An algorithm that is capable of estimating the parameters of non-stationary sinusoids in real-time lends application to various branches of engineering. Non-stationary sinusoids are sinusoidal signals with time-varying parameters. In this dissertation, a nonlinear filter is applied to power system applications to test its performance. The filter has a structure which renders it fully adaptive to tracking time variations in the parameters of the targeted sinusoid, including its phase and frequency. Mathematical properties of the differential equations which govern the proposed filter are presented. The performance of the proposed filter in the field of power systems is demonstrated with the aid of computer simulations and practical experimentations. The filter is applied to synchronous generator excitation control, voltage dip mitigation as well as the real-time estimation of symmetrical components. The parameter settings of the filter are tested and optimized for each of the applications. This dissertation demonstrates the simulation and experimental results of the filter when applied to the various power system applications. AFRIKAANS : 'n Filter wat bevoeglik is met die beraming van die parameters van beweeglike sinusoïdale in ware-tyd, kan bruikbaar aangewend word in verskeie takke van ingenieurswese. Beweeglike sinuskrommes is sinusoïdale seine met tyd-wisselende parameters. In hierdie verhandeling word `n nie-liniêre filter aangewend in verskeie kragstelseltoepassings om die werksverrigting van die filter te toets. Die filter het 'n struktuur wat dit toelaat om wisselende tydvariasies in die parameters van die teikensinusoïdaal op te spoor, insluitende die fase en frekwensie. Wiskundige eienskappe van die differensiaalvergelykings wat die voorgestelde filter beheer is ondersoek. Die werksverrigting van die voorgestelde filter in die veld van kragstelsels is gedemonstreer met die hulp van rekenaarsimulasies asook praktiese eksperimente. Die filter is toegepas tot opgewekte, sinkrone eksitasie-beheer, spanningsverlaging versagting, asook die ware tyd estimasie van simmetriese komponente. Die parameter verstellings van die filter is getoets en geoptimeer vir elk van die toepassings. Hierdie verhandeling demonstreer die simulering en eksperimentele resultate van die filter wat aangewend is vir verskeie kragstelseltoepassings. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / unrestricted

The results described in this dissertation focus on the synthesis and utilization of several disulfonated poly(arylene ether) random copolymer membranes in fuel cell and reverse osmosis applications. Poly(arylene ether)s were prepared by direct step copolymerization using a third monomer 3,3–-disulfonated 4,4–-dichlorodiphenylsulfone. The membrane properties of a 4,4–-biphenol-based disulfonated poly (arylene ether sulfone) random copolymer (BPS-35), optionally blended with various fluorine containing polymers or unsulfonated biphenol-based poly (arylene ether sulfone)s (Radel R) were investigated for fuel cell applications. Fluorine containing copolymers used included with 2,2–-hexafluoroisopropylidene 4,4–-biphenol based unsulfonated (6F-00) or disulfonated (6FS-35 and 6FS-60) PAES, hexafluoroisopropylidene biphenol based 4,4–-difluoro phenyl phosphine oxide) (6FPPO), and poly(vinylidene fluoride) (Kynar®). Tapping mode atomic force microscopy (TM-AFM) images of the membranes with 10 wt% of fluorinated copolymers showed macroscopic phase separation. Good miscibility between the copolymers at low concentrations was also confirmed by the observation of only one glass transition temperature. Compared to the benchmark Nafion 1135, the 10wt% blends of the fluorinated copolymers afforded a considerable reduction in the methanol permeabilities, which is important for direct methanol fuel cells (DMFC). The best DMFC performance with 0.5 M methanol fuel was illustrated with blends containing 10 wt% 6FS-00. At higher methanol concentrations (up to 2.0 M) BPS-35/6FS-00 (90/10) membranes outperformed both Nafion membranes. Blends of BPS-35 blends with 6FS-35 or Radel R were also used as RO membranes. The highest salt rejections of 97.2 and 98.0% were obtained from BPS35/Radel R (90:10) and BPS-35/6FS-35 (95:5) blends, respectively in the salt form. A systematic study of the preparation of BPS-20 random copolymer skin-core asymmetric membranes by diffusion induced phase separation (DIPS) from various polar aprotic solvent or cosolvent systems is reported. The best aprotic solvents to generate an asymmetric structure were NMP and DMAc whereas tetrahydrofuran (THF)/ formamide (FAm) (80/20 v/v) mixtures proved to be the best co-solvent systems. Acetone was the best non-solvent to prepare asymmetric membranes from both aprotic solvents and co-solvent mixtures. Overall, asymmetric membranes prepared from THF/FAm co-solvent mixtures illustrated the most stable phase separated morphology that was free of macrovoids. However, thicker skins (~5 μM) were formed due to the high volatility of THF. Therefore, ultra-thin skin thin film composites (TFC) based on BPS-20 in diethylene glycol (Di(EG) were prepared. Thermal treatment of these TFC was conducted at 90 °C and the addition of 20 wt% glycerin to the casting formulation helped to prevent pore collapse in the porous Udel polysulfone. A minimum of three coats was required to obtain a dense, smooth, and pinhole free skin layer. The generation of three dimensional (ternary) solubility parameter phase diagrams based on experimental data was formulated and a region of solubility based on the solubility parameters of the aprotic solvents and the different co-solvent systems was established for BPS-20. / Ph. D.

L’extensa implantació del control digital als entorns industrials, científics, comercials, professionals i domèstics ha revelat, d’ençà dues dècades, la gran sensibilitat d’aquests dispositius davant sobtats i breus descensos de tensió al subministrament elèctric de xarxa: aturades de plantes a processos productius, re – arrancades a processadors i sistemes de telecomunicació, etc.; i la causa sol esdevenir aparentment inexplicable pels usuaris. La normalització de les conseqüències, però, pot equivaler a un dia sencer de producció nul•la. L’ínfima correlació mostrada pels fenòmens esmentats amb anomalies al sistema elèctric proper (un client pot patir sèries conseqüències, per bé que el client veí només ha percebut una oscil•lació a l’enlluernat, i tots dos comparteixen la mateixa escomesa) sumada amb l’absència contrastada d’interrupció elèctrica suposà, al començament, un major grau d’incertesa, no només pels consumidors; també per a les empreses elèctriques. Fou necessari analitzar el problema en les seves vessants “microscòpica” i “macroscòpica” per a determinar la causa eficient: registrar la forma d’ona al punt de subministrament afectat i fer l’inventari de tots els incidents al Sistema Elèctric del mateix moment. La causa: els sots de tensió produïts per incidents elèctrics a xarxes remotes respecte el subministrament. Davallades sobtades (entre el 80 i el 10% del valor nominal) i ràpides (entre 10 ms i 1 s) al valor eficaç de la tensió subministrada, sense pas per “Zero”, produïdes, principalment, per curt - circuits perfectament detectats i eliminats a xarxes d’Alta Tensió (AT), molt allunyats de la conseqüència observada. A Catalunya, hom comptabilitzen afectacions davant curt - circuits a les interconnexions amb l’Aragó, Castelló i França. La present Tesi Doctoral estableix: • La metodologia per a modelar el Sistema Elèctric de Potència; • La sistematització del binomi causa (curt - circuit) – efecte (sot de tensió); • La personalització estadística de risc pel sot de tensió segons comarques; • Un sistema de protecció eficaç per a limitar la durada dels sots. La metodologia ha estat enfocada a la utilització sistemàtica, tal que per a cada curt - circuit esdevingut a la xarxa AT es pugui establir, en temps real, las capçaleres de subministrament afectades pel sot de tensió, així com la magnitud i la durada del mateix. L’entorn d’aplicació triat ha estat el Sistema Elèctric de Catalunya, per bé que la metodologia i sistemàtica són exportables, de forma natural, a qualsevol altre sistema elèctric trifàsic de corrent altern. / La implantación masiva del control digital en entornos industriales, científicos, comerciales, profesionales y domésticos ha puesto de manifiesto, durante los últimos veinte años, la gran sensibilidad de los mismos ante súbitos y breves descensos de tensión en la alimentación eléctrica procedente de la red: paradas de planta en procesos productivos, re – arranques en procesadores y sistemas de telecomunicación tienen lugar; y la causa de los mismos suele ser aparentemente inexplicable para los usuarios. La normalización de las consecuencias, en ocasiones, equivale a un día de producción nula. La escasa correlación mostrada por dichos fenómenos con anomalías en el sistema eléctrico cercano (un cliente padece consecuencias serias, mientras que el cliente vecino solamente ha percibido una oscilación en el alumbrado y ambos se alimentan del mismo tramo eléctrico) sumada con la ausencia contrastada de interrupción eléctrica supuso, en los inicios, un mayor grado de incertidumbre tanto para los consumidores como para las empresas eléctricas. Fue necesario analizar el problema a nivel “microscópico” y “macroscópico” para determinar la causa eficiente: registrar la forma de onda en el punto de suministro afectado y revisar todos los incidentes habidos en el Sistema Eléctrico en dicho instante. La causa: los huecos de tensión producidos por incidentes eléctricos en redes alejadas del suministro. Descensos súbitos (entre el 80 y el 10% del valor nominal) y rápidos (entre 10 ms y 1 s) en el valor eficaz de la tensión suministrada, sin paso por “cero” de la misma, producidos, principalmente, por cortocircuitos perfectamente detectados y eliminados en redes de Alta Tensión (AT), y situados muy lejos de la consecuencia observada. En el caso de Catalunya, se han contabilizado afectaciones ante cortocircuitos en interconexiones con Aragón, Castellón de la Plana y Francia. La presente Tesis Doctoral establece: • La metodología para modelar el Sistema Eléctrico de Potencia; • La sistematización para el binomio causa (cortocircuito) – efecto (hueco); • La personalización del riesgo estadístico de hueco vs. comarcas; • Un sistema protectivo eficaz para limitar duración de los huecos. Dicha metodología se ha orientado a la utilización sistemática, tal que para cada cortocircuito que tenga lugar en la red AT pueda establecerse, en tiempo real, las cabeceras de suministro afectadas por hueco de tensión, la magnitud y la duración del mismo. Como entorno de aplicación, se ha utilizado el Sistema Eléctrico de Catalunya, si bien la metodología y sistematización son exportables, de forma natural, a cualquier otro sistema eléctrico trifásico de corriente alterna. / The massive introduction of digital control in industrial, scientific, commercial, professional and domestic environments has revealed, over the last twenty years, the great sensitivity of them to sudden and short voltage dips in the electrical power grid: shutdowns of productive process plants, re - starts of processors and telecommunications systems take place, and the cause of them is often apparently inexplicable to the users. The normalization of the consequences sometimes is equivalent to a day without production. The weak correlation shown by these phenomena with anomalies in the nearby electrical system (i.e. in the same portion of a common distribution network, a customer may suffer serious consequences, while the adjacent customer has only percept a swing in the lighting) together with the absence of electrical power interruption represented, in the beginning, a great degree of uncertainty for both consumers and utilities. It was necessary to analyze the problem at the "microscopic" and "macroscopic" levels to determine the efficient cause: record the waveform at the affected plants and review all the disturbances occurred in the Power System at the same instant of time. The cause: voltage dips caused by electrical disturbances away from the supply. Sudden decreases (between 80 and 10% of the nominal value) and fast (between 10 ms and 1 s) in the supplied rms voltage, produced mainly by short-circuits perfectly detected and eliminated in High Voltage (HV) networks, and located far away from the observed consequence. In the case of Catalonia, affectations due to short-circuits in interconnects with Aragon, Castellón de la Plana and France have been recorded. This thesis provides: • A methodology useful to model the Power System; • A systematic analysis for cause – effect: from short – circuit to voltage dip; • A particularization voltage dip statistic risk for each county; • A reliable protective system to ensure time – limitation for voltage dips. The presented methodology is oriented to the systematic use, such that for every short - circuit that takes place in the HV network, the magnitude and duration of voltage dips that appear in the distribution can be established in real-time. As the application framework, the Catalan Power System is used, although the methodology and systematization are exportable, to any other alternating three-phase power system.