EE300 Final Report Ritesh Kumar s11048886
Transcript of EE300 Final Report Ritesh Kumar s11048886
Modeling and Simulation of a Synchronous Generator Driven by an
Engine at a Power Station
Ritesh Kumar Student Id No: s11048886
School of Engineering and Physics Faculty of Science and Technology
University of the South Pacific
November 2011.
Supervisor Mr. Mohammed Tazil
School of Engineering and Physics Faculty of Science and Technology
University of the South Pacific
A report submitted in fulfillment of the requirements for the degree of Bachelor of Engineering Technology.
Aim
To model and simulate a Synchronous Generator driven by an Engine at a Power Station
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Objectives
• Model and simulate the Synchronous generator and test with manual controls.
• Behaviour of the Synchronous generator as the load varies.
• Model by connecting a prime mover (diesel engine) to the synchronous generator
and simulate with variable loads.
• Implement Basic Auto control System on the model and simulate for stable power
output
• Model and simulate synchronous generator connected to the grid driven by a
prime mover.
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Declaration of Originality I Ritesh Kumar hereby declare that the report being written in this project is to the best of
my knowledge and belief original, except as acknowledged in the text. The material has
not been submitted previously, either in whole or in part, for a degree at this or any other
institution.
________________________
Ritesh Kumar
(Student ID No. s11048886)
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Acknowledgments
I would like to take this opportunity to thank all those people who assisted and supported
me over the course of this project.
First and foremost, I would like to thank my project supervisor Mr. Mohammed Tazil for
his constant encouragement, guidance, enthusiasm and support throughout this project.
Without his vision and unlimited support such a project would not have been possible.
Secondly, I am very grateful to all the academic and technical staff members of the
School of Engineering and Physics for their encouragement and support during the phase
of this project.
All my friends, colleagues and relatives deserve earnest thanks for their support,
encouragement and understanding.
Finally, I thank the almighty lord for giving me strength and helped me built faith in
doing this project also I would like to thank the lord for giving me such wonderful
family members, without their support and understanding this project would not have
been possible.
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List of Figures
Figure: 1.1 Shows the picture of a wind turbine with its components 3
Figure: 1.2 Block diagram of the wind power generation system. 4
Figure: 1.3 Model of the wind turbine system in Simulink 4
Figure: 1.4 Shows the picture of steam turbine generator system 6
Figure: 1.5 Simulink model for control of a steam turbine generator. 7
Figure: 1.6 shows the picture of the hydro power plant station 8
Figure: 1.7 Simulink model for hydro electric generator 9
Figure: 1.8 Shows the diesel engine cycle with its intakes 10
Figure: 1.9 Block diagram of the diesel power generation system. 11
Figure: 1.10 Shows Simulink model of a generator set operating on a local
grid
12
Figure: 1.11 Shows the emergency diesel generator set 13
Figure: 2.1 shows cutaway view of a synchronous AC generator with a
solid cylindrical rotor capable of high speed rotation
16
Figure: 2.2 The full equivalent circuit for a three-phase synchronous
generator
17
Figure: 2.3 Shows Phasor diagram of a unity power factor load, (b)
voltage and current response of a resistive load
17
Figure: 2.4 shows Phasor diagram of a lagging power factor load, (b)
voltage and current response of a inductive load
18
Figure: 2.5 Shows Phasor diagram of a leading power factor load, (b)
voltage and current response of a capacitive load
18
Figure: 2.6 Synchronous Machines model in SimPowerSystem library 19
Figure: 2.7 shows the model of the synchronous machine that was used
for simulation
20
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Figure 3.1
Block diagram structure of the diesel-engine generator
governor
21
Figure 3.2 Block diagram of a PID controller 23
Figure: 3.3 Block diagram of engine speed control system, Implemented
PID speed Controller
25
Figure: 3.4 diesel engine governor system 26
Figure: 3.5 Model of the diesel engine governor system in Simulink 27
Figure: 3.6 Excitation block 30
Figure: 3.7 Model of the speed governor and the excitation in Simulink 30
Figure: 4.1 Preliminary model 1 of the synchronous generator 31
Figure: 4.2 Shows the multimeter results for a 100W active power for
preliminary design 1
32
Figure: 4.3 Three-phase voltage outputs from the scope for preliminary
design 1
32
Figure: 4.4 Three-phase current outputs from the scope for preliminary
design 1
33
Figure: 4.5 Shows the machine outputs for preliminary design 1 33
Figure: 4.6 Preliminary model 2 for the synchronous generator 34
Figure: 4.7 Three-phase voltage outputs from the scope for preliminary
design 2
35
Figure: 4.8 Three-phase current outputs from the scope for preliminary
design 2
35
Figure: 4.9 The unity power factor form preliminary design 2 36
Figure: 4.10 The lagging power factor form preliminary design 2 36
Figure: 4.11 standalone model 37
Figure: 4.12 Unity power factor for a 1MW resistive load 38
Figure: 4.13 The synchronous machine outputs for 1MW Active Power
load
38
Figure: 4.14 lagging power factor for a 35KW active power and 20KW 39
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reactive power
Figure: 4.15 The synchronous machine outputs for 35KW Active Power
load and 20KW Reactive Power load
39
Figure: 4.16 Powergui block 40
Figure: 4.17 Load flow and Machine initialization block 41
Figure: 4.18 Steady state peak voltages and currents for a 800KW Active
Power Load
41
Figure: 4.19 Steady state rms voltages and currents for a 800KW Active
Power Load
42
Figure: 4.20 Steady state peak voltages and currents for a 500KW Active
Power Load and 800KW Reactive Power load
42
Figure: 4.21 Steady state rms voltages and currents for a 500KW Active
Power Load and 800KW Reactive Power load.
43
Figure: 4.22 Final model connected to the grid 44
Figure: 4.23 Unity power factor for a 1MW active power load 45
Figure: 4.24 Three-phase voltages for a 1MW active power load 45
Figure: 4.25 Three-phase currents for a 1MW active power load 46
Figure: 4.26 Synchronous machine outputs for a 1MW active power load 46
Figure: 4.27 Lagging power factor for a 200KW active power load and
800KW reactive power load
47
Figure: 4.28 Three-phase voltages for a 200KW active power load and
800KW reactive power load
48
Figure: 4.29 Three-phase currents for a 200KW active power load and
800KW reactive power load
48
Figure: 4.30 Synchronous machine outputs for a 200KW active power
load and 800KW reactive power load
49
Figure: 4.31 Leading power factor for a 100KW reactive power load 50
Figure: 4.32 Three-phase voltages for a 100KW reactive power load 50
Figure: 4.33 Three-phase currents for a 100KW reactive power load 51
Figure: 4.34 Synchronous machine outputs for a 100KW reactive power 51
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load
Figure: 4.35 Active and Reactive block Added to the Final model 52
Figure: 4.36 Active and Reactive Power Supplied to the grid after
simulating a 1MW active power load (resistive load)
53
Figure: 4.37 Active and Reactive Power Supplied to the grid after
simulating a 200KW active power load and a 800KW reactive
power load (inductive load).
53
Figure: 4.38 Active and Reactive Power Supplied to the grid after
simulating a 100KW reactive power load (capacitive load).
54
Figure: 4.39 Synchronous machine outputs 55
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List of Tables
Table 2.1 Synchronous machine Parameters 19 - 20
Table 3.1 The table below summarizes the PID terms and their
effect on a control system.
24
Table: 4.1 Results for different sizes Active Powers (Resistive
loads) used in for simulation
44
Table: 4.2 Results for different sizes Reactive Powers (Inductive
loads) used in for simulation.
47
Table: 4.3 Results for different sizes Reactive Powers (Capacitive
loads) used in for simulation.
49
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Table of Contents
Aim i
Objective ii
Declaration of Originality iii
Acknowledgements iv
List of Figures v
List of Tables ix
Table of contents x
Abstract xii
Chapter 1 Introduction and Literature Review
1.1 Introduction 1
1.2 Literature Review 2
1.2.1 Wind Power 2
1.2.2 Biomass Power 5
1.2.3 Hydroelectric Power 8
1.2.4 Diesel Power 10
1.2.5 Matlab/Simulink software 14
Chapter 2 Synchronous Machine (Generator)
2.1 Introduction 15
2.2 Behavior of synchronous machine with different types of
loads
17
2.3 Simulink Model of Synchronous Machine 18
2.4 Synchronous Machine Used in Simulation. 19
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Chapter 3 Diesel Engine
3.1 Introduction 21
3.2 Speed Control of the Diesel Engine 22
3.3 PID Controller 23
3.4 Actuator Design 25
3.5 Voltage Regulator 27
Chapter 4 Simulation Results
4.1 Introduction 31
4.2 Modeling of the synchronous generator 31
4.2.1 Preliminary Model 1 31
4.2.2 Preliminary Model 2 34
4.3 Standalone model 37
4.4 Load Flow and machine initialization 40
4.5 Final Model connected to the Grid 43
4.6 Synchronous Machine Outputs 54
4.7 Loading effects on the synchronous generator 56
Discussion 57
Conclusion 58
Future Recommendations 60
References 61
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Abstract
This report presents the modeling and simulation of a synchronous generator driven by a
diesel engine at a power station. The modeling process involves reviewing of literature
and exploring what work has been already done in this area. The models were achieved
after studying various simulations of power systems. The simulation was done using the
Matlab/Simulink software package. Using software modeling of a diesel generator
system provides an in-depth understanding of the system operation before building the
actual system. Also the testing and experiments of the system operation under
disturbances is not possible on the actual system. Individual system components such as
the synchronous generator were simulated with constant values and the results were
analyzed. Stability aspects of the synchronous generator driven by diesel engine with
various types and sizes of load were also analyzed and discussed in detail. Finally,
recommendations were given for future work and conclusion made.
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Chapter 1
Introduction and Literature Review
1.1 Introduction
The increasing demand for energy, the continuous decrease in the current available
resources of fossil fuels and the growing concern regarding environmental pollution have
forced mankind to discover new production technologies for electrical energy using clean
renewable sources such as wind energy, solar energy and water energy.
The renewable sources of electric power technologies such as wind, solar and hydro are
clean, silent and reliable, with low maintenance costs and small environmental impact.
The sunlight, kinetic energy of flowing water and kinetic energy of the wind are free,
practically unlimited, however, electric power production systems using as primary
sources completely pose problems such as wind speed fluctuations during day, night,
summer and winter. Also not enough water in the damn to run the hydro turbines and
lack of sunlight for solar panels cannot produce enough power to meet the demand. As a
result, in autonomous regimes, to meet the demand of the power supply to the local grid
should be backed-up by other reliable sources of primary energy, such as diesel generator
sets. The combined sources of primary energy with diesel generator sets are known as
hybrid systems and are designed for decentralized production of electric power. By
combining renewable energy sources of wind, solar and diesel increases the reliability of
supply of electricity to the consumers.
The increased interest in using diesel generator sets as the main source in isolated areas
or as an emergency source has been very reliable and economical. Diesel generators
provide continuous electric power to the grid when the renewable sources of energy are
insufficient and unavailable. The diesel generator sets convert the chemical energy from
the fuel into mechanical energy by the means of internal combustion engines. The
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synchronous generator is main part of the diesel generator set as it converts the
mechanical power produced from the diesel engine to electrical power. The analysis of
various complex aspects of diesel generator sets is done through software modeling and
simulation. The simulation of the diesel generator is done in different regimes and the
behavior of the machine is analyzed.
For this proposed project refers to the modeling and simulation of a synchronous
generator driven by a diesel engine at a power station. The system is connected to the
grid and the behavior of the system is analyzed in detail.
1.2 Literature Review
Engineers have developed numerous methods of controlling stable power output.
Software’s are mostly used to control the power system at power stations. The prime
mover always provides mechanical power to the synchronous machine to deliver
electrical power. However, the system has to precisely maintain constant voltage and
frequency at all times. These parameters widely simulated and controlled using numerous
power software’s.
A lot of research has been done in these areas to control for stable power outputs through
simulation. Different types of prime movers behave differently with the synchronous
machine and are accordingly modeled and simulated for a stable power output .The
following sections describe the types of modeling and simulation of various power
generation systems.
1.2.1 Wind Power
The increasing capacity of wind power penetration is one of today’s most challenging
aspects in power-system control [2]. The synchronous generator is driven by the wind
turbine which acts as the prime mover. The Kinetic energy of the wind is changes to the
mechanical energy which drive the electric generator to produce electricity.
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The wind blows on the blades of the turbine and makes them turn which turns the shaft
inside the nacelle (the box at the top of the turbine).The shaft goes into a gearbox which
increases the rotation speed enough for the generator, which uses magnetic fields to
convert the rotational energy into electrical energy. The power output goes to a
transformer, which converts the electricity coming out of the generator to the right
voltage for distribution system.
Figure: 1.1 shows the picture of a wind turbine with its components.
The instruments to measure the wind speed and direction are fitted on top of the nacelle.
When the wind changes direction motors turn the nacelle, and the blades along with it,
around to face the wind. The nacelle is also fitted with brakes, so that the turbine can be
switched off in very high winds, like during storms. This prevents the turbine being
damaged. All this information is recorded by computers and transmitted to a control
center, which means that people don't have to visit the turbine very often, just
occasionally for a mechanical check [4].
Various software’s methods are used by electrical engineers to study the load flow,
steady state voltage stability, dynamic and transient behavior of power systems through
computer models. This application is also applied to the wind turbine power generation
system. Today these tools must incorporate extensive modeling capabilities with
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advanced solution algorithms for complex power-system studies, as in the case of wind
power applications [3].
Figure: 1.2 Block diagram of the wind power generation system.
The Figure below shows the modeling and simulation of the wind turbine power
generation in MATLAB/Simulink software. A 30kw 480V permanent magnet
synchronous generator (PMSM) is used to provide power to the grid.
Figure: 1.3 Model of the wind turbine system in Simulink
Advantages of wind Power
• Wind is free and in abundance.
• Installing the wind turbines for the first time is expensive while maintain is not
very expensive.
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• It can be used to generate own power where the country grid cannot supply.
• Installing the wind turbine may take a very small piece of land while taking the
components up may be challenging.
• No pollution – clean power.
Disadvantages of wind Power
• A number of pollutants are given off into the surrounding in creation of the wind
turbines.
• Wind turbines are quite noisy.
• The wind speed is not constant hence there is no definite supply of electricity
always.
1.2.2 Biomass Power
Biomass energy is important for dual applications such as heat and power generation. It is
a clean renewable energy resource derived from the waste of human and natural
activities. It excludes organic material which has been transformed by geological process
into substances such ac coal and petroleum. The biomass energy is extracted from wood,
waste, alcohol fuels, crops, landfill gases.
Producing energy from biological mass (biomass) is a quite simple process. The bi-
product such as wood or crop remaining is burnt in furnaces. The created is used to boil
water and the energy from the steam is used to rotate turbines of the electric generators.
Sometimes it is also called steam turbine generators. Also when garbage is burned or
allowed to decompose it gives out methane gas which is also known as landfill gas. These
gases are collected and used to make energy for the power plants. This is also known as
gas turbine generators where the gas is used to turn the turbines.
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Figure: 1.4 Shows the picture of steam turbine generator system
This system is widely used by many industries to produce in-house power and also by
countries to meet consumers’ power demand. However, the control of stable power with
different load and frequency is done through computer software’s. The Figureure below
shows a 600MVA 22kV synchronous generator driven by a steam turbine for stable
power output. The software used for simulation is Matlab/Simulink.
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Figure: 1.5 Simulink model for control of a steam turbine generator.
Advantages of biomass energy
• Biomass does not add co2 to the atmosphere as it absorbs the carbon in growing as
it releases when consumed as fuel.
• Can be used with the same power plants that are used for fossil fuels.
• It’s cheap and also sensible to use waste products
• Reduces dependence on foreign oil and biomass energy has the potential to
greatly reduce greenhouse gas emissions.
Disadvantages of Biomass energy
• Sufficient quantity of waste may not be readily available
• Very little greenhouse gases are created while burning the fuel.
• Some materials are not always available.
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1.2.3 Hydroelectric Power
Hydroelectric power plants produce about 24 percent of the world’s electricity which
supply more than one billion people with power. According to the National Renewable
energy Laboratory, the total output of the world’s hydropower plants is about 675,000
megawatts, which is equal to the energy of 3.6 billion barrels of oil.
Hydro power is the process of changing the kinetic energy of flowing water in a reservoir
into electrical power that we can use. The turbine acts as a prime mover for the
synchronous generator. The turbines are turned by the flowing water from the dam which
converts the kinetic energy of the water to mechanical energy. This mechanical energy is
used by the synchronous generator to produce electricity. Then the transformer in the
power house transforms the electricity into a usable form, and the electricity travels
through the power lines and goes for commercial and business use.
Figure: 1.6 shows the picture of the hydro power plant station
However, the control of steady state voltage, load flow and dynamic and transient
behavior of power systems is done through standard software simulated by electrical
engineers. The Figure below shows an example a hydroelectric turbine modeled in
Matlab/Simulink Software for control power output. A 200MVA 13.8kV synchronous
machine has been used for supplying stable power.
8
Figure: 1.7 Simulink model for hydro electric generator
Advantages of Hydro Power
• Pollution and waste free
• It’s a renewable energy source
• Very reliable and not expensive to maintain once the dam has been built
• Can increase and decrease the production depending on the demand of power
• Water can be stored and used in peak times.
Disadvantages of Hydro Power
• It takes a lot of time and expensive to build a dam.
• The dam will change the habitat and landscape, as much more land will be
submersed.
• The land below the dam is also affected as flow of water is reduced.
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1.2.4 Diesel Power
In today’s world, where fuel prices are rapidly increasing as a result of rise in its demand
and minimal supply one needs to choose a cost effective fuel to meet their demand. The
diesel engine has proved to be extremely efficient and cost effective. The price of diesel
fuel is much higher than gasoline but diesel has a higher energy density than gasoline.
Diesel engines are widely used as a prime mover to provide mechanical power for the
synchronous generator to produce electricity.
A diesel generator consists of an internal combustion (IC) engine and a synchronous
generator coupled on the same shaft. The internal combustion engines convert chemical
energy from the fuel to mechanical energy. The pistons of the engine are connected to the
crankshaft, and the up-down motion of the pistons, known as the linear motion, creates
the rotary motion needed to turn the shaft of the synchronous generator. In a diesel air is
compressed first and then the fuel is injected because air heats up when it is compressed
and the fuel ignites.
Figure: 1.8 Shows the diesel engine cycle with its intakes
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The diesel engine uses a four-stroke combustion cycle. The four strokes are:
• Intake stroke – the air moves in through the intake valve and moves the piston
down. Compression stroke -- The piston moves back up and compresses the air.
• Combustion stroke – When the piston reaches the top, fuel is injected and
ignited, forcing the piston to move down again.
• Exhaust stroke -- The piston moves back to the top, and pushes the exhaust out
from the exhaust valve which was created from combustion.
The diesel generator sets are usually designed to run at 3000 rpm or 1500 rpm at a
frequency of 50 Hz. The internal combustion engine is equipped with mechanical
regulators to keep the desired speed, coupled in the injection pump and adjusted to obtain
an output frequency of about 52 Hz without load and 50 Hz for rated load. . The speed
regulator and voltage regulator are two major components of a diesel generator set. The
performance of these components is vital for the operation and utilization of diesel
generator set, their purpose is to exactly maintain the desired voltage and frequency.
Figure: 1.9 Block diagram of the diesel power generation system.
The analysis of the complex aspects of a diesel generator set requires the development of
reliable numerical models that allow for simulation in different operation systems,
specifically in conditions as close as possible to the reality of the assembly internal
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combustion engine and the synchronous generator. The synchronous generator
represents a key component of a diesel generator set. It converts the mechanical power
produced by the primary mover into electrical power [5]. The Figureure below shows a
diesel engine modeled with a synchronous generator for constant frequency and voltage
outputs.
Figure: 1.10 Shows Simulink model of a generator set operating on a local grid
Diesel generators can be used as prime source of power or as a backup power. During the
grid blackout one can use the generator set as back up to supply power. Also when there
is less power supplied by renewable sources such as hydro and wind, diesel generator set
can be used to generate power to the grid.
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Figure: 1.11 shows the emergency diesel generator set
Advantages of diesel Power
• Modern diesel engines have overcome disadvantages of earlier models of higher
noise and maintenance costs.
• Fuel cost is low and is highly efficient and produces higher torque compared to
other fuels.
• There is no sparking as the fuel ignites. The absence of spark plugs lowers
maintenance costs.
• A diesel generator has a longer life compared with gas generators.
• Out of all the fuels diesel is least flammable and fuel is readily available.
Disadvantages of diesel Power
• The startup during cold conditions takes some time.
• The cost of buying a diesel generator is quite expensive though the maintenance
is cheap.
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• The installation process and its period take a lot of time and consume higher cost
than installation of other generators.
• Light loads can cause a diesel generator to experience “wet stacking.” This causes
the engine to run rough and smoke.
1.2.5 Matlab/Simulink software
MATLAB is a general purpose mathematical convenient program which provides
editing, plotting, debugging, and graphics capabilities, as well as access to an extensive
and sophisticated library of dominant computational processes, and is becoming widely
used throughout the engineering community [5]. Simulink is a software package designed
to run within MATLAB. Simulink can be used for modeling, simulating, and analyzing
energetic system, whose performance is described with sets of differential equations. The
package has a graphical user interface (GUI) for building the dynamic system model from a
comprehensive library of built-in or user-defined, functional blocks.
The main advantages of using MATLAB- Simulink are:
• Fast development of the product
• Access to stylish reliable mathematical solution algorithms
• Assistance in output control, particularly with regards to graphics and results [5].
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Chapter 2
Synchronous Machine (Generator)
2.1 Introduction
Synchronous generators are primary source of energy. Large- scale of power is generated
by three-phase synchronous generators, known as alternators, driven by steam turbines,
gas turbines, reciprocating engines and hydro turbines. The synchronous generator
converts mechanical energy produced by the engines and turbines to electrical power for
the grid. Synchronous generators can extremely generate large amount of power up to
1500MW. Synchronous machines always operate at synchronous speed because the rotor
speed always matches to the supply frequency.
The armature windings of the synchronous machine are placed on the stationary part called
stator. The armature windings are designed for generation of balanced three-phase voltages
and are arranged to develop the same number of magnetic poles as the field winding that is
on the rotor [6]. The field requires a two to three percent of the machine rating power for its
excitation. The rotor is mounted on a shaft driven by prime mover. A field winding carries a
DC current to produce a constant magnetic field. An AC voltage is induced in the three-
phase armature winding to produce electrical power. The electrical frequency of the three-
phase output depends upon the mechanical speed and the number of poles. The synchronous
speed is given by the formula:
����� =120��
Where:
����� = synchronous speed
F = system frequency
P = number of poles
There are two types’ synchronous generators, stationary field and revolving field. For the
stationary field generators, poles on the stator (field winding) are supplied with DC to
create a stationary magnetic field and the armature windings on the rotor consist of three-
15
phase windings whose terminals connect to three slip rings on the shaft. The brushes
connect the armature to the external three-phase load. These arrangements work for low
power machines less than 5KVA. Revolving field synchronous generators are commonly
known as alternators. These generators are used for large power generation. Revolving
synchronous generators has a stationary armature with three-phase winding on stator
while the three- phase is directly connected to the load. The rotating magnetic field is
created by DC field windings on rotor powered by slip-rings/brushes.
Figure: 2.1 shows cutaway view of a synchronous AC generator with a solid cylindrical
rotor capable of high speed rotation
The most suitable way to determine the performance characteristics of synchronous
generators is by means of equivalent circuits. These equivalent circuits can become very
useful when analyzing machine losses and performance. The following Figureure shows
the equivalent circuit of a three phase synchronous generator. Where, Xs is the
synchronous reactance, EA is the internal generated voltage, Va123 is the phase voltage, RA
is the series resistance, Vf is the field voltage, Radj adjustable resistor which controls the
flow of field current and RF ,LF are the coil inductance and resistance in series.
16
Figure: 2.2 The full equivalent circuit for a three-phase synchronous generator
2.2 Behavior of synchronous machine with different types of loads
Power Factor is defined as the fraction of the apparent power that is actually supplying
real power to a load. It is always between the numbers 0 to 1. The three types of power
factors are listed below.
� Unity power factor - In an AC circuit that is purely resistive current and voltage
are in-phase, the power factor is unity.
Figure: 2.3 (a) shows Phasor diagram of a unity power factor load, (b) voltage and
current response of a resistive load
17
� Lagging power factor - In an AC circuit that is inductive, current and voltage are
out of-phase, the impedance angle (j) is positive and current lags voltage by a
phase angle (Φ).
Figure: 2.4 (a) shows Phasor diagram of a lagging power factor load, (b) voltage and
current response of a inductive load
� Leading power factor – in an AC circuit that is capacitive, current and voltage
are out of phase, the impedance angle (J) is negative, and the current leads the
voltage phase angle (Φ) .
Figure: 2.5 (a) Shows Phasor diagram of a leading power factor load, (b) voltage and
current response of a capacitive load
2.3 Simulink Model of Synchronous Machine
The SimPowerSystem is part of the Simulink library that contains all the synchronous,
asynchronous and DC machines. The SimPowerSystem library contains six different
models of the three-phase synchronous machines with its parameters in PU standard and
in SI standard. The synchronous machines can be operated in both motor mode and in
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generator mode. If the mechanical power for the machine is negative it operates in motor
mode and if the mechanical power supplied is positive the machine operates in generator
mode. The excitation is provided by the built in excitation block available
SimPowerSystem library.
Figure: 2.6 Synchronous Machines model in SimPowerSystem library
The upper row of the Figure 2.6 represents simplified models of the synchronous
generator with permanent magnets on the rotor and the down row represents generators in
PU/SI standards, these can used for modeling of power plants.
2.4 Synchronous Machine Used in Simulation.
The synchronous machine used in the simulation was a 3.125MVA, 2400V and 50Hz.
The machine parameters in PU standard are listed below.
Table 2.1 Synchronous machine Parameters
Direct Axis Synchronous Xd
1.56
Direct Axis Transient X'd
0.296
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Direct Axis Subtransient X"d
0.177
Quadrature Axis Synchronous Xq 1.06
Quadrature Axis Subtransient X"q 0.177
D- axis time constants
Short-circuit
Q - axis time constants
Open -circuit
Leakage reactance Xl 0.052
Direct Axis Open Circuit Transient Td' 3.7
Direct Axis Short Circuit Transient Td" 0.05
Direct Axis Open Circuit Subtransient Tq" 0.05
Stator resistance Rs 0.0036
Inertia coefficient 1.07
Friction factor 0
Pole pairs 2
Rotor type Salient pole
Figure: 2.7 shows the model of the synchronous machine that was used for simulation
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Chapter 3
Diesel Engine 3.1 Introduction
The speed of a diesel-engine generator set is controlled through a speed governor. The
control of a diesel engine can be considered as a speed-feedback system. The operator
gives a change in speed value by adjusting the governor set, the engine governor which is
also acts as sensor, will distinguish the change between the actual speed and the desired
speed, and control the fuel supply to maintain engine speed within the range. The
governor defined as an electromechanical device that automatically controls the speed of
the engine by linking the intake of the fuel. There several types of governors which exist
as mechanical-hydraulic, direct mechanical type, electro hydraulic, electronic, and
microprocessor based governors [7].
Figure 3.1 Block diagram structure of the diesel-engine generator governor
The appropriate operation of a diesel-engine generator is determined to a great extent by
two main components, the speed regulator and the voltage regulator. The performances
of these components are vital for the operation and utilization of diesel-engine generator.
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The purpose of the speed regulator and voltage regulator is to maintain constant voltage
and frequency with any given type and size of load.
3.2 Speed Control of the Diesel Engine
The speed regulator of a diesel-engine generator is designed to maintain constant speed
of the diesel engine. The speed governor changes the amount of fuel used-up by the
motor at different amount of loads to maintain constant speed of the diesel-engine. For
instance, for a constant load the fuel is held steady since desired speed is equal to the
actual speed. If the desired speed and actual speed are different, the fuel setting is
adjusted by the driver to make actual speed equal to the desired speed. The fuel is held
steady until a speed or load changes. As the load increases the speed of the diesel engine
decreases, hence the actual speed gets lower than the desired speed. The fuel supply is
increased to increase the speed of the diesel engine, which returns the actual speed to the
desired speed. More fuel is consumed to pick up the load then to maintain the load. When
the load decreases, the speed of the engine increases and the actual speed get higher than
the desired speed, the fuel input is decreased which decreases the engine speed. The
actual speed returns to the desired speed of the diesel engine.
The speed governor of the diesel engine maintains constant voltage and frequency at the
generator terminals. The frequency is directly proportional to the generator speed. For a
constant frequency the speed governor needs to provide a good accuracy and a short
response time. When various electronic loads are connected or disconnected at the
generator terminals the speed governor starts regulating. There are plenty speed
governing systems, they start from a simple spring base up to complex hydraulic and
electronics ones able to regulate the fuel to maintain the speed of the diesel engine at a
constant value.
However, it is a difficult task to control the speed of power generation plants driven by a
diesel engine as a prime mover. This is due to the presence of a dead time and changes in
parameters, these results plant dynamics [8]. To control the speed many different
approaches has been used. The most widely used controller is a PID controller.
22
3.3 PID Controller
PID stands for Proportional, integral, and Derivative. It is a feedback controller, used to
correct the error between the input and the output. Error is known as the difference
between the actual speed and the desired speed. It is a basic filter device used to regulate
some output based upon the combined function of factors. PID is actually a differential
equation solved in the frequency domain. PID controller is a combination of three
different controllers that is proportional, integral and derivative controller [9].
Figure 3.2 Block diagram of a PID controller
P -Proportional, I - Integral, D - Derivative. These terms define three elementary
mathematical functions applied to the error signal. The controller does the PID
mathematical functions on the error and applies the sum to a process. Tuning a system
means adjusting three multipliers �, � and � adding in various amounts of these
functions to get the system to behave the way you want. The table 3.1 summarizes the
effect of PID on the control systems.
23
Table 3.1 the table below summarizes the PID terms and their effect on a control system.
The transfer function of the PID controller looks like the following:
� � �� � �� = ��
� � �� � ��
Where:
� = ����������������
� = ������������
� = ���!���!�����
The PID transfer function of the diesel-engine generator set is:
"# = $ � � �%�&'� � $ � � �%�&' � �%�'(' � %�) (%∗ +%)
Where:
%� = ���� �������#�
%∗ = �������#����� (%,-.) % = ��������� ���/��0�#/����1���������� % = ��������� ���/��0�#/����1����������
The transfer function of the controller after laplace transformation is:
24
"� = 21 � 345'
21 � 3�' �3�3�'�5
Where:
3�, 3�,34 � 7��1�������8�#��������
Figure: 3.3 Block diagram of engine speed control system, Implemented PID speed
Controller
3.4 Actuator Design
"(')
"9�
:���
'� � ;�:��' �:���
Where:
"(') � ���<���#�1����������=�������1������/������
"9(') � ���<����!����������1���/������
:�� � ���/����1�����#�����������>1��#0���/��#�1����
;� � ���/� �8����#�����#�������/��#�1����
Then the transfer function of the actuator is after Laplace transformation is:
25
"(')"�
= 1 �3?'
'(1 �3@')(1 �3A')
Where:
3?, 3@,3A � B#�1������8�#��������
Figure: 3.4 diesel engine governor system
The above model was to model the diesel engine governor system for the simulation. The
constants values were taken from reference [10]. The engine inertia is combined with the
generator inertia.
The model below shows the model of the system in MATLAB/Simulink.
26
Figure: 3.5 Model of the diesel engine governor system in Simulink
3.5 Voltage Regulator
The excitation block is used for voltage regulation, it is also known as the automatic
voltage regulator (AVR). It controls the voltage at the generator terminals. The voltage
regulator keeps the voltage constant during load variations by limiting voltage peaks and
over voltages as fast as possible. The excitation current is the parameter that changes the
voltage amplitude at the generator terminals. The mathematical implementation of the
excitation system is shown below.
The model of phase-compounding excitation system is expressed d-q component.
C, =D(C� + EF)� � (CF � E�=)� Where:
C, = �/��1��1�!���������/��=#�������1��� C� = �/���8��1�����8����!���������/���������� + �=��
CF = �/���8��1�����8����!���������/����������> + �=�� = √2
H
I
27
The voltage difference model is:
∆C = C,-. � C.K L + CM. � C�MLN + C..
CM. = D(C�)� � $CF&�. 11 � �3,
Where:
C,-. = �������#�!���������/��1��8���#!���������1�����
C.K = �������!��1����/��=#��������0���8
C�MLN = P��1� ���Q���!������
L = �/�����#��!������=#����
3, = ��8�#����������/���R����������
C.. = �1��1�!���������/���� S�#<����
∆C = �/�!������ �������#����������/�#�8���/����!�����
The compensator model is:
C� =∆C 1 � �3�1 � �3N
Where:
C� = �1��1�!���������/�#�8��������
3. = ��8�#����������/�#�8�����������
3N = ��8�#����������/�#�8�����������
The amplifier model is:
CL =C� L1 � �3L
Where:
CL = �/��1��1���!���������/��8�������
28
L = �������/��8�������
3L = ��8�#����������/��8�������
The model of the proportional saturation loop is:
T.� = CL � C, 0 ≤ T. ≤ T.VLW�� T. = T.�
T.VLW = #�������, � = 0
�, XM., � ≥ 0
Where:
T.� = �/��1��1�!���������/�!���������1�����
T. = �/��1��1�!���������/����������������1����������
T.VLW = �/�8�=�818�1��1�!���������/����������������1����������
The mathematical model of the alternating current exciter is given by:
C. = 13- � - T.�
Where:
- = ��8�#����������/������������#1������=#����
The feedback stability loop is given as:
C.. = C. � .1 � �3..
Where:
. = �/���� S�#<����
3.. = ��8�#����������/���� S�#<����
The following model shows the excitation system for the diesel generator system
modeled in Simulink. The block parameters are automatically changed as soon as the
29
load varies for the system. The initial values are implemented by Simulink since the
excitation block is available in the SimPowerSystem library. The X�and XF values are
taken from the synchronous machine output and connected directly the excitation block.
Figure: 3.6 Excitation block
Figure: 3.7 Model of the speed governor and the excitation in Simulink
30
Chapter 4
Simulation Results 4.1 Introduction
The synchronous generator will behave differently with different types of loads. This
chapter will show behavior of the model with different types of loadings and the
procedure followed to model the final circuit.
4.2 Modeling of the synchronous generator
4.2.1 Preliminary Model 1
The first objective of my project was to model and simulate a synchronous generator and
observe the behavior of the machine with different types and sizes of loads. Figure 4.1
first model of the synchronous generator which was made to see the outputs of the
system.
Figure: 4.1 Preliminary model 1 of the synchronous generator
An 8.1KVA 400V 50Hz pu standard synchronous generator was simulated with a 100W
active power (resistive load) and the results are shown below.
31
Figure: 4.2 Shows the multimeter results for a 100W active power for preliminary design
1
Figure: 4.3 Three-phase voltage outputs from the scope for preliminary design 1
32
Figure: 4.4 Three-phase current outputs from the scope for preliminary design 1
Figure: 4.5 Shows the machine outputs for preliminary design 1
The expected results were to get a pure sine wave from the model which was achieved
however the amplitudes were not correct since the generator was 400V and the voltage
output were near 2000V.
33
4.2.2 Preliminary Model 2
Another circuit was modeled using a 2000KVA 400V 50Hz synchronous generator in SI
standard. This time some changes were made to the circuit to compensate for the outputs
which were not correct. A 10KW Active power was used in the simulation. A small
resistance was applied as the resistance of the wire since the synchronous generator
cannot be connected directly to the scope. The model and results are shown below.
Figure: 4.6 Preliminary model 2 for the synchronous generator
34
Figure: 4.7 Three-phase voltage outputs from the scope for preliminary design 2
Figure: 4.8 Three-phase current outputs from the scope for preliminary design 2
However, the results gave pure sine waves for the system but the outputs were still out of
range. The behavior of the machine with a resistive and inductive load was tested and the
results are shown below.
35
Figure: 4.9 The unity power factor form preliminary design 2
Figure: 4.10 The lagging power factor form preliminary design 2
The machine outputs are different with a resistive load and a inductive load. For a
resistive current and voltage and current are in phase whereas for and inductive load
36
current lags the voltage by a phase angle. These two components are shown in Figure 4.9
and 4.10 above.
4.3 Standalone model
After modeling the synchronous machine the standalone model was made by connecting
the diesel engine governor system and the excitation block. A 3.125 MVA 2400 volts
50Hz synchronous generator was used to model the standalone system. The synchronous
machine and diesel engine parameters were taken from reference [6].
Figure: 4.11 standalone model
The standalone system was tested with different types and sizes of loads of which the
results are shown below.
37
Figure: 4.12 Unity power factor for a 1MW resistive load
Figure: 4.13 The synchronous machine outputs for 1MW Active Power load
38
Figure: 4.14 lagging power factor for a 35KW active power and 20KW reactive power
Figure: 4.15 The synchronous machine outputs for 35KW Active Power load and 20KW
Reactive Power load.
39
4.4 Load Flow and machine initialization
The machine state has to be initialized for constant speed and voltage output. The
Powergui block available in the Simulink library allows in doing the load initialization.
As soon as a model is simulated a Powergui block is automatically created. By clicking
on the block various components of the model are shown.
Figure: 4.16 Powergui block
After adding a load the load has to be initialized for constant voltage and frequency. By
clicking on the load flow and machine initialization block and choosing update circuit
measurements, the circuit measurements are automatically changed. The field voltage and
mechanical power values are changed to maintain constant voltage and speed of the
diesel engine.
40
Figure: 4.17 Load flow and Machine initialization block
The steady state current and voltage block determines the peak voltage, peak current, rms
voltage and rms current for that load. It gives the values expected after the simulation of
the model.
Figure: 4.18 Steady state peak voltages and currents for a 800KW Active Power Load
41
Figure: 4.19 Steady state rms voltages and currents for a 800KW Active Power Load
Figure: 4.20 Steady state peak voltages and currents for a 500KW Active Power Load
and 800KW Reactive Power load.
42
Figure: 4.21 Steady state rms voltages and currents for a 500KW Active Power Load and
800KW Reactive Power load.
4.5 Final Model connected to the Grid
The final model was made by connecting all the components to the grid. A 200MVA grid
was used to connect the final model. The behavior of the grid connected synchronous
machine driven by a diesel engine was tested with different types and sizes of loads. the
Figure below shows the final model.
43
Figure: 4.22 Final model connected to the grid
Table: 4.1 Results for different sizes Active Powers (Resistive loads) used in for
simulation
Active Power (W)
Reactive Power (VAR)
RMS Voltage
RMS Current
Frequency (HZ)
Peak Voltage
Peak Current
50000 0 1386 13.03 50 1960.099997 18.42720272
100000 0 1386 24.06 50 1960.099997 34.02597831
150000 0 1386 36.09 50 1960.099997 51.03896747
200000 0 1386 48.12 50 1960.099997 68.05195662
250000 0 1386 60.15 50 1960.099997 85.06494578
500000 0 1386 120.3 50 1958.685784 170.1298916
800000 0 1385 192.4 50 1958.685784 272.0946894
1000000 0 1385 240.5 50 1961.514211 340.1183618
2000000 0 1387 481.18 50 1961.514211 680.4912819
3000000 0 1387 722.5 50 1961.514211 1021.769299
44
Figure: 4.23 Unity power factor for a 1MW active power load
Figure: 4.24 Three-phase voltages for a 1MW active power load
45
Figure: 4.25 Three-phase currents for a 1MW active power load
Figure: 4.26 Synchronous machine outputs for a 1MW active power load
46
Table: 4.2 Results for different sizes Reactive Powers (Inductive loads) used in for
simulation.
Active Power (W)
Reactive Power (VAR)
RMS Voltage
RMS Current
Frequency (HZ)
Peak Voltage Peak Current
20K 35K 1384 9.705 50 1957.27157 13.72494262
100K 80K 1386 30.82 50 1960.099997 43.58606199
100K 150K 1385 45.61 50 1958.685784 64.50228058
100K 200K 1386 53.79 50 1960.099997 76.07054752
50K 250K 1386 61.33 50 1960.099997 86.73371778
200K 500K 1386 129.5 50 1960.099997 183.1406563
500K 800K 1385 226.9 50 1958.685784 320.8850573
1M 2M 1385 528 50 1958.685784 746.7047609
1M 3M 1385 761 50 1958.685784 1076.216521
1M 50K 1385 240.8 50 1958.685784 340.5426258
Figure: 4.27 Lagging power factor for a 200KW active power load and 800KW reactive
power load
47
Figure: 4.28 Three-phase voltages for a 200KW active power load and 800KW reactive
power load
Figure: 4.29 Three-phase currents for a 200KW active power load and 800KW reactive
power load
48
Figure: 4.30 Synchronous machine outputs for a 200KW active power load and 800KW
reactive power load
Table: 4.3 Results for different sizes Reactive Powers (Capacitive loads) used in for
simulation.
Reactive Power (-VAR)
Active Power (W)
RMS Voltage
RMS Current
Frequency (HZ)
Peak Voltage
Peak Current
50000 0 1386 12.03 50 1960.099997 17.01298916
20000 0 1386 4.814 50 1960.099997 6.808024089
100000 0 1386 24.06 50 1960.099997 34.02597831
150000 0 1386 36.18 50 1960.099997 51.16624669
200000 0 1386 48.41 50 1960.099997 68.46207855
250000 0 1386 60.48 50 1960.099997 85.53163625
500000 0 1386 120.3 50 1960.099997 170.1298916
800000 0 1386 192.4 50 1960.099997 272.0946894
1000000 0 1386 240.6 50 1960.099997 340.2597831
2000000 0 1386 481.1 50 1960.099997 680.3781449
49
Figure: 4.31 Leading power factor for a 100KW reactive power load
Figure: 4.32 Three-phase voltages for a 100KW reactive power load
50
Figure: 4.33 Three-phase currents for a 100KW reactive power load
Figure: 4.34 Synchronous machine outputs for a 100KW reactive power load
51
After testing the final model with various types and size of load I was required to verify if
the system was supplying power to the grid or extracting power from the grid. This was
done by adding an active and reactive power block to the model from the Simulink
library. Since the reactive supplied to the grid was negative it was concluded that it was
supplying power to the grid.
Figure: 4.35 Active and Reactive block Added to the Final model
52
Figure: 4.36 Active and Reactive Power Supplied to the grid after simulating a 1MW
active power load (resistive load)
Figure: 4.37 Active and Reactive Power Supplied to the grid after simulating a 200KW
active power load and a 800KW reactive power load (inductive load).
53
Figure: 4.38 Active and Reactive Power Supplied to the grid after simulating a 100KW
reactive power load (capacitive load).
4.6 Synchronous Machine Outputs
The synchronous machine outputs shown below shows the mechanical power provided
by the diesel engine, the field voltage, rotor speed and the terminal voltage of the
synchronous machine.
54
Figure: 4.39 Synchronous machine outputs
The mechanical power stabilizes near 0.285 pu however, it takes almost 1 second to the
system to stabilize. As soon as the mechanical power gets stable the whole system gets
stable. Initially the field voltage goes up to 5 pu to keep the terminal voltage at 1 pu. As
soon as the rotor speed comes to 1 pu the field voltage also comes near 1 pu. This is
evident from the formula:
TZ = [%
Where:
= #��������������������/�#�����1#�������/�8�#/���
[ = ��1=���/�8�#/���
% = ���� ���/������
TZ = ���������������� !������
55
To maintain the internal generated voltage (Vt) the flux (Vf) has to go up as the machine
starts. Once the machine is operating at its normal speed with the appropriate mechanical
power provided the field voltage comes back to 1 pu.
4.7 Loading effects on the synchronous generator
The synchronous generator behaves differently with a resistive load, inductive and a
capacitive load. With a resistive load the synchronous generator give a unity power factor
means the current and voltage are in phase. An inductive load gives a lagging effect
where the current lags the voltage by a phase angle. This is called the lagging effect.
Since a pure inductive load does not exist with every simulation a resistive load is added
with the inductive load. For a capacitive load leading power factor is shown where the
current leads the voltage by a phase angle. These components are clearly shown in the
results.
56
Discussion
Although I managed to meet my objectives of the project and do various tests on the
model there were some difficulties I faced due to lack of resources and time.
One of the common problems was to get a suitable data sheet for the synchronous
generator. The data sheet available by the manufacturers did not have all the parameters
needed for simulation. Also Matlab\Simulink does not have a standard size generator in
their Power library. So to overcome this problem I used a generator size which had been
used in a journal paper available online. The diesel engine parameters were also taken
from a journal paper.
The second problem was that the Matlab\Simulink some time did not give correct outputs
as expected. For instance, a while modeling the synchronous generator alone the
frequency supplied was 50Hz and the output was just coming out to be 0.5Hz. However
after the inclusion of the diesel engine the problem was solved and the output was 50Hz
every time. This is shown in the results in chapter 4.
Finally, various tests were done on the model and the outputs are shown in chapter 4.
These results coincide with the theory in chapter 2 and 3.
57
Conclusion
This project has been a very good practice of the studies done in the BETECH program.
It has also allowed a good experience in this field of work. The graphs achieved after the
simulation have a lot of resemblance to the theoretical aspects learnt over the years. The
synchronous machine behaves differently with different types and sizes of loads
however; it still delivers constant voltage and frequency to the grid. The outputs directly
coincide with the theory no matter what type and size of load is added to the system.
In this course I have been able to learn how to model and simulate synchronous generator
driven by a prime mover to generate electricity. This course has enabled me to broaden
my knowledge about Power generation system and has been a great means of experience
gaining. I have been able to enhance my skills and knowledge in the many ways.
I have gained a lot of experience in modeling a diesel generator set and simulating it for
stable power output. I have also learnt how to calculate values for the excitation system
of the synchronous generator and also how to control the diesel engine speed using an
automatic voltage regulator. I have also learnt how to control the speed through PID
when the load on the shaft changes to provide enough mechanical power to maintain
constant voltage and frequency of the diesel generator.
Moreover, it was a great experience of modeling and simulation with Matlab\Simulink
software. Though I had a very low knowledge of using Simulink this project has made
me understand the use Simulink in depth. I have used this software in some of my
previous units but not in detail. This project had made me understand the modeling and
simulation procedure in detail.
Finally, this course had been a very interesting experience and a chance to learn a lot
about Power generation system. The EE300 course has taught me how to manage time,
58
work under pressure and being committed to the project. It has enabled me to learn a
whole lot about diesel generator sets used in for generating electricity.
59
Future Recommendations
I would like to recommend the students who will be doing this project in future to:
• Calculate synchronous machine parameters and then model it using power system
software.
• Calculate the diesel engine parameters to connect to the synchronous generator
• Try and model synchronous generators operating in parallel connected to the grid
• Try using any other power system software to model and simulate diesel
generator set.
60
References
[1] Tylor and Francis Group, Chapter 3, Prime Movers, Synchronous Generators,
2006 LLC
[2] Sebastian Achilles and Markus Poller “Direct Drive Synchronous Machine
Models for Stability Assessment of Wind Farms” journal pp 1-9
[3] Ashwani Kumar, K. S. Sandhu, S. P. Jain, and P. Sharath Kumar “ Modeling
and Control of Micro-Turbine Based Distributed Generation System “
International journal of circuits, systems and signal processing .pp 65 – 72
[4] http://www.bwea.com/energy/how.html
[5] Tiberiu Tudorache, and Cristian Roman “ The numerical Modeling of Transient
Regimes of Diesel Generator sets” Acta Polytechnical Hungarica, Vol 7 , No. 2,
2010.
[6] Yeager, K.E., and J.R.Willis, "Modeling of Emergency Diesel Generators in an
800 Megawatt Nuclear Power Plant," IEEE Transactions on Energy
Conversion, Vol. 8, No. 3, September, 1993
[7] Matlab help file, Emergency diesel generator set. , Matlab 2007b
[8] Mohammad Tazil, Chapter 3, Synchronous generators, EE221, Department of
Engineering, University of the South Pacific
[9] Department of Engineering University of the South Pacific, EE300 Project, Designing, Development and Testing of a PIC Micro-controller based
Differential Drive Line Tracing Vehicle-2 with PID, 2010 61
[10] Mohd Dzarif Bin and Mohd Bakhari, “Speed Control Of Diesel Engine System
Through PID” TJ223.M39 2007
[11] Zheng-Ming Ge and Ching-I “Lee,Non-linear dynamics and control of chaos
for a rotational machine with a hexagonal centrifugal governor with a spring”,
Journal of Sound and Vibration 262 (2003) 845–864
[12] ] Dale Querrey, Peter Reichmeider, and Damir Novose, “Using MATLAB
Simulink for Transient Analysis in Synchronous Machines.” Auburn University,
Auburn, AL 36849 USA.
[13] Lan Gao and Hehe Fu, “The Control and Modeling of Diesel Generator Set in Electric
Propulsion Ship” international journal of Information Technology and Computer
Science, 2011, 2, 31-37, March 2011.
[14] Jun Ho Kenneth Mun , “ Implementation of Controls to a Synchronous Machine
(Simulation using MATLAB)” School of Information Technology and Electrical
Engineering, University of Queensland, 2003.
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