STATIC AND DYNAMIC IMPACT OF HVDC, TNB-EGAT INTERCONNECTION

SYSTEM

SHAHIDA BINTI MOHD SAID @ SAYED

This thesis is submitted as partial fulfillment of the requirements for the award of the

Bachelor of Electrical Engineering (Power Systems)

Faculty of Electrical & Electronics Engineering

University Malaysia Pahang

NOVEMBER, 2010

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“All the trademark and copyrights use herein are property of their respective owner.

References of information from other sources are quoted accordingly; otherwise the

information presented in this report is solely work of the author.”

Signature : ____________________________

Author : SHAHIDA BINTI MOHD SAID @ SAYED

Date : 30 NOVEMBER 2010

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ACKNOWLEDGEMENT

In the name of ALLAH s.w.t., most gracious, most merciful.

The thesis has been an extremely satisfying experience for me. I would like to

acknowledge all those who have been a part of this project. Firstly, I would like to

express my appreciation to my project supervisor, Mr. Mohd Redzuan Bin Ahmad for

his guidance and advices in pursuing my research idea. Without his continued support

and interest, this thesis cannot be achieved as presented here.

I am also appreciated to my beloved family and friends for their constant on

supporting me to pursue my thesis successfully. Their encouragement and help are very

useful for me on keep doing this project until it successful.

Finally, I would like to thank University Malaysia Pahang (UMP) by giving me

this opportunity to continue my studies here. This opportunity I grab it as my

experiences before go further to the working field.

May God repay all of your kindness.

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ABSTRACT

HVDC interconnection TNB-EGAT system is the second stage of the grid

interconnection between Malaysia and Thailand. This system is to export the electrical

power during lower demand and import during TNB’s peak load. The objectives of this

project are to study the static and dynamic impacts of HVDC TNB-EGAT system. This

study will also focus on modeling and simulating of the HVDC interconnection system

by using Power System Computer Aided Design (PSCAD/EMTDC) software. The load

flow analysis has been conducted by comparing the simulation from PSCAD with the

actual data. Hence, the fault analysis also has been conducted by locating the fault at the

HVDC modeling which is the DC line fault analysis and AC signal phase short circuit at

inverter station analysis. This system is stabilized by having a transient stability

analysis. The PSCAD software has the features that can be used to conduct such

analysis. This analysis has been performed and the impacts have been monitored on the

system and both power system utilities. From the analysis, some improvements have

been suggested for the future system.

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ABSTRAK

HVDC sistem interkoneksi TNB-EGAT merupakan tahap kedua dari

interkoneksi grid antara Malaysia dan Thailand. Sistem ini adalah untuk eksport kuasa

selama permintaan yang lebih rendah dan import selama beban puncak TNB. Tujuan

dari projek ini adalah untuk mempelajari kesan statik dan dinamik sistem HVDC TNB-

EGAT. Penyelidikan ini juga akan mengfokuskan pada pemodelan dan simulasi sistem

interkoneksi HVDC dengan menggunakan Power System Computer Aided Design

(PSCAD/EMTDC) perisian. Analisis aliran kuasa telah dilakukan dengan

membandingkan simulasi dari PSCAD dengan data aktual. Oleh sebab itu, analisis

kesalahan juga telah dilakukan dengan meletakkan kesalahan pada pemodelan HVDC

yang merupakan garis analisis kesalahan DC dan isyarat AC rangkaian fasa pendek pada

analisis stesen inverter. Sistem ini akan stabil dengan memiliki analisis kestabilan

transien. Perisisan PSCAD mempunyai ciri-ciri yang boleh digunakan untuk melakukan

analisis tersebut. Analisis ini telah dilakukan dan kesannya telah dipantau pada sistem

dan utiliti sistem kuasa untuk keduanya. Dari analisis tersebut, beberapa pembaikan

telah dicadangkan untuk sistem pada masa hadapan.

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TABLE OF CONTENTS

CHAPTER CONTENTS PAGE

TITLE i

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xiii

LIST OF ABREVIATIONS xiv

LIST OF APPENDICES xv

1 INTRODUCTION

1.1. Overview of The Project 1

1.2. Objective 3

1.3. Scope of Project 3

1.4. Problem Statement 3

1.5. Literature Review 4

1.6. Thesis Outline 5

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2 HIGH VOLTAGE DIRECT CURRENT (HVDC) TNB-EGAT

INTERCONNECTION SYSTEM

2.1. Introduction 8

2.2. Operation of HVDC 10

2.3. HVDC System Configuration 12

2.4. HVDC Converter Station 15

2.5. Differences of HVDC and HVAC 15

2.6. Advantages of HVDC 16

2.7. Application of HVDC 17

2.8. TNB Side 18

2.9. EGAT Side 19

2.10. HVDC Controls 20

2.11. Summary 22

3 STATIC AND DYNAMIC IMPACT OF HVDC

INTERCONNECTION SYSTEM

3.1. Introduction 23

3.2. Static and Dynamic Impacts 24

3.3. Tools 25

3.4. Analysis Procedures 27

3.5. Modelling of HVDC System 30

3.6. Calculation of the Parameters 36

3.7. Summary 45

4 RESULTS AND DISCUSSIONS

4.1. Introduction 46

4.2. Simulation in PSCAD/EMTDC 47

4.2.1. Load Flow Analysis 50

4.2.2. Fault Analysis 55

4.3. Summary 64

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5 CONCLUSIONS AND RECOMMENDATIONS

5.1. Conclusions 65

5.2. Recommendations 67

REFERENCES 68

APPENDIXES 71

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LIST OF TABLES

TABLE NO. TITLE PAGE

3.1 AC Equivalent Circuits Parameters of TNB-EGAT 31

HVDC Network

3.2 Parameters of Triple Tuned Filter at Rectifier AC Network 32

3.3 Parameters of Triple Tuned Filter at Inverter AC Network 33

3.4 PI Controller Parameter of Rectifier Current Controller 35

3.5 VDCOL Controller Parameter of Rectifier Current Controller 36

3.6 PI Controller Parameter for Inverter Current Controller and CEA

Controller 36

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LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 TNB-EGAT AC-HVDC Network Schematic Overview 10

2.2 Simplified AC-HVDC Systems Diagram 11

2.3 Monopolar Link 12

2.4 Bipolar Link 13

2.5 Back To Back Link 14

2.6 Parallel Multiterminal System 14

2.7 Series Multiterminal Link 14

2.8 TNB Side AC-HVDC Network 19

2.9 EGAT Side AC-HVDC Network 19

2.10 Simple DC Current Controller 20

2.11 Simple Extinction Angle Controller 21

3.1 Overview of PSCAD/EMTDC Model for TNB-EGAT

Network 27

3.2 Flowchart of the Project 29

3.3 TNB-EGAT AC System Equivalents Circuit 30

3.4 Triple Tuned Filter at Rectifier AC Network 31

3.5 Triple Tuned Filter at Inverter AC Network 32

3.6 Capacitor Bank at Rectifier Side 33

3.7 Capacitor Bank at Inverter Side 34

3.8 Passive DC Filter Installation at DC Transmission Line 34

3.9 AC Current Flow Diagram 43

4.1 Overall Overview of HVDC Interconnection System 47

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4.2 Rectifier Circuit 48

4.3 Rectifier Current Control 48

4.4 Inverter Circuit 49

4.5 Inverter Current Control 49

4.6 Graph at Rectifier Side 50

4.7 Results at Rectifier Side as in Meter 51

4.8 Graph at Inverter Side 52

4.9 Results at Inverter Side as in Meter 52

4.10 The Effect of Iorder 53

4.11 Power Meter at Rectifier Side and Inverter Side 54

4.12 Fault Simulation Model 55

4.13 Overall Overview of DC Line Short Circuit Fault 56

4.14 Graph of AC Volts (RMS) with DC Fault at Rectifier Side 57

4.15 Graph of DC Volts and DC Current at Rectifier Side 57

4.16 Power Meter at Rectifier Side 58

4.17 Graph of AC Volts (RMS) with DC Fault at Inverter Side 58

4.18 Graph of DC Volts and DC Current at Inverter Side 59

4.19 Power Meter at Inverter Side 59

4.20 DC Line Short Circuit of IEEE Paper 60

4.21 Overall Overview of AC Signal Phase Short Circuit at

Inverter Station 60

4.22 Graph of AC Volts (RMS) with AC Signal Phase Short

Circuit at Rectifier Side 61

4.23 Graph of DC Volts and DC Current at Rectifier Side 61

4.24 Power Meter at Rectifier Side 62

4.25 Graph of AC Volts (RMS) with AC Signal Phase Short

Circuit at Rectifier Side 62

4.26 Graph of DC Volts and DC Current at Inverter Side 63

4.27 Power Meter at Inverter Side 63

4.28 AC Signal Phase Short Circuit at Inverter Station of IEEE

Paper 64

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LIST OF SYMBOLS

p.u - Per Unit

V - Voltage

P - Active Power

Q - Reactive Power

S - Apparent Power

W - Wattage

Var - Varians

IOrder - DC Current Order

α - Valve Ignition Delay Angle

- Commutation Margin Angle

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LIST OF ABBREVIATIONS

PSCAD - Power System Computer Aided Design

EMTDC - Electromagnetic Transient

HVDC - High Voltage Direct Current

HVAC - High Voltage Alternating Current

DC - Direct Current

AC - Alternating Current

TNB - Tenaga Nasional Berhad

EGAT - Electricity Generating Authority of Thailand

PI - Proportional Integral

RMS - Root Mean Square

VDCOL - Voltage Dependent Current Order Limiter

CEA - Constant Extinction Angle

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A Flow Chart 71

B Data 73

C Gantt Chart 82

CHAPTER 1

INTRODUCTION

1.1. Overview of The Project

As early as 1881 Mercel Deprez, inspired by experiments with arc lights across

a DC generator, published the first theoretical examination of HVDC power

transmission. He soon put theory into practice and by 1882 he transmitted 1.4 kW at 2

kV over a distance of 35 miles. Electric power transmission was originally developed

with direct current. The availability of transformers and the development and

improvement of induction motors at the beginning of the 20th Century, led to greater

appeal and use of A.C. transmission. Through research and development in Sweden at

Allmana Svenska Electriska Aktiebolaget (ASEA), an improved multi-electrode grid

controlled mercury arc valve for high powers and voltages was developed from 1929.

Experimental plants were set up in the 1930’s in Sweden and the USA to investigate the

use of mercury arc valves in conversion processes for transmission and frequency

changing. D.C. transmission now became practical when long distances were to be

covered or where cables were required. The increase in need for electricity after the

Second World War stimulated research, particularly in Sweden and in Russia. In 1950, a

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116 km experimental transmission line was commissioned from Moscow to Kasira at

200 kV. The first commercial HVDC line built in 1954 was a 98 km submarine cable

with ground return between the island of Gotland and the Swedish mainland. In power

transmission system, High Voltage Direct Current (HVDC) is used widely in most of

modern countries. HVDC is used in transmission system for long distances. When

HVDC is combined in AC power system, there are many impacts occurs inside the

system such as static and dynamic impacts.

This project is to study the static and dynamic impact of HVDC, TNB-EGAT

interconnection system in order to upgrade their system in power transmission system if

the fault occurred. The analysis of this project is fully using the Power System

Computer Aided Design (PSCAD) program. The static impacts of this project are load

flow analysis and fault analysis. Moreover, the dynamic impact of this project is

transient stability analysis.

The HVDC network is based on the actual of TNB-EGAT project. The

simulation model consists of a static AC equivalent circuit, converter transformer,

converter valve group, DC transmission line, converter controllers, DC filter and AC

filters. The parameters of equivalent AC networks, HVDC converters, DC link, filters

and etc. are modelled through the PSCAD/EMTDC program.

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1.2. Objective

The objective of this project is to study the static and dynamic impact of HVDC,

TNB-EGAT interconnection system. Hence, to conduct the load flow analysis, fault

analysis and transient stability analysis of the system. Beside that, the objective is to

model and simulate the HVDC interconnection system by using Power System

Computer Aided Design (PSCAD)/EMTDC program.

1.3. Scope of The Project

The scopes of this project focus on modeling and simulating HVDC

interconnection for TNB-EGAT system. This project has been modeled by referring the

actual system of TNB-EGAT. Moreover, this project is focused on conducting the load

flow analysis and fault analysis.

1.4. Problem Statement

From this project, there is having three problem statements. The first one is

study of the static impacts that are important in order to planning, economic scheduling

and control of an existing system as well as planning its future expansion. Its also

provide with safety purpose too. The second one is study of dynamic impacts are

important in order to maintain in stability after large, major and sudden disturbance.

The third one understands the HVDC system.

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1.5. Literature Review

Power systems around the world are experiencing continuous unprecedented

change and stress due to increasing consumer load coupled with environmental and

resource constraints. These problems have been alleviated to some extent by using

HVDC transmission links [1]. High Voltage Direct Current (HVDC) transmission is

widely recognized as being advantageous for long-distance, bulk power delivery,

asynchronous interconnections and long submarine cable crossings. HVDC lines and

cables are less expensive and have lower losses than those for three-phase AC

transmission [2].

The 300 MW Thailand-Malaysia HVDC interconnection systems consist

of Khlong Ngae converter station on the Thai border and Gurun converter station on the

Malaysia border. Both stations are linked by a 300 kV DC overhead transmission line of

110 km. EGAT’s Khlong Ngae converter station is situated at Sadao district in

Southern Songkhla province, about 24 km from Thai-Malaysia border. TNB’s Gurun

converter station is located in Kedah, about 86 km from Malaysia’s northern border [14].

A contract was signed between TNB and EGAT on 15 August 1997 for the development

of the Malaysia-Thailand 300/600 MW HVDC Interconnection Project, to serve the

following purposes which are sharing of spinning reserve between TNB and EGAT AC

system, to take advantage of a more economical power exchange between both countries

due to the different daily peak consumption periods, emergency assistance to either AC

network and reactive power support (voltage control) to both AC networks [5].

In this project, there are having three analyses which are load flow analysis,

fault analysis and transient stability analysis. These analyses are modeled in PSCAD

program. PSCAD/EMTDC is a general-purpose time domain simulation program for

simulating power systems electromagnetic transients and its controls. The modelling is

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referring to the CIGRE Benchmark with the actual parameter of data from TNB. The

CIGRE HVDC Benchmark test model is used as the test system [1].

HVDC transmission applications can be broken down into different basic

categories. Although the rationale for selection of HVDC is often economic, there may

be other reasons for its selection. HVDC may be the only feasible way to interconnect

two asynchronous networks, reduce fault currents, utilize long cable circuits, bypass

network congestion, share utility rights-of-way without degradation of reliability and to

mitigate environmental concerns. In all of these applications, HVDC nicely

complements the AC transmission system [6].

1.6. Thesis Outline

This thesis includes five chapters. The brief outline of each chapter is presented

as below:

i. Chapter 1

This Chapter 1 is an introduction which is the overview of the project,

objective of the project, scope of the project description, problem

statement regarding to this research and the literature reviews that

previous works done by researchers.

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ii. Chapter 2

This Chapter 2 is the detail explanation about the project which is about

high voltage direct current (HVDC) that are includes the introduction,

operation of HVDC, HVDC system configuration, HVDC converter

station, differences of HVDC and HVAC, advantages of HVDC,

application of HVDC, TNB side, EGAT side and the HVDC controls.

iii. Chapter 3

This Chapter 3 is about the details of static and dynamic impact of

HVDC interconnection system which includes with introduction and the

static and dynamics impact of the system. In this chapter is the analysis

of the project that will discuss about what tools that are being used and

what is the parameter are needed in circuit diagram of TNB-EGAT AC-

HVDC network and the methodology by doing this project.

iv. Chapter 4

This Chapter 4 will discuss about the result that will achieve at the end

of this project by doing the simulation of PSCAD. These results will be

achieved by doing these analyses which are load flow analysis and fault

analysis that is having a different type of fault.

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v. Chapter 5

The last chapter is Chapter 5 which contains of the conclusion of overall

project by state the final result that gained from the project. The future

recommendations also stated in order to improve this project in the

future undertakings.

CHAPTER 2

HIGH VOLTAGE DIRECT CURRENT (HVDC) TNB-EGAT INTERCONNECTION

SYSTEM

2.1. Introduction

High voltage is used for transmission to reduce the energy lost in the resistance

of the wires. Power in a circuit is proportional to the current but the power loss as heat

in the wires is proportional to the square of the current. However, power is also

proportional to voltage, so for a given power level, higher voltage can be traded off for

lower current. Thus, the higher voltage can be produced the lower of the power loss.

Power loss can also be reduced by reducing resistance. Commonly achieved by

increasing the diameter of the conductor, but larger conductors are heavier and more

expensive.

High Voltage Direct Current (HVDC) technology has characteristics which

makes it especially attractive for certain transmission applications. HVDC transmission

is widely recognized as being advantageous for long-distance, bulk power delivery,

asynchronous interconnections and long submarine cable crossings. The number of

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HVDC projects committed or under consideration globally have increased in recent

years reflecting a renewed interest in this mature technology. New converter designs

have broadened the potential range of HVDC transmission to include applications for

underground, offshore, economic replacement of reliability-must-run generation, and

voltage stabilization. Developments include higher transmission voltages up to ±800

kV, capacitor-commutated converters (CCC) for weak system applications and voltage-

sourced converters (VSC) with dynamic reactive power control. This broader

technology range has increased the potential HVDC applications and contributed to the

recent growth of HVDC transmission. HVDC transmission applications can be broken

down into different basic categories. Although the rationale for selection of HVDC is

often economic, there may be other reasons for its selection. HVDC may be the only

feasible way to interconnect two asynchronous networks, reduce faults, currents, utilize

long cable circuits, bypass network congestion, share utility rights-of-way without

degradation of reliability and to mitigate environmental concerns. In all of these

applications, HVDC nicely complements the AC transmission system.

The interconnection between TNB and EGAT consists of the construction of a

110 km HVDC line (86 km TNB, 24 km EGAT) with DC converter stations (12-pulse)

at both ends. The interconnection will be between Gurun 500/275 kV (50Hz) substation

on the Malaysia side and Khlong Ngae 230 kV (50Hz) substation on the Thailand side.

The converter station at Gurun will be constructed for bi-directional 300 MW monopolar

operations. In the past, the AC transmission line system linked between Thailand and

Malaysia to exchange the energy power with the capacity of 80 MW transferred from

Sadao Substation in Thailand. At the present, the HVDC grid network is implemented

for connection of the asynchronous 230 kV AC system of Thailand with 275 kV AC

system of Malaysia. The capacity of HVDC interconnection between Thailand and

Malaysia is 300 MW with the maximum overload capacity of 450 MW for 10 minutes.

The 110 km DC overhead transmission line is connected at voltage level of 300 kV

(approximately 24 km from the Thailand border and 86 km from Malaysia border).

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Initially, the converter station is configured as a monopole converter of 300

MW. Provision has also been made for adding a second 300 MW pole in the future in

order to extend the system into a bipolar configuration with a total capacity of 600 MW.

The first objective of this connection is to provide various benefits of both countries

comprising such as economic exchange of power between two different networks,

enhancing system reliability, sharing spinning reserve, sharing experiences on HVDC

operation and maintenance system to extend closer cooperation between Thailand and

Malaysia. Figure 2.1 below is illustrated as TNB-EGAT AC-HVDC network schematic

overview.

 

 

Figure 2.1: TNB-EGAT AC-HVDC Network Schematic Overview

2.2. Operation of HVDC

The power system is begin from power plant which is the electrical power is

producing by generator. The generator can be operated by using steam from many

sources like winding, nuclear, gas and coal. From power plant, electrical power will be