INTEGRATED EQUIPMENT OPERATION AND CENTRAL CONTROL
SYSTEM OF POWER PLANTS
Maunank V Patel
B.E., C.U. Shah College of Engineering & Technology, India 2006
Nilay K Desai
B.E., S.V.I.T, Gujarat University, India 2006
PROJECT
Submitted in partial satisfaction of
the requirements for the degrees of
MASTER OF SCIENCE
in
ELECTRICAL AND ELECTRONIC ENGINEERING
at
CALIFORNIA STATE UNIVERSITY, SACRAMENTO
FALL
2009
INTEGRATED EQUIPMENT OPERATION AND CENTRAL CONTROL
SYSTEM OF POWER PLANTS
A Project
by
Maunank V Patel
Nilay K Desai
Approved by:
______________________________, Committee Chair
Dr. John C. Balachandra, Ph.D.
______________________________, Second Reader
Dr. B. Preetham Kumar, Ph.D.
____________________________
Date
ii
Students: Maunank V Patel
Nilay K Desai
I certify that theses students have met the requirements for format contained in the
University format manual, and that this project is suitable for shelving in the Library and
credit is to be awarded for the project.
________________________________, Graduate Coordinator __________________
Dr. B. Preetham Kumar, Ph.D.
Date
Department of Electrical and Electronic Engineering
iii
Abstract
of
INTEGRATED EQUIPMENT OPERATION AND CENTRAL CONTROL
SYSTEM OF POWER PLANTS
by
Maunank V. Patel
Nilay K. Desai
As we know our each day to day activity requires electricity, starting from waking
up by alarm to using cell phone and computer at work till watching our daily night shows
on television, and that comes from the power generation plants, usually called power
plant. Main goal of the project is to analyze and diagnosis the main performance
parameters and optimize power plant functionality using the fault detection in
instruments and plant components, also issuing the replacement, repair or corrective
adjustments to the plant instruments. This could be done by continuously collecting data
through different parameters like voltage, part’ maximum efficiency, maximum output
etc. The outcome of this project and conclusion will be beneficial to the power plant
authorities and government authorities to prioritize and effectively maintaining the power
plant and its valuable instruments like generator.
_______________________, Committee Chair
Dr. John C. Balachandra, Ph.D.
_______________________
Date
iv
TABLE OF CONTENTS
List of Figures…………………………………………………………………...…....… vii
List of Tables……………………………………………………………………..……. viii
Chapter
1. INTRODUCTION………………………………………………..…………….......... 1
2. POWER PLANTS, GENERATOR OPERATION AND
EXPERIMENTS………...…………………………………………………...………. 3
2.1 Electric Generator Principles………………………………………………… 4
2.2 Purpose of Performing Experiments…………………………………………. 7
2.3 Load Characteristics of an Alternator………………………………...……… 8
2.4 Efficiency and Losses of an Alternator ………………………….…………. 15
3. DATA TRANSMISSION…………………………………………………..………. 21
3.1 Wired Communication……………………………………………..…….…. 22
3.2 Wireless Communication …………………………………………..………. 23
3.3 Why Satellite Communication? ……..……………………………………... 25
4. CENTRAL CONTROL SYSTEM AND CONTROL LOGIC…………………….. 28
4.1 Implementation……………………………………………....……………... 29
4.2 Finite State Machine………………………………………………………... 34
4.3 Control-IC Inputs and Outputs…………………………………………….... 35
4.4 Algorithm Structure and Operation………………………………………… 36
4.5 Code Logic………………………………………………………………..… 38
5.6 Simulation Results………………………………………..………………… 46
v
5. CONCLUSION…………..…………………………………………………………. 49
5.1 Future Expansions.……………...………………………………….……….. 49
5.2 Advantages……………………………………………………….…………. 50
5.3 Limitations……………………………………………………….…………. 50
6.
References…………….……………………………………………………………. 52
vi
LIST OF FIGURES
1. Figure 2.1: Generator Operating Principle ………………………………………...… 4
2. Figure 2.2: 3-Phase Generator Schematic ……...………….……………………….... 6
3. Figure 2.3: Circuit Diagram of the DC Motor, Alternator and RLC Load ……......… 9
4. Figure 2.4: Power Factor of Different Types of Loads (a) Lagging PF (b) Leading PF
………………………………………………………………………………………. 11
5. Figure 2.5: Resistive Load VI Characteristics …..………………..………………... 12
6. Figure 2.6: Resistive and Reactive Load VI Characteristics……..……………….... 14
7. Figure 2.7: Circuit for Measuring Rotational Losses ……………….…………..….. 16
8. Figure 2.8: Circuit for Measuring Armature Resistance…………………………..... 17
9. Figure 2.9: Circuit for Measuring Field Losses……...…………………………..…. 18
10. Figure 3.1: Classification of Communication Systems………..…………….…..….. 22
11. Figure 4.1: Block Diagram of Central Control System………...…………..………. 32
12. Figure 4.2: Finite State Machine of Central Control System………………...….….. 34
13. Figure 4.3: Block Diagram of Control-IC…………………………………..………. 36
14. Figure 4.4: Results of Repair Functionality of Control-IC………………….…….... 46
vii
LIST OF TABLES
1. Table 2.1: No Load, Full Load and Voltage Regulation Readings…………………. 10
2. Table 2.2: Rotation Losses…………………………………………………..……… 19
3. Table 2.3: Armature Resistance………………………………………………..…… 19
4. Table 2.4: Field Losses………………………………………………………..……. 19
5. Table 2.5: Core Losses………………………………………………………..…….. 19
6. Table 2.6: Total Losses………………………………………………………..……. 20
7. Table 2.7: Efficiency…………………...………………………………………...…. 20
viii
1
Chapter 1
INTRODUCTION
In this project, we have discussed one of the most important parts of power plant,
which is generator. We have concentrated on the working of generators, its different
operating parameters like nominal power output, Speed and Nominal power factor during
different loading conditions etc. and there are always chances of faults occurring in the
real time condition which affects described parameters. We have achieved different
solutions to overcome those faults by doing certain experiments on synchronous
generator. In addition to that, we have prioritized the tasks need to be performed on the
generators in different abnormal operating conditions in order to optimize generator’s
working and its efficiency. Moreover, to operate more than one power station centrally
we need effective way of communication link between the power plants and central
control station. So basically the project is divided in to three parts, which are described
below in detail. [1-17]
Chapter I of this project report focuses on the introduction and a brief overview of
project summary. Chapter II will mainly be focusing on the generator’s working and its
detailed analysis. This chapter will also include details of the experiments, followed
procedures, result data and respective calculations of the experiments performed. Chapter
III will be focusing on the different types of communication systems available, and
choosing best fit for the communication link between the power plant and control logic.
2
Chapter IV of the report explains different abnormal operating conditions of generator
and cover the algorithm designed to handle under-voltage and overvoltage situations in
detail. The last chapter V will be covering conclusion, advantages, limitations and future
expansion of the “Integrated equipment operation and central control system of power
plants”.
3
Chapter 2
POWER PLANTS, GENERATOR OPERATION AND EXPERIMENTS
Generally power plants are classified by sources of energy they use to convert it into
the electric energy. There are several types of power plants like Thermal power plant,
hydroelectric power plant, solar power plant, wind power plant and nuclear power plant
etc., but the main part of the power plant is generator. [3][18] Generator is the common
and most important part of the system which converts one form of energy in to the
electric energy with the help of other power plant specific equipments. In other language
generator converts mechanical energy to electrical energy. Generated electrical energy is
transferred via Transformer for reliable power transmission network. Following is the
classification of power plants according to the source energy they use: [3] [18] [8-11]

Fossil fuel or geothermal power plant: coal, oil or gas to heat water to operate
turbine.[3]

Nuclear power plant: nuclear reactor’s heat to operate steam turbine generator.[3]

Hydroelectric power plant: flow of water, wave or tidal motion to operate water
turbines. [3]

Solar power plant: solar energy to heat fluid (oil) which boils water into steam to
operate turbine. [3]

Wind power plant: strong, steady wind to operate wind turbines. [3]
4
2.1 Electric Generator Principles
Figure 2.1: Generator Operating Principle [19]
Faraday’s law states that when a conductor is moved perpendicular to the
magnetic field, voltage is generated in conductor. [4] Generator works on this principle.
As shown in the figure 2.1 the coil is placed in the magnetic field. When coil rotates it cut
the magnetic flux lines and that produces the current in the coil. We get the maximum
voltage, when coil is perpendicular to the magnetic flux lines. Moreover, every 180
rotation of the coil current flowing through the coil changes its direction to the opposite.
So current generated by the generator is always alternating, and this is the reason that
generator can also be called an alternator. There are two different types of arrangement in
generator: set of coils rotates within stationary magnetic field or magnetic field rotates
inside a stationary set of coils. [3-5] Main components of generator are stated bellow: [4]
5

Stator

Rotor

Core and Frame
Amount of electrical voltage generated depends on Active length of conductor (L),
Strength of magnetic field (B) and velocity of conductor (v) [3-5].
E = B x L x v………………………………………… [4] (eq. 2.1)
The magnitude of the generated voltage at the generator terminal depends on the rate
of change of flux linkage, number of coils and the flux linkage to the coil. Generated
voltage can be varied by increasing or decreasing the speed of the rotor, but ideally speed
should be constant, because we need our operating power supply frequency to be constant
at either 60Hz or 50Hz. Increasing the magnetic flux strength also increase the voltage
produced by the generator. [3-5]
6
Figure 2.2: 3-Phase Generator Schematic [6]
Let’s take an example of the small engine driven generator to understand the
operational characteristics of the generator. In this type of generator combustion engine
works as an exciter. This means mechanical energy of the combustion machine is used to
rotate the generator shaft. Now in normal no load condition combustion machine runs at a
rated speed, as soon as the load is applied to output of the generator combustion machine
speed and output voltage reduces. Now to maintain the rated speed, combustion machine
throttle needs to be changed in certain way that it increase the inlet of the fuel and
eventually overcome the load effect on generator and maintains its normal speed. Same
way when load is cutoff from the generator output, throttle needs to be adjusted so that
7
generator comes back to the normal rated speed. Hence the generator should be operated
at rated speed to generate fix frequency. [3][4]
To practically understand the effect of loading and efficiency of generator we
have performed several experiments and measured different parameters of the generator
in the Lab, which we are going to discuss in the next topic 2.2.
2.2 Purpose of Performing Experiments
We want to know the behavior of synchronous generator under different operating
conditions. For testing this condition, we will simulate an alternator in different
circumstances. We have performed two experiments to monitor the outcome of an
alternator. First one is load characteristics of an alternator and second is to find losses and
efficiency of an alternator. Using results of these experiments, we will design a central
control system which will monitor the performance of an alternator of power plants
situated at different locations. We have selected load characteristic, losses and efficiency
for specific reasons. [7]
Load characteristic experiment:
Generator reacts differently when the load connecting to the output of it is resistive,
capacitive or inductive. Hence, the power factor for each of the above explained loads are
different. The purpose of doing this experiment is to understand behavior of generator
under different loading conditions. [7]
Losses and Efficiency experiment:
8
Performance and efficiency of any electrical machine can be determined by its losses
and outputs. Thus, we are going to measure different types of losses and its effects on
generator efficiency. [7]
2.3 Load Characteristics of an Alternator
As we have seen earlier that there are three types of load i.e. resistive, inductive and
capacitive, but in real time applications generator drives combination of these three types
of load. [3-7] The reason behind this is simple, let’s take an example of home appliances.
Our home appliances are the load driven by generator and these appliances load consists
of resistors, capacitors and inductors of different types of ICs etc. So in real time
applications loads are never purely resistive or capacitive or inductive. But, here in this
experiment for the simplification we are going to apply resistive, capacitive and inductive
load separately and see the generator output voltage change during full load and no load
conditions. [3-7]
Equipments used:
DC motor, Synchronous AC generator, strobe tachometer (to measure RPM of the
rotor), connecting probes, RLC load [7]
Specification of an alternator and DC motor:
Generator Spec
Voltage:
208V
Ampere:
1.7A
Horse Power: 1/3 (0.33)
RPM:
1800
Phase:
Frequency:
3
60Hz
DC motor Specs
Voltage:
125V
9
Sh.FLD Amp: 1.7A
Horse Power: 1/3 (0.33)
RPM:
1800
Procedure Followed:
Motor
Alternator
Alternator Switch
2
Syncr.
Run
Rheostat
0- 125V
DC Supply
Shunt
Field
ARM
V
4,5,6
T1
Induc.
Start
1
Start
Switch
T2
T3
L2
L3
3
L1
Tachometer
-
0- 150V
DC Supply
+
RLC Load
Figure 2.3: Circuit Diagram of the DC Motor, Alternator and RLC Load
As shown in the figure 2.3 we connected the 150V power supply to the alternator
field, and 125V power supply to the DC excitation motor. We have coupled both motor
and alternator and clamped it securely. We have RLC resistive/reactive load that has
option of turning it into only purely resistive, capacitive or inductive load. So this RLC
resistive/reactive load is connected at alternator’s output terminal through a switch. As
per alternator’s specifications the rated RPM is 1800 to generate 60Hz frequency. [7] So
we will always try to adjust the speed of the rotor to 1800, during this experiment. First
of all we started with the resistive load. So we gave 125V supply to the DC motor and
10
150V to the alternator’s field, also connected resistive load to the alternator, using RLC
load. We want 208V at the output of an alternator so adjusted the 150V supply in such a
way that we can achieve that level. Now we need to adjust rotor speed at 1800 RPM,
which can be obtained using the field rheostat of the DC motor. [7] So as shown in the
table 2.1 full load resistive voltage is 208V. Now we are going to disconnect the RCL
resistive load from the alternator, and will again match the rated speed (1800 RPM) using
DC motor field rheostat, and take the reading of alternator output voltage, which in
resistive load case is 215V as shown in the table 2.1. We are going to follow the same
procedure for capacitive and inductive load, like connecting the load to the alternator
matching the full load output voltage to 208V and speed to 1800 RPM, and then
disconnecting the load take the no load voltage reading after matching the speed of an
alternator to 1800 RPM using the DC motor field rheostat. All the readings taken are
shown bellow in table 2.1. [3-7]
Readings and Calculations:
TYPE OF LOAD
Resistive
Capacitive
Inductive
No Load Volts
215
193
240
Full Load Volts
208
208
208
3.36%
-7.2%
15.32%
Voltage regulation
Table 2.1: No load, Full Load and Voltage Regulation Readings [7]
Here, voltage regulation is calculated by equation given bellow
11
% Voltage regulation = No load volts – Full Load Volts
Full load volts
X 100
[3][7]
% Voltage regulation for resistive load = 3.36%....................................... (eq. 2.2)
% Voltage regulation for inductive load = -7.2%...................................... (eq. 2.3)
% Voltage regulation for capacitive load = 15.32%................................... (eq. 2.4)
Understanding of an experiment:
Figure 2.4: Power Factor of Different Types of Loads (a)Lagging PF (b)Leading PF[6]
As explained earlier, the experiment was performed under three loading conditions
shown bellow.
12

Resistive load (Unity)

Capacitive load (Leading)

Inductive load (Lagging)
Here we have measured the output voltage of the generator with these three loading
conditions. In general, an alternator terminal voltage depends on the speed of the rotor
and field current of an alternator, but when the load is connected to the output terminal of
generator, resultant voltage changes. The change in output voltage is different from the
generated voltage which highly depends on the type of load connected to the armature
coil. [7] Now we are going to discuss the changes of output voltage due to resistive,
capacitive and inductive loads. [7][17]
Figure 2.5: Resistive Load VI Characteristics [17]
13
Resistive load at the output of an alternator gives IR drop, basically voltage (ΔV)
drop. As shown in the table 2.1, resistive full load voltage is 208V and no load voltage is
215V. So here we can say that 7V of voltage dropped. According to equation 2.2 we got
3.36% of voltage regulation for this resistive load. Moreover, when the generated
sinusoidal voltage and current signal passes through different kind of loads, it leads to a
change in the angle between voltage and current respectively. [17] The angle between
resultant voltage and current is called the “power angle” and the cosine of the same angle
is called “power factor” (PF). [17] Power factor always depends on the reactive
characteristics of the circuit. When pure resistance is connected to the alternator’s
armature coil, the resultant voltage is in phase with the generated current, as shown in the
figure 2.4 and figure 2.5. [3][4][17]
Inductor always opposes ac current. So when inductor is connected to the armature
coil as a load then there is a IR drop in inductor and due to the reactance of the inductor,
applied sinusoidal voltage and current changes its respective angle. In case of a pure
inductive load is 90° lagging current with respect to the resultant voltage. As shown in
table 2.1the inductive full load voltage is 208V and no load voltage is 240V. The voltage
regulation of the inductor is increased by 15.32%, as shown in equation 2.4. [3-7][17]
14
Figure 2.6: Resistive and Reactive Load VI Characteristics [17]
Capacitive load is different than the inductive load and resistive load. The capacitive
reactance tries to add the voltage to the actual applied voltage. Hence the resultant
voltage is going to be higher than the actual applied voltage. We can notice the increased
resultant voltage in the table 2.1, says no load voltage is 193V and full capacitive load
voltage is 208V. Due to the increase in the resultant voltage, the voltage regulation is –ve.
In addition to that when pure capacitive load is connected to the output terminal of an
alternator the resultant current is leading 90° with respect to the resulting voltage. [37][17]
15
By doing this experiment we came to know that most of the critical operating
condition in real time generator application occurs due to different kind of load generator
drives. These abnormal operating conditions and its details are discussed in chapter 4. It
also covers the control logic that shows how to handle different situations.
2.4 Efficiency and Losses of an Alternator
One from of energy can be converted to another form of energy, but 100%
conversion is not possible due to the losses of the energy conversion systems. [7] The
same phenomenon applies to the power generating systems like generator systems. So the
purpose of doing this experiment was to know the efficiency of a synchronous generator
and loss parameter affecting the efficiency. Efficiency of a generator is a ratio of total
power output to the sum of total losses and actual power output. [3-7] As the losses
increases the efficiency of a generator decreases, because efficiency is inversely
proportional to the losses. In generator system there are several types of losses like Field
losses, armature losses, core losses and several types of mechanical losses. Here in this
experiment we have measured all of these losses of the generator, whose specifications
are listed below. [7]
Equipments used:
DC motor, Synchronous AC generator, strobe tachometer (to measure RPM of the
rotor), connecting probes, RLC load [7]
Specification of an alternator and DC motor:
16
Generator Spec
Voltage:
208V
Ampere:
1.7A
Horse Power: 1/3 (0.33)
RPM:
1800
Phase:
3
Frequency: 60Hz
DC motor Specs
Voltage:
125V
Sh.FLD Amp: 1.7A
Horse Power: 1/3 (0.33)
RPM:
1800
Procedure Followed:
We have calculated rotational losses, armature resistance, field losses and total losses
of a synchronous generator synchronous generator system by following procedure.
Shown below is the procedure to measure these losses.
DC Motor
+
A
+
Rheostat
+
0- 125V
DC Supply
V
ARM
Shunt
Field
Start
Switch
Tachometer
Figure 2.7: Circuit for Measuring Rotational Losses
First of all we are going to calculate rotational losses of the generator system. Here
we have used the same alternator and DC motor as we have used in the previous
17
experiment (2.5). As shown in figure 2.7, we have connected the DC motor to the 125V
dc power supply. We have not coupled the dc motor to the alternator yet. We gave the
supply to dc motor and using the field rheostat we adjusted shaft speed to the 1800 RPM
(rated speed), and noted the reading of supply voltage and field current in table 2.2. Now
we are going to measure voltage and current with DC motor coupled to the alternator, but
alternator is not connected to any power supply. This is because we want to know the
rotational losses of the alternator. We followed the same procedure, connected 125V to
dc motor, and adjusted the speed of the rotor to 1800 RPM using the motor field rheostat.
We measured the input voltage and resultant current in the table 2.2. [7][17]
Field
Syncr.
Run
Induc.
Start
Armature
A
+
V
0- 150V
DC Supply
-
Figure 2.8: Circuit for Measuring Armature Resistance
Now, for the armature resistance losses we do not need to couple dc motor to the
alternator. As shown in figure 2.8, we have connected the circuit. We have connected
150V power supply to the one armature winding. We increased the supply voltage so that
18
we get 1A current. We have noted down the reading of voltage and current in table 2.3,
and calculated the armature resistance as depicted. [7]
3-phase Alternator
2
A
Syncr.
Run
V
4,5,6
T1
Induc.
Start
1
A
0- 150V
DC Supply
T3
L2
L3
3
L1
-
T2
+
RLC Load
Figure 2.9: Circuit for Measuring Field Losses
To determine the field losses, we have connected the alternator as shown in figure
2.9. In this case we have connected 150V dc power supply to the alternator as shown in
the figure 2.9. RLC load is connected to the alternator output with no resistance load, this
is just to close the circuit. We gave the 125V supply to the DC motor and adjusted the
speed to rated 1800 RPM speed. After that we have increased the 150V excitation voltage
so that output comes to 208V. At this time we noted the voltage and current
measurements of the alternator field in table 2.4. At the same time we measured motor’s
voltage and current measurements. That gave us core losses according to the table 2.5. [7]
19
Readings and calculations:
E
I
ExI
Uncoupled Motor
125V
0.76A
PML=__95V___
Coupled Motor
125V
1.02A
PMAL=__127.5V__
PAL = PMAL-PML = 127.5V – 95 = 32.5
Table 2.2: Rotation Losses [7]
I
E
RDC = E/I
RDC x 1.5
Armature Res.
0.3A
4.2V
14 Ω
21 Ω
63Ω
Table 2.3: Armature Resistance [7]
Current
Voltage
PFL = E x I
0.51A
53V
27.03
Table 2.4: Field Losses [7]
Current
Voltage
PNLL
PCL (PNLL - PMAL)
1.15A
125V
143.75
16.25
Table 2.5: Core Losses [7]
Rot. (PAL)
32.5W
Field (PFL)
27.03W
20
Core (PCL)
16.25W
(IALT)2 R (PLOAD)
3W
TOTAL
78.78W
Table 2.6: Total Losses [7]
E
I
POUT
POUT + Losses
100.84+78.78W =
201V
0.29A
100.84W
179.62
Table 2.7: Efficiency [7]
POUT = E x I x 1.73 = 100.84W……………………………………………… (eq. 2.5)
%Efficiency = Power Out / Power Out + Losses * 100……………………. (eq. 2.6)
= 100.84/ 179.62 * 100
%Efficiency = 56%.......................................................................................... (eq. 2.7)
21
Chapter 3
DATA TRANSMISSION
As we have discussed earlier in our introduction, we want to collaborate the data of
the different power plants at one central place. So that observations of power plant
equipments, its parameters, real time inputs/outputs as well as decisions on the repair,
change or maintenance of power plant’s various functional blocks could be issued
remotely. This process needs efficient data transmission link. So bellow we have
categorized and discussed the different ways of communication systems. We are going to
start with some basic fundamentals of communication systems, and then on we are going
to concentrate on the type of communication that is more advantageous for the
“Integrated Equipment Operation and Central Control System of Power Plant”. [1]
Now the common functional blocks for any communication system consist of
transmitter, channel and receiver. [1][2] Basic purpose of communication systems is to
transfer information from one end to other end respectively called as a Transmitter and
Receiver. Transmitter takes the data signals from the source and feed that data signal in to
the channel. Further on channel guides these transmitted signals to the receiver, and
receiver fetches data signal from the channel and give it to the intended target. The
information is mainly speech, data, pictures and music. [1] Here in this project the
information type will be “real time data”, which we are going to discuss in the chapter no.
4. Moreover communication systems could be mainly categorized in two parts, wired and
22
wireless or rather we can say guided propagation and free propagation, and this
differentiation is based on the channel that we are using. [1]
Types of
Communication
systems by Channel
Wired Communication
Systems
Telephone
Channels
(Twisted pair)
Coaxial Cables
Channels
Wireless Communication
Systems
Optical Fiber
Channel
Broadcast audio/
video Channel
Mobile/
Telecommunication
systems by Channel
Satellite
Communication
Channel
Figure 3.1: Classification of Communication Systems
3.1 Wired Communication
Wired communication is often called guided propagation of the signals. There are
several types of channels for wired communication, commonly includes
23

telephone channels

coaxial cables

optical fiber
Telephone channels are usually used for the speech transfer, and this communication
system uses twisted pair of copper cables. Typically the twisted pair cables have
impedance of 90 to 110ohms and can support frequencies till 3.4 kHz, so twisted pair
cables are known as “bandwidth limited channel”. [1][2][12] Coaxial cables are having
larger bandwidth than twisted pair cable channel and lower impedance around 50 to
75ohms. [1][2] This is the reason they are generally used for the Television signal
transmission which requires high bandwidth cable. Optical fiber cables are could be
called as ideal cables for wired transmission, as they have very large bandwidth, very low
losses, light weight and small in size. They can carry up to 2 X 1013 Hz frequency. [1][2]
These were the types of wired communication systems that we can use for the
transmission between different power station and the central control station. [1][2][12]
3.2 Wireless Communication
Wireless communication is generally called as a free space propagation of signals.
Usually they are categorized in

broadcast audio/video channels

mobile/Telecommunication channels

satellite communication channels
24
All of the above listed types of wireless communication systems use specific type of
modulation of the information signal, and that modulated signal is transmitted via
antenna into the free space. Antennas usually mounted on the top of the tower so that the
transmitted signal is less obstructed and could be received without losing any signal
properties by the receiver. The reason of wireless communication to be successful is that,
the signal propagates beyond the line of sight because the most of the RF signals can
propagate on the surface of earth. [1] Broadcasting of audio/video is a simplex
communication where there is only one transmitter and many receivers, used for the
AM/FM radio and Television broadcasting. Mobile/Telecommunication channel
communication system is a wireless version of the wired telephone channel. This type of
communication is full duplex, and also has one transmitter and multiple receivers, but the
signals are highly encoded and could be received by one and only one receiver. Receiver
could be handling the signals from two different transmitters. [1][2] The last type of
wireless communication system is satellite communication system, has a very large
bandwidth, which is the main advantage of it. Moreover it is highly secured
communication link, with the greater area of coverage. So, satellite communication is
going to be the best communication system for data transfer and control of different
power plants. Comparative study between satellite communication and other types of
communication, and why satellite communication is better for the specific purpose
central control system of different power plants is explained bellow. [1][2][12]
25
3.3 Why Satellite Communication?
In this section we are going to see the advantages of satellite communication over the
all other communication system discussed in the above section, and why we have decided
that satellite communication is highly compatible for central control of the several power
plant systems. [1][2]
Very low losses due to atmospheric conditions make it a reliable communication:
Compared to other types wireless communication systems satellite signals are highly
guided and unidirectional. Satellite communication uses 4Ghz/6Ghz frequencies for its
upstream and downstream communication, that’s why the attenuation and losses of
signals are very less compared to the losses due the earth surface topological features in
other types of wireless communication system. [1] Due to very negligible losses in the
information signal satellite communication is highly reliable.
Greater area of coverage: In satellite communication there are several types of
satellites. They are generally categorized from its operational orbit like geostationary,
low earth orbit, medium earth orbit etc. For our requirements here we need constant
communication between central control station and power plans 24 x 7, and that is
fulfilled by the geostationary satellite. As they maintain the relative speed to earth to
almost zero, so they are stationary earth. Moreover one geostationary satellite can cover
almost 42.4% of the earth surface. This amount of coverage is not possible using the
single antenna by any other communication system. [1][13][14]
26
Geostationary satellites always points toward the same direction on the earth: There
is no need to adjust the direction of earth based antenna, because geostationary satellites
are stationary to earth. So once the transmitter and receiver pair is aligned for the
communication, there is no need to further adjustments. [1][13][14]
Installation and implementation of new services are very fast and easy: Compared to
several types of wired communication there is no need to install extra wiring for any new
service. Even the expansion of the network to the remote areas is very difficult using the
wired network. On the other hand setting up the satellite network is very easy, fast and
inexpensive for special application. Adding new feature does not require much of the
physical implementation compares to other systems. [1][13][14]
Very high availability: This is the most important advantage of the satellite
communication system because in any natural disaster condition or in any worst possible
human being condition, information exchange is possible. [1][13][14]
Quality of service: As we discussed earlier losses are very less and availability is high
compared to any other communication method available. This automatically improves the
quality of service provide by satellite communication. [1][13][14]
27
Secured communication: Satellite communication always operates in two direction,
signals from earth to satellite is called uplink signals and signals from satellite to earth
station is called downlink signals. Uplink usually operated at 4Ghz and downlink usually
operates at 6Ghz. So it is very difficult to obstruct or interfere the satellite
communication signals, and hence considered as a highly secured communication link.
[1][13][14]
28
Chapter 4
CENTRAL CONTROL SYSTEM AND CONTROL LOGIC
This is the last part of our project, and this part is going to include the control system
that we have designed specifically for generator, but the future expansion of this control
system can handle different integrated parts of the operation power plant. The designed
control system is going to be at the central control station as we have discusses in our
earlier part of project. The main purpose of designing this automated control system is to
capture the real time data, process it and make supervisory decisions remotely. By doing
this efficiency of the power plant components could be increased with comparatively less
efforts. Here for the simplicity we are going to concentrate on the generators. We are
going to focus on generators real time data and decisions with respect to that data. [16]
In the electrical infrastructure environment the same kind of system that is been used
from quite a long time called SCADA (superiority control and data acquisition). SCADA
generally used in industrial infrastructure, power generation systems, manufacturing
systems etc. to analyze and process the real time data using the SCADA components.
SCADA system components include high end customized computer system, interface
software, remote sensors and control systems and communication system to interface
between central control system and remote units.[16] Here we are trying to achieve the
same goal as SCADA system in different way. SCADA system uses the high end
computer controlling system, but we have planned to do this by simple FPGA and
29
hardware coding. [16][15] Here we are using verilog as our hardware coding language.
FPGA stands for field programmable gate array. FPGA is a one type of integrated circuit
that could be programmed and erase many times. FPGA’s use clock and used highly in
synchronous applications. Languages like verilog or VHDL is used to program FPGAs.
Benefits of using FPGAs: [15]

Reliable: they are generally programmed to achieve some specific functionality.
[15]

Upgradable: As FPGAs could be reprogrammed many times, any system upgrade
using FPGA is very easy and cost effective. [15]
4.1 Implementation
As we have seen generators data means output parameters of generator, different
sensor data, winding currents, voltages etc. First of all we are going to concentrate on
different kinds of abnormal operating condition of a generator, they are listed below.
Under voltage:
By definition under voltage is a condition of a generator output voltage is low below
the low voltage tolerance level. This condition generally occurs due to heavy system
load. When large system load is applied to the generator exceeds the generator’s load
driving capability then output voltage goes below normal operating voltage, because the
response time of the voltage regulator circuit and/or the exciter is slower compared to the
30
time taken by the system to go in the under voltage state. Different sets of relays like time
relay, under voltage repays, heavy load relays etc. could be used to protect the generator
from this type of situation. [3][4][5]
Overvoltage:
Over voltage is a condition due to the loss of large amount of load from the generator.
When large system load losses from the generator then generators tries to rotate faster
which increases the frequency and voltage instantaneously. This is because the response
time of the voltage regulator circuit and/or the exciter is slower compared to the time
taken by the system to go in the under voltage state. The voltage regulator usually
reduces the voltage to the normal level, if that’s not possible by the voltage regulator then
issue needs to be resolved by the operator. If the overvoltage condition is caused by the
light system load and transmission line capacitance then shunt reactors could be used or
issue needs to be addressed by the operator to bring the voltage back to operational.
[3][4][5]
Loss of synchronization:
Generators usually operate the load together, it is usually called that they are working
in synchronization. During some incidents generator goes out of synchronization. The
stator and rotor pole speeds difference causes “slipping of poles”. As sleeping frequency
increases torque on the rotor shaft increases. That could result into severe damage of
generator. If generator is isolated when it’s out of synchronization and/or detection of the
31
first slip cycle, then it could be saved from being damaged. This protection could be
provided through the relays. [3][4][5]
Excessive load:
Excessive system load is caused by mismatch between the generated power and the
load. This issue could be resolved as soon as the exciter notices it. Usually the electrical
events like excessive load occur fast than the response time of the exciter system or
voltage regulator system. Excessive load condition lowers the output voltage and reduced
the output frequency of the generator. [3][4][5]
There are several other several other operating conditions like unbalanced phase
condition and synchronous resonance, but for the representation of our conceptual control
system we are going to take under-voltage condition and overvoltage condition in to the
consideration.
32
Satellite
Repeater
TX/RX Antenna
Power Plant
Va
Undervoltage
Sensor
Vb
Vc
0
UV Or
1
Central control station
TX Antenna
RX Antenna
MUX/
Transmitter
UV
Receiver
Control
IC
Va
Vb
Vc
Overvoltage
Sensor
0
OV Or
1
Figure 4.1: Block Diagram of Central Control System
As shown in the block diagram, we are having two sensors one for under-voltage and
another for overvoltage at the power plant side. They have the same inputs from the
generator as they both are voltage sensors. It is assumed that both of the sensor bocks are
combination of electronic circuitry and some repays, which together gives digital output.
Output of the under-voltage and overvoltage sensor block is named as UV (either 0 or 1)
and OV (either 0 or 1) respectively. Both of this output signals re sent to the transmitter
and via satellite link it is received by the receiver antenna. After the successful reception
OV
33
both the signals are sent to the Control-IC input. Now the Control-IC will continuously
monitor these inputs and respond to these conditions.
34
4.2 Finite State Machine
reset
onoff=0
Idle
State
onoff=0
onoff=1
Replace=0,
ov=0,uv=0
onoff=0
Replace
/ACK
Running
State
onoff=0
replace=1
uv=1
replace_ack=1
ov=0
uv=0
Change /
Replace
State
ov=1
Under
Voltage
State
Over
Voltage
State
ov=0
uv=1
uv=0
Dummy
Wait State
Dummy
Wait State
uv=1
Repair /
ACK
ov=1
ov=1
Repair
State
repair_ack=1
Figure 4.2: Finite State Machine of Central Control System
35
4.3 Control- IC Inputs and Outputs
Input Signals:

onoff : is a master switch it should always be on to operate the generator

ov_in: overvoltage signal from the sensor

uv_in: under voltage signal from the sensor

replace_in: Additional direct input from the sensor.

repair_ACK: Repair is acknowledges and/or repair is under process

replace_ACK: Replace is acknowledged and/or replace is under process
Outputs Signals:

repair: Repair output LED turns on when the FSM (final state machine) pointer
goes to the Repair state. “Repair state” is also shown in figure 4.2.

run: run signal goes “1”, when the generator is in a running condition. Running
indicator stays on during the normal generator operation.

replace_out: Replace output signal indicates that the generate needs to be replaced
due to severe conditions.
36
Indicator
ON / OFF
Running
OV_in
Indicator
UV_in
Replace_in
Control
IC
Repair
Change/
Replace
Repair_ACK
Indicator
Replace_ACK
Clock
Reset
Figure 4.3: Block Diagram of Control-IC
4.4 Algorithm structure and operation
As shown in finite state machine figure 4.2, we have implemented two abnormal
operating conditions in our control states here. They are under-voltage and overvoltage.
Now we are going to start with the flow and control logic of FSM for these two particular
37
abnormal operating conditions of generator. First of all to enter in to the FSM onoff
signal should be set to go to the next state, which is running state. And this turns the LED
indicator on. This indicator shows that the generator is running in its normal operating
condition. Now at the same time the control logic continuously monitors all other input
signals given to the system, like ov_in, uv_in, replace_in etc. As soon as any change in
input signal is noticed by control system it reacts accordingly. Now let’s see how the
system is going to react with the under-voltage signal “set”. Let’s assume that the FSM
pointer is at running state, and suddenly the under-voltage sensor detects the abnormal
condition. This causes the uv_in = 1. Now pointer goes to under-voltage state, while its
also monitoring all the input signals. Here comes the interesting part, as we have
discussed earlier regarding the loading conditions, abrupt load change causes voltage to
either go up or down with respect to nominal voltage. These types of voltage fluctuations
are frequent in power generation systems, and hence should not recognize as abnormal
under-voltage or overvoltage conditions. To avoid that we have added two different
functions to our system, time delay and critical voltage sensor in our control logic.
Critical voltage sensor: As shown in the figure 4.1 we are using two sensors for the
two abnormal operating conditions. These sensors set the output “1” when the generator
output voltage is above or below the critical voltage level. By doing this small
fluctuations in the voltage is neglected, and this avoids the control system going into the
abnormal operating condition.
38
Time delay: This function is implemented at central control station in Control-IC
logic. Assume one of the un_in or ov_in signal sets to “1”. Now as we know that change
in the generator load changes its output voltage. Generators voltage control system or any
other system takes some time to react to change in the load. So before taking some
decision we should system some amount of time so that fault decision is avoided.
So these are the two main features we considered while designing the control logic
for under-voltage and overvoltage conditions. Let’s come back to the FSM. We have left
the FSM pointer at under-voltage state. In this state pointer will wait till 3 clock cycles. If
the uv_in signal is still “1” then the control logic will issue repair indicator, otherwise the
control logic pointer will go back to the running condition (state) again. So this will
prevent the false repair indicator to set, during the normal voltage fluctuation. Now in
case the control logic pointer goes to the repair state and turns on the repair indicator
signal, then the repair must be acknowledge by someone from the power plant side, and
for that we have a input signal called repair_ACK, as described in the above section #. As
soon as our control logic receives the repair_ACK=1 it turns off the repair indicator LED
and goes back to idle state (or goes to the running state if onoff=1).
4.5 Code Logic
module
generator(onoff,ov_in,uv_in,replace_in,reset,clk,replace_out,repair,run,ov_out,uv_out,re
pair_ack, replace_ack);
input onoff,ov_in,uv_in,replace_in, repair_ack, replace_ack;
input reset,clk;
39
output replace_out,repair,run,ov_out,uv_out;
reg replace_out,repair,run,ov_out,uv_out;
reg [3:0]cs,ns;
// parameters of total eleven stages of FSM
parameter idle=4'b0000,
s1=4'b0001, //run
s2=4'b0010, //
s3=4'b0011,
s4=4'b0100,
s5=4'b0101,
s6=4'b0110,
s7=4'b0111,
s8=4'b1000,
s9=4'b1001,
s10=4'b1010,
s11=4'b1011,
s12=4'b1100,
s13=4'b1101;
//
always @ (posedge clk or posedge reset)
begin
if(reset)
cs<=idle;
else
cs<=ns;
end
//next state combinational logic
always@(onoff or replace_in or ov_in or uv_in or cs or replace_ack or repair_ack)
begin
case(cs)
idle:
begin
if (onoff==1'b1)
ns=s1;
else
ns=idle;
end
s1: //run state
begin
if (onoff==1'b0)
ns=idle;
40
else if (replace_in==1'b1)
ns=s4; // change and replace stage
else if (uv_in==1'b1)
ns=s3; // under voltage stage
else if (ov_in==1'b1)
ns=s2; // over voltage stage
else
ns=s1;
end
s2: //over voltage state
begin
if (onoff==1'b0)
ns=idle;
else if (ov_in==1'b0)
ns=s1; //run state
else
ns=s5; //dummy_ov_1
end
s3: //under voltage state
begin
if (onoff==1'b0)
ns=idle;
else if (ov_in==1'b0)
ns=s1; //run state
else
ns=s8; //dummy_uv_1
end
s4: // change and replave stage
begin
if (onoff==1'b0)
ns=idle;
else if (replace_ack == 1'b1)
ns = s13;
else if (replace_in == 1'b0)
ns=s1;
else
ns=s4;
end
s5: // dummy_ov_1
begin
if (onoff==1'b0)
ns=idle;
else if (ov_in==1'b0)
ns=s1;
41
else
ns=s6;
end
s6: // dummy_ov_2
begin
if (onoff==1'b0)
ns=idle;
else if (ov_in==1'b0)
ns=s1;
else
ns=s7;
end
s7: // dummy_ov_3
begin
if (onoff==1'b0)
ns=idle;
else if (ov_in==1'b0)
ns=s1;
else
ns=s11;
end
s8: // dummy_uv_1
begin
if(onoff==1'b0)
ns=idle;
else if (uv_in==1'b0)
ns=s1;
else
ns=s9;
end
s9: // dummy_uv_2
begin
if(onoff==1'b0)
ns=idle;
else if (uv_in==1'b0)
ns=s1;
else
ns=s10;
end
s10: // dummy_uv_3
begin
if(onoff==1'b0)
ns=idle;
else if (uv_in==1'b0)
42
ns=s1;
else
ns=s11;
end
s11: // repair state
begin
if(onoff==1'b0)
ns=idle;
else if (repair_ack == 1'b1)
ns = s12;
else
ns=s11;
end
s12: // repair acknowledge state
begin
ns = idle;
end
s13: // change and replace acknoledge
begin
ns = idle;
end
default:
ns=idle;
endcase
end
always @(cs)
begin
case(cs)
idle:
begin
replace_out=0;
repair=0;
run=0;
ov_out=0;
uv_out=0;
end
s1: //run state
begin
replace_out=0;
repair=0;
run=1'b1;
43
ov_out=0;
uv_out=0;
end
s2: //over voltage stage
begin
replace_out=0;
repair=0;
run=0;
ov_out=1;
uv_out=0;
end
s3: // under voltage stage
begin
replace_out=0;
repair=0;
run=0;
ov_out=0;
uv_out=1;
end
s4: // change and replace
begin
replace_out=1;
repair=0;
run=0;
ov_out=0;
uv_out=0;
end
s5: // change and replace
begin
replace_out=0;
repair=0;
run=0;
ov_out=1;
uv_out=0;
end
s6: // change and replace
begin
replace_out=0;
repair=0;
run=0;
ov_out=1;
uv_out=0;
end
s7: // change and replace
stage
stage
stage
stage
44
begin
replace_out=0;
repair=0;
run=0;
ov_out=1;
uv_out=0;
end
s8: // change and replace stage
begin
replace_out=0;
repair=0;
run=0;
ov_out=0;
uv_out=1;
end
s9: // change and replace stage
begin
replace_out=0;
repair=0;
run=0;
ov_out=0;
uv_out=1;
end
s10: // change and replace stage
begin
replace_out=0;
repair=0;
run=0;
ov_out=0;
uv_out=1;
end
s11: // repair state
begin
replace_out=0;
repair=1;
run=0;
ov_out=0;
uv_out=0;
end
s12: // repair ack stage
begin
replace_out=0;
repair=0;
run=0;
45
ov_out=0;
uv_out=0;
end
s13: // change and replace ACK stage
begin
replace_out=0;
repair=0;
run=0;
ov_out=0;
uv_out=0;
end
default: // Default stage
begin
replace_out=0;
repair=0;
run=0;
ov_out=0;
uv_out=0;
end
endcase
end
endmodule
46
4.6 Simulation
Figure 4.4 Results of Repair Functionality of Control-IC
Figure 4.4 shows the results of repair functionality of the Control logic. The designed
logic is simulated in ModelSim. The logic is fully functioning, and functionality check is
shown in figure 4.4. Bellow is the understanding of the simulation in detail. All the
affected input, output and control state signals for the repair case are highlighted in the
figure 4.4.
47

As shown in clock cycle 1, we have initialized the inputs and reset our logic. By
default we are keeping the onoff = 1, just for the simplicity.

Now During clock cycle 2 control-IC senses the onoff = 1 and decided that next
state (ns) is going to be running state. So, logic goes in the running state in the
clock cycle 3, turning the output ‘run’ = 1. No input output condition changes
during the clock cycle 4.

During clock cycle 5, the input ‘ov_in’ goes high and sensed by the control-IC. So
During the clock cycle 6 ‘ov_out’ goes high (= 1), which can be seen in the figure
4.4. As we have discusses earlier in topic (4.4), there is a 3 clock cycle time delay
to avoid Control-IC going into the Repair state with one the overvoltage condition
detected. We kept the ‘ov_in’ signal high for only two clock cycles, during ck 67, and forced it to 0 in ck 8. This change in ‘ov_in’ is detected by the control-IC
in ck 8 and current state (cs) goes running state in ck 9. So here we have checked
the functionality of time delay feature of control logic, which avoided false
detection of overvoltage operating condition of generator, discusses in topic (4.4).

Now here we are going to check that control logic goes into the repair state,
during true over voltage operating condition of generator. As shown in figure
‘ov_in’ goes high in ck 11, and we keep it high for the rest of the clock cycles.
Control logic detects this change in ‘ov_in’ in ck 11 and changes its current state
(cs) and ‘ov_out’ = 1 in ck 12 to over voltage state. Control logic waits for the
‘ov_in’ signal to be 0 during ck 13, 14 and 15. As the ‘ov_in’ is detected high in
48
ck 15 control logic goes into repair state in ck 16 by turning on the output ‘repair’
= 1 as shown in figure 4.4. This condition says the generator needs to be repaired.

Here we are going to check if the repair is acknowledged, than generator control
logic should go into the idle state and start running again. After ck 16 output
‘repair’ is high, so we changed the ‘repair_ack’ input signal to 1 at ck 18. Control
logic detected the repair acknowledgement in ck 18 and turned the output signal
‘repair’ to 0. This condition can also be seen in the figure 4.4.
Other different functionalities like under-voltage and change/repair condition of the
Control-IC is also verified.
49
Chapter 5
CONCLUSION
The goal behind this project was to design and outline the model to control different
power plants remotely, which is successfully achieved. Working on this project was
really good learning experience about different aspects of power plants and current
requirements for futuristic applications for me and my partner. My skills of designing,
thinking, time management and team work improved a lot by working on this project.
5.1 Future Expansions

More complex logic with every real time abnormal operating conditions can be
considered and designed.

The control logic could be verified after installing the logic in the hardware
FPGA.

All power plant components and its operating conditions can be included in the
central control logic.

More complex control logic could be easily designed using high level languages
like C, C++ or system verilog.
50
5.2 Advantages

Geographically separated power plant systems and its operating blocks (like
generator) can be monitored at one central control station.

Controlling is very easy as most of the power plants are at remote locations.

Complex controlling logic can be easily implemented on FPGAs at central control
station.

FPGA’s are fast, so can handle many more complex data structure and give
results quickly.

FPGA’s are also upgradable so new control logic features can be added very
easily.

As we have selected satellite communication as a effective communication system
between power plants and central control station, new features can be added very
easily.

The completely designed system could be very important for the rapidly
developing countries like India and china. [20]
5.3 Limitations

The central control operation model is not cost effective, as installation cost is
high. In addition to that, replacement of already established control system of
power plants is addition cost overhead.
51

Including all power plant operating blocks in same control logic can make it very
complex.
52
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