Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 127-140) Also available online.

Thesis (Ph.D.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Thesis (PhD (Electrical Engineering))--Cape Peninsula University of Technology, 2018. / Electrical energy can be easily used and converted to other forms of energy for various applications. Technological advancement increases the dependency on electricity to a great extent. Various internal and external factors are responsible for the bad quality of power in power systems. The performance of the system is greatly affected by the presence of harmonics, as well as voltage and frequency variations, which leads to the malfunctioning of the device and decline of power quality and supply at load side. The reactive power compensation is carried out for better power quality. The literature survey is done to find the best and efficient scheme for reactive power compensation and mitigation of various power quality problems. The devices which are used to measure various power quality factors are discussed. Various mitigating schemes are surveyed in order to compensate reactive power and to improve the power quality at the distribution end. The integration of the most widely used renewable energy, wind energy in the distribution system creates technical issues like stability of the grid, harmonic distortion, voltage regulation, active and reactive power compensation etc. which are restricted to IEC and IEEE standards. One of the topics this thesis addresses is regulation in the reactive power generated along with voltage regulation by using an effective power electronics device known as a STATCOM. The main power quality factors like overvoltage and voltage flickers are mitigated by establishing STATCOMs in small wind farms. The wind farms are equipped with three wind turbines. These three wind turbines found in the wind farm can be operated together or one after another with an introduced delay. A glitch in even a little piece of a power grid can result in loss of efficiency, income and at times even life. In this manner, it is basic to outline a system which can distinguish the faults of the power system and take a faster response to recover it back to required reactive power. Two devices STATCOM and D-STATCOM are used for this purpose in this thesis. The D-STATCOM circuit and operating principle are also discussed in thesis. Different topologies of D-STATCOM discussed with their benefits and shortcomings. The voltage, current and hybrid technologies of D-STATCOM are also discussed.

Orientador: Santos Junior Anesio dos / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T21:32:28Z (GMT). No. of bitstreams: 1 Bauab_GabrielaHelenaSergio_D.pdf: 3455899 bytes, checksum: 4ade2d30d8e9de4118018a2a17477849 (MD5) Previous issue date: 2009 / Resumo: Com a expansão dos sistemas elétricos e o aumento de carga, uma das dificuldades dos operadores é a manutenção do perfil de tensão do sistema. Neste trabalho é proposta uma estratégia de cálculo de variáveis descontrole, visando melhoria nos perfis de tensão das redes de transmissão e distribuição consideradas de forma integrada. Esta estratégia leva em consideração as especificidades dos componentes dos sistemas, como barras com controle de tensão, transformadores em fase com controle de tap das subestações de transmissão e das subestações de distribuição. Para a abordagem da regulação de tensão no sistema de transmissão é proposta a decomposição do problema. Esta é realizada levando em conta os efeitos que as variáveis de decisão provocam no sistema. A decisão sobre as variáveis de tensão das barras com controle é calculada por meio da resolução de um problema de otimização que envolve uma heurística para o tratamento das restrições sobre as injeções de potência reativa. Na seqüência, as decisões sobre os taps dos transformadores das subestações de transmissão também são tomadas com base em um problema de otimização simplificado. Para a integração das soluções dos sistemas de transmissão e distribuição é proposta uma heurística de ajuste de carga baseada em cálculo de fluxo de carga. O cálculo dos taps dos transformadores das subestações de distribuição é feito considerando a invariância d fluxo de potência ativa através das mesmas e possibilita a recuperação do perfil de tensão dos alimentadores. São apresentados resultados obtidos com sistemas de testes considerados em situações de operação normal e com perturbações, como contingências em circuitos de transmissão e alterações de carga. / Abstract: With the expansion of the electrical systems and the load increase, one of the difficulties of the operators is the maintenance of the voltage profile of the system. In this work, a control variable calculation esstrategy is proposal, aiming the improvement in the voltage profiles of the networks, considered transmission and distribution of integrated form. This strategy takes in consideration the specificities of components of the systems, such as voltage control, control of tap of transformers of transmission's subtation and distribution's substation. For the voltage regulation problem of transmission systems, a problem decomposition is proposal. This is based on the decomposition according to effect provoked for the same ones on the system. The decision on voltage variable of control bars is calculated by the resolution of a optimisation problem that involves a heuristic for the treatment of the reactive power injections restrictions. In the sequence, the decision on tap variable of transformers of transmission substation are also taken based on a simplified optimisation problem. For the Integration of the solutions of transmission and distribution systems is proposed a heuristic of load adjustment based on load flow calculation. The calculation of transformers' taps of the distribution substation is made considering the permanence of active power flow through the same ones and makes possible the recovery of the voltage profile of the feeders. Tests with transmission and distribution systems are presented considering normal operation and disturbances situations, as contingencies in the transmission circuits and load alteration. / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

A dissertation submitted in partial fulfillment of the Master's Diploma in Technology: Electrical Engineering (Heavy Current), M.L. Sultan Technikon, 1998. / With the ever increasing electrical demand on an electrical system, the quality of the supply will be tested more and more. And it is with this deteriorating quality that the topic of voltage dips and depressions has become a contentious issue amounts the industrial sector and supply authorities, hence the means to combat this issue in recent years. / M

This paper investigates the various parameters that effect voltage stability in sub-transmission power networks. The paper first looks at contributions from equipment: generators, transmission lines, transformers, capacitors, SVCs and STATCOMs. The paper also looks at the effects of loads on voltage stability. Power flow solutions, PV and VQ curves are covered. The study models an existing voltage problem i.e., a long, radial, 115 kV sub-transmission network that serves a 65 MW load. The network model is simulated with the following voltage instability countermeasures: adding a capacitor, adding an SVC, adding a STATCOM, tying to a neighboring transmission system, adding generation and bringing in a new 230 kV source. Then, using the WECC heavy-winter 2012 power flow base case and Siemens PTI software, VQ and PV curves are created for each solution. Finally, the curves are analyzed to determine the best solution.

Many settlements in Sub Saharan Africa (SSA) lack access to electricity which is a necessary resource for development. Given the geography and population patterns in the region, extending national grids is economically unviable for many of the un-electrified settlements. Meanwhile the region is endowed with renewable resources which can be exploited in off-grid mode for electricity generation. This thesis examines the importance of off-grid technologies for onward electrification in the SSA region. The exercise inspires an electricity planning problem that can be analytically specified but is computationally intensive and impractical for real sized problems. Heuristic methods must therefore be used. We develop two new heuristic solution methods which draw on standard algorithms i.e. lexicographic algorithm and genetic algorithm to solve the problem. The new solution methods together with two existing heuristic algorithms in the literature are applied to a case study of Ghana. We find that the electrification schemes yielded by all four solution methods/algorithms suggest off-grid technologies, especially solar, are important for onward electrification in SSA. Locations that were assigned off-grid technologies in the algorithms mentioned above are typically rural where livelihoods are based on small scale farming. Currently, adoption of renewable resource technologies is low in these locations. We therefore develop a dynamic stochastic farm household model to examine the extent to which market failures impact self-funded investment in solar panels by farmers in rural SSA. We find that credit restrictions and risk affect solar panel investment to varying degrees. Using simulations of the policy functions, we find that the expected investment cycle for a credit constrained household in a stochastic farm income environment is 30 years if investment in solar panels is irreversible. In a reversible investment scenario, the expected investment cycle is 5 years only. Reversibility is therefore a major determinant of solar panel adoption among poor farmers.

The importance of modern energy services to development is well established and it extends to deploying renewable energy for electricity to address current global challenges such as lack of access to electricity, poverty, environmental degradation and climate change. No doubt, electricity from renewable energy has negative impacts, but it also has benefits over other energy sources, particularly coal, oil and gas. These benefits have included that it is generally environmentally benign, it is vast, free, and supports standalone technologies. Thus avoiding costs associated with expanding the grid network. Hence, the idea that enhanced deployment of renewable energy for electricity can drive sustainable development in countries such as Nigeria, where amidst global concerns about climate change, modern access to electricity is low and energy supply for basic tasks such as cooking and cooling are from energy sources harnessed unsustainably or is itself not sustainable. In addition, other problems in Nigeria include high poverty and unemployment rates, environment degradation, destruction of biodiversity and natural ecosystem, corruption, lack of infrastructure, and dwindling government revenue profiles. Yet, the country has significant energy resources, renewables and non-renewables through which it can presumably meet all its energy needs. Nigeria enacted the Electric Power Sector Reform Act (EPSRA) in March 2005 to give statutory support to its National Electric Power Policy, (NEPP) which, inter alia, sought to promote expanded access to electricity, with minimum adverse impact on the environment. Given the benefits of renewable electricity, and the policy objectives on electricity development in Nigeria, this thesis examines the ability of Nigeria's Electric Power Sector Reform Act (EPSRA) 2005 to enhance the deployment of renewable energy for electricity and thereby foster sustainable development in the country.

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