http://localhost:8081/jspui/handle/123456789/38 Thu, 07 May 2026 21:26:46 GMT 2026-05-07T21:26:46Z http://localhost:8081/jspui/handle/123456789/20421 Title: INVESTIGATION OF ELECTROMAGNETICALLY INDUCED VIBRATIONS IN ASYNCHRONOUS HYDROGENERATOR Authors: Ali, Javed Abstract: In India, the first variable speed Pump Storage Power Plant (PSPP) having four nos. of 250 MW Doubly Fed Induction Machine (DFIM) totaling a capacity of 1000 MW recently started operation at the Tehri dam of Uttarakhand state. Variable speed Pump Storage Power Plant (PSPP) employing a Doubly Fed Induction Machine (DFIM) is an acceptable option for sites with wide variation in water head since they provide variable speed operation with reduced power converter rating and high dynamic stability. In DFIM, power converters on the rotor side function as an excitation system regulating the machine's real and reactive powers based on set points (reference) and feedback signals from various sensors. Consequently, in order to maintain the exponential rise in renewable energies, the sector of energy conversion must improve electrical machine performance. These performances are assessed based on standards unique to each of the physical domains i.e., thermal management, control, power converters, losses in electromagnetic materials, and acoustics—involved in the design of electrical machines. Noise and vibration are associated with a number of difficulties, including mechanical fatigue (in the energy sector, such as hydroelectric generators), security (in military applications), vibroacoustic comfort (in rail, automobile, or home applications), and safety and health issues (in industrial environments). Vibrations can degrade working conditions, limiting machine's life and raising maintenance costs. Standards are mostly used to evaluate the impact on the environment. However, individual people's subjective feelings vary depending on the circumstances. The Covid-19 health issue and containment efforts have brought attention to how pervasive noise pollution is in our communities. This work focuses on the vibrations from electromagnetic sources in doubly fed induction machine. Electromagnetic fields, which produce parasitic forces in active structures, are associated with these particular vibrations. The interaction between these magnetic forces and the structural mechanics causes noise and vibration. Nowadays, manufacturers of electrical machines are being forced by economic limitations to make lighter machines, which raises the vibration level and makes machine structures more pliable. Furthermore, the behavior of electromagnetic fields and, eventually, magnetic forces can be greatly impacted by modifications in topology as well. Reducing vibrations without sacrificing electromechanical performance is the primary challenge in machine design. A comprehensive literature survey is carried out in the area of electromagnetic vibrations in electrical machines such as squirrel cage induction machines, synchronous machines, permanent magnet synchronous machines etc. The source, effect, and cause for electromagnetic vibrations in DFIM is studied through simulation and experimental tests. From the literature, it is found that the electromagnetic vibration in large rated DFIM stator serving to hydropower applications is not yet explored enough. Mon, 01 Apr 2024 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/20421 2024-04-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/20415 Title: AN INTEGRATED MODELING APPROACH FOR HYDROPOWER POTENTIAL ASSESSMENT AND SUITABILITY ANALYSIS Authors: Tefera, Wasu Manawko Abstract: As the demand for energy continues to rise, experts and energy supply agencies are actively seeking diverse power sources to fulfill the demands. Among several non-renewable and renewable energy resources, hydropower become a priority because of its sustainability and environmental suitability. As a result, experts in the field focus on developing approaches for suitability assessments for hydropower projects and analyzing the spatial distribution of the potential sites at regional as well as global scales. This strategic approach would enable policymakers and government stakeholders to gain valuable insights, facilitating the idea and planning of future sustainable and environmentally compatible energy development endeavors. This study focused on hydropower potential assessment and feasibility analysis, including the catchment and global scale, as several limitations exist in the existing literature. For example, previous studies have limitations in considering the recently updated hydrological information. In addition to this, some of the global scale studies used topographical information that has left some parts of the landmass uncovered. Moreover, many of these studies relied on relatively coarse-resolution digital elevation models (DEM), which may not accurately capture where finer details are required for precise assessment. Similarly, regarding regional and catchment-based hydropower potential assessment studies, many of the proposed methodologies primarily focus on assessing small-scale and Run–of–River (RoR) type hydropower potential possibilities. However, it is reported that a significant amount of untapped hydropower potential is available, especially in developing countries, which needs to be assessed via the development of comprehensive methodological frameworks. Therefore, the study comprises two main parts. The first part of the study provides an assessment of the worldwide hydropower potential, mainly the RoR type, and evaluates the spatial distribution. The analysis focused on assessing possible hydropower potential and evaluations under theoretical, technical, economic and environmental constraints. The study used a relatively recent (1965 – 2014) global runoff dataset having a resolution of 0.5o x 0.5o for the computation of design discharge and a 3' x 3' (approximately 90 m x 90 m at the equator) resolution DEM covering 90oN - 60oS, for topographical analysis. Design discharges (Qd) at 30%, 75% and 95% flow dependability were used in the assessment and evaluations. The study assessed the suitability of potential sites with an interval of 0.5 km to 5 km in the river networks and used empirical relations derived from the observed cost of electromechanical equipment to corresponding head (H) and installed power (P) for economic analysis. The analysis revealed that the global theoretical hydropower potential ranges from 25.48 Peta watt-hours per year (PWh/yr) at 95% flow dependability to 184.17 PWh/yr at 30% flow dependability. Of these, the energy ranges from 7.06 PWh/yr to 49.05 PWh/yr, which is technically feasible considering a design discharge determined from a flow in ranges of 95% to 30% flow dependability. After excluding environmentally unsuitable and economically less competitive (Levelized Cost of Electricity (LCoE) > US$ 0.1/kWh) potential sites, it was estimated that an exploitable hydropower potential of 5.42 PWh/yr at 95% flow dependability to 39.56 PWh/yr at 30% flow dependability would be available globally. Fri, 01 Mar 2024 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/20415 2024-03-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/20414 Title: Rainfall-Runoff and Sediment Yield Modelling under Climate Change Authors: Hailu, Melese Baye Abstract: The primary aim of this research is to improve soil conservation practices in the Tekeze watershed. To achieve this goal, several procedures were carried out, including assessing the amount of erosion in the basin, evaluating different techniques to prevent erosion, and examining the impact of climate change on the watershed. For a better understanding of the work and findings, the abstract is described in three separate sections. Each section provides more detail on different aspects of the research, such as the methodology used, the results obtained, and the implications of the findings. The details of each abstract are described as follows: Assessment of erosion in each sub basins Land erosion is a significant issue worldwide because of inadequate land use and changes in land cover. This phenomenon results in the loss of the top layer of nutrient-rich soil, which is crucial for the productivity of the land and the storage capacity of reservoirs. As a result, it has negative impacts on the global economy. Therefore, soil conservation practices are being implemented globally to address this issue. However, carrying out large-scale soil conservation in developing nations can be difficult without significant investment. To increase the efficiency of soil conservation efforts, it is essential to identify the region’s most vulnerable to erosion and implement necessary remedial measures. In this study, the SWAT model was used to determine areas prone to erosion. While the model is widely accepted for water resource management, allocation, and prediction globally, there is uncertainty in the model's results that may arise from measured data, model structure, or input data. Therefore, extensive sensitivity analysis, uncertainty prediction, and model calibration are necessary to obtain accurate simulation results. The study employed several algorithms, namely SUFI-2, ParaSol, GLUE, and PSO, that are integrated with SWAT-CUP software for model calibration, sensitivity analysis, and uncertainty prediction. Results show that out of these four algorithms, the SUFI-2 algorithm provided the most accurate simulation outcomes, with R2 values of 0.76 and 0.85 under streamflow and R2 values of 0.8 and 0.66 under sediment for calibration and validation, respectively. After simulating 34 sub-basins, the study found that five sub-basins, namely 1, 3, 5, 14, and 17, are the most susceptible to erosion. These sub-basins exhibit a mean annual sediment yield of 23 tons/ha/year, indicating a high risk of soil erosion. This result emphasizes the importance of identifying areas prone to erosion and implementing effective soil conservation practices to mitigate the negative impacts of erosion on the global economy. Assessment of soil conservation options Soil conservation (SC) is essential to maintain the reservoir service life and increase the yield since soil erosion is a major global concern that adversely affects the storage capacity and land fertility. This study evaluates the spatio-temporal variation of soil erosion using popular SWAT model and identifies the best SC practice for Tekeze watershed located in Northern part of Ethiopia. To accomplish this, four soil conservation management scenarios involving baseline, terracing, contouring, and grassed waterway scenarios are selected for soil loss evaluation. The SWAT model was calibrated and validated with R2 values of 0.7 & 0.9 and NSE values of 0.8 & 0.7, respectively, indicating satisfactory model performance. Five sub-basins of the catchment were found to be more susceptible to erosion with an average annual soil loss of 25.15 tons/ha/yr. However, by implementing terracing, grassed waterways, and contouring techniques, the level of erosion in the watershed has significantly decreased when compared to the baseline scenario. Specifically, the implementation of terracing led to a 35.18% reduction in erosion, while grassed waterways and contouring resulted in reductions of 27.11% and 18.76%, respectively. These results demonstrate the effectiveness of these techniques in mitigating erosion within the watershed. Since the investment cost of the execution of an SC measure in a large watershed is very high, priority areas are also identified for cost savings as well as improved work efficiency. Fri, 01 Mar 2024 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/20414 2024-03-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/20315 Title: ANALYSIS OF SUB SYNCHRONOUS OSCILLATION IN HYDROPOWER SYSTEMS Authors: Mohale, Vijay Pandurang Abstract: Hydropower is a leading energy resource amongst the world’s renewable energy capacities. According to the International Hydropower Association Status Report 2023, hydropower contributes 15.7% of total electricity production. To achieve proficient generation in the arena of the hydropower sector, a widespread design with recent trends and developments in technology is obligatory. Asynchronous machines are now extensively used in hydropower plants due to their flexibility in power generation, better energy efficiency at wide variation in water head, partly rated power converter interface, and intrinsic short-circuit and overload protection. Asynchronous generators of large capacity (e.g., 250MW) need further research to identify the amount of compensation in transmission lines in view of variable speed of operation. Sub Synchronous Oscillation (SSO) is generated in long distance transmission lines with the series compensation of certain amount. This SSO disturbs the constancy as well as security of the power system. The rotor side of the DFIM is typically linked to the grid through back-to-back power electronic converters, while the stator circuit is connected directly to the grid. As a result, it is considered a partial isolation from the grid and eliminates the requirements for synchronous operation of the turbine to deliver power to the grid. However, it is vulnerable to sub synchronous oscillations when connected to series compensated transmission lines or under weak grid conditions. For long distances, extra high-voltage transmission lines are used to transfer electricity from large-rated electric power stations to consumers for higher energy efficiency. To increase the power transfer capability, capacitor units are connected in series with the long transmission lines. However, SSO is a prevalent issue when DFIM is radially connected with the series compensated transmission lines. The events on the Texas Electric Reliability Council's electrical network, as well as the electrical networks of southwestern Minnesota, the United States, and Hebei, China, are examples of sub-synchronous oscillations that occur in wind farms with doubly fed induction machines. Based on literature and real events, it is understood that the research on SSO has been conducted extensively for wind power applications. However, the research conducted on SSO with DFIM-based large hydro units is limited, but it is essential in view of variable speed operations of the turbine and generator, multi-channel converters in the rotor circuit, and DC link capacitors. Sat, 01 Jul 2023 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/20315 2023-07-01T00:00:00Z