA. B. KARKI
SHRADHA. B. MATTIKATTI
VIDYA. V. HIREMATH
Keywords: Renewable energy, Buck-Boost.
Introduction:
At present in India 70% of the source for generation of power is coal. The generation is not
meeting the needs of all the consumers across the country. Renewable energy sources are
available abundantly in nature. Solar energy freely available in nature and a clean fuel can be
harnessed to produce electricity. The developments in solar technology are resulting in lower
payback periods of solar PV panels. Solar PV panels convert sunlight into electricity and
produce DC output power. Sunlight is available only during day time; hence it is necessary to
store the generated electric power in batteries for utilization when required. Conventional
process includes inversion, step up, transmission, step-down, rectification and filtration for
the utilisation of power. These steps can be eliminated by use of buck boost converter.
The power received from the sun is about 1.8X10^11 MW. This is almost 1000 times
greater than the power produced from all the sources used all around the world. If it is
possible to tap this energy effectively there would be no shortage of power in the world. At
the utility end many DC appliances work on different voltage levels. Buck boost converter
provides the voltage levels by stepping up/ down the available input as per the requirement.
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Some of the applications of buck boost converter are as follows:
Dc ceiling fan
Rated voltage = 12V
Rated power < 28W
Rated current = 2.0 -2.5A
Ac fan
Rated voltage = 120V
Rated power = 120W
Dc table fan
Rated voltage = 12V
DC LED bulb
Rated voltage = 12V
Rated power = 11W
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Radio
Rated voltage = 6V
Rated power = 4W
DC TV Rated voltage = 12V
Mobile
Rated voltage = 4.5V
Refrigerator
Voltage= 12/24V DC
Power rating = 45W
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Objectives:
India is expected to be the 2nd largest energy consumer by 2025. With this rapid increase in
the gap between demand and supply there exists a need for the development of new ways for
generation of power. In this proposal we aim to harness the solar power by PV panels stored
in battery. For DC power there is no device like transformer for step-up and step-down. Buck
boost converter facilitates variable DC output voltage for DC loads. This project aims to
design a Buck-Boost converter for multi-utility purpose using solar PV based renewable
source of energy. Application of buck-boost converter has not been explored in renewable
energy area. These circuits provide a wide range of output voltages that can be utilized for
huge number of low power applications. Thus thereby reducing the transmission and
distribution costs.
Methodology:
There are three types of converters:
1. Buck converter
2. Boost converter
3. Buck-boost converter
Buck Converter
Buck Converter is one in which the output voltage is less than the input/supply voltage. Buck
is a non isolated power topology also called as step down power storage.
Simulation of buck converter
Duty cycle=52%
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Working:
The basic operation of the buck converter has the current in an inductor controlled by two
switches, a transistor and a diode. Specifically, the switch and the diode have negligible
voltage drop when in on state and zero current flow when off state and the inductor has zero
series resistance
When switch is ON for 'DT' seconds, it is supplying current to the load, initially current flow
to the load is restricted. Diode 'D' becomes reverse bias, as energy is also being stored in
inductor ‘L’ and voltage across inductor Vdc − Vo which is positive so that inductor current
'IL' increases linearly, voltage across switch becomes zero.
When switch is OFF for '(1-D)T' seconds. Diode 'D' becomes forward bias and voltage
across inductor '-VO' which is negative so that inductor current 'IL' decreases linearly, voltage
across switch is Vdc .
Boost Converter
Boost Converter is one in which the output is more than the input/supply voltage. It is
also called as step up power storage.
Simulation of boost converter for output voltage of 24V in MATLAB
Duty cycle=52%, frequency=12 KHz, inductor=1mH
Working operation:
There are two modes of operation:
Mode 1: It begins when transistor is switched on at t=0, the input current rises and flows
through inductor L and transistor.
Mode 2: It begins when transistor is switched off at t= t1 , the current flowing through the
transistor would now flow through L, C, load and diode Dm .
Then with the decrease in the magnitude of inductor current, mode 1 repeats and the
cycle continues.
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Buck-Boost Converter
Buck-Boost is the one in which the buck as well as boost operation is possible i.e. the
input voltage can be varied from minimum value to a maximum value.
Simulation of buck boost converter for output voltage of 4.5V in MATLAB
Duty cycle=29%, frequency=20 KHz, inductor=1mH, capacitors = 47µF
Simulation of buck boost converter for output voltage of 32V in MATLAB
Duty cycle=75%, frequency=20 KHz, Inductor=1mH, capacitors = 47µF
Working operation:
There are two modes of operation in buck boost converter as in the buck converter
and the boost converter.
Mode 1: In this mode the transistor is turned on and diode is reverse biased, the input current
rises and flows through the inductor and transistor.
Mode 2: Transistor is switched off and the current which was flowing through inductor would
flow through capacitor, diode and the load. The energy stored in the inductor will be
transferred to load and the inductor current would fall until transistor is switched on again in
the next cycle. Then the cycle repeats. The output obtained by the buck boost converter has
the reverse polarity.
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Simulation results for buck boost converter for constant frequency of 20 kHz and
Inductance of 1mH
Output voltage
Pulse Width
(%)
Mode of
operation
4.5V
29%
Buck mode
6V
35%
Buck mode
24V
68%
Boost mode
32V
75%
Boost mode
Application
Mobile charger
Radio
24V dc motor
Printer
Firing Circuit
This is a very simple circuit utilizing a 555 timer IC to generate square wave of frequency
that can be adjusted by a potentiometer. With values given the frequency can be adjusted
from a few Hz to several KHz. To get very low frequencies replace the 0.01uF capacitor with
a higher value. The formula to calculate the frequency is given by:
f =
( R + R2 )
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The duty cycle is given by: %dutycycle = 100 * 1
0.69 * C * ( R1 + 2 * R2 )
R1 + 2 * R2
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PCB LAYOUTS OF CIRCUITS
The PCB layouts are designed in the copper connection software.
Buck circuit
Buck circuit PCB layout
Etched copper clad
Boost Circuit
Boost circuit PCB layout
Etched copper clad
Buck Boost Circuit
Buck boost circuit PCB layout
Etched copper clad
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Results:
Buck circuit
Hardware of buck circuit with output of 6V
Hardware output of Buck converter 6V
Hardware output of Buck converter 4.5V
The above figure shows the buck circuit hardware implementation. The output of circuit is
6V DC with an input of 12V DC. The MOSFET is triggered through pulses of 555 timer
circuit. The duty cycle is 68%,33% and the frequency is 12 kHz. The radio is run by the 6V
DC. Mobile charged with 4.5 V.
Boost circuit
Hardware of boost circuit with output of 17V
Hardware output of Boost converter 17.19V
The above figure shows the boost circuit hardware implementation. The output of circuit is
17.19 V DC with an input of 12V DC. The MOSFET is triggered through pulses of signal
generator. The duty cycle is 36% and the frequency is 100 kHz.
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Buck Boost circuit
Hardware of buck boost circuit with output of 20V
Hardware output of Buck Boost converter 20V
The above figure shows the Buck boost circuit hardware implementation. The output
of circuit is 20.1 V DC with an input of 12V DC. The MOSFET is triggered through pulses
of signal generator. The duty cycle is 68% and the frequency is 20 kHz.
Hardware of buck boost circuit with output of 7V
Hardware output of Buck Boost converter 7V
The above figure shows the Buck boost circuit hardware implementation. The output of
circuit is 7.5V DC with an input of 12V DC. The MOSFET is triggered through pulses of
signal generator. The duty cycle is 52% and the frequency is 12 kHz.
Conclusion:
In order to utilize the DC power directly available from the renewable sources needs step
down or step up as various applications require work at different voltage levels. There is
absence of a device like transformer incase of DC power, buck boost converter serves the
purpose. Here the voltages can be stepped up or stepped down depending on the requirement
by varying the gate pulse to power devices (MOSFET/IGBT). Keeping all the other circuit
parameters constant, by varying duty cycle and frequency, voltage variation for step down are
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demonstrated. The various circuits are simulated in MATLAB. The hardware implementation
for buck operation proves that DC-DC utilization can be done effectively by buck boost
converter.
Future Scope:
 The project can be expanded for buck- boost inverter applications where the bulky
transformer can be eliminated.
 The polarity reversal techniques can be adopted for positive output to meet the higher
voltage requirements for voltage ratings up to 110DC.
 Appliances requiring DC like LED bulbs, DC Motor based low power refrigerators /
pumps for air-conditioners / mixers can be developed and promoted such the effective
utilization of renewable energy is obtained.
 Battery can be eliminated and direct utilization of renewable energy can be explored.
 Harmonic analysis can be done to evaluate the performance of the device over longer
durations.
 Boost stage of buck boost circuit has to be further improved and tested for utilities
like 24V DC motor, 32 V for printer applications.
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