Institutional-Repository, University of Moratuwa
Welcome to the University of Moratuwa Digital Repository, which houses postgraduate theses and dissertations, research articles presented at conferences by faculties and departments, university-published journal articles and research publications authored by academic staff. This online repository stores, preserves and distributes the University's scholarly work. This service allows University members to share their research with a larger audience.
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Recent Submissions
item: Thesis-Abstract
Induction motor and vector control based programmable loading unit for load testing of different motors
(2025) Ranasinghe, RADS; Karunadasa, JP
Electrical machines are extensively utilized in contemporary systems that require mechanical operation. Along with its popularity, ongoing studies and developments are underway for machines’ performance and efficiency enhancement. Motor testing holds a significant role in research and development. It was stated that motors must be tested under various practical scenarios such as post manufacturing, rewinding, and changes in environmental factors etc. It was stated the type tests conduction on motors are necessary to ensure that it meets specified standards and regulatory requirements. The purpose of these tests is to verify thermal and mechanical compatibility for supplying the rated power over an extended period. Current practice for testing using conventional loading units like eddy current brake testing, temperature rise testing and DC lamp load testing have their own drawbacks like less controllability, bulky arrangement, being expensive and inefficient.
However in this research, the proposed loading unit simulation model was designed to verify a more controllable, compact, simple and yet cost effective loading unit comparatively for conventional methods which can be used to test motors. The proposed programmable loading unit simulation consist of an Induction Motor (IM) connected with a test motor where the IM is operated by power electronics(PE) controllers with the usage of vector controlling technique. The PE controllers include of a bi-directional IGBT based rectifier to enable the bidirectional flow of power between induction motor and the utility grid and CC PWM VSI to energize the Induction Motor.
The study aims to progressively develop a simulation of a vector control based 3 phase induction motor programmable loading unit that can be directly coupled to a given motor to conduct load testing.
item: Thesis-Full-text
Studying the turbine-generator oscillations a case study of Lakvijaya Power Station
(2024) De Silva, LUN; Prasad, WD
The Lakvijaya Power Station located in Narakkalliya, Norochcholai, Sri Lanka plays a crucial role in the nation’s energy sector, contributing significantly by almost half of the load to the electricity grid at most of the year. However, similar to any large-scale power facility, it also faces operational challenges, including turbine-generator oscillations. This research study presents a comprehensive study focused mainly on understanding and help mitigating these oscillations for improved operational efficiency and grid stability.
This research inherits a good conjunction of theoretical analysis, numerical simulations, and practical measurements to characterize the nature and causes of turbine-generator oscillations at Lakvijaya Power Station. Through detailed modelling, factors such as turbine multi-stages dynamics, generator response characteristics, speed governor controls, excitation controls, and grid interactions are investigated to identify potential sources of oscillations.
Furthermore, advanced signal processing techniques are applied to real-time operational data to detect and analyze oscillatory patterns. This includes frequency domain analysis and modal analysis with modulation study to pinpoint dominant oscillation frequencies and modes.
The results of this study offer valuable insights for power plant operators, grid operators, and researchers involved in the operation and optimization of large-scale power generation facilities. By detailed in-depth evaluation of turbine-generator oscillations at Lakvijaya power station, this study contribute to the broader country’s visionary policy of ensuring reliable and efficient electricity supply in Sri Lanka’s energy landscape.
item: Thesis-Full-text
Configuring a power system stabilizer for improved dynemic performance a case study for Lakvijaya power station
(2024) Chandrasena, HLL; Prasad, WD
The concept of Power System Stabilizer (PSS) is widely accepted worldwide as a supplementary excitation control method to improve the dynamic performance of power systems. This work presents the implementation of a PSS by proposing a robust tuning procedure for the inbuilt PSS functions in UNITROL 5000 excitation controllers, focusing on the ST1A type static excitation system. Additionally, this research serves as a case study for the Sri Lankan power system centered around the Lakvijaya Power Station in Sri Lanka, which is the largest coal power plant in the country. The proposed tuning procedure demonstrates how the conventional Frequency Response-Based Method and a Model Based Method incorporated with an optimization technique, can be used in a cascaded format to significantly enhance the dynamic response of the power system. The optimization technique has been completely automated on the Python coding platform, which employs an Eigenvalues-based approach to optimize in the presence of comprehensive dynamic data of the Sri Lankan power system up to the 33kV voltage level.
item: Thesis-Full-text
Development of a matrix based utility scale feeder reconfiguration algorithm for supply restoration
(2023) Sandaruwan, WNDC; Jayatunga, JVUP; De Silva , PSN
Handling of supply outages are critical task in electricity distribution utilities. One of major expectation of any electricity customer is receiving continues electricity supply. Responsibility of a utility is also supplying electricity continuously with minimum outage time duration. Although unplanned outages cannot be reduced to zero, those can be managed and restored the supply as early as possible to minimize the outage time duration and minimize affected area. Outage time duration and the area affected is directly influenced to revenue loss of both utility and commercial customers.
In an event of unplanned supply outage, utilities have to carried out fault localization, fault isolation and supply restoration temporary, until the fault is cleared to restore the supply to the fault occurred, isolated section. These steps are currently done as manual method. In this research utility network was modeled as a matrix and above-mentioned fault localization, isolation and supply restoration were done by an algorithm to maximize the efficiency and minimize outage time period.
Centrally handling of outages were focused on this research. Matrix-based utility network model and algorithm for the network calculations was expected to validate through this research. The algorithm produces switching instructions to fault localization, faulty section isolation and supply restoration based on the outage massages were fed. It was simulated in MATLAB environment. Algorithm was developed considering hypothetical network and different test cases of possible fault scenarios. Outage data were fed to the algorithm manually and compared the results given by the algorithm with manual method results for the same outages. Algorithm validated by actual network data with manually fed outage cases. Algorithm results were tallied with the manual results. It shows that centralized matrix-based utility network representation and matrix-based algorithm is suitable to solve networks related issues more efficiently than manual & local methods.
item: Thesis-Abstract
Sri Lankan government fertilizer ban policy’s impact on tea exportation
(2025) Alwis, MSP; Talagala, PD
The recent policy of the Sri Lankan government, banning chemical fertilizers, has sparked discussions and concerns regarding its impact on several industries. Among them, the tea industry draws utmost attention due to its contribution to Sri Lanka’s export revenue. Sri Lankan tea is worldwide renowned for its high quality, and tea exports significantly contribute to Sri Lanka's economic growth. Since Sri Lanka's economy relies heavily on tea exports, it is crucial to examine the possible outcomes of the government policy on fertilizer importation. Although the objective of this move by the Sri Lankan authorities is to advance organic farming in order to maintain environmental sustainability, the immediate effects on tea production and exportation have to be well studied. Since independence, the Sri Lankan government has followed numerous policies in the agricultural sector. Tea has earned a greater attention of government agricultural policy since it is the single most important crop next to rice. While there is limited research specifically addressing the impact of government fertilizer ban policy on tea exports in Sri Lanka, there is a timely requirement in studying the impact on the tea industry due to government policy changes. The significance of this study lies in its potential to revise the agricultural practices as well as the economic dynamics of one of the country’s key industries. Since Sri Lanka is globally renowned for its high-quality tea, any policy involved in its production procedure has considerable implications. The aim of this study is to evaluate the impact of the Sri Lankan government's fertilizer ban policy on tea exportation. This research analyzed how the policy has influenced export volumes and trends, utilizing quantitative methods to assess the short-term and long-term effects on the tea industry. Tea export data, tea production data, and fertilizer import data from 2012 to 2022 were used in this study. As the methodology, time series approaches were used in this study in order to separately identify the short-term impact of Sri Lanka’s government fertilizer ban policy. Granger causality tests were conducted, and long-term relationships were checked using co-integration tests. The ARIMA and ETS models along with VAR models and VECM were built to identify the effects of fertilizer banning. There was clearly a short-term relationship between fertilizer imports and tea exports as well as tea exports and total tea production. Based on the findings of the analysis, we can conclude that the ban on fertilizer importation impacts tea exportation more significantly than tea production. This is likely because quality of tea, which is crucial for exportation, is more directly affected by the availability of fertilizers than the overall quality of tea produced. Usually, tea exports have to be of high quality. Due to the fertilizer import ban, there must be a lack of fertilizer used, resulting in a quality drop in tea produced