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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

A DSP controlled resonant active filter for current harmonic mitigation in three-phase power systems

��nsal, Abdurrahman 01 December 2000 (has links)
Power quality has become an important concern to both electric utilities and end users due to the increased use of non-linear loads in modem power systems over the past decade. Nonlinear loads inject harmonics into the power system and thus may lead to poor power quality and lower power factor. Current and voltage harmonics can adversely affect the operation of sensitive devices. A common remedial solution to reduce the effects of harmonic distortion in a power system is filtering. Passive and active filters are two common types of harmonic filters. An active filter, in general, is a controllable current source that injects current at the same magnitude and opposite phase to that of the harmonic current. For this thesis work, a DSP-controlled active filter to cancel lower order (5th, 7th, 11th, and 13th) harmonics in a three-phase, three-wire power system is designed. The proposed active filter employs a series LC tank tuned to a high frequency, along with a pulse-width modulated (PWM) converter topology. The PWM control of the active filter is implemented in a TMS320F240 DSP. The DSP implementation enhances the performance of the filter in real-time and enables the filter to compensate for varying loads. Additionally, the use of DSP-control reduces the number of components and therefore reduces the cost and improves the reliability of the overall system. The uniqueness of the filter is in its ability to control each harmonic separately. A laboratory prototype of the proposed active filter has been built and tested to verify the performance of the active filter. / Graduation date: 2001
32

A Dimmable High Power Factor Electronic Ballast for Compact Fluorescent Lamps

Lam, John 18 July 2012 (has links)
Incandescent lamps are now being gradually replaced by Compact Fluorescent Lamps (CFLs) as CFLs consume less power to produce the same light output and its lifetime is much longer than that of an incandescent lamp. However, current CFLs have the following drawbacks: (1) the line current drawn from the CFL produce a large amount of unwanted harmonics that results in very poor input power factor; (2) the dimming performance of a CFL with conventional incandescent lamp dimmers is very poor. The performance of the CFL depends on the design of the electronic ballast circuit that is located at the base of each CFL. For a CFL electronic ballast to be practical, its size and cost is of utmost importance. Thus, the main challenge in the design of practical dimmable CFL ballasts is to solve the aforementioned CFL performance issues while minimizing its size and cost. In the first part of this dissertation, two novel high power factor single-stage electronic ballast topologies are proposed to solve the poor power factor issue of the CFLs that are currently on the market. Both proposed circuits have the following advantages: (1) only one switch is required in the power circuit; (2) the switch has both lower current and voltage stress than other conventional circuits; (3) the built-in power factor correction (PFC) circuit allows incandescent phase-cut dimmer to be used for dimming the CFL; (4) the circuit design is simple and it requires less system space compared to other conventional high PF electronic ballast topologies. The second part of this dissertation proposes a new control circuit that enables the lamp to maintain high power factor throughout the majority of the dimming range. In the proposed control scheme, the dimmer phase-cut angle is fed-forward to the control circuit. The controller then determines the proper duty cycle based on the phase-cut angle to facilitate the desired dimming operation. This novel control circuit was first implemented using analog circuitry. After assessing the performance of the analog version of the proposed controller, it was then digitally implemented through the Field Programmable Gate Array (FPGA) technique. The feasibility and performance of both the proposed electronic ballasts and control concept have been verified through theoretical analysis, simulation and experimental results on a 13W 4-pin D/E CFL from Osram Sylvania. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2010-04-30 12:51:59.682
33

CAN Control System for an Electric Vehicle

Azzeh, Abdel Rahman January 2007 (has links)
The University of Canterbury has purchased a 1992 Toyota MR2 and used it as the platform to construct a new electric car. Similar to the common combustion engine vehicle, electric vehicles require control systems to control the operation of 12Vdc auxiliary loads, such as lights, indicators and windscreen wipers, where traditional technology results in a large number of wires in the wiring harness. Also, with the added complexity of modern vehicles, the need for integrating independent control systems together has become very important in providing safer and more efficient vehicles. To reduce the number of wires and make it possible for different control systems to communicate, and so perform more complex tasks, a flexible and reliable control system is used. The CAN (Controller Area Network) control system is a simple two-wire differential serial bus system, which was developed by Bosch for automotive applications in the early 1980s. The power and control system within the vehicle is named the "Power Distribution Network" and it is implemented by using multiple power converters and the CAN control system. This thesis presents the design, implementation, and test results of the CAN control system for the MR2. The 312Vdc nominal battery voltage is converted to an intermediate voltage of 48Vdc. This configuration is considered more efficient than the usual 12Vdc distribution system since smaller and lighter wires can be used to carry the same amount of power. The power distribution network operates off the 48Vdc intermediate voltage, and provides 12Vdc output to power all auxiliaries within the vehicle. The Power Distribution Network is implemented with two major subsystems: the auxiliary power system, which consists of multiple converters to step-down voltage from the 48Vdc intermediate voltage to the 12Vdc, and the CAN control system, which is developed to control and integrate the 12Vdc auxiliary loads within the vehicle. The prototype CAN control system is fully operational and has been tested with 12Vdc loads which are used to simulate most of the auxiliary loads in the vehicle. Experimental measurements show that the prototype is able to successfully control and maintain the network of independent nodes. This confirms that in principle the CAN control system is suitable for controlling the auxiliary loads in an electric vehicle.
34

Active filters : a unified approach

Koozehkanani, Ziaddin Daie January 1996 (has links)
The increase in the occurrence of non-linear loads in power systems has caused considerable concern to power utilities and manufacturers of power electronics equipment. To alleviate the problems caused by generation of current harmonics, there has been considerable interest in the use of active filters. This thesis presents a unified approach to the design of active filter configurations. It is shown that this approach offers a systematic method of classifying existing structures and it can be used for developing new circuits.
35

A novel isolation technology for automotive power integrated circuit applications /

Jiang, Xingchuan. January 2007 (has links)
Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references. Also available in electronic version.
36

Magamp post-regulator applied to a quasi-resonant converter and magamp operation under extreme load condition in a PWM converter /

Lee, John C., January 1988 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1988. / Vita. Abstract. Includes bibliographical references (leaves 68-70). Also available via the Internet.
37

Experimental and analytical study on two-phase impingement cooling with and without electric field

Feng, Xin, January 2007 (has links)
Thesis (Ph.D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 10, 2009) Includes bibliographical references.
38

Modeling and simulation of custom power devices /

Kagalwala, Raxit A. January 1996 (has links)
Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [102]-109).
39

Serie- en parallelkompensasie van nie-aktiewe drywing

Klopper, Sonja 10 June 2014 (has links)
M.Ing. (Electrical and Electronic Engineering) / The purpose of this investigation is mainly the study of various topologies of force commutated distortion compensators. This is done against the background of distortion in power systems in general. At the time of the investigation confusion reigned the domein of terminology and definition of power components and power compensators. Part of the investigation was the functional categorizing of power compensators. Forced commutated distortion compensators were then highlighted as element of this suggested frame work. There is a general increase of distortion in power networks which emphasises the limits of passive filters to compensate for non-active power. The use of power converters as forced commutated distortion compensators proves an effective means whereby to counteract these limits. In this document the different topologies of forced commutated distortion compensators are labelled according to the position where the converter is coupled to the network, as well as the characteristics of the energy storage element used. The topologies are studied through modelling, mathematical analysis and simulation. An experimental system of one of the topologies is presented. Control strategies for forced commutated distortion compensators are discussed with emphasis on the control of energy loss in the energy storage elements of the compensators. The investigation is concluded with proposed ideas for futher study as well as a philosophical approach to the role of forced commutated distortion compensators in the future.
40

Manufacturability improvements of high frequency transformers

Swart, Barend Jacques 17 February 2014 (has links)
M.Ing. (Electrical and Electronic Engineering) / In order to improve the industrialisation of modern power converters, its physical size must be reduced, material must be utilised more efficiently and its manufacturability improved. Consequently, many converters are operated in the ultrasonic frequency range, where the size of its constituent components are considerably reduced. Even at high frequencies of operation, however, magnetic components are still the largest and heaviest components in converters, and do not utilise materials to their maximum benefit. The aim of this work is to investigate the possibility of improving the industrialisation of power electronic converters by making use of a novel, multiple core magnetic component structure, called the distributed transformer. Existing magnetic component structures are evaluated from a materials point of view and the concept of distributed magnetic components introduced. A generalised transformer model is developed for the distributed transformer and pertinent design considerations discussed. A 1.5 kw battery charger industrialised by Spoornet is based on the CukDC-DC converter and is used as a case study. A conventional monolithic isolation transformer is used in its construction after a complete mathematical analysis of the converter topology, and compared with the equivalent distributed transformer configuration. The distributed transformer is then compared with the conventional monolithic transformer and evaluated in terms of its physical and electrical performance, design and ease of manufacture.

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