M. Tech. Engineering: Electrical. / Discussing the developing an entirely software based synchrophasor platform for transient stability analysis of a multi-machine system by exploiting the possibility of distributing a precise time reference by means of communication networks and an open source software-only Precision Time Protocol (PTP) to synchronise PMUs and evaluates the precision of this synchronisation in the event of faults in a power system.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: This work investigated the influence of photo-voltaic generators on the voltage control of distribution feeders and the methods that can be used to increase the maximum penetration levels of these feeders. Initially, a brief overview of the reasons why it is necessary to increase the generation penetration levels on distribution feeders was provided. A review of various issues associated with connecting generation to the distribution network; methods and technologies that can be used to increase penetration levels; and ways to improve voltage regulation on MV feeders was given. The grid code for renewable power plants and the voltage apportionment standard were reviewed to determine what limits penetration levels and what can be done to increase them. The operation and control of a typical distribution network, without any connected generation, was initially investigated. A control strategy was implemented that provided suitable voltage regulation on the feeder during both high and low load. The influence of connecting generation to this typical distribution network, without making any modifications to the control of the feeder, was investigated. Base penetration levels, for various generation connection cases, were found. It was shown that the penetration is limited by the rapid voltage change or voltage rise. The base penetration levels were compared to the optimal amount of generation that provides the lowest losses. It was shown that the penetration needs to be increased by between 100% and 200% for the feeder’s losses to be minimised. Voltage regulator and capacitor control was influenced by the generation and they could not function as expected. It was shown that flicker will not be an issue, even with penetration limits well above the current allowable limits. Various methods that can be used to increase the amount of generation that is connected to the typical network were investigated. On-load tap changer setpoint reduction, reactive power control and electronic voltage regulators are some of the methods or technologies that can be used to increase penetration levels. It was shown that each of the technologies can assist, depending on the circumstance, in increasing penetration. The individual modifications can increase penetration up to 100% at the cost of increased tap changes and in some cases losses. Two proposed control strategies were assessed, that combine the investigated technologies. The results showed that it is possible to increase penetration levels by 50-80%, while improving power quality and reducing losses when compared to the base generation connection case. / AFRIKAANSE OPSOMMING: Hierdie werk ondersoek die invloed van die foto- voltaïes kragopwekkers op die spanning beheer van die verspreiding voerder asook die metodes wat gebruik kan word om die maksimum penetrasie vlakke van hierdie voerders te verhoog. Aanvanklik is 'n kort oorsig van die redes waarom dit nodig is om die opwekking penetrasie vlakke op die verspreiding voerders, te verhoog voorsien . Eerstens word 'n hersiening van verskeie kwessies wat verband hou met die koppeling van generasie na die verspreidingsnetwerk gegee. Tweedens word metodes en tegnologie wat gebruik kan word om penetrasie te verhoog gegee en laastens word maniere om spanning regulasie op medium spanning voerders te verbeter, gegee. Die rooster kode "grid code => probeer liewer netwerk regulasies" vir hernubare krag aanlegte en die spanning toedeling standaard is hersien om te bepaal wat beperk die penetrasie vlakke en wat gedoen kan word om dit te verhoog. Die werking en beheer van 'n tipiese verspreiding netwerk, sonder enige verbonde generasie, is aanvanklik ondersoek. 'n Beheer-strategie is toe geïmplementeer wat geskikte spanning regulasie op die voerder tydens beide hoë en lae belasting verskaf. Die invloed van die koppeling van opwekking tot hierdie tipiese verspreiding netwerk, sonder om enige veranderinge aan die beheer van die voerder, is ondersoek. Basis penetrasie vlakke, vir verskeie generasie verband gevalle, is gevind. Daar is bewys dat die penetrasie word beperk deur die vinnige spanning verandering of spanning styging. Die basis penetrasie vlakke word vergelyking met die optimale aantal generasie wat die laagste verliese bied. Daar is bewys dat die penetrasie moet met tussen 100% en 200% verhoog word sodat die voerder se verliese beperk kan word. Die spanning reguleerder en kapasitor beheer is beïnvloed deur die opwekking en hulle kon nie reageer soos verwag nie. Daar is getoon dat flikker nie 'n probleem sal wees nie; selfs al is die penetrasie vlakke ver bo die huidige toelaatbare grense. Verskillende metodes wat gebruik kan word om die aantal generasie wat gekoppel is aan die tipiese netwerk te verhoog is ondersoek. Aan-las tap wisselaar vermindering, reaktiewe krag beheer en elektroniese spanning reguleerders is 'n paar van die tegnieke wat gebruik kan word om penetrasie te verhoog. Daar is bewys dat elkeen van die tegnologieë kan help, afhangende van die omstandighede, vir toenemende penetrasie. Die individuele veranderinge kan penetrasie verhoog tot 100% by die koste van 'n verhoogde tap veranderinge en in sommige gevalle verliese. Twee voorgestelde beheer strategieë is beoordeel, wat die ondersoek tegnologie kombineer. Die resultate het getoon dat dit moontlik is om penetrasie te verhoog met 50% tot 80%, terwyl die verbetering van gehalte en die vermindering van krag verliese in vergelyking met die basis generasie verband hou.

The terminations and the joints are the basic accessories of the power cables. Power cables require electrical stress control when terminated. Since there are different types of terminations, the analysis should be done to choose the proper method for electric field control problem at the terminations. Throughout this study two different types of termination methods are investigated by using the finite element analysis program (ANSYS): Stress Controlled Termination Model with Deflector and Stress Control Tube (SCT). The results are compared with those obtained for a cable without stress control model termination. The numerical calculations are also compared with the measurements obtained by an experimental model: the electrolytic tank model.

Este trabalho apresenta o controle de potência em um gerador de indução duplamente alimentado (GIDA) utilizado em uma micro turbina eólica, visando o controle de potência ativa e reativa para minimizar as variações de tensão em redes rurais. Com a inserção destas fontes renováveis de energia no sistema de distribuição em baixa tensão, é fundamental analisar os impactos na qualidade de energia no ponto de conexão (PC) e implementar o controle adequado para atender os requisitos técnicos dos procedimentos de distribuição estabelecidos por norma. Uma equação é apresentada para relacionar a variação de tensão com a potência injetada em uma rede de distribuição em baixa tensão. Uma rede rural típica é emulada nesse trabalho para analisar este impacto na variação de tensão em áreas remotas. O sistema utiliza malhas de controle tradicionais PI para as correntes retóricas e malha de potência ativa e reativa, e as referências são então definidas para auxiliar a evitar uma violação da banda de variação de tensão permitida por norma. Devido ao fato de que a inserção de potência ativa em redes rurais é o principal fator de variação da tensão no PC, resultados experimentais são apresentados para validar a teoria desenvolvida e comprovar a eficácia do sistema projetado. / This work presents the power control in a double fed induction generator (DFIG) used in a wind turbine, aiming the control of active and reactive power to minimize the voltage variations in rural networks. With the insertion of these renewable energy sources in the low voltage distribution system, it is fundamental to analyze the impacts on the quality of energy at the point of connection (PC) and to implement adequate control to attend the technical requirements of the distribution procedures established by standard. An equation is presented to relate the voltage variation to the injected power in a low voltage distribution network. A typical rural network is emulated in this work to analyze this impact on the voltage variation in remote areas. The system uses traditional PI control meshes for rotor currents and active and reactive power mesh, and the references are then set to help prevent a violation of the allowable voltage variation band as per standard. Due to the fact that the insertion of active power in rural networks is the main factor of variation of the voltage in the PC, experimental results are presented to validate the developed theory and to prove the efficiency of the designed system.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta o projeto e análise de uma estratégia de controle para inversores monofásicos conectados a rede de distribuição de energia elétrica. A estratégia é projetada com o objetivo de atender os limites harmônicos do padrão IEEE 1547.2-2008 e ao mesmo tempo suportar uma faixa de variação dos parâmetros da rede elétrica, como frequência, resistência e indutância. Neste sentido, a estratégia envolve um conjunto de técnicas como: um sincronizador de fase e frequência; controladores de corrente e potência, com rejeição de harmônicos; amortecimento ativo; estimador de corrente; filtro digitais; entre outras. Para essa estratégia de controle, foi escolhido o controlador proporcional ressonante (PR) e um sincronizador de fase e frequência de segunda ordem (MSOGI-FLL) com capacidade de suportar variações usuais de frequência. Ainda, um filtro de conexão passivo do tipo LCL-LC e um algoritmo de rejeição o de harmônicos (HC) são utilizados para atender os limites de conteúdo harmônico. Para aumentar a margem de estabilidade do sistema é utilizado uma técnica de amortecimento ativo. Para implementação dessa técnica de amortecimento ativo é proposto um novo estimador da corrente do capacitor do filtro de conexão de fácil implementação e que suporta variações da impedância da rede elétrica, entre redes fracas e redes fortes. Esse trabalho também contribui com o projeto dos ganhos do controlador PR com amortecimento ativo apresentado a estabilidade em uma ampla de faixa de parâmetros da rede elétrica, o que pode caracterizar desde uma rede fraca até uma rede forte. Para validação experimental da estratégia proposta foi construído um protótipo de um inversor monofásico de 1 kW, com características similares de produtos comerciais, como custo e dimensões reduzidas. O funcionamento da estratégia de controle proposta e do conversor de potência foi verificado por meio de resultados experimentais. Os vários resultados apresentados no trabalho corroboram o bom desempenho do sistema projetado e analisado em simulações computacionais. A distorção harmônica total (DHT) da forma de onda de corrente ´e inferior a 2,3% em todos os casos analisados, atendendo o padrão IEEE 1547.2-2008. / This work presents the design and analysis of a control strategy for single-phase inverters connected to the electric power distribution network. The strategy is designed to comply with the harmonic limits of the IEEE 1547.2-2008 standard and at the same time support a range of grid parameters variation such as frequency, resistance and inductance. In this sense, the strategy involves a set of techniques such as: a phase and frequency syn- chronizer; current and power controllers with harmonic compensation; active damping; current estimator; digital filter; among others. For this control strategy, a resonant pro- portional controller (PR) and a second-order phase-frequency synchronizer (MSOGI-FLL) with the capacity to withstand usual frequency variations were chosen. Furthermore, a LCL-LC passive connection filter and a harmonic compensation algorithm (HC) are used to comply with the harmonic limits. To increase the stability of the system an active damping technique is used. To implement this active damping technique, it is proposed a new estimator of the filter capacitor current with an easy implementation and support for electrical grid impedance variations between weak grids and strong grids. This work contributes to the PR controller with active damping gains design seeking stability in a wide range of parameters of the electrical grid that characterizes from a weak grid to a strong grid. For experimental validation of the proposed strategy a prototype of a 1 kW single-phase inverter was built, with characteristics of commercial products, such as cost and dimensions restrictions. The operation of the power converter and the proposed control strategy was verified through experimental results. The various results presented in the paper corroborate the good performance of the system analyzed in computational simulations. The total harmonic distortion (DHT) of the current waveform is lower than % in all analyzed cases, meeting the IEEE 1547.2-2008 standard.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho é proposto e apresentado um medidor inteligente de energia elétrica considerando os métodos de medição classe S especificados no PRODIST e na norma IEC 61000-4-30. O medidor proposto calcula os valores eficazes de tensão e corrente, as potências aparente, ativa e reativa, o fator de potência, a frequência, as distorções harmônicas e detecta a ocorrência de variações de tensão de curta duração. Como principais contribuições deste trabalho, pode-se citar a avaliação de métodos existentes e a proposta de um novo método para detectar a origem de distúrbios em relação à localização do medidor. Propôs-se também uma interface gráfica que permite o monitoramento dos parâmetros elétricos e de qualidade de energia, e ainda possibilita a interação do consumidor para a obtenção o de informações detalhadas sobre o estado da rede. O medidor pode ser utilizado como um registrador de dados e permite o acesso à sua interface gráfica por meio da utilização da porta de comunicação ethernet. Para a validação inicial, realizaram-se simulações computacionais, a partir de um modelo de consumidor residencial, em diferentes cenários de operação. Na etapa de validação experimental, foi utilizada uma fonte de geração de sinais e realizaram se testes com o medidor conectado à rede de distribuição de baixa tensão. A partir destas etapas foi possível verificar o funcionamento da interface gráfica e validar o funcionamento do medidor inteligente proposto. / In this study, a smart meter is presented, which considers the class S measurement methods specified at IEC 61000-4-30 standard and PRODIST. The proposed smart meter calculates RMS voltage and current values, active, reactive and apparent powers, power factor, frequency, harmonic distortions and detects short duration voltage variations. As main contributions of this study, it can be mentioned the evaluation of existing methods and the proposal of a new method to determine on which side of a recording device a disturbance originates. It’s also developed a graphical interface that allows the monitoring of electrical and power quality parameters and it enables consumer interaction to get detailed power grid information. The smart meter can also be used as a data logger and it allows access to its graphical interface through ethernet communication port. For the initial validation, computer simulations were performed through a residential consumer model in different operating scenarios. The experimental validation tests were carried out using an AC power source and the smart meter has been connected to low-voltage distribution grid. Through these steps, it was possible to verify the interface operation and to validate the proposed smart meter operation.

Orientadores: Paulo Morelato França, Celso Cavelucci / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-23T09:06:37Z (GMT). No. of bitstreams: 1 Almeida_Joselainede_M.pdf: 6148218 bytes, checksum: 1ef511889e4a35f380f54407917e0268 (MD5) Previous issue date: 2013 / Resumo: As concessionárias de energia elétrica devem projetar adequadamente as redes de distribuição, incluindo: definição da localização e capacidade dos transformadores; definição dos traçados de rede primária (15 kV) e de rede secundária (127/220V); e definição e instalação de elementos construtivos, tais como postes, estruturas primárias, estruturas secundárias, transformadores. Projetar estas redes é uma tarefa complexa e demorada que exige amplo conhecimento das normas técnicas e experiência por parte dos projetistas. Neste trabalho é proposto um Sistema de Apoio à Decisão (SAD) para projetos de redes aéreas de distribuição de energia elétrica, englobando as diversas etapas de especificação do projeto. Também é detalhado um sistema especialista para definição dos elementos construtivos (módulo de projeto de execução da rede). Os ganhos potenciais desta abordagem são avaliados em estudos de caso de diversos tipos de projetos. Os principais benefícios da utilização do SAD são: diminuição da dispersão das soluções de projeto; diminuição dos erros; soluções de menor custo e redução no tempo de elaboração dos projetos / Abstract: Electric power companies must design distribution networks, which is a task that includes: the determination of the capacity and position of distribution transformers; the routing of primary feeders (15 kV) and secondary distribution circuits (127/220V); and the selection and installation of constructive elements such as poles, primary structures, secondary structures, street transformers. The design of these networks is a complex and demanding task that requires a great knowledge about technical norms and experience from the network designers. This thesis presents a Decision Support System (DSS) to assist designers to elaborate the several steps of the distribution networks projects specification. An expert system that defines the constructive elements (Network Execution Project module) is also proposed. The advantages of this approach are evaluated through case studies based on different types of projects. The benefits of this DSS are the less variation of project solutions and the reduction of errors, solution costs and completion time / Mestrado / Automação / Mestra em Engenharia Elétrica

In this work passive piezoelectric devices for vibration damping are studied. It is developed the basic idea of synthesizing electrical wave guides to obtain an optimal electro-mechanical energy exchange and therefore to dissipate the mechanical vibrational energy in the electric form. Modular PiezoElectroMechanical (PEM) structures are constituted by continuous elastic beams (or bars) coupled, by means of an array of PZT transducers, to lumped dissipative electric networks. Both refined and homogenized models of those periodic systems are derived by an energetic approach based on the principle of virtual powers. Weak and strong formulation of the dynamical problem are presented having in mind future studies involving the determination of numerical solutions. In this framework the effectiveness of the proposed devices for the suppression of mechanical vibrations is investigated by a wave approach, considering both the extensional and flexural oscillations. The optimal values of the electric parameters for a fixed network topology are derived analytically by a pole placement technique. Their sensitivities on the dimensions of the basic cell of the periodic system and on the design frequency are studied. Moreover the dependence of damping performances on the frequency is analyzed. Comparing the performances of different network topological configurations, the advantages of controlling a mechanical structure with an electric analog are shown. As a consequence of those results, new interconnections of PZT transducers are proposed. An experimental setup for the validation of the analytical and numerical results is proposed and tested. A classical experience on resonant shunted PZT is reproduced. Future experimental work is programmed.

La calidad de energía eléctrica incluye la calidad del suministro y la calidad de la atención al cliente. La calidad del suministro a su vez se considera que la conforman dos partes, la forma de onda y la continuidad. En esta tesis se aborda la continuidad del suministro a través de la localización de faltas. Este problema se encuentra relativamente resuelto en los sistemas de transmisión, donde por las características homogéneas de la línea, la medición en ambos terminales y la disponibilidad de diversos equipos, se puede localizar el sitio de falta con una precisión relativamente alta. En sistemas de distribución, sin embargo, la localización de faltas es un problema complejo y aún no resuelto. La complejidad es debida principalmente a la presencia de conductores no homogéneos, cargas intermedias, derivaciones laterales y desbalances en el sistema y la carga. Además, normalmente, en estos sistemas sólo se cuenta con medidas en la subestación, y un modelo simplificado del circuito. Los principales esfuerzos en la localización han estado orientados al desarrollo de métodos que utilicen el fundamental de la tensión y de la corriente en la subestación, para estimar la reactancia hasta la falta. Como la obtención de la reactancia permite cuantificar la distancia al sitio de falta a partir del uso del modelo, el Método se considera Basado en el Modelo (MBM). Sin embargo, algunas de sus desventajas están asociadas a la necesidad de un buen modelo del sistema y a la posibilidad de localizar varios sitios donde puede haber ocurrido la falta, esto es, se puede presentar múltiple estimación del sitio de falta.Como aporte, en esta tesis se presenta un análisis y prueba comparativa entre varios de los MBM frecuentemente referenciados. Adicionalmente se complementa la solución con métodos que utilizan otro tipo de información, como la obtenida de las bases históricas de faltas con registros de tensión y corriente medidos en la subestación (no se limita solamente al fundamental). Como herramienta de extracción de información de estos registros, se utilizan y prueban dos técnicas de clasificación (LAMDA y SVM). Éstas relacionan las características obtenidas de la señal, con la zona bajo falta y se denominan en este documento como Métodos de Clasificación Basados en el Conocimiento (MCBC). La información que usan los MCBC se obtiene de los registros de tensión y de corriente medidos en la subestación de distribución, antes, durante y después de la falta. Los registros se procesan para obtener los siguientes descriptores: a) la magnitud de la variación de tensión ( dV ), b) la variación de la magnitud de corriente ( dI ), c) la variación de la potencia ( dS ), d) la reactancia de falta ( Xf ), e) la frecuencia del transitorio ( f ), y f) el valor propio máximo de la matriz de correlación de corrientes (Sv), cada uno de los cuales ha sido seleccionado por facilitar la localización de la falta. A partir de estos descriptores, se proponen diferentes conjuntos de entrenamiento y validación de los MCBC, y mediante una metodología que muestra la posibilidad de hallar relaciones entre estos conjuntos y las zonas en las cuales se presenta la falta, se seleccionan los de mejor comportamiento.Los resultados de aplicación, demuestran que con la combinación de los MCBC con los MBM, se puede reducir el problema de la múltiple estimación del sitio de falta. El MCBC determina la zona de falta, mientras que el MBM encuentra la distancia desde el punto de medida hasta la falta, la integración en un esquema híbrido toma las mejores características de cada método. En este documento, lo que se conoce como híbrido es la combinación de los MBM y los MCBC, de una forma complementaria. Finalmente y para comprobar los aportes de esta tesis, se propone y prueba un esquema de integración híbrida para localización de faltas en dos sistemas de distribución diferentes. Tanto los métodos que usan los parámetros del sistema y se fundamentan en la estimación de la impedancia (MBM), como aquellos que usan como información los descriptores y se fundamentan en técnicas de clasificación (MCBC), muestran su validez para resolver el problema de localización de faltas. Ambas metodologías propuestas tienen ventajas y desventajas, pero según la teoría de integración de métodos presentada, se alcanza una alta complementariedad, que permite la formulación de híbridos que mejoran los resultados, reduciendo o evitando el problema de la múltiple estimación de la falta. / Power quality includes the supply and customer support quality. The supply quality considers two aspects, the wave shape and continuity. In this thesis the fault location problem, topic related with supply continuity is considered. Fault location is a relatively solved problem in power transmission systems, due to the homogeneous characteristics of the power line, measurements in both terminals and also the availability equipment such as fault locators normally included in distance relays. However, in power distribution systems the fault location is a complex problem which remains unsolved. The complexity is mainly because the presence of laterals, load taps, non homogeneous conductors, unbalances in the system and load. In addition, these power systems only have measurements at the substation and a simplified model of the power network. The main efforts to solve this problem have been oriented to the development of impedance based methods. Because of the reactance estimation makes possible the estimation of the distance to the faulted node by using the circuit model, those methods are considered as Model Based Methods (MBM). However the main drawbacks are related to the requirement of a good system model and to the possibility of multiple estimation of the location of the fault due to the three-shape of such networks. As a result, in this thesis an analysis and a comparative test between several MBM frequently cited is presented. In addition, the solution of the fault location is complemented by using methods which use more than the rms values of current and voltage obtained from fault databases. As tool to relate this information with the fault location, two classification techniques are used and tested (LAMDA and SVM). These relate the voltage and current characteristics to the faulted zone and are denoted in this document as Classification Methods Based on the Knowledge (CMBK).The information used by CMBK is obtained from current and voltage fault registers measured at the distribution substation, before, during and after the fault. These registers are pre-processed to obtain the following characteristics or descriptors: a) The magnitude of the voltage variation between the steady states of fault and pre-fault ( dV ), b) the magnitude of the current variation between the steady states of fault and pre-fault ( dI ), c) the magnitude of the apparent power variation between the steady states of fault and pre-fault ( dS ), d) the magnitude of the reactance as seen from the substation ( Xf ), e) the frequency of the transient caused by the fault ( f ), and f) the maximum eigenvalue of the correlation matrix of the currents ( Sv ). By using these descriptors, several training and validation sets were used with CMBK and by means of a proposed methodology it is shown how to relate these sets with the faulted zone and also to select those which offer the best performances.The application results demonstrate how by combining the MBM with the CMBK it is possible to reduce the multiple estimation of the fault location. The CMBK is used to determine the faulted zone while the MBM finds the distance from the measurement point to the faulted node. Thus the integration in a hybrid approach uses the best characteristics of each method. In this document, the term hybrid is used to describe the complementary combination of MBM and CMBK. Finally and aimed to compare the thesis results, an integration hybrid scheme to fault location is proposed and tested in two different power distribution systems. Both, methods which use the system parameters and are based on the impedance estimation (MBM), and those which use the information represented by the signal descriptors and are based in classification techniques (CMBK) have shown the capability to solve the problem of fault location. The two proposed methodologies have advantages and drawbacks, but according to the integration theory presented, high complementarity has been reached. This makes possible the development of a hybrid approach used to avoid or reduces the multiple estimation of the fault location.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009 / The purpose of this project is to develop methods for distribution network power quality' variations monitoring. Power quality (PO) has become a significant issue for both power suppliers and customers. There have been important changes in power system regarding to power quality requirements. "Power quality" is the combination at voltage quality and current quality. The main research problem of the project is to investigate the power quality of a distribution network by selection of proper measurement, applying and developing the existing classic and modern signal conditioning methods for power disturbance's parameters extracting and monitoring. The research objectives are: To study the standard lEC 61000-4-30 requirements. to investigate the common couplings in the distribution network. To identity the points for measurement, to develop MySQL database for the data from the measurement and to develop MATLAB software tor simulation of the network To develop methods based on Fourier transforms for estimation of the parameters of the disturbances. To develop software for the methods implementation, The influence of different loads on power quality disturbances are considered in the distribution network. Points on the network and meters according to the lEC power quality standards are investigated and applied for the CPUT Bellville campus distribution network. The implementation of the power quality monitoring for the CPUT Bellville campus helps the quality of power supply to be improved and the used power to be reduced. MATLAB programs to communicate with the database and calculate the disturbances and power quality parameters are developed.