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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
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