Browsing by Author "Oyedokun, David T O"

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    Microgrid planning and design under uncertainty: A case study in Northern Angola
    (2020) Kamanzi, Brian; Oyedokun, David T O
    The national energy development plan for Angola, Angola Energia 2025, identifies the need to balance efforts to expand access to electricity in countries with low levels of industrialisation, across the urban and rural spheres. This need is coupled with the urgency of investing in environmentally sustainable technologies responding to local and international targets addressing the impacts of Climate Change. This dissertation seeks to assess the feasibility of an electricity micro-grid system (a) for uplifting the quality of life and development of two neighboring Angolan coastal villages, and (b) one that (I) depends entirely on domestic renewable sources of electricity generation; (ii)has a sustainable initial generating capacity of not less than 2MW and (iii) is flexible enough to undergo future expansion as needed over time. The design of a proposed Microgrid solution for N'zeto and Tomboco villages located in Angola is developed through a thorough context study used in conjunction with remotely acquired contextual data and a variety of estimation and model techniques. Microgrids are defined as a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity functioning with two modes of operation. The Microgrid design process requires a set of context specific empirical data ranging from load profiles of the site under survey to the availability of endogenous energy resources. The existence of documented public policy, the domestic availability of renewable resources in and around the study area, the present low population density in rural Angola, the low level of Angola's rural electrification , and the existence of financing mechanisms which the country can afford. The load profile and contemplated electrical energy consumption in the study area along with an estimation of the availability, nature, diversity, and extent of the domestic renewable energy sources are developed as key inputs for design decisions related to component sizing. A comparative evaluation of their performance of two proposed candidate solutions, derived from the assessment of the available energy resources is used as a basis to select preferred candidate. The proposed solution is subjected a sensitivity analysis of key design variables. Aspects of the selected design, including concept of operations, reticulation and a discussion on the possible downstream benefits are elaborated in compliance with the technical and policy constraints of the proposed electrification scheme.
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    Power Maximization and Turbulence Intensity Management through Axial Induction-Based Optimization and Efficient Static Turbine Deployment
    (2021-08-12) Charles, Mfon; Oyedokun, David T O; Dlodlo, Mqhele
    Layout optimization is capable of increasing turbine density and reducing wake effects in wind plants. However, such optimized layouts do not guarantee fixed T-2-T distances in any direction and would be disadvantageous if reduction in computational costs due to turbine set-point updates is also a priority. Regular turbine layouts are considered basic because turbine coordinates can be determined intuitively without the application of any optimization algorithms. However, such layouts can be used to intentionally create directions of large T-2-T distances, hence, achieve the gains of standard/non-optimized operations in these directions, while also having close T-2-T distances in other directions from which the gains of optimized operations can be enjoyed. In this study, a regular hexagonal turbine layout is used to deploy turbines within a fixed area dimension, and a turbulence intensity-constrained axial induction-based plant-wide optimization is carried out using particle swarm, artificial bee colony, and differential evolution optimization techniques. Optimized plant power for three close turbine deployments (4D, 5D, and 6D) are compared to a non-optimized 7D deployment using three mean wind inflows. Results suggest that a plant power increase of up to 37% is possible with a 4D deployment, with this increment decreasing as deployment distance increases and as mean wind inflow increases.
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    Subsynchronous resonance in series compensated networks with high penetration of renewable energy sources
    (2022) Chikohora, Tinashe Edward; Oyedokun, David T O
    The global shift towards clean energy has seen a spiked rate of environmentally friendly renewable energy sources (RES) as utilities and regional energy blocks battle with rising demand. RES sites may be located in remote or populated areas with limited servitudes. To reduce investment costs, grid impact study assessments conducted by utilities often recommend new power plants to cut-in nearby existing lines for power evacuations after considering availability of wayleaves and other socio-economic concerns. There are foreseen and planned connections of RES evacuating power via series compensated lines in Africa. However, integrating RES through series compensated lines results in subsynchronous resonance (SSR) between generator rotors and the grid. SSR is a phenomenon where there is exchange of electrical energy between the generator shaft system and the transmission system below the fundamental power frequency leading to electrical instability. The future trend in power systems entails deeper investments of the same highlighted SSR inducing sources such as series compensation. This brings uncertainty and misperceptions in respect to effective management of the SSR problem translated to a case of either retarding power system investment without SSR against reinforcing grid investments with SSR inducing consequences. The dissertation dissects the SSR problem with emphasis on its management in a modern power system environment receiving rising RES and flexible alternating current transmission systems (FACTS) connections through series compensated lines. The simulations performed in this study utilised the IEEE first benchmark model (FBM) within Digital Simulation and Electrical Network – PowerFactory (DIgSILENT) software. The unmodified FBM served as a base case representation of the power system without RES or STATCOM (static synchronous compensator) penetrations. The various modifications to the FBM captured multiple scenarios representative of rising penetrations of wind power, solar power and static compensators. The generator, shaft, busbar terminals and series capacitor were monitored and analysed to derive SSR modulated torsional effects after applying a 3-phase fault to the system for 75 milliseconds. From the perspective of conventional synchronous non–renewable generation, decrease in SSR probability is achievable by adding RES like solar PV power in the vicinity. Another output from the simulations confirmed that PV generation does not participate in SSR occurrence as seen by its pre and post fault conditions recovering immediately and remaining constant afterwards. In addition, the results from the modal analysis comparison reinforced that as more RES or STATCOM devices are connected to the FBM, the overall system improves on oscillatory stability as seen by the oscillatory eigenvalue real parts becoming more negative and the damping ratios more positive. The future work involves analysis of SSR in other RES and how SSR protection can be incorporated in protection relays using a filtering method based on the prony analysis.