In this thesis, MEMS switches actuated using electrostatic actuation is explored. MEMS switches that are lateral switches and clamped-clamped switches are designed, fabricated, and tested in this thesis. This thesis extensively explains the process by which the MEMS Switches were designed and fabricated. In addition, it explains the changes in the switches when issues called for a modification to devices. Contact resistances were extensively studied, in this thesis. There has been a trade-off between the reliability of switches and their contact resistances. Many actions were taken to mitigate this trade-off and to allow both reliable devices with low contact resistances. The efforts to do so ranged from thermal oxidation to reduce the scalloping on the sidewalls, to modifying the dry etching recipe, to modifying the sputtering recipe, to electroplating, and many more. However, reliability of the MEMS Lateral switches was accomplished independent to the contact resistances. In addition, low contact resistances were accomplished independent to reliability. A novel approach to designing clamped-clamped MEMS switches is also showcased in this thesis. These devices experienced unique challenges compared to those faced with lateral switches. Both lateral and clamped-clamped switches are discussed in-depth in this thesis. / Master of Science

In the oil and gas industry, brownfield projects focus on the modification of or addition to an existing production facility that is fully operational and operating. Welding is typically avoided on these projects. The drilling of holes in existing primary structural elements is also prohibited. Clamped connections are often used when adding additional services in a brownfield project. There are different types of clamped connections utilized when a new structural support must be attached to an existing vertical structural pipe. The short bolt clamped connection is a well-established connection and typically used on offshore projects. The U-bolt clamped connection is an alternative connection, although its use in the offshore oil and gas industry is not as well documented. The main drawback to using the U-bolt clamp connection is the lack of a well researched and vetted design methodology. A preliminary analysis methodology is proposed in this thesis. The material, fabrication, installation, and maintenance of both the short bolt connection and U-bolt connection will also be discussed. The following thesis will end with recommendations for moving forward.

For an Electrical Vehicle, the power is delivered from the battery pack to the electric motor through the use of power converter. Many research projects have been conducted in improving the efficiency of traction inverters. Inverter topologies are categorized based on the number of voltage levels of the inverter output phase voltage. The conventional 2-level Voltage Source Inverter (VSI) is commonly used as a traction inverter due to its simple structure. Due to the recent trend in utilizing higher DClink voltage in traction motor drives to achieve a higher power rating, multi-level inverters are gaining attention to replace the conventional VSI in EV powertrain. Multi-level voltage source inverters (MLVSI) have been widely adopted in high-power converters and medium-voltage drives. There are four major categories of MLVSI: the Flying Capacitor (FC), Neutral Point Clamped (NPC), Cascaded and Hybrid. The power rating of the MLVSI increases with the increase of inverter levels, but the size, number of switching devices, cost and control difficulty also increases. Due to the above reasons, 3-level NPC can be a good solution for traction inverters. Due to the structure and control limitation, Diode Clamp NPC suffers from uneven loss distribution and neutral point voltage balancing issues. This issue can be resolved with Active Clamped NPC (ANPC). In this thesis, the design, simulation, prototyping and testing of a 70kw 3-level ANPC traction is introduced. / Thesis / Master of Science (MSc)

(This thesis consists of two parts.) Part I Comparison of Traveling Wave and Gain-Clamped Semiconductor Optical Amplifiers. Today's Wavelength Division Multiplexing (WDM) optical networks are getting dynamic light-path reconfigurable and optical transparent. Optical amplification without optoelectronic conversion is a key technology in all-optical networks. semiconductor optical amplifier (SOA) is a very potential device in this field. Besides the linear amplification, the nonlinear features of SOA make it has a broad application in wavelength conversion, tunable wavelength filter, optical switching and optical logic. The simple structure and very compact size of SOA indicate the essential low-cost and compatibility of integration. Resonant cavity is the basic structure of conventional SOAs, while gain-clamped SOAs (GC-SOAs) provide a constant gain which raises a lot of interests in applications. SOA with Distributed Bragg Reflectors (DBR) is one of the structures to realize the clamped gain. In this thesis the performances of traveling wave SOA (TW-SOA) and DBR-SOA are compared through a dynamic model. This model consists of a distributed feedback wave equation, a carrier rate equation and a material gain model, thereby can be used to simulate both of the two SOAs. To balance the time cost of simulation and the accuracy of the result, three important non-physical parameters, simulated bandwidth, cavity discritization and frequency discretizaiton, are investigated. The simulation results show that DBR-SOA has a very stable device gain which is independent on input optical power. From a noise level point of view DBR-SOA and TW-SOA have different characteristics. These comparison is conducted with both large signal input and small signal input. In addition, a desirable application, SOA in a multi-channel WDM system, is also simulated with GC-SOA and TW-SOA. The Bit Error Rate (BER) of TW-SOA increases greatly due to inter-channel cross talk, while the BER of GC-SOA is virtually constant with the variation of WDM channel number. Another application, wavelength converter, shows TW-SOA is very useful in non-linear application. Part II Impact of Dispersion on Hybrid of Frequency-Hopped Optical CDMA and WDMA Networks. A new analytical formula for analysis of the system performance of the Hybrid of Wavelength Division Multiple Access (WDMA) and Code Division Multiple Access (CDMA) is developed and presented. The effects of fiber dispersion and inter-channel crosstalk are considered and their impact on system performance is analyzed in terms of power penalty. Finally, methods to overcome the effects of the fiber dispersion are discussed. / Thesis / Master of Applied Science (MASc)

Improving the quality factor of the mechanical oscillations of micron scale beams in a viscous fluid, such as water, is an open challenge of direct relevance to the development of future technologies. We study the stochastic dynamics of doubly-clamped micron scale beams in a viscous fluid driven by Brownian motion. We use a thermodynamic approach to compute the equilibrium fluctuations in beam displacement that requires only deterministic calculations. From calculations of the autocorrelations and noise spectra we quantify the beam dynamics by the quality factor and resonant frequency of the fundamental flexural mode over a range of experimentally accessible geometries. We carefully study the effects of the grid resolution, domain size, linear response, and time-step for the numerical simulations. We consider beams with uniform rectangular cross-section and explore the increased quality factor and resonant frequency as a baseline geometry is varied by increasing the width, increasing the thickness, and decreasing the length. The quality factor is nearly doubled by tripling either the width or the height of the beam. Much larger improvements are found by decreasing the beam length, however this is limited by the appearance of additional modes of dissipation. Overall, the stochastic dynamics of the wider and thicker beams are well predicted by a two-dimensional approximate theory beyond what may be expected based upon the underlying assumptions, whereas the shorter beams require a more detailed analysis. / Master of Science

Las topologías de convertidores multinivel han recibido una atención especial durante las dos últimas décadas debido a sus notables ventajas en aplicaciones de alta potencia y media/alta tensión. En estas topologías, y comparadas con el convertidor tradicional de dos niveles, el voltaje que soporta cada dispositivo semiconductor es menor, evitando los problemas asociados con la interconexión serie de dispositivos. La distorsión armónica en la tensión de salida es también menor y la eficiencia mayor. Pero incorporan un número superior de dispositivos semiconductores y la estrategia de modulación resultante es, por tanto, más compleja.Entre estas topologías, el convertidor cc-ca de tres niveles trifásico con conexión al punto neutro del bus de cc es probablemente el más popular. La aplicación a este convertidor de técnicas de modulación convencionales causa una oscilación de la tensión del punto neutro de baja frecuencia (tres veces la frecuencia fundamental de la tensión de salida). Esta oscilación, a su vez, supone un incremento del estrés de tensión de los dispositivos y provoca la aparición de armónicos de baja frecuencia en la tensión de salida.Esta tesis presenta una nueva técnica de modulación del pulso de conducción de los dispositivos semiconductores para convertidores de tres niveles trifásicos con conexión a punto neutro, capaz de conseguir un control completo de la tensión del punto neutro con una distorsión armónica reducida en la tensión de salida alrededor de la frecuencia de conmutación. Esta nueva técnica de modulación, basada en la definición de unos vectores espaciales virtuales, garantiza el equilibrado de la tensión del punto neutro con cualquier carga (lineal o no, cualquier factor de potencia) y para todo el rango de tensión de salida, con el único requisito de que la suma de corrientes de fase sea nula.Las características de la técnica de modulación propuesta y sus beneficios con respecto a otras modulaciones se han verificado a través de simulaciones y experimentos tanto en lazo abierto como en lazo cerrado. / Multilevel converter topologies have received special attention during the last two decades due to their significant advantages in high-power medium- and high-voltage applications. In these topologies, and compared to the previous two-level case, the voltage across each semiconductor is reduced, avoiding the problems of the series interconnection of devices. The harmonic distortion of the output voltage is also diminished and the converter efficiency increases. But a larger number of semiconductors is needed and the modulation strategy to control them becomes more complex.Among these topologies, the three-level three-phase neutral-point-clamped voltage source inverter is probably the most popular. The application of traditional modulation techniques to this converter causes a low frequency (three times the fundamental frequency of the output voltage) oscillation of the neutral-point voltage. This, in turn, increases the voltage stress on the devices and generates low-order harmonics in the output voltage.This thesis presents a novel pulsewidth modulation for the three-level three-phase neutral-point-clamped converter, able to achieve a complete control of the neutral-point voltage while also having a low output voltage distortion at around the switching frequency. The new modulation, based on a virtual space vector concept, guarantees the balancing of the neutral-point voltage for any load (linear or nonlinear, any load power factor) over the full range of converter output voltage, the only requirement being that the addition of the output three-phase currents equals zero.The performance of this modulation approach and its benefits over other previously proposed solutions are verified through simulation and experiments in both open- and closed-loop converter configurations.

Cette thèse a pour but l'analyse d'un système photovoltaïque connecté au réseau électrique en prenant en compte le contrôle, l'étude de la stabilité et la fiabilité. Un onduleur de type 2-Niveau a été comparé avec un onduleur multi-niveaux appelé Neutral Point Clamped. Les avantages et désavantage de chaque topologie ont été analysé en considérant l'efficacité énergétique, l'optimisation de l'injection de l'énergie sur le réseau électrique et la fiabilité du système. Pour le contrôle du courant de sortie de l'onduleur, ont été proposées deux solutions : un contrôle basé sur la théorie de la platitude et un contrôle par passivité. Ces deux différents contrôles sont comparés par rapport à la robustesse, la complexité et le nombre de capteurs utilisés. Il a été montré que les deux contrôles sont capables de gérer la problématique de la résonance du filtre LCL. Pour augmenter l'efficacité de l'algorithme MPPT dans une configuration Distributed-MPPT avec la connexion en série des deux sorties des convertisseurs boost, une nouvelle technique a été proposé pour l'équilibrage des tension d'entrée d'un onduleur NPC. En utilisant un outil appelé TPtool, un étude de la stabilité large signal par "Higher-Order-Singular-Value-Decomposition" a été présenté et comparé avec une méthode basée sur les modèles Takagi-Sugeno pour des systèmes non-linéaires. Finalement, l'onduleur 2-Niveaux est comparé avec deux multi-niveaux différents (NPP et NPC) en termes de disponibilité, en prenant en compte les niveaux de redondance des convertisseurs. Pour analyser la disponibilité, a été considérée la théorie des chaines de Markov et pour l'implémentation, le logiciel GRIF a été utilisé / The aim of this PhD thesis is to analyze a PV-grid connected system in terms of control, stability and reliability. A comparison between a classical 2-Level inverter and a multilevel NPC is presented. The advantages and weakness of both the converters are analyzed with respect to the power efficiency, optimization of the energy injection to the grid and reliability of the system. In order to control the inverter output current, two different solutions are proposed: flatness-based control and passivity-based control. These controls are compared in terms of robustness, complexity and number of sensors used. It is shown that both the controls may manage the resonance problems due to a LCL filter. For increasing the efficiency of the MPPT in a configuration Distributed-MPPT with connections in series of the boost converters outputs, a novel technique for the dc voltages balancing of a NPC inverter is proposed. A large stability analysis using "Higher-Order-Singular-Value-Decomposition" is presented and compared with Takagi-Sugeno approach for nonlinear systems. Finally, 2-Level inverter is compared with two multilevel inverters (NPC and NPP) in terms of availability, considering the redundancy levels of the converters. To analyze the systems availability, the Markov chains theory is considered and it is implemented on GRIF

Due to development of industries, power factor and harmonic pollution have become serious concerns in the power system. This thesis presents an adaptive linear neuron (ADALINE) - based static synchronous compensator (STATCOM) to cope with power quality issues in the industrial power system. The targeted compensating current of the STATCOM is generated based on the so-called LMS algorithm, thus the compensated system current becomes balanced and active even in reactive, unbalanced or distorted loads. In this thesis, the STATCOM is realized by using a three-level neutral point-clamped (NPC) inverter with the in-phase level-shifted sinusoidal pulse width modulation (IPLSPWM). Theoretical analysis of ADALINE method is detailed and hardware implementation of STATCOM is conducted to validate effectiveness of the proposed approach.

Power inverters, used to convert DC power to AC, are often used in e.g. solar power applications. However, they tend to be impractically large and expensive; as such, power miniaturization is an active research area. In this thesis, several classes of modern power inverters are evaluated and compared with regards to size, efficiency and output quality in order to identify areas of potential improvement. Methods for estimation of THD, power losses and input ripple are created and verified against a simulation of a five-level neutral-point-clamped inverter with SPWM control. Finally, this design is implemented physically and is found to achieve 94.5% efficiency and 7% THD under low voltage laboratory conditions, while remaining smaller than an average textbook.

Nanomechanical resonators (NR) are cantilevers or doubly clamped nanowires (NW) which vibrate at their resonance frequency. These nanowires with picogram-level mass and frequencies of the order of MHz can resolve added mass in the attogram (10-18 g) range, enabling detection of a few molecules of cancer biomarkers based on the shift in resonance frequency. Such biomarker detection can help in the early stage detection of cancer and also aid in monitoring the treatment procedure in a more advanced stage. Optical transduction is one of the methods to measure the resonance frequency of the cantilever. However, there is a dependence of measured resonance frequency on the polarization of light and the laser power coupled as thermal energy into the cantilever during the measurement. This thesis presents a numerical model of the nanocantilever and shows the variation in resonance frequency and amplitude due to varied amounts of energy absorption by the NW from the laser during resonance measurements. This thesis answers questions on the effects of laser heating by calculating the temperature distribution in the NW, which changes the Young’s modulus and stiffness, causing a resonance downshift. It also shows the variation of resonance amplitude, affecting signal strength in measurements, by considering the effects of structural damping. In this work, a numerical model of the nanowire was analyzed to determine the temperature rise of the NW due to laser heating. The maximum temperature was calculated to be about 500 K with 1 mW of laser power absorbed in Silicon NWs and it is shown that the nanowire tip would reach its melting point for about 2.6 mW of laser power absorbed by it. The resonance shift due to attained temperature of the NW was calculated. The frequency is predicted to decrease by 24 kHz for a 11.6 MHz resonator, when 2mW of laser power is absorbed. However, the frequency shift is mode-dependent and is larger for higher modes. The variation in vibration amplitude around the resonance peaks is calculated based on the effects of structural damping. This can be used to decide on the suspension height of the NW above the substrate, before fabrication. This calculation also provides a method to study the variation in material damping due to temperature. Finally, a semi-analytical method for calculating the frequency of a cantilever beam with varying Young’s modulus is derived to examine the validity of the results calculated above. An effective Young’s modulus value for the laser heated NW is given, which serves as a correction factor for the resonance shift. The derivation is then extended to calculate the resonance shift with an addition of a mass to the beam of varying Young’s modulus. / Graduate / 2019-12-13