The penetration of renewable and distributed generation sources (DGs) in power distribution systems has been increasing at an ever-faster rate. While DGs provide clean and affordable energy, their addition introduces new problems in the system operation. One of the main challenges due to the high penetration of DGs is the overvoltage issues that demand appropriate voltage control. This control is essential to maintain the power quality, energy efficiency, and voltage stability in the system. Voltage Regulators (VRs) and capacitor banks (CBs) are traditional control devices that are installed in the system to keep the desired voltage profile. However, they are not designed to operate in a way that can address the high frequency and magnitude changes occurring in systems with high penetration of DGs. Therefore, they need to be supplemented with voltage control performed by controlling the reactive power generation of the DGs. The coordination among these different control devices is essential for proper system operation. This thesis explores the design of the coordinated control of VRs, CBs, and DGs, by considering different control methods such as coordinated cooperative, predictive cooperative, and unified control of all voltage control devices. The proposed methods are implemented in a system with high penetration of DGs and tested by exploring the worst-case scenario in terms of DG sizing and placement. This scenario is determined analytically using sensitivities and verified using stochastic Monte Carlo simulation. The future generation of active power distribution systems need to be optimally controlled in order to be efficient, reliable, and resilient, while capable of effectively managing high penetration levels of DGs, and other controllable loads and devices. The important outcome of this thesis is the introduction of a practical voltage control method to achieve these goals.

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A wearable body temperature sensor would allow for early detection of fever or infection, as well as frequent and accurate hassle-free recording. This thesis explores the design of a body-temperature-sensing device inkjet-printed on a flexible substrate. All structures were first modeled by first-principles, theoretical calculations, and then simulated in HFSS. A variety of planar square inductor geometries were studied before selecting an optimal design. The designs were fabricated using multiple techniques and compared to the simulation results. It was determined that inductance must be carefully measured and documented to ensure good functionality. The same is true for parallel-plate and interdigitated capacitors. While inductance remains relatively constant with temperature, the capacitance of the device with a temperature-sensitive dielectric layer will result in a shift in the resonant frequency as environmental or ambient temperature changes. This resonant frequency can be wirelessly detected, with no battery required for the sensing device, from which the temperature can be deduced. From this work, the optimized version of the design comprises of conductive silver in with a temperature-sensitive graphene oxide layer, intended for inkjet-printing on flexible polyimide substrates. Graphene oxide demonstrates a high dielectric permittivity with good sensing capabilities and high accuracy. This work pushes the state-of-the-art in applying these novel materials and techniques to enable flexible body temperature sensors for future biomedical applications.

Esta Tese aborda o estudo de transistores por efeito de campo orgânicos (OFETs do inglês, Organic Feld-Effect Transistors). Entender o comportamento da carga acumulada no canal do OFET, a qual é responsável pelo processo de condução elétrica no dispositivo, é de grande importância para ajudar a melhorar sua eficiência ou a propor um modelo teórico que descreva o comportamento do transistor em todos os seus regimes de operação. Vários trabalhos na literatura investigam o campo elétrico na camada semicondutora do transistor (ao longo do canal) gerado pela acumulação de cargas, porém nenhum investiga o campo na camada dielétrica de OFETs, que é diretamente proporcional à carga acumulada no canal. Investigou-se inicialmente o campo elétrico na camada dielétrica do dispositivo por meio da espectroscopia vibracional por Geração de Soma de Frequências (espectroscopia SFG do inglês, Sum-Frequency Generation). Espectros SFG obtidos nos dispositivos polarizados exibiram uma banda em ~1720 cm-1, devido ao grupo carbonila da camada dielétrica orgânica (PMMA – poli(metil metacrilato)), cuja a amplitude foi proporcional à voltagem de porta aplicada, indicando que esses grupos polares foram orientados sob ação do intenso campo elétrico no dispositivo. Esse sinal SFG induzido pelo campo pode ser devido a duas contribuições, um termo não linear de segunda ordem (devido à reorientação molecular) e outro de terceira ordem (interação entre os campos ópticos e o campo estático no volume do material). Observamos uma redução quase completa do sinal SFG em altas temperaturas (próximas da Tg do polímero dielétrico), indicando que o mecanismo de reorientação molecular é o responsável pelo sinal SFG gerado. Foram realizadas então medidas preliminares de microscopia SFG para mapear esse sinal SFG ao longo do canal de OFETs a base dos polímeros N2200 (semicondutor) e PMMA (dielétrico). Os resultados conseguem demonstrar a variação da densidade de carga acumulada no canal quando o dispositivo está polarizado e próximo à saturação. Usando Microscopia por Modulação de Carga (microscopia CMM do inglês, Charge Modulation Microscopy), que é outro método não invasivo para investigar a acumulação de cargas em um dispositivo operando, mapeamos a distribuição de carga no canal desses OFETs com alta resolução espacial (sub-micrométrica). Além disso, uma simulação da densidade de carga esperada e dos perfis de CMM foi realizada usando um modelo ambipolar para OFETs. Com base nessas simulações, propusemos uma modulação de onda quadrada do OFET, que permite uma comparação mais direta dos perfis de CMM com o perfil de densidade de carga ao longo do canal do transistor. Usando o esquema proposto, esses perfis foram medidos e comparados com o esperado com base no modelo ambipolar. Em geral os perfis de densidade de carga obtidos concordam bem com o modelo, usando apenas um único parâmetro global ajustável, exceto muito próximo do eletrodo de dreno e no regime de saturação profunda, quando os experimentos apresentam um artefato devido à eletro-absorção e não permitem uma comparação precisa com o modelo. Portanto, espera-se que esta Tese tenha contribuído para o avanço de técnicas de caracterização da distribuição de carga em OFETs, e assim melhorar o entendimento de seus mecanismos de funcionamento. / This Thesis deals with the study of Organic Field Effect Transistors (OFETs). Understanding the behavior of the accumulated charge along the OFET channel, which is responsible for the electrical conduction process in the device, is of great importance for improving its efficiency or proposing a theoretical model that describes the behavior of the transistor in all its operating regimes. Several studies in the literature investigate the electric field in the semiconductor layer of the transistor (along the channel) generated by the charge accumulation, but none investigates the field in the OFET dielectric layer, which is directly proportional to the charge accumulated in the channel. The electric field in the dielectric layer of the device was initially investigated by Sum-Frequency Generation (SFG) vibrational spectroscopy. SFG spectra obtained in the polarized devices exhibited a band at ~ 1720 cm-1, due to the carbonyl group of the organic dielectric layer (PMMA - poly (methyl methacrylate)), whose amplitude was proportional to the applied gate voltage, indicating that these polar groups were oriented by the intense electric field in the device. This field-induced SFG signal may be due to two contributions, a second order non-linear term (due to molecular reorientation) and a third order term (interaction between the optical fields and the static field in the material volume). We observed an almost complete reduction of the SFG signal at high temperatures (close to the Tg of the dielectric polymer), indicating that the molecular reorientation mechanism is responsible for the generated SFG signal. Preliminary SFG microscopy measurements were performed to map this SFG signal along the channel of OFET fabricated with N2200 (semiconductor) and PMMA (dielectric) polymers. The results demonstrate the variation of the accumulated charge density along the channel when the device is polarized and close to saturation. Using Charge Modulation Microscopy (CMM), which is another noninvasive method to investigate the accumulation of charges in an operating device, we mapped the charge distribution in the channel of these OFETs with high spatial resolution (sub-micrometer). In addition, a simulation of the expected charge density and CMM profiles was performed using an ambipolar model for OFETs. Based on these simulations, we proposed a square-wave modulation of the OFET, which allows a more direct comparison of the CMM profiles with the charge density profile. Using the proposed scheme, these profiles along the transistor channel were measured and compared with those expected from the ambipolar model. In general, the obtained charge density profiles agree well with the model, using only a single global adjustable parameter, except very close to the drain electrode and in the deep saturation regime, when the experiments have an artifact due to the electro-absorption and do not allow a precise comparison with the model. Therefore, it is expected that this Thesis has contributed to the advancement of techniques to characterize the charge distribution in OFETs, and thus improve the understanding of its operating mechanisms. Keywords: Field-effect transistors. Organic electronics. Nonlinear optics. Sum-frequency generation. Polarization of dielectrics. Charge modulation microscopy. Metal-insulator-semiconductor capacitor.

Apresentamos neste trabalho um estudo do efeito da depleção do silício policristalino e da corrente de tunelamento em dispositivos com óxidos de porta finos. Utilizamos curvas características da capacitância em função da tensão de porta (C-V), para analisar a degradação causada por estes efeitos.Quanto ao efeito da depleção do silício policristalino a capacitância total na região de inversão apresenta uma redução conforme a concentração de dopantes do silício policristalino diminui. Este efeito foi observado em curvas C-V tanto de alta como de baixa freqüência, sendo esta última mais afetada. A corrente de tunelamento através do óxido de porta apresentou uma influência na largura da região de depleção no silício, que aumentou devido ao tunelamento de portadores do substrato. Como resultado, uma diminuição na capacitância do silício foi observada, fazendo a curva C-V diminuir na região de inversão. Quando considerado o efeito de depleção no silício policristalino junto com o efeito do tunelamento, observou-se que na região da porta houve um excesso de portadores, causando uma diminuição na região de depleção do silício policristalino. Neste caso a curva C-V sofreu uma maior redução, tornando-se difícil separar os dois efeitos. A curva C-V de baixa freqüência foi a mais atingida, pois como os portadores tem tempo de resposta, pode-se observar a influência da corrente de tunelamento nas cargas de inversão. Apresentamos ainda um novo método para a determinação da concentração de dopantes no substrato e no silício policristalino, através de curvas C-V de alta freqüência. Simulações numéricas bidimensionais e medidas experimentais foram utilizadas para validação do método. Os resultados obtidos indicam que o método proposto apresenta um grande potencial, tendo como principal vantagem a simplicidade de aplicação. / In this work we present the study of polysilicon depletion and the gate tunneling current effects in thin-gate oxide devices. Characteristic curves of capacitance as a function of the gate voltage (C-V) were used to analyze the degradation caused for these effects. Regarding the poly depletion effect, a reduction of the total capacitance in the inversion region was verified as the polysilicon doping concentration decreases. This effect was observed in C-V curves in high and low frequency, being the last one more affected. The gate tunneling current presented an influence on the width of the depletion silicon region, which increased due to the carriers tunneling from the substrate. As a result, a reduction in the silicon capacitance was observed, causing the C-V curve reduction in the inversion region. When the polysilicon depletion effect is considered together with the tunneling effect, it was observed that there is a carriers excess in the gate region, causing a reduction of the polysilicon depletion region width. In this case, the C-V curve suffered a larger reduction, making difficult to separate both effects. The most affected characteristic was the C-V curve at low frequency, due to existence of the carrier response time that allows observing the influence of the tunneling current in inversion charges. A new method for the determination of the doping concentration of substrate and polysilicon was also presented, through C-V curves at high frequency. Two-dimensional simulations and experimental measurements were used to validate the method. The obtained results indicate that the propose method present a higher potential, having as principal advantage the simplicity of application.

Apresentamos neste trabalho um estudo do efeito da depleção do silício policristalino e da corrente de tunelamento em dispositivos com óxidos de porta finos. Utilizamos curvas características da capacitância em função da tensão de porta (C-V), para analisar a degradação causada por estes efeitos.Quanto ao efeito da depleção do silício policristalino a capacitância total na região de inversão apresenta uma redução conforme a concentração de dopantes do silício policristalino diminui. Este efeito foi observado em curvas C-V tanto de alta como de baixa freqüência, sendo esta última mais afetada. A corrente de tunelamento através do óxido de porta apresentou uma influência na largura da região de depleção no silício, que aumentou devido ao tunelamento de portadores do substrato. Como resultado, uma diminuição na capacitância do silício foi observada, fazendo a curva C-V diminuir na região de inversão. Quando considerado o efeito de depleção no silício policristalino junto com o efeito do tunelamento, observou-se que na região da porta houve um excesso de portadores, causando uma diminuição na região de depleção do silício policristalino. Neste caso a curva C-V sofreu uma maior redução, tornando-se difícil separar os dois efeitos. A curva C-V de baixa freqüência foi a mais atingida, pois como os portadores tem tempo de resposta, pode-se observar a influência da corrente de tunelamento nas cargas de inversão. Apresentamos ainda um novo método para a determinação da concentração de dopantes no substrato e no silício policristalino, através de curvas C-V de alta freqüência. Simulações numéricas bidimensionais e medidas experimentais foram utilizadas para validação do método. Os resultados obtidos indicam que o método proposto apresenta um grande potencial, tendo como principal vantagem a simplicidade de aplicação. / In this work we present the study of polysilicon depletion and the gate tunneling current effects in thin-gate oxide devices. Characteristic curves of capacitance as a function of the gate voltage (C-V) were used to analyze the degradation caused for these effects. Regarding the poly depletion effect, a reduction of the total capacitance in the inversion region was verified as the polysilicon doping concentration decreases. This effect was observed in C-V curves in high and low frequency, being the last one more affected. The gate tunneling current presented an influence on the width of the depletion silicon region, which increased due to the carriers tunneling from the substrate. As a result, a reduction in the silicon capacitance was observed, causing the C-V curve reduction in the inversion region. When the polysilicon depletion effect is considered together with the tunneling effect, it was observed that there is a carriers excess in the gate region, causing a reduction of the polysilicon depletion region width. In this case, the C-V curve suffered a larger reduction, making difficult to separate both effects. The most affected characteristic was the C-V curve at low frequency, due to existence of the carrier response time that allows observing the influence of the tunneling current in inversion charges. A new method for the determination of the doping concentration of substrate and polysilicon was also presented, through C-V curves at high frequency. Two-dimensional simulations and experimental measurements were used to validate the method. The obtained results indicate that the propose method present a higher potential, having as principal advantage the simplicity of application.

Orientador: Carlos Alberto Canesin / Resumo: No presente trabalho de dissertação, é analisado e desenvolvido um conversor ressonante com o objetivo de produzir ozônio, aplicado à água de processos de higienização industrial. Na atualidade, no ano de 2018, dois dos fatores de grande importância no desenvolvimento de conversores para geração de ozônio são: a eficiência energética, isto é, quanta energia é aproveitada em relação à energia total fornecida ao conversor, e a outra é a produção de ozônio fazendo uso dessa energia aproveitada. Os dois fatores não necessariamente estão relacionados, por exemplo, para dois conversores distintos com a mesma energia disponível, pode acontecer que em um deles possa ser produzido maiores concentrações de ozônio com um menor aproveitamento de energia. Portanto, este trabalho enfatiza a melhoria da eficiência energética na produção de ozônio, empregando comutação suave nas estruturas envolvidas do conversor ressonante proposto, o que resulta em uma eficiência energética de 91,57%. A estrutura do conversor proposto apresenta dois estágios em cascata, o primeiro deles, um conversor que é responsável por gerar um barramento CC estável de 400,5 V e que atende aos requisitos de fator de potência e distorção harmônica total com valores de 0,994 e 5,79%(para a corrente de entrada), respectivamente, e o segundo, um inversor ressonante capaz de fornecer uma tensão de 4,4 kV com uma frequência de 10 kHz que atua como fonte de alimentação de um reator conformado por câmaras de descarga usadas em ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In the present dissertation, it is studied and developed a resonant converter in order to produce ozone, applied in water treatment for cleaning processes. Currently, in the year 2018, two of the factors of great importance in the development of converters for ozone generation are: energy efficiency, that is, how much energy is used in relation to the total energy supplied to the converter, and the other is the production of ozone making use of this energy harnessed. The two factors are not necessarily related, for example, for two different converters with the same energy available, it can happen that in one of them can be produced higher concentrations of ozone with a lower use of energy. Therefore, this work emphasizes the improvement of energy efficiency in the production of ozone using soft switching in the involved structures of the proposed resonant converter, which results in an energy efficiency of 91.57%. The structure of the proposed converter has two stages in cascade, the first one, a converter that is responsible for generating a stable DC bus of 400.5 V and that meets the requirements of power factor and total harmonic distortion with values of 0.994 and 5.79% (for the input current), respectively, and the second, a resonant inverter capable of providing a voltage of 4.4 kV with a frequency of 10 kHz which acts as a power supply for a reactor formed by discharge chambers used in ozone generation applications by electric discharge. Naturally, relevant ozone info... (Complete abstract click electronic access below) / Mestre

This dissertation presents a low-power high-resolution delta-sigma ADC. Two new architectural design techniques are proposed to reduce the power dissipation of the ADC. Compared to the conventional active adder, the direct charge transfer (DCT) adder greatly saves power by keeping the feedback factor of the active adder unity. However, the inherent delay originated from the DCT adder will cause instability to the modulator and complex additional branches are usually needed to stabilize the loop. A simple and power-efficient technique is proposed to absorb the delay from the DCT adder and the instability issue is therefore solved. Another proposed low-power design technique is to feed differentiated inverted quantization noise to the input of the last integrator. The modulator noise-shaping order with this proposed technique is effectively increased from two to three without adding additional active elements. The delta-sigma ADC with the proposed architectural design techniques has been implemented in transistor-level and fabricated in 0.18 µm CMOS technology. Measurement results showed a SNDR of 99.3 dB, a DR of 101.3 dB and a SFDR of 112 dB over 20 kHz signal bandwidth, resulting in a very low figure-of-merit (FoM) in its application category. Finally, two new circuit ideas, low-power parasitic-insensitive switched-capacitor integrator for delta-sigma ADCs and switched-resistor tuning technique for highly linear Gm-C filter design are presented. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from June 9, 2012 - June 9, 2014

This dissertation presents the design and development of a mixed-signal low noise second-order integrated circuit (IC) for the open-loop and closed-loop operation of integrated capacitive micro- and nano-gravity accelerometers. The micromechanical accelerometers are fabricated in thick (less than 100 m) silicon-on-insulator (SOI) substrates. The IC provides the 1-bit digital output stream and has the versatility of interfacing sensors with different sensitivities while maintaining minimum power consumption (less than 5 mW) and maximum dynamic range (90 dB). A fully-differential sampled-data scheme is deployed with the ability of low-frequency noise reduction through the use of correlated double sampling (CDS) scheme. In this work, the measured resolution of the closed-loop CMOS-SOI accelerometer system, in the presence of high background accelerations, is in the micro-g (g: gravity) range. In this design, a second-order SC modulator is cascaded with the accelerometer and the front-end amplifier. The accelerometer operates in air and is designed for non-peaking response with a BW-3dB of 500 Hz. A 22 dB improvement in noise and hence dynamic range is achieved with a sampling clock of 40 kHz corresponding to a low oversampling ratio (OSR) of 40. The interface IC consumed a current of 1.5 mA from a supply of 3 V.

<p>In this thesis, controllers for power oscillation damping, transient stability improvement and power flow control by means of a Controlled Series Compensator (CSC) and and a Dynamic Power Flow Controller (DPFC) are proposed. These devices belong to the group of power system components referred to as Flexible AC Transmission System (FACTS) devices. The developed controllers use only quantities measured locally at the FACTS device as inputs, thereby avoiding the risk of interrupted communications associated with the use of remote signals for control.</p><p>For power systems with one dominating, poorly damped inter-area power oscillation mode, it is shown that a simple generic system model can be used as a basis for damping- and power flow control design. The model for control of CSC includes two synchronous machine models representing the two grid areas participating in the oscillation and three reactance variables, representing the interconnecting transmission lines and the FACTS device. The model for control of DPFC is of the same type but it also includes the phase shift of the internal phase-shifting transformer of the DPFC.</p><p>The key parameters of the generic grid models are adaptively set during the controller operation by estimation from the step responses in the FACTS line power to the changes in the line series reactance inserted by the FACTS device. The power oscillation damping controller is based on a time-discrete, non-linear approach which aims to damp the power oscillations and set the desired power flow on the FACTS line by means of two step changes in the line reactance separated in time by half an oscillation cycle.</p><p>A verification of the proposed controllers was done by means of digital simulations using power system models of different complexities. The CSC and DPFC controllers were shown to significantly improve the small-signal- and transient stability in one four-machine system of a type commonly used to study inter-area oscillations. The CSC controller was also tested for 18 different contingencies in a 23-machine system, resulting in an improvement in both the system transient stability and the damping of the critical oscillation mode. </p>