IRJET- Design and Implementation of Converters using MPPT in an Eco Vehicle

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 03 | Mar 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 1576
DESIGN AND IMPLEMENTATION OF CONVERTERS USING MPPT IN AN
ECO VECHCLE
S. Muralidharan1, U. Nikeshkumar2, V. Nithya3, S. Udhayakumar4, K. Elango5
1,2,3,4Student, Department of Electrical and Electronics Engineering, Valliammai Engineering College,
Kattankulathur, Tamil Nadu, India.
5Head of the Department, Department of Electrical and Electronics Engineering, Valliammai Engineering College,
Kattankulathur, Tamil Nadu, India.
---------------------------------------------------------------------***----------------------------------------------------------------------
Abstract - The photovoltaic (PV)systemsarefoundtobe the
best source employing conventional source of energy fromthe
sun. However these photovoltaic arrays do not deliver a
maximum power automatically and shows a non linear
behavior and hence it produces a non linear I-V curve due to
sunlight radiance and temperature. In order to overcome this
drawback a SEPIC converter whichregulatesthelinearoutput
is employed and we track the maximum power point obtained
by using perturb and observe (P&O) algorithms to obtain
maximum power. To control the converter topologies, fuzzy
logic control is used. For storing the obtained voltagefromthe
photo voltaic system we use a 48V battery. Thus the overall
efficiency and performance of the solar eco vehicle has been
improved.
Key Words: Photovoltaic system, Maximum power
point tracking, SEPIC converter, Fuzzy logic
controller.
1. INTRODUCTION
The rapid depletionofnonrenewableenergyresourcesis
the major problem nowadays. In addition to this, the
population is increasing at a greater extent which increases
the demand of electricity. Hence we use renewable energy
resources which are found as an effective alternative for the
conventional energy resources. One such example of such a
replacement is the solar eco vehicle. This vehicle uses
photovoltaic systems which absorbs the sunlight and
converts this to Direct Current (DC). This DC produces non
linear I-V characteristics due to sun radiance and
temperaturewhichvariesduetotime.Astheirradianceofthe
sun is more the temperature of the photovoltaic system
increases which reduces the overall efficiency of the solar
panel. If the irradiance of the sun reduces maximum power
cannot be obtained. This also reduces the efficiency of the
panel. Hence the panel efficiency has to be improved. This
drawback can be overcome by designing and employing
certain power electronic devices such as converter and
controlling circuits. The non linear power that is obtained as
output from the photovoltaic system, which is due to
irradiance of the sun and temperature changes is being
corrected by using a suitable converter. In case of a
photovoltaic system, the output varies with time. Hence the
output from the solar panel should be boosted or reduced in
order to obtain the desired output. If the desired output
voltage has to beincreased, weuse a buckconverterandifthe
desired output voltage has to be reduced we use a boost
converter. But the output voltage of a solar panel has to be
increased or reduced comparing the desired output voltage
with the present output voltage. For this reason we cannot
use a buckconverter ora boostconverter.Hencewerequirea
buck- boost converter with increases or reduces the output
voltage according to the desired voltage but this buck boost
converterhascertaindisadvantages.HenceaSEPICconverter
is being used for this operation. Thus a variable fluctuating
DC is being converted into stiff DC by using converters. But
still the I-V characteristics is non linear and hence we use
Maximum power point tracking technique, where the
maximum poweris being trackedand set as referencepower
which is being compared with the present power and
accordingly adjusted to produceasmoothI-Vcharacteristics.
This maximum power point tracking (MPPT) technique is
done with the help of perturb and observe algorithm. To
obtain maximum power the firing pulsesoftheconverterhas
to be controlled using a controller circuit. Here, fuzzy logic
controller is being employed.Hence the output voltageofthe
converter is being controlled with great accuracy by
controlling the firing pulses of the converter. Thus the
efficiencyofthephotovoltaic(PV)systemshasbeenincreased
due to the design of converters and controllers. Finally, the
obtained DC voltage is being stored in a battery for later use
of energy.
2. BLOCK DIAGRAM OF PROPOSED AREA
Fig -1: Block Diagram

3. ENERGY ABSORPTION AND CONVERSION
WORKING OF SEPIC CONVERTER
Fig – 2: Working of SEPIC Converter
To increase the overall efficiency of the photovoltaic(PV)
system we employ a SEPIC converter, because the output
voltage from the solar panel is fluctuating and variable DC
which cannot bestored in a battery.HencethisfluctuatingDC
has to be converted into stiff DC with the help of a DC-DC
converter. If the output voltage has to be increased, we use a
boostconverter else werequire buck converter. Inthecaseof
a photovoltaic system we sometimes need to increase or
reduce the output voltage, hence a buck boost converter can
be used. But buck boost converter has certain disadvantages
such as poor transient response, need of a filter in the input
side, high peak current etc. Thus we use a SEPIC converter
which can increase or lessen the output voltage of the
photovoltaic system. The block diagram ofa SEPIC converter
shows that it employs two inductors L1 and L2, three
capacitors Cin, C1 and C2, a switch S1, a diode D and a
resistiveload Rwhichareconnectedinseriesandparallel.The
capacitor Cin is used as a filter capacitor, C1 as coupling
capacitor and C2 as decoupling capacitor.
3.1 CASE 1: WHEN SWITCH S1 IS OPEN
When the switch S1 is open, input voltage flows through
inductors L1 and L2, capacitances Cin, C1andC2, Diode D1
and load R. The capacitances and inductances charges at this
case. Voltage flows through inductor L1, capacitor C1,
inductor L2, diode D1, capacitor C2 and load RL. This is the
voltage path when the switchS1 is open.Thisswitchcanbeof
any switching device, but in this case we use a MOSFET . The
main aim of using this SEPIC converter is to increase or
reduce the output voltage to achieve the desired output. This
is done by adjusting the pulse width modulation signals
which is applied to the switching device that is MOSFET. The
output voltage of the SEPIC converter is boosted by
increasing the ON time of the PWM signals fed to the
converter. And the output voltage of this converter can be
reduced by reducing the ON time and increasing the OFF
time.
Fig – 3: Circuit Diagram when switch S1 is open
3.1 CASE 2: WHEN SWITCH S1 IS CLOSED
In this case, when the switch S1 is closed there exists two
loops of operation, becausethecurrentflowsthroughthelow
impedance path and hence it passes through loop1 which is
indicated in green lines in thefigure.Onlytheleakagecurrent
flows throughtheloop2thatisthroughcapacitorC1,inductor
L2, capacitor C2, diode D1 and load RL which is indicated in
red lines. Only verylessvoltagepassesthroughtheload.Thus
the operation of a SEPIC converter is being discussed.
Fig - 4: Waveform of SEPIC Converter

The above graph shows the waveform of SEPIC converter
when the pulses are being applied. The voltage and current
characteristics with respect to time are being plotted
accordingly. Hence using SEPIC converter,thedesiredoutput
is being brought byvarying its firing pulses. Thus the output
which is obtained can beincreased ordecreasedaccordingto
the output from the photovoltaic module. This SEPIC
converter is fed with PWM signals by a controller.
4.MAXIMUMPOWERPOINTTRACKINGTECHNIQUE
The general output power-voltage (P-V) waveform of the
photovoltaic systemisbeingshownbelow.Fromthegraphwe
can infer that, the P-V characteristic is not linear due to solar
radiance and temperature. general the output current of PV
module is mainly depends on irradiation level, whereas, the
output voltage of PV module depends on temperature level.
Howeverthe power variationatdifferenttemperatureisvery
small, so only the irradiation variation is the main factor of
output power of PV array. In order to overcome this weuse a
maximum power point tracking technique. This technique
employs perturb and observe (P&O) algorithm for tracking
the maximum power point of the panel.
Fig – 5: General P-V Characteristics of PV panel
Fig - 6: P-V Characteristics of PV panel after implementing
MPPT technique
Thus using P&O algorithm, the maximum power point is set
as reference and the present power is being compared with
the reference and accordingly the reference voltage is being
adjusted. The flowchart of Perturb and Observe algorithm is
sketched as follows.
Fig - 7: P-V characteristics after employing MPPT
Technique in SEPIC converter topology
Thus by using perturb and absorb algorithm, we could
obtain the maximumpower pointtracking,whichproducesa
linear P-V output characteristic curve at all operating
conditions.
Fig – 8: Flowchart of Perturb and Observe algorithm
5. FUZZY LOGIC CONTROLLER
Fig – 9: Block diagram of fuzzy logic controller
Fuzzy logic controller is used to provide the Pulse width
modulated (PWM) signals to the SEPIC converter. If the ON

timeofthe PWM signal is increased,theoutputvoltagecanbe
boosted. The fuzzy logic controller can have multiple inputs
multiple outputs, Whereas P, PI or PID controllers have only
single input and single output. Hence for this reason fuzzy
logic converters are being used in the place of conventional
converter circuits. This controller can providemoreaccurate
control than other converters. The first process to be done is
fuzzification. Conversion of crisp inputs into fuzzy inputs is
called as fuzzification. This inputs are being compared with
the rules which are being set accordingly. Now the output
obtained is being defuzzified,as the output is to beconverted
again to crisp form. This output thus produced is being
compared with the reference carrier signal. This reference
carrier signal is fixed whereas the output waveform varies
with time. The amplitudes at the point of interfering of the
reference wave and output are being compared and the
required PWM signals are being obtained, which is used to
provided to the SEPIC converter to obtain the linear desired
output. This PWM signal can have more ON time or less ON
timeafter comparingthetwowaveforms.IftheONtimeofthe
PWM signals is more, the output voltage boosts up and if ON
time is less and OFF time of the PWM signal ismore, then the
output is reduced compared it the input to the SEPIC
converter. Thus the firing pulses of the SEPIC converter are
being varied to control its output voltage
Fig – 10: Block diagram of fuzzy logic controller for SEPIC
converter
The membership function conversion and the rules that
are to be formed by programming it in Embedded C during
hardware implementation of this project, whereas the rules
and membership function can directly set in the MATLAB
software during the software implementation. Hence fuzzy
logic controller proves to be a more efficient and accurate
way of controlling the SEPIC converter to obtain a overall
linear P-V characteristic curve from the output of the
photovoltaic module employed in the solar eco vehicle.
6. CONCLUSION
We have designed a more efficient SEPIC converter
employingmaximumpowerpointtracking(MPPT)algorithm
to obtainlinearP-Vcharacteristicsofthephotovoltaicmodule
and a fuzzy controller to generate the required pulse with
modulation (PWM) signals which is more efficient and
accurate is fed to the converter for varying its firing pulses
and the DC output from the converter is stored in a 48V
battery.
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