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