THD AND EFFICIENCY STUDY FOR PV GRID-CONNECTED

THD AND EFFICIENCY STUDY FOR PV GRID-CONNECTED

LAFSAH BT MAT DAUD

A report submitted in partial fulfillment of the

requirements for the award of the degree of Bachelor of

Electrical Engineering (Power System)

Faculty of Electrical Engineering

Universiti Malaysia Pahang

JUNE 2012

v

ABSTRACT

Total harmonic distortion (THD) is a measurement of the harmonic distortion

and is defined as the ratio of the sum of the powers of all harmonic components to the

power of the fundamental frequency. In general, efficiency is a measurable concept,

quantitatively determined by the ratio of output to input. The project is all about the

experimental study on THD and efficiency for photovoltaic (PV) grid connected. A

scale-down less than 1kW system will be developed and established for the study. The

impact on THD and efficiency will be assessed to the real network environment by

connected three phase motor to Variable Frequency Drives (VFD’s) as the load. The

experimental will be done by using Power Quality Analyzer (PQA) software and the

comparison between before and after connected PV will be conducted. The results of the

THD and efficiency for PV grid connected system will be obtained and analyzed under

influence of load conditions.

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ABSTRAK

Jumlah herotan harmonik (THD) adalah ukuran herotan harmonik dan

ditakrifkan sebagai nisbah jumlah kuasa semua komponen harmonik kuasa frekuensi

asas. Secara amnya, kecekapan adalah satu konsep yang diukur, yang kuantitnya

ditentukan oleh nisbah output kepada input. Tujuan kertas ini adalah kajian eksperimen

THD dan kecekapan untuk grid photovoltaic (PV) yang berkaitan. Satu skala-turun

kurang daripada 1kW sistem akan dibangunkan dan ditubuhkan untuk kajian. Impak ke

atas THD dan kecekapan akan dinilai untuk persekitaran rangkaian sebenar oleh

penyambungan tiga fasa motor kepada Pemacu Frekuensi Variabel (VFD) sebagai

beban. Eksperimen adalah dengan menggunakan Kualiti Kuasa Analyzer (PQA) dan

perbandingan di antara sebelum dan selepas penyambungan PV akan dijalankan.

Keputusan THD dan kecekapan bagi sistem grid PV yang berkaitan akan diperolehi dan

dianalisis di bawah pengaruh keadaan beban.

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TABLE OF CONTENTS

CHAPTER CONTENTS

PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF FIGURES xiii

LIST OF APPENDICES xvii

LIST OF ABBREVIATIONS

xviii

1 INTRODUCTION

1.1 Overview THD and Efficiency of

PV Grid Connected

1.2 Problem Statement

1.3 Project Background

1.4 Objective

1.5 Scope of Project

1.6 Report Outline

1

1

2

3

3

4

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2 LITERATURE REVIEW

2.1 Introduction

2.2 History of PV

2.3 Types of PV System

2.4 PV System Works

2.4.1 The Solar Cell

2.4.2 Types of PV Cell

2.4.3 Types of PV Panel

2.4.4 The PV System

2.4.5 On Grid System

2.4.6 Off Grid System

2.5 Introduction of Harmonics

2.6 Definition of THD

2.7 Definition of Efficiency in PV Grid-

Connected

2.8 Experimental evaluation that Related with

THD and efficiency in PV Grid- Connected

system

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3 METHODOLOGY

3.1 Introduction

3.2 KEWPQAMASTERV203 Software

3.3 PQA Instrument

3.4 Flowchart of the study

3.5 Block Diagram

3.6 The function of each component in block

diagram

3.6.1 PV Array

3.6.2 MPPT

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33

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34

ix

3.6.3 DC-DC converter (Boost converter)

3.6.4 Capacitor

3.6.5 Common DC Link

3.6.6 Load

3.6.7 Inverter

3.6.8 Grid-Connected System

3.7 Flowchart of the Experimental Setup

3.8 Total Harmonic Distortion

3.9 Efficiency

3.9.1 Procedure to Get The Efficiency at

Load for PV Grid-Connected

System

3.9.2 Procedure to Get The Efficiency at

PV Inverter

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4 RESULT AND DISCUSSION

4.1 Introduction

4.2 Result

4.3 Case 1: Total Harmonic Distortion (THD)

4.3.1 Comparison THD for

Frequency is 50 Hz with Speed

is 1500 rpm Before and After

Connected PV

4.3.1.1 THD at Grid

4.3.1.2 THD at Load

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50

50

50

53

x




Connected PV

4.3.2.1 THD at Grid

4.3.2.2 THD at Load




Connected PV

4.3.3.1 THD at Grid

4.3.3.2 THD at Load

4.3.4 Comparison result THD

for frequency is 50 Hz,

40 Hz and 30 Hz with speed

is 1500 rpm, 1200 rpm and

900 rpm before and after

connected PV.

4.3.4.1 THD at grid

4.3.4.2 THD at PV

4.3.4.3 THD at load

4.4 Case 2: Efficiency

4.4.1 Comparison Efficiency for



Connected PV

4.4.1.1 Efficiency at Load

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67

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77

80

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Connected PV





Connected PV



Frequency is 50 Hz, 40 Hz and

30Hz with Speed is 1500 rpm, 1400

rpm and 900 rpm Before and After

Connected PV.

4.4.5 Comparison of PV Inverter

Efficiency during No Load and

Fixed Load Conditions

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89

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93

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5 CONCLUSION

5.1 Conclusion

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6 RECOMMENDATION

6.1 Recommendation

99

REFERENCES

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xii

APPENDICES

APPENDIX A Current Harmonics result

APPENDIX B Experimental Setup

APPENDIX C Datasheet for PV Array Module

APPENDIX D Datasheet for PV inverter

APPENDIX E Schematic Drawing for Three Phase Motor

APPENDIX F Schematic Drawing for DOL Motor Starter Box

xiii

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Diagram of Grid-Connected photovoltaic system

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2.2 Direct-coupled PV systems

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2.3 Diagram of Stand-Alone PV system with battery storage powering DC and AC loads

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2.4 Diagram of photovoltaic hybrid system

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2.5 Major photovoltaic system components

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2.6 Solar cell

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2.7 Types of commercial solar cell available today

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2.8 The PV panel

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2.9 Grid connected PV system

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2.10 Comparison of linear and non-linear VI characteristic

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3.1 Instrument layout of PQA

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3.2 Flowcharts for THD and efficiency study for PV Grid-Connected

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3.3 Main components in PV grid connected system

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xiv

3.4 Flowchart of experimental setup

41

3.5 Equivalent circuit during no load test

45

3.6 Equivalent circuits during Block Rotor Test

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3.7 Emprical formulas

46

3.8 Formula and connection for Star and Delta

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3.9 Equivalent circuit of induction Machine (from test) that recommended by IEEE

47

4.1 Comparison THDV at grid for frequency is 50 Hz with speed is 1500 rpm before and after connected PV

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4.2 Comparison THDI at grid for frequency is 50 Hz with speed is 1500 rpm before and after connected PV.

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4.3 Comparison result THDV at load for frequency is 50 Hz with speed is 1500 rpm before and after connected PV.

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4.4 Comparison result THDI at load for frequency is 50 Hz with speed is 1500 rpm before and after connected PV

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4.5 Comparison result THDV at grid for frequency is 40 Hz with speed is 1200 rpm before and after connected PV.

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4.6 Comparison result THDI at grid for frequency is 40 Hz with speed is 1200 rpm before and after connected PV.

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4.8 Comparison result THDI at load for frequency is 40 Hz with speed is 1200 rpm before and after connected PV.

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4.9 Comparison result THDV at grid for frequency is 30 Hz with speed is 900 rpm before and after connected PV.

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4.10 Comparison result THDI at grid for frequency is 30 Hz with speed is 900 rpm before and after connected PV.

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4.12 Comparison result THDI at load for frequency is 30 Hz with speed is 900 rpm before and after connected PV.

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4.13 Comparison result THDV at grid for frequency is 50 Hz, 40 Hz and 30 Hz with speed is 1500 rpm, 1200 rpm and 900 rpm before and after connected PV.

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4.14 Comparison result THDI at grid for frequency is 50 Hz, 40 Hz and 30 Hz with speed is 1500 rpm, 1200 rpm and 900 rpm before and after connected PV.

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4.15 Comparison result THDV at PV for frequency is 50 Hz, 40Hz and 30 Hz with speed is 1500 rpm, 1200 rpm and 900 rpm after connected PV.

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4.16 Comparison result THDI at PV for frequency is 50 Hz, 40Hz and 30 Hz with speed is 1500 rpm, 1200 rpm and 900 rpm after connected PV.

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4.17 Comparison result THDV at load for frequency is 50 Hz, 40 Hz and 30 Hz with speed is 1500 rpm, 1200 rpm and 900 rpm before and after connected PV.

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4.18 Comparison result THDI at load for frequency is 50 Hz, 40 Hz and 30 Hz with speed is 1500 rpm, 1200 rpm and 900 rpm before and after connected PV.

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4.19 Comparison result efficiency versus time at load for frequency is 50 Hz with speed is 1500 rpm before and after connected PV.

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4.20 Comparison THDV versus efficiency at load for frequency is 50 Hz with speed is 1500 rpm before and after connected PV.

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4.21 Comparison THDI versus efficiency at load for frequency is 50 Hz with speed is 1500 rpm before and after connected PV.

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4.23 Comparison THDV versus efficiency at load for frequency is 40 Hz with speed is 1200 rpm before and after connected PV.

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4.24 Comparison THDI versus efficiency at load for frequency is 40 Hz with speed is 1200 rpm before and after connected PV.

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4.26 Comparison result THDV versus efficiency at load for frequency is 30 Hz with speed is 900 rpm before and after connected PV.

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4.27 Comparison result THDI versus efficiency at load for frequency is 30 Hz with speed is 900 rpm before and after connected PV.

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4.28 Comparison result efficiency versus time at load for frequency is 50 Hz, 40 Hz and 30 Hz with speed is 1500 rpm, 1200 rpm and 900 rpm before and after connected PV.

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4.29 Comparison result efficiency of PV inverter during no load and fixed load conditions.

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xvii

LIST OF APPENDICES

APPENDIX TITLE

PAGE

A Current Harmonics result

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B Experimental Setup

108

C Datasheet for PV Array Module

111

D Datasheet for PV inverter

114

E Schematic Drawing for Three Phase Motor

116

F Schematic Drawing for DOL Motor Starter Box

117

2

xviii

LIST OF ABBREVIATIONS

PV - Photovoltaic

DC - Direct Current

AC - Alternating Current

THD - Total Harmonic Distortion

THDI - Total Harmonic Distortion Current

THDV - Total Harmonic Distortion Voltage

PCU - Power Conditioning Unit

MPPT - Maximum Power Point Tracker

ARC - Anti-Reflective Coating

PE - Power Electronic

PWM - Pulse Width Modulation

PCC - Point Common Coupling

VFDs - Variable Frequency Drives

PQA - Power Quality Analyzer

CHAPTER 1

INTRODUCTION 1.1 Overview THD and Efficiency of PV Grid-Connected

Today, the use of Grid-Connected Photovoltaic (PV) systems has been grown to

be popular in many parts of the world. More numbers of Grid-Connected PV generators

connected to a distribution network through PV inverters can afford to cause harmonic

problems. In general, a harmonic problem can be defined as a particular disturbance,

which is created by the presence of non-linear components in the electrical system that

determines a permanent modification of the voltage and current sinusoidal wave shapes

in terms of sinusoidal components at a frequency different from the fundamental. In a

grid interconnected photovoltaic power system, the Direct Current (DC) output power of

the photovoltaic array should be converted into the Alternating Current (AC) power of

the utility power system.

Under this condition, an inverter to convert DC power into AC power is required.

A line commutated inverter uses a switching device like a commutating thyristor that

can control the timing of turn ON but cannot control the timing of turn OFF by itself.

Turn OFF should be performed by reducing circuit current to zero with the assist

2

of supplemental circuit or a source. On the other hand, a self-commutated inverter is

characterized in that it uses a switching device that can freely control the ON-state and

the OFF-state, such as an IGBT or a MOSFET. A self-commutated inverter can freely

control the voltage and the current waveform at the AC side, adjust the power factor, and

suppress the harmonic current, and is highly resistant to utility system disturbance.The

sum voltage harmonic distortion of the utility grid has been established to influence the

harmonic currents of an inverter [1].

The number of PV Grid-Connected system that connected to the utility grid has

no result to the inverter’s harmonic currents but it is not the case for load power factor.

The ordinary installation pattern of a PV Grid-Connected system consists of a PV array

and a grid connected inverter. While the inverter injects power produced from the PV

array into the utility grid, there are roughly always some types of loads receiving power

from the grid at the same moment. It is usual to ask whether the grid condition and the

local loads have influence, if any on the inverter output in addition to the irradiation

which directly affects the dc output power of the PV array. In this study, the issues of

local loads by taking into consideration the load condition at PCC on the harmonic

currents of a grid-connected inverter must be analyzed. An experimentalbefore and after

connected PV platform is prepared to measure the Total Harmonic Distortion (THD) and

efficiency values on both DC and AC sides.

1.2 Problem Statement

This study has been proposed because of the rapid growth of PV Grid-Connected

installation and it is important to explore its effects on THD and efficiency.The total

voltage harmonic distortion of the utility grid has been recognized as main factors that

can affect the harmonic currents of an inverter. At the same time, the harmonics is

majority occurs under influence of load conditions.

3

1.3 Project Background

The term “harmonics” was originated in the field of acoustics, where it was

related to the vibration of a string or an air column at a frequency that is multiple of the

base frequency [2]. A harmonic component in an AC power system is defined as a

sinusoidal component of a periodic waveform that has a frequency equal to an integer

multiple of the fundamental frequency of the system [2]. Harmonics in the voltage or

current waveform can then be conceived as completely sinusoidal components of

frequencies multiple of the fundamental frequency [2]. PV systems use inverters to get

linked to distribution networks that utilize alternative voltage. On the other hand,

harmonic currents generated by PV systems may downgrade the quality of the electrical

network and change performance of other electrical equipment. In this study, the THD

and efficiency of PV Grid-Connected system hasbeenanalyzed under influence of load

conditions by varied the frequency.

1.4 Objective The objectives for this project are stated below:

i. To measure the value of THD and efficiency at PV Grid-Connected.

ii. To obtain and analyzed THD and efficiency under influence of load

conditions by varied the frequency.

iii. To compare the experimental of THD and efficiency before and after

connected PV.

4

1.5 Scope of Project

Data has been collected at FKEE laboratory by using Power Quality Analyzer

(PQA). The harmonic and efficiency data that already get will be transferred to the

computer by using KEWPQAMASTERV203 software. The PV Grid-Connected system

configuration has been setup at FKEE laboratory. The setup consist PV array, DC to AC

inverter, load and grid system.

1.6 Report Outline

Chapter 1 discuss about the introduction, project background, objective and

scope project. Otherwise this chapter discusses more about the application and the goal

of THD and efficiency analysis.

Chapter 2 discusses more about the literature review. Besides that the history of

PV, PV system works, types of PV, introduction of harmonics, definition of THD,

definition of efficiency in PV Grid-Connected and experimental evaluation that related

with THD in PV Grid-Connected system also discuss in this chapter.

Chapter 3 focused on methodologies for determine the harmonic and efficiency

data. In addition, the flowchart about main procedure PSM 1 and PSM 2 will be

discussing more details in this chapter. MATLAB software, Power Quality Analyzer

(PQA), block diagram, PV Grid-Connected design using MATLAB, experimental setup

of PV Grid-Connected, THD and efficiency formula is also discussed with details in this

chapter.

Chapter 4 exposed about the result that displayed and analyzed. This data will

be discussing further to get the THD and efficiency study for PV Grid-Connected. The

5

THD and efficiency will be discussed and analyzed at the grid, PV and motor (load) by

varied the frequency and speed by using the Variable Frequency Drives (VFD’s).

Chapter 5 is about the conclusions for this study that have been elaborate

details.

Chapter 6 is about the recommendation for this study that have been elaborate

details.

CHAPTER 2

LITERATURE REVIEW 2.1 Introduction This chapter present about the literature review. Besides that the history of PV,

PV system works, types of PV system, introduction of harmonics, definition of THD,

definition of efficiency in PV Grid-Connected and experimental evaluation that related

with THD in PV Grid-Connected system also discuss in this chapter.

2.2 History of PV

In the late 1950s the first conventional photovoltaic cells were created, and

during the 1960s were mainly used to supply electrical power for earth-orbiting satellites

[3]. In the 1970s, improvements in industrialized, performance and excellence of PV

modules helped to decrease costs and opened up a number of opportunities for powering

7

distant terrestrial applications, including battery charging for navigational aids, signals,

telecommunications equipment and other critical, low power needs [3]. Photovoltaic

became a popular power source for consumer electronic devices, including calculators,

watches, radios, lanterns and other small battery charging applications in the 1980s.

Subsequent the energy crises of the 1970s, significant efforts also began to build

up PV power systems for residential and commercial uses both for stand-alone, remote

power as well as for utility-connected applications. Throughout the similar period,

international applications for PV systems to power rural health clinics, refrigeration,

water pumping, telecommunications, and off-grid households increased dramatically,

and remain a major portion of the present world market for PV products [3]. Nowadays,

the industry’s manufacture of PV modules is growing at approximately 25 percent

annually, and major programs in the U.S, Japan and Europe are rapidly accelerating the

accomplishment of PV systems on buildings and interconnection to utility networks [3].

2.3 Types of PV System

Photovoltaic power systems are normally classified according to their useful and

operational requirements, component configurations, and how the equipment is

connected to other power sources and electrical loads [3]. Two principles for

classifications are grid-connected or utility-interactive systems and stand-alone systems.

Photovoltaic systems can be designed to give DC and/or AC power service, can function

interconnected with or independent of the utility grid, and can be connected with other

energy sources and energy storage systems [3].

The first one type is Grid-Connected (Utility-Interactive) PV Systems. Grid-

Connected or Utility-Interactive PV systems are designed to function in parallel with

and interconnected with the electric utility grid [3]. The main component in grid-

connected PV systems is the inverter, or power conditioning unit (PCU) [3]. The PCU

converts the DC power produced by the PV array into AC power

voltage and power quality requirements of the utility grid, and automatically stops

supplying power to the grid when the utility grid is not energized

Figure 2.1 illustrates that

load demand, this allows the AC power produced by the PV system to either supply on

site electrical loads, or to back feed the grid. At

when the electrical loads are

necessary by the loads is received from t

required in all Grid-

carry on to operate and feed back onto the utility grid when the grid is

service or repair [3].

Figure 2.1

Since there is no electrical energy storage (batteries) in direct

the load only operates during sunlight hours, making these designs suitable for common

applications such as ventilation fans, water pumps, and small circulation pumps for so

converts the DC power produced by the PV array into AC power


supplying power to the grid when the utility grid is not energized [3]

illustrates that when the PV system output is greater than the on

his allows the AC power produced by the PV system to either supply on

site electrical loads, or to back feed the grid. At nighttime and throughout

when the electrical loads are larger than the PV system output, the

by the loads is received from the electric utility This safety

-Connected PV systems, and ensures that the PV system will not

to operate and feed back onto the utility grid when the grid is

Figure 2.1 Diagram of Grid-Connected Photovoltaic system [3]

Since there is no electrical energy storage (batteries) in direct


applications such as ventilation fans, water pumps, and small circulation pumps for so

8

converts the DC power produced by the PV array into AC power dependable with the


[3].

hen the PV system output is greater than the on-site

his allows the AC power produced by the PV system to either supply on-

throughout other periods

than the PV system output, the equilibrium of power

he electric utility This safety characteristic is

onnected PV systems, and ensures that the PV system will not

to operate and feed back onto the utility grid when the grid is downward for

hotovoltaic system [3]

Since there is no electrical energy storage (batteries) in direct-coupled systems,


applications such as ventilation fans, water pumps, and small circulation pumps for solar

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THD AND EFFICIENCY STUDY FOR PV GRID-CONNECTED