ABSTRACT
These synchronous machines have found any importance in the industries but not without problems related to the effect of saturation in the synchronous machines there is a need for the establishment of MATLAB model that can simulate the embedded Simulink Model with an approved level of solving the saturation effect on a synchronous machine. This work presented a dynamic analysis of synchronous machines with saturation effect. Relevant literatures were reviewed to ascertain the extent of the work done by other researchers in the field. The mathematically model of a synchronous machine with saturation effect, the algebraic equations were studied and the D-Q transformations presented. Based on the mathematical models, computer simulations with MATLAB/SIMULINK models of the test machines were carried out and he models used to compare the dynamic behaviors of the conventional and saturation effect of the synchronous machine at different operating conditions and parameters variations. The dynamic analysis of synchronous machine with a saturation effect contents were adopted in the design and the system simulated with MATLAB/SIMULINK using su- system blocks models for the conventional and saturation effect respectively. The dynamic performances of both models were modeled by simulating the Simulink to get results and the plots were achieved in MatLab. From the outcome of the results, it was observed that the saturation effect of the work has a lower field current overshot of 13pu as compared to 15pu conventional, the speed of the conventional over shot more than the saturation effect model. There was a uniform overshot of the electrical torque, real and reactive powerwith time respectively. It was further noted that in the event of heavy fault in one of the phases, the saturation effect occurred in a synchronous machines. Although appeared to be both in positive and negative sizes. It will perform satisfactorily indicating higher degree of efficiency and stability under fault conditions. Finally, an increase in the time lead to corresponding increases in the steady-state conditions of the field current, speed, electrical torque, real and reactive until the time gets to above 10 seconds. It is also noticed that the oscillations stopped completely after 6 seconds for the conventional and 5.6 seconds for saturation effect accept reactive power generated and field current against time.
TABLE OF CONTENTS
Title Page i
Declaration page ii
Certification page iii
Dedication iv
Acknowledgements v
Table of Contents vi
List of Tables ix
List of Figures x
List of Abbreviation xii
Abstract xiv
CHAPTER 1: INTRODUCTION
1.1 Background of the Study 1
1.2 Statement of the Problem 7
1.3 Aims and Objectives of the Study 8
1.3 Scope of the Study 9
1.5 Significance of the Study 9
1.6 Overview of the Study 10
CHAPTER 2: LITERATURE REVIEW
2.1 Theory of Synchronous Machines 12
2.2 Classification of Synchronous Machine 13
2.2.1 Synchronous machine operate as a generator 13
2.2.2 Synchronous machine operator as a motor 14
2.2.3 The basic functions of large synchronous motors 14
2.2.3.1 Large synchronous motor most common faults 15
2.2.3.2 Test methods for evaluating the condition of a synchronous motor 16
2.3 Model Assumptions of Synchronous Machines 16
2.4 Machine Sectionalizing of a Synchronous Machine 16
2.4.1 Rotor sectionalizing 16
2.4.2 Stator sectionalizing of a synchronous machine 17
2.4.2.1 Stator winding of a synchronous machine 17
2.4.2.2 Stator current of a synchronous machine 17
2.4.2.3 Stator mmf of a synchronous machine 18
2.4.3 Sector numbering a synchronous machine 18
2.5 Merits and Demerits of a Synchronous Machine 18
2.6 Previous Works on a Synchronous Machine with Saturation Effect 19
2.7 Research Gap 36
CHAPTER 3: MATERIALS AND METHODS
3.1 Material for the Study 37
3.2 Dynamic Modeling of Synchronous Machine 37
3.3 Electrical Model of a Synchronous Machine 37
3.3.1 Park’s transformation and d-q modeling of synchronous generator 38
3.3.2 Stator voltage equations in arbitrary reference-frame variables 40
3.3.3 Voltage equations in rotor reference-frame variables, Park’s equations 41
3.4 Mechanical Model Development of a Synchronous Machine 44
3.4.1 Saturation effects of synchronous machines 45
3.5 Air gap saturation effect of synchronous machine 46
3.6 Computer Simulation 48
3.6.1 Conventional model of a synchronous machine 48
3.6.2 Saturation effect simulink model of the study 50
3.7 The Analysis of sub-system block diagram of a conventional and saturation effect of simulink models of synchronous generator 51
3.7.1 Simulink model transformation of abc2qdo sub-system synchronous generator 51
3.7.2 Simulink model for transformation of abc2qdo sub-system block 52
3.7.3 Simulink model of the Q-circuit sub-system block 53
3.7.4 Simulink Model of the inside D-cct sub-system block 54
3.7.5 Simulink model of the rotor sub-system block 55
3.7.6 Simulink model of the qd Sub – system block 56
3.7.7 Simulink model of the OSC sub-system block 57
3.7.8 Simulink model of the transformation of qdr2abc sub-system block 58
3.7.9 Simulink model of the VIPQ sub-system block 58
3.7.10 Overall simulink model diagram of the a synchronous generator 59
3.8 Saturation Effect Simulink Model of transformation of abc2qdo synchronous generator 60
3.8.1 Simulink model transformation of abc2qdo sub-system block 61
3.8.2 Simulink model of the Q-circuit sub-system blocK 61
3.8.3 Simulink model of the D-circuit sub-system block 62
3.8.4 Simulink model of the Rotor sub-system block 63
3.8.5 Simulink model of the qd sub – system block 64
3.8.6 Simulink model of the OSC sub-system block 65
3.8.7 Simulink model of the transformation of the qdr2abc sub-system block 66
3.8.8 Simulink model of the VIPQ Sub-System Block 66
3.8.9 Overall simulink model diagram of the a synchronous generator with saturation effect 67
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Results of the Study 69
4.2 Simulation Results of a conventional Simulink model of a synchronous generator 71
4.3 Simulation Results of the Saturation Effect model of a synchronous generator 79
4.4 Simulation Results of the Conventional and Saturation Effect models 87
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 98
5.2 Recommendations 99
5.3 Contribution to the knowledge 110
REFERENCES
APPENDICES
LIST OF TABLES
4.1 The machine parameters of the Simulink Model synchronous generator 70
4.2: Comparison of the dynamic performances of conventional and saturation effect for field current 88
4.3: Comparison of the conventional and saturation effect models for speed time 89
4.4: Comparison of the dynamic analysis of conventional and
saturation effect of the instantaneous electrical current 90
4.5: Comparison of the dynamic analysis of the real power
generated 91
4.6: Comparison of the dynamic analysis of conventional and
saturation effect of reactive power 93
4.7: Comparison of the dynamic analysis of the Conventional and saturation effect models for the instantaneous current graph 93
LIST OF FIGURES
1.1: Schematic Power flow for Normal Generator Operations 3
3.1: D-Q component axes superimposed on a three-phase synchronous machine 38
3.2: Open circuit saturation curve of a synchronous machine 46
3. 3: Simulink model of equations (3.133-3.35) 52
3.4: Simulink Model transformation of abc2qdo and qds2qdr 53
3.5: Simulink model of the Equation (3.153) - (3.156) 53
3.6: Simulink Model Equation (3.145–3.151) 55
3.7: Simulink model of Equation (3.152) – (3.156), the Rotor-cct sub-system 56
3.8: Simulink model of the equations (3.41-3.56), qd-cct64 57
3.9: Simulink model of the equations (3.157-3.58) 57
3.10: Simulink model of the Equation (3.159) – (3.163) 58
3.11: Simulink model of Equations (3.164)- (3.167) 59
3.12: General Simulink Model of a Conventional Synchronous Generator 60
3.13: Simulink model equations of transformation of abc2qdo Sub-System Block 60
3.14: Simulink model equations of 61
3.15: Simulink Model of Equation (3.176) - (3.179) 62
3.16: Simulink Model Equation (3.180) – (3.186) 63
3.17: Simulink Model of Equation (3.187) – (3.191) 64
3.18: Simulink model Equations (3.176) – (3.191) 64
3.19: Simulink model of equations (3.92-3.93) 65
3.20: Simulink Model of Equation (3.194– 3.198) 66
3.21: Simulink Model Equation (3.199– 3.102) 67
3.22: Simulink Model of equation (3.160-3.102) of Synchronous Generator with Saturation Effect 68
4.1: Response of synchronous generator to step changes in Tmech of Stator Voltage Magnitude against Time 71
4.2: Response of synchronous generator to step changes in Tmech of Stator Current Magnitude against Time 72
4.3: Response of synchronous generator to step changes in Tmech of a Real Power Generated (pu) against Time(sec) 73
4.4: Response of synchronous generator to step changes in Tmech of a Reactive Power Generated (pu) against Time (sec) 74
4.5: Response of synchronous generator to step changes in Tmech of Power angle (rad) against Time(sec) 75
4.6: Response of synchronous generator to step changes in Tmech of an Instantaneous electrical torque(pu) against Time(s) 76
4.7: Response of synchronous generator to step changes in Tmech of a Field Current against Time 77
4.8: Response of synchronous generator to step changes in Tmech of an Instantaneous Armature Current (pu) against Time (sec) 78
4.9: Response of synchronous generator to step changes in Tmech for Saturation Stator Voltage Magnitude against Time (secs) 79
4.10: Response of synchronous generator to step changes in Tmech For Saturated Effect Stator Current against Time 80
4.11: Response of synchronous generator to step changes in Tmech for Saturation of Real Power Generated (pu) against Time (sec) 81
4.12: Response of synchronous generator to step changes in Tmech for the Saturated Model Reactive Power Generated (pu) against Time (sec) 82
4.13: Response of synchronous generator to step changes in Tmech for Saturation of Power angle (rad) against Time(sec) 83
4.14: Response of synchronous generator to step changes in Tmech For saturation of an Instantaneous electrical torque(pu) against Time(sec) 84
4.15: Response of synchronous generator to step changes in Tmech For saturation of a Field Current (pu) against Time (sec) 85
4.16: Response of synchronous generator to step changes in Tmech For saturation of an Instantaneous Armature Current (pu) against Time(sec) 86
4.17: The comparison graph of field current against time, between Saturated and non-saturated model 87
4.18: The comparison graph of speed against time, between
Saturated and non-saturated model 88
4.19: A graph of Power Angle Delta (rad) against time (sec) 89
4.20: A graph of Instantaneous electrical Torque against Time 90
4.21: A graph of Pgen against time for the two models 91
4.22: A graph of Qgen (pu) against time (secs) 92
4.23: Comparison graph of armature current against time 93
LIST OF SYMBOLS AND ABBREVIATIONS USED
r_s Amature winding resistance
r_f D-axis field winding resistance;
r_g Q-axis damper winding resistance
r_kd D-axis damper winding resistance (reflected to the stator);
r_kq Q-axis damper winding resistance (reflected to the stator);
X_ls The stator winding leakage reactance
X_laq Q-axis damping winding leakage reactance
X_ad D-axis damping winding leakage reactance
X_f The field winding leakage reactance
X_q Q-axis non-saturated synchronous reactance
X_d D-axis non-saturated synchronous reactance
X_mq Q-axis non-saturated magnetizing reactance
X_md D-axis non-saturated magnetizing reactance
X_mqs Q-axis saturated magnetizing reactance
X_mds D-axis saturated magnetizing reactance
ψ_m Magnetizing flux per second
I_m Magnetizing current
W Rotor speed;
P Number of poles
V_qs Armature q axis terminal voltage;
V_ds Armature d axis terminal voltage;
i_qs Armature q axis terminal current;
i_ds Armature d axis terminal current;
V_fd Field winding terminal voltage (reflected to the stator);
i_fd Field winding terminal current (reflected to the stator);
i_kd d-axis damper winding current (reflected to the stator);
i_kq q-axis damper winding current (reflected to the stator);
L_ls armature phase leakage inductance;
L_md d-axis coupling inductance;
L_lfd Field winding leakage inductance (reflected to the stator);
L_lkd d-axis damper winding leakage inductance (reflected to the stator);
L_mq q-axis coupling inductance;
L_lkq q-axis damper winding leakage inductance (reflected to the stator);
T_l load torque;
AC Alternating Current
MMF magneto- motive Force
ODE Ordinary Differential Equation
H Inertia constant in seconds
Qdo Quadrature , Direct and Zero axes components
EMF Electro- Motive Force
v_f Field winding voltage
v_d D-axis component of the stator winding voltage
v_q Q-axis component of the stator winding voltage
i_d D-axis component of the stator winding current
i_q Q-axis component of the stator winding current
i_f Field winding current
i_aq Damping winding current
i_ad Damping winding current
r_s The stator winding per phase electrical resistance
r_f The field winding electrical resistance
r_aq Q-axis damping winding electrical resistance
r_ad D-axis damping winding electrical resistance
ω_r The rotor electrical angular speed
ω_b The base electrical angular speed
ψ_q q-axis stator winding phase linkages flux per second(voltage)
ψ_d d-axis stator winding phase linkages flux per second(voltage)
ψ_f Field winding linkages flux per second(voltage)
ψ_aq Q-axis damping winding linkages flux per second(voltage)
ψ_ad D-axis damping winding linkages flux per second(voltage)
D The differential operator
P The machine pole number
J The inertia moment of the machine and turbine motors
T_a The driving torque
T_e The machine electromagnetic torque
θ_r The angular position of the q-axis referred to the stator winding phase- a magnetic field axis
θ_e Theangular position of the maximum value of the stator winding phase-a voltage
ω_r The stator winding voltage electrical angular speed (Synchronous machine)
ω_m The mechanical angular speed
δ The load angle of the machine
ω_b Base frequency
〖T'〗_do D-axis transient time constant
〖T'〗_qo Q-axis transient time constant
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Synchronous machines have long been used as alternating current generators for many industrial applications due to its robustness, ease of construction, accepted level of efficiency and stability. An AC electric motor in which, at steady-state, the rotation f the shaft is synchronized with the frequency of the supply current, the rotation period is exactly equal to an integral number of AC cycles (Fitzgerald et al., 1972). They supply the electric power issued by all sectors of modern society. Synchronous machine is an important electro-mechanical energy converter, it convert mechanical power into AC electrical power.
The synchronous generator is also called alternator is used in alternating power in an AC system. Since the power grid operates at a fixed frequency, the alternator need to run at an appropriate speed to produce power at the desired frequency. The synchronous machines have a standard for industrial electrical drives (Levi et al., 2007). It has replaced the old DC drive systems due to factors such as cost, reliability, and operation free maintenance.
The most widely used types of AC motor is the synchronous machines, this is because the motor rotates at a rated locked to the line frequency since it does not rely on current induction to produce the rotor’s magnetic field. Small synchronous motors are used in timing applications such As in synchronous clocks, timers in appliance, tape recorders and precision. In higher power industrial sizes, the synchronous motor provides two important functions. First, it is highly efficient means of converting AC energy to work. Secondly, it can operate at leading or unity power factor and thereby provide power-factor correction.
Synchronous generators operate in parallel forming a large power system supplying electrical power to consumers. It is also built in large units, rating ranging from tens to hundreds of Megawatts (Kothari and Nagarath, 2010).
Synchronous machines have two major parts namely stationary part stator and a rotating field system called rotor. In a synchronous generator, a DC current is applied to the rotor winding producing a rotor magnetic field. The rotor is then driven by external means producing a rotating magnetic field, which induces a 3-phase voltage within the stator winding. Power systems consist of elements for generation, transmission, distribution and loads. Figure 1.1 explain the synchronous machines as the main generating units of power systems. From the load side, synchronous motors are also used. This makes the synchronous machine one of the most important components of electric power systems. The main overall objectives of power systems are security and reliability. Reliable operation of power systems refers to their ability to continuously supply the required electrical energy without interruption under abnormal operating conditions such as faults, switching, and load changes.
In both modes of operation the power system behavior is dependent on the electrical and electromechanical functioning of the machines (Slemon, 1990). The machine is the most widely used type of generator, providing most of the electrical energy available from the national grid, as shown in Figure 1.1. The stator has a standard three-phase ac winding mounted in it and the rotor (the rotating member) has a dc winding that is connected to an external dc supply. For normal generator operation, the machine will be connected mechanically to a drive system such as steam or gas turbine with the stator winding connected to the grid supply (Carpenter, 1968).
The drive system will then be used to attempt to increase the speed of the generator by increasing the mechanical power into the shaft. The generator speed cannot change so the mechanical power is converted to electrical power by the generator and fed out to the mains supply. Control of the rotor dc excitation allows the power factor at which the power is delivered to the grid to be varied. In simplistic terms, the generator can be regarded as having two basic controls: the drive system controlling the total amount of power generated; and the rotor dc excitation controlling the output power factor (Say, 2002).
Figure 1.1: Schematic Power flow for Normal Generator Operation Source: (Carpenter, 1968)
The synchronous machine is the main generating units of power systems. The electrical and electromechanical behaviour of most synchronous machines can be predicted from the equations which described the 3-phase salient-pole synchronous machine. Unlike Induction machine is a workhorse when it comes to converting energy from electrical to mechanical (Park, 1929). There are many challenges of using synchronous machines, they cannot be used for variable speed applications as there is no possibility of speed adjustment unless the incoming supply frequency is adjusted (Variable Frequency Drives).
The motors cannot be used started on load; this is because the starting torque is zero. These motors have the tendency to hunt and also costlier than induction motors. The motors require DC excitation at the rotor and the construction of the machines is more complicated than induction motors. The presence of the collector rings and brushes are required resulting in increase in maintenance.
When a Synchronous Machines/ Generator are subjected to heavy phase faults, it tends to saturation due to the excessive magnetic fields. The field of synchronous machine is excited by an external dc supply to produce the field flux. Field coils are wound around an iron structure, as the field current is keep increasing , the field flux keeps increasing linearly up to a certain point after which the magnetic material gets saturated and the flux stops increasing even if the field current increases. This happens because after a time, all the so called microscopic magnet gets aligned to the applied field direction and the material is said to be saturated. As alternator core iron gets saturated, rate of rise of pen circuit voltage with field current decreases. On the other hand, short circuit current keeps rising linearly with field current. Synchronous reactance (Xs) decreases as core gets saturated. Xs = (open circuit voltage) / (short circuit voltage), for a given excitation.
When a ferromagnetic material is exposed to magnetic field in which it moves, some voltage is induced in the material. If there is an increase in the magnetic field, the voltage is increased up to a point, and this point is called saturation. The result of the saturation effects is a variation of the stator and rotor inductances.
These parameters are used in the mathematical model of the machine and particularly in the electromechanical torque expressions (Boldea et al., 2000). It has been confirmed that including magnetic saturation in the model of synchronous machine plays a vital role in estimating the synchronizing and damping torques which in turns provide more accurate prediction of the behavior of the machine under small and large disturbances. It also has an important role in the modeling of electrical machines (De-mello and Hannett, 1986). It requires information about d- and q-axis magnetizing curves. The d-axis magnetizing cure is simply the open- circuit (no load) characteristics of the machines while the q-axis magnetizing curve is usually not available and one may assume that the level of the saturation of q-axis and d-axis is the same.
This approach leads to single saturation approach which converts an anisotropic synchronous machine into isotropic equivalent. Saturation is mainly a property of iron- it does not manifest itself over a practical range of fluxes in plastic, or other non- ferrous materials.
- The effect of saturation is to lower the synchronous reactance ( to a saturated value)
- Saturation may limit the performance of machines because of high air gap line voltage drop.
- Saturation is often accompanied by hysteresis which results in losses in AC machines.
- Saturation is not present in superconducting machines.
- Saturation effect limits the armature terminal voltage and required large field magnomotive force (mmf).
In some cases, saturation has only a secondary effect upon the overall performance of the machine; in some cases it is very vital, and must be taken into account when predicting the synchronous machine performance. Incorporating saturation into the machine equations which describe its dynamic behaviour is quite involved. The increased use of variable frequency in synchronous motors drives systems has generated enormous interest on the computer simulation of synchronous machines (Krause and Thomas, 1996).
In recent years, the development of high speed computers and power electronics technology with associated high microcontrollers, AC drives systems have become a viable alternative to DC machines for variables speed applications. This increased interest in synchronous motors is mainly because of its merits over other industrial motor types. These advantages include: simplicity, ruggedness, less initial cost, high torque-inertia ratio, capability of much higher speed and very simple to maintenance (Leonard, 1996).
The most vital quality that makes the synchronous motor a viable alternative to DC drive system is its cost per KVA and its suitability in hostile environment. This work were also analysed based on the assumption that the field source of a synchronous machine is on the rotor and the armature winding is on the stator, that is one of the good difference between the synchronous and other machines.
Consequently, the need for the development of accurate models for Synchronous machine becomes highly imperative. This is so because the magnetic field has the field winding wound on the rotating member (rotor) and the armature wound on the stationary member (stator).The stator core is made of insulated steel laminations, in order to minimize eddy current and hysteresis losses. The function of a synchronous machine stator is to provide a rotating mmf to the rotor (Kudarauskas, 2007).
Under dynamic conditions, the lower sections of the rotor bar experience a higher inductance than the upper section of the rotor bar due to non-uniform flux distribution thereby causing the current to flow primarily in the upper portion of the bar. Also, the re-distribution of the current to flowing in the rotor bar effectively increases the resistance of the bar. This phenomenon of decrease in inductance and increase in resistance of the rotor conductors is known as Saturation Effect .This effect is highly noticeable in motors with rotor bars that have a large bar depth to the width ratio and in motors operated over a wide range of frequency-such as synchronous machine. The dynamic analysis and modelling of synchronous machines therefore, involves the development of accurate and reliable models that can adequately account for the machines non-linearities such as saturation effect, with the view of realizing the actual machine performance in the transient conditions. However, in most synchronous machine dynamic problems, is the rotor speed that usually varying and as such the machine’s dynamic differential equations are non-linear.
Consequently, a numerical method such as Runge-kutta, Euler, Adams, Predictor-correction, is usually applied in arriving at a solution. When magnetic saturation in an AC machine is evolved, the theory of main flux saturation in d-q axes remains the best. Because of its simplicity, it is most used in either motoring or generating mode for synchronous or asynchronous machines. The fourth order Runge-kutta methods are widely used in computer solution to transient studies of A.C machines (Rehaoulia et al., 2006). The dynamic models of a round rotor synchronous machine, which take into account saturation effect of synchronous machine are developed and presented in this work using Simulink/MATLAB models. A reason unavoidable and interesting question might be asked. “What is the essence of this research work with saturation effect on synchronous being fully aware that the use of the conventional model has been perfect over the decades?”. The answer to the question is based primarily on the merits of the former over late; some of which are listed down:
- Saturation effect gives accurate and excellent calculation
- The effect help in lifting loads in a wharf since the loads does not affect the speed
- Saturation effects help to predict the stead-state and transient state performances of the synchronous machines.
1.2 STATEMENT OF THE PROBLEM
The synchronous machines with saturation effect has found many applications in the industries, but with challenges related to efficient speed control, fault tolerance, reduces losses and overall system integrity. Previous works in the dynamic analysis of synchronous machines with saturation effect has been developed. Despite the level of researches carried out in this area, there is need for shorter time in computation (without increasing hysteresis losses), improved stability, and dynamic performance analysis are yet to be explored. There is need foe the adoption of Embedded Simulink/MATLAB models.
The operation of a modern system generation, transmission and distribution has posed serious challenges as a result of synchronous generator speed control. Whenever there is a synchronous generator problem, the stations interconnected with the affected stations will also suffer as well. This will encourage power outage and also reduce the quality of electricity supply. Therefore, Synchronous Generator in power system ensures reliability and stability of power supply system, according to Figure 1.1, the absence of synchronous generator causes the system unreliable and at the same time leads to total black out of the entire power system
1.3 AIM AND OBJECTIVES OF THE STUDY
This thesis is aim at investigating the performance of a synchronous machine with saturation effect with a greater interest in embedded SIMULINK/MATLAB models Simulations to improve the saturation effect in electrical engineering energy calculation for system stability.
The main objectives for this research are:
- To investigate the current developments in synchronous machine with saturation effect by adequate review of some literatures.
- To develop a mathematical model of the conventional and saturation effect models.
- To model and simulate the conventional synchronous model and compare it with the saturation effect of synchronous machine.
- To incorporate the saturation effect, (Loads) in the dynamic models of both models.
- To use computer simulations to validate findings.
1.4 SCOPE OF THE STUDY
Dynamic analysis of synchronous machine with saturation effect on MATLAB/Simulink models which is the computing tool for the implementation of the mathematical model will be discussed to ascertain and establish the need for its use in this thesis.
The two commonly used machines are the Induction machines
And the Synchronous machines. The effect of saturation absolutely occurred in both machines. This thesis will be focusing on the synchronous machine only.
Mathematical models of the synchronous machine with saturation effect will be developed and analysis carried out to ascertain the practicability of the models developed. The D-Q reference frame theory will be used as the method of analysis for the synchronous motor since it is suitable for vector control of synchronous machine (Park, 1938). It is very important to briefly examine the need for the d-q reference frame as an analytical tool in the description of the desired mathematical model.
1.5 SIGNIFICANCE OF THE STUDY
A Synchronous generator, connected to an infinite bus which voltage is the generator rated voltage has its stable operating point defined by the rated values: armature voltage, apparent power, speed, power factor and excitation voltage. This set of values defines the load angle, armature winding current and excitation current. Due to economic reason, the synchronous generator operates in the saturated part of the magnetizing curve so that the variables are very sensitive to load and excitation current variations (Shaskshaft and Henser, 1979).
The effect of saturation of a synchronous generator needs to be included in the mathematical model to make it more accurate to represent the machine both in transient and stead-state operation. The excitation current is very vital to power system engineers for electrical energy system generators stability calculation initialization.
It is important that all electrical energy system stability calculations, using simulation, include the saturation effect in the mathematical dynamic model.
System modeling and simulation of the actual physical system offer a better alternative to reduce the enormous effort wasted in designed and testing results. Simulation can be very useful in man scientific and engineering research that proceed as follows (Ong, 1997).
This thesis creates more research work for future researches.
1.6 OVERVIEW OF THE STUDY
Chapter 1 starts with the introductory remark (background of study) and provides a review of basic literature available on specific topics of synchronous machine with saturation effect. An overview of the existing work done is presented. Meanwhile, despite the developmental improvements, research on this area is still on-going; a number of existing advantages were outlined. The objectives of the research are set and explained.
Chapter 2 presents review of synchronous machine with saturation effect. The saturation effect is discussed showing the differences from the conventional model. The D-Q reference frame theory is also discussed to give us the theoretical background. In addition we will discuss extensively the theories of the saturation effect, its applications and need for its adoption as a method for the speed saturation effect.
Chapter 3 discusses the mathematical models of the conventional model of synchronous machine. This chapter further discusses the saturation effect models will be developed for dynamic studies.
Chapter 4 extensively considers the mathematical model of the saturation effect. First, we examine the conventional model of the synchronous machine and by extension, the saturation effect.
Chapter 5 deals with computer simulation of the synchronous machine (conventional and saturation effect models) and their controllers using SIMULINK/MATLAB. The results gotten in this chapter are examined and discussed to ascertain the level of agreement of the model with existing theories.
Chapter 6 is dedicated to the conclusion and recommendations for further work.
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