UNIVERSITI TUN HUSSEIN ONN MALAYSIA

BORANG PENGESAHAN STATUS TESIS

JUDUL : DETERMINE LOCATIONS AND NUMBERS OF D-STATCOM

AT THE DISTRIBUTION NETWORK FOR POWER QUALITY

MONITORING SYSTEM (PQMS).

SESI PENGAJIAN: 2008 / 2009

Saya NOOR ROPIDAH BINTI BUJAL (801001-06-5712) (HURUF BESAR)

mengaku membenarkan tesis (Sarjana Muda/Sarjana /Doktor Falsafah)* ini disimpan di Perpustakaan dengan syarat-syarat kegunaan seperti berikut:

1. Tesis adalah hakmilik Universiti Tun Hussein Onn Malaysia.2. Perpustakaan dibenarkan membuat salinan untuk tujuan pengajian sahaja.3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara

institusi pengajian tinggi.4. **Sila tandakan ( )

(Mengandungi maklumat yang berdarjah keselamatan SULIT atau kepentingan Malaysia seperti yang termaktub

di dalam AKTA RAHSIA RASMI 1972)

TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)

TIDAK TERHAD

Disahkan oleh:

___________________________ ___________________________ (TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)

Alamat Tetap: NO.C23, PST. PERKHIDMATAN EN. SHAMSUL AIZAM BIN ZULKIFLI PEKAN AWAH, ( Nama Penyelia )

28000 TEMERLOH, PAHANG DARUL MAKMUR.

Tarikh: 30 OKTOBER 2008 Tarikh: 30 OKTOBER 2008

CATATAN: * Potong yang tidak berkenaan.** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak

berkuasa/organisasi berkenaan dengan menyatakan sekali tempoh tesis ini perlu dikelaskan sebagai atau TERHAD.

Tesis dimaksudkan sebagai tesis bagi Ijazah doktor Falsafah dan Sarjana secaraPenyelidikan, atau disertasi bagi pengajian secara kerja kursus dan penyelidikan, atau Laporan Projek Sarjana Muda (PSM).

“I declared that I read this thesis and in my opinion of view this project it is

qualified in terms of scope and quality for purpose of awarding the

Bachelor’s Degree of Electrical and Electronics Engineering”

Signature : ……………………………………………

Supervisor : EN. SHAMSUL AIZAM BIN ZULKIFLI

Date : 30 OCTOBER 2008

ii

“I declare that this thesis entitled “Determine Locations and Numbers of D-STATCOM at The

Distribution Network for Power Quality Monitoring System (PQMS)” is the result of my own research

except as cited in references”

Signature : ……………………………………..

Name of Candidate : NOOR ROPIDAH BINTI BUJAL

Date : 30 OCTOBER 2008

iv

DETERMINE LOCATIONS AND NUMBERS OF D-STATCOM

AT THE DISTRIBUTION NETWORK FOR POWER QUALITY MONITORING SYSTEM (PQMS)

NOOR ROPIDAH BINTI BUJAL

A thesis submitted as partial fulfillment of the requirement for The Award of Degree

In Bachelor of Electrical Engineering with Honours

Faculty of Electrical and Electronics Engineering

Universiti Tun Hussein Onn Malaysia

NOVEMBER, 2008

iii

Dedicated to my loving family, for their endless support

iv

ACKNOWLEDGMENT

I would like to express my gratitude to all those who gave me the possibility to complete this

thesis. I am deeply indebted to my supervisor Mr. Shamsul Aizam Zulkifli whose help, stimulating

suggestions and encouragement helped me in all the time of the project for and writing of this thesis.

I also want to express my warm thanks to my friends who supported me in this work for all their

help, support, interest and valuable hints, and those who have contributed directly and indirectly in

completing this project. I really appreciate it and will forever be indebted to them.

Especially, I would like to give my special thanks to my beloved husband, Mohammad Zuhaidi

bin Mohd Noor who patient and love enabled me to complete this work.

Finally, I would like to thank those who contributed directly or indirectly towards the success of

this research study.

v

ABSTRACT

Power quality monitoring system is used to monitor the electric system

distribution network. It can provide information about power flow demand and the

quality of power. This project is to determination of locations and numbers of

Distribution Static Compensator (D-STATCOM) in 10 bus bar distribution network.

Primary purpose of D-STATCOM is to support bus voltage by injecting or absorbing the

reactive power which able to improve the power system stability. By find the optimal

numbers and locations of D-STATCOM, it reduced the numbers of D-STATCOM needs

in mitigate voltage sag problem. The modal analysis and time domain simulation are

used to determine the best location of D-STATCOM in distribution network. An

optimal numbers and locations of D-STATCOM will reduce power quality problems in

distribution system and it is cost effective solutions.

vi

ABSTRAK

Sistem pengawasan kualiti kuasa adalah digunakan untuk memantau.rangkaian

sistem pengagihan elektrik. Ia menyediakan maklumat berkenaan permintaan aliran

kuasa dan kualiti kuasa. Projek ini khusus untuk menentukan lokasi dan bilangan D-

STATCOM yang diperlukan untuk ditempatkan dalam sistem rangkain sepuluh bas.

Fungsi utama D-STATCOM adalah bagi menyokong menaiki bas voltan dengan

menyuntik atau menyerap kuasa reaktif yang berdaya bagi meningkatkan kuasa

kestabilan sistem. Dengan menentukan bilangan optimum dan lokasi D-STATCOM, ia

dapat mengurangkan bilangan D STATCOM yang diperlukan dalam rangkaian serta

dapat mengurangkan masalah voltan melendut. Analisis ragaman dan simulasi domain

masa digunakan untuk menentukan lokasi yang sesuai untuk menempatkan D-

STATCOM dalam rangkaian pengagihan. Bilangan D-STATCOM dan lokasi yang

optimum dapat mengurangkan masalah kualiti kuasa dalam sistem agihan dan ia adalah

penyelesaian yang efektif dari segi kos.

vii

TABLE OF CONTENT

CHAPTER ITEM PAGE

TITLE i

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENT vii

AUXILIARIES

(A) LIST OF TABLES x

(B) LIST OF FIGURES xi

(C) LIST OF ABBREVIATIONS xiii

(D) LIST OF APPENDICES xv

I INTRODUCTION

1.1 Research Background 1

1.2 Problem Statement 3

1.3 The Objectives of Project 4

1.4 Scope of Project 4

II LITERATURE REVIEW

2.1 Power Quality 5

2.2 Types of Power Quality Problems 6

2.2.1 Voltage Sags 6

viii

2.2.2 Power Interruptions 7

2.2.3 Voltage Flicker 8

2.2.4 Voltage Swell 8

2.2.5 Transient 9

2.2.6 Harmonics 10

2.3 Power Quality Monitoring System (PQMS) 10

2.4 Distribution network configurations 12

2.5 Static Compensator (STATCOM) 13

2.6 STATCOM Configuration 14

2.7 STATCOM V-I Characteristic 16

2.8 Distribution Static Compensator (D-STATCOM) 17

2.9 Determination of Location and Number Of D-

STATCOM 18

2.9.1 Modal Analysis 18

2.9.2 Time-Domain Simulation 20

2.9.3 Particle Swarm Optimization (PSO) 20

2.9.4 Voltage Stability Criteria 21

2.10 PSCAD/EMTDC Simulation Tool 23

III METHODOLOGY

3.1 Network Design 25

3.1.1 The Distribution System for Simulation 27

3.1.2 Converting One Line Diagram Network to

Electrical Network 27

3.1.3 Design of the Proposed D-STATCOM 33

3.1.4 Selection of Power Electronic Switches 33

3.2 Simulation and Testing 35

ix

3.2.1 D-STATCOM Power Quality Mitigation

Strategies 35

3.2.2 Voltage Sags Simulation Model 36

3.2.3 Voltage Sag Calculation 36

3.2.4 Voltage Sag Control Strategies 37

3.3 Bus Bar Selection 40

3.3.1 Modal Analysis 40

3.3.2 Installation of D-STATCOM 41

IV RESULT AND ANALYSIS

4.1 Result of Simulation Network without D-STATCO 42

4.2 Result of Simulation Network with D-STATCOM 45

4.2.1 D-STATCOM at Bus bar A 45

4.2.2 D-STATCOM at Bus bar B 47

4.2.3 D-STATCOM at Bus bar C 49

4.3 D-STATCOM Allocated at Main Bus bar for Voltage

Sag Compensation 51

4.3.1 D-STATCOM Allocated at Main Bus bar A 51

4.3.2 D-STATCOM Allocated at Main Bus bar B 55

4.3.3 D-STATCOM Allocated at Main Bus bar C 59

V CONCLUSION AND FUTURE WORK

5.1 Conclusion 63

5.2 Future Work 65

REFERENCES 66

APPENDICES 70

x

LIST OF TABLES

TABLES TITLE PAGE

3.1 Active (P) and Reactive (Q) Power for Each Bus Bar 29

3.2 Grouping of Main Busbar 35

5.1 Summary of Network Simulation 64

xi

LIST OF FIGURE

FIGURE TITLE PAGE

2.1 Voltage sags 7

2.2 Power interruptions 8

2.3 Voltage flicker 9

2.4 Voltage Swells 10

2.5 Transient 10

2.6 Harmonic Voltage Distortion 11

2.7 Power Quality Monitoring Process 12

2.8 General Arrangement of STATCOM 15

2.9 Connection of the STATCOM with AC system 16

2.10 The V-I Characteristic of the STATCOM 17

2.11 V-P Curve and Point of Collapse (Nose) 20

2.12 Voltage Stability to Study 23

2.13 Voltage Recovery Criteria 23

3.1 Determine Location of D-STATCOM 26

3.2 Network Design Using PSCAD 31

3.3 Electrical Distribution network 32

3.4 6-Pulses STATCOM Configuration 33

3.5 Selection of Power Switches 34

3.6 The Complete Layout of the System under Study with D-STATCOM 34

3.7 Fault Component Connected In Shunt to the System 36

3.8 Example of Voltage Sag 36

3.9 Voltage Control Loop 37

3.10 SPWM Technique

xii

(a) Generation of PWM Carrier Signals 38

(b) Generation of Reference Sine Waveform 39

3.11 Interpolated Firing Pulses Component for 6-Pulse Converter 39

4.1 The Distribution System without D-STATCOM 43

4.2 (a) Per-unit Voltage (b) Voltage drop at Main bus bar A 44

(c) Voltage drop at Main bus bar B

(d) Voltage drop at Main bus bar C

4.3 The Distribution System with D-STATCOM at bus bar A 45

4.4 (a) Per-unit Voltage (b) Voltage drop at Main bus bar A 46

(c) Voltage drop at Main bus bar B

(d) Voltage drop at Main bus bar C

4.5 The Distribution System with D-STATCOM at bus bar B 47

4.6 (a) Per-unit Voltage b) Voltage drop at Main bus bar A 48

(c) Voltage drop at Main bus bar B

(d) Voltage drop at Main bus bar C

4.7 The Distribution System with D-STATCOM at bus bar C 49

4.8 (a) Per-unit Voltage (b) Voltage drop at Main bus bar A 50

(c) Voltage drop at Main bus bar B

(d) Voltage drop at Main bus bar C.

4.9 Load Voltage a) without D-STATCOM b) with D-STATCOM 51

c) Time of Recovery Load Voltage

4.10 Plot of Voltage Time Recovery 52

4.11 Load voltages at bus bar A, B and C without and with D-STATCOM 54

4.12 Load Voltage a) without and With D-STATCOM, Time of Recovery 55

4.13 Plot of Voltage Time Recovery 56

4.14 Load voltages at bus bar A, B and C; without D-STATCOM; with D-

STATCOM 58

4.15 Load Voltage a) without, With D-STATCOM and Time of Recovery 59

4.16 Plot of Voltage Time Recovery 60

4.17 Load voltages at bus bar A, B and C without D-STATCOM and with D-

STATCOM 62

xiii

LIST OF ABBREVIATIONS

PSCAD - Power System Computer Aided Design

EMTDC - Electromagnetic Transient including DC

FFT - Fast Fourier Transform

AC - Alternating Current

STATCOM - Synchronous Static Compensator

DFT - Discrete Fourier Transform

VSC - Voltage Source Converter

GTO - Gate Turn-off Transistor

IGBT - Insulated Gate Bipolar Transistor

Y-Y - Wye-Wye

Y- - Wye-Delta

DC - Direct Current

SPS - Static Phase Shifter

DFFT - Discrete Fast Fourier Transform

IEEE - The Institute of Electrical and Electronics Engineers

p.u - Per-Unit

HID - High Intensity Discharge

PLCs - Programmable Logic Functions

ASDs - Autism Spectrum Disorders

CAD - Computer Aided Design

HVDC - High Voltage DC Transmission

FACTS - Flexible AC Transmission Systems

SVC - Static VAR Compensator

PWM - Pulse Width Modulation

R - Resistor

L - Inductor

CDC - Direct Current Capacitor

xiv

SCR - Silicon Controlled Rectifier

BJT - Bipolar Junction Transistor

MOSFET - Metal Oxide Semiconductor Field Effect Transistor

MCT - Mos-Controlled Thryistor

PSM - Projek Sarjana Muda

SPWM - Sinusoidal Pulse Width Modulation

VSC - Voltage Sourced Converter

PI - Proportional Integral

PLL - Phase Locked Loop

THD - Total Harmonic Distortion

xv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A 1. Gantt Chart for PSM 1 71

2. Gantt Chart for PSM 2 73

B 1. Distribution Network System Of Parit Raja, Batu Pahat, Johor 75

2. Circuit Used for Simulation

(a) Layout of Distribution System without D-STATCOM 76

(b) Layout of Distribution System with D-STATCOM 77

CHAPTER I

INTRODUCTION

This section describes the introduction of the research work. It will start with some

background on the research work. Then, the solution of the problems will be

discussed through the device will be selected. Next the statement of problem,

objectives, scope and importance of the research are explained.

1.1 Research Background

Power quality is the Quality of electrical energy supplied and it refers to ability of

utilities to provide electric power without interruption [1]. In recent years, due to

increase in critical load an electronic device, customers require high level power

quality than before. Sensitive equipment and non-linear loads are now in more

common places in both the industrial commercial sectors and the domestic

environment.

2

In a changing electric industry, monitoring power supply and power quality are

critical to ensure an optimal performance of power systems. Power Quality Monitoring

(PQM) can provide information about power flow and demand, and the quality of the

power [13]. It is also can be a vital diagnostic tool, identifying problem conditions on a

power network before it can cause disturbances or interruptions. With the electric

industry undergoing change, increased attention is being focused on power supply

reliability and power quality. One of the most critical elements is to ensure the

reliability for monitoring the power system performance. It can even help identify

problem conditions on a power system before they cause interruptions or disturbances.

Effective monitoring programs are important for power reliability assurance for both

utilities and customers. The most common power quality problems are voltage sags,

harmonics, voltage swell, power interruptions and voltage flicker [2].

Reactive power compensation is an important issues in electrical power systems

where flexible AC transmission system (FACTS) devices play an important roll in

controlling the reactive power flow to the power network and hence, the system voltage

fluctuations and stability. Static synchronous compensator (STATCOM) is a member of

FACTS family that is connected in shunt with the system. In distribution system, it is

also known as Distribution static compensator (D-STATCOM). Primary purpose of D-

STATCOM is to support bus voltage by injecting or absorbing reactive power and it

capable in improving the power system stability [3]. It also can eliminate the harmonic

distortion and commonly located at every critical load in distribution system. An

optimal number and location of D-STATCOM will reduce or eliminate power quality

problems in distribution system. The project is determining the optimal number of D-

STATCOM and decides its locations in the selected distribution network.

3

1.2 Problem Statement

Electrical systems are subject to a wide variety of power quality problems such

as voltage sags, power interruptions, harmonic and voltage flicker. D-STATCOM is one

of the solutions of power quality problems. Distribution Static Compensator (D-

STATCOM) is the static device of the rotating synchronous condenser and it generate or

absorb reactive power at a faster rate [3]. It used for the dynamic compensation of

power transmission and distribution system to provide a reactive power compensation

and voltage regulation at the point of connection. Recent days, STATCOM commonly

located at every critical load in distribution system and it will increase the power quality

monitoring cost.

In the past, the determination was performed manually by power quality experts.

The experts installed the monitors according to their own guidelines and knowledge on

power quality and system topology. Commonly, D-STATCOM should be installed at all

critical loads [8]. However this is not feasible in economic terms. Thus, optimal

locations for STATCOM installation must be carefully selected for maximum efficiency.

It has been proved that the centre or midpoint of a transmission line is the optimal

location for shunt FACTS devices or reactive power support and the proof is based on

the simplified line model.

The validity of the above optimal location of shunt FACTS devices is

investigated, when the actual model of the line is considered. It is found that the FACTS

device needs to be placed slightly off-centre to get the highest possible benefit [4]. Both

the power transfer capability and stability of the system can further be improved if the

shunt FACTS device is placed at the new optimal point instead of at the midpoint of a

line having some resistance. In a large metropolitan area [4], modal analysis and time

domain simulations are used to determine the best location for STATCOM. Application

4

of Particle Swarm Optimization (PSO) also one of the technique to find optimal location

of Flexible AC Transmission System (FACTS) devices to achieve maximum system

load ability with minimum cost of installation of FACTS devices [5].

1.3 The Objectives Of This Project Are:

i. To apply D-STATCOM at the distribution network.

ii. To determine the numbers of D-STATCOM need for Power Quality

Monitoring System (PQMS).

iii. To determine the best location of STATCOM in distribution network.

1.4 Scope of Project

Scope of project is to determine the locations and numbers of D-STATCOM in

the five busbar distribution network.

1.5 Expected Result

At the end of this project, it been expected that can define the locations and

numbers of D-STATCOM need in research distribution network area.

5

CHAPTER II

LITERATURE REVIEW

This Chapter represents information gathered from published literature regarding Power

System Quality.

2.1 Power Quality

Power quality is Quality of electrical energy supplied. It used to describe electric

power that motivates an electrical load and the load's ability to function properly with

that electric power [13]. Without the proper power, an electrical device (or load) may

malfunction, fail prematurely or not operate at all.

6

2.2 Types of Power Quality Problems

There are many ways in which electric power can be of poor quality and many

more causes of such poor quality power. The most common power quality problems are

voltage sags, harmonics, voltage swell, power interruptions and voltage flicker [1].

2.2.1 Voltage Sags

Voltage sags are the most common power problem encountered. Sags are a short-

term reduction in voltage, and can cause interruptions to sensitive equipment such as

adjustable-speed drives, relays, and robots [1]. Sags are most often caused by fuse or

breaker operation, motor starting, or capacitor switching. Voltage sags typically are non-

repetitive, or repeat only a few times due to recloser operation. Sags can occur on

multiple phases or on a single phase and can be accompanied by voltage swells on other

phases [12]. Voltage Sag affect machine or process downtime, scrap cost, clean up costs,

product quality and repair costs all contribute to make these types of problems costly to

the end-user.

Figure 2.1: Voltage Sags

7

There are many reasons which cause the voltage sag to occur. Some of the

causes are shown below [14].

Motor start-ups

Sudden increase in the line loads

Electrical faults on utility power lines caused by animals, trees, or other objects

in contact with the power lines

Electronic loads which pull large currents such as copy machine and laser printer

Loose wiring

Short circuit in the system

2.2.2 Power Interruptions

Power interruptions are zero-voltage events that can be caused by weather,

equipment malfunction, recloser operations, or transmission outages. Interruptions can

occur on one or more phases and are typically short duration events, the vast majority of

power interruptions are less than 60 seconds [12].

Figure 2.2: Power Interruptions

8

2.2.3 Voltage Flicker

Voltage flicker is rapidly occurring voltage sags caused by sudden and large

increases in load current [1]. Voltage flicker is most commonly caused by rapidly

varying loads that require a large amount of reactive power such as welders, rock-

crushers, sawmills, wood chippers, metal shredders, and amusement rides. It can cause

visible flicker in lights, visual irritation and cause other processes to shut down or

malfunction. Susceptibility to flicker depends on the stiffness of the supply system. So

flicker is more common on lower-voltage systems and at the ends of long circuits [12].

Figure 2.3: Voltage Flicker

2.2.4 Voltage Swell

A voltage swell is increases in the RMS voltage that sometimes accompany

voltage sags [12]. They appear on the unfaulted phases of a three phase circuit that has

developed a single-phase short circuit. They also occurs following load rejection. Swells

can upset electric controls and electrics motor drives, particularly common adjustable-

speed drive, which can trip because of their built-in protective circuitry. Swells may also

9

stress delicate computer components and shorten their life. It was caused by system

faults, load switching and capacitor switching [1].

Figure 2.4: Voltage Swell

2.2.5 Transient

Voltage disturbances shorter than sags or swell are classified as transient and

caused by sudden changes in the power system [12]. It is an undesirable momentary

deviation of the supply voltage or load current. Transients are generally classified into

two categories which are impulsive and oscillatory. Transient effect tripping,

component failure, hardware reboot required, software ‘glitches’ and poor product

quality

Figure 2.5: Transient

10

2.2.6 Harmonics

Harmonics are periodic sinusoidal distortions of the supply voltage or load

current caused by non-linear loads [12]. Harmonics are measured in integer multiples of

the fundamental supply frequency. Using Fourier series analysis the individual

frequency components of the distorted waveform can be described in terms of the

harmonic order, magnitude and phase of each component. Figure 2.6 show the

limitation of low-frequency effects generated by mains connected appliances [1]. The

effects of harmonics and flicker are looked at and the regulatory regime which aims to

limit mains borne harmonic distortion is examined. Transformer and neutral conductor

heating leading to reduced equipment lifespan; audio hum, video ‘flutter’, software

glitches and power supply failure.

Figure 2.6: Harmonic Voltage Distortion

2.3 Power Quality Monitoring System (PQMS)

Power quality monitoring system is the cornerstone of power quality analysis [2],

diagnosis and improvement. Power Quality (PQ) measurement concepts are evolving

from instantaneous metering to continuous monitoring and recent developments in

11

measurement technology make PQ monitoring system more powerful. Proposed system

basically consists of one PQ analyzer and multiple PQ meters. PQ meter only acts as raw

data acquisition system and PQ analyzer performs all calculations and analysis

algorithm. The proposed system is very economical especially for large-scale system

because the price of Power Quality meter can be dramatically lowered in this scheme.

PQ measurement systems have many variations in their structure, price and function.

PQ monitoring falls into two categories [13]. One is event which includes

instantaneous RMS voltage variations (e.g. sag, swell, interruption) and transients. The

other is steady-state trend such as overvoltage, undervoltage, frequency, unbalance,

harmonic distortion and flicker [1].

Figure 2.7 shows the process of PQ monitoring. It is composed of four steps. At

the first step (Data Acquisition), the line voltages and currents are measured, sampled

and converted to digital signals. At the second step (Characterizing), the basic

characteristics such as RMS values of voltage and current, harmonic components and

frequency are calculated using various signal processing algorithms. At the third step

(PQ Analysis), the basic characteristics are analyzed and PQ events are detected. Finally

at the fourth step (Statistical Analysis), the PQ trends and events are analyzed in a

statistical manner and PQ indices are calculated. A/D converters are used to convert line

voltages and currents into digital signals [13].

Figure 2.7: Power Quality Monitoring Process

12

2.4 Distribution Network Configurations

Distribution networks are typically of two types, radial or interconnected. A

radial network leaves the station and passes through the network area with no normal

connection to any other supply [16]. This is typical of long rural lines with isolated load

areas. An interconnected network is generally found in more urban areas and will have

multiple connections to other points of supply. These points of connection are normally

open but allow various configurations by the operating utility by closing and opening

switches. Operation of these switches may be by remote control from a control centre or

by a lineman.

The benefit of the interconnected model is that in the event of a fault or required

maintenance a small area of network can be isolated and the remainder kept on supply.

Within these networks there may be a mix of overhead line construction traditional

utility poles and wires and, increasingly, underground construction with cables and

indoor or cabinet substations. However, underground distribution is significantly more

expensive than overhead construction. In part to reduce this cost, underground power

lines are sometimes co-located with other utility lines in what are called common utility

ducts. Distribution feeders emanating from a substation are generally controlled by a

circuit breaker which will open when a fault is detected. Automatic Circuit Reclosers

may be installed to further segregate the feeder thus minimizing the impact of faults.

Long feeders experience voltage drop requiring capacitors or voltage regulators to be

installed.

13

2.5 Static Compensator (STATCOM)

A STATCOM or Static Compensator is a member of the FACTS family of

devices used on alternating current electricity transmission networks. A STATCOM is a

power electronic voltage-source converter based device that can act as either a source or

sink of reactive AC power to an electricity network and if connected to a source of

power can also provide active AC power. Usually a STATCOM is installed to support

electricity networks that have a poor power factor and often poor voltage regulation.

There are a number of other uses for STATCOM devices including, wind energy

voltage stabilization, and harmonic filtering. It also maybe used for the dynamic

compensation of power transmission system, providing voltage support and increased

transient stability margins. However, the most common use is for voltage stability [3].

The general arrangement of STATCOM is shown in figure 2.8. The static

compensator (STATCOM) provides shunt compensation in a similar way to static VAR

compensators (SVC) but utilizes a voltage source converter rather than shunt capacitors

and reactors. The basic principle of operation of STATCOM is generation of a

controllable AC voltage source behind a transformer leakage reactance by a voltage

source converter connected to a DC capacitor. The voltage difference across the

reactance produce active and reactive power exchanges between the STATCOM and

power system [3].

14

Figure 2.8: General Arrangement of STATCOM

2.6 STATCOM Configuration

The most basic configuration of STATCOM consists of two-level Voltage

Source Converter (VSC) with a DC energy storage device, a coupling transformer

connected in shunt with the AC system and the associated control circuits [3]. Figure

2.9 depicts the schematic diagram of the STATCOM. The DC energy storage device

may be a battery, whose output voltage remains constant or it may be a capacitor whose

terminal voltage can be raised or lowered by inverter control in such a way that is stored

energy is either increased or decreased.

The VSC converts the DC voltage across the storage device into a set of three

phase AC output voltages that are in phase and coupled with the AC system through the

reactance of coupling transformer. A key characteristic of this controller is that the

15

active and reactive powers exchanged between the converter and the AC system can be

controlled by changing the phase angle between the converter output voltage and the bus

voltage at the point of common coupling [3].

Figure 2.9: Connection of the STATCOM with AC System.

The main advantages of STATCOM over the conventional Static VAR

Compensator (SVC) [10] are:

i. Significant size reduction due to reduced number of passive elements.

ii. Ability to supply required reactive power even at low voltages.

iii. Greater reactive power current output capability at depressed voltages.

iv. STATCOM exhibits faster response and better control stability.

v. With proper choice of design ratings and thermal design, STATCOM can

have short time overload capability. This is not possible in SVC due to its

inherent susceptance limit support.

vi. Independent from actual voltage on the connection point.

vii. High density, advanced power converters

16

2.7 STATCOM V-I Characteristic

The STATCOM can be operated in two different modes [11]:

i. In voltage regulation mode (the voltage is regulated within limits as explained

below)

ii. In Var control mode (the STATCOM reactive power output is kept constant)

When the STATCOM is operated in voltage regulation mode, it implements the

following Voltage versus Current (V-I) characteristic. Figure 2.10 show the V-I

characteristic of STATCOM. The STATCOM can supply both the capacitive and the

inductive compensation and is able to independently control its output current over the

rated maximum capacitive or inductive range irrespective of the amount of ac-system

voltage. The STATCOM can provide full capacitive-reactive power at any system

voltage. This capability is useful for situations in which the STATCOM is needed to

support the system voltage during and after faults where voltage collapse would

otherwise be a limiting factor.

Figure 2.10: The V-I Characteristic of the STATCOM

From the figure 2.10[11], as long as the reactive current stays within the

minimum and minimum current values (-Imax, Imax) imposed by the converter rating,

the voltage is regulated at the reference voltage Vref. However, a voltage droop is

17

normally used (usually between 1% and 4% at maximum reactive power output), and the

V-I characteristic has the slope indicated in the figure. In the voltage regulation mode,

the V-I characteristic is described by the following equation:

where,

V - Positive sequence voltage (pu)

I - Reactive current (pu/Pnom) (I > 0 indicates an inductive current)

Xs - Slope or droop reactance (pu/Pnom)

Pnom- Three-phase nominal power of the converter

2.8 Distribution Static Compensator (D-STATCOM)

When used in low-voltage distribution systems, the STATCOM is normally

identified as Distribution STATCOM (D-STATCOM). It operates in a similar manner

as the STATCOM (FACTS controller), with active power flow controlled by the angle

between the AC system and VSC voltages and the reactive power flow controlled by the

difference between the magnitudes of these voltages [3]. As with the STATCOM, the

capacitor acts as the energy storage device and its size is chosen based on power rating,

control harmonics considerations. The D- STATCOM controller continuously monitors

the load voltages and currents and determines the amount of compensation required by

the AC system for a variety of disturbances. The VSC connected in shunt with the ac

system provides a multifunctional topology which can be used for up to three quite

distinct purposes:

i. voltage regulation and compensation of reactive power;

ii. Correction of power factor;

iii. Elimination of current harmonics.

18

The D-STATCOM has plenty of applications in low-voltage distribution systems

aimed to improve the quality and reliability of the power supplied to the end-user. It can

be used to prevent non-linear loads from polluting the rest of the distribution system.

The rapid response o the D- STATCOM makes it possible to provide continuous and

dynamic control of the power supply including voltage and reactive power

compensation, harmonic mitigation and elimination of voltage sags and swells [6].

2.9 Determination Of Location And Number Of STATCOM

In order to determine the best location for these devices, there are three currently

methods that commonly used. They are Modal analysis, time domain simulations and

Particle Swarm Optimization.

2.9.1 Modal Analysis

A good correlation was found between Modal analysis and Time domain

simulation. Voltage stability studies comprise different techniques which are voltage

versus power (V-P) and reactive power versus voltage (Q-V) curve analysis, modal

analysis and time domain simulation [7]. Application of one or more of these techniques

will determine those buses or zone in the power system that show a tendency to voltage

instability or collapse and will show the effectiveness of the solution applied.

19

Contingencies that are critical to voltage stability, as well as buses that have a

strong participation in a potential voltage collapse, are determined with a combination of

both modal analysis and time-domain simulations. In Modal Analysis Application, the

main steps in carrying out a modal analysis are [4]:

1. Determine, for all credible contingencies, at transmission and sub

transmission levels, V-P curves for those buses considered critical to the

system or preferably, for all buses.

2. From V-P curves obtained in step 1, perform modal analysis as close to

the nose of the curve as possible [16](with today’s computer capabilities,

software packages are able to perform these steps expeditiously).

3. From modal analysis, contingencies that result in critical modes negative

eigen values or positive eigen values close to zero are identified. These

contingencies are called “critical contingencies”. From these

contingencies, bus participation is determined.

Figure 2.11: V-P Curve and Point of Collapse (Nose).

20

2.9.2 Time-Domain Simulation (Dynamic Analysis)

In Time-Domain Simulation (Dynamic Analysis), the simulations are carried out

with the following considerations [4]:

1. Test all critical contingencies determined in modal analysis and identify

the reason the voltage stability criteria is not met.

2. List all critical contingencies by voltage level, specifying their voltage

criteria violation.

It is worthwhile noting that all critical contingencies determined by modal

analysis were found to be critical as well in dynamic analysis, since all of them failed to

meet at least one characteristic of the voltage stability criteria [4].

2.9.3 Particle Swarm Optimization (PSO)

Particle swarm optimization (PSO) is a technique to for handling the

optimization problems. PSO technique is used to determined optimal location of

STATCOM for power quality improvement. The power transfer capability and transient

stability of the system can be improved by locating STATCOM slightly off-center

towards the sending end instead of the mid-point [5]. PSO is employed to search for the

location of STATCOM where the value of objective function is minimum. The problem

constraints are the location bounds. Therefore, the design problem can be formulated as

minimize objective function (J) and subject to Lmin ≤ L ≤ Lmax where L is the length

of the line section from the sending-end to the location of STATCOM. The following

21

steps are followed to search for optimal location of STATCOM to improve transient

stability or reduce voltage sag and harmonics [5].

1. Initially set the fault clearing time (Tfc) to a high value so that the system

is unstable at all locations of STATCOM.

2. Employed PSO to minimize the objective function.

3. Check for stability of the system.

4. If the system is unstable, decrease Tfc by a small step and repeat from

step 2 or stop if the system is stable.

The system is stable at Tfc = Tfcf only if the STATCOM is placed at optimal

location obtained by the above method for Tfc> Tfcf, the system become unstable at all

location [5].

2.9.4 Voltage Stability Criteria

As the results from time-domain simulations [6], the following voltage stability

criteria is used and presented in figures 2.11 and figure 2.12. Referring to figure 2.12,

after the fault is cleared, transient post-contingency voltage should not drop below 80%

of its initial value, and resulting oscillations should not exceed 20 cycles. Voltage below

this 80% value significantly increases the risk of voltage collapse: Industrial motor load

will stall, drawing increasing reactive current and bringing voltages down on nearby

motors and capacitors. Once voltage is recovered, its post-transient magnitude should

not fall below 0.9 p.u[4].

22

Figu

re 2.12: Voltage Stability to Study

Figure 2.13: Voltage Recovery Criteria

23

2.10 PSCAD/EMTDC Simulation Tool

PSCAD/EMTDC is an industry standard simulation tool for studying the

transient behavior of electrical networks [3]. Its graphical user interface enables all

aspects of the simulation to be conducted within a single integrated environment

including circuit assembly, run-time control, analysis of results, and reporting. Its

comprehensive library of models supports most ac and dc of power plant components

and controls, in such a way that FACTS, custom power, and HVDC systems can be

modeled with speed and precision.

It provides a powerful resource for assessing the impact of new power

technologies in the power network. Simplicity of use is one of the outstanding features

of PSCAD/EMTDC. It’s great many modeling capabilities and highly complex

algorithms and methods are transparent to the user, leaving him free to concentrate his

efforts on the analysis of results rather than on mathematical modeling.

For the purpose of system assembling, the user can either use the large base of

built-in components available in PSCAD/EMTDC or to its own user-defined models.

To show the effectiveness and simplicity of the proposed models, the ac network

modeling capabilities of PSCAD/EMTDC are simplified as much as practicable, such

that standard features such as synchronous generator, transformer saturation, and

frequency-dependent transmission line and cable models are not used in test circuits.

CHAPTER III

METHODOLOGY

This chapter describes the design of the 11kV distribution system. The project is

divided into three phases in order for project to be completed systematically. It is

included of designing, simulating and analysis. Selection of switches, devices and other

components is verified in this chapter. Mathematical formulas used to calculate

component’s value are also presented. The designed distribution system is subjected to

the effect of D-STATCOM in mitigating the voltage sag in the distribution network. The

following are the details for each phase.

3.1 Network Design

Network design involved of collecting and researching material information for the

project. The distribution network was obtained from Tenaga Nasional Berhad, Batu

Pahat, Johor. All the information that related to the project will be discussed and

analyzed. The results of the discussion are used in developing the project. The second

phase involved the simulation of the network circuit to obverse the voltage sag occurred

at each bus bar under study. Then D-STACOM was allocated at each bus bar in

sequence to see the effects. The third phase is about selecting the best location and

25

numbers of D-STATCOM in the distribution network. The circuit is designed using

PSCAD. The conversion of network from single line diagram to electrical network and

overall project design is presented. The overall flows of the determination of location

and numbers of D-STATCOM is given by the flow chart in figure 3.1.

Figure 3.1: Determine Location of D-STATCOM

26

3.1.2 The Distribution System for Simulation.

The distribution network in Parit Raja, Batu Pahat, Johor was chooses under this

study. This distribution network involves ten busbar and received 11kV from Main

Entrance Sub- Station (MES) Parit Raja. The layout for the system under study is as

shown in appendix A.

3.1.3 Converting One Line Diagram Network to Electrical Network.

The distribution network in obtained from Tenaga National Berhad is in the form

of single line diagram. The single line diagram was converted to electrical network

using mathematical formulas in order to simulate is PSCAD. The calculations for active

power (P), reactive power (Q) and load impedances i.e load resistance(R) and load

inductance (L) are done. For three phase loads, the active power (P) was considered as

load resistance (R) and reactive power (Q) was considered as load inductance (L).

The loads was calculated for each bus bar and the three phase voltage (VL-L )

from Main Entrance Sub-Station(MES) is 11kV and Apparent power (S) equal to

30MVA.

The Apparent power (S) is given by,

S = VI (3.1)

27

The active power (P) is given by,

P = S cos θ (3.2)

Where S is apparent power and θ is the power factor angle. In Malaysia, minimum

power factor is Cos θ = p.f = 0.85 which θ = 31.79°.

The reactive power is given by,

Q = P tan θ (3.3)

Where cos θ = 0.85.

The load resistance and inductance are given by,

P

VR

2

(3.4)

Q

VX L

2

(3.5)

Where XL = 2πfL which f is standard frequency equal to 50Hz.

Power and reactive power at each bus bar determine as shown in table 2.

28

Table 3.1: Active (P) and Reactive (Q) Power for each bus bar.

No. of Bus bar Active power ( P ) Reactive power ( Q )

Bus bar 1

cos

800

SP

kVAS

= 800kVA(0.85)

= 680kW.

tanPQ

= 680kW[tan (31.79°)]

= 421kVar.

Bus bar 2

No Load

P = 0kW

Q = 0kVar.

Bus bar 3

cos

500

SP

kVAS

= 500kVA(0.85)

= 425kW.

tanPQ

= 425kW[tan (31.79°)]

= 263kVar.

Bus bar 4

cos

4100

SP

kVAS

= 4100k (0.85)

= 3485kW.

tanPQ

= 3485kW[tan (31.79°)]

= 2160kVar.

Bus bar 5

cos

1000

SP

kVAS

= 1000kVA(0.85)

= 850kW.

tanPQ

= 850kW[tan (31.79°)]

= 527kVar.

Bus bar 6

cos

3200

SP

kVAS

= 3200kVA(0.85)

= 2720kW.

tanPQ

= 2720kW[tan (31.79°)]

= 1686kVar.

29

No. of Bus bar Active power ( P ) Reactive power ( Q )

Bus bar 7

(a)

cos

1600

SP

kVAS

= 1600kVA(0.85)

= 1360kW.

tanPQ

= 1360kW[tan (31.79°)]

= 843kVar.

Bus bar 8

(b)

cos

1050

SP

kVAS

= 1050kVA(0.85)

= 892.5kW.

tanPQ

= 892.5kW[tan (31.79°)]

= 553kVar.

Bus bar 9

cos

3200

SP

kVAS

= 3200kVA(0.85)

= 2720kW.

tanPQ

= 2720kW[tan (31.79°)]

= 1686kVar.

Bus bar 10

cos

8300

SP

kVAS

= 8300kVA(0.85)

= 7055kW.

tanPQ

= 7055kW[tan (31.79°)]

= 4373kVar.

The load data in electrical network for the distribution system were used in

design in PSCAD. The circuit design using PSCAD is shown in figure 3.2.

30

Figure 3.2: Network Design Using PSCAD

31

The design begin with create a new file in PSCAD. The circuit was draw start

from bus bar one to bus bar seven. The three phase source and loads are converted to

single line diagram. Voltmeter and ammeter are placed at each bus bar to measure the

voltage and current. Then, the circuit is simulated. If the simulation is success, the

same process is repeated for bus bar eight to fifteen. If the simulations fail, the

correction has to make to the design of bus bar one to seven until the simulation is

success. Output voltage at each bus bar is observed using graph control and voltage sag

is identified. The complete circuit design is shown in figure 3.3.

Figure 3.3: Electrical Distribution network

32

3.1.1 Design of the Proposed D-STATCOM

Figure 3.4: 6-Pulse STATCOM Configuration.

The D-STATCOM is connected in shunt to the distribution system via step down

transformer. Figure 3.4 show the configuration of 6-Pulse D-STATCOM. There are six

power electronic switches which act as six-pulse inverter connected to step down

transformer.

3.1.2 Selection of Power Electronic Switches.

In the library of the PSCAD software, there is a selection of power switches

namely the thyristor, diode, Gate-turn off (GTO), IGBT and transistor. Figure 3.5 shows

the selection of power switches. Power electronic switches that are used in the

simulation are the Gate Turn-off thyristors, widely known as GTO. The selection is due

to its turn-off capability. With and adequate turn-on pulse, the GTO rapidly turns off

and recovers to withstand the forward voltage and be ready for the next turn-on

pulse[14].

33

Figure 3.5: Selection of Power Switches

GTO are available up to 4000V, 3000 A. The switching frequency can go up to

10 kHz and switching time is 15μs [14]. Other advantages are reduction in acoustic and

electromagnetic noise due to elimination of communicating chokes and improved

efficiency of converter [14]. The disadvantage of GTO is switching losses due to high

switching frequency. Adding snubber circuit to GTO can reduce this. The complete

11kV distribution system with the insertion of D-STATCOM is illustrated in figure 3.6.

Figure 3.6: The Complete Layout of the System under Study with D-STATCOM.

34

3.2 Simulation And Testing

The design network is simulated to monitor the graph of load voltage (V) in term

of per-unit at selective bus bar. The results from simulation and testing are used in

process to decide the best location of D-STATCOM for the network. The distribution

network is divided into three main bus bar which are main bus bar A, main bus bar B

and main bus bar C and the grouping of buses is shown in table 2.1.

Table 3.2: Grouping of Main Busbar

Main Busbar No. of Bus

A Busbar 1, Busbar 2, Busbar 3, Busbar 4

and Busbar 6

B Busbar 7 and Busbar 8

C Busbar 9 and Busbar 10

3.2.1 D-STATCOM Power Quality Mitigation Strategies

The power quality concerned is voltage sags and the methods employed will

include the simulation model for voltage sags and their respective control strategies. For

example, the D-STATCOM is allocated at bus bar A and it will inject a voltage to the

bus bar. Using graph control, the improvement or decrement of voltage sag can be

observed. The procedure then repeated to bus bar B and bus bar C.

35

3.2.2 Voltage Sags Simulation Model.

The introduction of voltage sags to the system was done by using the fault

component from the software’s library.

Figure 3.7: Fault Component Connected In Shunt To The System.

Figure 3.7 shows the fault impedances that connected to simulation model. The

fault impedance of the component can be change to give different percentage of voltage

sags. The timed Fault Logic component simply opens and closes the fault at user

specified time. The duration of voltage sags is defined as between 0.5 cycle to one

minute and the desire duration of voltage sags can be set by using the timed fault logic.

In this simulation, a fault time is set to 1 s and occurs from 0.5s until 1.5s. The fault

component is connected in shunt to the study distribution system as shown in figure 3.6.

3.2.3 Voltage Sag Calculation

The value of voltage sags can be calculated in two terms. They are in percentage and

per unit calculation. Figure 3.8 shows an example of voltage sag with 0.5 sec duration.

Figure 3.8: Example of Voltage sag

36

The percentage of voltage sag of figure 3.8 is given by,

%100(%)).(

).().( xV

VVSag

upsagpre

upsagupsagpre

(3.6)

From equation 3.6, the percentage of voltage sag is

%100(%)).(

).().( xV

VVSag

upsagpre

upsagupsagpre

%.50

%1000.1

5.00.1

x

The voltage sag is 50% and it is consider as severe voltage sag.

3.2.4 Voltage Sag Control Strategies

The control used in this simulation is AC voltage or reactive power control. This control

is divided into two parts

Figure 3.9: Voltage Control Loop

37

As shown in figure 3.9, the PI controller regulates the AC side voltage sourced

converter (VSC) or alternatively, reactive power into or out of the VSC. The output of

the PI controller is the angle order, which is used to maintain the phase shift. The

reactive power from the system is compared to the referenced per-unit voltage that

contributes to a change in phase shift. The difference in phase shift will provide the

needed reactive power from the dc capacitor.

The sinusoidal PWM (SPWM) technique is shown in figure 3.10. The SPWM

firing pulses to the GTOs are obtained by comparing the PWM carrier signals and the

reference sine waveform. The PLL plays an important role in synchronizing the valve

switching to the distribution system’s voltage and locked to the phases at fundamental

frequency to generate the PWM triangular carrier signals. Its frequency is multiplied to

the PWM switching frequency. As shown in figure 3.10a, the switching frequency is set

to 1.5 kHz which 30 times the system’s operating frequency and converted to a

triangular signal whose amplitude is fixed between -1 to +1.

Figure 3.10b), the 6-pulse PLL are applied to generate sinusoidal curves at the

wanted fundamental frequency. Shft is effectively the output coming from the voltage

control loop,i.e. the angle order. The difference in angle will change the width of the

PWM signal and ultimately the needed reactive power to be supplied to the system. In

this simulation, the amplitude is fixed and phase shift is controlled to maintain.

(a)

38

(b)

Figure 3.10: SPWM Technique (a) Generation of PWM Carrier Signals

(b) Generation of Reference Sine Waveform.

The firing pulses to the GTOs are generated by the Interpolated Firing Pulses

component as shown in figure 3.11. With GTOs, the gate pulses are applied to switch-

on as well as switch-off. In PSCAD, these actions are preferred to model with

interpolated firing so that the exact instance of switching between calculations steps can

be achieved [14]. The software interpolates the solution between two time steps to find

the solution at the exact instant of event [14].

The components compare the PWM carrier signal that is triangular signal with

the sine wave signal. Both the turn-on and turn-off pulses are generated for interpolated

switching [14].

Figure 3.11: Interpolated Firing Pulses Component for 6-Pulse Converter.

39

3.3 Bus Bar Selection

The results of simulation are used to identify the location of D-STATCOM. The

Modal Analysis method is used to select the potential buses.

3.3.1 Modal Analysis

The simulation is run in two conditions which are simulation of network without

installing the D-STACOM and simulation of network with D-STATCOM. The network

without D-STATCOM is simulated to monitor the voltage at each main bus bar and the

voltage sag that occurs. From the results of simulation for the network with D-

STATCOM, the potential bus bar as D-STATCOM location is identified. Modal

analysis is used to identify the best location of D-STATCOM. From the results of

simulation, the graphs show the time taken for voltage to recover.

The time of recovery is based on voltage recovery criteria as shown in figure

2.13. Therefore the bus bar is classified to ideal, adequate or poor. The ideal bus bar

then is chosen as the location of D-STATCOM. For example the bus one take 0.4 s to

clear the fault, therefore it is classified as an ideal bus bar because the time of recovery

is less than 0.6s and selected as one of the location of D-STATCOM in the network.

40

3.3.2 Installation of D-STATCOM

The locations of D-STATCOM are obtained after applying modal analysis

method and ideal bus bars are chosen to install the D-STATCOM. Therefore, D-

STATCOM is installed at the chosen bus bar only. Numbers of D-STATCOM also

known from the locations of D-STATCOM and it will reduce the number of D-

STATCOM for this distribution network. If the number of D-STATCOM is reducing, it

also will reduce the cost in Power Quality Monitoring System (PQMS).

41

CHAPTER IV

RESULT AND DISCUSSION

In this chapter, it explains the results obtained from the simulation and its analysis. It

present that the 11kV distribution system is put under the effect voltage sag and analysis

of D-STATCOM effect in mitigating voltage sag. Voltage recovery criteria are also

identified in this chapter.

4.1 Result of Simulation Network without D-STATCOM

The system was simulated for three seconds with three phase balance fault

occurring at time 0.5s for duration of 1.0s. Figure 4.1 shows the layout of the

distribution system without D-STATCOM.

Figure 4.1: The Distribution System without D-STATCOM.

The results of simulation are shown in figure 4.2. There are four graphs which

are represent the per-unit voltage for overall system and voltage drop at main bus bar A,

B and C.

(a)

64

(b)

(c)

(d)

Figure 4.2: (a): Per-unit Voltage (b) Voltage drop at Main bus bar A

(c) Voltage drop at Main bus bar B

(d) Voltage drop at Main bus bar C.

Figure 4.2 shows the voltage drop at main busbar A, B and C with no D-

STATCOM in distribution network. The voltage is drop starting from 0.5s until 1.5s

because of faults time is set to 0.5s for duration 1s. After the fault time, the voltage will

return normal. This short-term reduction in voltage is called voltage sag. In this

simulation, the voltage sag is non-repetitive but the in the real network situation, it can

65

be happen. Voltage sag contributes to power quality problems and effect machine or

process downtime. These types of problems are costly to the end-user.

4.2 Result of Simulation Network with D-STATCOM.

To illustrate the use of the D-STATCOM in compensating voltage sag, a voltage

sag condition is simulated by creating a balance three-phase fault and the fault is occur

at 0.5s until 1.5s.

4.2.1 D-STATCOM at Bus bar A.

Figure 4.3 shows the layout of the distribution system with the effects of D-

STATCOM. There are graphs of the per-unit voltage for overall system and voltage

drop at main bus bar A, B and C.

66

Figure 4.3: The Distribution System with D-STATCOM at bus bar A.

(a)

(b)

67

(c)

(d)

Figure 4.4 (a): Per-unit Voltage (b)Voltage drop at Main bus bar A

(c) Voltage drop at Main bus bar B

(d) Voltage drop at Main bus bar C.

Figure 4.4 shows the effect of voltage when D-STATCOM is installed at busbar

A. From the figure, the voltage of all the main busbar from time 0.5s to 1.5s was

improved and voltage sag also reduced.

4.2.2 D-STATCOM at Bus bar B.

Figure 4.5 shows the layout of the distribution system with the effects of D-STATCOM. There

are graphs of the per-unit voltage for overall system and voltage drop at main bus bar A, B and C.

68

Figure 4.5: The Distribution System with D-STATCOM at bus bar B.

Figure 4.6 shows the effect of voltage when D-STATCOM is located at busbar

B. From the graphs, the voltage of all the main busbar from time 0.5s to 1.5s was

improved and voltage sag also reduced.

69

(a)

(b)

( c)

(d)

Figure 4.6: (a): Per-unit Voltage (b) Voltage drop at Main bus bar A

(c) Voltage drop at Main bus bar B

70

(d) Voltage drop at Main bus bar C

4.2.3 D-STATCOM at Bus bar C.

Layout of the distribution system with the effects of D-STATCOM is shown in

figure 4.7. There are graphs of the per-unit voltage for overall system and voltage drop

at main bus bar A, B and C.

Figure 4.7: The Distribution System with D-STATCOM at bus bar C.

71

Figure 4.8 shows the responses of other main busbar when D-STATCOM is

installed at busbar C. From the figure, the voltage of all the main busbar from time 0.5s

to 1.5s was improved and voltage sag also reduced.

(a)

(b)

(c)

72

(d)

Figure 4.8: (a) Per-unit Voltage (b) Voltage drop at Main bus bar A

(c) Voltage drop at Main bus bar B

(d) Voltage drop at Main bus bar C

4.3 D-STATCOM Allocated at Main Bus bar for Voltage Sag Compensation.

4.3.1 D-STATCOM Allocated at Main Bus bar A.

(a)

73

(b)

(c)

Figure 4.9: Load Voltage a) without D-STATCOM b) with D-STATCOM.

c) Time of Recovery.

Time of recovery,

The simulation results of the D-STATCOM at bus bar A response in term of the load

voltage in per unit are shown in figure 4.9. For the system without the D-STATCOM,

the load voltage drop from 0.818p.u to 0.800p.u as shown in figure 4.9(a). This voltage

sag condition which is due to the three-phase fault created at time, t = 0.5s for duration

1.0s and the run time simulation is 3s.

For the system with the D-STATCOM connected the load, voltage increase from

0.800p.u to 0.993p.u as shown in figure 4.9(b). There are spikes at the beginning and at

st

sst

25.0

5.175.1

74

the end of fault are occurred due to capacitor’s charging and discharging. The load

voltage returns to near its rated voltage due to the voltage sag compensation capability

of D-STATCOM. Figure 4.9(c) shows that the load voltage takes 0.25s to recover to

rated voltage. The recovery time then is plotted in a graph of Voltage recovery criteria

(time) is shown in figure 4.10.

Figure 4.10: Plot of Voltage Time Recovery

By referring voltage recovery criteria in figure 2.13, the recovery is considered

ideal because it happen within 0.6s. Figure 4.11 shows the effect of D-STATCOM to

voltage at bus bar A, B and B with and without D-STATCOM at bus bar A.

Figure 4.11 shows the effect of the D-STATCOM to other bus bar when the D-

STATCOM is located at bus bar A. The results are showed here are for the phase A

voltage but however the response are similar for the phase B and C voltages. The effect

of the D-STATCOM shows that the voltage sag can be reduce and voltage drop during

fault time had recover in 0.25s.

75

(a)

(b)

(c)

76

(d)

(e)

(f)

77

Figure 4.11: Load voltages at bus bar A, B and C (a), (c), (e) without D-STATCOM

(b), (d), (f) with D-STATCOM.

4.3.2 D-STATCOM Allocated at Main Bus bar B.

(a)

(b)

78

(c)

Figure 4.12: Load Voltage a) without D-STATCOM b) With D-STATCOM.

c) Time of Recovery.

Time of recovery,

The simulation results of the D-STATCOM at bus bar B in term of the load

voltage in per unit are shown in figure 4.9. For the system without the D-STATCOM,

the load voltage drop from 0.818p.u to 0.800p.u as shown in figure 4.12(a). This voltage

sag condition is referred at time, t = 0.5s to 1.5s for duration 1.0s and the run time

simulation is 3s.

For the system with the D-STATCOM connected the load voltage increase from

0.800p.u to 0.997p.u as shown in figure 4.12(b). The load voltage returns to near its

rated voltage due to the voltage sag compensation capability of D-STATCOM. Figure

4.12(c) shows that the load voltage takes 0.29s to recover to rated voltage. The recovery

time then is plotted in a graph of Voltage recovery criteria (time) is shown in figure

4.13.

st

sst

29.0

5.179.1

79

Figure 4.13: Plot of Voltage Time Recovery.

The graph of recovery time is plotted based on voltage recovery criteria in figure

2.13. From the time of recovery it is considered ideal because it takes 0.29s which is

happen within 0.6s. Figure 4.14 shows the effect of D-STATCOM to voltage at bus bar

A, B and B with and without D-STATCOM at bus bar B.

Figure 4.14 shows the effect of the D-STATCOM to other bus bar when the D-

STATCOM is located at bus bar B. The results are showed here are for the phase A

voltage but however the response are similar for the phase B and C voltages. The effect

of the D-STATCOM shows that the voltage sag can be reduce and voltage drop during

fault time had recover in 0.29s.

80

(a)

(b)

(c)

81

(d)

(e)

(f)

Figure 4.14: Load voltages at bus bar A, B and C; (a), (c), (e) without D-STATCOM (b), (d), (f) with

D-STATCOM.

82

4.3.2 D-STATCOM Allocated at Main Bus bar C.

(a)

(b)

(c)

83

Figure 4.15: Load Voltage a) without D-STATCOM

b) With D-STATCOM. c) Time of Recovery.

Time of recovery,

The simulation results of the D-STATCOM at bus bar C in term of the load

voltage are shown in figure 4.15. For the system without the D-STATCOM, the load

voltage drop from 0.818p.u to 0.800p.u as shown in figure 4.15(a). This voltage sag

condition is referred at time, t = 0.5s to 1.5s for duration 1.0s and the run time simulation

is 3s. For the system with the D-STATCOM connected the load voltage increase from

0.800p.u to 1.0 p.u as shown in figure 4.15(b). The load voltage returns to its rated

which is 1.0 p.u voltage due to the voltage sag compensation capability of D-

STATCOM.

Figure 4.15(c) shows that the load voltage takes 0.23s to recover to rated

voltage. The recovery time then is plotted in a graph of Voltage recovery criteria (time)

is shown in figure 4.16.

st

sst

23.0

5.173.1

84

Figure 4.16: Plot of Voltage Time Recovery.

The graph of recovery time is plotted based on voltage recovery criteria in figure

2.13, the time of recovery is considered ideal because it takes 0.23s to recover which is

happen within 0.6s. Figure 4.16 shows the effect of D-STATCOM to voltage at bus bar

A, B and B with and without D-STATCOM at bus bar C.

(a)

85

(b)

(c)

(d)

86

(e)

(f)

Figure 4.17: Load voltages at bus bar A, B and C (a), (c), (e) without D-STATCOM

(b), (d), (f) with D-STATCOM.

Figure 4.17 shows the effect of the D-STATCOM to other bus bar when the D-

STATCOM is located at bus bar C. The results that showed here are for the phase A

voltage, however the response are similar for the phase B and C voltages. The effect of

the D-STATCOM shows that the voltage sag can be reduce and voltage drop during

fault time had recover in 0.23s.

87

CHAPTER V

CONCLUSION AND FUTURE WORK

5.1 Conclusion

In this thesis, the modeling and simulation of 10 bus bar distribution network has

been done using the PSCAD/EMTDC program. In these studies, all the objectives

address in chapter I have been fulfilled.

From the simulation results, the D-STATCOM responded well in mitigating

voltage sag caused by three-phase balance fault. Table 3 shows the voltage after

recovery during fault which is from 0.5s to 1.5s and the time taken to recover to rated

voltage. Rated voltage in per-unit is 1.0 p.u.

88

Table 5.1: Summary of Network Simulation.

Voltage ( V p.u)Location of

D-STATCOM

( Bus bar)

Without D-

STATCOM

With D-

STATCOM

Time of

recovery(s)

Classification

A 0.800 0.993 0.25 Ideal

B 0.800 0.997 0.29 Ideal

C 0.800 1.0 0.23 Ideal

From table 3.1, when D-STATCOM allocate at bus bar A, the per-unit voltage

improve from 8.00Vp.u to 0.993Vp during fault time and it takes 0.25s as time of

recovery. If D-STATCOM is located at Bus bar B, the per-unit voltage improve from

0.800 Vp.u to 0.997 Vp.u and takes 0.29s as recovery time. The best result is when the

D-STATCOM is located at bus bar C which is returning the Voltage per-unit during

fault time to 1.0p.u. It takes the less time which is 0.23s as time of recovery.

Based on the recovery times, all location is ideal to install D-STATCOM because

voltage is recovered within 0.6s. Although the three of main bus bar are an ideal

location, only the best location will be chosen. The power quality problem (voltage sag)

can be reduce or eliminate when D-STATCOM is located at bus bar C. Therefore, the

bus bar C is chosen as the location in this distribution network. The number of D-

STATCOM for this distribution network is one and this will reduce the cost in power

quality monitoring system (PQMS).

89

5.2 Future Work

The simulation works for this project has been carried out successfully. The

following are some ideas for future research related to the works carried out in the

thesis:

i) Investigation on the use of other power semiconductor devices like Insulated

Gate Bipolar Transistor (IGBT) against GTO for the design of custom power

devices so as to compare the switching behaviour of the devices.

ii) Network design and simulation using other software such as MATLAB.

iii) Economic evaluation on the use of the custom power devices will need to be

studied in terms of cost and saving.

iv) Subject the D-STATCOM under different power quality problem such as

voltage swells or voltage flicker.

90

REFERENCES

[1] Masoud Aliakbar Golkar,” Electric Power Quality : Types and Measurements”

2004 IEEE International Conference on Electric Utility Deregulation,

Restructuring and Power Technologies (DWT2004) April 2004.Power

System Conference and Exposition, Vol.1, Oct 2004,pp.201-207.

[2] P.P Barker, J.J. Burke, R.T.Mancao, T.A.Short, C.A. Warren, and

C.W.Burns, “Power Quality Monitoring of a Distribution System,”

IEEE/Trans. Power Del.,vol.9, no.2,pp.1136-1142,Apr.1994.

[3] E.Acha, V.G Agelidis, O.Anaya-Lara, T.J.E.Miller(2002),”Power Electronic

Control in Electrical Systems”. 1st edition, New Delhi, Newnes. 108-

118,137-137,290-336.

[4] H.G. Sarminto, G. Pampin, J.D. de Leon, “FACTS Solution for Voltage Stability

problems in Large Metropolitan Area,” 2004 IEEE/PES Power System

Conference and Exposition, vol 1, Oct. 2004, pp.275-282.

[5] Shigenori Naka, Takamu Genji, Toshiki Yura and Yoshikazu Fukuyama, “ A

Hybrid Particle Swarm Optimization for Distribution State Estimation”,

2003 IEEE/PS, vol.18,No.1. February 2003

[6] H. Yonezawa, T.Shimato, M.Tsukada, K. Matsuno, I.Iyoda, J.Paserba, G.F.Reed,

“Study of a STATCOM application for voltage stability evaluated by

dynamic PV curve and time simulation,”2000 IEEE Power Engineering

Society Winter Meeting, vol.2, Jan 2000, pp.1471-1476.

91

[7] L.J.Cai,I.Erlich,G.Stamtsis, “Optimal Choice And Allocation of FACTS Device

In Deregulated Electricity Market Using Genetic Algorithms,” 2004

IEEE/PES

[8] M.K. Verma, S.C Srivastava, “Optimal placement of SVC for Static and

Dynamic voltage security enhancement, “ International Journal Emerging

Electric Power Systems, vol.2,no. 2, 2005, Article 1050.

[9] Hadi Saadat(2004) “Power System Analysis”.2nd edition. Singapore McGraw-

Hill. 4-8.

[10] M.F.Kandlawala and A.H.M.A.Rahim, “Power system dynamic performance

withSTATCOM controller, “ 8th annual IEEE technical exchange

meeting, April 2001.

[11] R.Mohan Mathur, Rajiv K.Varma(2002),”Thyristor-Based FACTS Controllers

for Electrical Transmission System”, United States of America, Willey

Inter- Scince,415-417.

[12] J.Arrilaga, N.R Watson, S.Chen(2000), “Power System Quality Assessment”,

Chichester, Wiley. 1-13.

[13] D. Won, I.Chung, S.Moon, J.Kim, J.Seo and J.Choe, “ Development of Power

Quality Monitoring Syatem with Central Processing Scheme,” in

Proc.IEEE Power Eng. Soc. Summer Meeting, vol.2.2002.pp 915-

919.

[14] Noor Izzri bin Hj Abdul Wahab( May 2002), “Power Quality Improvement

Using Distribution Static Compensator (D-STATCOM) On 11 kV

Distribution System”, Universiti Putra Malaysia: Mse Thesis. 23-31, 38-

72.

92

[15] M A Hannan(2003), “ Modelling And Simulation of Custom Power Devices for

Power Quality Improvement”, Universiti Kebangsaan Malaysia: MSc

Thesis.

[16] Distribution Network Configuration Retrieved from

http://en.wikipedia.org/wiki/Power_distribution. 28 January 2008.

[17] A busbar in electrical power distribution. Retrieve from

http://en.wikipedia.org/wiki/Busbar. 28 January 2008.

[18] Optimal Allocation of Shunt Dynamic Var Source SVC and STATCOM: A

Survey. Retrieve from

www.ece.utk.edu/~tolbert/publications/apscom_2006. 21 February 2008.

[19] Sidhartha Panda and Narayana Prasad Padhy (August 2007), Optimal Location

and ontroller Design of STATCOM for Power System Stability

Improvement Using PSO, Indian Institute of Technology, India.

93

APPENDIX A

94

APPENDIX A

GANTT CHART FOR PSM 1

GANTT CHART FOR PSM 2

71

APPENDIX A1

PSM 1 GANTT CHART (2008/2009)

Project Schedule (PSM 1)

WEEK AND DATE

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

PERIOD

TASK 27/12 3/01 10/01 17/01 24/01 31/01 7/02 14/02 21/02 28/02 6/03 13/03 20/03 27/03 3/041. Search the PSM project

2. Determine the project title.

3. Discuss and understanding the project overview with supervisor.

4. Search the information.

5. Discuss the objectives and scope project.

6. Identify methodology of project. WEEK AND DATE

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 PERIOD

TASK 27/12 3/01 10/01 17/01 24/01 31/01 7/02 14/02 21/02 28/02 6/03 13/03 20/03 27/03 3/04

72

7. Do research at the chosen method.

8. Implementation the PSCAD software

9. Design the 8 busbar

distribution network using PSCAD

10. Writing PSM 1 report

11. Writing seminar paper PSM 1

. 10. Preparation for seminar

11. Seminar

73

APPENDIX A2

PSM 2 GANTT CHART (2008/2009

Week ACTIVITY1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

1. Convert one line diagram network to electrical network.

2. Design the distribution network circuit using PSCAD

3. Design the distribution network circuit with DVR using PSCAD

4. Simulate the result

5. Determine the locations and numbers of DVR

6. Measure and analyze the project

7. Conclude all the data

8. Writing the PSM 2 report

9. Writing seminar paper PSM 2

10. Preparation seminar

11. Seminar

74

APPENDIX B

DISTRIBUTION NETWORK SYSTEM OF PARIT RAJA,

BATU PAHAT, JOHOR.

CIRCUITS USED FOR SIMULATION – LAYOUT IN PSCAD/EMTDC

75

(a) Distribution Network System Of Parit Raja, Batu Pahat, Johor.

APPENDIX B1

76

APPENDIX B2

(a) Layout of Distribution System without D-STATCOM

77

(b) Layout of Distribution System with D-STATCOM