The harmonic problem in power systems is gaining more attention as incidences correlated with harmonics increase. Conventional passive filtering techniques for harmonic mitigation have inherent problems, and purely active filters have the disadvantages of higher costs and ratings. Hybrid active filters inherit the efficiency of passive filters and the improved performance of active filters, and thus constitute a viable improved approach for harmonic compensation. To date, there have been several literature works comparing passive and active filters for harmonic mitigation. However, there are currently no comparisons of possible hybrid active filters. This thesis presents an assessment and comparison of hybrid active filters, including their topologies and control algorithms. Three different topologies of hybrid active filters are simulated in PSpice version 9.0 to verify their feasibility for harmonic compensation. From the simulations, all three topologies have better performance over passive filters for harmonic compensation and are insensitive to parameter variations. In addition, the simulated hybrid active filter ratings are lower than can be achieved with purely active filters. A modified "p-q" theory is introduced for control strategy, which is more feasible for extracting harmonic components for distorted load voltages. This thesis concludes with a comprehensive comparison of the hybrid active filter characteristics. / Graduation date: 2001

All telecommunication systems, such as cellular mobile networks (cellphones), object-detection systems (radars), and navigation systems that include satellite positioning systems (GPS), base their functioning on radio wave radiation with pre-defined frequencies and thus require a microwave filter to select the most appropriate frequencies. Generally speaking, the more highly-selective a filter is, the less non-useful frequencies and interference it picks up. Recent advances in microwave instruments, semiconductors, fabrication technologies and microwave filters applications have ushered in a new era in performance but have also brought significant challenges, such as keeping fabrication costs low, miniaturizing, and making low-profile devices. These challenges must be met while at the same time maintaining the performance of conventional devices. The thesis proposes use of lossy filter concepts to maintain high quality filtering frequency response flatness and selectivity regardless of the filter’s physical size. The method is applied to lumped element filters. It introduces resistances to the physical structure of the filter and hence a certain amount of loss to the frequency response of the filter. The lossy filter synthesis is based on the coupling matrix mode. The thesis also proposes modifications to the traditional lossy filter design techniques, to improve the filter performance in the stopband.

Thesis--Auburn University, 2009. / Abstract. Includes bibliographic references (p.46-49).

No description available.

All telecommunication systems, such as cellular mobile networks (cellphones), object-detection systems (radars), and navigation systems that include satellite positioning systems (GPS), base their functioning on radio wave radiation with pre-defined frequencies and thus require a microwave filter to select the most appropriate frequencies. Generally speaking, the more highly-selective a filter is, the less non-useful frequencies and interference it picks up. Recent advances in microwave instruments, semiconductors, fabrication technologies and microwave filters applications have ushered in a new era in performance but have also brought significant challenges, such as keeping fabrication costs low, miniaturizing, and making low-profile devices. These challenges must be met while at the same time maintaining the performance of conventional devices. The thesis proposes use of lossy filter concepts to maintain high quality filtering frequency response flatness and selectivity regardless of the filter’s physical size. The method is applied to lumped element filters. It introduces resistances to the physical structure of the filter and hence a certain amount of loss to the frequency response of the filter. The lossy filter synthesis is based on the coupling matrix mode. The thesis also proposes modifications to the traditional lossy filter design techniques, to improve the filter performance in the stopband.

Thesis (Ph. D.)--University of Adelaide, 1984. / At head of title: The University of Adelaide. Department of Electrical and Electronic Engineering. Includes bibliographical references (leaves Bibl. 1-Bib. 11).

Thesis (Ph. D.)--University of New South Wales, 1995. / Also available online.

Thesis (M.S.)--West Virginia University, 1998. / Title from document title page. "October 1998." Document formatted into pages; contains viii, 80 p. : ill. Includes abstract. Includes bibliographical references (p. 78-80).

<p> A two-part scheme for the design of wideband linear phase SAW filters is proposed. The design uses curved finger interdigital transducers, and extension of slanted finger design, to compensate for circuit effects and eliminate the need for matching. Theory is combined with distortion minimizing techniques to realize devices which satisfy INTELSAT filter specifications. </p> <p> Basic SAW theory is reviewed. and curved finger theory presented, while methods of distortion minimization are both reviewed and proposed. Experimental results which illustrate and support the theory given are included. </p> / Thesis / Master of Engineering (MEngr)

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