ABSTRACT
The study used passive compensators and FACTS controllers to achieve power system
compensation by obtaining load flow of the Northern Nigerian 330kV transmission grid;
determining the voltage magnitudes at the various buses; identifying the voltage violations and
applying the passive compensators and FACTS controllers at the worst case scenarios of the
voltage violations. The work compared the effects of the compensators on the Northern Nigerian
330kV transmission grid. The load flow study was carried out to obtain the voltage magnitudes
with the assumption that voltage magnitudes should range between 0.90pu and 1.10pu in the
simulations. And a bus whose voltage magnitude falls out of the range suffers from voltage
violation and is considered a critical case for power system compensation. The load flow study
for the network under consideration (Northern Nigerian 330kv line) was done with the Newton-
Raphson method owing to its quick convergence. In addition, it converged in 0.34 seconds after
five P and Q iterations. The results of the simulation shows that Birnin-Kebbi (0.6245pu),
Katampe (0.7237pu), Kaduna (0.6950pu), Kano (0.5713pu), Yola (0.8457pu), Gwagwalada(
0.7013pu), Lokoja ( 0.8516pu), Ajaokuta ( 0.8045pu), and Geregu ( 0.8854pu) have low
voltages. The simulation of the network with passive compensator and FACTS controller
improved the voltages at: Gwagwalada, Kano and Birim Kebbi buses by 0.49%, 1.04% and 4.5%
respectively.
TABLE OF CONTENTS
itle Page- – – – – – – – – – – i
Approval Page- – – – – – – – – – ii
Certification Page – – – – – – – – – iii
Dedication – – – – – – – – – – iv
Acknowledgment – – – – – – – – – v
Abstract – – – – – – – – – – vi
Table of Contents – – – – – – – – – vii
List of Tables – – – – – – – – – – viii
List of Figures – – – – – – – – – ix
List of abbreviations – – – – – – – – – x
CHAPTER ONE
1.1 Introduction- – – – – – – – – – 1
1.2 Background of the Study- – – – – – – – – 2
1.3 Statement of research problem- – – – – – – – 3
1.4 Objective of the thesis- – – – – – – – – 3
1.5 Scope of the study- – – – – – – – – 4
1.6 Significance of the study – – – – – – – – 4
CHAPTER TWO
2.1 Literature Review- – – – – – – – – 5
2.2 Transmission System Compensation- – – – – – – 5
2.3 Series Compensation – – – – – – – – 7
2.4 Shunt Compensation – – – – – – – – 7
2.5 Shunt Capacitive Compensation – – – – – – – 7
2.6 Inductive Compensation – – – – – – – – 8
2.7 Requirements for bulk A.C transmission of electric power- – – – 8
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2.7.1 Synchronism- – – – – – – – – – 8
2.7.2 Voltage profile- – – – – – – – – – 9
2.8 Power System Control – – – – – – – – 10
2.9 Load Flow Studies- – – – – – – – – 13
2.10 Classification of Bus- – – – – – – – – 14
2.10.1 Swing Bus- – – – – – – – – – 15
2.10.2 Generator Bus/Voltage Controlled Bus (P, V bus)- – – – – 15
2.10.3 Load Bus (P, Q Bus) – – – – – – – – 16
2.11 Load Flow methods in power systems- – – – – – – 16
2.11.1 Gaus-Seidel Method – – – – – – – – 16
2.11.2 Newton-Raphson- – – – – – – – – 17
2.11.3 Fast Decoupled Load Flow – – – – – – – 17
2.12 Comparison of the Load Flow Methods- – – – – – 18
CHAPTER THREE
3.1 Methodology- – – – – – – – – – 20
3.2 Mathematical model of Newton Raphson. – – – – – 22
3.3 Control of Voltage and Reactive Power- – – – – – – 24
3.4 Methods of Voltage Control- – – – – – – – 25
3.5 Series Capacitors- – – – – – – – – 26
3.6 Modeling of Reactive Compensating Devices- – – – – – 26
3.7 Compensation Effect on Maximum Power- – – – – – 26
3.8 Improvement of Reactive Power by Static Capacitor- – – – – 27
3.9 Capacitor Rating Calculations- – – – – – – – 28
ix
3.10 Relationship Between Reactive Power, Voltage and Capacitor (Q,V& C) in
AC Power System — – – – – – – – 31
3.11 Rating of Capacitor Bank- – – – – – – 31
3.12 Series Capacitor Compensation– – – – – – 32
3.13 Block Diagram Model of UPFC- – – – – – 33
CHAPTER FOUR
4.1 Simulation and Results – – – – – – – – 38
4.2 Discussion of Results – – – – – – – 50
CHAPTER FIVE
5.1 Conclusion- – – – – – – – – 52
5.2 Suggestion for Further Study – – – – – – 52
References- – – – – – – – – – 53
Appendix 1: Power Flow Result – – – – – – 58
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CHAPTER ONE
1.1 INTRODUCTION
The challenges of the power system operation and utilization have brought about its
compensation using passive compensators and FACTS controllers. The work will compare the
results of the application of passive compensators and FACTS controllers in enhancing stability
of a power system. Voltage stability analysis and control become increasingly important as the
systems are being operated closer to their stability limits including voltage stability limits. This is
due to the fact that there is lack of network investments and there are large amounts of power
transactions across regions for economical reasons in electricity market environments. Power
system operates in a synchronous mode and is subjected to a wide range of disturbances which
could be small, medium or large. The disturbance may be due to load changes, network changes,
faults, outages of the equipment, etc. These disturbances affects the overall stability of the power
systems. However, Power system stability is the ability of an electric power system, for a given
initial operating condition, to regain a state of operating equilibrium after being subjected to a
physical disturbance, with most system variables bounded so that practically the entire system
remains intact[1]. Regrettably, the Nigerian electric power system has faced daunting challenges
irrespective of the huge amount of money that has been pumped into the sector in the recent
time. Successful operation of a power system depends largely on the engineer’s ability to provide
reliable and uninterrupted service to the loads. The reliability of the power supply implies much
more than merely being available. Ideally, the loads must be fed at constant voltage and
frequency at all times. The first requirement of reliable service is to keep the synchronous
generators running in parallel and with adequate capacity to meet the load demand. Synchronous
machines do not easily fall out of step under normal conditions. A second requirement of reliable
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electrical service is to maintain the integrity of the power network. The high-voltage
transmission system connects the generating stations and the load centers. Power-system stability
is a term applied to alternating-current electric power systems, denoting a condition in which the
various synchronous machines of the system remain in synchronism, or “in step,” with each
other. Conversely, instability denotes a condition involving loss of synchronism, or falling “out
of step[1].
1.7 Background of the Study
Power system operation is aimed at matching supply with demand and provides
compensation for transmission loss, voltage and frequency regulation, reliability provision etc.
The need for more efficient and fast responding electrical systems has given rise to innovative
technologies in transmission using solid-state devices. These are called FACTS devices which
enhance stability and increase line loadings closer to thermal limits. Flexible AC transmission
systems (FACTS) have gained a great interest during the last few years, due to recent advances
in power electronics. FACTS devices have been mainly used for solving various power system
steady state control problems such as voltage regulation, power flow control, and transfer
capability enhancement. The development of power semiconductor devices with turn-off
capability (GTO, MCT) opens up new perspectives in the development of FACTS devices.
FACTS devices are the key to control electrical energy economically and environmental friendly
in future. The latter approach has two inherent advantages over the more conventional
switched capacitor- and reactor- based compensators. Firstly, the power electronics-based
voltage sources can internally generate and absorb reactive power without the use of ac
capacitors or reactors. Secondly, they can facilitate both reactive and real power compensation
and thereby providing independent control for real and reactive power flow. Their objectives in a
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power system are to increase power transmission capability, voltage control, voltage stability
enhancement and power system stability improvement [1].
1.8 Statement of research problem
Owing to the mechanical control mechanism supplemented by lack of proper load
dispatch tools, the present day power system is flexible and stiff. This makes the system manager
helpless as a result leading to various grid problems such as overloading of transmission
elements, power VAR management, etc.
Lack of control measures to deal with emergency operating conditions often leads to grid
disturbances and voltage violations. However, with the availability of FACTS controllers for
power system applications, it has become possible to replace the mechanical closing/opening of
circuit breaker. It is now possible to change the basic characteristics of the network by electronic
devices to achieve the requisite flexibility. Moreover, with the availability of various
compensating devices, there is the challenges of which one to be used by the system operators on
the power system.
1.9 Objective of the thesis
The study is aimed at using passive compensators and FACTS controllers to achieve
power system compensation.
The specific objectives of the study are:
· To obtain the load flow of the Northern Nigerian 330kV transmission grid
· To determine the voltage magnitudes at the various buses
· To identify the voltage violations
· To apply the passive compensators and FACTS controllers at the worst case scenarios of
voltage violations and comparing the effects of the compensators.
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1.10 Scope of the study
The study is restricted to the application of the passive compensators and FACTS controllers
at the Northern Nigerian 330kV transmission grid.
1.11 Significance of the study
The implementation of this work would offer the following benefits:
Ø Improve the voltage magnitudes.
Ø The people working in the control room find it very easy to control the line transmission
during disturbances.
Ø It helps to prevent unwanted damages to the line by the process of controller.
Ø It limits excessive voltage drop.
Ø The individual consumers will benefit from it by using a normal voltage.
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