In low power, battery-operated, portable applications, like cell phones, PDAs, digital cameras, etc., miniaturization at a low cost is a prominent driving factor behind product development and marketing efforts. As such, power supplies in portable applications must not only conform and adapt to their highly integrated on-chip and in-package environments but also, more intrinsically, respond quickly to fast load dumps to achieve and maintain high accuracy. The frequency-compensation network, however, limits speed and regulation performance because, in catering to all combinations of the output capacitor, its equivalent series resistance Resr, and the power inductor resulting from tolerance and modal design targets, it must compensate the worst-case condition and therefore restrain the performance of all other possible scenarios. Sigma-delta control, which addresses this issue in buck converters by easing its compensation requirements and offering one-cycle transient response, has not been able to simultaneously achieve high bandwidth, high accuracy, and wide LC-Resr compliance in boost (step-up) converters. This thesis investigates and presents techniques to achieve sigma-delta control in boost converters by essentially using explicit current and voltage control loops. The proposed techniques are developed conceptually and analytical expressions for stability range and transient response are derived. The proposed concepts are validated and quantified through PCB and IC prototypes to yield 1.41 to 6 times faster transient response than the state of the art in current-mode boost supplies, and this without any compromise in LC-Resr compliance range.

M. Tech. Electrical Engineering / Investigates the reasons behind the poor performance of distance relays on series compensated lines. In order to achieve this objective, a case study will be established in a power system software (DigSilent Power Factory). Furthermore, a practical incident that occurred on Eskom's compensated network will be examined. However, prior to investigating the performance of the distance relay on transmission lines, there are some other critical aspects that have to be thoroughly understood. These aspects include amongst others: transmission line modelling ; numeric relay algorithms ; distance protection philosophies ; series compensation phenomena ; analysis of distance relays performance on both compensated and uncompensated lines and the action and influence of the MOV. The study will provide a better understanding regarding the dynamic behaviour of the impedance protection relay under fault conditions on series compensated lines and the behaviour of the MOV during a fault.

Conventionally, system simulations of induction motor drives use lumped parameters model of the motor. This approach assumes motor parameters to be constant during the entire operation of the drive. Unfortunately, these are known to vary significantly over the operating range of the motor due to factors such as magnetic saturation, skin effects, and operating temperature. The variations in motor parameters affect motor output and control parameters resulting in degraded drive performance. One way of overcoming this problem is by coupling the field model of the induction motor with the drive simulation. By replacing the lumped parameters model with the field model, the influence of different operating conditions on motor parameters can be taken into account dynamically. In this thesis such an approach is investigated by coupling the finite element analysis of an induction motor with the system simulation of the field oriented controlled drive. The results obtained for the coupled simulation are promising and possible future works to make this method of simulation more accurate and reliable are recommended.

Solar photovoltaic (PV) systems are distributed energy sources that are an environmentally friendly and renewable source of energy. However, solar PV power fluctuates due to variations in radiation and temperature levels. Furthermore, when the solar panel is directly connected to the load, the power that is delivered is not optimal. A maximum peak power point tracker is therefore necessary for maximum efficiency. A complete PV system equipped maximum power point tracking (MPPT) system includes a solar panel, MPPT algorithm, and a DC-DC converter topology. Each subsystem is modeled and simulated in a Matlab/Simulink environment; then the whole PV system is combined with the battery load to assess the overall performance when subjected to varying weather conditions. A PV panel model of moderate complexity based on the Shockley diode equation is used to predict the electrical characteristics of the cell with regard to changes in the atmospheric parameter of irradiance and temperature. In this dissertation, five MPPT algorithms are written in Matlab m-files and investigated via simulations. The standard Perturb and Observe (PO) algorithm along with its two improved versions and the conventional Incremental Conductance (IC) algorithm, also with its two-stage improved version, are assessed under different atmospheric operating conditions. An efficient two-mode MPPT algorithm combining the incremental conductance and the modified constant voltage methods is selected from the five ones as the best model, because it provides the highest tracking efficiencies in both sunny and cloudy weather conditions when compared to other MPPT algorithms. A DC-DC converter topology and interface study between the panel and the battery load is performed. This includes the steady state and dynamic analysis of buck and boost converters and allows the researcher to choose the appropriate chopper for the current PV system. Frequency responses using the state space averaged model are obtained for both converters. They are displayed with the help of Bode and root locus methods based on their respective transfer functions. Following the simulated results displayed in Matlab environment for both choppers, an appropriate converter is selected and implemented in the present PV system. The chosen chopper is then modeled using the Simulink Power Systems toolbox and validates the design specifications. The simulated results of the complete PV system show that the performances of the PV panel using the improved two-stage MPPT algorithm provides better steady state and fast transient characteristics when compared with the conventional incremental conductance method. It yields not only a reduction in convergence time to track the maximum power point MPP, but also a significant reduction in power fluctuations around the MPP when subjected to slow and rapid solar irradiance changes. / Thesis (M.Sc.Eng)-University of KwaZulu-Natal, Durban, 2011.

Power management components can be found in a host of different applications ranging from portable hand held gadgets to modern avionics to advanced medical instrumentations, among many other applications. Low-dropout (LDO) linear regulators are particularly popular owing to their: ease of use, low cost, high accuracy, low noise, and high bandwidth. With all its glory, however, it tends to underperform switched-mode power supplies (SMPS) when with comes to power conversion efficiency, although the later generates a lot of ripple at its output. With the growing need to improve system efficiency (hence longer battery life) without degrading system performance, many high end (noise sensitive) applications such as data converters, RF transceivers, precision signal conditioning, among others, use high efficiency SMPS with LDO regulators as post-regulators for rejecting the ripple generated by SMPS. This attribute of LDO regulators is known as power supply rejection (PSR). With the trend towards increasing switching frequency for SMPS, to minimize PC board real estate, it is becoming ever more difficult for LDO regulators to suppress the associate high frequency ripple since at such high frequencies, different parasitic components of the LDO regulator start to deteriorate its PSR performance. There have been a handful of different techniques suggested in the literature that can be used to achieve good PSR performance at higher frequencies. However, each of these techniques suffers from a number of drawbacks ranging from reduced efficiency to increased cost to increased solution size, and with the growing demand for higher efficiency and smaller power supplies, these techniques have their clear limitations. The objective of this research project is to develop a novel current-mode LDO regulator that can achieve good high frequency PSR performance without suffering from the afore mentioned drawbacks. The proposed architecture was fabricated using a proprietary 1.5 um Bipolar process technology, and the measurement results show a PSR improvement of 20dB (at high frequencies) over conventional regulators. Moreover, the proposed LDO regulator requires a small 15nF output capacitor for stability, which is far smaller than some of the currently used techniques.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 6, 2009). Thesis advisor: Dr. Naz E. Islam. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Includes bibliographical references (p. 170-177).

Thesis (MEng)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: This thesis presents the design of a DSP based controller system for an auxiliary converter for generic energy storage connection to a line-interactive power compensator. The aim is to utilize a wide range of energy storage systems and incorporate them into the existing power compensator. This was done by adding a second converter to the system. The new controller was developed to control this converter and thereby the energy storage. A study was done on lead acid batteries, flow batteries and flywheels in order to gain a basic understanding of these systems and identify the requirements for their control. Based on these findings, a new DSP based controller and measuring system was developed. To test the new system a dc to dc converter was implemented for the control of lead acid and flow batteries. A dc to ac converter was also tested for the control of flywheel energy storage. / AFRIKAANSE OPSOMMING: Die tesis handeloor die ontwerp van'n DSP gebaseerde beheerstelsel vir 'n Iyninteraktiewe on-onderbreekbare kragbron met drywings-kompensasie met 'n hulp omsetter vir algemene enegiestoor koppeling. The doel is om 'n wye verskeindheid energie store in die huidige drywings elektroniese stelsel te inkorporeer. 'n Tweede omstetter is by die stelsel gevoeg om die energie stelsel te beheer. 'n Nuwe beheerder is ontwikkel om die omsetter te beheer en daardeur die energie stoor. Loodsuur batterye, vloei batterye en vliegwiele is ondersoek om 'n basiese begrip te vorm en te identifiseer wat nodig is vir die beheer van sulke energie store. Die nuwe DSP beheerder en meetstelsel is ontwikkel gebaseer op hierde ondervindings. Om die nuwe beheerstelsel te toets is 'n gs na gs omsetter geïmplementeer vir die beheer van loodsuur en floei batterye. Die omsetter is geherkonfigureer na 'n gs na ws opstelling en getoets. Die konfigurasie word gebruik vir die beheer van vliegwiele.

O presente trabalho trata do estudo, análise, construção e teste de uma nova configuração para um atuador planar. O dispositivo é composto de um núcleo de armadura ferromagnético plano, estático e sem ranhuras sobre o qual são montados dois conjuntos de enrolamentos planares, ortogonais entre si, com quatro bobinas cada, eletricamente independentes entre si. A parte móvel consiste de um carro equipado com ímãs permanentes de alto produto energético responsáveis pela produção de fluxo magnético de excitação. A movimentação bidirecional sobre o plano se dá pela interação entre esse fluxo e a corrente elétrica adequadamente aplicada aos enrolamentos. O atuador apresenta uma distribuição espacial da densidade de fluxo magnético em toda a sua estrutura. Este trabalho preocupa-se em analisar numérica e experimentalmente os fenômenos eletromagnéticos envolvidos, tanto em regime estático como dinâmico. O emprego de dois diferentes materiais utilizados separadamente no núcleo da armadura é investigado: o aço maciço (caso 1) e um compósito magneticamente macio de grão isolado (caso 2). Devido à movimentação do carro e conseqüentemente do fluxo magnético de excitação, uma força eletromotriz induzida aparecerá no núcleo da armadura, sendo responsável pelo estabelecimento de correntes elétricas induzidas no mesmo. Essas correntes, que também dependem da condutividade do material do núcleo, produzem um efeito de frenagem sobre o carro do atuador que afeta a sua dinâmica. Produzem ainda perdas Joule no núcleo da armadura. A redução desses efeitos pode ser obtida com a utilização de um material magnético isotrópico de alta resistividade, caso 2, que possibilita ainda a distribuição tridimensional da densidade de fluxo magnético na estrutura do atuador. Uma análise dinâmica a partir do método dos elementos finitos tornou possível a verificação da distribuição da densidade de corrente elétrica induzida no núcleo da armadura, bem como a obtenção dos seus valores em função da velocidade do carro e do material utilizado. Ainda, o efeito de frenagem foi quantificado em ensaios práticos, propondo-se então um coeficiente de atrito total, k, para cada um dos dois casos em estudo. Nessa caracterização, obteve-se que o coeficiente de atrito eletromagnético, devido às correntes induzidas, de 1,74469 Ns/m para o caso 1, enquanto que para o caso 2 esse valor fica em 0,261285 Ns/m. Os resultados numéricos e experimentais apontam que existem diferenças significativas na utilização dos dois materiais propostos, indicando que o caso 2, quando utilizado de maneira adequada no sistema, reduz as correntes elétricas induzidas minimizando seus efeitos. / The present work deals with the study, analysis, construction and testing of a new configuration of a planar actuator. The device comprehends a static ferromagnetic slotless core in form of slab, on which two sets of planar windings are assembled. They are orthogonal with respect to each other and have four independent coils. The moving part consists of a car, equipped with high energy product permanent magnets that deliver the excitation magnetic flux. The bidirectional movement on the plan is a result of the interaction between the excitation magnetic flux and the electric currents that fed the armature windings properly. The actuator features a spatial distribution of the magnetic flux density throughout its structure. This work is concerned with the numerical and experimental analyses of the electromagnetic effects involved in terms of static and dynamic behavior of the actuator. These effects are investigated for two different materials employed separately in the core of the armature: solid steel (case 1) and a grain isolated soft magnetic composite (case 2). Owing to the movement of the car and so the excitation magnetic flux, an induced electromotive force appears on the core of the armature and is responsible for the establishment of induced electrical currents in there. These currents, that also depend on the conductivity of the material of the armature core, produce a braking effect on the car that affects the dynamics of the actuator. It also produces Joule losses on that core. The reduction of those effects can be obtained with the use of an isotropic ferromagnetic material with high resistivity, case 2, that allows the 3d distribution of magnetic flux density on the structure of the actuator. A dynamic analysis by means of the finite element method made possible to verify the distribution of the induced electrical current density in the core of the armature, and to compute its value according to the speed of the car and to the material employed. Still, the effect of the braking force was quantified experimentally; as a result, a total friction coefficient, k, is proposed in order to take into account that force. By doing that, a resulting coefficient of electromagnetic friction due to the induced currents is 1.74469 Ns/m for case 1, while for case 2 it is 0.261285 Ns/m. The numerical and experimental results indicate that exist significant differences in the use of the two materials proposed, indicating that the case 2, when used in an appropriate manner, reduces the induced electrical currents minimizing its effects.

O presente trabalho trata do estudo, análise, construção e teste de uma nova configuração para um atuador planar. O dispositivo é composto de um núcleo de armadura ferromagnético plano, estático e sem ranhuras sobre o qual são montados dois conjuntos de enrolamentos planares, ortogonais entre si, com quatro bobinas cada, eletricamente independentes entre si. A parte móvel consiste de um carro equipado com ímãs permanentes de alto produto energético responsáveis pela produção de fluxo magnético de excitação. A movimentação bidirecional sobre o plano se dá pela interação entre esse fluxo e a corrente elétrica adequadamente aplicada aos enrolamentos. O atuador apresenta uma distribuição espacial da densidade de fluxo magnético em toda a sua estrutura. Este trabalho preocupa-se em analisar numérica e experimentalmente os fenômenos eletromagnéticos envolvidos, tanto em regime estático como dinâmico. O emprego de dois diferentes materiais utilizados separadamente no núcleo da armadura é investigado: o aço maciço (caso 1) e um compósito magneticamente macio de grão isolado (caso 2). Devido à movimentação do carro e conseqüentemente do fluxo magnético de excitação, uma força eletromotriz induzida aparecerá no núcleo da armadura, sendo responsável pelo estabelecimento de correntes elétricas induzidas no mesmo. Essas correntes, que também dependem da condutividade do material do núcleo, produzem um efeito de frenagem sobre o carro do atuador que afeta a sua dinâmica. Produzem ainda perdas Joule no núcleo da armadura. A redução desses efeitos pode ser obtida com a utilização de um material magnético isotrópico de alta resistividade, caso 2, que possibilita ainda a distribuição tridimensional da densidade de fluxo magnético na estrutura do atuador. Uma análise dinâmica a partir do método dos elementos finitos tornou possível a verificação da distribuição da densidade de corrente elétrica induzida no núcleo da armadura, bem como a obtenção dos seus valores em função da velocidade do carro e do material utilizado. Ainda, o efeito de frenagem foi quantificado em ensaios práticos, propondo-se então um coeficiente de atrito total, k, para cada um dos dois casos em estudo. Nessa caracterização, obteve-se que o coeficiente de atrito eletromagnético, devido às correntes induzidas, de 1,74469 Ns/m para o caso 1, enquanto que para o caso 2 esse valor fica em 0,261285 Ns/m. Os resultados numéricos e experimentais apontam que existem diferenças significativas na utilização dos dois materiais propostos, indicando que o caso 2, quando utilizado de maneira adequada no sistema, reduz as correntes elétricas induzidas minimizando seus efeitos. / The present work deals with the study, analysis, construction and testing of a new configuration of a planar actuator. The device comprehends a static ferromagnetic slotless core in form of slab, on which two sets of planar windings are assembled. They are orthogonal with respect to each other and have four independent coils. The moving part consists of a car, equipped with high energy product permanent magnets that deliver the excitation magnetic flux. The bidirectional movement on the plan is a result of the interaction between the excitation magnetic flux and the electric currents that fed the armature windings properly. The actuator features a spatial distribution of the magnetic flux density throughout its structure. This work is concerned with the numerical and experimental analyses of the electromagnetic effects involved in terms of static and dynamic behavior of the actuator. These effects are investigated for two different materials employed separately in the core of the armature: solid steel (case 1) and a grain isolated soft magnetic composite (case 2). Owing to the movement of the car and so the excitation magnetic flux, an induced electromotive force appears on the core of the armature and is responsible for the establishment of induced electrical currents in there. These currents, that also depend on the conductivity of the material of the armature core, produce a braking effect on the car that affects the dynamics of the actuator. It also produces Joule losses on that core. The reduction of those effects can be obtained with the use of an isotropic ferromagnetic material with high resistivity, case 2, that allows the 3d distribution of magnetic flux density on the structure of the actuator. A dynamic analysis by means of the finite element method made possible to verify the distribution of the induced electrical current density in the core of the armature, and to compute its value according to the speed of the car and to the material employed. Still, the effect of the braking force was quantified experimentally; as a result, a total friction coefficient, k, is proposed in order to take into account that force. By doing that, a resulting coefficient of electromagnetic friction due to the induced currents is 1.74469 Ns/m for case 1, while for case 2 it is 0.261285 Ns/m. The numerical and experimental results indicate that exist significant differences in the use of the two materials proposed, indicating that the case 2, when used in an appropriate manner, reduces the induced electrical currents minimizing its effects.