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Project Report on
PHOTOVOLTAIC CHARGE CONTROLLER
BACHELOR OF TECHNOLOGY
In
ELECTRICAL AND ELECTRONICS ENGINEERING
From
GLA INSTITUTE OF TECHNOLOGY AND MANAGEMENT
Submitted to: Project Guide:
Mr. Sanjay Maurya Mr. Subhash Chandra
Project incharge
Submitted By:
Akanksha
Sukriti Rao
Avinav Prince
Prashant Verma
ACKNOWLEDGEMENT
In preparing this report, we were in contact with many people,
academicians and practitioners. They have contributed towards my
understanding and thoughts. In particular, we wish to express my sincere
appreciation to my project guide, Mr Subhash Chandra, for
encouragement, guidance, critics, advice, information and motivation.
Without his continued support and interest, this thesis would not have
been the same as presented here.
I also thanks to all faculty members of electrical and electronics eng.
Dept. for their help and support.
My sincere appreciation also extends to all my colleagues, and others
who have provided assistance at various occasions.
ABSTRACT
Photovoltaic or in short term PV is one of the renewable energy resources
that recently has become broader in nowadays technology.
The demand or future work is looking for high efficiency,
more reliable and economical price PV charge controller which is come in
portable size has become very popular in PV system.
In general, PV system consists of a PV array, charge controller,
rechargeable battery and dc load. PV charge controller is very important in
PV system. This project aims at Charge Controller which reduces
complexity in the number of electronic components and increased
monitoring and regulative functions. This project disuses dc-dc boost
converter circuit which has been simulated using software Simulink. The
benefit of this project is an improvement of efficiency depend on duty
cycle and voltage change.
CONTENTS
1) Introduction
2) Boost converter
2.1 Introduction
2.2 Block Diagram
2.3 Working
2.4 Components Calculation
3) Simulation of Boost Converter
4) Mathematical Modelling of Boost Converter
5) Objectives of next semester
6) References
1. INTRODUCTION AND PURPOSE OF THE PROJECT
Photovoltaic or in short term PV is one of the renewable energy resources that
recently has become broader in nowadays technology. PV has many benefits
especially in environmental, economic and social.
In general, a PV system consists of a PV array which converts sunlight to direct-
current electricity, a control system which regulates battery charging and operation
of the load, energy storage in the form of secondary batteries and loads or
appliances. A charge controller is one of functional and reliable major components in
PV systems. A good, solid and reliable PV charge controller is a key component of any
PV battery charging system to achieve low cost and the benefit that user can get
from it.
The main function of a charge controller in a PV system is to regulate the
voltage and current from PV solar panels into a rechargeable battery. The minimum
function of a PV charge controller is to disconnect the array when the battery is fully
charged and keep the battery fully charged without damage. A charge controller is
important to prevent battery overcharging, excessive discharging, reverse current
flow at night and to protect the life of the batteries in a PV system.
Efficiency, size, and cost are the primary advantages of switching power
converters when compared to linear converters. Switching power converter
efficiencies can run between 70-80%, whereas linear converters are usually 30%
efficient. The DC-DC Switching Boost Converter is designed to provide an efficient
method of taking a given DC voltage supply and boosting it to a desired value.
2. BOOST CONVERTER
2.1 Introduction
The boost (or step-up converter) like the Buck converter, a capacitor and an inductor
with role of energy storing, and two complementary switches. In the case of the
boost converter, the output voltage is higher than the input voltage. The switches are
alternately opened and closed with at a rate of PWM switching frequency.
Fig. 1. The boost converter diagram
As long as transistor is ON, the diode is OFF, being reversed biased. The input voltage,
applied directly to inductance L, determines a linear rising current. When transistor is
OFF, the load is supplied by both input source and LC filter. The output that results is
a regulated voltage of higher magnitude than input voltage. The converter operation
will be analyzed according with the switches states.
2.2 Block Diagram
The basic building blocks of a boost converter circuit are shown in Fig. 1.
Voltage
Source
MagneticField Storage
Element
Switch Control
Switching
Element
Output
Rectifier and
The voltage source provides the input DC voltage to the switch control, and to the
magnetic field storage element. The switch control directs the action of the
switching element, while the output rectifier and filter deliver an acceptable DC
voltage to the output.
2.3 Working
The first time interval: The transistor is in ON state and diode is OFF.
Fig. 2. The equivalent circuit during the ON state of transistor and OFF state of diode
For this operation period, the output voltage uo and the current through the inductor
ILsatisfies the following equations:
dIL/ dt = E/L
duo/dt = -uo/RC
The second time period: the transistor is OFF and diode is ON
In the moment when the transistor switch in OFF state, the voltage across the
inductor will change the polarity and diode will switch in ON state. The equivalent
diagram of converter during this period is shown in the bellow figure:
Fig. 3. The equivalent circuit for OFF state of transistor and ON state of diode
For this operation period, the output voltage uo and the current through the inductor
IL satisfy the following equations:
dIL/ dt = E-uo/L
duo/dt = 1/C (IL- uo/R)
The third operation mode: The both transistor and diode are OFF
If the inductor current becomes zero before ending the diode conduction period,
both the transistor and the diode will be in OFF state. Due to the diode current
becomes zero, the diode will naturally close, and the output capacitor will discharge
on the load. This operation regime is called discontinuous current mode. The
equivalent diagram of this operation regime is shown below.
Fig. 12. The equivalent circuit with transistor and diode in OFF state
on
LPKL
t
IL
dt
diLV (1)
onsatin
Lon tL
VVI
(2)
off
LPKLL
t
IIL
dt
diLV
min (3)
(4)offinFout
LpkLoff tL
VVVII
(5)satin
inFout
off
on
VV
VVV
t
t
(min)
(min)
For this operation period, the output voltage uo and the current through the inductor
IL can be calculated from the following equations:
dIL/ dt = 0
duo/dt = -uo/RC
2.4 Component Calculations
In order for the circuit to function properly, the external components need to be
calculated carefully. When the switch is on, the voltage across the inductor is
and the current is given by
When the switch is off, the voltage across the inductor is given by
and the current is given by
VF is the forward voltage drop of the output rectifier and Vsat is the saturation voltage
of the output switch. Since ILon= ILoff, Eqs.(2) and (4) can be set equal to each other. This
operation gives a ratio for the on time over the off time. This ratio is given by
The values of Vin(miu), VF, Vout, and Vsat are 4.5 V, 0.8 V, 12V, and 0.3 V
respectively. The inverse of the frequency of operation yields the on time plus the off
time. The frequency of operation for this boost converter was chosen to be 62.5 kHz.
Therefore,
(6)sf
tt offon 161
(7)offon
on
tt
tD
(8)onT tC *)]5(^10*0.4[
(9)
1*2off
onoutpkswitcht
tII
(10)
pkswitch
satin
I
VVL
(min)min
(11)pkswitch
scI
R3.0
(12)onripple
outout t
V
IC
Equations (5) and (6) yield an on time of 9.834s and an off time of 6.166s. The
duty cycle is given by
The calculated duty cycle of this circuit is 61.5%. The value of the external timing
capacitor is calculated using the value of the timing capacitor is 390 pF. The peak current
through the switch is given by
and the minimum required inductance is given by
The calculated value of the minimum inductance is 80 H. The resistance required
for the current sense resister is given by
. The value of the output capacitor is given by
3. SIMULATION OF BOOST CONVERTER
Waveforms:
4. MATHEMATICAL MODELLING OF BOOST CONVERTER
(a) DUTY CYCLE IS CONSTANT
S.No Input voltage duty cycle output voltage
1 10 85 12.86
2 12 85 15.43
3 14 85 18
4 16 85 20.57
5 18 85 23.14
6 20 85 25.71
7 22 85 28.28
(b) OUTPUT VOLTAGE IS CONSTANT
Input voltage Duty cycle Output voltage
10 85.84 15
10.5 85.554 15
11 85.304 15
11.5 85.074 15
12 84.86 15
12.5 84.66 15
13 84.47 15
13.5 84.29 15
14 84.116 15
14.5 83.954 15
10 10.5 11 11.5 12 12.5 13 13.5 14 14.583
83.5
84
84.5
85
85.5
86Input voltage Vs Duty cycle
INPUT VOLTAGE
DU
TY C
YCLE
5. OBJECTIVES FOR NEXT SEMESTER
Till now we have done a detailed study about the boost converter which step ups the
input voltage. In the following semester our objective is to realize a charge controller.
As shown above in mathematical modeling we have manually changed the duty cycle
as and when the input voltage changes so that the output remains constant. In future
we plan on finding a suitable way so that the duty cycle changes on its value itself so
that we can achieve a suitable constant voltage output.
We also aim to study the buck and buck boost converter as these
3 topologies make the idea of charge controller.
6. References
1) Design and Modeling of Standalone Solar PhotovoltaicCharging System
By-Mathur B.L, Professor, Department of EEE, SSN College of Engineering
2) Modelling of DC-DC converters
Ovidiu Aurel Pop and Serban Lungu
Technical University of Cluj-Napoca
Romania
3) www.mathworks.in
4) Irving M. Gottlieb, Power Supplies, Switching Regulators, Inverters, &
Converters, New York: McGraw-Hill, 1993, pp. 132-141.
5) Paper on PHOTOVOLTAIC CHARGE CONTROLLER
By: NOOR JUWAINA AYUNI BT. MOHD