Master of Science in Electrical Engineering

Permanent URI for this collectionhttp://192.248.9.226/handle/123/55

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item: Thesis-Abstract
An Optimal power flow algorithm to reduce power loss by placement of DG in distribution system
(2022) Lakmali RMT; Hemapala KTMU
Distributed generation is a small-scale and renewable-based energy source (ex: solar/ wind/ biomass) near to loads in distribution networks. It is becoming more prominent in the present world due to incremental demands for electricity. The integration of DGs in the distribution system issprofitable, loss reduction and voltage-profile improvement if it is optimally sized and optimally placed. Research work included in this thesis focuses on using aneoptimization methodology for identifying the most appropriate locationaand size ofaDG. Initially, detailed study of optimal DG planning was carried regarding objective functions, constraints, load and design variables, and mathematical approaches. In this dissertation, a novel combined methodology for optimal DG planning is presented by Newton Raphson’s (NR) power-flow solution andeoptimization algorithm named ParticleeSwarm Optimization(PSO). A multi-objective function has been modified by considering real and reactive power loss minimization and cost minimization to attainethe optimal size and optimal location of DGs. Moreover, voltage-profile improvement and power systemestability improvements are obtained. The performance of theeproposed methodology is testedron the IEEE-30 busesystem and program is developed and simulated from MATLAB software. Two types of DGs are evaluated using the proposed model which is called a single DG source delivering only realpower and a single DG source delivering both realeand reactiveapower. The methoddis executed on the same 30-test bus systemefor different weighting factors. Resultsain theatest bus systemashow the effectiveness of the developed mathematical model with higher power loss reduction and cost reduction percentages. Furthermore, the proposed methodology is applied to select two distribution feeders in Sri Lanka with time-varying loads to allocate solar PV and biomass as DGs. In order to have a techno-economic solution for optimal size of DG and best location, the proposed algorithm can be used on any MV distribution feeder providing relevant line and load details.
item: Thesis-Abstract
Modelling of magnetic hysteresis of a three phase transformer under dynamic conditions
(2022) Gunasinghe MPDN; Karunadasa JP
Abstract The phenomenon of magnetic hysteresis effect of the core material of a transformer plays an important role when representing the transformer in a simulated environment. Input-output behavior of a transformer is critically correlated with the magnetic properties of the core material which is influenced by the magnetic hysteresis effect. To analyze the magnetizing characteristics of the core material of a transformer, it is required to develop a mathematical model for simulating the hysteresis phenomenon. As the outcome of this research, reliable representation of magnetizing characteristics of a three-phase transformer core, without considering any core material related parameters, a test based mathematical model is simulated. Mathematical model, which capable of producing magnetic characteristics for any given voltage level is designed by conducting two tests separately for a single phase transformer and three limbs of a three phase transformer. In the scope of this research, magnetizing characteristic model is developed using Matlab Simulink. Test data required to develop the proposed model is obtained using single phase and three transformer. Results obtained from the developed model is validated with the practically obtained outputs. Practical tests executed on transformer show close connectivity with simulated results evidencing the extensiveness of the designed model.
item: Thesis-Abstract
A Measurement - based procedure for dynamic data identification of synchronous generators
(2022) Priyadarshana KWK; Wijayapala WDAS; Prasad WD
Identification of synchronous generator parameters is a vast area in research topics. In order to model an existing power system network, these parameters are very crucial in identifying the behavior of the system during steady state or dynamic state conditions. When considering the Sri Lankan grid network there exists number of power plant which does not have some design parameters of the synchronous generators and for the older machines the existing value of the parameters might be differ from the design value due to several reasons. This thesis report is based on the identification of synchronous generator parameters using on line measurement data while giving small step response of around 2%-5% to AVR voltage reference set point. The proposed testing procedure does not create any stress to the machine and can be conducted several times without any special preparation or machine outage. The proposed methodology to identify the synchronous generator dynamic parameters is developed using the 3rd order SG model defined in the IEEE Standards. Two new system functions have derived to estimate the generator parameter which shows the relationship between the steady state and dynamic state parameters in d-q-0 domain and time domain. The Levenberg Marquart method is used as the Nonlinear least square algorithm to extract the parameters from the measured data. Proposed methodology has applied in MATLAB SIMULINK Simulation environment and in the real environment which test conducted at Kelanitissa Combined Cycle Power Plant, Sri Lanka. The Proposed method results have validated over the results with conventional test results conducted based IEEE Standards on two power plants in Sri Lanka and from the literature of similar tests. The results of the proposed method have showed good accuracy over the design values and the standard method results. It has showed that the output of the synchronous generator, using the estimated parameters is having a very closer behavior to same with the actual generator parameters. Therefore, this method can use to estimate synchronous generator parameters where the parameters are completely unknown or the machine is too old which may need to identify the existing parameter values. This study further discusses the reasons for any difference between the design parameter value and the estimated parameter value comparing with the standard IEEE based test results. This research concludes that the results of the estimated dynamic parameters obtained by the proposed method can be recommended in applying for modelling of the synchronous generators and power systems networks which will give a very close response to the actual response. Keyword: Parameter estimation, synchronous generators, Levenberg Marquart Method, Online Measurements, Small Disturbance.
item: Thesis-Abstract
Stability analysis of an islanded microgrid with ring and radial distribution
(2022) Herath HDBP; Arachchige LNW
Colombo being the commercial hub of Sri Lanka, maintaining high reliability of electricity supply is critical. Thus, the electricity distribution network of Colombo city comprises of six, 11 kV ring networks formed around five grid substations and five primary substations. However, the network is currently operated in open-ring topology. In the present operation, under maintenance periods, at times of load shedding and “selfgeneration” schemes, diesel generators are connected to the network. The generators, which are connected under the self-generation schemes are synchronized with the network. The generators, which are connected during maintenance and times of load shedding, are not synchronized. Hence, it is required to split the satellite belts into several sub sections to match the capacity of the generator to the load, so that the generator would not be tripped due to over loading. With the government policies to encourage renewable generation, solar PV generation has also been increasingly connected to the distribution network, which are not dispatched. With increasing penetration of solar PV, proper planning is required to maintain system stability and reliability under grid failures. The substations in Colombo city do not follow the conventional diurnal load pattern of Sri Lanka; instead, during day time, the load reaches a peak and during night time it drops. This load pattern follows a curve similar to the diurnal generation curve of solar PV. Thus, by introducing solar PV to such substations, the installed diesel generation capacity can be reduced and the rings can be operated as microgrids when the grid fails. In this research a case study is carried for the ring network based on primary substation-B of the Colombo city network with the distributed generation of solar PV and diesel generators to evaluate the ability of forming ring-connected microgrids for a commercial city with peak, day-time loading. The ring is split into smaller rings to form microgrids with capacity below 10 MVA. The satellites are considered as open looped. Loads of the satellite loop and the generation (solar PV/ diesel generators) are lumped to the respective radial/ ring substation. The results indicate that when the network has three, 2 MVA generators fixed to the highest loaded substations, the system is stable and when the network has 1 MVA generators fixed to all the substations, the system becomes unstable at N-1 emergency operation. Instability occurs due to small perturbations to diesel generators at some substations. Research reveals that with increasing penetration of solar PV, the system can be planned to be operated in ring-connected microgrids in stable operation to maintain the system reliability under grid failures
item: Thesis-Abstract
Performance evaluation of a generalized multilevel inverter with different operating modes
(2022) Sampath VKR; Karunadasa JP
Multilevel inverters are found in many applications in high power levels. These converters are available in different topological options, such as Cascaded Half Bridge, Neutral Point Clamp, Flying Capacitor, Hybrid and so on. By selecting appropriate switching sub-circuit, generalized multilevel inverter can be used to derive all common topologies. A Generalized 9 Level Inverter is developed and controlled to operate in Cascaded Half Bridge, Neutral Point Clamped and Flying Capacitor modes for operation in 3, 5, 7 and 9 levels with square-wave and Pulse Width Modulation control. Relative performances were investigated in terms of Total Harmonic Distortion and efficiency.
item: Thesis-Abstract
Technical analysis of employing on-site hydrogen production and storage systems with renewable energy for Telecom sites in Sri Lanka
(2022) Dilrukshi LW; Hemapala KTMU
Despite the fact that its technologies have grown at breakneck speed, energy is the lifeblood of the telecommunications industry. The concern is not only about how energy is delivered, but also about supply continuity and cost, all of which are key problems in the industry. The telecommunications industry has begun to seek for renewable energy alternatives due to the rising cost of fossil fuels and the reliance on fossil fuels for commercial electricity. To overcome the inherent restrictions of renewable energy and maintain an uninterruptible power supply, the hydrogen storage idea was added into the renewable energy conversion system. A fuel cell-based power system is explicitly modeled and studied in this study under different types of operating situations. The voltage output, current output, H 2 production, feed of air and fuel, pressure regulations, and flow rates must all be controlled in order to be technically feasible. The proposed methodology is valid for a PEMFC (Proton Exchange Membrane Fuel Cell) based power system, and the results are verified using the MATLAB Simulink tool.
item: Thesis-Abstract
Financial implications of solar penetration for electricity generation in Sri Lanka
(2022) Kodikara JJ; Wijayapala WDAS
It is important to have an uninterrupted, economical, and reliable electricity supply contributing to economic and social development of a country. Due to the environmental impacts of fossil fuel based conventional power generation, the world is moving towards power generation from renewable sources like wind, solar, biomass etc. Solar is one of the fast growing and economical renewable power generation source. The intention of development of solar power generation is to promote clean energy while addressing the basic requirement of uninterrupted and reliable electricity supply. Going with world trend, the Government of Sri Lanka promotes the development of solar PV based electricity through subsidies. Hence, the market graduated with many consumers willing to install solar rooftop and they were ably supported by solar power service providers. On the other hand, the utility is obliged to absorb the solar power generated as per the different subsidized schemes available. The benefit for the utility is that the expensive oil-fired generation during the daytime can be avoided, however in contrast, the utility needs to maintain sufficient capacity to compensate the intermittent and non-dispatchable electricity generation. Extensive research had been carried out on technical challenges and opportunities due to the technical constraints of solar power generation. However, only a limited number of studies have been carried out examining the financial and economic impact of solar penetration to the national grid of Sri Lanka. One-year historical system dispatch data for year 2019 and rooftop solar generation data for a period of 6 months of year 2019 considered for the analysis. The model compares the financials of two scenarios to estimate the impact to the utility. The base case scenario, which is business as usual with the already installed solar generation in the system. No solar scenario, which assume there is no solar in the system and therefore the demand is met by other available generation capacities in the system. This research examines the two scenarios with careful calculations of how the system can still run without solar in the system. Daily demand patterns were analyzed and then expanded to months and summarized for the year. This research focuses the financial impact of solar electricity penetration to the national grid and how everyone can still be beneficial.
item: Thesis-Abstract
Cost implications of rooftop solar PV with batteries on industrial and commercial customers in Sri Lanka
(2022) Herath SV; Lucas JR
Electricity is one of the key factors for the business of industrial and commercial customers in a particular location. Therefore, the Government and local authorities have introduced special tariff schemes to provide electricity in a cost-effective manner. On the other hand, the tariff structures are focused to reduce the stress for the grid operation by the utility provider. With the advantage of being a tropical country, Sri Lanka is having higher solar irradiation throughout the year and most of the electricity consumers are willing to install rooftop solar systems into their facility. The excess solar production can be sold back to the utility provider by several methods, as preferred by the consumer. However, the utility provider is facing many difficulties related to the technical and financial perspective, to absorb the total solar production by the consumers. Therefore, in this research, the management of the own solar production by the consumer, either grid connected or in islanded operation mode, has been speculated. The research is primarily focused on real-time based management of solar generation which is allocated for loads, charging, controllable load dispatching, and shedding is decided. Finally, the load is matched with the available power sources in the basis of optimum cost. As the optimization technique, quadrature optimization has been used. A selected industrial purpose customer and a general-purpose customer were used to analyze the data. Calculation of the unit costs for the solar energy and battery bank was done based on the LCOE formula and this represents the lifecycle cost of the energy sources based on the lifetime energy generation. The program is used to calculate the optimum battery capacity for an industrial and a general-purpose customer in Sri Lanka with the financial values in 2018 as indicated in annex 7. Also, in both cases the effect of the solar energy generation was varied to identify the change of the profit of the installations. It could be observed that when reducing the daily solar power generation, profit was drastically reduced. As an example, in relation to the data for Case B and Case E when solar generation was reduced by 17% profit was reduced by 24% for GP customer. Furthermore, the calculations were made to identify the profit changes for BST which represent the actual cost for the utility in 2018. In this case the average profit for each case was reduced by 150% ending with a loss for the investment. Also, the calculation was done for the new financial figures in 2022 November and the profits were reduced by 330% and the investment is found to be not feasible with the available figures. n conclusion, the method proposed is feasible to use to evaluate the initial investment for solar PV systems and battery energy storage (BES) systems. However, the tariff rates as well as the financial figures like fuel cost, exchange rate formulate a considerable impact on the result. Therefore, the financial figures provided in 2018 provides a profit generation but in 2022 the optimized solutions are not feasible due to changes of the financial figures. However, the method provided in this thesis can be used to calculate feasibility of solar and battery installation for any customer.
item: Thesis-Abstract
A Generalized procedure to develop transfer function based models of electrical power systems
(2022) De Silva SLD; Prasad WD
More and more renewable electricity generating sources such as wind and solar power plants are being integrated into electrical power systems, which in turn complicates processes such as power system stability studies due to the complex nature of controls in these power plants. Since most such studies are done using simulations, it is necessary to have accurate dynamic models of those power plants which describe the behaviour of the power plant during a disturbance to the network or to an internal control or the power plant. Nevertheless, it might be difficult to obtain these detailed models from manufacturers due to proprietary concerns and even if the detailed model is available, modelling complicated power electronic components in the simulation environment might be a difficult without knowing how each component operates. Moreover, when parameters change over time, physical parameters of these models need to be updated and it cannot be done without standard practical measurements. These standard tests require the generating sources to be taken out of the system for testing purposes. Therefore, instead of a detailed model, a dynamic equivalent model could be used for achieving the same requirement. This research presents a generalized procedure that can be used to accurately estimate black-box dynamic equivalent models of synchronous generators, wind and solar power plants by utilizing measurements and estimating parameters of the dynamic equivalent model. Simulations have been conducted to estimate and verify the accuracy of the proposed methodology by comparing the accuracy of the actual model and the estimated models.
item: Thesis-Abstract
Incorporation of off - shore wind power as the next step of non - conventional renewable energy in Sri Lanka
(2022) Prabhath NHM; Rodrigo A
With the current increasing trend for the non-conventional renewable energy (NCRE) in Sri Lanka, interest has been focused on retiring of thermal/coal power plants and getting the energy via renewable sources. Since almost all the water sources have been used, the available options will be wind, solar, biomass etc. From them, wind energy is more promising as it is having less intermittency and more efficiency compared to other sources. Offshore winds are more consistent than on shore winds as well as they are higher in speeds. Considering the Sri Lankan Sea territory massive energy can be harvested via offshore wind power with no or minimum affections to peoples’ lifestyle, existing inland natural beauty, relocation of people etc. compared to the onshore wind power. With being no/extremely little amount of effort required to relocate people and taking over lands, offshore wind power can be quickly implemented. However, development of offshore wind farms around Sri Lanka should be carefully and seriously studied as it can also have negative impacts on some areas. It includes marine mammals & fish, coral reefs, migratory pathways of birds, fishing industry, tourism industry etc. In this research a method is developed to locate suitable sites around a country for offshore wind power considering its technical, environmental, regulatory constraints. The method mentioned in this research is universal and validated on Sri Lanka. Initially the intended area of research (part of the Country’s Sea territory) was divided into equal areas. Then for each area the technical, environmental and regulatory constraints were analyzed using digitized maps. Creation of digitized maps using GIS software is also a part of this research. Then weightage factors are developed for each constraints using a model developed in this research and a total value for each area is calculated. Then the intended area of study is linked with the values table for that particular study area using a GIS software to visualize the suitable sites.
item: Thesis-Abstract
Estimation of actual earth resistance of a complex earthing network using soil layer modelling in the finite element domain
(2021) Liyanage WLDC; Rodrigo AS
Telecom infrastructure growth rate has been rapidly increased due to higher competition among operators for them to provide reliable and quality service to the customers. Rapid increase of telecom tower construction and usage of advanced equipment has been taken in place due to the recent development in telecom sector in Sri Lanka as well. The tower being a tall structure in the environment, act as a direct path for lightning to be grounded. Though it will protect low height buildings and people in the vicinity from direct lightning strikes, having a proper earthing system with low earth resistance is a must to avoid possible hazards by ground potential rise. Given the smaller area of the tower premises proper earthing network should be incorporated to maintain the lower earth resistance at the tower. Operators have to maintain the earth resistance at tower sites as per the TRCSL guideline for antenna structures which is below 5 ohms [1] To meet the TRCSL guidelines operators have incorporated complex earthing systems in tower sites. Typically, the tower earthing system includes copper tapes and multiple number of rods which have made a complex earth network to achieve the lowest possible earth resistance. Measuring earth resistance is quite hard in a complex earthing network due to parallel conductors, intersections and subjected to many assumptions including specially the homogeneity around all directions. Site measurement is the key parameter of reflecting the earth networks effectiveness to surges and lightnings. This thesis discusses specifically the reasons for deviations in measured and theorical values. Simulated earth networks thorough ANSYS Maxwell in the finite element domain to achieve earth resistance profile has been elaborated. Site earth resistance measurements has been taken along different directions. compared with the measurements in every direction of the sites. Validation has been done by the comparison between simulation and measurement. Analysis has done for different types of soil conditions and limitations for study has been discussed. Thesis concludes with the mechanism to estimate the accurate earth resistance of a site for a particular accuracy which also includes the general assumptions.
item: Thesis-Abstract
Design and implementation of an electronic fan regulator for reduced harmonics and ripple free speed
(2021) Kiriella KKCS; Karunadasa J P; Rodrigo WDAS
A ceiling fan regulator is needed to control the speed of a ceiling fan. With the development of power electronic switching devices, electronic (triac based) fan regulator has been introduced to the market by ceiling fan manufacturers. Compared to old fan controlling methods like inductive and resistive fan controller, this method offers advantages like low power dissipation, compactness, step-less control etc. Since this electronic fan regulator controls the effective voltage to the ceiling fan by chopping the waveform, it generates current and voltage harmonics. Speed ripples, low power factor issues, humming noises, mechanical oscillations, additional heating of the ceiling fan can be observed because of these low quality waveforms. This research investigated a suitable power electronic based fan regulator for reduced harmonics and ripple free speed. The study was carried out by choosing 6 different power electronic based single phase motor controlling methods and examining their technical aspects and market competitiveness as a ceiling fan regulator. Out of these 6 methods, DC chopper fed controller showed comparatively a best possible solution for above mentioned problems. Moreover, the simulation results were validated by implementing a prototype of a DC chopper fed controller. Unlike traditional electronic fan regulator, proposed method feeds the current continuously to the load. Thereby it reduces the speed ripples of the motor. Also FFT results suggests that the input, output current and voltage harmonics are significantly less in the proposed method compared to traditional electronic fan regulator. Since the production cost of the proposed fan regulator is around Rs. 1870/= (2021 figure), and it involves smart remote controlling facility, the prototype can also be developed as a market competitive product
item: Thesis-Abstract
Mitigating distribution feeder voltage rise optimally using an on-load tap changing transformer and smart inverters
(2021) Manamperi DI; Widanagama Arachchige LN; Ekanayake JB
Higher utilization of distributed generation using solar PV can be observed in recent years due to the gradual reduction of solar panel cost. More additions of solar PV generation in the LV grid can be expected in the future. One of the major challenges encountered by distribution grid operators due to high solar penetration is the voltage rise at the far end of the distribution lines. The centralized control of PV inverters and other controllable devices such as on-load tap changer transformers are a potential solution to solve the voltage rise problem. Optimum centralized control is a heavily investigated topic in the recent past. The optimum control of controllable devices in LV grids can prevent the voltage rise while minimising the energy loss due to resistive loss and generation curtailment. Optimum power flow can be utilized for optimum centralized control. Optimum power flow is a non-convex problem, and there are different solutions to solve it. A sequential mixed-integer second-order cone program-based methodology is suggested in this thesis. According to simulation results, the suggested method has a faster execution time and higher accuracy than the methods discussed in the literature. Also, the thesis proves that the voltage rise can be successfully mitigated by applying the proposed algorithm
item: Thesis-Abstract
Cost effective reliability improvements in 332kV/11kV electricity distribution networks - a case study in western province south 1, Ceylon Electricity Board, Sri Lanka.
(2021) Chameera W R V G D R; Perera HYR; Wijayapala W D A S
Electricity Distribution system in Sri Lanka consists of 33kV, 11kV and Low Voltage (400V/230V) networks. Providing reliable supply to the end user is a challenging task to any utility. Therefore, utility is trying to develop their network to provide a highly reliable supply to user by investing in system developments. In this research, a method is introduced for selecting a cost-effective solution to improve the reliability of the 33kV and 11kV distribution systems among different proposals. Improvement of conductor, its insulation and protection of short duration faults are focused to develop in this research. Part of the method developed in this research, includes the software tool (DisFeeRIA) to analyze the reliability indices and cost for the relevant proposal. Data Base of the DisFeeRIA software tool includes failure rate improvement, mean time to repair, costing of each option considered etc. The analysis is done using user input of the particular feeder, data base of the software which are the part of outcome of the research. Medium Voltage Underground cable (MVUGC), Medium Voltage Aerial Bundle Conductor (MVABC), Medium Voltage Covered Conductor (MVCC), Room Temperature Vulcanizing (RTV) Si-R coating on existing bare line ceramic insulators are considered as options for improving conductor and it’s insulation. One of the latest & innovative technologies used in distribution network, Pulse closing technology is used to reduce momentary interruptions and enhance the life time of the equipment which used in distribution network. Developed software and method were tested by case study done for Distribution network in Western Province South – 01 of Ceylon Electricity Board (CEB). Three (03) feeders were selected in different areas from Urban, Coastal & Rural. The method that is introduced in this research is very important to utilities for planning of Electricity Distribution network.
item: Thesis-Abstract
Techniques to minimize transfer potential near the substation boundaries
(2021) Bhasura PLS; Rodrigo AS
In Sri Lanka, the demand for electricity is growing at a rate of 5-6% each year. Transmission Infrastructure development is an essential task to cater this growing demand. Construction of grid substations and transmission lines are the major projects in transmission infrastructure development. It is very difficult and costly to find suitable lands for construction of grid substations in urban areas such as Colombo and Kandy. The designs of these grid substations are complex and congested, since they are confined to very small land extents. It is vital to ensure electrical safety in a grid substation. Grid substation grounding system plays a major role in electrical safety. The grid substation grounding system carries the electric current to the earth at normal and faulty conditions. This flow of electric currents into the earth increases the ground potential not only in the premises of the grid substation, but also in the neighboring lands. Grid substation grounding system ensures the minimum grounding resistance, safe step potential and touch potential levels in the premises of the grid substation, but it does not cover the area beyond the boundary of the grid substation. Soil structure of a land could be with a uniform soil resistivity or non-uniform and when it is non-uniform, it is considered as multiple layered with different soil resistivity in each layer. The flow of current in the earth depends on the resistivity of the soil layers. Accordingly current flow could be outwards from the land extent of the grid substation or to flow downwards from the surface. This behavior has been tested in this research with an artificially introduced vertical layer of Asphalt around the grid substation to reduce the flow of electric currents towards the adjacent lands from the land of the grid substation. The reduction of flow of electric currents in the upper soil layer of the adjacent lands, reduces the ground potential rise and the electric shock hazard beyond the boundary of the grid substation. The results show that with the increase of the depth and width of the vertical Asphalt layer, the ground potential rise of the adjacent land drops and hence the risk of electric shock reduces.
item: Thesis-Abstract
Analysis of options to limit occurrence and duration of under frequency load shedding in small, renewable dominant power systems:
(2021) Hemachandra MGND; Rodrigo WDAS
The power system Sri Lanka is an islanded power system of a relatively small size. Other than the coal power plants, combined cycle plants and gas turbines, a significant portion of electricity requirement is supplied by large hydro, mini hydro and other non-conventional renewable energy power plants. Accordingly, the power system of Sri Lanka can be identified as a low-inertia power system. CEB, the power transmission operator of Sri Lanka, adheres to N-1 reliability in the transmission network. They are not expected to keep N-1 reliability in generation according to the current practice. It means that the internationally practiced power system reliability levels do not exist in the power system Sri Lanka. Even before Non-Conventional Renewable Energy (NCRE) additions, the power system was largely dependent on under-frequency load shedding (UFLS) after large generator disconnection. Introducing NCRE to the power system has worsened the situation further. The aim of the study was to identify the behavior of the power system of Sri Lanka during and after generation disconnection and study possible methods to improve the power system performance after generation disconnection event. The impact of battery energy storage systems on frequency response was studied for the power system of Sri Lanka. A cost analysis on battery energy storage system was performed. Increase in costs was also calculated if an internationally practiced level of spinning reserve is maintained in the power system Sri Lanka. Suggestions to improve the performance of the system are included in the thesis, based on the findings of the research.
item: Thesis-Abstract
Design of battery supplemented micro - STATCOM and development of associated control algorithms to mitigate power quality issues in low voltage networks
(2021) Hennayaka HMSK; Jayahunga JVUP
Power Distribution Networks are evolving with the rapid penetration of distributed generators and introduction of concepts such as micro grid based Smart Girds. Distribution automation devices and solar PV generators in the present-day power systems makes power distribution networks more and more active. Assurance of a power supply with better power quality for a distribution customer is becoming a challenging task with the penetration of various loads inspired by power electronic concepts. And also, with the enormous penetration of solar PV generators to power distribution networks, bi-directional power flow makes it more challenging. As most of the planning studies carried out to improve Medium Voltage (MV) Networks to address these challenges, less attention has paid for the monitoring of power qualities at Low Voltage (LV) Distribution Networks. This research identifies a vital requirement to improve power quality at the leaf level of LV distribution network and presents a combined solution for most predominant power quality issues exist in LV distribution network. This thesis presents a Micro-STATCOM based solution to address power quality issues by under voltage regulation, over voltage regulation, harmonic mitigation and improving system power factor in LV distribution system. Development of Micro-STATCOM based model with DC power source is presented in order to mitigate major power quality issues exists in the modern LV distribution systems. Performance of the Micro-STATCOM model has evaluated with response time for voltage regulation, resolution of voltage regulation and level of reduction in Total Harmonic Distortion (THD%). Developed Micro-STATCOM was then integrated into modified IEEE 13 Distribution Bus System in order to observe the mitigation of power quality issues. Results obtained by mitigation of each power quality issues in the distribution network are discussed in this thesis. Potential applicability of developed Micro-STATCOM in the practical low voltage distribution networks and other areas are discussed and recommendations are made for the selection criteria to integrate Micro-STATCOMs in LV distribution Systems.
item: Thesis-Full-text
Experimental study on behavior of MOV based surge arrestors under distorted supply voltages
(2020) Illangakoon IPS; Rodrigo WDAS
Surges due to lightning and various switching operations are a common phenomenon in electrical power systems. Due to surges, there can be transient overvoltages in the lines as high as many times the normal supply voltage. Equipment connected to the line cannot withstand these high voltages since the internal circuitry has not been designed to withstand surges. Metal oxide Varistor (MOV) is one of the best clamping devices used for electronic equipment from surges. Metal Oxide Surge Arrestor (MOSA) is made by stacking several numbers of MOV blocks to match system voltages for power system applications. Throughout life, MOVs are exposed to system voltage stress endlessly. Thus, the stress these devices experience is comparatively higher especially in the case of MOSAs. Supply voltage distortion due to harmonics is another common phenomenon found in power systems due to modem non-linear loads connected to power systems. This study is conducted to access the effect of supply voltage harmonics on the life expectancy of MOVs. Electrical and thermal experiments performed to validate relevant models for MOVs. Using simulations, and a life expectancy model, the effect of various cases of voltage distortion studied to find the effect on life expectancy. Based on the above results, recommendations have been made on how to select maximum continuous voltage of surge arrestors to minimize the effect of supply voltage harmonics on life expectancy.
item: Thesis-Full-text
Three-dimensional modelling of earth resistivity for non-uniform soil conditions
(2020) Rajkumar K; Rodrigo A
The Grounding Resistance and Soil Resistivity plays a major role for the safe operation of electrical power systems, earthing system design, lightning protection systems etc. the corrosion level underground items like piling pipelines also can be evaluated with ground resistivity profiles. The researches and standards are mostly referring 2-layer soil conditions and horizontal multi layers, still the results are misinterpreted for different possible types of soil layers. In this research, three-dimensional modelling of earth resistivity layers done using apparent soil resistivity readings and applying the optimization algorithm. A methodology has been proposed to model the actual soil resistivity and layer thickness for a multi-layered soil structure. The apparent earth resistivity measured using Wenner four - point method. The readings further analyzed with MATLAB using genetic algorithm (GA). The results provided by the GA Constitute the three-dimensional modelling of actual earth resistivity profile for a non-uniform soil. The nobility of the research is to obtain the multi-layer soil characteristics and conclude it to a three-dimensional model through the measurements in soil electric properties in the top surface soil.
item: Thesis-Full-text
Demand response control strategy for decentralized air- conditioning systems in microgrids
(2020) Boralessa MAKS; Hemapala KTMU
Distributed energy systems are essential to integrate renewable energy sources to the modern electric grid. Microgrids are a distributed energy system that enables the integration of the intermittent renewable energy sources. Microgrids can operate in islanded mode without the support of the main grid in case of emergency. In this operation mode there must be a wide range of controls to operate the Microgrid until the main grid is available. A microgrid that consists of distributed air conditioning units is considered in this research. This research focuses on developing a control strategy to support the islanded operation of Microgrids using Fast Demand Response and Direct Load Control. The controller developed is a feedback controller with an Integer Linear Programming optimizer that optimizes the thermostat setpoint population of the air conditioners in the control loop. It is showed that the developed controller can be used in achieving power reserve margins, emergency load reduction and cold load pickup mitigation in an islanded Microgrid using simulations.