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Theses and dissertations (Engineering and Built Environment)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/10

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Start date: 2021Subject: search.filters.subject.Energy development--South Africa

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Now showing 1 - 5 of 5
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    Design and application of passive filters for improved power quality in standalone PV system
    (2024-05) Dlamini, Sandile; Adebiyi, Abayomi Aduragba; Kabeya, Musasa
    Harmonic components have developed in power systems due to the non-linear properties of the circuit components utilized in power electronics-based products and their rapid application. Power systems rely on fundamental quantities like sinusoidally varying voltage and current, which oscillate at a frequency of 50 Hz. The standard restrictions of IEEE-519-1992 were utilized as a benchmark in this study. To generate the best output, the total harmonic distortion (THD) should be decreased below the limit, even for certain individual harmonic numbers, and reflect the power factor output. Using the results of the simulation and projections for each mitigation strategy, the THDI can be reduced below the IEEE-519 standard whilst also providing cost and electrical advantages. Analysed and modelled is the PV system, which comprises solar panels, a DC-DC converter, a DC-AC inverter, and a non-linear load. Passive filters are an effective solution for improving power quality in standalone photovoltaic (PV) systems. This dissertation provides an overview of the design and application of passive filters for this purpose. Firstly, an introduction to PV systems and the power quality issues associated with them was preferred. Next, different types of passive filters, namely LC filters, LCL filters and LLCL filters, are discussed along with their advantages and disadvantages, and the design considerations for these filters, including the selection of filter components and the calculation of filter parameters. The application of passive filters in standalone PV systems was then discussed, including their implementation in DC-DC converters and Z-Source inverters and, the design of PWM controllers such as the constant boost control method and simple boost control method. The analysis of the outcome of the engineered systems was conducted according to the IEEE standard and SANS 10142 Standard to protect the connected equipment within the off-grid network. The outcomes pertain to the single-phase stand-alone/off-grid photovoltaic system and the single-phase Z-Source inverter. The Z-Source inverter is equipped with two distinct methods for PWM control, namely the constant boost control method and the simple boost control method. All three designs incorporate three passive filters, namely the LC filter, the LCL filter and the LLCL filter. The results were obtained from the network consisting of three distinct designs. LLCL demonstrates superior performance as a passive filter, substantiating its position as the optimal choice. The optimal outcomes of a single-phase off-photovoltaic (PV) network can be achieved using LC, LCL and LLCL filters, with corresponding percentages of 2.99%, 2.45% and 1.71% respectively. Unfiltered was 89.05%, which is not good for the equipment connected to the network. The Z-Source showcases the capability of voltage amplification to an infinite level, rendering it highly effective in minimizing total harmonic distortion. This research investigation further demonstrated the efficacy of the Z-Source Inverter with Constant Control Boost Method and Simple Boost Control Method, achieving unfiltered total harmonic distortion levels of 38.85% and 44.96% respectively. The Z-Source inverter, when combined with the Constant Boost Control method and Simple Boost Control method, exhibits various filter configurations such as LC, LCL, and LLCL filters. In the context of the constant boost control and simple boost control methods, it is imperative to assess the total harmonic distortion percentage of voltage and current for LC, LCL, and LLCL configurations. The constant boost control voltage (LC, LCL, LLCL) and current total harmonic distortion (LC, LCL, LLCL) are measured at 4.177%, 2.655%, 1.951%, and 2.958%, 2.09%,1.465% correspondingly. The voltage-based boost control methods, namely LC, LCL and LLCL, exhibit total harmonic distortion levels of 2.345%, 1.920% and 0.211%, respectively. Similarly, the current-based boost control methods, LC, LCL and LLCL, demonstrate total harmonic distortion levels of 2.346%, 1.921%, 0.211%, and 2.346%, 1.921%, 0.211%, respectively. Finally, the dissertation wrapped up by exploring the potential of passive filters for enhancing power quality in standalone PV systems. The thesis offers a comprehensive investigation of the design and implementation of passive filters in standalone PV systems, providing valuable insights for engineers and researchers in the field. It enhances understanding and utilization of these imperative devices.
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    Power flow and faults analysis of a hybrid DC Microgrid : PV system and wind energy
    (2021-12-01) Zulu, Musawenkosi Lethumcebo Thanduxolo; Ojo, Evans E.; Akinrinde, Ajibola O.
    Rural electrification has become a very important means of improving the standard of living of rural dwellers, a process which also helps in the electrification of remote and isolated regions. Presently, the electrification of such regions can be achieved through the use of renewable energy. The use of renewable energy sources such as PV and wind energy is gaining popularity as the solution to achieving the electrification of rural areas, such as the use of the microgrid, which can be in the form of an AC or DC microgrid. The DC microgrid can be used to connect distributed energy resources and its energy storage is considered to be an economical system to meet consumer demand due to its benefits, namely environmental friendliness, reliability and good performance in load distribution. The power system may experience many faults when transferring power via overhead transmission lines to the load. When these faults occur, it is important to detect the location and isolate the part that had experienced the fault quickly, without de-activating the whole microgrid. The main aim of this study was to conduct a power flow and faults analysis on a hybrid DC microgrid model with battery storage. The hybrid energy sources for the DC microgrid are the PV system and wind energy system. Firstly, this research conducted a power flow analysis for the hybrid DC microgrid. Secondly, a fault analysis was carried out on the system and both the power flow and the fault analysis were formulated through implementation in a MATLAB/Simulink environment under various conditions in order to ascertain the stability and reliability of the system. Various MATLAB/Simulations were carried out, including the DC single-line-ground fault and DC line-line fault and are analysed in a designed hybrid DC microgrid power system. The results showed that DC line-to-line and DC line-to-ground faults lead to the imbalance of DC voltage, which is difficult to re-balance and stabilize in the system after the existence of these faults. When these faults occurred in the system, there was immense fluctuation and unsteadiness of output load power delivered to consumers. Moreover, wind-generated power on the generation side was severely affected. Based on the results and analysis of those results, the hybrid DC microgrid is seen as a satisfactory and optimum concept for the generation and transmission of power for rural and isolated area electrification, i.e. it can provide power to remote areas that cannot be reached by the national grid. The study revealed, based on the analysis of results, that it has an effective response under fault conditions. Results for a hybrid DC microgrid revealed that high quality of power is experienced in load distribution. Also based on the results, when DC faults occurs there is disturbance to output.
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    Design of control strategies for frequency stability of PV-thermal interconnected power system
    (2021-02) Estrice, Milton Solomon; Sharma, Gulshan; Akindeji, Timothy Kayode
    Renewable energy in particular solar energy is a viable option to meet the increasing energy demand for the modern world. The Solar resource in South Africa is among the highest in the world. With the progression of modern society, both energy demands and energy prices are increasing, which has welcomed the introduction of renewable energy resources as an alternative. However, solar radiation varies over the complete day sometimes over the season, and sometimes over the complete year. Further, the power demand is highly variable in nature. Hence, the generated power should match the customer demands over the period of twenty-four hours, and further, it should be economical for customers and electrical utilities. Hence, this study will focus on integrating PV plants with thermal plants to meet the rising customer power demand. The integration of PV with thermal power plants will bring some new challenges in the domain of power system operation & control which is the frequency of the power system should be restricted to well-defined values. Hence, suitable control strategies are to be developed for the successful and smooth operation of the power system. In this research work, an attempt is made to investigate an interlinked system comprising of a thermal and a PV generation system. The control strategies based on PID controllers and their gains tuned through effective tuning techniques are presented. In addition, the concept of fuzzy logic is used to address the problem of frequency managing of PV-Thermal via effectively designing fuzzy proportional, fuzzy integral, and fuzzy PI built control strategies to ensure the frequency regulation of the energy system. The obtained results are shown via a graphical approach, and the best control design is explore and suggested for the considered system. In addition, the scope for further improvement and possible direction areas are also explored and listed in this report.
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    The analytical and experimental study on the establishment of a tidal power plant in South Africa
    (2021-02) Mtukushe, Namhla Faith; Ojo, Evans Eshiemogie
    The majority of South Africa’s electricity is generated from fossil-fuel plants that use mainly coal. In these power plants, the combustion of these fossil fuels liberates greenhouse gasses into the atmosphere that contribute to climate change. This problem coupled with the rapid depletion of fossil fuels has necessitated the need to explore the alternative form of energy such as renewable energy. Tidal energy is a form of ocean energy that can be considered as an alternative energy resource or renewable energy source. This form of energy has not been explored in South Africa, the only country in the world that is bounded by two oceans; the Indian and the Atlantic. Tidal energy can be harnessed from the movements of tides to generate electrical power. This study considered the possibility of harnessing tidal energy as the alternative energy source for power generation which can be used to mitigate the challenges associated with the energy crisis currently being experienced in the country. For this study, an extensive literature review was carried out to understand the tidal phenomenon, the concept of energy conversion from tides, the different techniques or technologies that can be used to generated power from tides. There are two main technologies used for converting tidal energy to electrical energy and these are the tidal barrage and the tidal streams. Based on the inferences drawn from the literature reviews concerning the tides experienced around the South Africa coastal region, it was identified that the tidal stream technique is applicable. Harmonic analysis of the tidal resource for four identified sites was conducted, from these analyses, Esikhawini was selected as an optimum site. Tidal streams extract the kinetic energy of tides and the mode of operation of tidal stream plants is determined by the type of tidal turbine employed. Several turbine designs were reviewed, a helical cross-flow turbine was selected due to its self-starting capability and its ability to operate in reverse stream flows. For this helical turbine, an analytical model using the blade element momentum theory (BEMT) was developed and was implemented on MATLAB environment. For the experimentation, a prototype was developed and tested in a laboratory concrete flume in the department of Civil Engineering at the University of KwaZulu-Natal. Based on the experimental results, an analysis of the unit turbine was done which was used to propose a conceptualized tidal power plant. Hence, the proposed tidal power plant was used to justify the reason for embarking on this study which is to ascertain the possibility of establishing a tidal power plant in South Africa.
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    Application of optimal control for power systems considering renewable energy technologies
    (2021-03) Chetty, Dhanpal; Sharma, Gulshan; Davidson, Innocent Ewaen
    Over the last decade, power generation from renewable energy sources such as wind, hydro and solar energies have substantially increased globally and in South Africa. Of all the renewable energy sources, wind energy appears to be the most promising, considering design and costs. However, due to the intermittent nature of wind, the increased integration of wind energy into existing power systems raises several control challenges related to load frequency control (LFC) and tie-line power system stability. The stability of modern power systems, incorporating wind energy generations, will be significantly enhanced with the development of LFC strategies based on modern control theory, which is the focus of this research. This thesis presents the design, modelling and analysis, of two LFC control strategies for interconnected power systems, having wind power integrations. The first design is an optimal control strategy, based on error minimization through full state vector feedback, for a two-area interconnected power system consisting of hydro-thermal generations. The second design is a model predictive control (MPC) strategy, based output vector feedback of system state parameters, for a two-area interconnected power system consisting of thermal generations in each area. Both designs include the active power support from doubly fed induction generator based wind turbines (DFIG) in conjunction with the combined effort of a thyristor control phase shifter (TCPS) and super conducting magnetic energy storage unit (SMES). Both control strategies were simulated in MATLAB Simulink and positive results were obtained. The results show that the optimal control strategy is enhanced with power integrations using DFIG based wind turbines combined with the TCPS-SMES units and the MPC strategy is very robust and provides better dynamic performances even with parameter variations and generation rate restrictions.