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.

Afin de modéliser correctement les phénomènes liés à l'évaporation, les numériciens souhaitent obtenir des mesures expérimentales fiables, leur permettant d'améliorer leurs modèles. A l'opposé, de nombreux industriels souhaitent pouvoir réaliser des mesures in situ, avec des techniques expérimentales appliquées aux conditions réelles.C'est dans ce cadre que s'est inscrite cette thèse. L'objectif principal, a été de démontrer la faisabilité, et la stabilité, de mesures en réfractométrie d'arc-en-ciel sur des gouttes uniques en écoulement afin d'obtenir le taux d'évaporation de ces gouttes.L'utilisation d'un dispositif dédié habituellement à la PIV a servi à réaliser des acquisitions de couples d'images, séparées par un délai temporel variable. Une méthode très fine de la mesure de variation de diamètre a été introduite, autorisant la mesure du taux d'évaporation instantané d'une goutte en écoulement par le biais du déphasage de la structure de ripple.

Plasmonic properties of self-assembled silver nanoparticles/nanowires array on periodically patterned Si (100) substrate are reported with special attention on the mechanism of nanoparticles self-assembly. The advantage of this bottom up approach over other self-assembling and lithographic methods is the flexibility to tune array periodicity down to 20 nm with interparticle gaps as low as 5 nm along the ripple. Ripple pattern have shallow modulation (~2 nm) still particles self-assembly was observed in non-shadow deposition. Therefore adatoms diffusion and kinetics is important on ripple surface for the self-assembly. PVD e-beam evaporation method used for deposition has proven to be superior to sputter deposition due to lower incident flux and lower atom energy. It was found that particles self-assembly largely dependent on angle of incidence, substrate temperature, and deposition direction due to ripple asymmetric tilt. Ostwald ripening observed during annealing on ripples substrate has striking dependency on ripple periodicity and was found to be different compared to Ostwald ripening on flat Si surface. In-situ RBS measurements of deposited silver on flat and rippled substrate confirmed different sticking of atoms on the two surfaces. The difference between maximum and minimum of the calculated local flux show a peak at an incidence angle of 70o with respect to surface normal. This explains the best alignment of particles at this angle of incidence compare to others. Self-assembled nanoparticles are optically anisotropic, i.e. they exhibit a direction dependent shift in LSPR. The reason of the observed anisotropy is a direction dependent plasmonic coupling. Different in plane and out of the plane dielectric coefficients calculated by modelling Jones matrix elements, confirms that nanoparticle/nanowire array are biaxial anisotropic (ex ¹ ey ¹ ez). The nanoparticles are predominantlyinsulating while nanowires are both metallic and insulating depending on the dimension. Silver nanoparticles/nanowires self-aligned on pre-patterned rippled substrate are presented for the first time as an active SERS substrate. Anisotropic SERS response in such arrays is attributed to different field enhancement along and across the ripples. Strong plasmonic coupling in elongated nanoparticles chain results in significantly higher SERS intensity then spherical nanoparticles/nanowires and non-ordered nanoparticles. Higher SERS intensity across the nanowires array in comparison to along the array (bulk silver) confirms electromagnetic field enhancement (hot-junction) is responsible for SERS phenomenon. Self-assembly of cobalt nanoparticle on ripple pattern substrate is also reported. Due to less adatom mobility and higher sticking cobalt self-assembly is possible only at much higher temperature. A strong uniaxial magnetic anisotropy was observed not observed for non ordered cobalt particles.

This thesis investigates laser micromachining using a high pulse repetition frequency (high-PRF) femtosecond fibre laser. Three different types of industrial-grade metals, Stainless steel, Copper, and Aluminium are investigated. The impact of the processing parameters on material removal is studied. Finally the feasibility of the technology in three dimensional micro structuring is explored. The thesis contributes to clarify the main interaction mechanisms occurring in high-PRF femtosecond laser processing. Heat accumulation and particle shielding are identified as main material removal influencing mechanisms. As a result of heat accumulation, lowered ablation thresholds are detected for Aluminium (0.16 J/cm² at 1.02 MHz versus 0.33 J/cm² at 20 kHz) and Stainless steel (0.088 J/cm² at 1.02 MHz versus 0.11 J/cm² at 20 kHz). For the high heat conductive Copper heat accumulation is largely ruled out. Particle shielding is investigated by ultra high speed camera imaging. It is shown that the ablation plumes enlarge at the higher pulse repetition rates. A parameter study investigates material ablation. From this study, appropriate machining parameters are derived with regard to both high ablation rate and removal efficiency, and small roughness: Aluminium: 5 μm pulse spacing / 5 μJ pulse energy, Copper: 7.5 μm pulse spacing / 7 μJ pulse energy, Stainless steel: 5 μm pulse spacing / 3 μJ pulse energy. In addition experimentally and theoretically determined volume ablation rates are compared. For this, a material removal calculation model is designed. Good agreements between theoretical and experimental values are obtained by taking into account effective penetration instead of optical penetration for energy transport. A surface temperature calculation model is designed, providing useful insights into heat accumulation. Heat accumulation observed for Aluminium and Stainless Steel is confirmed by surface temperature rise, calculated based on the remaining energy. Improvement of the model by enhanced energy coupling yields surface temperatures above the melting temperature. This is conclusive to experimental observations. Finally the feasibility of the high-PRF femtosecond laser technology in micromachining is demonstrated by micro mould fabrication. Utilising these moulds, micro-fluidic plastic demonstrators are fabricated by micro-injection moulding.

abstract: With the push for integration, a slew of modern switching power management circuits are operating at higher switching frequencies in order to reduce passive filter sizes. But while these switching regulators provide power conversion at high efficiencies, their output is prone to ripples due to the inherent switching behavior. These switching regulators use linear-low dropout regulators (LDOs) downstream to provide clean supplies. Typically, these LDOs have good power supply rejection (PSR) at lower frequencies but this degrades at higher frequencies. Therefore, some residual ripple is still manifested on the output. Because of this, high power supply rejection (PSR) with a wide rejection frequency band is becoming a critical requirement in linear low-dropout regulators (LDOs) used in complex systems- on-chip (SOCs). Typical LDOs achieve higher PSR within their loop-bandwidth; however, their supply rejection performance degrades with reduced loop-gain outside their loop- bandwidth. The LDOs with external filtering capacitors may also have spectral peaking in their PSR response, causing excess system- level supply noise. This work presents an LDO design approach, which achieves a PSR of higher than 68 dB up to 2 MHz frequency and over a wide range of loads up to 250 mA. The wide PSR bandwidth is achieved using a current-mode feedforward ripple canceller (CFFRC) amplifier which provides up to 25 dB of PSR improvement. The feedforward path gain is inherently matched to the forward gain of the LDO, not requiring calibration. The LDO has a fast load transient response with a recovery time of 6.1μs and has a quiescent current of 5.6μA. For a full load transition, the LDO achieves settling with overshoot and undershoot voltages below 27.6 mV and 36.36 mV, respectively. The LDO is designed and fabricated in a 180 nm bipolar/CMOS/DMOS (BCD) technology. The CFFRC amplifier helps to achieve low quiescent power due to its inherent current mode nature, eliminating the need for supply ripple summing amplifiers and adaptive biasing. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2020

In this work, a modified boost converter design has been implemented in a multiphase configuration with a condensed topology. The modified aspect of the design has already been proven to drastically reduce input current ripple by about 40% in a single-phase implementation. By placing two modified boost converters in parallel with interleaving main switches (multiphase), the input inductors and modified capacitors of the modified topology can be reduced to just one of each, lowering the number of components, size, and cost. Additionally, multiphase DC/DC converters lower input/output voltage and current ripples while delivering more power compared to single-phase converters. By combining the modified and multiphase benefits, this thesis creates a topology with low ripple and noise while providing high power capability. This thesis covers the analysis, simulation, hardware implementation, and testing of the Modified-Multiphase Boost Converter as well as an equivalent Standard-Multiphase Boost Converter for comparison. Simulation and hardware test results exhibited a 9% input current ripple reduction with the Modified-Multiphase design, presenting a high-power converter with considerable input noise reduction. Keywords: dc/dc, boost, multiphase, interleave, modified, power, ripple

This thesis deals with position control of movable solenoid core without using a distance sensor. There are several methods of sensorless position estimation presented in theoretical part. The method based on measurement of ripple current is chosen for experiments. Firstly, it is verified by simulations with mathematical model of solenoid. After that, the experiment is created. The goal is position control based on sensorless method.

The master’s thesis deals with the design of a synchronous motor with embedded magnets. First of all, the general theory of synchronous motor, which is focused on field-weakening drive, is described. Then a 6-pole and a 8-pole version of the motor with embded magnet, which has 65 kW and 3000 rpm is complexly designed. Motors are compared with each other and with a motor with surface magnets, that was also designed in this work. Finally, all motors are compared with a mafufactured and measured motor.

This master's thesis focuses on the subject Management of free capital inside the cryptocurrency market. First, selected cryptocurrencies are briefly described. Subsequently, their historical data are analysed. Finally, based on these findings, an appropriate strategy for the chosen company is formulated.

This thesis is focused on the sensorless control of BLDC motor using the Extended Kalman filter. In the first section, process of EKF implementation for estimating rotor speed and electrical angle is described. For this estimation, EKF uses non-linear BLDC motor model and some measurement containing random noise. Second part deals with designing methodology to measure and estimate the quality of BLDC motor sensorless control. Best results were achieved with total current entering power electronics ripple analyzation. In the last section, several BLDC sensorless control algorithms were evaluated.