Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-02-05T17:06:52Z No. of bitstreams: 1 guilhermemarciosoares.pdf: 5349685 bytes, checksum: 1085aed638a3213e03844d5e5e68f7d1 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-02-26T11:52:22Z (GMT) No. of bitstreams: 1 guilhermemarciosoares.pdf: 5349685 bytes, checksum: 1085aed638a3213e03844d5e5e68f7d1 (MD5) / Made available in DSpace on 2016-02-26T11:52:22Z (GMT). No. of bitstreams: 1 guilhermemarciosoares.pdf: 5349685 bytes, checksum: 1085aed638a3213e03844d5e5e68f7d1 (MD5) Previous issue date: 2014-06-25 / Este trabalho propõe um sistema inteligente de iluminação pública utilizando diodos emissores de luz (LEDs). Neste âmbito, é proposta uma topologia para o acionamento dos LEDs com controle de intensidade luminosa. Além disso, funções adicionais são propostas de modo a expandir o conjunto de funcionalidades da luminária. Para o acionamento dos LEDs foi desenvolvido um conversor baseado na topologia Ćuk operando em modo de condução descontínuo (DCM) com um interruptor estático em série com a carga, sendo uma solução para o acionamento de LEDs de estágio único. Deste modo, este conversor foi projetado para desempenhar simultaneamente as funções de correção do fator de potência e controle da potência na carga. Através da análise da resposta fotométrica dos diodos emissores de luz perante ondulações de baixa frequência em sua corrente, foi possível criar uma metodologia de projeto que evita o uso de capacitores eletrolíticos no circuito de acionamento dos LEDs, aumentando assim a confiabilidade do sistema. A modelagem e o controle do conversor também foram feitas e estão mostradas no trabalho. De modo a controlar e gerenciar o sistema eletrônico da luminária, foi proposta uma arquitetura baseada no microcontrolador TM4C123GE6PM. Este sistema digital é responsável ainda por promover outras funcionalidades como controle automático de intensidade luminosa, proteção do circuito e ainda monitoramento de parâmetros de qualidade de energia da tensão de entrada do conversor, tais como afundamentos e elevações. A fim de avaliar experimentalmente o sistema proposto, foram desenvolvidos um programa de computador capaz de gerenciar as funcionalidades da luminária e um protótipo de 70W deste equipamento. Os resultados experimentais obtidos mostraram um bom desempenho tanto do circuito de acionamento dos LEDs, como das funcionalidades da luminária. / This paper proposes a smart lighting system based on light-emitting diodes (LEDs) for street lighting applications. In this context, a power converter with dimming capability was designed. Furthermore, additional functions are proposed in order to expand the feature set of the luminaire. To drive the LEDs, a topology based on Ćuk converter operating in discontinuous conduction mode (DCM) with an electronic switch in series with the load was proposed. This converter was designed to perform simultaneously the functions of power factor correction and power control, being a single-stage LED driver solution. By analyzing the LEDs photometric response due to low-frequency current ripple, a design methodology that avoids the use of electrolytic capacitors in the proposed converter was developed. The modeling and control of the converter were also done in order to ensure that the system is always operating within the desired specifications. To control and manage the electronic system of the luminaire, it was developed an architecture based on the microcontroller TM4C123GE6PM. Beside the aforementioned functions, this digital system was designed aiming the promotion of other features, such as automatic dimming, protection of the driver and even monitoring some power quality parameters related to the input voltage, such as sags and swells. In order to experimentally evaluate the proposed system, a software, able to manage the luminaire functionalities, and a 70W prototype were built. The experimental results demonstrated a good performance of the LED driver as well as the functionalities of the proposed luminaire.

Three-level diode-clamped inverter is being widely used these days. Extensive research has been carried out on pulse width modulation (PWM) strategies for a three-level inverter. The most widely used PWM strategies are sine-triangle pulse width modulation (SPWM) and centered space vector pulse width modulation (CSVPWM). The influence of these PWM strategies on the DC-link capacitor current and voltage ripple is studied in this thesis. The sizing of the DC capacitor depends on value of the maximum RMS current flowing through it. In this work, an analytical expression for capacitor RMS current is derived as a function of operating conditions like modulation index, power factor angle of the load and peak load current. The worst case current stress on the capacitor is evaluated using the analytical expression. The capacitor RMS current is found to be the same in SPWM and CSVPWM schemes. The analytical expression is validated through simulations and experiments on a 3kVA MOSFET based three-level inverter. Harmonic analysis of the capacitor current is helpful in better evaluation of capacitor power loss. Therefore, harmonic analysis of the capacitor current is carried out, using the techniques of geometric wall model and double Fourier integral for SPWM and CSVPWM schemes. The theoretical predictions are validated through experiments. The capacitor RMS current is divided into low-frequency RMS current (where low frequency component is defined as a component whose frequency is less than half the switching frequency) and high-frequency RMS current. The capacitor voltage ripple is estimated analytically for SPWM and CSVPWM schemes, using the low-frequency and high-frequency capacitor RMS current. The voltage ripples due to SPWM and CSVPWM schemes are compared. It is found that the voltage ripple with SPWM is higher than that with CSVPWM. A simplified method to estimate the capacitor power loss, without the requirement of FFT analysis of capacitor current, is proposed. The results from this simplified method agree reasonably well with the results from the detailed method. A space vector based modulation scheme is proposed, which reduces the capacitor RMS current at high power factor angles. However, the proposed method leads to higher total harmonic distortion (THD) than CSVPWM. Simulation and experimental results, comparing CSVPWM and the proposed PWM, are presented.

Indiana University-Purdue University Indianapolis (IUPUI) / This research proposes state-of-the-art multilevel converter topologies and their modulation strategies, the implementation of a conventional flying-capacitor converter topology up to four-level, and a new four-level flying-capacitor H-Bridge converter confi guration. The three phase version of this proposed four-level flying-capacitor H-Bridge converter is given as well in this study. The highlighted advantages of the proposed converter are as following: (1) the same blocking voltage for all switches employed in the con figuration, (2) no capacitor midpoint connection is needed, (3) reduced number of passive elements as compared to the conventional solution, (4) reduced total dc source value by comparison with the conventional topology. The proposed four-level capacitor-clamped H-Bridge converter can be utilized as a multilevel inverter application in an electri fied railway system, or in hybrid electric vehicles. In addition to the implementation of the proposed topology in this research, its experimental setup has been designed to validate the simulation results of the given converter topologies.