Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / Spoornet is one of South-Africa’s largest railway companies. It is very important to operate the railway system as cost effectively as possible. A large portion of the railway operates from 3 kV DC traction supplies. One method of cost saving is to utilise the regenerative braking mechanism of the electric trains.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / Although regenerative braking has been in used in railway systems for a long time already, the energy generated was dissipated in resistor banks. The rapid advances in the power electronics field, accompanied by the development of faster and higher power switching devices in recent years, now make it possible to convert the regenerated electrical energy from DC to AC, which can then be injected into the Eskom grid. A 1.5 MW full scale prototype system was built, installed and tested in a Spoornet DC traction substation. A seven level series-stacked converter topology was used along with a specially designed injection transformer. The system was controlled by the PEC 33 controller board, which was developed at the University of Stellenbosch. The primary function of the system is to function as a regeneration converter and as a secondary function act as an active power filter.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Approved for public release; distribution is unlimited / The naval vessels of the future will require lighter, more compact, and more versatile power electronics systems. With the advent of the DC Zonal Electrical Distribution System, more innovative approaches to the conversion of the dc bus power to ac power for motor drives will enhance the efficiency and warfighting capability of tomorrow's ships. This thesis explores the concept of a hybrid dc-ac power converter that combines a hysteresis controlled inverter with a six-step bulk inverter. A six-step bulk inverter is built from discrete components and tested in simulation and hardware. The two inverters are connected in parallel to provide a high-fidelity current source for a three-phase load. The addition of the hysteresis inverter to the bulk inverter adds a closed current loop for more robust control and improves the quality of the output load current. / Major, United States Marine Corps

Submitted in fulfillment of the requirements for the degree of Master of Engineering in Electrical Power Engineering, Durban University of Technology, Durban, South Africa, 2017. / Voltage instability and increased power loss on transmission lines are major challenges in power transmission due to ever increasing load growth. This work investigates the effect of Static Synchronous Compensator (STATCOM) to mitigate power losses and enhance the voltage stability of a transmission system. STATCOM, a shunt-connected power electronic device, operate as a Voltage Source Converter (VSC) to improve power transfer capacity of transmission lines by injecting a set of three-phase balanced sinusoidal current with controllable magnitude and phase angle into the transmission lines to regulate the line voltage and compensate for reactive power at the Point of Common Coupling (PCC). To validate the capacity of STATCOM in this light, a modified model of IEEE 14 bus test system was simulated using DIgSILENT PowerFactory v15. Four different load profiles were included by increasing the base load in a step of 10%. In each case, power flow was run with and without STATCOM incorporated in the network with a view to determine the impact of STATCOM on bus voltage and transmission line losses. The simulation results are obtained were recorded and analyzed. It is noted that there was sufficient improvement in the new voltage profile obtained for the weak buses of the system, the active and reactive power losses were mitigated by 17.73% and 24.80% respectively when STATCOM was incorporated at normal load. The results showed that STATCOM could give quick voltage support to reduce the likelihood of voltage collapse and mitigate power losses along the transmission lines. Reduction of reactive power losses along the lines is higher than the active power losses resulting in the improvement of the voltage profile as the device is connected to the system. / M

Many issues related to the design and implementation of a maximum power point tracking (MPPT) converter as part of a photovoltaic (PV) system are addressed. To begin with, variations of the single diode model for a PV module are compared, to determine whether the simplest variation may be used for MPPT PV system modeling and analysis purposes. As part ot this determination, four different DC/DC converters are used in conjunction with these different PV models. This is to verify consistent behavior across the different PV models, as well as across the different converter topologies. Consistent results across the different PV models, will allow a simpler model to be used for simulation ana analysis. Consistent results with the different converters will verify that MPPT algorithms are converter independent. Next, MPPT algorithms are discussed. In particular,the differences between the perturb and observe, and the incremental conductance algorithms are explained and illustrated. A new MPPT algorithm is then proposed based on the deficiencies of the other algorithms. The proposed algorithm's parameters are optimized, and the results for different PV modules obtained. Realistic system losses are then considered, and their effect on the PV system is analyzed ; especially in regards to the MPPT algorithm. Finally, a PV system is implemented and the theoretical results, as well as the behavior of the newly proposed MPPT algorithm, are verified. / by Thomas Bennett. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Orientador: Júlio Borges de Souza / Banca: Luis Carlos Origa de Oliveira / Banca: Giuliano Pierre Estevam / Resumo: A transmissão de energia elétrica em corrente contínua em alta tensão é uma tecnologia utilizada para atender os requisitos cada vez mais rigorosos para a transmissão de energia elétrica, como por exemplo: adoção de fontes de energia localizadas em regiões remotas, a expansão das cargas industriais e urbanas, transmissão de energia elétrica por canais marítimos, etc. Esta tecnologia tem-se demonstrado comprovadamente eficaz e altamente confiável com a capacidade de modular a potência transmitida de forma rápida e precisa, apresentando características vantajosas do ponto de vista técnico e econômico. Porém, este tipo de tecnologia possui a desvantagem operacional de gerar conteúdo harmônico no sistema devido ao comportamento não linear dos conversores de potência utilizados para a conversão de corrente alternada em corrente contínua. Neste contexto, com o intuito de aplicar a metodologia de cálculo do conteúdo harmônico para o conversor de seis pulsos, o objetivo central do trabalho consiste no desenvolvimento de um simulador computacional para a determinação das harmônicas de correntes geradas pelas estruturas chaveadas dos conversores estáticos trifásicos, considerando condições não ideais de operação. O principal diferencial deste aplicativo computacional é proporcionar um ambiente visual interativo e intuitivo para a realização das simulações, apresentando de uma forma clara o objetiva os resultados dos parâmetros calculados pelo aplicativo e o resultado de cálculo do conteúdo harmônico de corrente gerado pelos conversores de potência. / Abstract: The power transmission in high voltage in direct current is a technology used to meet the increasingly stringent requirements for the transmission of electricity, such as: Adoption of energy sources located in remote areas, the expansion of industrial loads and urban, electrical transmission channels, marine, etc. This technology has demonstrated proven effective and highly reliable with the ability to model the power transmitted quickly and accurately, with advantageous features in terms of technical and economic. However, this type of technology has the disadvantage of generating harmonic content operating in the system due to nonlinear behavior of power converters used to convert alternating current into direct current. In this context, in order to apply the methodology of calculation of harmonic content for the six-pulse converter, the central objective of the work is to develop a software to determine the harmonic currents generated by switching structures of three-phase static converters, considering non-ideal operation. The main distinguishing feature of this application is to provide a computational interactive and intuitive visual environment to perform the simulations, showing a clear objective results of the parameters calculated by the application and the result of calculating the current harmonic content generated by power converters. / Mestre

Orientador: Flávio Alessandro Serrão Gonçalves / Banca: José Luiz Antunes de Almeida / Banca: Helmo Kelis Morales Paredes / Resumo: Este trabalho aborda o estudo de topologia de conversor de energia baseada no uso de configuração de rede de impedância denominada fonte-Y, com o objetivo de ser aplicado em sistemas de geração distribuída de energia, em redes de baixa tensão. Em sistemas de geração distribuída de energia usualmente se faz necessária a existência de um estágio elevador de tensão e um estágio inversor, ambos controlados para produzir tensão e/ou corrente senoidal com mesma frequência, amplitude e fase da rede elétrica. Nesse sentido, este trabalho propõe a aplicação do conversor fonte- Y entre a geração e a conexão com e rede elétrica, de forma que as ações de conversão relacionadas com a elevação (CC-CC) e inversão (CC-CA) sejam efetuadas de forma integrada por uma única estrutura, contribuindo com a possibilidade de melhoria no rendimento global devido à minimização de estágios de conversão em cascata. Inicialmente, é efetuado um levantamento bibliográfico relacionando as principais topologias de conversores utilizando redes de impedância com indutores acoplados, considerando os aspectos operacionais, arranjo de impedância e ganho estático idealizado, desprezando perdas entre tensão de entrada e tensão máxima de saída obtida. Segue-se o estudo da operação de conversor CCCC empregando rede de impedância do tipo Y, definição das equações que regem o comportamento no tempo das tensões e correntes nos capacitores e indutores. É feita uma avaliação comparativa do ganho estático de tensão obtido e... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This paper deals with the study of energy converter topology based on the use of impedance network configuration called Y-source, with the objective of being applied in photovoltaic energy cogeneration systems in low voltage grids. In photovoltaic energy generation systems, it is usually necessary to have a voltage boost stage and an inverter stage, both controlled to produce voltage and / or sine current with the same frequency, amplitude and phase of the power grid. In this sense, this work proposes the application of the Y-source converter between the photovoltaic generation and the connection with the electric grid, so that the conversion actions related to elevation (DC-DC) and inversion (DC-AC) in a way integrated by a single structure, contributing to the possibility of improvement in the overall yield due to the minimization of cascade conversion stages. Initially a bibliographical survey was performed relating the main inverter topologies using impedance networks with coupled inductors considering the operational aspects, impedance arrangement and ideal static gain between the input voltage and the maximum output obtained. ext, the study of the DC-DC converter operation using the Y-type impedance network, definition of the equations governing the time behavior of the voltages and currents in the capacitors and inductors, is presented. It is also done the comparative evaluation of the static voltage gain obtained and the stresses in the semiconductors according to the... (Complete abstract click electronic access below) / Mestre

It has become a case of great desire and, in some instances, a requirement to have systems in engineering be energy efficient, in addition to being effectively powerful. It is rare that there is a single technique that has the range to make this possible in a wide collection of areas in the field. The work done in this thesis exhibits how Pulse Width Modulation (PWM) bridges LEDs, plug in vehicles, fuel cells and batteries, all seemingly different sub categories of electrical engineering. It stems from an undergraduate directed independent study supervised by Dr. Zilouchian that encircled LEDs and electric vehicles and how they contribute to a smart electric grid. This thesis covers the design and development of a prototype board that test how PWM saves energy, prolongs lifespan and provides a host of customizable features in manufactured LED lights that are used in the marine industry. Additionally, the concept of charging batteries that provide power to electric vehicles was explored. It is stressed that consumers who are interested in electric vehicles are concerned about refueling and recharge times. It is natural that a competing product, such as the electric vehicle in a world dominated by internal combustion engines, will perform on par if not better than existing choices. Tests are conducted to investigate the methods of fast battery charging and the challenges this technique creates. Attention is also given to the development of a pulsed Proton Exchange Membrane (PEM) fuel cell, specifically to prove whether pulse modulation is more efficient in a hydrogen producing fuel cell as opposed to direct-driven voltage and current alternatives. / by Wayne W. Watt. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 200?. Mode of access: World Wide Web.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Thomas Raymond Zaloum. / M.S.