A method for high performance output voltage control of a four-leg inverter based three-phase transformerless UPS is proposed. Voltage control loop is employed and the method employs stationary frame resonant filter controllers for the fundamental and harmonic frequency components. A capacitor current feedback loop provides active damping and enhances the output voltage dynamic performance. The controller design and implementation details are given. Linear and nonlinear loads for balanced and unbalanced load operating conditions are considered. The steadystate and dynamic performance of the UPS are investigated in detail. A scalar PWM method with implementation simplicity and high performance is proposed and implemented. The control and PWM methods are proven by means of theory, simulations, and experiments.

Voltage imbalance in low voltage (LV) networks is expected to deteriorate as low carbon technologies, e.g. electric vehicles (EVs) and heat pumps (HPs) are increasingly deployed. The new electrical demand attributable to EVs and HPs would increase the voltage magnitude variation, increasing the possibility of voltages moving outside the statutory LV magnitude limits. Moreover, the single-phase nature of EVs and HPs, which will be connected via a single-phase 'line & neutral' cable to a 3-phase four-wire LV mains cable buried beneath the street, further entangles this voltage management problem; the non-balanced voltage variations in the three phases boost the levels of voltage imbalance. Excessive voltage imbalance and magnitude variation need to be mitigated to limit their adverse effects on the electric network and connected plant. The voltage imbalance in LV networks is conventionally reduced by reinforcing the network, generally at a high cost. Some modern methods for voltage imbalance mitigation have been introduced in recent years. The power electronic converter based methods are inadequate due to the generation of harmonics, significant power losses and short lifetime. Besides, automatic supply phase selection and smart EV charging rely on an advanced smart communication system, which currently is not available. This project aims to develop alternative solutions that mitigate the voltage imbalance seen in LV networks. A voltage balancing method based on Scott transformer (ST) is proposed. This method does not generate harmonics and is independent of the smart communication system. Computer simulations demonstrated the proposed method is able to convert a non-balanced 3-phase voltage into a balanced 3-phase voltage at either a point on the LV feeder or a 3-phase load supply point with the predefined voltage magnitude. Besides, a physical voltage balancing system was created based on the proposed method and it was tested in an LV network in the laboratory. The test results show the balancing system is capable of maintaining a low level of voltage imbalance on the LV feeder by rapidly compensating for the voltage rises and sags caused by single-phase load variations. This voltage balancing method is a potential solution for the network utilities to accommodate the significant penetration of low carbon technologies without breaching the network voltage limits. The impact of EVs and HPs on the LV network voltages is investigated based on a Monte Carlo (MC) simulation platform, which comprises a statistical model of EV charging demand, profiles generators of residential and HP electrical demand, and a distribution network model. The MC simulation indicates the impact of EVs and HPs is related to their distribution; when more than 21EVs and 13HPs are non-evenly distributed on a 96-customer LV feeder, the voltage limits are likely to be violated. Moreover, the effectiveness of the ST based voltage balancing method and the demand response based TOU tariff, implemented either alone or together, in mitigating the impact of EVs and HPs is investigated based on the established MC simulation platform. The results indicate the ST based balancing method alone is able to completely mitigate the voltage limit violations regardless of the penetration levels of EVs and HPs. Moreover, using both of the two investigated methods further enhances the balancing effectiveness of the ST based voltage balancing method.

Le Système Électrique est soumis ces dernières années à plusieurs évolutions, depuis la dérégulationdu marché d'énergie à l'intégration de plus en plus importante de Générateurs Dispersés (GED). Ainsi,dans le cadre du concept de Smart Grid, les nouvelles technologies de l'information et de lacommunication (NTIC) offrent de nouvelles perspectives pour la gestion et l'exploitation des réseauxde distribution.Dans ce contexte, de nouveaux outils sont étudiés. Encore appelés Fonctions Avancéesd’Automatisation (FAA), le but principal de ces outils est d’utiliser tous les composants du réseau dedistribution de manière coordonnée en vue de les rendre plus actifs, flexibles et d’augmenter leurefficacité opérationnelle. Dans notre cas, nous avons étudié les fonctions associées à la reconfigurationen régime normal, du réglage de la tension et l’hybridation de ces deux derniers, tout en tenant comptede la présence des GED. En partant du comportement physique inhérent aux composants du réseau,plusieurs modèles ont été proposés. Certains sont tirés de la théorie des graphes et d’autres sur l’outilpuissant de la reformulation mathématique pour « convexifier » nos modèles. Cette modélisationadoptée répond à la fois à la nécessité de prendre en compte tous les moyens de réglages qui peuventêtre discrets (prises des transformateurs avec régleurs en charge ou des gradins de condensateurs),binaires (état de connectivité des composants) et continues (puissance réactive de la DG) et par lechoix des outils et des algorithmes d'optimisation mixte. En effet, la complexité de ces problèmes sonttelles que nous avons exploré à la fois des algorithmes méta-heuristiques (ACF : Algorithme desColonies de Fourmis) que déterministes (Décomposition de Benders Généralisée, Algorithme duBranch and Cut). / The Electric Power System is undergoing a lot of evolutions in recent years, including the energymarket deregulation and the increasing integration of Dispersed Generators (DG). Therefore, withinthe framework of Smart Grid concept, the New Information and Communication Technologies (NICT)provide new perspectives to manage and operate distribution networks.In this context, new tools, called Advanced Distribution Automation functions (ADA, are beingstudied). The main objective of these tools is to use all the distribution network components in acoordinated manner to make them more active and flexible, in addition to increasing their operationalefficiency. In our case, we studied the functions associated with the reconfiguration problem, thevoltage control problem and the hybridization of these two, while taking into account the presence ofthe DG. Based on the inherent components of network physical models, several models have beenproposed. Some are derived from the graph theory and others use powerful mathematicalreformulation to make our models convex. The adopted models answer to the necessity of taking intoaccount all regulation means, which can be discrete (On Load Tap-Changer and capacitor banks),binary (components connectivity such as lines or transformers) and continuous (DG reactive power ),and by the choice of tools and algorithms of mixed optimization. Indeed, the complexity of theseproblems is such that we have explored both algorithms: meta-heuristic (ACA, Ant Colony Algorithm)and deterministic (Generalized Benders Decomposition, Branch and Cut Algorithm).

Dans un contexte de développement des énergies renouvelables et des liaisons HVDC dans les systèmes électriques, les travaux présentés s’attachent au fonctionnement technique de tels systèmes. La génération éolienne, photovoltaïque et les liaisons HVDC sont interfacées par dispositifs d’électronique de puissance au réseau de transport électrique. Dès lors, serait-il envisageable d’alimenter la demande électrique uniquement via des sources électriques interfacées par des convertisseurs statiques ?Le pilotage du système électrique par électronique de puissance constitue un changement radical du fonctionnement dynamique des réseaux. La traditionnelle stratégie de commande « grid-following » des onduleurs a montré ses limites lorsque la pénétration de ces dispositifs devient importante. Elle doit être révisée au profit de stratégies dîtes « parallel grid-forming ».Dans cette thèse, les besoins fondamentaux du système électrique sont d’abord analysés pour définir les exigences de la stratégie « parallel grid-forming », ainsi que les défis associés. Selon ces spécifications, une méthode de synchronisation de sources « grid-forming » est ensuite proposée ainsi qu’un contrôle de tension, adapté aux limitations physiques des convertisseurs de tension PWM. La stabilité de la solution est discutée pour différentes configuration de réseau. Enfin, une stratégie de limitation du courant a été spécifiquement développée pour palier la sensibilité des VSC aux sur courants, lors d’évènements réseaux éprouvant. Les idées développées sur un convertisseur unique sont appliquées à petits réseaux afin d’extraire des interprétations physiques depuis des simulations temporelles / In the context of renewable energy and HVDC links development in power systems, the present work concerns the technical operations of such systems. As wind power, solar photovoltaics and HVDC links are interfaced to the transmission grid with power-electronics, can the system be operated in the extreme case where the load is fed only through static converters?Driving a power system only based on power electronic interfaced generation is a tremendous change of the power system paradigm that must be clearly understood by transmission grid operators. The traditional “grid-feeding” control strategy of inverters exhibits a stability limit when their proportion becomes too important. The inverter control strategy must be turned into a “parallel grid-forming” strategy.This thesis first analyses the power system needs, proposes the requirements for “parallel grid-forming” converters and describes the associated challenges. Accordingly, the thesis gives a method for designing a stable autonomous synchronization controls so that grid-forming sources can operate in parallel with a good level of reliability. Then, a method is proposed to design a voltage control for a grid-forming PWM source taking into account the limited dynamic of large converters. The robustness of the solution is discussed for different configuration of the grid topology. A current limiting strategy is presented to solve the current sensitivity issue of grid-forming converters, subject to different stressing events of the transmission grid. The ideas developed on a single converter are then applied on small grids with a limited number of converters to allow a physical interpretation on the simulation results.

The Electrical Functional Stimulation (EFS) allows the direct connection between man and machine through electrical signals. The last years growth in EFS is possible because of the new technological resources that make it feasible. Restoring someone s vision or hearing, even parcially, is one among several contribution that EFS may contribute to human s well-being. However the interface between the electrical circuits and the tissue is sensitive to several factors. Among several effects that may damage the tissue and electrode in EFS we can find those caused by the electrical stimuli, this may harm the application. This work presents contributions regarding electrical circuits topologies for safety stimuli in EFS. It is essential to ensure proper electrical charge balance and a small residual voltage on the tissue-electrode interface. For each of these problems one proposal is presented, both share circuit blocks. The blocks to control intensity and polarity of stimuli are designed to avoid the integration of high voltage devices. The current mode stimuli is generated using an ultra-low power charge redistribution Digital to Analog Converter (DAC) for stimulus intensity definition. This DAC architecture even simplifies the feedback mechanism that is obtained directly from measurement circuit. The technic that uses only low voltage devices to measure electrodes current is presented, it is suitable to implement the charge balance control in an integrated circuit. This measurement technique is insensitive to capacitors mismatch and to the current measurement absolute ratio. That control is possible through the a simplified feedback path that joins the controller and the measurement in an efficient way acting directly in the DAC. The proposed residual voltage control technique requires only passive elements to be added to the circuit, that suggest a lower power consumption. The charge redistribution DAC keeps residual voltage information stored, in order to compensate it in next stimulation cycles. The stimulation cycle polarity is explored, alternated cathodic and anodic-first cycles are used in order to reduce the charge imbalance and residual voltage. Both proposals are presented and validated with electrical simulation, known metrics are used and the performance is equivalent to state-of-art in literature. / A estimulação elétrica funcional(EFS) faz a interface direta entre o homem e a máquina, por meio de sinais elétricos. A viabilidade advinda de novas tecnologias justifica o seu crescimento nos últimos anos. Restaurar a visão ou a audição, mesmo que parcialmente, são duas das inúmeras contribuições que pode proporcionar para o bem estar do ser humano. No entanto, a interface entre o circuito elétrico e o tecido é sensível a diversos fatores. Entre os diversos fenômenos que podem ocasionar danos ao tecido e ao eletrodo na interface de EFS estão os causados pelo estímulo elétrico usado, e isso pode inviabilizar a aplicação. Neste sentido, este trabalho apresenta contribuições relacionadas à topologia de circuitos para segurança na geração do estímulo em EFS. O correto balanceamento de carga elétrica e a diminuição da tensão residual, na interface entre o tecido e o eletrodo, são indispensáveis. Uma técnica é propostas para a solução de cada um desses problemas, ambas compartilham blocos de circuito comuns. O controle da intensidade e da polaridade de estimulação são concebidos para evitar a necessidade de dispositivos de alta tensão. A geração de estímulos em modo corrente utiliza um Conversor Digital para Analógico (DAC) do tipo redistribuição de carga de ultra baixo consumo de energia para o controle da intensidade dos pulsos. Esse conversor ainda simplifica a realimentação, que é derivada diretamente do circuito de medição. Como solução para viabilizar a implementação em circuito integrado de controle do desbalanço de carga, uma técnica de medição usando somente dispositivos de baixa tensão é apresentada. Essa técnica é tolerante ao descasamento entre capacitores utilizados e à variação no ganho do circuito de medição de corrente. O controle é possível por meio de um laço de realimentação simplificado, que une medição e controle de forma eficiente e atua direto no DAC. A técnica proposta para controle da tensão residual nos eletrodos requer somente adição de elementos passivos ao circuito, sugerindo a redução do consumo de energia. O DAC tipo redistribuição de carga é usado para armazenar a informação da tensão residual e a compensação no ciclo seguinte. A fase dos ciclos de estimulaçãotambém é explorada, ciclos com fases alternadas são usados visando redução no desbalanço de carga e tensão residual. As duas propostas são apresentadas e validadas por meio da simulação elétrica, métricas conhecidas são utilizadas e o desempenho observado é equivalente ao estado da arte.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The subject of this work is to present a switched reluctance machine (SRM) driver capable to control the machine as a motor/generator, allowing the transition between the modes of operation while the machine is running. Six load voltage control strategies developed to be applied to a switched reluctance generator was performed, being that the strategies AV2, TBV, Hi and AMV was developed in this work. A SRM simulation able to represent the machine as a motor/generator was implemented and the results were presented. The load voltage strategies showed in this work was tested through simulations and the results indicate that the strategy called AV2 was the best one, providing a better utilization of the mechanical energy from the primary source. A prototype was assembled and the experimental results showed that the machine operating as a motor/generator operate properly and all the load voltage strategies developed to switched reluctance generator kept the voltage on the load near to the reference value confirming the functionality of the strategies. / Este trabalho tem como objetivo apresentar um acionamento capaz de controlar a máquina de relutância variável (MRV) como motor e como gerador, permitindo a transição de modos de operação com a máquina girando. Seis técnicas de controle de tensão na carga da máquina operando como gerador foram implementadas, sendo que as estratégias AV2, TBV, Hi e AMV foram desenvolvidas neste trabalho. Uma simulação da MRV capaz de representar a operação da máquina como motor/gerador foi desenvolvida e os resultados foram apresentados. As estratégias de controle de tensão na carga foram testadas através de simulação. Comparações entre as mesmas demonstraram que a estratégia AV2 é a que proporciona maior geração de energia elétrica, demonstrando a importância de se adicionar uma etapa de roda livre ao controle do GRV com malha fechada de tensão na carga. Um protótipo foi construído no laboratório utilizando DSP e resultados experimentais da máquina operando como motor/gerador, assim como resultados do GRV controlado pelas estratégias de controle de tensão na carga foram apresentados e discutidos. / Doutor em Ciências

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The search for solutions to the different power quality problems, in special the ones related to the voltage level compliance to the standard values has produced, up to now, an extensive range of commercial products using different techniques. Despite this recognition, the challenge for alternative strategies, presenting low cost and low maintenance properties, are very attractive and this subject is still motivating research worldwide. In this context, this dissertation is focused on the proposal of a voltage regulating device, here referred as CET (Electromagnetic Voltage Compensator), which presents an innovative design to obtain the process of voltage regulation. The main idea is based on the voltage injection, been as an additive or subtractive way, through a physical arrangement, presenting as a full electromagnetic power device. Aiming operative dynamic properties, the proposal in question, as far as their operational design concerns, is based on electronic switching and control device. The proposal outlined here will encounter emphasizes to the CET physical structure, the control unit composition and the evaluation of the electric complex performance under different voltage deviations occurrences. The studies are presented and then discussed, using the results provided by the computational simulation carried out in the time domain simulator ATP throughout its classical feature the MODELS language. / A busca por soluções para os distintos problemas da qualidade da energia elétrica, com destaque às variações das tensões de suprimento, conta, na atualidade, com uma extensa gama de produtos visando, sobretudo, a regulação dinâmica da tensão de suprimento. Não obstante tal reconhecimento, os desafios por estratégias alternativas por compensadores com propriedades operacionais e econômicas mais atrativas continuam motivando pesquisas em todo o mundo. Neste contexto, a presente dissertação encontra-se focada numa proposta de controle de um dispositivo regulador de tensão, aqui denominado por CET (Compensador Eletromagnético de Tensão), que se apresenta com uma concepção inovadora no que tange ao processo da regulação da tensão. A ideia central apoia-se na injeção série de reforços de tensão, aditiva ou subtrativa, através de um arranjo físico totalmente eletromagnético quanto às suas unidades de potência. Objetivando propriedades operativas dinâmicas, a proposta em pauta, no que tange a sua concepção operativa, fundamenta-se em chaveamentos eletrônicos controlados. À luz destes fatos, o trabalho vai de encontro a esta filosofia e ressalta a estrutura física do dispositivo, a composição da unidade de controle e avalia o desempenho do dispositivo sob condições associadas com a ocorrência de desvios de tensão. Quanto aos estudos feitos e discutidos, estes se encontram alicerçados em investigações computacionais conduzidas através da plataforma ATP e recursos oferecidos pela linguagem MODELS. / Mestre em Ciências

Este trabalho apresenta uma estratégia de controle coordenado para potência reativa e tensão terminal de um grupo moto gerador (GMG) para uso em um sistema de geração distribuída (GD). A partir da construção de uma superfície fuzzy, baseada no comportamento do erro e da derivada do erro de uma malha de controle, foi realizada a sintonia de controladores fuzzy PD+I para potências ativa e reativa e tensão terminal. O controlador coordenado fuzzy PD+I ajusta automaticamente a tensão nos terminais da máquina e a potência reativa fornecidas à rede de distribuição. A estratégia coordenada é dada através de um parâmetro que regula a malha de potência reativa a partir do erro de tensão terminal, priorizando o ajuste da tensão e ponderando a malha de controle de potência reativa. Para avaliar o desempenho do sistema de controle, a GD é conectada a uma rede de distribuição e submetida a eventos como entrada e saída de cargas locais. O conjunto de cargas locais é composto por um motor de indução, uma carga RLC e um retificador trifásico não controlado. Sete cenários foram simulados para avaliar a estratégia de controle em diferentes regimes de operação do GMG. Resultados para tensão terminal, fator de potência e fluxo de potências entre o sistema, as cargas e a rede, ilustram a eficiência da estratégia de controle apresentada. A estratégia de controle coordenado para potência reativa e tensão terminal se mostrou capaz de melhorar os índices de fator de potência controlando o fluxo de potência do barramento em que a GD estava conectada, sem prejudicar a tensão terminal do gerador, mantendo a GD em limites seguros de operação. / This work presents a coordinated control strategy to terminal voltage and reactive power for a diesel generation set used as a distributed gerenation system (DG). From desired control actions, a fuzzy surface was designed for fuzzy PD+I controllers. Fuzzy PD+I controllers automatically adjust the terminal voltage and the reactive power delivered to the grid. The coordinated control strategy weighs the control action for the reactive power through a variable parameter, prioritizing the terminal voltage adjustment. To illustrate the system control performance, the DG is connected to a grid dynamic model and the system is subjected to connection and disconnection of loads at the local bus. The local loads set was composed of an induction machine, a RLC load and an uncontrolled three-phase rectifier. Seven scenarios were simulated to evaluate the control strategy in different DG regime of operation. Results for terminal voltage, power factor and reactive power among the DG, the local loads and the grid, illustrates the control strategy efficiency improved the power factor by regulating the reactive power injected at the bus, maintaining the DG terminal voltage in safe operation limits.

Orientador: Carlos Alberto Favarin Murari / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-11T08:34:49Z (GMT). No. of bitstreams: 1 Canoas_AnaCarolinaGarcia_D.pdf: 790052 bytes, checksum: bdc65cd1e622b5ffa74f95691e03751e (MD5) Previous issue date: 2008 / Resumo: Devido ao crescente aumento da demanda de energia elétrica e ao retardo de investimento na expansão dos sistemas e energia elétrica (SEE), a operação destes sistemas está cada vez mais próxima de seus limites operacionais, contribuindo para maior complexidade dos SEE. Neste sentido, para satisfazer as rígidas condições de operação, um gerenciamento do perfil de tensão e fluxo de potência tem se tornado cada vez mais importante para as concessionárias, de modo a aumentar a segurança operacional dos sistemas e otimizar o uso de fontes de potência reativa, visando suprir aos consumidores energia dentro de determinados padrões de qualidade e confiabilidade. o objetivo principal desta pesquisa é o desenvolvimento de metodologias com o objetivo de monitorar o perfil de tensão, mantendo-o dentro dos limites operativos, visando não perder a qualidade de fornecimento de energia elétrica. O primeiro método trata-se de uma ferramenta de auxílio à tomada de decisão dos operadores nos centros de controle, baseada em um conjunto de regras nebulosas, o qual é a base do sistema de inferência fuzzy (ou nebulosa) que por sua vez se fundamenta na teoria de conjuntos nebulosos. Considerando que o problema de controle de tensão e de potência reativa apresenta características de natureza não-linear e que envolve variáveis de controle contínuas e discretas, foi desenvolvido um segundo método, o qual utiliza lógica nebulosa em conjunto com a técnica de otimização particle swarm. Este método mostra a possibilidade de incorporar lógica nebulosa em algoritmos baseados em busca, possibilitando a redução das perdas do sistema, satisfazendo as restrições de operação, e garantindo que o perfil de tensão mantenha-se dentro dos limites operativos com uma melhor utilização das fontes de potência reativa / Abstract: Due to the growing electrical power demand and the lag of transmission system infrastruc ture, the operation of transmission systems approaches to its limits and increases the complexity of the system operation. ln this context, in order to satisfy the more rigid operating conditions, managing voltage profile and power flow in a more effective way becomes very important to the power companies that have the aim of enhancing the operating conditions and optimiz ing reactive power sources to provide the consumers with an adequate quality and reliability standards. The main objective of this research work is the development of methodologies for monitoring the volt age profile in order to keep it within operating limits and preserving the quality of the energy being served. The first method consists of a tool for helping decision making by system operators in control centres. This method is based on a set of fuzzy rules, which are the base of a fuzzy inference system. Considering that the voltage and reactive power control present nonlinear characteristics and mixed continuous and discrete variables, a hybrid meta-heuristic method based on fuzzy system and particle swarm optimization has been developed. The fuzzy system has been incorporated into swarm intelligence to provide operational point that allows reduction of system losses while satisfies the operationallimits, volt age constraints and the best utilisation of reactive power / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

L’intégration massive de la production d’énergie éolienne intermittente au niveau des réseaux électriques pose un problème de stabilité du système électrique. En effet les caractéristiques sont très différentes de celles de sources conventionnelles maîtrisées par les gestionnaires de réseau. Par conséquent, l’injection de cette énergie induit de nouveaux challenges pour les gestionnaires de réseaux électriques. De plus, les conditions de raccordement évoluent et tendent à ce que toutes les sources participent aux services rendus aux systèmes électriques. Les travaux de cette thèse sont focalisés sur la proposition d’une nouvelle stratégie de commande non-linéaire basée sur la commande par « platitude à une boucle » d’un système de conversion d’énergie éolienne. Cette stratégie de contrôle vise la gestion des interactions au point de connexion par la génération et le suivi de trajectoires de références. De par le fait que toutes les variables du système sont liées à la « sortie plate » de ce système, cette commande procure une rapidité de réponse et une bonne maitrise des régimes transitoires. La mise en œuvre de cette nouvelle stratégie de contrôle pour la constitution d’un parc éolien offshore, capable de satisfaire différentes conditions de raccordement a été simulée avec succès. Plus particulièrement, l’évaluation de l’impact de différents défauts du réseau sur les services proposés (Régulation de fréquence et de tension, la tenue aux creux de tension.) a été réalisée. / The massive integration of intermittent production of wind energy in electrical networks creates an electrical system stability problem. Indeed, its characteristics are very different from those of conventional sources controlled by Grid managers. Therefore, the injection of this energy makes new challenges for power Grid operators. Moreover, the connection conditions are evolving and go towards the situations that all different sources participate into services of electrical systems. This thesis proposes a new nonlinear control strategy based on a « one loop flatness control » of a wind energy conversion system. This control strategy has aim of energy interactions management at the connection point through generation and tracking of reference trajectories. As all system variables are functions of the « flat output » of the system, this control provides fast response and good control in transient state. The application of this new control strategy into an offshore wind farm which is able to satisfy different connection conditions was simulated successfully. Specifically, effects of various grid faults on the proposed ancillary services (frequency and voltage regulation, and low-voltage ride through capabilities) were performed.