Dissertations / Theses on the topic 'Bidirectional power conversion'

碩士<br>國立中山大學<br>電機工程學系研究所<br>103<br>Two circuit designs are proposed for power detectors used in biomedical sensing systems. The first topic is a wide range high conversion gain low-power power detector, and the other one is a bidirectional power detector. The wide range high conversion gain low-power power detector is composed of an amplitude-to-voltage converter (AVC), a peak or valley detector, and a bandgap bias. Two RMS power detectors consist of an AVC to boost conversion gain and enlarge input frequency range. The AVC converts the input power into a DC voltage proportionally. Peak or valley detector will therefore detect the maximum or minimum voltage value, respectively, where the resonant frequency of the input signal is associated with. The proposed detector reduces power consumption by using a power switch to power-gate the peak or valley detector. The proposed power detector is realized on silicon using a TSMC 0.25 μm CMOS process. Measurement results justify that the conversion gain is 166 mV/dB, the input frequency range is from 500 Hz to 2.5 GHz and the power saving is up to 39.6 %. The second topic is a wide range high conversion gain bidirectional power detector. To make power detector more robust such that it will not be constrained by the type of sensors, the proposed detector consists of an AVC, a peak and valley detector, a decider and a bandgap bias. The AVC is also composed of two RMS power detectors carrying out the conversion between different amplitude voltage levels and the corresponding DC voltages. Next to the AVC circuit, the decider will determine the direction of the AVC output signal to change the mode of peak or valley detection. This design is carried out on silicon using a UMC 0.18 μm CMOS process. Measurement result shows that the conversion gain is 76 mV/dB and the input frequency range is from 500 kHz to 20 GHz.

碩士<br>國立臺灣科技大學<br>電機工程系<br>106<br>This thesis presents the design of grid-connected bidirectional three-phase six-arm power converters, which consists of three single-phase, two-arm, full-bridge converters using unipolar sinusoidal pulse-width modulation control strategy for each phase. Grid voltage angle is detected by phase-lock loop software to raise power factor to be close to unity. Direct current as well as power closed-loop controls are introduced to reduce the steady-state error of AC signals. The bidirectional power conversion contains grid-connection and rectification modes with power flows from AC to DC and DC to AC sides, respectively. Analyses and experiments of separate single-phase constant power controls under unbalanced three-phase voltage are also given for both modes. In addition, the proposed system can serve as stable and independent voltage sources when power failure occurs. The 32-bit digital signal processor, TMS320F28069, is adopted as system core. The control strategies are implemented by C language for reliability and complexity improvement. The experimental results in grid-connected mode show output power of 6 kW on AC side, yielding power factor of 0.99. The corresponding phase voltage and its peak current are 220 V and 12.9 A, respectively, with total harmonic distortion (THD) of 2.63% and overall system efficiency of 98%. Whereas, the experimental results in rectification mode give output power and current on DC side of 6 kW and 15 A, respectively, with DC voltage ripple within 1%. The corresponding phase voltage and its peak current are 220 V and 12.9 A, with the THD, power factor and overall system efficiency of 2.93%, 0.99 and 97%, respectively. The experimental results verify the feasibility of the system proposed.

碩士<br>國立臺灣科技大學<br>電機工程系<br>106<br>This thesis aims to design grid-connected three-phase permanent-magnet synchronous motor (PMSM) drives with bidirectional power conversion. Energy recovery feature is provided for loss reduction in generator mode without additional breaking resistor. The system includes bidirectional three-phase grid- and motor-side power converters. The former uses grid voltage vector for input current control and dc output voltage supply. Meanwhile, a dual second-order generalized integrator under synchronous frame is adopted to estimate the phase angle of grid voltage for power-factor enhancement. Whereas, the latter drives PMSM with field-oriented control using resolver and current sensors to feed back rotor position, speed as well as phase current for speed and current closed-loop controls in order to improve the performance of the proposed drive. System simulation is given by using Matlab/Simulink. A 32-bit digital signal processor, TMS320F28069, is adopted as the control core. Since control strategies are mostly implemented by software program, circuit components are reduced largely. Experimental results show that when the three-phase PMSM is operated under motor mode at 1500 rpm, the mechanical power output from the PMSM is 2.22 kW with the peak grid phase current and total harmonic distortion (THD) of 10.1 A and 3.37%, respectively, the corresponding values on the motor input are 20.3 A and 3.93%. The efficiencies of grid-side rectifier, motor-side inverter and PMSM are 98%, 98% and 85%, respectively, resulting in the overall efficiency of 82%. While in generator mode at 1500 rpm, the mechanical power input to the permanent-magnet synchronous generator (PMSG) is 2.44 kW, the peak generator phase current and its THD are 16.0 A and 3.75%, respectively. The corresponding values on the grid side are 7.2 A and 4.57%. The efficiencies of PMSG, motor-side rectifier and grid-side inverter are 82%, 98% and 97%, respectively, yielding the overall efficiency of 80%. The feasibility of the proposed system is verified experimentally.

碩士<br>國立成功大學<br>電腦與通信工程研究所<br>105<br>This thesis presents the research on CMOS millimeter-wave (MMW) low power down conversion mixer and bidirectional up-/down-conversion mixer, implemented by standard TSMC 90-nm GUTM CMOS process. In the 60-GHz ultra-low-power down conversion mixer design, the mixer core is merged directly with self-biased trans-impedance amplifier (TIA) to omit its traditional load stage and to enhance the conversion gain. By using weak-inversion bias technique in a source-driven topology, the mixer core only needs quiescent current of uA which can be supported from TIA via the feedback resistor. The sub-harmonic mixers can work effectively for millimeter wave system by employing local oscillator (LO) frequency that is only half of the fundamental mixer. In the 80–105-GHz low LO power up-/down-conversion sub-harmonic mixer, by adopting weak inversion biasing technique of the transistor, the mixer demonstrates improved conversion loss under low LO driving power condition. In the 94-GHz CMOS bidirectional up-/down-conversion mixer integrated with T/R switch for single-mixer RF transceiver. The CMOS TRx uses only one up-/down-conversion mixer and T/R switches to change the modes between transmitting (Tx) and receiving (Rx) path. Compared with the traditional TRx architecture, it can reduce the chip size without use of additional mixer and filters, and also simplify the complexity of TRx design. All the measurements are conducted by fully on-wafer probing. According to different characteristics of the parameters and adjust the measurement methods and setting. Simulation and measurement results are compared and discussed.

碩士<br>國立臺灣科技大學<br>電機工程系<br>107<br>This thesis aims to develop single-phase grid-connected three-phase permanent-magnet synchronous motor (PMSM) drives with bidirectional power conversion. The system includes single-phase inverter and PMSM drives. The single-phase full-bridge inverter with digital phase-lock loop control is adopted to trace the voltage phase angle immediately. The bidirectional power conversion control strategy with the power compensation method is introduced to improve the stability of dc-link voltage. The three-phase three-leg inverter with field-oriented control is used to control the speed, torque, and rotor position of three-phase PMSM. Moreover, the feedback of three-phase current and rotor position, obtained by current sensor and resolver, is used to enhance the motor operating performance. When the system is operated in motor mode, PMSM is under speed control and the power flow from single-phase grid side to motor side. When the system is operated in generator mode, PMSM is under torque control and the power flows from motor side to single-phase grid side. Therefore, braking resistors needn’t be added in dc-link. The mechanical energy is converted to electrical energy directly, yielding the energy recovery benefits. The digital signal processor, TMS320F28069, is adopted as system core. When the system is operated in motor mode at 2500 rpm with mechanical load of 4 N-m, the peak phase current and total harmonic distortion (THD) are 6.17A and 2.63%, respectively, the RMS voltage of the single-phase grid side is 220V. The RMS inductor current and its THD of the single-phase grid side are 5.31A and 3.68%. The dc-link voltage is 400V. The system efficiency is 79.1%. When the system is operated in generator mode at the same situation, the peak phase current and THD are 6.38A and 1.94%, respectively, the RMS inductor current and its THD of single-phase grid side are 4.26A and 3.94%. The system efficiency is 85.0%. When the system is operated in rotor position control mode at 4 N-m, the mechanical angle of 1080 degrees in clockwise and counterclockwise rotation are implement stably in 1.2s. In conclusion, the experimental results verify the feasibility of the system.

The decarbonization of the energy system is one of the most complex and consequential challenges of the 21st century. Meeting this challenge will require the deployment of existing low carbon technologies at unprecedented scales and rates and will necessitate the development of new technologies that have the ability to transform variable renewable energy into high energy density products. Reversible Solid Oxide Cells (RSOCs) are electrochemical devices that can function both as fuel cells or electrolyzers: in fuel cell mode, RSOCs consume a chemical fuel (H₂, CO, CH₄, etc.) to produce electrical power, while in electrolysis mode they consume electric power and chemical inputs (H₂O, CO₂) to produce a chemical fuel (H₂, CO, CH₄, etc.). As such, RSOC systems can be thought of as flexible “energy hubs” that have unique potential to bridge the low power density renewable infrastructure with that of high energy density fuels in an efficient, dynamic, and bidirectional fashion. This dissertation explores the different operational sensitivities and design trade-offs of a methane based RSOC system, investigates the optimum operating strategies for a system that adapts to variations in the hourly spot electricity and fuel prices in Western Denmark, and provides an economic analysis of the system under a wide variety of design assumptions, operational strategies, and fuel and electricity market structures. In order to perform such comprehensive analyses, a 0-D computational model of a methane based RSOC system was developed in Python. In fuel cell mode, the system generates power by consuming natural gas, while in electrolysis mode the system generates synthetic natural gas (SNG) by electrolyzing steam and catalytically hydrogenating recycled CO₂ into CH₄ downstream of the RSOC. The model's flexibility enables the simulation of “part-load” operation, allowing the user to assess the changes in output, efficiency, and operating cost as the system is operated across multiple points. The model has the ability to evaluate the impact that changes in design choices and operating parameters (Area Specific Resistance, temperatures, current density, etc.) have on the system as it interfaces with time varying exogenous factors such as fuel and electricity prices. As such, one of the main contributions of this model is the ability to run simulations in which the operating strategy of the RSOC system responds and adapts to varying market signals. The computational model is used to develop a series of hourly optimizations for finding the optimal operating strategy for an RSOC system that can buy or sell electricity and gas in the spot electricity and natural gas markets in Western Denmark. After receiving an electricity and gas price signal, the optimization determines the operating mode (fuel cell, electrolysis or idle) and operating point (e.g., current density) that maximize the operating profits every hour for the given electricity and gas price pair. In order to avoid the speculation associated with traditional energy storage simulations, the system is “opened” at both ends, allowing it to instantaneously buy and sell any electricity or gas that is generated. Thus, the system never stores any of the products and it buys and sells them at the instantaneously available market price. By assuming that market prices reflect all existing information, this design choice removes the necessity of having to speculate about the future in order to determine the optimum operating strategy. This approach is one of the innovations presented in this work. The optimizations aim at maximizing the operating profits at each hour of the year, and decisions of operating mode and point are based on marginal operating costs for each electricity and natural gas price pair. The full economic analysis, however, requires the understanding of how design choices (e.g. operating limits, heat management, gas recycling systems, etc.) affect the investment costs, and therefore a Total Plant Cost (TPC) model is developed. For each design choice, the TPC model is used to compute a cost of the system per m² of active electrode area or kW of output. This value, assumed to be a sunk cost that does not affect the operating decision, together with the operating profits resulting from the optimization is used to assess the overall profitability of the system. For a system with 100m² of active electrode area, conventional costing metrics suggest that the balance of plant (BoP) components for managing the system's heat (Heat exchangers, evaporators, condensers) are the main cost drivers and represent roughly 50% of the TPC. The cost of the electrochemical RSOC stack, assembly, power inverter and piping represent 35% of the cost, with the other 15% coming from pumps, compressors and the methanation system. Twenty different optimization scenarios are developed in order to quantify the effect that system design choices, operating limits, and market prices have on the operating profile and on the overall economics of the system. The first 12 case studies are based on real hourly spot electricity and natural gas prices for the years 2009-2014 in Western Denmark. For the last 8 scenarios, a forecasted hourly time-series for electricity in the Danish grid for the year 2050 and two fixed SNG prices (high and a low) are used. The 2050 prices, which assume a fossil fuel free system, are used to understand the role and value that RSOC systems can offer in deeply decarbonized energy systems. For each optimization, different parameters such as the initial ASR and the operating limits (maximum current densities for each mode of operation) are varied in order to find the impact that these changes have on the system's design (balance of plant components), hourly operating mode, investment costs, hourly operating profits, and overall plant profits. For the 2009-2014 optimizations, it is found that the sale of electricity (fuel cell mode) and fuel (electrolysis mode) is not large enough to cover the fixed costs associated with the plant. Fuel cell mode dominates the operation (61% of the time) with electrolysis representing only ~ 4% of the operating hours. ASR is found to have an important impact on the system's economics, due to the fact that a lowering of the ASR leads to a reduction in the size of the heat management system, which in turn reduces the Total Plant Cost. For the 2050 dataset, it is found that under the high gas price scenario electrolysis mode dominates (50% of the time), and fuel cell operation represents 15% of the hours in the year. For the low SNG price, electrolysis still dominates (48% of the time), and fuel cell operation increases to 30% of the operating hours. Furthermore, for the high SNG scenario, the sale of fuel and electricity are large enough to cover the system's fixed cost, making the system attractive from an investment perspective. For the low SNG price, the system also becomes profitable when using ASR values of 0.4 ASR or below.

Dissertação de mestrado em Engenharia Eletrónica Industrial e Computadores<br>A elevada dependência energia elétrica por parte das sociedades aliada ao facto de uma presumível escassez dos principais meios de produção de energia atual, mais propriamente os combustíveis fósseis, tem proporcionado o investimento em soluções de produção de energia alternativas de forma a colmatar as necessidades energéticas. Essas soluções consistem no desenvolvimento de fontes de produção de energia renovável tendo como princípio o aproveitamento dos recursos naturais de forma a promover uma produção de energia limpa e sustentável. No entanto alguns tipos de fontes de energia renováveis têm como principal desvantagem uma produção de energia intermitente e o requerimento de um sistema que permita a interface com a rede elétrica como é o caso da energia solar o que normalmente implica a introdução problemas de qualidade de energia elétrica (QEE). Estes problemas evidenciados aliados ao facto da crescente conexão de cargas não lineares na rede elétrica, fomentam impactos negativos no que concerne à qualidade de energia. Posto isto no sentido de mitigar tais problemas, têm sido desenvolvidos sistemas de resolução de problemas de qualidade de energia que integram sistemas de produção de energia renovável e também sistemas de armazenamento de energia de forma a que em períodos de intermitência seja colmatada a falta de energia elétrica. Neste sentido, a presente dissertação visa a conceção de um conversor CC-CC multinível para um UPQC trifásico que permite a interface com painéis solares fotovoltaicos e um sistema de armazenamento de energia (baterias). O conversor CC-CC no ponto de interface com os painéis solares fotovoltaicos permite um fluxo unidirecional de energia, sendo responsável por controlar a potência extraída dos painéis fotovoltaicos. Já no ponto de interface com as baterias permite um fluxo bidirecional sendo responsável por controlar a carga e descarga das baterias. No desenvolvimento desta dissertação é apresentado uma revisão bibliográfica sobre a tecnologia solar fotovoltaica, sobre os sistemas de armazenamento de energia, com principal foco nas baterias, sobre conversores CC-CC e possíveis estratégias de controlo dos mesmos, as respetivas simulações computacionais do conversor proposto, a conceção do protótipo em contexto laboratorial e por último a sua validação experimental.<br>The high dependence of electrical energy by the societies, combined with the fact that a presumed shortage of the main means of energy production, rather fossil fuels, has provided the investment in alternative energy production solutions in order to meet the energy needs. Part of these solutions consist in the use of renewable energy sources for energy production, based on the principle of using natural resources, in order to promote clean and sustainable energy production. However, some types of renewable energy sources have as main disadvantage an intermittent energy production, as well as the requirement of a system that allows the interface with the electrical grid as is the case of solar energy that, usually, implies the introduction of power quality (PQ) problems. These problems, allied to the increasing connection of nonlinear loads into the electrical grid, have a negative impact on the PQ. In order to mitigate such problems, dedicated systems have been developed, some of them also integrating renewable energy production systems and energy storage systems. In this sense, the present dissertation aims the development of a DC-DC multilevel converter for a three-phase UPQC allowing the interface of photovoltaic solar panels (as a renewable energy source) and a set of batteries (as an energy storage system). The DC-DC converter at the interface point with the PV solar panels allows a unidirectional power flow and is responsible for controlling the power extracted from the photovoltaic panels. In the point of interface with the batteries, it allows a bidirectional power flow, which is responsible for controlling the batteries charging and discharging. In this dissertation, a bibliographical review is presented on solar photovoltaic technologies, on energy storage systems, with the main focus on the batteries, a review of DC-CC converters and possible control strategies, a set of computational simulations of the proposed DC-DC converter, a conception of the prototype in a laboratory context and, finally, its experimental validation.<br>FCT – Fundação para a Ciência e Tecnologia pelo suporte financeiro concedido através do Projeto 0302836 NORTE-01-0145-FEDER-030283 e ERDF–COMPETE 2020 Programme, SAICTPAC/0004/2015–POCI–01–0145–FEDER–016434

Dissertação de mestrado em Engenharia Eletrónica Industrial e de Computadores<br>Atualmente, a utilização de cargas não-lineares na rede elétrica é uma constante. Este tipo de cargas leva a uma degradação da Qualidade de Energia Elétrica, uma vez que consome harmónicos de corrente, prejudicando o transporte e a distribuição de energia e o funcionamento da maioria dos equipamentos ligados à rede elétrica. Para além disso, em determinados sistemas há cargas que necessitam de ser alimentadas ininterruptamente, tais como controladores de processos industriais, computadores, equipamentos médico e sistemas de comunicação de dados, pelo que estas cargas não podem depender exclusivamente da rede elétrica, uma vez que, sendo esta suscetível a falhas, terá de ser complementada por geradores de emergência ou UPSs (Uninterruptible Power Supplies – fontes de alimentação ininterruptas). Deste modo, torna-se necessário o desenvolvimento e a utilização de equipamentos capazes de mitigar os problemas acima referidos. No Grupo de Eletrónica de Potência e Energia (GEPE) da Universidade do Minho têm sido desenvolvidos Filtros Ativos de Potência para compensar problemas de Qualidade de Energia. Assim sendo, neste trabalho de Mestrado foi proposto o desenvolvimento de um Filtro Ativo Paralelo Monofásico com operação como UPS. Este equipamento é capaz de compensar o fator de potência e os harmónicos de corrente em condições normais de funcionamento da rede elétrica e é também capaz de alimentar, de forma isolada, um conjunto de cargas prioritárias perante eventuais falhas na rede. Para além disso, foi também desenvolvido um conversor CC-CC bidirecional isolado com o intuito de carregar as baterias a partir da rede elétrica, através do barramento CC do Filtro Ativo Paralelo, bem como injetar energia na rede elétrica isolada proveniente das mesmas. Pretendeu-se que o equipamento desenvolvido fosse leve, compacto e com operação silenciosa, de modo a poder ser instalado no quadro elétrico de uma habitação. Deste modo, alguns procedimentos foram tomados aquando do projeto da solução apresentada, tais como a escolha dos semicondutores de potência e dos elementos magnéticos a utilizar. No final, foi efetuado um levantamento de custos da solução obtida de modo a analisar a sua viabilidade comercial.<br>Nowadays, the use of nonlinear loads connected to the electrical power grid is unceasing. This kind of electrical loads leads to Power Quality declining, since it consumes harmonic currents, worsening power transmission and distribution and the proper operation of a vast amount of power grid connected equipment. Furthermore, there are loads connected to several power systems that need incessant power supplying, such as industrial process controllers, computers, medical equipment and datacenters, whereby these loads cannot depend exclusively upon the power grid, since it is vulnerable to power outages, and therefore must be complemented by emergency generators or UPSs (Uninterruptible Power Supplies). Therefore, the development and use of equipment capable of mitigating these issues is needed. The Group of Energy and Power Electronics (GEPE) of the University of Minho has been developing Active Power Filters to compensate for Power Quality problems. Thus, the development of a Single-Phase Shunt Active Power Filter with UPS operation was proposed in this Master's thesis work. This equipment is capable of compensating for power factor and harmonic currents during normal operation of the power grid, and is also able to supply with isolation a set of priority electrical loads towards eventual power outages. Besides that, a bidirectional isolated DC-DC converter was developed in order to charge the battery pack from the power grid, through the Shunt Active Power Filter DC-link, as well as to provide energy stored in the batteries to the isolated electrical power grid. It was intended for the equipment to be weightless, compact and silent in order to be installed in a domestic electrical switchboard. Consequently, several procedures were taken during the solution’s development, such as the power semiconductors and the magnetic elements selection. In the end, it was performed the costing of the obtained solution with the purpose of evaluating its commercial feasibility.

Dissertação de mestrado em Engenharia Eletrónica Industrial e de Computadores<br>Hoje em dia, devido à utilização massiva de cargas não lineares pelos consumidores em geral, tem aumentado progressivamente o conteúdo harmónico nas formas de onda das correntes, que, por sua vez, provocam quedas de tensão nas impedâncias das linhas, contribuindo para o aumento do conteúdo harmónico das tensões na rede elétrica. Como resultado, cada vez mais a rede elétrica apresenta baixos índices de qualidade de energia elétrica. O projeto em que esta dissertação está enquadrada consiste no desenvolvimento de um condicionador da qualidade de energia unificado (unified power quality conditioner - UPQC) trifásico com interface, através do barramento cc, a uma fonte de energia renovável e a um sistema de armazenamento de energia. O UPQC desenvolvido consiste na junção de um condicionador ativo série (CAS), um condicionador ativo paralelo (CAP) e um conversor cc-cc com interface com a fonte de energia renovável e o sistema de armazenamento de energia e o barramento cc. Assim, o CAS é responsável por garantir tensões sinusoidais e equilibradas às cargas, o CAP é responsável por garantir correntes sinusoidais e equilibradas na rede elétrica e o conversor cc-cc tem como funcionalidade carregar ou descarregar as baterias e extrair a máxima potência da fonte de energia renovável. Com o desenvolvimento deste UPQC é possível melhorar a qualidade da energia elétrica, beneficiando tanto o utilizador final como o fornecedor de energia e todo o sistema de transporte. Assim, o âmbito desta dissertação é apenas referente ao desenvolvimento do conversor cc-ca para o CAP do UPQC. No âmbito desta dissertação, e de acordo com o enquadramento do projeto, este conversor é responsável por garantir correntes sinusoidais e equilibradas na rede elétrica, manter a tensão do barramento cc regulada e manter um fluxo bidirecional de energia com a rede elétrica de acordo com a operação do conversor cc-cc (fonte de energia renovável e sistema de armazenamento de energia).<br>Nowadays, due to the massive use of nonlinear loads by consumers in general, it has progressively increased the harmonics content in the waveforms of the currents, causesing voltage drops in the line impedances, contributing for increasing the harmonic content of the voltages in the electrical grid. As a result, each more, the electric grid presents low indices of power quality. The project where this dissertation is framed consists in the development of a three-phase unified power quality conditioner (UPQC) with interface, through the dc-link, to a renewable energy source and to an energy storage system (batteries). The developed UPQC consists is the combination of a series active conditioner (CAS), a parallel active conditioner (CAP) and a dc-dc converter for the interface between the CAS, the CAP, the renewable energy source and energy storage system. Therefore, the CAS is responsible for ensuring sinusoidal and balanced voltages to the loads, the CAP is responsible for ensuring sinusoidal and balanced currents to the electrical grid, and the dc-dc converter has the function of charging or discharging the batteries and extracting the maximum power from the renewable energy source. With the development of this UPQC, it is possible to increase the quality on the electrical grid side, benefiting: the end-user, the electricity supplier and the entire transportation system. Thus, the purpose of this dissertation is only related with the development of the dc-ac converter applied in the CAP of the UPQC. In the context of this work, and according to the project structure, this converter is responsible for ensuring sinusoidal and balanced currents from the electrical grid, maintaining a regulated dc-link voltage, as well as maintaining a bidirectional power flow according to the operation of the dc-dc converter (used to interface the renewable energy source and energy storage system).<br>FCT – Fundação para a Ciência e Tecnologia pelo suporte financeiro concedido através do Projeto 0302836 NORTE-01-0145-FEDER-030283 e ERDF–COMPETE 2020 Programme, SAICTPAC/0004/2015–POCI–01–0145–FEDER–016434

Tese de Doutoramento em Engenharia Eletrónica e de Computadores<br>Os veículos elétricos são cada vez mais uma realidade dos nossos dias. Contudo, a introdução dos veículos elétricos no mercado tem sido constrangida por várias condicionantes tecnológicas que limitam o seu desempenho e que inflacionam o seu custo. Por outro lado, a introdução dos veículos elétricos traz novas oportunidades, nomeadamente a sua integração nos sistemas elétricos como elemento estabilizador, podendo ainda contribuir para o aumento da eficiência energética. A eletrónica de potência associada aos sistemas de tração em veículos elétricos possui uma complexidade acrescida, originando questões técnicas e económicas mais relevantes que as da própria máquina elétrica. Deste modo, o controlador da máquina elétrica desempenha um papel vital, sendo uma peça essencial em termos de desempenho e eficiência energética global do sistema de tração. Por sua vez, a utilização de sistemas bidirecionais para o carregamento das baterias eletroquímicas dos veículos elétricos possibilita o armazenamento de energia, produzida em horas de vazio, para posterior devolução à rede elétrica em horas de pico de consumo. Esta funcionalidade permite uma melhor gestão da carga do sistema, sempre que seja necessário. Assim, estes sistemas bidirecionais surgem como uma mais-valia para os sistemas elétricos. Tendo em consideração as diversas oportunidades existentes, não só no desenvolvimento dos sistemas de tração, mas também dos sistemas de carregamento das baterias dos veículos elétricos, existe uma forte aposta no desenvolvimento tecnológico para a mobilidade elétrica. Deste modo, foi identificado um espaço para a conceção de uma nova topologia de conversor de eletrónica de potência que integra o sistema de tração e o sistema de carregamento de baterias. Consequentemente, esta nova topologia contribui para uma melhoria do desempenho global do veículo, através da redução do peso e do custo, e de um aumento de funcionalidades, com benefícios para o utilizador e para a rede elétrica. Assim, esta tese de doutoramento tem como objetivo conceber, desenvolver e testar uma nova topologia de conversor bidirecional unificado que integra o sistema de tração e o sistema de carregamento de baterias. Tradicionalmente, o veículo elétrico possui um conversor de eletrónica de potência que aciona a máquina elétrica responsável pela tração. Adicionalmente, existe um segundo conversor de eletrónica de potência para o carregamento das baterias. Pode constatar-se a existência de semelhanças entre estes conversores, permitindo antever uma convergência entre eles num único conversor de potência. Este conversor é controlado para que em cada momento execute as funcionalidades implementadas, de tração ou de carregamento de baterias. Quando o veículo elétrico se encontra em andamento, o conversor de eletrónica de potência opera bidirecionalmente para efeito de tração e de travagem regenerativa. Analogamente, quando o veículo elétrico se encontra imobilizado e acoplado à rede elétrica, o conversor de eletrónica de potência pode também operar bidirecionalmente, tendo a função de controlar a transferência de energia entre a rede elétrica e as baterias, efetuando a carga ou descarga das mesmas. Ao longo desta tese foi possível realizar a validação da nova topologia de conversor bidirecional unificado proposto, bem como dos algoritmos de controlo necessários. Deste modo, numa fase inicial, e com o auxílio de ferramentas de simulação computacionais, foi possível obter resultados que fundamentam o correto funcionamento do sistema proposto. Em seguida, procedeu-se à implementação prática do protótipo laboratorial, onde foi possível obter, de forma análoga, resultados do funcionamento do protótipo desenvolvido. Com base nesses resultados experimentais, comparados com as simulações, foi possível comprovar o correto funcionamento da nova topologia proposta.<br>Electric vehicles are increasingly a reality of our days. However, the introduction of the electric vehicles in the market has been constrained by several technical constrictions, limiting their performance and increasing their cost. On the other hand, the introduction of electric vehicles brings new opportunities, namely their integration into the electrical power systems as a stabilizing element, and also contributing to improve energy efficiency. The power electronics associated with the powertrain systems for electric vehicles has increased complexity, witch brings technical and economic issues more relevant than those of the electric machine. In this way, the controller of the electrical machine has vital importance, being an essential part in terms of performance and overall powertrain system energy efficiency. On the other hand, the use of bidirectional systems for charging the electric vehicles electrochemical batteries allows the storage of energy produced during low consumption hours, for later return to the power grid during peak consumption hours. This feature can allow a better load system management whenever needed. These bidirectional systems can appear as an asset for the electrical power systems. Taking into consideration the existing opportunities, not only in the development of powertrain systems, but also on the charging systems of the electric vehicle batteries, there is a strong investment in technological development for electric mobility. Therefore, it was identified space for the creation of a new topology of power electronics converter that integrates the powertrain system and the batteries charging system. Consequently, this new topology contributes to increase the overall performance of the vehicle, reducing weight, space occupation and costs, and adding new functionalities which benefits the users of the electric vehicles and also the electrical power grid. The research work proposed in this PhD Thesis aims to design, develop and test a new topology of bidirectional converter that integrates the powertrain and the battery charging system. Traditionally, an Electric Vehicle has a power converter that drives the electric machine responsible for the traction. Additionally, there is a second power electronics converter used to charge the batteries. It can be observed similarities between these two power converters that allow foreseeing a convergence between them in a single power converter. This power converter is controlled at each moment to execute the implemented functionalities, as powertrain or as battery charging system. When the electric vehicle is running, the power electronics converter operates bidirectionally for traction and regenerative braking. Similarly, when the electric vehicle is immobilized and connected to the power grid, the power electronics converter can also operate bidirectionally, having the function of controlling the energy flow between the power grid and the batteries, during the charging or discharging. During this PhD Thesis it was possible to perform the validation of the new proposed unified bidirectional converter topology, as well as the verification of the necessary control algorithms. In an initial phase, with the aid of computational simulation tools, it was possible to obtain simulation results to support the correct operation of the proposed system. Then, the laboratory prototype was implemented, and it was possible to obtain the operation results with the developed prototype. Based on these experimental results, and comparing with those obtained on the simulations, it was possible to prove the correct operation of the new proposed topology.<br>Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/86628/2012

Dissertação do mestrado em Engenharia Eletrónica Industrial e Computadores<br>A Qualidade de Energia Elétrica (QEE) é um tema cada vez mais importante no ramo da engenharia, pois os problemas na rede elétrica podem levar a que os equipamentos não funcionem corretamente. Isso, faz com que muitos clientes, no sector industrial serviços tenham prejuízos económicos muito elevados. Porém, muitos desses problemas ocorrem devido às cargas utilizadas pelos clientes que “poluem” a rede elétrica com potência reativa e harmónicas. Existem equipamentos de eletrónica de potência que mitigam estes problemas de Qualidade de Energia Elétrica, entre eles o Condicionador Unificado de Qualidade de Energia (Unified Power Quality Conditioner - UPQC). Esta dissertação aborda uma nova topologia deste equipamento chamado Condicionador Unificado de Qualidade de Energia com Controlo Invertido (iUPQC) Monofásico com a adição de baterias, para permitir o modo de alimentação ininterrupta da instalação (Uninterruptible Power Supply – UPS) denominando-se assim iUPQC-UPS. Um UPQC é um equipamento constituído por um condicionador ativo série (Conversor CC-CA) e um condicionador ativo paralelo (Conversor CC-CA) que ligam a um barramento CC comum. Este barramento irá ligar às baterias a partir de um conversor CC-CC bidirecional. O objetivo do UPQC com controlo invertido é que o condicionador ativo série absorva da rede a potência ativa necessária impondo uma corrente sinusoidal do lado da rede, enquanto que o condicionador ativo paralelo fornece às cargas uma tensão sinusoidal com frequência e valor eficaz normalizado. Desta forma, todas a potência reativa e harmónicas serão fornecidos pelo condicionador ativo paralelo. Esta dissertação apresenta um estudo bibliográfico dos condicionadores ativos de potência que mitigam os problemas de QEE, das topologias dos conversores de potência e dos seus algoritmos de controlo. Com base neste estudo, foi usada a ferramenta PSIM para fazer simulações dos modos de funcionamento do iUPQC-UPS. Posteriormente, foi desenvolvido o protótipo do iUPQC-UPS, constituído pelo sistema de controlo, sistema de comando e sistema de potência. Por ultimo, o protótipo foi validado ao retirar os resultados experimentais de todos os modos de funcionamento.<br>Electrical Power Quality is an increasingly important topic in the engineering field, as the problems created in the electrical network lead to the equipment not working properly. This causes many customers in the industrial services sector to have very high economic losses. However, many of these problems occur due to the loads used by customers that “pollute” the Electric Grid with reactive power and harmonics. There are power electronics equipment that mitigate these Power Quality problems, among them the Unified Power Quality Conditioner (UPQC). This dissertation approaches a new topology of this equipment called Unified Power Quality Conditioner with Inverted Control (iUPQC) with the addition of batteries, to allow the uninterruptible power supply of the installation (Uninterruptible Power Supply - UPS), thus called iUPQC- UPS. This equipment consists of a series active conditioner (DC-AC converter) and a parallel active conditioner (DC-AC converter) that connect to a common DC bus. This bus will connect to the batteries from a bidirectional DC-DC converter. The objective is that the series active conditioner absorbs the necessary power from the power grid while imposing a sinusoidal current on the power grid side, while the shunt active conditioner provides the loads with a sinusoidal voltage with normalized frequency and effective value. In this way, all reactive power and harmonics will be provided by the shunt active conditioner The batteries will charge or discharge as needed by the network. That is, if the power of the network is greater than the power of the loads, the batteries will use power from the network to charge. If the power of the network is less than the power of the loads, the batteries will discharge when supplying power to the loads.<br>Este trabalho de dissertação está enquadrado no projeto IC&DT “Quality4Power – Enhancing the Power Quality for Industry 4.0 in the era of Microgrids”, financiado pela Fundação para a Ciência e Tecnologia, com a referência PTDC/EEI-EEE/28813/2017

Tese de Doutoramento Engenharia Eletrónica e de Computadores<br>A aposta na mobilidade elétrica, principalmente em veículos elétricos (VEs), representa um novo paradigma de transporte tendo por base a mobilidade eficiente e sustentável. Como consequência, é também uma mais-valia para a independência dos custos do petróleo e para a redução das emissões de gases com efeito de estufa. Para que este novo paradigma de transporte seja uma alternativa viável face aos atuais veículos com motor de combustão interna, é espectável que os VEs tenham custos reduzidos, tanto ao nível da utilização como da produção e manutenção. Além disso, com a sua integração nas redes elétricas, é também espectável que a qualidade da energia elétrica não seja descurada. Assim, o projeto de investigação apresentado nesta tese enquadra-se na conjuntura atual de desenvolvimento científico e tecnológico da mobilidade elétrica. Neste contexto, são propostos novos modos de operação que permitem a integração dinâmica dos VEs na rede elétrica visando as smart grids, assim como novas topologias on-board e off-board para sistemas de carregamento de baterias de VEs. Hoje em dia, tipicamente, os VEs disponíveis comercialmente apenas permitem carregar as baterias através do modo de operação grid-to-vehicle (G2V). Nesta tese, os sistemas de carregamento de baterias de VEs desenvolvidos permitem operar em modo bidirecional, viabilizando o modo de operação vehicle-to-grid (V2G). Através dos modos de operação G2V e V2G, o VE pode atuar contextualizado com cenários colaborativos com a rede elétrica, i.e., como elemento consumidor, armazenador e fornecedor de energia, dando especial contributo à área de sistemas de armazenamento de energia das smart grids. Além disso, tendo em conta a evolução das smart homes e smart grids, nesta tese são propostos e validados experimentalmente novos modos de operação que representam novos desafios e oportunidades para a utilização do VE. Nesta tese é proposto o modo de operação home-to-vehicle (H2V), que é referente ao controlo dos modos de operação G2V e V2G em função das cargas da casa onde o VE está conectado. É proposto o modo de operação vehicle-for-grid (V4G), que está relacionado com a evolução das smart homes nas smart grids, e é referente à utilização do VE para mitigar problemas de qualidade da energia elétrica (fator de potência e harmónicas de corrente), durante os modos de operação G2V e V2G, ou mesmo fora dos períodos de operação nestes modos. É também proposto o modo de operação vehicle-to-home (V2H), que está relacionado com a evolução das smart homes nas smart grids, e é referente à utilização do VE como fonte de tensão independente ou como fonte de tensão ininterrupta, semelhante a uma uninterruptible power supply (UPS) do tipo off-line. Além da contextualização com estes modos de operação, os sistemas de carregamento de baterias propostos podem também operar em colaboração com fontes de energia renováveis, contribuindo para a integração ativa destes veículos na rede elétrica. Além dos modos de operação, nesta tese estão também propostas novas topologias para sistemas de carregamento de baterias de VEs on-board e off-board. O sistema de carregamento de baterias de VEs on-board é composto por um conversor CA-CC front-end do tipo multinível para interface com a rede elétrica, e por um conversor CC-CC back-end do tipo interleaved para interface com as baterias do VE. Por outro lado, o sistema de carregamento de baterias de VEs off-board é composto por um conversor CA-CC front-end do tipo interleaved para interface com a rede elétrica, e por um conversor CC-CC back-end bidirecional de três níveis para interface com as baterias do VE. Além dos sistemas de carregamento de baterias de VE on-board e off-board, nesta tese é também proposto um sistema integrado de carregamento de baterias e de interface com fonte de energia renovável. Este sistema integrado é composto por um conversor CA-CC front-end full-bridge para interface com a rede elétrica e por dois conversores CC-CC back-end half-bridge para interface com as baterias do VE e com a fonte de energia renovável. As topologias dos sistemas de carregamento de baterias de VE on-board e off-board, assim como do sistema integrado, estão validadas através de resultados de simulação e através de resultados experimentais, obtidos com os protótipos desenvolvidos no âmbito desta tese.<br>The focus on electric mobility, especially in electric vehicles (EVs) represents a new transport paradigm based on the efficient and sustainable mobility. As consequence, it is also an asset for the independence of oil costs and for the reduction of emissions of greenhouse gases. In order to obtain real benefits from this new transportation paradigm in counterpart of the traditional vehicles with internal combustion engine, it is expected that the EVs will have reduced costs, both in terms of usage as production and maintenance. Moreover, with the EVs integration in the power grids, it is also expected that the power quality is not neglected. Thus, the research project presented in this thesis is framed with the current situation of scientific and technological development for electric mobility applications. In this context, are proposed new operating modes that enable the dynamic integration of EVs into the power grids targeting smart grids, as well as new topologies of on-board and off-board EV battery charging systems. Nowadays, typically, the available EVs only allow charge the batteries through the grid-to-vehicle (G2V) operation mode. In this thesis, the developed EVs battery charging systems admit the bidirectional operation, also enabling the vehicle-to-grid (V2G) operation mode. Through the G2V and V2G, the EV can operate contextualized with collaborative scenarios with the power grid, i.e., capable of consuming, storing, and providing energy, representing a special contribution for the area of energy storage systems in the smart grids. Besides, taking into account the evolution of smart homes and smart grids, in the scope of this thesis are proposed, and experimentally validated, new operation modes that represent new challenges and opportunities for the EV usage. In this thesis is proposed the home-to-vehicle (H2V) operation mode, which is related with the dynamic control of the G2V and V2G modes according with the electrical appliances connected in the same installation. It is proposed the vehicle-for-grid (V4G) operation mode, which is related with the evolution of smart homes in the smart grids, and consists in the use of the EV battery charger to mitigate some power quality problems (power factor and current harmonics) during the G2V and V2G operation modes. It is also proposed the vehicle-to-home (V2H) operation mode, which is related with the evolution of smart homes in the smart grids, and consists in the use of the EV battery charger as voltage source in isolated systems or as an off-line uninterruptible power supply (UPS). Besides the contextualization with these operation modes, the proposed topologies for the EV battery charging systems can also operate in collaboration with renewable energy sources, contributing to their active integration into the power grid. Besides the aforementioned operation modes, in this thesis are also proposed new topologies of on-board and off-board EV battery charging systems. The on-board EV battery charging system is composed by a multilevel AC-DC front-end converter used to interface the power grid, and by an interleaved DC-DC back-end converter used to interface the EV batteries. On the other hand, the off-board EV battery charging system is composed by a three-phase interleaved AC-DC front-end converter used to interface the power grid, and by a bidirectional three-level DC-DC back-end converter used to interface the EV batteries. Besides the on-board and off-board EV battery charging systems, in this thesis is also proposed an integrated system to interface an EV and a renewable energy source with the power grid. This integrated system is composed by a full-bridge AC-DC front-end converter used to interface the power grid, and by two half-bridge DC-DC back-end converters used to interface the EV batteries and the renewable energy source. The topologies of the on-board and off-board EV battery chargers, as well as the integrated topology, are validated through simulations and experimental results obtained with the prototypes developed in the scope of this thesis.<br>Parte dos trabalhos foram também suportados pelo COMPETE: POCI-01-0145-FEDER-007043 e pela FCT no âmbito do projeto: PEst-UID/CEC/00319/2013.

Neste projeto fez-se a análise, ao nível de simulação em software do efeito da integração de um sistema de baterias na rede da ilha do Porto Santo, ou seja numa rede isolada com o objetivo de apoiar a geração de energia durante os períodos de cheia e aproveitar o excesso de produção durante os períodos de vazio de carga para recarregamento do sistema, contribuíndo para a melhoria do rendimento de geração de energia elétrica na ilha. Com este intuito, procedeu-se à implementação, com o auxílio do software PSSE (Power System Simulation for Engineering) e do Matlab/Simulink, de uma rede com base no modelo de rede elétrica da ilha do Porto Santo ao nível dos componentes que a caracterizam. Inicialmente fez-se uma análise do funcionamento atual da rede elétrica, registando-se as suas funcionalidades e modo de operação. Em adição à rede elétrica desenvolvida em software de simulação, desenvolveu-se e simulou-se em Matlab/Simulink o modelo de um sistema de conversão de energia e banco de baterias adequado, quer ao nível dos objetivos de potência e tempo de operação pretendidos, quer ao nível da viabilidade de implementação prática analisando-se as características do sistema implementado e aplicando-as a um sistema no software PSSE para a realização de uma análise mais aprofundada dos efeitos da implementação do sistema de baterias na rede em termos de simulação vetorial e temporal. Observou-se e analisou-se ainda o funcionamento da rede, em diversas condições de operação, para cenários diversos, sem sistema de baterias e com sistema de baterias tendo-se verificado a viabilidade de implementação do mesmo, levando à mitigação das necessidades de utilização de um segundo grupo gerador na central térmica.<br>In this project, the effect of the integration of a battery system in the power grid of the island of Porto Santo was analyzed at the software simulation level. Being an isolated power grid, the goal of the integration of the system is to back up the power generation during peak demmand periods and use low demand periods to recharge, improving therefore the efficiency of power generation in the island. With this purpose, using the software PSSE (Power System Simulation for Engineering) and Matlab/Simulink the model of a power grid was developed with the maximum similarity possible to the grid of the island of Porto Santo, in terms of its components characteristics. The project started with the annalyzis of the grid as it is now with the registration of the components capabilities and operation mode. In adition to the development of the power grid model, a suitable power convetion and battery system model was also developed and tested using Matlab/Simulink, in terms of power supply and response time needed, but also considering it’s implementation viability in terms of existing components and economic viability. Using the obtained results, the created model was the basis for the development of a similar model in PSSE for vector and time domain analysis. The grid’s operation was also observed and registred in diversified load and generation conditions, without and with battery system in operation, having accounted for the viability of implementation of the system in terms of electrical performance, mitigating the need for a second generator group at the thermal power plant.