Desenvolvimento de um conversor estático PWM para o acionamento de LED’S para iluminação publica

This work deals with the development of a switched-mode power supply circuit based on a Buck topology converter with a Boost Rectifier One-Cycle Control with Power Factor Correction developing, thus, a source of direct current for a module of 50 power LEDs that will be used in a lamp for public street lightning. It is presented, at first, some aspects about the most common technologies used in lamps of public street lightning in Brazil and a comparison with the White LED high power, which is the one that presents itself as the most promising among the existing market. Then it is presented the detailed development of the static converter switched PWM, consisting of a Boost rectifier with power factor correction and methodology of control One-Cycle Control associated with a Buck converter controlled by a PI method that operates as a direct current source . At the end of the simulation results of the circuit through the PSIM software are presented to verify the design behavior

Desenvolvimento de estrutura para purificação de água potável, através da irradiação de UV com lâmpadas fluorescentes especiais

Pós-graduação em Engenharia Elétrica - FEIS

Análise de geradores piezelétricos acoplados com circuitos retificadores operando em regime caótico

Pós-graduação em Engenharia Mecânica - FEIS

Sistema de geração e armazenamento de energia elétrica utilizando transdutor piezelétrico na forma pulsada

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Projeto de controladores robustos para acionamento de um motor de indução trifásico

Pós-graduação em Engenharia Elétrica - FEIS

Retificador entrelaçado com elevado fator de potência para operação de um veículo trólebus alimentado por redes em CA Ou CC

This paper presents the development and the main results for an interleaved boost rectifier operating as a special input power stage for a trolleybus type vehicle, allowing its feeding by alternate current (AC) or direct current (DC) distribution power systems. When feeding with two wires (single phase) alternate current distribution system, the converter accomplish active power factor correction, providing a relatively sinusoidal current with low total harmonic distortion (THD) and fully complying with IEC 61000-3-4 standards. In addition, a management control system promotes the required automatic operation changes for the proposed rectifier when the vehicle is changing from the DC distribution power system to the AC distribution power system and vice-versa, keeping its original electrical DC system characteristics for the adjustable speed driver sub-system. The main experimental results for a prototype rated at 150kW are presented, considering its application for a trolleybus with DC adjustable speed driver, demonstrating the proposed converter benefits and the possibility of AC feeding system for trolleybus type vehicle.

Effect of parametric uncertainties on the performance of a piezoelectric energy harvesting device

The use of piezoelectric materials for the development of electromechanical devices for the harvesting or scavenging of ambient vibrations has been extensively studied over the last decade. The energy conversion from mechanical (vibratory) to electrical energy is provided by the electromechanical coupling between mechanical strains/stresses and electric charges/voltages in the piezoelectric material. The majority of the studies found in the open literature present a tip-mass cantilever piezoelectric device tuned on the operating frequency. Although recent results show that these devices can be quite effective for harvesting small amounts of electrical energy, little has been published on the robustness of these devices or on the effect of parametric uncertainties on the energy harvested. This work focuses on a cantilever plate with bonded piezoelectric patches and a tip-mass serving as an energy harvesting device. The rectifier and storage electric circuit was replaced by a resistive circuit (R). In addition, an alternative to improve the harvesting performance by adding an inductance in series to the harvesting circuit, thus leading to a resonant circuit (RL), is considered. A coupled finite element model leading to mechanical (displacements) and electrical (charges at electrodes) degrees of freedom is considered. An analysis of the effect of parametric uncertainties of the device on the electric output is performed. Piezoelectric and dielectric constants of the piezoelectric active layers and electric circuit equivalent inductance are considered as stochastic parameters. Mean and confidence intervals of the electric output are evaluated.

Parametric Sensitivity Analysis of the Most Recent Computational Models of Rabbit Cardiac Pacemaking

The cellular basis of cardiac pacemaking activity, and specifically the quantitative contributions of particular mechanisms, is still debated. Reliable computational models of sinoatrial nodal (SAN) cells may provide mechanistic insights, but competing models are built from different data sets and with different underlying assumptions. To understand quantitative differences between alternative models, we performed thorough parameter sensitivity analyses of the SAN models of Maltsev & Lakatta (2009) and Severi et al (2012). Model parameters were randomized to generate a population of cell models with different properties, simulations performed with each set of random parameters generated 14 quantitative outputs that characterized cellular activity, and regression methods were used to analyze the population behavior. Clear differences between the two models were observed at every step of the analysis. Specifically: (1) SR Ca2+ pump activity had a greater effect on SAN cell cycle length (CL) in the Maltsev model; (2) conversely, parameters describing the funny current (If) had a greater effect on CL in the Severi model; (3) changes in rapid delayed rectifier conductance (GKr) had opposite effects on action potential amplitude in the two models; (4) within the population, a greater percentage of model cells failed to exhibit action potentials in the Maltsev model (27%) compared with the Severi model (7%), implying greater robustness in the latter; (5) confirming this initial impression, bifurcation analyses indicated that smaller relative changes in GKr or Na+-K+ pump activity led to failed action potentials in the Maltsev model. Overall, the results suggest experimental tests that can distinguish between models and alternative hypotheses, and the analysis offers strategies for developing anti-arrhythmic pharmaceuticals by predicting their effect on the pacemaking activity.

Adenoviral expression of IKs contributes to wavebreak and fibrillatory conduction in neonatal rat ventricular cardiomyocyte monolayers

Previous studies have shown that the gating kinetics of the slow component of the delayed rectifier K(+) current (I(Ks)) contribute to postrepolarization refractoriness in isolated cardiomyocytes. However, the impact of such kinetics on arrhythmogenesis remains unknown. We surmised that expression of I(Ks) in rat cardiomyocyte monolayers contributes to wavebreak formation and facilitates fibrillatory conduction by promoting postrepolarization refractoriness. Optical mapping was performed in 44 rat ventricular myocyte monolayers infected with an adenovirus carrying the genomic sequences of KvLQT1 and minK (molecular correlates of I(Ks)) and 41 littermate controls infected with a GFP adenovirus. Repetitive bipolar stimulation was applied at increasing frequencies, starting at 1 Hz until loss of 1:1 capture or initiation of reentry. Action potential duration (APD) was significantly shorter in I(Ks)-infected monolayers than in controls at 1 to 3 Hz (P<0.05), whereas differences at higher pacing frequencies did not reach statistical significance. Stable rotors occurred in both groups, with significantly higher rotation frequencies, lower conduction velocities, and shorter action potentials in the I(Ks) group. Wavelengths in the latter were significantly shorter than in controls at all rotation frequencies. Wavebreaks leading to fibrillatory conduction occurred in 45% of the I(Ks) reentry episodes but in none of the controls. Moreover, the density of wavebreaks increased with time as long as a stable source sustained the fibrillatory activity. These results provide the first demonstration that I(Ks)-mediated postrepolarization refractoriness can promote wavebreak formation and fibrillatory conduction during pacing and sustained reentry and may have important implications in tachyarrhythmias.

The Electrodeposition of Iron-Manganese Alloys

An electrodeposition of an iron-manganese alloy was made from the same conditions determined by previous re­search. Various addition agents were experimented with in an attempt to produce better conditions for electro-deposition. It was found advantageous to add small a­mounts of sodium lauryl sulfate and ammonium sulfite to the electrolyte.

Convergent and divergent modulatory pathways in {\it Aplysia\/}: Cellular and network studies

Neuromodulation is essential to many functions of the nervous system. In the simple gastropod mollusk Aplysia californica, neuromodulation of the circuits for the defensive withdrawal reflexes has been associated with several forms of learning. In the present work, the neurotransmitters and neural circuitry which contribute to the modulation of the tail-siphon withdrawal reflex were examined.^ A recently-identified neuropeptide transmitter, buccalin A was found to modulate the biophysical properties of the sensory neurons that mediate the reflex. The actions of buccalin A on the sensory neurons were compared with those of the well-characterized modulatory transmitter serotonin, and convergence and divergence in the actions of these two transmitters were evaluated. Buccalin A dramatically increased the excitability of sensory neurons and occluded further enhancement of excitability by serotonin. Buccalin A produced no significant change in spike duration, and it did not block serotonin-induced spike broadening. Voltage-clamp analysis revealed the currents that may be involved in the effects on spike duration and excitability. Buccalin A decreased an outward current similar to the S-K$\sp+$ current (I$\sb{\rm K,S}$). Buccalin A appeared to occlude further modulation of I$\sb{\rm K,S}$ by serotonin, but did not block serotonin-induced modulation of the voltage-dependent delayed rectifier K$\sp+$ current (I$\sb{\rm K,V}$). These results suggest that buccalin A converges on some, but not all, of the same subcellular modulatory pathways as serotonin.^ In order to begin to understand neuromodulation in a more physiological context for the tail-siphon withdrawal reflex, the modulatory circuitry for the tail-withdrawal circuit was examined. Mechanoafferent neurons in the J cluster of the cerebral ganglion were identified as elements of a modulatory circuit for the reflex. Excitatory and inhibitory connections were observed between the J cells and the pleural sensory neurons, the tail motor neurons, and several classes of interneurons for the tail-siphon withdrawal circuit. The J cells produced both fast and slow PSPs in these neurons. Of particular interest was the ability of the J cells to produce slow EPSPs in the pleural sensory neurons. These slow EPSPs were associated with an increase in the excitability of the sensory neurons. The J cells appear to mediate both sensory and modulatory inputs to the circuit for the tail-siphon withdrawal reflex from the anterior part of the animal. ^

Simulación, construcción y medida de un sistema de telealimentación eficiente

Los sistemas de telealimentación han tomado gran importancia en diferentes campos, incluido el de las telecomunicaciones, algunos ejemplos pueden ser: En la red conmutada telefónica junto con la señal de información y llamada existe una alimentación de 48v que se transmite a través de toda la línea de transmisión hasta los terminales. En algunos ferrocarriles eléctricos, se aprovecha la producción de energía eléctrica cuando un tren baja una cuesta y el motor funciona como generador, devolviendo la energía excedente a la propia catenaria por medio de superposición, y siendo esta recuperada en otro lugar y aprovechada por ejemplo por otro tren que requiere energía. Otro uso en ferrocarriles de la telealimentación es la llamada "tecnología del transpondedor magnético", en la que el tren transmite a las balizas una señal en 27MHz además de otras de información propias, que se convierte en energía útil para estas balizas. En este proyecto pretendemos implementar un pequeño ejemplo de sistema de telealimentación trabajando en 5 MHz (RF). Este sistema transforma una señal de CC en una señal de potencia de CA que podría ser, por ejemplo, transmitida a lo largo de una línea de transmisión o radiada por medio de una antena. Después, en el extremo receptor, esta señal RF se transforma finalmente en DC. El objetivo es lograr el mejor rendimiento de conversión de energía, DC a AC y AC a DC. El sistema se divide en dos partes: El inversor, que es la cadena de conversión DC-AC y el rectificador, que es la cadena de conversión AC-DC. Cada parte va a ser calculada, simulada, implementada físicamente y medida aparte. Finalmente el sistema de telealimentación completo se va a medir mediante la interconexión de cada parte por medio de un adaptador o una línea de transmisión. Por último, se mostrarán los resultados obtenidos. ABSTRACT. Remote powering systems have become very important in different fields, including telecommunications, some examples include: In the switched telephone network with the information signal and call there is a 48v supply that is transmitted across the transmission line to the terminals. In some electric railways, the production of electrical energy is used when a train is coming down a hill and the motor acts as a generator, returning the surplus energy to the catenary itself by overlapping, and this being recovered elsewhere and used by other train. Home TV amplifiers that are located in places (storage, remote locations ..) where there is no outlet, remote power allows to carry information and power signal by the same physical medium, for instance a coax. The AC power signal is transformed into DC at the end to feed the amplifier. In medicine, photovoltaic converters and fiber optics can be used as means for feeding devices implanted in patients. Another use of the remote powering systems on railways is the "magnetic transponder technology", in which the station transmits a beacon signal at 27MHz own as well as other information, which is converted into useful energy to these beacons. In this Project we are pretending to implement a little example of remote powering system working in 5 MHz (RF). This system transform DC into an AC-RF power signal which could be, for instance, transmitted throughout a transmission line or radiated by means of an aerial. At the receiving end, this RF signal is then transformed to DC. The objective is to achieve the best power conversion performance, DC to AC and AC to DC. The system is divided in two parts: The inverter, that is the DC-AC conversion chain and the rectifier that is the AC-DC conversion chain. Each part is going to be calculated, simulated, implemented physically and measured apart. Then the complete remote-powering system is to be measured by interconnecting each part by means of a interconnector or a transmission line. Finally, obtained results will be shown.

Development and improvement of protection-system algorithms for ground-fault detection and location in synchronous machines

Uno de los defectos más frecuentes en los generadores síncronos son los defectos a tierra tanto en el devanado estatórico, como de excitación. Se produce un defecto cuando el aislamiento eléctrico entre las partes activas de cualquiera de estos devanados y tierra se reduce considerablemente o desaparece. La detección de los defectos a tierra en ambos devanados es un tema ampliamente estudiado a nivel industrial. Tras la detección y confirmación de la existencia del defecto, dicha falta debe ser localizada a lo largo del devanado para su reparación, para lo que habitualmente el rotor debe ser extraído del estator. Esta operación resulta especialmente compleja y cara. Además, el hecho de limitar la corriente de defecto en ambos devanados provoca que el defecto no sea localizable visualmente, pues apenas existe daño en el generador. Por ello, se deben aplicar técnicas muy laboriosas para localizar exactamente el defecto y poder así reparar el devanado. De cara a reducir el tiempo de reparación, y con ello el tiempo en que el generador esta fuera de servicio, cualquier información por parte del relé de protección acerca de la localización del defecto resultaría de gran utilidad. El principal objetivo de esta tesis doctoral ha sido el desarrollo de nuevos algoritmos que permitan la estimación de la localización de los defectos a tierra tanto en el devanado rotórico como estatórico de máquinas síncronas. Respecto al devanado de excitación, se ha presentado un nuevo método de localización de defectos a tierra para generadores con excitación estática. Este método permite incluso distinguir si el defecto se ha producido en el devanado de excitación, o en cualquiera de los componentes del sistema de excitación, esto es, transformador de excitación, conductores de alimentación del rectificador controlado, etc. En caso de defecto a tierra en del devanado rotórico, este método proporciona una estimación de su localización. Sin embargo, para poder obtener la localización del defecto, se precisa conocer el valor de resistencia de defecto. Por ello, en este trabajo se presenta además un nuevo método para la estimación de este parámetro de forma precisa. Finalmente, se presenta un nuevo método de detección de defectos a tierra, basado en el criterio direccional, que complementa el método de localización, permitiendo tener en cuenta la influencia de las capacidades a tierra del sistema. Estas capacidades resultan determinantes a la hora de localizar el defecto de forma adecuada. En relación con el devanado estatórico, en esta tesis doctoral se presenta un nuevo algoritmo de localización de defectos a tierra para generadores que dispongan de la protección de faltas a tierra basada en la inyección de baja frecuencia. Se ha propuesto un método general, que tiene en cuenta todos los parámetros del sistema, así como una versión simplificada del método para generadores con capacidades a tierra muy reducida, que podría resultar de fácil implementación en relés de protección comercial. Los algoritmos y métodos presentados se han validado mediante ensayos experimentales en un generador de laboratorio de 5 kVA, así como en un generador comercial de 106 MVA con resultados satisfactorios y prometedores. ABSTRACT One of the most common faults in synchronous generators is the ground fault in both the stator winding and the excitation winding. In case of fault, the insulation level between the active part of any of these windings and ground lowers considerably, or even disappears. The detection of ground faults in both windings is a very researched topic. The fault current is typically limited intentionally to a reduced level. This allows to detect easily the ground faults, and therefore to avoid damage in the generator. After the detection and confirmation of the existence of a ground fault, it should be located along the winding in order to repair of the machine. Then, the rotor has to be extracted, which is a very complex and expensive operation. Moreover, the fact of limiting the fault current makes that the insulation failure is not visually detectable, because there is no visible damage in the generator. Therefore, some laborious techniques have to apply to locate accurately the fault. In order to reduce the repair time, and therefore the time that the generator is out of service, any information about the approximate location of the fault would be very useful. The main objective of this doctoral thesis has been the development of new algorithms and methods to estimate the location of ground faults in the stator and in the rotor winding of synchronous generators. Regarding the excitation winding, a new location method of ground faults in excitation winding of synchronous machines with static excitation has been presented. This method allows even to detect if the fault is at the excitation winding, or in any other component of the excitation system: controlled rectifier, excitation transformer, etc. In case of ground fault in the rotor winding, this method provides an estimation of the fault location. However, in order to calculate the location, the value of fault resistance is necessary. Therefore, a new fault-resistance estimation algorithm is presented in this text. Finally, a new fault detection algorithm based on directional criterion is described to complement the fault location method. This algorithm takes into account the influence of the capacitance-to-ground of the system, which has a remarkable impact in the accuracy of the fault location. Regarding the stator winding, a new fault-location algorithm has been presented for stator winding of synchronous generators. This algorithm is applicable to generators with ground-fault protection based in low-frequency injection. A general algorithm, which takes every parameter of the system into account, has been presented. Moreover, a simplified version of the algorithm has been proposed for generators with especially low value of capacitance to ground. This simplified algorithm might be easily implementable in protective relays. The proposed methods and algorithms have been tested in a 5 kVA laboratory generator, as well as in a 106 MVA synchronous generator with satisfactory and promising results.

Transferencia inalámbrica de energía

El trabajo presentado en este documento se centra en la temática de la transferencia inalámbrica de energía, concretamente en aplicaciones de campo lejano, para llevar a cabo dicho trabajo nos centraremos en el diseño, implementación y medición de una rectenna operando en la banda ISM concretamente a una frecuencia de 2.45GHz, el objetivo primordial de este trabajo será analizar que parámetros intervienen en la eficiencia de conversión en la etapa de RF-DC a fin de lograr la máxima eficiencia de conversión posible. Para llevar a cabo dicho análisis se emplearán herramientas informáticas, concretamente se hará uso del software AWR Microwave Office, a través del cual se realizarán simulaciones SourcePull a fin de determinar la impedancia óptima de entrada que se le debe presentar a la etapa rectificadora RF-DC para conseguir la máxima eficiencia de conversión, una vez realizadas dichas pruebas se implementará físicamente un circuito rectenna a través del cual realizar medidas de SourcePull mediante un Wide Matching Range Slide Screw Tuner de MAURY MICROWAVE para cotejar las posibles diferencias con los resultados obtenidos en las simulaciones. Tras la fase de pruebas SourcePull se extrapolará una red de entrada en base a los datos obtenidos en las mediciones anteriores y se diseñará y fabricará un circuito rectenna con máxima eficiencia de conversión para un conjunto de valores de potencia de entrada de RF y carga de DC, tras lo cual se analizará la eficiencia del circuito diseñado para diferentes valores de potencia de RF de entrada y carga de DC. Como elemento rectificador emplearemos en nuestro trabajo el diodo Schottky HSMS-2820, los diodos Schottky se caracterizan por tener tiempos de conmutación relativamente bajos y pérdidas en directa reducidas los cual será fundamental a la hora de trabajar con niveles reducidos de potencia de RF de entrada, para implementar el circuito se empleará un substrato FR4 con espesor de 0.8mm para disminuir en la mayor medida posible las pérdidas introducidas por el dieléctrico, se analizarán diferentes posibilidades a la hora de implementar el filtro de RF a la salida del diodo rectificador y finalmente se optará por el empleo de un stub radial ya que será este el que mejor ancho de banda nos proporcione. Los resultados simulados se compararán con los resultados medidos sobre el circuito rectenna para determinar la similitud entre ambos. ABSTRACT. The work presented in this paper focuses on the issue of wireless transfer of energy, particularly applied to far-field applications, to carry out this work we focus on the design, implementation and measurement of a rectenna operating in the ISM band specifically at a frequency of 2.45GHz, the primary objective of this study is to analyze any parameter involved in the RF-DC conversion efficiency in order to achieve the maximum conversion efficiency as possible. Computer analysis tools will be used, particularly AWR Microwave Office software, in order to carry out SourcePull simulations to determine the optimal input impedance which must be presented to the rectifier stage for maximum conversion efficiency, once obtained, a rectenna circuit will be implemented to compute SourcePull measurements, and finally simulated results will be compared to measured results. Once obtained the result, an input network impedance is extrapolated based on data from previous measurements to design and implement a rectenna circuit with high conversion efficiency for a set of RF input power and DC load values , after that, the designed circuit efficiency will be analyzed for different values of RF input power and DC load. In this work a HSMS-2820 Schottky diode will be used as the rectifier , Schottky diodes are characterized by relatively low switching times and reduced direct losses, that properties will be essential when working with low RF input power levels , to implement the circuit a FR4 substrate with 0.8mm thickness is used to reduce as much as possible the dielectric losses, different possibilities to implement the RF filter to the output of the rectifier diode will be analyzed, finally we will opt for the use of a radial stub as this will provide the best bandwidth possible. The simulated results are compared with the results measured on the rectenna circuit to determine the similarity between them.

A Wireless Charging System Applying Phase-Shift and Amplitude Control to Maximize Efficiency and Extractable Power

Wireless power transfer (WPT) is an emerging technology with an increasing number of potential applications to transfer power from a transmitter to a mobile receiver over a relatively large air gap. However, its widespread application is hampered due to the relatively low efficiency of current Wireless power transfer (WPT) systems. This study presents a concept to maximize the efficiency as well as to increase the amount of extractable power of a WPT system operating in nonresonant operation. The proposed method is based on actively modifying the equivalent secondary-side load impedance by controlling the phase-shift of the active rectifier and its output voltage level. The presented hardware prototype represents a complete wireless charging system, including a dc-dc converter which is used to charge a battery at the output of the system. Experimental results are shown for the proposed concept in comparison to a conventional synchronous rectification approach. The presented optimization method clearly outperforms state-of-the-art solutions in terms of efficiency and extractable power.