Faculty of Engineering, Electrical Engineering

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item: Thesis-Abstract
110V universal battery charging panel using pic microcontroller
Vijithananda, SK; Karunadasa, JP
Conventional power electronics and electronic control circuits have been replacing by the intervention of the microprocessors/microcontrollers in modern industrial applications. This is mainly because with their applications the whole systems becomes more and more compact while enhancing the durability. On the other even with the more robust applications hand more accurate & fine operation could achieve by using such modern programming devices. This project was origin from based on an actual requirement of designing (10v battery charging panel (to energize the batteries in spring charge type breakers)for electrical engineering division of Jaya Container Terminal(J.C.T) of Sri Lanka Ports Authority. But this technique would use to not only to charge batteries of spring charge breakers . but also batteries widely use in YHF communication hand held sets, explosive detectors, emergency lamps, etc.... Rechargeable batteries are vital to portable electronic equipment such as laptop computers and cell phones. Fast charging circuits must be carefully designed and are highly dependent on the particular battery's chemistry. The most popular types of rechargeable batteries in use today are the Sealed-Lead-Acid (SLA), Nickel-Cadmium(NiCd), Nickel-Metal-Hydride (NiMH), and Lithium-Ion (Li-Ion). Li-Ion is fast becoming the chemistry of choice for many portable applications because it offers a high capacity-tosize (weight) ratio and a low self-discharge characteristic .Depending on the battery chemistry the charging characteristics of a battery differs to each other. In this project simply what I have done is allows the particular battery to follow its charging characteristic curve when they where you could not find in conventional charging techniques. The charging process is controlled by the software program microcontroller (PIC16F876).Since the battery chemistries are different for different types of batteries, several sets of programs would have to written to the controller for each battery given by the manufacturer. There are some theoretical design calculations included for designing of power electronics modules. DCDC converter, square pulse generator, single rail power & dual rail power supplies,(etc..) Calculations have been done based on highly theoretical facts. Therefore some practical observations are tends to differ from the theoretical approach. Most of the theories studied in the power electronic lessons of my M.S post graduate were widely used in doing above mentioned designs. At the beginning the actual target was to built a battery charging panel of 110V,tut due to some limitations of purchasing of high capacity transformer which suit to this application ,the project was limited to 40V panel only. But the concept, approach & the guide line would be more or less same for the more advanced systems also.
item: Thesis-Full-text
A Conceptual design for a tower type concentrating solar power plant near Hambantota
Wijayawardhana, NABR; Wijayapala, WDAS; Fernando, DGR
In this study the basics of a central receiver type solar thermal power plant including a thermal storage are studied. Further, the technical feasibility of a central receiver type solar thermal power plant near Hambantota is investigated. The requirement of a power plant and the size of the plant are determined. The availability of solar resources in the area and the best area to locate a solar thermal power plant is also studied. The other required resources such as water, lands, proximity to transmission lines are taken into consideration. Further the impact on the environment and the possible measures to mitigate such impacts are examined. In addition, the technical features of a central receiver type power plant are studied and a conceptual design for such a power plant has been developed. In the conceptual design, the total required number of heliostats or reflectors, the heliostat field layout, the receiver size, the thermal storage size and the tower height have been determined. Finally, the economic feasibility of the plant is checked considering the available soft loan facilities which can be obtained from international development banks such as Global Environmental Facility (GEF), World Bank and Japan International Cooperation Agency (JICA). The economic benefits from the Carbon credit program have also been taken into account. Finally, it is concluded that certain cost reductions and economic conditions are required for the project to be viable
item: Thesis-Abstract
A dynamic load shedding scheme for maintaining system frequency stability with the increasing renewable energy penetration
(20) Herath BHMST; Widanagama Arachchige LN
Renewable energy power plants, especially grid connected solar and wind generation units are displacing the conventional generator stations with rotating machines with inertia. In Sri Lanka, renewable energy generation has begun to increase significantly. The total solar and wind energy penetration is 13% for 2020 and according to the least cost long term generation expansion plan 2018 – 2037 of Ceylon Electricity Board, this amount will be 47% by 2030. With the increased penetration of wind and solar energy generations units having no rotational inertia, there would be a variation in operational and dynamic characteristics in the power system. The power generation of solar power plants varies drastically with the cloud cover. The power output of solar and wind energy varies with their intermittent nature and as a result of it, the system frequency deviations become faster and risking the stability of power system as well. This study is focused on evaluating the frequency stability of Sri Lankan power system at major contingencies during the day-peak periods having maximum wind and solar generation. In Sri Lanka, static under frequency load shedding scheme is used to restore the stability of power system after major disturbances. This load shedding scheme is initiated based on the rate of change of frequency and under frequency settings, which shed pre-determined load amounts at frequency set points in six stages. This thesis analyzes the frequency response of Sri Lankan power system with the maximum wind and solar generation for year 2030 to evaluate the performance of the present load shedding scheme in maintaining system stability. A dynamic load shedding scheme can provide quick and optimal solution by using real-time data of operating conditions. Therefore, this research is proposing a new load shedding scheme based on dynamic load shedding method to improve the frequency stability of Sri Lankan power system while absorbing maximum solar and wind power into the system.
item: Thesis-Full-text
A Mechanism to reduce waste due to voltage dips in narrow fabric looms
Gamini, HKL; Karunadasa, JP
Like any other industry, apparel industry too tries to minimize their product cost by reducing production waste. Voltage fluctuations and power failures are two of the most concerning factors affecting the production. Even though these voltage fluctuations & voltage failures affect different kinds of looms at different degrees, its effect on the weaving looms which manufacture elastics is severe. As a narrow fabric elastic manufacturer it has been faced difficulties in minimizing the number of joints in the fabric (tape), which is a direct consequence of the same. There are no research papers or commercial devices found to minimize the fabric joints in case of voltage dips or short period voltage interruptions. The significance of the proposed system is its ability to sense the voltage dips/sags or interruption with the fast AC to DC converter and take decisions intelligently to suit the situation prevailed, e.g. whether to let the machine run or stop depending on the time elapsed. The brain of the controller 0" isa '--peripheral interface controller (PIC) and is programmed as assembly language. MPLAB Software compiles assembly to hex codes and the required sequence of signals is generated from PIC. This signal is sent to control unit of the loom via the DPDT relay to hold down the control. switches to perform the controller operations of the looms within a 3 second period during the short-time voltage variations such as interruptions and dips. Numerous other applications are possible with this system in other industries too. One is in the rubber extruder and another is mixing mill in manufacturing rubber tires.
item: Thesis-Abstract
A Neuro-fuzzy controller for efficient operation of water pumping system
Nishantha, MGS; Nanayakkara, DPT
The need for energy conservation is increasing the requirements for increased levels of electric motor & pump efficiencies. Controlling motor speed with load change has proven very successful in many applications such as water pumping. It is therefore important to optimize the efficiency of motor drive and pump systems if significant energy savings are to be obtained. The system gives best performance when system operates at the rated operating condition with the constant pressure head. But in actual operation the system is operating different operating point due to present system condition. (Actual system head may vary with the sump level, and the designed pump characteristics may not match with the present condition, so on). This causes to inefficient system operation.// This thesis proposes a new control scheme based on Neuro-Fuzzy concepts. The fuzzy logic concept used computes the required motor speed to meet the optimum overall efficiency of the pumping system in the presence of the variation of the output pressure, sump level and tank level. An Artificial Neural Network (ANN) used to predict the required Voltage and Frequency as the speed changes.// The network was trained on a set of data patterns generated by calculation based on the induction motor with pump equivalent circuit, using Matlab/Simulink computer piograme. A simulation result of overall efficiency and specific energy consumption has shown a very good concordance between the two methods, (with or without Neuro-Fuzzy controller).// The detail of overall energy saving while proposed Neuro-Fuzzy control shows below table. Energy savings 433,555 kWh per annum Benefit Rs. 3,077,850.00 perannuam The proposed methods can be easily implemented on pumping system equipped with pressure sensors. However, like many pumping system control techniques, the developed model is sensitive to motor and pump parameter variation due to temperature changes.// Finally, the advantages that can be gained by Neuro-Fuzzy controller with the proposed efficiency optimization algorithm are tremendous, and energy saving can be achieved with a very high percentage, specially in the field of water pumping systems.
item: Thesis-Abstract
A Novel behavior based mobile robotic platform for landmine detection
Aravinthan, A; Nanayakkara, T; De Silva, C
Humanitarian demining is an urgent and necessary activity to be carried out to resettle in places where the civilians were used to live before the war. Humanitarian mine clearance technology currently used in various parts of the world is based on the use of very basic equipment, techniques, and procedures developed in early years. Robotics has come into all aspects of life today. It has come into the industrial aspect, the biological and practical sciences aspect, everyday life, and especially in the rescue aspect. Humanitarian Demining is one of the areas where the robots can be used to reduce risk and speed up the process. Anovel behavior based mobile robotic platform for landmine detection is proposed in this thesis. A fully autonomous wheeled mobile robot called Autonomous Mine Detecting Robot(AMDR) was designed and developed for this purpose. A microcontroller based system was developed for processing sensor signals and driving actuators. Networks of microcontrollers were used to implement the whole system while reducing complexity of algorithm. Bumper switches, photoreflectors and sonar sensor were used in the robot to sense the world aud two DC motors were used for locomotion. A Subsumption based behavior based controller was implemented to enable the robot to do simple search operation to detect landmines. Six behaviors were arranged according to its priority level. Behaviors were tuned to give better performance.This thesis explains about Humanitarian Demining in the first chapter. The design of the robot and design of the proposed controller are explained in consecutive chapters. In the final chapter the results of experiments are summarized.
item: Thesis-Full-text
A Real time traffic signal control system
Jayakody, ANNK; Udawatta, L
Traffic congestion problem in Colombo city is getting worse since traditional traffic control system could not fulfill the need. Since the existing system is a fixed time fixed cycle control system, it cannot fit with dynamic traffic environment. In this research, a decentralized control strategy to control a traffic network grid is presented. Single controller is to control traffic signals of all approaches at one intersection and each approach green time is given by its separate Fuzzy Inference System. Vehicle arrival data are to be collected by lane detectors. Inductive Loop Detectors are proposed for this purpose. Herein, a methodology is developed to decide green time of each approach based on the arrival data by the Fuzzy Inference System and the Cycle time. Influence to the particular intersection is identified and is factorized as an input to the Fuzzy Inference System. Later, the green time is decided by the FIS. Results for this mechanism are shown for one intersection on a simulated environment modeled by Matlab. Calculations have been done based on the real data obtained for fifteen occasions. Results for three sets of data from both existing fixed time system and the intelligent model have been compared based on the calculations done for the total vehicle delay time, expected at the passing the particular intersection. It shows 51.6% of minimized total vehicle seconds delay by the intelligent traffic control model over the fixed time control system.
item: Thesis-Abstract
Achieving frequency stability through controlled active power injection using energy storage systems
(2021) Aluthge CD; Hemapala KTMU; Lucas JR
As solar Photovoltaic solar generation increases in the power system the conventional generators are being replaced or lose their dominance. Therefore, the resultant inertia of the system reduces. Due to this reason, in case of a large machine tripping in the system, or a line being tripped, the frequency deviation in a unit time increases compared to the fequency deviation in a system without high solar pentration. By using a fast active power injector to the system, such frequency deviation could be mitigated in a high solar power pentrated system. An energy storage system of such magnitude is not economically possible in the Sri Lankan context. During a fault in the system, Under Frequency Load Shedding (UFLS) occurs in the feeders and 33 kV feeders are diconected from the grid. A control mechanism has been developed to be used as an Uniterrupted Power Supply for the feeder. so that the feeder’s voltage and frequency are kept intact until the system is restored. By incorporating the said method, the selected feeder will not undergo any power interruptions during UFLS, as the fast active power injector which has been developed will cater to supplying the required power to the feeder. The fast active power injection method has been developed by combining both the virtual synchronous generator concept and the indirect current control pulse width modulation technique. Further, the research also addresses the selection criteria of the Battery Energy Storage System (BESS) to be implemented when developing the fast active power injector. The study has shown that a unity power factor 50 MW BESS can stop UFLS occurring in case of the tripping of a medium scale power plant or line tripping. and other common system faults. As such a BESS would not be economical, it also shows that a 13.7 MW, 3.88 MWh of BESS would be sufficient to prevent UFLS operating 90% of the time at night peak and day peak, with the UFLS operating probability during the off peak being less than 0.1%. Thus, the study has also shown that depleting the energy storage during the day to account for solar fluctuations would be to great advantage, with building up the battery energy reserves before night time.
item: Thesis-Full-text
Acoustic design optimization of close-fitting enclosure using genetic algorithm tool for diesel power generator soundproofing application
(2015-09-16) Ehelepola, I; Chandima, DP
Network providers are faced with significant challenges in delivering backhaul solutions. Given that solutions based on Time Division Multiplexing (TDM), is not providing improved efficiency at a reasonable cost. Thus the need for new backhaul solutions is becoming significant. With the full-IP evolution, all the mobile networks are migrated to full-IP, thus capabilities inherent to traditional TDM needs to be developed in these IP networks. Real-time applications have relatively tight timing requirements concerning delay and delay variations. Therefore, need efficient timing solution for those real-time applications. Synchronization is important aspect in networks and it is more critical in mobile networks. Loss of synchronization in mobile networks leads to call drops, mobile broadband data speed degrades and packet losses. Network equipment should be synchronized in frequency, time and time of day. To achieve the packet network based synchronization new strategies should be adopted. Else, traditional synchronization techniques is to be continued to synchronize networks. Specialized synchronization networks can deliver better and accurate performances, but that is with a higher cost. There are new technologies introduced to the industry for synchronization. Before migrating in to new technologies, analyzing these techniques against the service delivery requirement is a prerequisite. There is information available and accessible for the operators, in the areas related to developments of technical standardization proceedings, but there is clear lack of resources and information for practical implementations. There are gaps to be addressed while migration mobile networks into packet switching networks. Migration from circuit switching network to packet switching networks will break the synchronization chain. Most importantly, delivering the synchronization across the borders is required to interwork communication systems. Packet networks are asynchronous in nature therefore integrating time aware applications with packet network require correct timing at the interfaces to provide acceptable performance. Hence, special consideration and design is required in All-IP networks. Cost plays a major role in the adaptation of modern technologies to existing telecommunication networks. Hence backhauling need to be a highly cost effective. At present, the IP networks have proven to be the most cost effective and thus migrating mobile network to a full-IP based network with synchronization capability provides additional cost benefit for the network operators. In this research, technical standards and available synchronization methods are extensively evaluated. Moreover, network requirements, possibilities and limitations are also extensively analyzed. Logical behaviors are compared and analyzed for standardized synchronization techniques. Based on these analyses, implementation guidelines have been developed. The guidelines have been prepared within the overall technical framework published by ITU-T standards and it is hoped that they will be helpful for the mobile operators who wish to migrate from existing network to future proof capacity agile packet switching network.
item: Thesis-Full-text
Active current shaping for better utility interface
Perera, MHC; Karunadasa, JP
Increased use of nonlinear electrical loads injects harmonic currents to power systems. High levels of power system harmonics create voltage distortion and enlarge power quality problems. Harmonics result in poor power factor, lower efficiency and interference to adjacent communication systems. The harmonic currents flow into the utility supply lines produces extra losses. An active power filter uses a switching inverter to produce harmonic compensating currents. The major objective of this project was to eliminate effects of harmonics and to improve power factor of a typical nonlinear load. Attempts were made to apply active power filters for current shaping of a specific load, contrary to its common applications of applying at the point of common coupling. The National Instruments USB-6008 multifunction data acquisition (OAQ) module was used to acquire data from the sample load viz. the computer power supply. A potential divider was incorporated to the circuit to acquire voltage signal. Current signal was acquired using a series resistor. Filter current was implemented by switching an inductor using four insulated gate bipolar transistors (IGBT) arranged in H bridge configuration. The simulation circuit was implemented using M·ATLAB Simulink software tool. Inductance of the switching inductor, voltage of the step up transformer and the switching frequency of the system were obtained by simulation. Subsequently the above circuit parameters were validated for variable loads using total harmonic distortion as the discerning criterion. It was possible to reduce THO of the current wave of computer power supply from 107% to 12%. Power factor was improved from 0.66 to unity. By increasing the power factor to unity, the current flow can be reduced by approximately 34%. The observations made herein are applicable for harmonic elimination in nonlinear loads in general with necessary modifications.
item: Thesis-Full-text
Active vibration suppression with disturbance force estimation
Abeysiriwardhana, WASP; Abeykoon, AMHS
Vibration is a basic phenomenon that has attached control engineering’s attention for many decades. Vibration rejection in control systems is implemented with passive, semi active and active vibration suppression systems. These methods commonly use multiple redundant sensors. Multiple sensor usage and complex control has implemented the cost of operation and complexity. Minimal sensor usage to provide vibration suppression within the commonly used acceleration or deflection observation could be used to reduce the complexity and the cost of the system. This dissertation proposes a novel methods which uses either the acceleration or motor deflection measurement based disturbance force observe for vibration observations and to suppress the vibrations with active vibration suppression. The proposed system is capable of estimating the disturbances and compensate disturbance using the only a acceleration or suppression deflection sensory data. Proposed system still could work as a traditional vibration suppression system in case of a failure to active system. Active for to be injected is calculated based on the disturbance forces acting on the sprung mass. A novel method is proposed for spring and damper parameter measurements with electromagnetic actuators which enhance the overall system performance. A Quarter car model is used to illustrate the adaptability, robustness, and the vibration suppression capabilities of the system. Performance of the active vibration suppressor and disturbance observer is measured using system simulations and practical results. Simulation and practical system responses provide evidence of robust vibration suppression capabilities of the proposed method under different conditions.
item: Thesis-Full-text
Adaptive vision attentive robot eye for service robots in domestic environments
Madhusanka, BGDA; Jayasekara, B
Using eyes as an input modality for different control environments is a great area of interest for enhancing the bandwidth of human machine interaction and providing interaction functions when the use of hands is not possible. Interface design requirements in such implementations are quite different from conventional application areas. Both command-execution and feedback observation tasks may be performed by human eyes simultaneously. In order to control the motion of a mobile robot by operator gaze interaction, gaze contingent regions in the operator interface are used to execute robot movement commands, with different screen areas controlling specific directions. I have developed of adaptive vision attentive robot eye for a service robot. In this project a methodical approach has been followed to the design and develop an interactive robotic eye for adapting robot attention to user command request about the distance of an object based on the visual attention of the robot. In a human robot interaction, the humans may use command request, which focus or search object a feedback whether the movement is “near”, “middle”, and “far”. The actual quantitative meaning of those terms depends on spatial arrangement of the domestic environment where the attention is focused on. Therefore, spatial information of the environment is analyzed to adapt robot’s perception about the distance of an object, which is in its vision field. The process includes the mechanical and electrical designs, in the design process close attention has been paid to the human bio-mechanics to realize a design that reaches anthropomorphism to a closer degree. The proposed method is capable to mimics key visual functions of the human brain promises to robot eye maneuver quickly and safely through adaptive vision field through the domestic environments. The motion of changing adaptive vision field which used a focus or search objects in domestic environment more human-like manner using depth map analysis. Also the proposed robotic eye is designed in such a way that it can be used as a platform for facilitating further developments in integrating more interactive features to robotic eye.
item: Thesis-Abstract
An Advanced machine learning approach to estimate the state of charge of battery energy storage system for micro-grid
(2021) Jeewandara JMDS; Karunadasa JP; Hemapala KTMU
Microgrids and energy storage systems play a major role in the sustainable and clean energy sector. There are various types of energy storage systems (ESS) are available and among them, battery energy storage systems (BESS) are the most effective technology due to their high reliability, availability of different scales, less environmental impact, dynamic local voltage support, etc. Whereas it has been seen that few drawbacks when it is in operation such as load dynamics caused by renewable energy fluctuation, battery state of charge level variation, extreme heat buildup, temperature effect for the battery performance and loading imbalance, single phase generating systems, short term loading by electric vehicle charges. Therefore, to investigate such kinds of issues, battery modeling is required. This study mainly focused on battery modeling. For that, first, developed an accurate battery model based on the electrical and thermal behavior of the battery. Battery parametrization is an essential part of battery modeling to investigate the conditions of the battery under different temperatures and charge/discharge rates. In the proposed battery model, a second-order equivalent circuit model is used to identify the electrical parameters. It is the most preferred model because it accounts for the dynamics of charging or discharging currents than other available models. The thermal model is also investigated in detail by using heat generation inside the battery due to electrical loss and entropic heat. The three experiments performed on the battery cells to identify the battery parameters are constant current-constant voltage charge, constant current discharge, and pulse discharge. In each experiment, battery voltage, battery current, state of charge, battery capacity, surface temperature, and core temperature variations are analyzed and recorded while the ambient temperature is kept constant using a thermal chamber. Finally, model parameters are validated with the theoretical results. In addition to the above study, an accurate battery SOC level estimation method is developed via deep learning architectures, and the battery core temperature estimation model is developed by only using measurable parameters of the battery. Those studies can improve the accuracy of the battery parametrization procedure.
item: Thesis-Full-text
Agent based metering system for energy networks
(2015-10-30) Ranawaka, DMD; Hemapala, KTMU
Centralized automated single server based energy meter reading systems required high-end resources, at the same time it has low efficiency benefits, low reliability and real time meter data monitoring get more complex when the connected meter base is large. Therefore objective of the research is to provide a methodological approach for energy meter reading systems to apply for the Sri Lankan context using decentralized technique. Agent based solution was implemented with Multi Agent System (MAS) to address above issues and the system is characterized de-centralized nature and self configurable nature. Low cost, high reliable, high efficient meter reading system is provided by MAS based decentralized system
item: Thesis-Abstract
Alternative power supply options for safe shutdown of Lakvijaya power plant in a total blackout
(2015-02-08) Priyantha, GWV; Perera, HYR
Lakvijaya Power station with a capacity of 300MW is designed to deliver generated power to national grid initially over Veyangoda transmission lines. But there is no other auxiliary power supply from the grid. In addition to above lines, there is no other auxiliary power supply from the grid. Since commissioning of the plant, two incidents have taken place showing the inadequacy of the existing arrangement. At 12.15 hours on 7th June 2011, the Plant had been in operation at 260MW & 181MVar and Veyangoda line 1 and 2 tripped from Veyangoda end which resulted in an Island wide blackout. Lakvijaya machine tripped without stabilizing at the house load. Consequently the plant was without an electricity supply. At the same time Standby diesel generator of 800 kVA failed to start. Further, Plant DC supply failed causing an unsafe shutdown resulting damages and lifetime reductions to the plant and its subsystems such as rupturing of the diaphragm in LP turbine, drop in drum water level below tripping limit, rising condenser hot well level closer to the tripping limit, rising condenser vacuum pressure up to tripping limit, rising condenser steam temperature to a level which effect to condenser tubes and damaging of bearing due to pressure dropped in jacking oil pressure etc. A similar failure took place on 08th August 2012. This study is carried out to investigate the different options available to improve power supply situation eliminating such incidents in future. Initially all subsystems of the plant had been thoroughly analyzed and identified all possible bad consequences on the subsystems due to improper shutdown. A time analysis was done to find out the time taken by each subsystem to reach its tripping limits or withstanding time of subsystem before component failure during such an improper shutdown process. After collecting data from the site, detailed power system analysis including load flow studies were conducted using the ‘Power World Simulator’ software package considering possible unit auxiliary standby power supply options available during blackout condition. In that analysis below mentioned seven possible options were identified and studied. i) from Kothmale power plant, ii) from Kelanitissa Fiat gas turbine power plant, iii) from Kelanitissa combine cycle power plant, iv) from Kerawalapitiya combine cycle power plant, v) from Heladanavi diesel plant at Puttalam through 220kV line , vi) from Heladanavi diesel plant at Puttalam through 33kV line, vii) from 6×2.5MW diesel plants at Lakvijaya power station . Finally it was identified and concluded that 6 of 2.5MW standby synchronized diesel generators with 15sec restoration time should be installed.
item: Thesis-Full-text
Alum and lime dosing controllers for water treatment plant
Hettiarachchi, LP; Dasanayake, P
Many techniques are applied to the control of Alum and Lime commonly termed as coagulant dosing in a drinking water treatment plant. Coagulant dosing rate is non linear con-elated to raw water parameters such as turbidity, conductivity, pH, temperature, etc. Manual method called Jar testing is used to decide the Alum and Lime dosage. However in practical situation, Jar testing is carried out maximum three times per day. But the parameters of water sources are continuously changing specially on rainy days. Therefore overdosing and underdosing of Alum and Lime are normally occurred. Excessive coagulant overdosing leads to increase treatment costs and human health problems, while underdosing leads to failure to meet the water quality targets and less efficient operation of the water treatment plant. It means that important requirement arises to automate the system with optimum coagulant dosage. The research is aimed to propose an alternative to the jar test allowing for an on line determination of optimal coagulant dosage from raw water characteristics and design a system for feeding Alum and Lime automatically with a monitoring display. The reasonable assumption made by this research is, except turbidity and pH value, other parameters are almost same throughout year. After analyzing thousand number of jar test results with corresponding turbidity values and pH value of incoming water, it was found turbidity value of raw water and the dosage of Alum has a relationship and pH value of raw water and the dosage of Lime has another relationship. Relationship of turbidity value of raw water and the dosage of Alum is second order polynomial. However pH value of raw water and the dosage of Lime have stepwise relationship. And also actual values of three hundred situations were taken and applied to check the validity of relationships and it is proved that the relationships which has obtained are well suited to develop the automation system. Next objective is designing of hardware and software part of controller of an automotive system to dose Alum and Lime using the relationship. PIC 16F876 microcontroller is selected as the controller; it made the task easier. Since PIC 16F876 has 8-bit with analogue to digital converters, it handled analogue output of turbidity sensor and pH sensor. In this project MAX_7219 display driver IC could be easily interfaced with microcontroller by using three wires (SDO, SDI and SCLK) and LOAD (CE) which is common today named as Serial Peripheral Interface (SPI).The PIC16F876 chip is in electrical erasable packaged version (FLASH), and it helped for programming several times for testing our object before implementing. Finally complete control and feeding system for Alum and Lime was designed. Value of turbidity was measured by a turbidity sensor. That value was taken to the microcontroller that decides the Alum dosage and changes the valve position using stepper motor accordingly. Either increment or decrement of the value of turbidity by 10 makes the changing of valve position in ADC. Either increment or decrement of the value of pH value by 0.1 makes the changing of valve position in LDC. Using MAX7219 IC current value of turbidity and current value of pH are displayed in ADC and LDC respectively. Key features of the system are simple relationships constructed to find optimum coagulant dosage and ability of handling practical situations of water treatment plants using automation system with microcontrollers.
item: Thesis-Full-text
An AC drive system to replace an existing DC drive system
Muhandiram, RRN; Karunadasa, JP
DC commutator motor is the oldest motor but still the best performance motor. It has control simplicity and control accuracy although commutator motor has some inherent drawbacks due to its mechanical commutator. Normally, the older the motor, the higher the effects of some drawbacks. This dissertation is based on "Replacing an old DC drive system with a new AC drive system" in order to eliminate prevailing practical problems arisen due to aging of the drive system. The DC drive system being less reliable, that results high down time of the relevant machine effecting loss in production. . Briefing on new AC drive system, other than the existing control functions, some functional improvements are also adopted assuring far better running performance of the machine than present. Minimum maintenance, quick failure restore, minimizing down time and hence improved reliability are the key motivations of the project. It is considered the maximum running speed of the machine for capacity selection of the motor and the AC drive. The required modifications in power and control wiring are introduced keeping operational part of the machine in such a way that, machine operator does not feel any difference while in operation. Same switches, selectors, pushbuttons are utilized as in the existing system. Economic consideration of the proposed system against the existing system is discussed followed by the design. Improved power factor, reduced total harmonic distortion, improved efficiency and enhanced reliability of the machine contributes positive impact on the proposed system. It is important to say that, this is much oriented at reliability improvement of the particular machine than the other sayings.
item: Thesis-Abstract
Analysing of power quality problems of wind power generators
Chandranath, MLAA; Nanayakkara, DPN
Wind power as a rule does not contribute to voltage in grids. Also, wind power very often is a source of voltage fluctuations and flicker. Furthermore, care must be taken to upkeep availability of networks more or less dependent on wind power by preventing the voltage from collapsing in conjunction with faults occurring in the grid. The first wind power plant installed at Hambantota III Sri Lanka, 3MW was commissioned in early 1999. Alternating current transmission will turn out to be an economically and technically attractive option in many cases, and dynamic reactive power compensation will then be a natural part of the scheme. The dominating kind of wind power generators are asynchronous, this since they are robust and cost effective. Induction generators, however, do not contribute regulation of grid voltage nor frequency, and they are substantial absorbers of reactive power. Ideally, they need to be connected to very stiff grids in order not to influence power quality is a detrimental way. This is not the case in reality. Quite 0 n the contrary, wind power is usually connected for out in the grid, on sub transmission or distribution levels. The majority cases are 10-40kV. The objective of the research is to analyze the problem of voltage and current harmonics, transient behavior, power fluctuation and reactive power consumption of wind power generators and modeling of wind turbines connected to the medium voltage distribution line of the grid wher~ the other consumers are connected. Often, Voltage regulation problems arise as a consequence of grids being made dependent on wind power, a matter of growing concern as wind power gets more important in the power balance. To certain degree, Voltage Control problems cased by defect of reactive power in the grid can be, and is remedied by installation of fixed or mechanically switched shunt capacitors. This will 'not help on voltage fluctuations, however caused by varying output of wind generators. Regular voltage flicker is part of the picture, as well, caused by such phenomena as turbulent wind impact and so-called tower shadow effects.
item: Thesis-Abstract
Analysing of voltage surges in grid substation auxiliary supply
Hemaratne, JDKG; Karunadasa, JP; Jayawickrama, YRL
In Sri Lankan National Electricity Grid, severe voltage fluctuations have been noticed in the Grid Substation auxiliary supply. The auxiliary supply is quantitatively 20CkVA, but very important to keep in good health because it provides power to all substation equipment installed in GSSs, such as battery charger units and power supply modules for various types of protective monitoring and measuring instruments. Due to these fluctuations, not only the protective equipment, but also the small power equipment such as computers, Air conditioners and substation lights are also had frequent failures. It is observed all these failures to the equipment and substation lights have been experiencedjust after the tr pping of feeders due to an earth fault.// The objective of the research is to analyze the problem of voltage fluctuations in the auxiliary supply in Grid Substations and find the possible remedies. The studies presented in this report are mainly focused on the Earthing Transformer, which provides the power to the Auxiliary equipments. The earthing transformers in bulk of the GSSs are a Zig-Zag wound transformer with an low voltage auxiliary winding.// Unfortunately, there are no models for Zig-Zag transformer readily available for simulation of the problem using computer software. Therefore the purpose of simulation of the problem in this report is mainly based on a Prototype transformer, which was wound specifically for the purpose.// The possible cause to the voltage surges experienced in the auxiliary supply at an earth fault is due to the extra flux in the grounding transformer limbs and the leakage flux of primary windings directly influencing the auxiliary winding, resulting an extra voltage induced in the auxiliary winding. The arrangement of the winding in each limb has made a huge impact on the problem.// The integration of two functions has created a negative impact on the performance of the transformer. As a solution, firstly, this report suggest to split the two functions integrated in the grounding transformer i e use separate transformer for grounding the 33kV side of the GSS and an other separate transformer for auxiliary and control supply for the GSS. Secondly, re-arrange the windings in such a way that the no resultant flux induces due to the fault current injected into the neutral of the grounding transformer
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Analysing the maximum wind power penetration level around Kalpitiya Peninsula
Kothalawala, TR; Karunadasa, JP
The Government of Sri Lanka has declared the importance of developing renevvable energy in line with the national policy of maximizing indigenous sources and ensuring fuel diversity. Sri Lanka has exploited hydropower resources to almost its maximum economical potential. Only a limited number of small and medium scale hydropower plants are yet to be developed. and these are already in various stages of development. Therefore. the country is now clearly at a cross road as far as future generation IS concerned. Wind is one of the promising renewable energy options available for grid connected power. In addition, wind-mapping results for Sri Lanka shows a very good wind potential in Kalpitiya area. This research covers the impact of wind integrations on the power system of Sri Lanka and analyzes the maximum wind penetration levels around Kalpitiya peninsula for theproposed years 20 I 0. 2012. 2014 and 20 I 6 transmission networks. A steady state system analysis as well as a frequency and voltage stability analysis are used appropriately to figure out the wind penetration limits. Finally. a transient stability analysis is performed to confirm the stable operation of the wind integrated power systems. The widely known power system simulation software package PSS' E is used to model wind turbines and perform steady state and stability analyses. This research project concludes that 20MW: 70MW. 185MW and 220MW wind absorptions are feasible respectively in the years 20 I 0, 2012, 2014 and 2016 at Puttlam GS/PS. Approximately 30% wind availability is considered for the steady state system analysis. In addition, 5% spinning reserve response on droop is assumed for year 20 I 0 and 2012 and I 0% spinning reserve response on droop is assumed for year 2012 and 2014. Analyzing the most economical wind penetration limit with net work modifications is beyond the scope of this research and is open for further research study.