Analysis of A PWM Boost Inverter . for Solar Home Application.

Analysis of A PWM Boost Inverter. for Solar Home Application.

ByRAFIA AKHTER

A thesis submitted to the Department of Electrical and Electronic EngineeringOf

Bangladesh University of Engineering and TechnologyIn fulfillment ofthe requirements for the degree of

MASTER OF SCIENCE IN ELECTRICAL AND ELECTRONiC ENGINEERING

DEPARTMENT OF ELECTRICAL AND ELECTRONIC ENGINEERINGBANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY

2008

•

Declaration

It is hereby declared that this thesis or any part of it has nor been submitted elsewhere forthe award of any degree or diploma.

--------~------( Rafia Akhter )

Dedication

To my beloved parents, husbandand only one son.

.01\ .. '1... •.

. .'

The thesis entitled" Analysis of A PWM Boost Inverter for Solar Home Application."Submitted by Rafia Akhter, Roll No. 040306l06P, Session April 2003 has beenaccepted as satisfactory in partial fulfillment of the requirements for the degree ofMASTER OF SCIENCE IN ELECTRICAL AND ELECTRONICS ENGINEERING

BOARD OF EXAMINERS

Member

Chairman

,

.o,~(Dr. Aminul Hoque) (Supervisor)ProfessorDepartment of Electrical andElectronics Engineering, BUETDhaka~ 1000, Bangladesh .

..,._~ ~_~r.:_r::-,-~_~(Ex- Officio)

(Dr. S.P. Majumder)ProfessorDepartment of Electrical andElectronics Engineering, BUETDhaka- 1000, Bangladesh.

I,

I

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Member ( External )C).j

Member

3.---- -----------------------;;:,ttf'u-o V(Dr. Mohammad Ali Choudhury)ProfessorDepartment of Electrical andElectronics Engineering, BUETDhaka- 1000, Ban ladesh.

0J!j{-4.-- - - - -- ~-.-~-.-w,(Dr. Kazi Khairul Islam)ProfessorDepartment of Electrical andElectronics Engineering, JUTGazipur

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Abstract

This thesis analyzes the procedural approach and benefits of applying

optimization techniques to the design of a boost dc-ac converter with solar cell as an

input. The analysis is performed based on the particular l2V DC to 230 V AC conversion

for home applications. A traditional design methodology is the use of buck inverter. One

of the characteristics of the most classical inverter is that it produces an AC output

instantaneous voltage always lower than the DC input voltage. Thus, if an output voltage

higher than the input one is needed, a boost dc-dc converter must be used between the

DC source and the inverter. It is less complex, lower cost and provides higher power

conversion efficiencies. This technique allows the P.W.M. voltage source inverter to

become a new feasible solution for solar home application.

V

Acknowledgements

I am very much grateful to the Almighty Allah for the successful completion ofthe work.

First of all, I would like to specially thank my supervisor Dr. Aminul Hoque,

Professor, Department of Electrical and Electronic Engineering, BUET, a brilliant

engineer and excellent human being, who lighted my way through the course of my

graduate work and life for the past two years. His enthusiasm, broad knowledge and

sharp thinking gained my most sincere admiration. His caring and understanding touched

me deeply.

I would also like to acknowledge and thank Dr. Mohammad Ali Choudhury,

Professor, Dept. of EEE, BUET, from whose teaching, discussions and contributions I

gained significant insight into the field of design optimization.

I also like to thank Dr. S.P. Majumder, Head and Professor, Dept. of EEE,

BUET, for his kind support for fulftlling my thesis.

I am also very much grate- full to Dr. Kazi Khairul Islam, for his great helpful

ness.

My sincere thanks to my friends Ms. Lutfa Akter, Assistant Professor, Dept. of

EEE, BUET, whose expertise in design optimization, hard work and patience made

possible the application of optimization techniques. It has been a pleasure to work with

them and I greatly enjoyed our friendship.

VI

(

ABSTRACT v

ACKNO WLED GEMENTS VI

TABLE 0 F CONTENTS ; VII

LIS T OFF IGURE S XIII

LIST OF TABLES XIV

CHAPTER 1 - INTRODUCTION...... 1

1.1 INTRODUCTION 1

1.2 LITERA TUR E RE VIEW 1

1.2.1 Stand alone solar electricity or Solar Home system 1

1.2.2 Solar System: How It Really Works Sun Light and Battery Bank! 2

1.2.3. Pulse Width Modulation (pWM) Basics 4

1.3. The Modern Switched-Mode Power Supply Topologies and Trends 5

1.3.1. The Switching Regulator Family 5

1.3.2. Analysis of converter waveforms 6

1.4 MOTIVATION AND OBJECTIVE 8

1.5 OUTLINE 9

VII

.-:j. .. ,

CHAPTER 2 - CONVERSION OF ELECTRIC ENERGY BY THE NEW PWM

BOOST INVERTER 10

2.1. Introduction 10

2.2. Solar Cells 10

2.2.1. Solar Electric systems 11

2.2.2. PV cell interconnection and module design 12

2.3. Stand Alone Solar Electric Systems 13

2.4. Voltage Source Inverter with Pulse Width Modulation 14

2.4.1. Voltage Source Inverter 14

2.4.2. Freewheeling diode 18

2.5. Switching mode regulator 19

2.5.1. Buck regulator 19

2.5.2. Boost regulator 21

2.5.3. Buck-boost regulator ; 23

2.5.4. Cuk Regulator 24

2.5.5. Converter Comparison 26

2.6. Converter interface of pv panels 26

2.6.1. Single DC String, Single DC-AC Inverter 27

2.6.2. Individual DC-AC Inverters per Panel (Module Integrated

Converters) 28

2.6.3. Multi-converter strings-panel integrated dc-dc, string dc-dc 28

VIII

~.

f::;',

2.7. Batteries Used in PV Systems 28

2.8. PWM Control. 29

2.8.1. Principle 29

2.8.2. Generation 29

2.8.2.1. Intersective .............................•......................................... 30

2.8.3 PWM Methods 31

2.8.4. Objective of PWM 32

2.8.5. Disadvantage of PWM 32

2.9. The conventional VSI. 33

2.9.1.Proposed Boost Inverter 34

2.9.1.1. The New Inverter and Principle ofOperation 34

2.10. Boost inverter circuit 36

2.10.1. Circuit operation 37

CHAPTER 3 - SIMULATION AND EXPERIMENTAL RESULTS 40

3.1. System description 40

3.2. The circuit description for the proposed boost inverter 41

3.2.1. Control design methodology 41

3.2.2. Selection of control parameters .41

IX

,,' ..

3.3 Simulation and experiment .42

3.3.1. The simulation and experimental results .42

3.3.1.1. Variation of output with load 150 and 500 ohm 48

3.3.2. Efficiency of Conversion 50

3.3.3. Simulation results with practical switches 51

3.3.3.1. The simulation and experimental results 51

3.4. Variation of Output 57

3.4.1. Variation in tabular form 56

3.4.2. Variation by graphical form 60

3.4.2.1. Variation by Modulation Index 60

3.4.2.2. Variation by modulating frequency ......•.•.............. 64

3.4.2.3. Variation by Boost stage 66

CHAPTER 4 - CONCLUSION 69

4.1. GENERAL••.•.•.••••••.••••••••••••••••••••••.•.••••..••••••••••.••••••••••••••••••..••••.••.••• 69

4.2. FUTUREWORKS .••..•••••••••••••••••••••••••••••••••.•••••••••.••.••.••••••••••••••••••••.•• 71

REFARENCES 72

GLOSSARY 76

x

LIST OF FIGURES

Figure. 2.1: Conversion of dc to ac 10

Figure. 2.2 Solar Cell.. 11

Figure. 2.3: Cells in series and in parallel. .12

Figure. 2.4. Single-phase voltage source converter. 15

Figure 2.5: Gate pulse input signal, and ac voltage and current outputs of a

pulse width modulation (PWM) converter. 16

Figure 2.6: Pulse width modulation (PWM) signals 17

Figure 2.7: Freewheeling diode operation 18

Fig. 2.8: Buck Converter. 19

Fig. 2.9: Voltage and current changes 20

Fig. 2.10: Boost Converter Circuit 21

Fig. 2.11: Voltage and current waveforms (Boost Converter) 22

Fig. 2.12: schematic for buck-boost converter. 23

. XI

Fig. 2.13: Waveforms for buck-boost converter 23

Fig. 2.14: CUK Converter 24

Fig. 2.15: CUK "ON-STATE" 25

Fig. 2.16: CUK "OFF-STATE" ; 25I

I

Fig. 2.17: Comparison of Voltage ratio ...............................•........... 26

Figure. 2.18: Comparison ofthree grid connected PV inverter

topologies 27

Figure.2.19: Pulse width modulation 29

Figure.2.20 :sguare wave, showing the definitions of Ymin, Ymax 29

Figure.2.21: A simple method to generate the PWM pulse train 31

Figure. 2.22: The conventional Voltage source inverter or buck inverter.

....................................................................... 33

Figure. 2.23: Circuit used to generate an AC voltage larger than DC input

voltage .33

Figure. 2.24: Principle of boost inverter 35

Figure. 2.25: The proposed Boost Inverter 36

XII

Figure. 2.26: Equivalent circuit for the boost inverter. .37

Figure. 2.27a: Mode I: Sl is closed and S2 is open 37

Figure. 2.27b: Mode 2: Sl is open and S2 is closed 38

Figure. 3.1: Conversion of solar cell to home application .40

Figure. 3.2: Boost Inverter using switches .42

Figure. 3.3 Control circuit .43

Figure. 3.4: Pulse width modulated signal. .44

Figure. 3.5: Output wave shapes of Sl and S2 .44

Figure. 3.6: Output voltage Across C2 45

Figure. 3.7: Output voltage Across C 1. .45

Figure. 3.8: Output voltage Across both cl and c2 .46

Figure. 3.9: Output voltage at load 250 Ohm, time t=84.1 ms,Vout= 22Vac .46

Figure. 3.10: Current for Rload= 250 Ohm, At time t= 83.67m, 0.9 A .... .47

XlII

- .'f'-

Figure. 3.11: Output voltage Across C2,Cl and for load 250 Ohm .47

Figure. 3.12: Vout=220.51 Vac at time, t=83.67 ms, Rload=150 ohm .. .48

Figure. 3.13: Current for Rload= 150 Ohm, Attime t= 83.67m, 1.47 A ... .48

Figure. 3.14: Vout = 228 V ac at time, t=84 ms, Rload=500 ohm .49

Figure. 3.15: Current for Rload= 500 Ohm, At time t= 83.67m, 0.45 A ... .49

Figure. 3.16: Output voltage at various load 50

Figure.3.17 : voltage gain at various load 50

Figure. 3.18: Boost Inverter using practical switches 52

Figure. 3.19: Control circuit 53

Figure. 3.20: Vout = 228 V ac at Rload=300 ohm 54

Figure. 3.21: lout = 0.76A ac at Rload=300 ohm 54

Figure. 3.22: Pout = 173.28 Watt 55

Figure. 3.23:Iin = lOA 55

Figure. 3.24: Pin = 178. 86Watt 56

XIV

Figure. 3.25: Variation of voltage gain with duty cycle 58

Figure. 3.26: Variation of output voltage with modulation index 59

Figure. 3.27: Pulse width modulated signal for m=I1.. 60

Figure. 3.28: Pulse width modulated signal for m=10 61



Figure. 3.31 : Variation of output modulating frequency, f= 50 Hz 64

Figure. 3.32: Variation of output modulating frequency, f= 60 Hz 64



Figure. 3.35: Variation of output by Boost stage, duty cycle =0.95 66


xv

Figure. 3.37: Variation of output by Boost stage, duty cycle =0.75"." ...67


Figure. 3.39: Variation of output by Boost stage, duty cycle =0.55"." ...68


LIST OF TABLES

Table: 2.1 How a Standard Grid-Tied* Solar System Works 14

Table: 3.1 Output Power at various load 50

Table: 3.2 Variation of Boost stage 57

Table: 3.3 Variation of modulation index 58

Table: 3.4 Variation of input freq .,59

XVI

/

Chapter 1Introduction

1.1. Introduction

Photovoltaic cells produce DC power over a wide voltage range depending on the

amount of sunlight and ambient temperature. A minimum DC voltage is required to

directly convert this DC voltage to a standard 230 Volts AC and to do so without the

use of any transformer. An addition of a transformer decreases power conversion

efficiency and adds to the weight and overall inverter or system costs. In our thesis,

our requirement is 230 V for residential use i.e. for Solar Home Application(SHS).

For this, in this thesis we proposed a new voltage source inverter which is less

complexive, lower cost and has higher power conversion efficiencies.

1.2. Literature Review

In this section a literature review, on the basic operation of the solar cells, converters

and the control techniques most commonly used is provided.

1.2.1 Stand-alone solar electricity or Solar Home Systems

A means to supply remote areas with electrical energy are Solar Home Systems

(SHS). Apart from its ecological advantages in many cases this option is also the

most economic way to electrify rural areas, especially when consumption is low and

grid extension would be long. But even this most economic way has often a price that

is too high for allowing wide spread ofSHS [I].

Stand-alone solar electricity systems or solar home systems are used when no grid

electricity is available. A battery is needed to ensure the availability of electricity at

night or at periods with little bright sunlight. Solar Home Systems are often used to

cover the electricity needs of a household. Small systems (commercially available as

a SHS kit) cover the most basic needs (lighting and sometimes TV or radio), larger

systems can also power a water pump, wireless phone, refrigerator, electric tools

(drill, sewing machine, etc) and a VCR [2-5].

The system consists of:

.:. a solar panel,

.:. a control unit,

.:. battery storage,

.:. cables,

.:. the electric load and

.:. a support structure.

1.2.2. Solar System

Solar Cells

Solar cells receive the sun's energy and change it to electricity. Inside a solar panel,

each cell contains silicon, an element found in sand that absorbs sunlight. The energy

in this absorbed light produces a small electrical current. Metal grids around the solar

cells direct the currents into wires that lead to the power controls.

2

Solar Panels

The solar array is comprised of one or more solar PY modules (solar panels) which

convert sunlight into clean solar electricity. PY is short for Photo voltaics which

means electricity from light. The solar modules need to be mounted facing the sun

and avoiding shade for best results.

Charge Controller

The main function of a charge controller is to prevent over charging the batteries, as

well as keeping electrical storage in the batteries from discharging to the solar

modules at night.

Batteries

The batteries store the solar power generated and delivers the power as needed. The

battery bank consists of one or more solar deep-cycle type batteries. Depending on

the current and voltages for certain applications, the batteries are wired in series

and/or parallel.

Inverter

The Inverter changes the DC current stored in the batteries into usable AC current

which is the most common type used by most household appliances and lighting.

Wiring

Selecting the correct sIze and type of wire will enhance the performance and

reliability of these system. The size of the wire must be large enough to carry the

maximum current expected without undue voltage losses.

Loads

The appliances and devices (such as TV's, computers, lights, water pumps etc.) thatconsume electrical power are called loads.

3

1.2.3. Pulse Width Modulation (PWM) Basics

There are many forms of modulation used for communicating information. When a

high frequency signal has amplitude varied in response to a lower frequency signal

we have AM (amplitude modulation). When the signal frequency is varied in

response to the modulating signal we have FM (frequency modulation). These signals

are used for radio modulation because the high frequency carrier signal is needed for

efficient radiation of the signal. When communication by pulses was introduced, the

amplitude, frequency and pulse width become possible modulation options. In many

power electronic converters where the output voltage can be one of two values the

only option is modulation of average conduction time [6].

Linear Modulation: The simplest modulation to interpret is where the average ON

time of the pulses varies proportionally with the modulating signal. The advantage of

linear processing for this application lies in the ease of de-modulation. The

modulating signal can be recovered from the PWM by low pass filtering.

Triangular PWM: The simplest analog form of generating fixed frequency PWM is

by comparison with a linear slope waveform such as a triangular wave. Here the

output signal goes high when the sine wave is higher than the triangular wave. This is

implemented using a comparator whose output voltage goes to a logic HIGH when

the input is greater than the other [7-9].

Regular Sampled PWM: The Triangular carrier PWM generates a switching edge at

the instant of crossing of the sine wave and the triangle. This is an easy scheme to

implement using analog electronics but suffers the imprecision and drifts of all analog

computation, as well as, having difficulties of generating multiple edges when the

signal has even a small added noise. Many modulators are now implemented digitally

but there is difficulty in computing the precise intercept of the modulating wave and

the carrier. Regular sampled PWM makes the width of the pulse proportional to the

value of the modulating signal at the beginning of the carrier period.

4

There are many ways to generate a Pulse Width Modulated signal other than fixed

frequency sine saw tooth. For three phase systems the modulation of a Voltage

Source Inverter can generate a PWM signal for each phase leg by comparison of the

desired output voltage waveform for each phase with the same triangular wave. One

alternative which is easier to implement in a computer and gives a larger modulation

depth is using space vector modulation (see page 31).

1.3. The Modern Switched-Mode Power Supply Topologies and Trends

1.3.1. The Switching Regulator Family

A DC-to-DC converter is a device that accepts a DC input voltage and produces a DC

output voltage. Typically the output produced is at a different voltage level than the

input. In addition, DC-to-DC converters are used to provide noise isolation, power

bus regulation, etc [I 0-1 I].

DC-DC power converters are employed in a variety of applications, including power

supplies for personal computers, office equipment, spacecraft power systems, laptop

computers, and telecommunications equipment, as well as DC motor drives. The

input to a DC-DC converter is an unregulated dc voltage. The converter produces

regulated output voltage ,having a magnitude (and possibly polarity) that differs from

the input. For example, in a computer off-line power supply, the 120 V or 240 V ac

utility voltage is rectified, producing a DC voltage of approximately 170 V or 340 V,

respectively. A dc-dc converter then reduces the voltage to the regulated 5 V 3.3 V

required by the processor rcs. High efficiency is invariably required, since cooling of

inefficient power converters is difficult and expensive. The ideal DC-DC converter

exhibits 100% efficiency; in practice, efficiencies of 70% to 95% are typically

obtained. This is achieved using switched-mode,. or chopper, circuits whose elements

dissipate negligible power. Pulse-width modulation (PWM) allows control and

5

regulation of the output voltage. This approach is also employed in applications

involving alternating current, including high-efficiency DC-AC power converters

(inverters and power amplifiers), AC-AC power converters, and some AC-AC power

converters (low-harmonic rectifiers).

1.3.2. Analysis of Converter Waveforms

Under steady-state conditions, the voltage and current waveforms of a DC-DC

converter can be found by uses of two basic circuit analysis principles. The principle

of inductor volt-second balance states that the average value, or DC component, of

voltage applied across an ideal inductor winding must be zero. This principle also

applies to each winding of a transformer or other multiple winding magnetic devices.

Its dual, the principle of capacitor amp-second or charge balance, states that the

average current that flows through an ideal capacitor must be zero. Hence, to

determine the voltages and currents of DC-DC converters operating in periodic steady

state, one averages the inductor current and capacitor voltage waveforms over one

switching period, and equates the results to zero. The inductor currents and capacitor

voltages contain dc components, plus switching ripple at the switching frequency and

its harmonics. In most well designed converters, the switching ripple is small in

magnitude compared to the DC components. For inductor currents, a typical value of

switching ripple at maximum load is 10% to 20% of the DC component of current.

For an output capacitor voltage, the switching ripple is typically required to be much

less than I% of the DC output voltage. In both cases, the ripple magnitude is small

compared with the dc component, and can be ignored.

Some of the popular DC-to-DC converter topologies are:

I. Buck Converter/ Step down converter.

2. Boost Converter/ Step up converter.

3. Buck-Boost Converter/ Step up-down converter.

4. Cuk Converter

6

Buck Converter/ Step down converter- The buck converter, also known as the step-

down converter, is a switching converter that has the five basic components, namely

a power semiconductor switch, a diode, an inductor, a capacitor and a PWM

controller. This converter produces an output voltage LOWER than the source. Here,

V(") tem-=-Vin T

and defining "duty ratio" as

tD = ..2!!..T

the voltage relationship becomes Vo=D Vin • Since the circuit is lossless and the input

and output powers must match on the average Vo* 10 = Vin* lin' Thus the average

input and output current must satisfy lin =D 10 These relations are based on the

assumption that the inductor current does not reach zero (continuous conduction

mode).

Boost Converter/ Step up converter- The boost converter, also known as the step-

up converter, is another switching converter that has the same components as the

buck converter, but this converter produces an output voltage greater than the source.

The ideal boost converter has the five basic components, namely a power

semiconductor switch, a diode, an inductor, a capacitor and a PWM controller. The

placement of the inductor, the switch and the diode in the boost converter is different

from that of the buck converter. Here,

Va T I- =-- =Vin t~O' (1- D)

Since the duty ratio "D" is between 0 and 1 the output voltage must always be higher

than the input voltage in magnitude.

7

Buck-Boost Converter/ Step up-down converter- Here the output voltage may be.

higher or lower than the source depending to the value ofD. The circuit components

are same. Here,

Vo IJ-~----Vi;.; (1 - D)

Since the duty ratio "D" is between 0 and I the output voltage can vary between

lower or higher than the input voltage in magnitude. The negative sign indicates a

reversal of sense of the output voltage.

Cuk Converter- The buck, boost and buck-boost converters all transferred energy

between input and output using the inductor, analysis is based of voltage balance

across the inductor. The CUK converter uses capacitive energy transfer and analysis

is based on current balance of the capacitor. Here,

Va D-~----ViII (l - D)

Thus the voltage ratio is the same as the buck-boost converter.

1.4. Motivation and Objective

The design of a power electronics system involves a large number of design variables

and the application of knowledge from several different engineering fields (electrical,

magnetic, thermal, solar and mechanical). In order to simplifY the design problem,

traditional design procedures fix a subset of the design variables and introduce

assumptions (simplifications) based on the designer's understanding of the problem.

These simplifications allow an initial design to be obtained in a reasonable amount of

8

time, but further iterations through hardware prototype testing are usually required.

The ability and expertise of the designer usually leads to good and optimum design.

The aim of this work is to design and propose a new voltage source inverter (VSI)

referred to as a boost inverter or boost dc-ac converter. The main attribute of the new

inverter topology is the fact that it generates an ac output voltage larger than the dc

input one, depending on the instantaneous duty cycle. This property is not found in

the classical VSI, which produces an ac output instantaneous voltage always lower

than the dc input one. The new inverter is intended to be used whenever an ac voltage

larger than the dc link voltage is needed, with no need of a second power conversion

stage. Here as input, PV cell is used.

1.5. Outline

The proposed VSI consist. of a boost-regulator, four switches with eight diodes; dc

filter capacitor and a load. These converters will produce a DC - biased sine wave

output, so that each source only produces a unipolar voltage. The modulation of each

converter will be 180 degrees out of phase with the other, which maximizes the

voltage excursion across the load. The load will be connected differentially across the

converters. The values of series inductor and capacitor will be so chosen as to

resonate at supply frequency. A proper switching scheme will be developed and the

duty cycle of the switching pulse will be modulated over the period of main supply

voltage. The proposed inverter circuit will be modeled mathematically and simulation

will be carried out to reveal the influence of input resonating series inductor-

capacitor and switching frequency on input. The information thus obtained will be

used for design and finally comparison will be made with the voltage source inverter

generally used at present.

9

Chapter 2 I

IIConversion of Electric Energy by the new PWM

Boost Inverter

I2.1. Introduction

The electricity produced by solar cells is direct current (DC), so it cannot be used in the

home as it is. For this reason, an inverter is installed in the solar system to carry out the

conversion of the generated direct current to alternating current (AC) for use in the home.

'11.,

Generated inStack (DC)

Inverter

/\vSupplied toHome (AC)

Figure. 2.1 : Conversion of dc to ac

In the inverter, the direct current generated in the stack is converted as follows: square

wave ---> step-up ---> modulation/rectification ---> corrugation and is finally synchronized

with the alternating current used in the household, before being supplied to the home.

2.2. Solar Cells

Solar cells receive the sun's energy and change it to electricity. Inside a solar panel, each

cell contains silicon, an element found in sand that absorbs sunlight. The energy in this

10

absorbed light produces a small electrical current. Metal grids around the solar cells

direct the currents into wires that lead to the power controls.

Figure. 2.2 Solar Panel

2.2.1. Solar Electric Systems:

Solar energy systems consist of five major parts. These are,

I. The sun: Sunny days and cloudy days will produce power in a solar electric

system. Light rays from the sun - visible light and invisible rays, both help to

produce electricity in the panels.

2. The power producing mechanism: This consists of the solar electric panels.

These panels are assembled from solar cells. Each cell will produce electric

power when exposed to sunlight. These cells are manufactured in a high-tech

process similar to that which is used to make computer chips. Solar electricity

was developed in the 1950's and has been perfected since then. Present solar

panels have no moving parts, are very reliable, and have a long life.

3. The roof mounting structure: This consists of aluminum and stainless steel

units which are used to mount the system on the roof of home.

4. The inverter: Solar cells produce DC (direct current), which is similar to that

produced by a car battery or flashlight battery. The electrical inverter, through

electronic circuits, produces the AC (alternating current) power which is used

by appliances and lighting fixtures. The inverter makes the power useful by

producing AC power to the standards of our local power.

II

5. The wiring: This will be connected to the load center (circuit breaker box or

electrical panel) of home. The solar electric system, when installed this way,

can be thought of as a home appliance which produces power, rather that one

which uses power.

2.2.2. PV Cell interconnection and Module Design

Solar cells are rarely used individually. Rather, cells with similar characteristics are

connected and encapsulated to form modules (arrays) which, in turn, are the basic

building blocks of solar arrays.

As maximum voltage from a single silicon cell is only about 600 mY, cells are connected

in series to obtain the desired voltage. Usually about 36 cells are used for a nominal 12 V

charging system.

Under peak sunlight (I W/m2) the maximum current delivered by a cell is approximately

30 mA/cm2• Cells are therefore paralleled to obtain the desired current.

Figure. 2.3: Cells in series and in parallel.

12

A typical 36 cell module based on screen printed silicon cell technology has the cells

series connected to suit the charging of 12 volt battery [12].

The typical characteristics for each cell would be:

Yoc = 600 mY (250 C)

Isc = 3.0 AmpsYmp = 500 mY (250 C)

Area = 100 cm2

Therefore 36 cells in series give:

Yoc = 21.6 Yolts (250 C)Isc = 3.0 Amps

Ymp = 18 Volts (250 C)

Imp = 2.7 Amps

2.3. Stand Alone Solar Electric Systems

Stand-Alone solar electric systems operate on the same basic principles as grid-tied with

battery back-up systems, however, instead of tying into the local utility they function

independently from the grid. They are used for properties where utility power is not

available, or very costly. A stand-alone system utilizes a battery bank to store the energy

produced by the modules, allowing one to draw electricity even when the modules are not

receiving energy from the sun. After being stored in the batteries, the DC power flows to

the inverter where it is converted to AC electricity for use in home [4].

13

Table: 2.1 How a Standard Grid-Tied Solar System Works:

PHASE IABSORB

PHASE 2CONVERT

PHASE 3PROFIT

PHASE 4ENJOY

The solar photovoltaic modulesabsorb the energy from sunlight andgenerate direct current (DC) power.

The Inverter converts this power intohigh quality AC electricity forconnection to the utility.

Net-Metering allows meter to spinbackwards and "bank" excess energyfor later use.

Living Independently solar powered.by the sun!

2.4. Voltage Source Inverter with Pulse Width Modulation

2.4.1. Voltage Source Inverter

The amplitude of the harmonics can be reduced by using the pulse width modulation

(PWM) technique [13-14]. The basic concept of the PWM method is the division of the

on-time into several on and off periods with varying duration. The rms value of the ac

voltage is controlled by the on-time of the switches. The most frequently used PWM

technique is sinusoidal pulse width modulation. This approach requires a bridge

converter with IGBT or MOSFET switches shunted by an anti-parallel connected diode.

14

The diode allows current flow in the opposite direction when the switch is open. These

freewheeling diodes prevent inductive current interruption

This provides protection against transient over voltage, which may cause reverse

breakdown of the IGBT and MOSFET switches. The typical circuit diagram is shown in

Figure. 2.4.

+

Figure. 2.4. Single-phase voltage source converter

During the positive cycle, S I and S2 are switched by the high frequency pulse train

shown in Figure 2.5.During the negative cycle, the pulse train switches S3 and S4.

IS

LoadCurrent

SOms40ms30msV(VS:+,VS:-)

Time

LoadVoltage

20msv

10mso V(L1:1,VOUT-)

PWMOutputVoltage

Oso

I(VS)*10

400

o

-400

Figure 2.5: Gate pulse input signal, and ac voltage and current outputs of a pulse width

modulation (PWM) converter.

The load inductance integrates the generated pulse train and produces a sinusoidal

voltage (Vac) and current wave, as shown in Figure 2.5.The width of each pulse is varied

in proportion to the amplitude of a sine wave. A typical PWM waveform is also shown

in Figure 2.5.The switches in this converter are controlled by gate pulses.

The gate signal contains several pulses distributed along the half-cycle. The control

circuit produces the gate pulse train by generation of a triangular carrier wave and a

sinusoidal reference signal. The two signals are compared, and when the carrier wave is

larger than the reference signal, the gate signal is positive. When the carrier wave is

smaller than the reference signal, the gate signal is zero. This results in a gate pulse with

variable width.

On the next page, in Figure 2,6, it

(a) shows the carrier wave and reference sine wave;

(b) depicts the resulting gate signal with variable width pulses. It has to be noted that

several other methods are used for generation of PWM signals

16

1.0VCarrier wave

/

..... ';"1/' ..~.'-.:

Reference signal/

.:I .

.j..

OV".", '"

:--,'. "...:, . ~-.,.., --- _.,".- ~-:-: .-

.:?

Os 5msV(PWM_ TRI1.E1:IN+)

10ms 15ms• V(PWM_TRI1Vtri:+)

Time

20ms 25ms

(a) Triangular carrier wave and sinusoidal reference signal

Gate pulse with variable width

/ ----------

.OV

1.0V

-1.0V

as 5ms• V(PWM_TRI1:s)10ms 15ms 20ms 25ms

Time

(b)Variable-width gate pulse signal

Figure 2.6: Pulse width modulation (PWM) signals.

The frequency of the reference sine wave determines the frequency of the generated ac

voltage. The amplitude of the ac voltage can be regulated by the variation of the

reference signal amplitude. The amplitude of the fundamental component of the ac

voltage is:

vV = con/rot V =mVacV de decarner

The modulation index, m is the ratio of the peak-to-peak ac voltage (2 Vac) to the dc

voltage.

17

2.4.2. Freewheeling diode

The inverter interrupts the current several times each cycle. The interruption of an

inductive current would generate unacceptably high over voltage. This overvoltage

generation is eliminated by providing freewheeling diodes connected in parallel with the

switches. When the switches open, the current, if inductive, is diverted to the diodes, as

shown in Figure 2.7.

~ GmrtWffisWtms Sl arrl~ dmrlarrl~ arrl~ q:en•••....... Gmrt WffisWtmsSl arrl~ q:enarrl~ arrl~ q:en

••I.;m.J ••••••• ldo

~ t,,, ,, ,, ,, ,, ,

!! ,~

,,Va:

, , +, ,---. , ,,Vd;

~ .~~t

,,,, ,, ,,, ,, ---.•••••••••• ••••••••••

-Figure 2.7: Freewheeling diode operation.

The diagram shows the current path when switches 8 I and 82 are closed, and switches 83

and 84 are open. When switches 8 I and 82 open (now all switches are open), the current

18•

diverts through the diodes of switches 83 and 84. This current diversion prevents the

interruption of inductive current.

2.5. Switching Mode Regulator

Dc converter can be used as a switching-mode regulator to convert a dc voltage, normally

unregulated, to a regulated dc output voltage. The regulation is normally achieved by

PWM at a fixed frequency and the switching device is normally BJT, M08FET or IGBT.

There are four basic topologies of switching regulator [15-21]:

I. Buck regulator

11. Boost regulator

lll. Buck-boost regulator

IV. Cuk regulator

2.5.1. Buck regulator

The buck converter is also known as the step-down converter. Here the average output

voltage is less than the input voltage.

INPUT

Vin

L

Figure. 2.8: Buck Converter

OUTPUT

Voc

In this circuit the transistor turning ON will put voltage Yin on one end of the inductor.

This voltage will tend to cause the inductor current to rise. When the transistor is OFF,

the current will continue flowing through the inductor but now flowing through the diode.

19

It is initially assumed that the current through the inductor does not reach zero, thus the

voltage at Yx will now be only the voltage across the conducting diode during the full

OFF time. The average voltage at Yx will depend on the average ON time of the

transistor provided the inductor current is continuous.

T

T

TIME

Figure. 2.9: Voltage and current changes

To analyze the voltages of this circuit let consider the changes in the inductor current

over one cycle. From the relation

di= L-

dt

the change of current satisfies

eli ~ J(V1 -Vo)dt + J(Vx - v.,)dtON OFF

For steady state operation the current at the start and end of a period T will not change.

To get a simple relation between voltages ,it is assumed that no voltage drop across

transistor or diode while ON and a perfect switch change. Thus during the ON time

Yx=Yin and in the OFF Yx=O.

Thus

0= dl = .b""(Vin - Vo)dt + ri",,+i<1'j( -Vo)dt\m

20

which simplifies to

-- ••....._ r._.•••.

which gives,

and defining "duty ratio" as

the voltage relationship becomes Vo=O* Vin. Since the circuit is lossless and the input

and output powers must match on the average Vo* Io = Vin* lin. Thus the average input

and output current must satisfY lin =0 Io These relations are based on the assumption that

the inductor current does not reach zero.

2.5.2. Boost regulator

The buck converter is also known as the step-down converter. Here the average output

voltage is more than the input voltage.

INPUT V:o.: OUTPUT

Vut

• IVo

•

-J'I

Figure. 2. I0: Boost Converter Circuit

21

While the transistor is ON Vx =Vin, and the OFF state the inductor current flows through

the diode giving Vx =Vn. For this analysis it is assumed that the inductor current always

remains flowing (continuous conduction). The voltage across the inductor is shown in

Figure. 2.11 and the average must be zero for the average current to remain in steady

state

This can be rearranged as

Vo T 1-~-~/lin [off (1 - D)

and for a lossless circuit the power balance ensures

.10-. ~(I-D)l'ln

\' ,-'L

T

(Vin- Vo)

TIME

Figure. 2.11: Voltage and current waveforms (Boost Converter)

Since the duty ratio "D" is between 0 and I the output voltage must always be higher than

the input voltage in magnitude. The negative sign indicates a reversal of sense of the

output voltage.

22

2:5.3. Buck-Boost regulator

Here the average output voltage may be more or less than the input voltage depending on

the duty cycle.

LINPlrr OlrrPlrr

+ +

Vin v.Ie• •

Figure. 2.12: schematic for buck-boost converter

With continuous conduction for the Buck-Boost converter Vx =Vin when the transistor is

ON and Vx =Vo when the transistor is OFF. For zero net current change over a period the

average voltage across the inductor is zero

('./in)

T

(\fQ)

TIME

Figure. 2.13: Waveforms for buck-boost converter

which gives the voltage ratio

23

ff~..•

v:') DVi". (1- D)

and the corresponding current

10lin

(1- D\. ,

Since the duty ratio "0" is between 0 and I the output voltage can vary between lower or

higher than the input voltage in magnitude. The negative sign indicates a reversal of

sense of the output voltage.

2.5.4. Cuk Regulator

The buck, boost and buck-boost converters all transferred energy between input and

output using the inductor, analysis is based of voltage balance across the inductor. The

CUK converter uses capacitive energy transfer and analysis is based on current balance

of the capacitor. The circuit in Figure. 2.14 is derived from DUALITY principle on the

buck-boost converter.

INPUf

Vin

+

LZ

c

OUfPlrf

+

v.

Figure. 2.14: CUK Converter

It is assumed that the current through the inductors is essentially ripple free andean

examine the charge balance for the capacitor Cl. For the transistor ON the circuit

becomes

24

INPUT LI L2 OUTPUT,ILl vLI -

++ +

Vin v.C

Figure. 2.15: CUK "ON-STATE"

and the current in C I is Ill. When the transistor is OFF, the diode conducts and the

current in C I becomes IL2.

INPlTf LI L2 OUTPUT

+ III ''L2+ +

Vin v.C

Figure. 2.16: CUK "OFF-STATE"

Since the steady state assumes no net capacitor voltage rise ,the net current is zero

which implies

I L2 = (1- D)ILl D

The inductor currents match the input and output currents, thus using the power

conservation rule

Vo D-=-Vin (1- D)

25

"1

Thus the voltage ratio is the same as the buck-boost converter. The advantage of the CUK

converter is that the input and output inductors create a smooth current at both sides of

the converter while the buck, boost and buck-boost have at least one side with pulsedcurrent.

2.5.5. Converter Comparison

The voltage ratios achievable by the DC-DC converters is summarized in Figure. 2.17.

Notice that only the buck converter shows a linear relationship between the control (duty

ratio) and output voltage. The buck-boost can reduce or increase the voltage ratio with

unit gain for a duty ratio of 50%.

Variation of voltage gain wijh duty cycle

l 0 Ql ~ Q3 M Q5 M V M ~

__ ..__ dutycycle,D

Figure. 2.17: Comparison of voltage ratio with duty cycle

2.6. Converter Interface of PV Panels

In grid-connected inverters for PV applications, a number of different approaches have

been developed and used over the last 20 years. An excellent review of such systems

available in Europe is given in [22J. Only the two more common approaches used in

smaller residential scale installations (1-3 kW) are compared here (Figure. 2.18).

26

2.6.1. Single DC String, Single DC-AC Inverter

In a residential system of say 2 kW or less, all the PV panels on the rooftop can be

connected electrically in series, to create high voltage low current de source. This source

is connected a single dc-ac inverter within the roof or house. The ac then runs to the

residential switchboard [23].

__ c__

YVV

DCB~

••••••

Figure. 2.18: Comparison ofthree grid connected PV inverter topologies.

a) a single dc-ac inverter connected to a single de PV string,

b) integrated dc-ac inverter for every PV panel and

c) the proposed series connected panel integrated DC-DC converters

connected to a centralized dc-ac inverter.

27

2.6.2. Individual DC-AC Inverters per Panel (Module Integrated Converters)

In this more recent approach, each PV panel has its own dc-ac inverter, mounted at the

panel on the rooftop. A 220- V ac connection from the switchboard runs to the rooftop,

and loops from inverter to inverter, panel to panel. Each panel is now effectively placed

in parallel, via its own dedicated inverter. To be small, light and low cost, module-

integrated converters generally use high frequency switch mode techniques. To

efficiently convert the panel's low dc voltage to the 220-V ac grid voltage they invariably

require a transformer isolated converter. Most approaches rectify to a high voltage dc bus

which is followed by an ac inversion stage and line side filtering.

2.6.3. Multi-Converter Strings-Panel Integrated DC-DC, string DC-DC

The approach proposed in this thesis combines aspects of this two approaches. Every

panel has its own converter, but these converters are DC-DC converters, and the panels

with their associated converters are still placed in series to form a dc string. A single dc-

ac inverter is then required to connect to the grid. This intermediate solution is argued to

combine the best features of the two existing approaches presented.

2.7. Batteries Used in Some PV Systems

Batteries are often used in PV systems for the purpose of storing energy produced by the

PV array during the day, and to supply it to electrical loads as needed (during the night

and periods of cloudy weather). Other reasons batteries are used in PV systems are to

operate the PV array near its maximum power point, to power electrical loads at stable

voltages, and to supply surge currents to electrical loads and inverters. In most cases, a

battery charge controller is used in these systems to protect the battery from overchargeand over discharge.

28

,,'r 0

2.8. PWM Control

A pulse-width modulated signal is a square wave whose duty cycle is proportional to the

instantaneous value of some continuous source signal. The PWM signal effectively

applies discrete "on" and "off" signals for varying amounts of time. Below, there is a 1Hz

sine wave modulated with a 10Hz square wave.

Source Signal: Sine Wave of 1 Hz

0.8

0.6

0.4

0.2 0.4 0.6 0.8 1.2 1.4 1.6 1.8 2

- - ,-

,

Pulse-Width Modulated Sine Wave1.5

0.5

o

-0.5o 0.2 0.4 0.6 0.8 1 1.2Time (s)

1.4 1.6 18 2

Figure.2.l9: Pulse width modulation

is driven by a constant value of I and the 50% duty cycle square wave.

2.8.1 Principle

II :;'1 I .(I "I 'd YI.1l I

Figure.2.20 :Sguare wave, showing the definitions ofYmin,Ymax

29

~.'. IT.l<\'tf

Pulse-width modulation uses a square wave whose duty cycle is modulated resulting in

ihe variation of the average value of the waveform. If we consider a square waveform}\t)

with a low value Ymin, a high value Ymax and a duty cycle D ,the average value of the

waveform is given by:

1 T .;;= - ( f(f.)elt'" T 'n ..•0

As}\t) is a square wave, its value iSYmax for 0 .< t .< D . T

and Ymin for D .T t < T. The above expression then becomes:

Y 1 (f,DT rT )T 0 Y",oJ: elt + JDT Ymin dtD. T. Y"hu.+T(l-D) Yl1li 11

TD . YmoJ: + (1 - D) Ymin

.This latter expressIon can be fairly simplified. in many cases where Ymin = 0 as

y= D . Ymo.r. From this, it is obvious that the average value of the signal ([}) is

directly dependent on the duty cycle D.

2.8.2. Generation

2.8.2.1 Intersective

The simplest way to generate a PWM signal is theintersective method, which requires

only a sawtooth or a triangle waveform (easily generated using a simple oscillator) and a

comparator. When the value of the reference signal (the green sine wave in figure 2.21) is

more than the modulation waveform, the PWM signal is in the high state, otherwise it is

in the low state.

30

"

,/ I:1 Jj ,:

,- r' I

t /1": 'I:" / li !' Ii'I ,

I I " I I I I I I " I I ,I III :' , I Ii I i' I : i' I ' I III "" 'i, '[I II I j' Ii ,'I! i I, ! , , I , 'r j' I (' I , " I I i'

I " / ,.,' ,I I ~,' i I J: I I " ,I I , l. I I, j , I' , I I I I Ir , "I I ,I J I I 'I, II I ' I ' I ,I I' I II I ! I f J

" I I .' I ! ! " , ~ 'f , ' ,I ' .', 1 I I I. ,I I

"['i.

Figure.2.2I: A simple method to generate the PWM pulse train corresponding to a given

signal is the intersective PWM: the signal (here the sinewave) is compared with a

sawtooth waveform When the latter is less than the former, the PWM signal is in high

state (I). Otherwise it is in the low state (0).

2.8.3. PWM Methods

Various PWM techniques, include:

1. Sinusoidal PWM (most common)

The most common PWM approach is sinusoidal PWM. In this method a triangular wave

is compared to a sinusoidal wave of the desired frequency and the relative levels of the

two waves is used to control the switching of devices in each phase leg of the inverter.

2. Space-Vector PWM

Space vector PWM is an advanced, computationally intensive technique that offers

superior performance in variable-speed drives. This technique has the advantage of

31

taking account of interaction among the phases when the load neutral is isolated from the

center tap of the dc supply. Space vector PWM can be used to minimize harmonic

content of the three-phase isolated neutral load.

3. Sigma-Delta Modulation

Sigma-delta modulation is a useful technique for high frequency link converter systems -

uses integral half-cycle pulses to generate variable freq., variable voltage sinusoidal

waves.

2.8.4. Objective of PWM

.:. Control of inverter output voltage

.:. Reduction of harmonics

2.8.5. Disadvantages of PWM

.:. Increase of switching losses due to high PWM frequency

.:. Reduction of available voltage

.:. EMI problems due to high-order harmonics

In our circuit, sinusoidal pulse width modulation is used for switching. The description

is given to the next page [24-26].

32

QC

2.9. The Conventional VSI

The single phase VSI in Figure. 2.22 uses the topology which has the characteristic that

the average output voltage is always lower than the input dc voltage. Thus if an output

voltage higher than the input one is needed, a boost DC-DC converter must be used

between the dc source and the inverter, shown in Figure. 2.23. [27-35].

+Vin

R

+ Vo -

Figure. 2.22: The conventional voltage source inverter or buck inverter

Yin

cR

+ Vo -

BoostDC-DCConverter

Figure. 2.23: Circuit used to generate an AC voltage larger than DC input voltage

33

-,..

2.9.1. Proposed Boost Inverter

In this thesis, a new VSl is proposed, referred to as boost inverter, which naturally

generates an output ac voltage lower or larger than the input de voltage depending on the

duty cycle.

2.9.1.1. The New Inverter and Principle of Operation

Let us consider two DC-DC converters feeding a resistive load R as shown in Figure.

2.24a.The two converters produces a dc-biased sine wave output such that each source

only produces a unipolar voltage as shown in Figure. 2.24b. The modulation of each

converter is 180 degrees out of phase with the other so that the voltage excursion across

the load is maximized. Thus, the output voltage ofthe converters are described by

v = V + V sin wi (i)1 de In

V = V - V sin wi (ii)2 de m

Thus, the output voltage is sinusoidal as given by

V = V - V = 2V sin wi (iii)o 12m

34

( i

(a) Two DC-DC converter

t ~--.~,.t-~.~....•,..",..~..t' •.••..••.•4._..•_-_.•.~•...-_.•._._.----r"'- ---+-- ..•.,

VI ~~~_. _/~ ..... /; V

OC...--./ .....~.~ --'-~_..- :

,O\t + .. ----.-r------'!+------.'f--.---.'f .........• -...- ... -~. , ... f .•••..•••••••

LinH:

i .' ,.~ ".<-",. +- "'!- •• " .••.• ~ •••••• -•••.•.••• -- +- -'.•..__...•.

\'2~-.-~~-7~': '---_/ \'nc --------'

o \,r ~ .•. , '.. +--_. ----f.--(: .. -i-------.+---._ •.•• ---- --..•.---- --+--..__+•...•. time

(b) Output voltage

Figure. 2.24: Principle of boost inverter

Thus, a dc bias voltage appears at each end of the load with respect to ground, but the

differential dc voltage across the load is zero.

35.,

i!"'c,-

2.10. Boost Inverter Circuit:

Each converter is a current bidirectional boost converter as shown in Figure. 2.25a. The

boost inverter consists of two boost converters as shown in Figure. 2.25b. The output of

the inverter can be controlled by one of the two methods: (I) use a duty cycle D for

converter A and a duty cycle of (1- D) for converter B or (2) use a differential duty

cycle for each converter such that each converter produces a dc-biased sine wave output.

The second method is preferred and it uses controllers A and B to make the capacitor

voltage VI and v, follow a sinusoidal reference voltage.

Vin

+

C V1

(a) The current bi-directional boost converter

R

01 + Vo. D3

C2 V2ClVI 11 l2

02S2 04

64

(b) The proposed DC-AC boost converter

Figure. 2.25: The proposed Boost Inverter

36

2.10.1. Circuit Operatiou:

The operation of the Inverter can be explained by considering one converter A only as

shown in Figure. 2.26. There are two modes of operation: mode I and mode 2.

R

82 + Vo+

02

1 C V1 +V2

Yin81 01

Figure. 2.26: Equivalent circuit for the boost inverter

Mode 1: When the switch S] is closed and S2 is open as shown in Figure. 2.27a,current

ill rises quite linearly, diode D2 is reverse polarized, capacitor C] supplies energy to the

output stage, and voltage V] decreases.

Mode 2: When switch S] is open and S2 is closed ,as shown in Figure. 2.27b,current ill

flows through capacitor and the output stage. The current ill decreases while capacitor

C I is recharged.

Ra L1

V1

R1

+ Vo.

V2

Figure. 2.27a: Mode I: Sl is closed and S2 IS open

37

Ra L1

C1 V1

R1

+ Vo-

V2

Figure. 2.27b : Mode 2: Sl is open and S2 is closed

The average output of converter A, which operates under the boost mode, can be

found from

At mode I:

At mode 2:

From the above two equations,

=> V,." TON + Vl.l TO!'F = 0=> v,JON + (V" - 1'" )T;m' = 0=> ~'IIT()N + ~'IITOFF = V;)TOFF=> v,J = Vo(T -TON)

Vo. T=>-=---

1'" T - TONVo D=>-=--

1'" 1-D

So, V, 1 .- = -- (lV)VI" 1-D

The average output of converter B , assuming which operates 180 degree out of phase,

can be found from

V, 1- = _ (v)1'," D

38

Therefore, the average output voltage is given by

V V. V. v'n v,,, (.),,= 1- 2 = I-D -D VI

This gives the dc gain of the boost inverter as

where D is the duty cycle. It should be noted that va becomes zero at D=0.5. If the duty

cycle D is varied around the quiescent point of 50% duty cycle, there is an ac voltage

across the load. Because the output voltage in equation in (iii) is twice the sinusoidal

component of converter A, the peak output voltage equals to

V =2V =2V. -2V (viii)n(pk) m I de

Because a boost converter cannot produce an output voltage lower than the input voltage,

the dc component must satisfy the condition

Which implies there are many possible values of Vdc• However, the equal term produces

the least stress on the devices. From the equation (iv), (vii) and (viii), we get

V = 2V,n _2(V"{Pk)+V)o(pk) 1- D 2 In

Which gives the ac voltage gain is

G = v,,{Pk) = Dac V;n I-D

Thus, V,,{pk) becomes v'n at D=0.5.

39

Chapter 3

Simulation and Experimental results

3.1. SystemDescription

New residential scale photo voltaic CPV) arrays are commonly connected to the grid by a

single dc-ac inverter connected to a series string of pv panels, or many small dc-ac

inverters which connect one or two panels directly to the ac grid.

Buck, boost, buck-boost, and Clik converters are considered as possible dc-dc converters

that can be cascaded. ORCAD Capture 9.1 simulations are used here for conversion.

The, conversion structure from solar sell to home is shown in the Figure. 3.1. It consists of

the cascade connection of two stages. The first stage is a boost-regulator and the second

stage is the boost inverter. A solar cell can charge a battery up to 12 V de. Using boost

regulator is the first stage where output de voltage is almost 50 V de. This output is the

input of the second stage of the boost inverter. Here, the output is 230 V ac , pure

sinusoidal. Then this voltage is applied to home.

Boost BorneBoost Ae•Solar cell 12VRegulator Application

Inverter

Figure. 3.1: Conversion of solar cell to home application

40

/

.,

Here, a solar cell charges a battery up to 12 V dc. Then a boost regulator is used. It boost

up the 12 V to 48 V. This is the input of the boost inverter. Its output across resistive load

is 230 V ac. This is then applied to home.

3.2. The Circuit Description For The Proposed Boost Inverter

The boost dc-ac converter is shown in Figure.3.2. It includes dc supply voltage V;n, input

inductors LJ, Lz and L3• power switches 81 - 85, transfer capacitors CI - C3, free-

wheeling diodes DI-D5 and load resistance R .The principal purpose of the controllers A

and B is to make the capacitor voltages VI and V2 follow as faithfully as possible a

sinusoidal reference. The operation of the boost inverter is better understood through the

current bidirectional boost dc-dc converter shown in Figure. 2.8. In the description of the

converter operation, we assume that all the components are ideal and that the converter

operates in a continuous conduction mode. Figure. 2.9 shows two topological modes for

a period of operation.

3.2.1. Control Design Methodology

In the design of the converter, the following are assumed:

.:. ideal power switches;

.:. power supply free of sinusoidal ripple;

.:. converter operating at high-switching frequency.

3.2.2. Selection of Control Parameters

Once the boost inverter parameters are selected, inductances LJ, L2 and L3 are designed

from specified input and output current ripples, capacitors CI - C3 are designed so as to

limit the output voltage ripple in the case of fast and large load variations, and maximum

switching frequency is selected from the converter ratings and switch type.

41

3.3 Simulation and Experiment

3.3.1. The simulation and Experimental results

Frequency, f=50Hz.

R= 250 ohm

Vin = 12 Vdc

VO"' = 226 Vac

S, - S5 : switches;

D,-Ds : DINI 190(diodes);

C, -C2- C3 : 400uF

L,_ L2-L3 : 10 mH

R1

VOFF = 2VVON = 3V

53

C2

-=-0 s

VOFF '" 2VVON = 3V

54

L3

D7D5

L2

06 06

D12

~o

C1

VonD1N1190

V1 =-1V2 = 1TO '" 0TR =. 01mTF ::: .001mPER = .25m

PW=.1m

OFF = 2.0V1 ON = 3.0

D11

~o

C3

Figure. 3.2: Boost Inverter with ideal switches

42

•,

SI

« [« Rvee:l~ vee 1111

ISV U4AVI'IO USA

~'.10 Rl 8C= m '0.0 TR' 248ms1111V3 TF' OOlms= 1

lSV PW;.OOlms.O

~

PER' .15msVl0

VOFF'O 'VVM\?l' 7 .FREQ' 50

"'0 vee0Figure. 3.3: Control circuit

16U

-16UOs 2as ~RS,U(UlA:') • U(UlA:-)

6115 80S 111115 12115 16115 18115 261lS

HoeFigure. 3.4a: Pulse Width Modulation signal

43

.~.26U

.......... --

............ ..•. -- -----

•• "'r-- --- -"f" ••••• t •••••••

........, ; ..,...: . • •••••••• '1 ••••• •• ••• f •• •• -t •••••

..,... ..

..{_.. ..-2OU

us 20s, U(UIIA:OUT)

40s 60s 80s IOns 120s 140s 160s 181'5 21lns

Figure. 3.4b: Pulse width maculated signal

2. Oms

IiIII II

-H+I I II I

I I I

-*I,

l.ams

I I II I I

++ II I I

I I I-+: :I II

1.6ms

I I III

1. 4ms

I '

. LJ1-FTiU-1" -III I I I I

1.2m5

I~I I..LI II

I I II I I

-H .I-~I II II I

1.Orns

I II I

II I I

o .8m"

'II I

O.6ms

-H~-+-~ I II I -1-LLII I I I I

20VI II II II -I

lOY I II

'Ii .-LI III

ifov I I I

! I -1-LL -1-1 i- J-l I I-j-lJ--1++- I I LL -1 I I

-lOV + 1 tf-;. I

.:E. Ilr _:r-LLL -1-1-1_-+ I I

.20v I IT I I I I I IOs O.2ms O.4m3

• VIR2:1I • V(U1A:OUTITime

Figure. 3.5: Output wave shapes ofS I and S2

44

" ,-_ ~................•...•.... , ." '"... ;--_.~---; .._. -_.-'- -_: __ ._~-_. _._-~ .._~-_._~....

••• , •••• , ••••••••••••••••••••••••••••••••• ' ••• 4 ••••••••

•••• __ ••••••••••••• __ ••••••• C ••• " ••••••••

, ,

300U

200U

100U

OU

.........•. __ ..__ .

, ,

•....•....~.......•.......•.... '........•

" ," ,..•....•... ~ ....•, " ,

" ,

.. ..........•....---~_...•.. _.

_.~- .. ,._.-.- .:- - .-~....

.... , ...'. __ .'.__ .

• 1 ' ••• 1

.~~~.... . ..: ...:....; ...~ ~~.... ...'. ..•....' ...~~~.......~..: : .

...~~~ -: : ~.

..~....~....... -'~"",'--'...~..~....~....

, , ,...~..~....~....

...•...... __ .•.._-

...•.........•....• _.'. l. '. _

..~_ ..~- - -~.-_ •• __ .C J _

•••• •• ~ ••• J ••••

••• ~ ••• ~ ••• J ••••

• ••••••••• 1 ••••••, , ,---_ .._-_._-_ .•....

..__ .•.. __ .. _--

, ,'-:'_-l- __L---~ --:-._.~-_.• •• ' •••••••• C •••

• ••• ' ••• , ••• C •••

, '. '" '"... ~.... ~... ~......•. ;.... t .... ;•....... ~.•. ~.... ~.•..... : .... ~... ~-.... - .. :.... ~.. -.~ ..., ,. , , .,' " .. .. :-.-.t : : : ':"" t .. ';' "-:' .-. --. :" .-t 1 t .. ':." .: .

...~~~ ~ :.-..~ - ~~ ~......~ ~~ : ~~., ,. '" .,' '" '"••• ~••.. ~.•. ~.- -.: t ~ -~ .. J ••• , •••••• : •• -.~.-.~- ••••••• :•••• : •••• ~ •••

, " '"

41Jms

••• J •••• L ••• '••••

••• J •••• L •••• ' ••••

••• J •••• L •••• ' ••••

-100UOs• U(C2:2)

, , ,....~~ ~... ..~~~.....~~~.....~~ ~.

, , ,

•••••••• J •••• , ••••

....•.... '....•....

....~ ; : .

.... : : ; .

60Pl5 80ilS

Tillie

1001115 1281115 140ilS 160ms

Figure. 3.6: Output voltage across C2

161Jm51200510005S005

Ii",

600540ilS

U : : , , , , , , , , , ,,.... ._ ..•............. ....•.........• ._ .. ..-•....•........ .........•......... ...•....•..... .........•...: ' , , , , , , , , ,, , , , , , , , , , , , , ,...•....• .. '.... ....•..... _ ..•... _ ...•.........• .... .........•...•.... ....~...•......... ....•...•....•... ........~.. _ . _ ........•... .~..., , , , , , ,, , , , , , , , , , , , , , , , , , ,.. .... ._ ..~........•... ....•........ _. ........•........ .........•......... ..._~....•....•.... ........•.... .........•..., , , , , , : : A: ....~...j..~ ... ' , , , ,' , , ... + ... ;..rt ...... ... ....•............ ....•.........• .........•.... - ._ .. .........•.., ,

U' , , , , , , , , , , ,

: , ..1... : : : ,.~.... ....: ... ....~...~.-.,' .. ....l...~. .: ... ...~....~..~... ....;....~. .... l. .. J • ..~... ••• t •••• ~ .: ... .... ~ ••• t • .. ..., , ,

••• J •••• ....: ... ....~...~...~.. .... :....;. ..: ... ••• J •••• L ... .. •••• '•••• 1 ...•. .. •••• c ••• J • .., ... ...:....~..~.. ....:.._.~.., .., , , , ,, , , , , ,...~....~...~.

, , , , ,...~... ,L•• _.L .. ••• ',c ••• ~. ",'. ....l...~..: .. .. ..•. ~... t ... ~ .. ....~...~... l • •• t •••• ~ ..~. .. •••• C ••• I .._~.., ,, , , , ,...~... ~....:. .. .. ..~...~..~. ....:..... ...:. .. • •• J ••••••• J. .. ....:....~...:. .. •••• ~••• J ...~... ...:.... ...~. .. • ••• ;•••• 1 •• _L, ,, ,, , , , , ,

....~..-i-.-+. ' ,••• J. .. -..._. ....... ........ ....... ...•... ..

I;l+"' , , , , , : : , , , , ,, , , , , , , , ,....•... ....... LV......._ ..•.. .•....... ........ •........ ...v....:..I/:"':" ........•...., ,

....:..~....:... ' , :/:' , .::;.;... ,, , , :y' , ....~..:....:... ' , ,....•..•........ ...;... :'.'!'" ._._.- .~....•.., , ..y ....;... ' , , ....~..L...~... : : : ,, , , , , ,.•........ ......~........ .... ...•....... ... ..•....•.. .... ...•....... ............., , , , , , ,, ,: : : , , , , , , : : , ,, , , , , , , , , , , , , , ,...~....~....:. .. ..~...~....~... _ ...:.... :....:.... ...~....~...~.... ..-.:....~....:.... •••• c •• _J •••• L••• ...:....~...~.... ._.~._..:....~..., , ,, , , , , , , , , , ,...~....~....:.... •••• C ••• I •••• L. __ ....:....;....:.... ...~....~...~.... ....:....:....~..- ....~...~....~... ..-:-...~...~ ....:....:....~..., , ,, , , , , , , , , , , , , , , , ,...~....~....~... ....~...~....~_ .. ._ ..:...~....:.... _ ..~._..~...~.... ....:....:....;.... ....~...~....~... ...:._ ..~...~ ....;....:....~..., , , , , , , , , , ,...~.... ,' .. '. :.... ....~...~....~... _._.: ....:....:.... ...~.._.~- ..~.... ....:....:....~... ....~...~....~... ....:..._~-..~...- ....~...:....~..., , , , , , , , , , ,

OU

300

100U

-100UOs 20",• U(C1 :1)

Figure. 3.7: Output voltage across Cl

45

300U

__ ::: ::: , --ii ::: : : :--- ._- ...-._--

....•.... -_ ...•.. _-: :

160m,140ms1211llls1lHlll1s801'15601115401115

~: ' ,-- -- - ----.-- --- --- --;.;--- ----- ' --~- --ri--- -fl --- -t\:--- -ri--- --ri----rt--('i:---A n ~ : : :~'

••• J.. .' __• .c. _.J •• _ L •• , __ .'. _ ••••• J ••• ~ __ ~ .' •• __ __ _ _ _ __ ~_ •• L •• __ •• .J _. _ _.' ~ , _

_.J. .' .'._.J __~ ...•..•... '. __, .J __.~ __~ ••• __: I _.J. __ _•• __~__ ••••••• : ••• L •• ~ ••••• '•••• __.L ••

:::f!2- :::::\~:::;::;: ::::;:~-:: : -::::::~-::;::-:::~:::-:::;--:::;-::::;: -::;::'-::;:::-:::;:r:;-Jp:::[: -::[:-:/_ ' , ----,----'--- - viz::: 1/- ;---)-::j::::j.- --J- :--j- ---/-1--)- --j-r-Y- --Y- i-oj

ou , , , , , , , , ,_•• J._ •• L •• __ '. C J L •• _ ••••• ' ••••••• J .L __ .'. , • L • __ c J .L ••••••• L ••• I •••••••• ' •••• I •••• L •••

, , , , , , , " '" .,'• -- J. < .'. _ •• __ • _}_ •• ~ •• __ ~ • I '. __••• __• ~•••• ~••• ~_.__ ----:----l'-' ~_. ~ ~----;___ ___,. __.L J __ • ; : :•• _

• __ J •• _. , , ~ ~ ~_._ •••• ~ ••• _~ ; ~----."-. _~ • ._ •• ~ •• _~ :•• _. _. __ ~ __ • ~ __ ._~... • •• ~ •••• ~ ••• ~_ ••••••• ~_._~ •••• ~ •••

-- -~-- --~----:- --. - ~•.. ~ ~..• -.•. ~.. -~-- --l --- - . -.;.- .. ~•.. ~ :.•.. l ..•. ~ ..•.•.• ~.•. ~...• ~... . ..••. _.•. J -- --; ---;-- .-;---

200U

10lU

-100UOs 201115

• U(C2:2) • U(Cl:l)Tine

Figure_ 3.8: Output voltage across both c I and c2

16iJ11s140""

" ,..... _-- .._-~--_ ...............•...,, " '"---1-- --r---,- - , ' r---, " '", " ."

---~----~---_._--- .... '.... !.... ~...

120.5100.580.560.540""

200U-,

40011

"" , I ,

, " ,,' ,'" I" '" "--.T - • ..,..••• , •••••••• -c---.- ... ","'" .. T••••••••• _or --'--"T'" •• , •••••••• ---- -- -.T ••••••••

I 'I I" ,'I I '" I I I ",

I I, " "I I" ,'" ,,' 'I I '"

.;~\:-IIff-!TIITjltrII!- :rrrI':j.I , " :,: :': : : :: I ; : : : : ;

••••••••• , - __ •••••••••••• J , __ •••••••• • •• J ._.J ••••••• J. ,•.•.•_.__ •••••• • •••••••• .._ ••••••• J... ... J. •••.•.••••••••••.•••

'I I I I '" '" " I , I I I I I ,

'I '., I I I I" " I I " I I I, I I I

I ' " " " I 'I I ,I " I, I '" I I ,'---,-.--r- - ,-'" "--c---,. -- -'.'f'- •..,..--, -.- -••,••--, --. -- ---,-,-"'T ••••••• ---r---,- --, - .•..•••. -c --, --- ---..,..•.• T••••••• -, , , " I • " I I '" '" '"

, , , I I '" I' " " I '" '"

-20011 : : ::::,: :' :: :: : :I " '" '" " I" I I I I '"

I " I" " I '" .1" ", '" '"~ ••• J •••• ,. , ••••••••• J. , ••••••••••••• _J •••••••••••• ••••• _ ••••••••••••••••••••• • _ •••••••••••••••• _. •••••••••••••••••••

, " ", ", '., ,'" '" '" '"" '" " I '" ,'I' '" " I " I

~••• ~.••• ; •• -.~ -- .•••• ~ ••• ~•• -- ~- -- - - •• : ••• ~.••• : •• -- --.~ •••• ~ ••• ~•• - - - -.;.1. •• -: •••• ~ ••••••• ~••• ~- •• -:... • •• : •••• ~ ••• ~••• .~ ••• ; •••• ~•••, " '" 'I I 'I I ,I' I " I " I '"I " .,' '" I " ,I I I '" '" I I ,

t.--~---. ~- : -.~---~---.~ --.;--- ~---.~....•.. ~ ~--.~.•....• :.: ; ~.-- .. -.~._-~...• ; .•..•.• ~ ~__.~•.....• .;.•.• ;.•__~---• " " I • " I I I I' " '" '" " I, " '" '" I I I " " " I 'I I I I I-400U

Os 20""::,:U(C2:2,S2:3)

ii••Figure_ 3.9: Output voltage at load 250 Ohm, time t=84_I ms, Vout= 226 Vac

46

2.0A

L... . ..•. _.'.. • ••. •...

~.--~--- ... --- .,-- .. ---

. '._-- ._- ---- -..--- --..'---- -- .... ---- ...

~---

1601lls140••12011151001lls8f1ms6011'15401lls

, ",, '". " ",~ ~----~ -:---- ~._-~ ;--- - _- ---, '" "~---~... _~---+. - --- ~-._~----; ...

, " ", " " ",

, " '" '"r ••• :----; .••• :---- •••• :---t ..;-----..!----; ...I " '" "

1.0A

-1.00Os 21J11ls:ii: - J (R1)

Figure. 3.10: Current for Rload= 250 Ohm, At time t= 83.67m, 0.9 A

160msHOrns120mslOOmsBOrns60ms

v , ,i

i ;

f' .(;1;,

v ( ~ (

.. ':'. I I II I if I -:/- ' / I II '/. - ... --.. t-. .__ . -.--_. - L 1/ - ..- - ---. +.. ._--. _. -- ./--- .-J - ..

v JJ, V /, .A j :J j

\._- -._-- ,

-- , .. - . -.,.\ -.._-

\--, ... -_.,. ----

v \ \C ,

",, i i

v, , , , ,

'00

200

-400

Os 20ms 4Omsv V(C2:21 6 V(Cl:1) 0 V(Rl:2,R1;1)

-200

Time

Figure. 3.11: Combined output voltage across C2,CI and for load 250 Ohm

47

3.3.1.1. Variation of output with load 150 and 500 ohm:

161lm,

: - :-

........, ...•• :•.. f ..•• ; •.

140""

, , ,......_.~...•..... _ ...•....•.........

, " ,.,.-., ••••••••• , •••• """""""r'", , ,, , ,...; ; ; ;.- ..; : .

, " ",, " '"

120.,

.,.... ,....

":""f'"

; -: -....;..o

100.,

.~~...:....~...:: : :..,~ ." , ," , ,..~.:..+...:...:: : :-'; - :- :-..,.~..

" , ,..:t ..;....:" " ",.., , , _, .:: ;: :::..~.:....!....;....-.";'....i- .. ':'":: " '"

BO/lls

..., ,.

60/lls

.- ~-:--- -; _. --~- -- _ .. -.---~._ .. t___ ---. __ . _. , .... ..•.. _. t_. __• _

" I ,

- ---, ".- -,--- -, _.- --- j" --"r -. -j--,8 -:~~1'~-~2iJ'i-5ij1)-_.~._.~---or .... -- "j" "'r-- "1-- -- .. --,----'" "-r---

- - ;----:--..!..----+ ...:-.-+ ... --~-:-.. 1----:---- ----:----.; .. --f---- •• +---;---+--- ----:-.. +---;- ....•• ~•• _~---- ••• ~----~ ••• , •• _. -- r"'~----~'" --- ' •••• :._--; .••••• ~---.~ ••• ; •• r---,""""

"", ... ,. '.r".,""

.... ;... :.... f... ...~.. ...1••.

....•.........•.... ........•........, ,,', '", ,,'

""""~"", •••• """'.r"',""

•••• ; •... :•••• ;.- ..••• ~.. -.: •••• 1••••

..............•...""r"',"", •••

••• • :-•.. ~•••• f •..

.... ,.... ,.... ,....

~.......•....~...~~....~ : .

r :-.. -; ; .

-.._,._._, ..._,_.

'f\" :... i..), , ,

ou' -; -\; - :~--- ~---- ---~-_.I : :"._-,----, .. ----l.'--:--"H- :----, ,

400U

-.----.- -- ...---,--- ..-------r--.'-.--'".-

;.-.-:----~----:---- ... +--;----f---200U .--- --,-'-', roo •••• -r"' .~•• -"""

,----.--- .... _ .•..-

-200U

-~OOUos 20"":~:U(R1:2.R1:1)

TilrteFigure. 3,12: Vout = 220.51 V ac at time, t=83.67 ms, Rload=150 ohm

160'5140""120.5100""80.,60.,40.,20.,

, I : : : : : : : : : : , 0 , , 0 ,.....•....,....~... .- ..•...•....•... "ji,!"'7"':'" ...~....:...~"l3'.Ml.:h~,r~0....•....•....•- ... ...•....•.....- ... • •• ..L ••••••••• _ ••' , , , , , , , , , , ,," , , , , , , , ,•••••••••••••• ..L._. ....•.._ •....•... .. •.........•.... .........•......... ..•.... ..•....•... •• _.c •••.•••• _••••• ...•....•......... • ••• L ••••••••••••' , , , , , , , 0 o , 0 , •...~._ ..~... .~ ....~...;.... l(:L:~::::n~..;....~...•••• ..L ••••••• _•••• ..._,_ ........•... .. ....•...,.... ••• ..L ••• , •••• ~ ••• ..~ ••• ~ •••• ; •••• ,L ••• ....•..- ......- .. .. ••• ..L •••••••• /i...:...~...... '.........•... .. •.........•.... . .....•....,._.

'\~"'!""f ...' , o , , 0 , 0' , ,

0 , ,. -',~...~....:.... -.~...~_..~.... ' 0(...:-- ..:....:..... ... • •• ..L •••••••• .. ...•......... ...•....•... .....•....•..., 0 , 0 0 : ' , , , ,, ,

, , 0 o , , o , ,0-0 : 0 0 : " 0 : : 0 0 0I o , 0 0 0 " o , 0 0 , 0 o , ,....~....~....;.. ... ...{....~_.. ... • ...;._ ..}.... ...~...~...~.... ..'.'. ":"",1. ... .... ..~.... :.-.. ••• J • ..~...~.... . ... :.•. t •. -.~ ..."L..~.•..~....:.o , 0 o , " o , , 0 0 , ,.. .... ...~....~-.. ... • ...;....~.... ...~.• ',1. ••• ~ •••• ...•.'. ..~ •••••l .•• "'_,L. .~....:... ....~. ..~...~.... ....:...:-...~...: "A" , 0 , , ,

" , 0 , , , , 0 ,r'" " ..~.... :. . ....~..~....~.. •••• 1- ..:....:... ...~.. .~...~... •• J.' •. .:....~.. ••• _L. .~....~... ...~. ..~...~... - ..-:- ..:....~.."... J._ .~ .... :... 0 , 00 " , , , , o , , , ,....~. . ~.•.. t .. ....:. • .0•••• 1••• ...~.. .~...~... • _J.' •• .:-...~.. ... .~.~....:.. ...~.. .~...~... ....;.- .~....~..f : : ; ", ,

" , , , ,-'1 - ~ 7 -: -: : - :- 7 - -' - - c -: : -: - - ;- c 7 - : ' , -" 0 -, , , ,"

, ,L ••• ; •••• "";'" ._ .•••• J..•••• ....... .......•.. ........ .....•.. ..•..•... .....•. ......... •....... • •• ..L ••••••• , •' \: ' 0 " , 0 0 , 0 , , , 0 ,

" 0 , ,r ... ; .... ,.- .. , ... ....~..l..~ .......... ........ •....... ..•..... .....•- .._ ..•. ._ ...........•., , " , 0 : o , , , ," 0 , ,_ .._ ............ ....•._- ...• .. ........ ....•. .. ......... .. ..,.'.... ....•... .. .. • ••• L ••••••• LI : :

o , ,0

" 0 0 , , ,o , 0 0 0 0 " 0 , ,...t..;"f' ... -...._ ...... .. ....•..... .. ...•.... . _.J. .. • •• ..L ••• .. .. .. .''-;--''If-'-'; .., , : : " : : , :o , , ," , 0 , 0 ,

, '\{: ' '\.I ' , ,

...j....~V" " , ,

..).) V'" ' , 0

.. ..j. ... ;.V~..' , , o , ....:...Ld... t' , ,r .•• ~...• ~•••..•...-. ._ ..~...~._..~... _.J.' ••.. I_ ••••• ...~....~~.~..." ,o , , , 0 , o 0 o , " , , , ...~...+.~.... o 0• ••• J •••• ~ •••• '_ ••• ..-.~...~._ ..~... ....;...~... ,'." .._~....~..,"" ..~.:.... :..v, ... ....~...~..,'" ....:....:.. ,'-'I : : ' , , , , , , " , , , , 0 , 0 ,....~....~.-..:.... ....~...~....~... .... :....;._ ..:.... ...~....~...~.... • •• -' •••• 1 •••• 1. ••• .._.~...~_...:.... ...~....~...~.... ....~...:....~..." , ,L ..~....~...~....

' , , " , , , , , , , ,.._.~...~.._.~... .... :._ ..:....~.... ...~....~.._~.... • •••• '._ •• J ••••••• _ •••• ,L••• ~•••• : •••• ...~....~_..~.... ....:....:....~..." , ,, , , , 0 , , , 0 " , , o , 0 , , , , 0 ,,

00

2.00

-1.00

-2.00os::;:-I(Rl)

Ti.~Figure. 3.13: Current for Rload= 150 Ohm, at time t= 83.67m, 1.47 A

48

160ms140"120.s100"80ns600s40ms

400U, '::: ; ::': ::;: :

i"'~'-'-:-"': ... -...•._-•....•--- ....•----,....•---....•. _--•...•._---..;:._--:....~----...~._-~----:... --..•..._. ~.... __..•...• •..., , , ,'I ,,' I , ,

i"" , ... -r -- _.,•••. - -_.~ _•• j -..• ~._. --.. ;. ---:.-.. ;.... -._~•.. _~-_.~.. { 4-.ihM;228~.22 T--~... ~.---!...._.-j •••• ~-- -i- ... _.--~... !..--~_..;:::i:::L::,~::::::L:!:::L: -~::::L:L: :::LL:L: ::~-_::L:~:::::):::~~:::!::::::~::++::::~:::i:):::

2OOU-, ; : !_ f.\ : : --il--;--:----I) _, ,+ Il-l __; ;____:--f---T--- __~ __; ; _I : : : ••. _\ " " I' ;: : 'I " "}\i::r -:::::::;::::;::::::;:;::::;:::::;:_:;:::;:::::;::_-:;::::;::::::;:_-;::::;::::::;:_-:;:::;:::-::::_-:;::::;:::

ou~"-i y! -,~.;__: -i:-!- ": _: -::- '- ~ -i' _:- -:- ~; -:- -i-

~:::;::::(\::/:-:-:::-i::C;-:: :::-::<:::::-:: :::;:::::--:::: :: :::t::i\::r- ::::::::;--::;---:::;:::::--::;-:: ::::::::i~::;---: : \) :: :: :: :: \ : : \ : :: \ :-200U

, ,~ \!:: ,,,! \!: "! :: \!~- •• '--"' t ,__ •• t_ ••• __ •• t __ • ••••••••• ••• _ •• _.~ ••••••••••••• __ •• ~,. ,_ •• _. _ •• •••••• _ •••• _ •• __ •••••••• __ •••••• _ ••••••••• _ ••• ~ •••

"I' • , I ••I , I " , I I " 'I'~ ••• , •••• r •••• ,••••••• 'T ••• ' •• ' .r." •••. T••••••••• T••••••• , •• "r' •• , ••••••• r' •••• T'.'.r' •••••• r ••• , •••• T•• ' •••• , •••• r" ., ••••••••••••• , •••• T' ••

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" , " I" 'I I-400UOs 21lins:;:: U(S3: 3 ,52: 3)

Tilile

Figure_ 3.14: Vout = 228 V ac at time, t=84 ms, Rload=500 ohm

161lins

, , ,....~..:....~..., ,

140"

,• .. t ••• ~.•• ~•••

120ns100.s

, " '".••• :••. t •••• ;....•••• ,".. ~•... ~.••, , ,

RO"

...~.. ',' ...~...

60.s41lms

, ,...•...,....•..., , ,, , ,, , ,....•........,..., , ,, , ,

20"

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I I I I •

'I "........•.. ............•.• I, • I

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...•....,....'.., ,.........,....,....

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, '" '" , , I" '" ", '"' " '" " " '" '" ",

O.SA

-O.OA

-O.SA

-l.OAOs, I(Rl)

Ii.,Figure. 3.15: Current for Rload= '500 Ohm, at time t= 83_67m, 0.45 A

49

Table: 3.1 Output Power at various load

RIoad (ohm) Vout (volt) Pout (watt)

100 216 471

150 220.51 324.15

200 226 258

250 228 210

500 230 102.6

o -----------.~--~----~--~ ---~--~--~-~500250200

load (ohm)

150100

19.4 I19.219

18.8.: 18.6>:; 18.4~ 18.2

1817.8 .17.617.4

500250200

load (ohm)

150100

600

500

100

£400o::- 300"o> 200

Figure. 3.16: Output voltage at various load, Figure.3.!7 : voltage gain at various load

3.3.2. Efficiency of conversion

It is the ratio of ae output power to the de input power.. p

Efficiency = -'!".!.. *!00%~"

,.'So

3.3.3. Simulation results with practical switches

3.3.3.l.The simulation and experimental results

Frequency, f=50Hz.

R : 300 ohm

Vi" : 12 Vdc

VOUI : 228 Vac

S] - S5 : APT45G J OOBN,practical switches ( igbt) ;

D]-D5 : DINIl90(diodes);

C] -C2 : 265 uF

C) : 280uF

L]_L2 : 10mH

L) : 1 mH

Pout : 173 Watt

Pin : 178 Watt

Efficiency: 97.19 %

200RIll

.Olu O1u

20:5u

10mH 10mH205u

VI=O rIII = 10 VJ

TO = 0 •TR = 0.001mpw= 0.085mTF = .001m

PER=0.1m

12V

gate 1((

R'---'0/1,I .001

.:l-1m

.01u

C2• f

co 280u

f.01

gnd2

01u

~o

Rll

1meg

Figure. 3.18: Boost Inverter using practical switches

52

••

"'" "10\&.J:- VI

o "00'

R"

"

"" <gndl

<gnd2

<g3l~2

Rg R8

5k 5k03

'00'R7

'"

o

o

TUl94

VI = 10

o

V1 = .10

i::~"mJTf •. 001msPW= 001msPER: .2~ms

o

Figure. 3.19: Control circuit

53

1801llS 20lhrls"""140ns128F1SBOns60llls

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ou

4"

201lU

-400UOs 21Jr.ls 40msII U(R111:2.R111:1)

-200U

Timl.'

Figure. 3.20: Vout = 228 V ac at Rload=300 ohm

1B01JIs 20lbrJs160llls111lbrJs12 Oms10""8""6 OlliS40l'S

A: t<:,. ~:

.--:-.+ ..:.. - ... f ..• :••• !..- ...:... ...:... .f ... :.•• !... .;.. -f-. .:...At'1''';'' 1"of- .-:... .~...:._+- .~..- •. f ..

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..~........... ............... .. .. .. .. .. _.~...•-. .. .. ...: , ,

: : : ( \"'.""",-" .. t •••""", .. "". ,...•.. ... ,,-,...,.. .. •••t •• , •• ... •• , ••• t • .. ••• t. '.;" ... ..,...,. .. _••t ••,.. ... .., .•• t •: :.--:-.+ ..:.. ... "':'.-i. ...: •• j •.. :.. "', •••;•.. j . ... .+ ..:. ... ""('r' ", .+--:- ... "':"'f' ._; ","',' ._., .......,.'J\l"r ..'._.'. •• '._J . ...~..'... '. .. , ..~_.~. ... ..~...~.. .. . ..•..,. .. • ~ ••• L .. .., •• L •• ~ • ... •• J ••• L ..

.;-.-\/ ., .. i, : : : : : :••• t. " ..., .. ..,. ••• t ",... , .. ..,. .. "'r .,...~ _.,. .t •• , .. "'r ""'t .. , "", .. "'r ., ••• t, ,

''';-.-J- .. ;... ..+ .:...! .. .--;.. I"'; .. .. -f- .:...! .. .--:- +.~.. ._ .... ~... : .. .+ +.~.. ..+ .:... : .+ +..:.. ..-:.- .:...:..~... l ...:... • _.L •• '... ... ..J •. '... .. • •• L • ..... ... ..~.. '.. .. _••L. ..... .. ..... '.. .. • •• C. ~... .. ._ ...~.. .. ...~. J ••• ...

..•...•...•... ':'['1[ ::::::;\j.:: ... .. .. . ... .. .. .. . ...•.. ..... .. ... ...•. - ...-- .:..~..-:. "":'" ••• t- ••,-""" ••• t •••, • ,... ..,... .. ... '''c'' ,.. ..,._ . .. ... ...,..Vr-' ..,_ .. .. ... ...,.Vi": :~: .+.+~.+.-J- ..:... ... f"':"'I'" ... :.. -t- .. ;... ."i"': .:... ...~..~ f •• .+..f ~... _.. ;.••• :. 1"" .+..} +.- ••• :••• ~ • f ••

, , , , , ,

BOO"

OA

400mA

-!lnOlllA

-BOOIllAOs 201115II -I(R111)

Figure. 3.21: lout = 0.76A ac at Rload=300 ohm

S4

1BOllls 200ms16DIlIS120ms1001115ROms

W,. ',' ,. ','

,. ',' 'C ','" ',' "

" .. ..W

: :: : : : ,.. " ,

: : : +.. : :.. .. '. .. . .. : ..:

. if- + : : : : :.. : ....j. : : : :

w : : : : : :: : : : :

::\: .F- : : :: : : : :.. : ; : ., 'C: : : :.. 1: ::; : . ,: :

: : : : :..: : :

.. "(: : :'~;,',/'i :\1

, , .' ";1i ,. , ,"1, .' .'. ,: : : : : :ow

Os 2OlliS 40llls 6DillS• -U(R111:2,R111:1) * I(R111)

50W

200

150

100

Figure. 3.22: Pout = 173.28 Watt

100

100llls90r.JS

--:---:..

- ---.- ..,..... _. --,_._,--,--_ c_ ••• '••••• : _.J.. __ ' __ ;__

..: +--l-~-~-.,- .,.-....,--.--._'-- --:--.~ ~..:-..:---:--

, , I ,

--....•...•...•....,...•..--.-- .•.. -.-:._-:---:---:--, I , ,

8l1ms70ns60111550l1ls"DillS30flls20llls

: : I:

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:::::::::;:: ::(::(:(1: ::::::::::::~:::::;:::':.ltrrr::::::::::::F::::::;:::'~.: :::.:.::r'~::::::;:::::.'I:" ::1:"_•• _, --c- •••••• _ ,_" __," , , •.::••••','•• t,". . .,. '-r,' --~---,-' ..... -','-~-- r"

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__r_.r ••••••••• _. __._ •••__••••••••••••••• __ •••__ ••__ ••••••••.•• _

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1 OlliS

..... --:

-r- r--r-- •• -- -or _roo •• '

r -r .- -- c--r •• c. --

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..,

•• C __ C __ C __ ,'-_ ••• \' •• C __ '- __ L_ •• c_

--.-- ..-.....----.- .... -.--r--

-++-:---;--- -+.:---.~--:-.-_.:-.

o

00

-50Os• I (R6)

TiIllE.'

Figure. 3.23:Iin = lOA

o-55

280W

100111590/1158illls7001560m5SOm54001530/115

,.'r",-

._~--~-~

, '" , , .+ , , , , ,., , , , , , , ,-- •. ..,...-,.. , .. ",--,--,--,.-." •.•.. ",-- '-r--,---,--,-- .. , • __._~..• , .. , .. , , __ "' . ....•..•.. ,.. __,__,__, __, ..

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__ Coo' -':'-~-- --;'-!'-!'-;-' ";-':--:'-':-' -':--;'--;";" --;--i--:--:-- --:--:'-:'-i-" -';'-;--;--:-- -':--:-';-':-' ":--;--;--;-- ._-'-- _~__J __

, "', "" ,',' "" ",' "" "" "" ,._~- .•.-~_.• -- - •••••••• --.-- --.-->_ .•. -.- ••• ~._~--~- •. - --.-.,_.,.- ••••.• --~--~-~-----~--.--.- ••••••••••. -.--.-- -->--~--~- ..•..•••• ,••, , " "" '" "" "" " , , , , ,. , " .,' , " "" ".,'" "', "" "", , , , " ,," "" "., "" "" "" "', ,._~.-;---:-.~_._.~..~._~--;-- --;--;._;--;- ..-;._~--~-~----~..;.-:..;.- ..;._;_.~--;--- --;-.~--~--~.. -.~..:--:--;-- --;--;--;-~-- ._.,- ..~..,.-, , " ,," "" ,,' , , " ,',' '" 1 "', ""

.-:---:---:-.~•. "':'-.;--;--f-- .. f •• } •• f •• :••• _.:-.-:---:---:-- --.:••; •• f •• f.- --r":---;---:-'- --:"':"1"1" "l.-f--f--f-- .. )-.•;..• :.•. :.. ..:.. ..;.. {--, " ,,', " , " "" ,," "" ,', "", ,t "" " , " ,," "" ",' '" ""

ow

-108WOs 10015 21lms• I(R6) * U(u999:')

Figure. 3.24 : Pin = 178. 86Watt

. pEfficiency = ----""'---* 100%

p."

- 173.28 * 100%178.86

=97%

56

~'.

3.4. Variation of output

(a) in Tabular form

(b) by graphical form

3.4.1. Variation in Tabular form:

The variables are

(i) Boost stage (i.e. duty cycle)

(ii) Modulation Index

(iii) Input frequency to the gate pulse

Table: 3.2 Variation of Boost stage

pw Duty Cvcle Vout(volt) Vin VoutlVin.098 .98 77 12 . 6.41.095 .95 134 12 11.16.087 .87 221 12 18.41.086 .86 226 12 18.83.085 .85 227 12 18.91.084 .84 224 12 18.67.075 .75 166.16 12 13.84.065 .65 133 12 11.08.055 .55 117.3 12 9.77.045 .45 102.5 12 8.54.035 .35 95.882 12 7.99.025 .25 87.112 12 7.26.015 .15 76.6 12 6.38.005 .05 60.275 12 5.02

57

Variation of ac gain with Duty Cycle, D

20 I18.~--16 j,~----

c~~t--i10 t~> 8t:1-

I

2 .I--~~~~~~~~~~~~~~~~~~~_

o l.~~~~~~~~~~~_~~0.050.150.250.350.450.550.650.750.840.850.860.87 0.95 098

Duty Cycle, D

Figure. 3.25: Variation of voltage gain with duty cycle

Table: 3.3 Variation of modulation index

Sin ampl M Vout(volt) VinII 1.1 233 1210 1.0 2279 0.9 2158 0.8 2147 0.7 2126 0.6 2105 0.5 2094 0.4 2053 0.3 2022 0.2 119

58

•

Variation of output voltage with modulation index, m

250 r-'-----200 t------;.,..-.-.~~:::::::::::::::~

~ 150 t--~---------------------~ 17-15 100 .~I----------------------------

> 501.---.--- ..------------ _ia -i--.--_--_- -_--_-_--_--_--,02 03 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1

Modulation Index, m

Figure. 3.26: Variation of output voltage with modulation index

.:. From the graph, it is shown that, the amplitude of the ac voltage can be regulated

by the variation of the reference signal amplitude.

Table: 3.4 Variation of input freq

Fin(Hz) Fout(Hz)20 2030 3040 40.0350 50.0160 60.0670 70.480 8090 90100 100.0 I110 110

.:. It is shown that, the frequency of the reference sme wave determines the

frequency of the generated ac voltage.

59

3.4.2. Variation by graphical form

3.4.2.I.Variation by modulation index

118RS 180l'ts

. .,.. - .. - - ..:... "'r" ~"'i", .. ,, , ... ~ _- ~...•.., ".

116M17JtAS

.,-j--.( ••{•••••. :--••:•••••. .. ... .. . ...~...~..~... -- -~..-:.....172ns

._{-- ...

._~.. ..

170qs16Sns

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. '". ,. .., ""{"-I-":'" .. ,;- ..:... , ... _..:... t ••, ., '" .., .. ,.. ..

•• -:-- .: •. -:.•• •• -~.• -:••• ~••. _.~•. -J-'

CU

lCU

1SU

-1ClU

-lSU160Rs 162RS 16!lns

, U(U9:.) .• U(U5:t)Tille

11605 180ns118ns

.. i"'f ---:-..... :... ~_..•... .. .,'. .. ..,..]"".;--t- "r-t.; ....., ., .. ~--- ~ -_ .. " '". .. . .., .. '"-- _- -.- .. '. '". ,. .". .. '"-- ... -•..•... --- ....._- .... .. ' ... .. . ..

..;-_.; ..~ ~..~;_ .

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-'J'" '-f--' "'f".1 t ....~..- ..~ :-.~~..

_ .....•..~_ .--- ...•...--- .--- ._ ....~--- .

1111115

.+ ..;...;---_..}..~..-•... .. ..,. .. '"-.~...:..~--- -_.: ..~...~... .. '". " '". ... .. , .............. - ~ --, " .,.. .. '". .. ,.,...---.- .•.....-.-- •......, .. . ... .. . .., " .,....-_ -.-- •....... .. .,'. .. , ... . , ; --~ ~.. t- .. ~..

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. .. '" .- _-_._ ., ,.. .. '" .. ...._ -- .•........, '" ., '.. ,, .. , ,

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. . ". .. . '" .. .. ,. .., ,,' ,., '.. .,.-- •......... - -.......•........... -_ ......•...... - _ .•......,- .....•..•._ ., .. ". '" '" '" , .., ., ". ... .., '".. , .,. '" ... . ..

.-f-"i"-~-" "'1--.~---i'" ._-j--'1 ... 1... ---r- .. j"'i--- --f-.+._j_.. "'f"f--+'

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1SU

1 CU

-lOU

-1St/16005 162ns

• t/(U9A:OUT)TI••

Figure. 3.27: Pulse width modulated signal for m=ll

60

15U - ~..__ ._ ••••• J._ _.

.. ---;..._. --_ •...

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68

Chapter 4

Conclusion

4.1. GENERAL

DC to AC power conversion is essential if the supply voltage is a battery or solar cell or aI

fuel cell. Use of inverter for the conversion is essential in power lines of all capacities.

Our proposed circuit is an attempt to propose a new voltage source inverter (VSI)

referred to as a boost inverter or boost dc-ac converter.

The main attribute of the new inverter topology is the fact that it generates an ac oJ~put

voltage larger than the dc input one, depending on the instantaneous duty cycle. This

property is not found in the classical VSI, which produces an ac output instantanJous

voltage always lower than the dc input one. The DC and small-signal performance bf a

boost DC to AC converter is determined simply by substituting the circuit's mo~els

(point by point) by the PWM switch, and analyzing the resulting linear circuits. ';1

Renewable energy can be cost effective right now in the right application. For cabins Ld

homes the first step is to make sure that we have the most energy efficient appliaJbes',I

available. This will lower our cost of the renewable energy system and give a quickerI

payback. Efficient appliances would include fluorescent lighting (about 4 times I, as

efficient as incandescent), efficient appliances such as a refrigerator/freezer and clotlles

washer, efficient water pump, and so on. The use of propane or natural gas apPIian~es

will also have to be considered for heating, cooking, air conditioning, and other hikh

power consuming duties. Although, these could also be done with high efficiency wo~d

burning appliances, solar heating, floor radiant heating, geothermal heat pump, or ot~er

renewable means.

o69

II

I

Photovoltaic can power just about any electrical load. However, air conditionitg and

electric heating elements (cook stove, water heater or furnace) use large amotnts of

electricity which drives the system cost beyond the average homeowner's means. 'I

'I

!IFor most residential and small offices, a I kilowatt to 3 kw system should add soJe real

"

value. For smaller homes and limited roof space, a 250, or 60,0, watt system clan be

installed. A rough calculation is that IDo' watts of AC peak power require 12 squaJe feet!Iof roof space - or I kw requires 120,square feet. I

i

"

1In our thesis, we found 228 Vac for modulation index=I.D, Sin_ampl =10, linputIfrequency=5DHz and duty cycle= 0,.85. The output power can be varied from IDo'~ to

I,"480, W, depending on the load. 'I!

So, it may be concluded that the thesis work is successful to achieve the goal for ruing

a small house by solar power. il

I

,I

'iIII::1I

I

I70,

J,

4.2. FUTURE WORKS

Reviewing the proposal and contributions made in this thesis, we can suggest some.'

future works to be done to achieve the same or related goals.

Research can be done

- on minimizing the time to achieve the desired sinusoidal vales.

- on minimizing the Capacitor current spikes in the inverter. circuit.

- the boost - regulator can be minimized and circuit may more simple.

- the output power can be increased.

- the initial input current is very high (almost 10A). So it can be minimized.

71

References

[1] Stefan Krauter, Fabian Ochs, "All-In-One Solar Home System", UFRJ-COPPE-

EE, PV-Labs, IEEE 2002, Pp 1668-1671

[2] The Solar Electric House: A Design Manual For Home-Scale Photovo!taic Power

Systems By Steven Strong And William Scheller. Sustainability Press. 1993.

[3] The New Solar Electric Home: The Photovo1taic Handbook - Joel Davidson.1990.

[4] Oksolar.Com Serving the Industry since 1988.

[5] Consumer's Guide to Buying a Solar Electric System. September 1999.

[6] Rivas, C., Rufer, A., "A P.W.M. Current Converter For Electric Energy

Production Systems From Fuel-Cells", European Power Electronics Conference

Proceedings, Pp. I-II, 200 I

[7] Http://www.Andrew.Cmu.Edu/User/Zke/Pwm_ModulelPwm_Def.Htm

[8] Http://Casemods .Pointofnoreturn. Org/PwmlPwmtheory .Html

[9] F. HEATH, "The Switching Regulator Power Supply", Electronics World, Pp 13-17. Oct 1971.

[10] W. Robert Erickson, "DC-DC Power Converters," Article In Wiley

Encyclopedia Of Electrical And Electronics Engineering, , Department Of

Electrical And Computer Engineering, University Of Colorado

72

[11] T. Noguchi, S. Togashi, And R. Nakamoto, "Short-Circuit Pulse-Based

Maximum-Power-Point Tracking Method For Multiple Photovoltaic- And-

Converter Module System," IEEE Trans. Ind Electron., Vol. 49, Pp. 217-223,Feb. 2002.

[12] Photovoltaic Panel Simulation User's Guide, Educational Bookmarks, Australian

Cooperative Research Centre For Renewable Energy (ACRE), August 14-1998

[13] Prof. Dr-Ing. Peter Mutschler, "AC Drive With VSI", Practical Training Sz

[14] G. T. Kim And T. A. Lipo, "VSI-PWM Rectifier/Inverter System With A

Reduced Switch Count," IEEE Transactions On Industry Applications, Vol. IA-

32, No.6, Pp. 1331-1337, Nov./Dec. 1996.

[15] A. Kislovski, R. Redl, And N. SokaI, "Dynamic Analysis Of Switching-Mode

DC/DC Converters", New York: Van Nostrand Reinhold, 1994.

[16] V. Vorperian, R. Tymerski, And F. C. Lee, " Equivalent Circuit Models For

Resonant And PWM Switches", IEEE Trans. Power Electron., Vol. 4, No.2, Pp.205-214, April 1989.

[17] N. Mohan, T. Undeland, And W. Robbins, Power Electronics: Converters,

Applications, Anddesign, 2nd Ed., New York: John Wiley & Sons, 1995.

[18] Forsyth, A.J., Mollov, S.V., "Modelling And Control Of DC-DC Converters,"

Power Engineering Journal, 12(5):229-236, October 1998.

[19] D. M. Mitchell, Dc-Dc Switching Regulator Analysis, New York: Mcgraw-Hill,1988

73

[20] S. Cuk, "Basics of Switched-Mode Power Conversion: Topologies, Magnetics,

And Control, In Advances In Switched-Mode Power Conversion", Vol. 2, Pp.

279-310, Irvine: Teslaco, 1981.

[21] R. D. Middlebrook And S. Cuk, "A General Unified Approach To Modeling

Switching-Converter Power Stages," Int. J Electronics, Vol. 42, No.6, Pp. 521-550, June 1977.

[22] M. Calais, J. M. A. Myrzik, And V. G. Agelidis, "Inverters For Single Phase Grid

Connected Photovo!taic Systems--overview And Prospects,"In Proc. 17th PV

Solar Energy Conj And Exhibition, Munich, Germany, Oct. 200 I.

[23] Geoffrey R. Walker, Member, IEEE, And Paul C. Sernia," Cascaded DC-DC

Converter Connection Of Photovoltaic Modules", IEEE Transactions On Power

Electronics, Vol. 19, NO.4, Pp. 1130-1139, July 2004.

[24] H.W. Van Der Broeck, H.-C. Skudelny, And G.V. Stanke, "Analysis And

Realization Of A Pulsewidth Modulator Based On Voltage Space Vectors,"

IEEE Transactions On Industry Applications, Vo1.24, Pp. 142-150, 1988.

[25] F. Barzegar And S. Cuk, "Solid-State Drives For Induction Motors: Early

Technology To Current Research," In Proc. IEEE Region 6 Con[, Anaheim, CA,Feb. 15-18, 1982.

[26] F. Barzegar And S. Cuk, "A New Switched-Mode Amplifier Produces Clean

Three-Phase Power," In Proc. Powercon 9, 9th Int. Solid-State Power Electronics

Conj, Washington, DC, July 13-15, 1982.

[27] F. Barzegar And S. Cuk, "A Boost Dc-Ac Converter: Design, Simulation And

Implementation," In Proc. Power Electronic Brazilian Con[ (COBEP '95), Dec.

1995, Pp. 509--'514.

74

[28] C' Aceres, R., Barbi, I., " A Boost DC-AC Converter: Analysis, Design, And

Experimentation", IEEE Transactions On Power Electronics, Vol. 14, Pp. 134-

141, January 1999.

[29] C' Aceres, R., Barbi, I., "A Boost Dc-Ac Converter: Operation, Analysis, Control

And Experimentation", In Proc. Int. Conj Industrial Electronics, Control And

Instrumentation (IECON'95), Pp. 546-551, Nov. 1995.

[30] R. C' Aceres, "DC-AC Converters family, Derived From The Basic Dc-Dc

Converters," Ph.D. Dissertation, Federal Univ. Santa Catarina, Brazil, 1997 (InPortuguese).

[3 I] Cecati, C., Dell' Aquila, A. And Liserre, M., " Analysis And Control Of A

Three-Phase Dc/Ac Step-Up Converter", In Proc. IEEE I8IE'02 Conj, Pp. 850-856,July 2002.

[32] Cecati, c., Dell' Aquila, A. And Liserre, M., "A Novel Three-Phase Single-

Stage Distributed Power Inverter", IEEE Transactions On Power Electronics,

Vol. 19, Pp. 1226-1233, September 2004.

[33J Espinoza, J.R. , Power Electronics Hand Book, Edited By M.H. Rashid. San

Diego, C.A: Academic Press 2001

[34] Jang, Y., Jovanovic, M., "New Two-Inductor Boost Converter With Auxiliary

Transformer", EEE Applied Power Electronics Conference, Pp.654-660, 2002.

[35] Rivas, C., Rufer, A.," A P.W.M. Current Converter For Electric Energy

Production Systems From Fuel-Cells", European Power Electronics Conference

Proceedings, Pp. I-II, 200 I

75

Glossary

Alternating current (ac) - Electric current that regularly alternates direction. This kind

of electricity is delivered from an inverter and used by buildings and homes.

Annual solar savings - The amount of energy saved by the power generated by a solar

electric system.

Cell - A (solar) cell or photovoltaic cell is a device that converts light energy into

electrical energy.

Cell efficiency - The percentage of electrical energy that a solar cell produces

compared to the total amount of energy from the sun falling on the cell under standard

testing conditions.

Current - The flow of electricity between two points. Measured in amps.

Direct current (de) - Electrical current that flows only in one direction. This kind of

electricity is generated by a solar system and is converted into AC power by the inverter.

It is the most common form of electricity used in boats and RVs.

Efficiency - The ratio of output energy to input energy.

Electric circuit - The path followed by electricity, beginning from the generating

source, continuing through the devices that use the electricity, and then traveling back to

the source.

Electricity - The controlled flow of electrons through a conductor.

Energy - Usable power. It is measured in kilowatt-hours.

76

Energy audit - A process that determines how much energy you use in your home.

Grid - A distribution network, including towers, poles, and wires that a utility uses to

deliver electricity.

Grid-connected PV system - A solar electric system that is tied in to the utility's

network. When a solar system generates more power than a building needs at that time,

solar power is lent to the utility grid and retrieved later when it is needed.

Inverter - A device that converts the electricity generated from a solar electric system

from direct current (DC) to alternating current (AC) for use in the home.

Irradiance - The amount of solar energy that strikes a surface during a specific time

period. Measured in kilowatts (kW).

Junction box - The point on a solar panel where it connects, or is strung, to other solar

modules.

Kilowatt (kW) - A unit of electrical power, one thousand watts.

Kilowatt-hour (kWh) - A unit of electric energy, or one thousand watts acting over a

period of one hour. The consumption of electrical energy by homes is typically measured

in kilowatt-hours.

Load - Anything that is connected to an electrical circuit and draws power from that

circuit.

Megawatt (mW) - One million watts, or one thousand kilowatts.

Module - Synonym

electricity.

for solar panel, or an assembly of solar cells used to generate

Monocrystalline solar cell - A solar cell made from a thin slice of a single large crystal

ofsilicon.

Multicrystalline- A solar cell composed of many small crystals (crystallites). Because

of the numerous grain boundaries, solar cells that employ this crystal structure will

operate with lower efficiency than monocrystalline solar cells.

Panel - Synonym for solar module, or an assembly of solar cells used to generate

electricity.

Passive solar home - A house that uses part of the building as a solar collector, in

contrast to active solar generation as with a solar power system.

Peak load - This is the largest amount of electricity being used at anyone point in time

during the day.

Photovoltaic (PV) - This is the conversion of visible light into electricity. Photo means

"light", voltaic means "electric."

Photovoltaic array - Synonym for a solar system. A solar array is an interconnected

assembly of solar panels that functions as a single electricity-producing unit.

Photovoltaic cell - Synonym for solar cell; A solar cell or photovoltaic cell is a device

that converts light energy into electrical energy.

Photovoltaic module - The layers of glass, plastic, and silicon cells framed in metal,

which collect the sun's energy.

Semiconductor - A solid material such as silicon or germanium that has an electrical

conductivity between that of a conductor and an insulator. Typical semiconductors for

78

PV cells include silicon, gallium arsenide, copper

telluride.

Silicon (Si) - A chemical element that is the most common semiconductor material used

in making PV cells.

Single-crystal silicon - Silicon material with a single crystal structure. A common

material for the construction of solar PV cells.

Solar cell - A solar cell or photovoltaic cell is a device that converts light energy into

electrical energy.

Solar energy - Energy from the sun.

Solar module - see photovoltaic module.

Solar panel- see photovoltaic module.

Solar power - Electricity generated from sunlight.

Voltage (or electric potential) - The electric force that causes electric current to flow

(analogous to pressure which can cause a water current to flow in a pipe) measured in

volts (V).

Watt (W) - The unit of electric power, which is the rate of energy production, or the

amount of energy consumed at a point in time. One ampere of current flowing at a

potential of one volt produces one watt of power.

Watt-hour (Wh) - A unit of energy equal to one watt of power being used for one

hour.

79

Analysis of A PWM Boost Inverter . for Solar Home Application.

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