Mnltiloop Controller and Reference Generator for a Dynamic Voltage Restorer Implementation

This paper deals with the design and analysis of a Dynamic Voltage Restorer output voltage control. Such control is based on a multiloop strategy, with an inner current PID regulator and an outer P+Resonant voltage controller. The inner regulator is applied on the output inductor current. It will be also demonstrated how the load current behavior may influence in the DVR output voltage, which. justifies the need for the resonant controller. Additionally, it will be discussed the application of a modified algorithm for the identification of the DVR voltage references, which is based on a previously presented positive sequence detector. Since the studied three-phase DVR is assumed to be based on three identical H-bridge converters, all the analysis and design procedures were realized by means of single-phase equivalent circuits. The discussions and conclusions are supported by theoretical calculations, nonlinear simulations and some experimental results.

Corrosion protection of stainless steel by polysiloxane hybrid coatings prepared using the sol-gel process

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Dynamic behavior of a linear induction motor

Although conventional rotating machines have been largely used to drive underground transportation systems, linear induction motors are also being considered for future applications owing to their indisputable advantages. A mathematical model for the transient behavior analysis of linear induction motors, when operating with constant r.m.s. currents, is presented in this paper. Operating conditions, like phase short-circuit and input frequency variations and also some design characteristics, such as air-gap and secondary resistivity variations, can be considered by means of this modeling. The basis of the mathematical modeling is presented. Experimental results obtained in the laboratory are compared with the corresponding simulations and discussed in this paper.

An improved design procedure for LCC resonant filter of dimmable electronic ballasts for fluorescent lamps, based on lamp model

This paper presents an improved design methodology for the determination of the parameters used in the classical series-resonant parallel-loaded (SRPL) filter employed in the switching frequency controlled dimmable electronic ballasts. According to the analysis developed in this paper, it is possible to evaluate some important characteristics of the resonant filter during the dimming operation, such as: range of switching frequency, phase shift, and rms value of the current drained by the resonant filter + fluorescent lamp set. Experimental results are presented in order to validate the analyses developed in this paper. © 2005 IEEE.

Multiloop controller and reference generator for a dynamic voltage restorer implementation

This paper deals with the design and analysis of a Dynamic Voltage Restorer output voltage control. Such control is based on a multiloop strategy, with an inner current PID regulator and an outer P+Resonant voltage controller. The inner regulator is applied on the output inductor current. It will be also demonstrated how the load current behavior may influence in the DVR output voltage, which justifies the need for the resonant controller. Additionally, it will be discussed the application of a modified algorithm for the identification of the DVR voltage references, which is based on a previously presented positive sequence detector. Since the studied three-phase DVR is assumed to be based on three identical H-bridge converters, all the analysis and design procedures were realized by means of single-phase equivalent circuits. The discussions and conclusions are supported by theoretical calculations, nonlinear simulations and some experimental results. ©2008 IEEE.

Caracterização dielétrica de partículas nanométricas e nanoestruturadas de óxido de niobato da família tetragonal tungstênio bronze com estequiometria K'Sr IND. 2' N'b IND. 5' 'O IND. 15'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da fotocapacitância em dispositivos MIS orgânicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Espectroscopia de impedância em soluções iônicas e mistura de etanol/água

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Microstructural and electrochemical characterization of friction stir welded duplex stainless steels

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desenvolvimento e aplicação de microplumas para tratamento de politereftalato de etileno (PET)

Pós-graduação em Engenharia Mecânica - FEG

Flashover phenomenon: an analysis with influence of the thickness of the layer pollution of the high voltage polluted insulators

Results of the analysis of dynamic behavior of flashover phenomenon on the high voltage-polluted insulators are presented. These results were taken from a mathematical and an experimental model that introduce the variable thickness influence of the layer pollution deposited on the high-voltage insulator surface. Analysis of the flashover was done by way of introducing a variation in the thickness of the channel of Obenaus' model, simulating a layer pollution of variable thickness. The objective was to obtain a better reproduction of the real layer pollution deposited on the insulator that works in the polluted regions. Two types of thickness variations were used: a sudden variation, using a step; and a soft variation, using a ramp; that were put along the way of the discharge. Comparison between the mathematical and experimental models showed that introduction of a ramp makes Obenaus' model more efficient in analyzing behavior of flashover phenomenon.

Fabrication, Electrical Characterization and Simulation of Thin Film Solar Cells: CdTe and CIGS Materials

CdTe and Cu(In,Ga)Se2 (CIGS) thin film solar cells are fabricated, electrically characterized and modelled in this thesis. We start from the fabrication of CdTe thin film devices where the R.F. magnetron sputtering system is used to deposit the CdS/CdTe based solar cells. The chlorine post-growth treatment is modified in order to uniformly cover the cell surface and reduce the probability of pinholes and shunting pathways creation which, in turn, reduces the series resistance. The deionized water etching is proposed, for the first time, as the simplest solution to optimize the effect of shunt resistance, stability and metal-semiconductor inter-diffusion at the back contact. In continue, oxygen incorporation is proposed while CdTe layer deposition. This technique has been rarely examined through R.F sputtering deposition of such devices. The above experiments are characterized electrically and optically by current-voltage characterization, scanning electron microscopy, x-ray diffraction and optical spectroscopy. Furthermore, for the first time, the degradation rate of CdTe devices over time is numerically simulated through AMPS and SCAPS simulators. It is proposed that the instability of electrical parameters is coupled with the material properties and external stresses (bias, temperature and illumination). Then, CIGS materials are simulated and characterized by several techniques such as surface photovoltage spectroscopy is used (as a novel idea) to extract the band gap of graded band gap CIGS layers, surface or bulk defect states. The surface roughness is scanned by atomic force microscopy on nanometre scale to obtain the surface topography of the film. The modified equivalent circuits are proposed and the band gap graded profiles are simulated by AMPS simulator and several graded profiles are examined in order to optimize their thickness, grading strength and electrical parameters. Furthermore, the transport mechanisms and Auger generation phenomenon are modelled in CIGS devices.

Modeling multiple state electrostatically formed nanowire transistors

The present thesis work proposes a new physical equivalent circuit model for a recently proposed semiconductor transistor, a 2-drain MSET (Multiple State Electrostatically Formed Nanowire Transistor). It presents a new software-based experimental setup that has been developed for carrying out numerical simulations on the device and on equivalent circuits. As of 2015, we have already approached the scaling limits of the ubiquitous CMOS technology that has been in the forefront of mainstream technological advancement, so many researchers are exploring different ideas in the realm of electrical devices for logical applications, among them MSET transistors. The idea that underlies MSETs is that a single multiple-terminal device could replace many traditional transistors. In particular a 2-drain MSET is akin to a silicon multiplexer, consisting in a Junction FET with independent gates, but with a split drain, so that a voltage-controlled conductive path can connect either of the drains to the source. The first chapter of this work presents the theory of classical JFETs and its common equivalent circuit models. The physical model and its derivation are presented, the current state of equivalent circuits for the JFET is discussed. A physical model of a JFET with two independent gates has been developed, deriving it from previous results, and is presented at the end of the chapter. A review of the characteristics of MSET device is shown in chapter 2. In this chapter, the proposed physical model and its formulation are presented. A listing for the SPICE model was attached as an appendix at the end of this document. Chapter 3 concerns the results of the numerical simulations on the device. At first the research for a suitable geometry is discussed and then comparisons between results from finite-elements simulations and equivalent circuit runs are made. Where points of challenging divergence were found between the two numerical results, the relevant physical processes are discussed. In the fourth chapter the experimental setup is discussed. The GUI-based environments that allow to explore the four-dimensional solution space and to analyze the physical variables inside the device are described. It is shown how this software project has been structured to overcome technical challenges in structuring multiple simulations in sequence, and to provide for a flexible platform for future research in the field.

New method for analytical photovoltaic parameter extraction

Correct modeling of the equivalent circuits regarding solar cell and panels is today an essential tool for power optimization. However, the parameter extraction of those circuits is still a quite difficult task that normally requires both experimental data and calculation procedures, generally not available to the normal user. This paper presents a new analytical method that easily calculates the equivalent circuit parameters from the data that manufacturers usually provide. The analytical approximation is based on a new methodology, since methods developed until now to obtain the aforementioned equivalent circuit parameters from manufacturer's data have always been numerical or heuristic. Results from the present method are as accurate as the ones resulting from other more complex (numerical) existing methods in terms of calculation process and resources.

Circuitos equivalentes en bandas milimétricas

The use of ideal equivalent circuits which represent the electrical response of a physical device is a very common practice in microwave and millimeter wave circuit design. However, these equivalent circuit models only get accurate results in a certain frequency range. In this document, some basic devices have been analyzed, with several equivalent circuit models for each one. Physical devices have been manufactured and measured, and measurements have been compared with the responses obtained from the equivalent models. From this comparison, it?s possible to see what equivalent models are more advisable in each case and which are their limitations.