Design and Control of Power Converters for High Power-Quality Interface with Utility and Aviation Grids

Power electronics as a subject integrating power devices, electric and electronic circuits, control, and thermal and mechanic design, requires not only knowledge and engineering insight for each subarea, but also understanding of interface issues when incorporating these different areas into high performance converter design.Addressing these fundamental questions, the dissertation studies design and control issues in three types of power converters applied in low-frequency high-power transmission, medium-frequency converter emulated grid, and high-frequency high-density aviation grid, respectively, with the focus on discovering, understanding, and mitigating interface issues to improve power quality and converter performance, and to reduce the noise emission.For hybrid ac/dc power transmission,• Analyze the interface transformer saturation issue between ac and dc power flow under line unbalances.• Proposed both passive transformer design and active hybrid-line-impedance-conditioner to suppress this issue.For transmission line emulator,• Propose general transmission line emulation schemes with extension capability.• Analyze and actively suppress the effects of sensing/sampling bias and PWM ripple on emulation considering interfaced grid impedance.• Analyze the stability issue caused by interaction of the emulator and its interfaced impedance. A criterion that determines the stability and impedance boundary of the emulator is proposed.For aircraft battery charger,• Investigate architectures for dual-input and dual-output battery charger, and a three-level integrated topology using GaN devices is proposed to achieve high density.• Identify and analyze the mechanisms and impacts of high switching frequency, di/dt, dv/dt on sensing and power quality control; mitigate solutions are proposed.• Model and compensate the distortion due to charging transition of device junction capacitances in three-level converters.• Find the previously overlooked device junction capacitance of the nonactive devices in three-level converters, and analyze the impacts on switching loss, device stress, and current distortion. A loss calculation method is proposed using the data from the conventional double pulse tester.• Establish fundamental knowledge on performance degradation of EMI filters. The impacts and mechanisms of both inductive and capacitive coupling on different filter structures are understood. Characterization methodology including measuring, modeling, and prediction of filter insertion loss is proposed. Mitigation solutions are proposed to reduce inter-component coupling and self-parasitics

Study of efficient transmission and reception of image-type data using millimeter waves

Evaluation of signal processing and modulation techniques for transmission and reception of image type data via millimeter wave relay satellite

Active damping of a 6th order 3LC output filter with state-feedback

Standard solution to reduce switching ripple in power converters is to employ LC(L) output filters, with higher attenuation requiring higher switching frequency and/or larger filter size. High switching frequency can increase the converter losses, whereas large filter reduces the bandwidth and increases cost of the power converter. The alternative path of increasing the filter order is taken in this paper. To be more exact, a 6th order filter consisting of 3 series connected LC blocks is employed to achieve very high ripple attenuation and increased converter bandwidth without increasing the switching frequency. In contrast to previously proposed high-order filter solutions active damping is employed yielding no penalty to the converter efficiency. The active damping is achieved via state-feedback control, i.e., Linear Quadratic Regulator, with the state information reconstructed only from capacitor voltage measurements with a Luenberger observer. The complete design is evaluated in simulations and validated on the experimental synchronous buck converter achieving in excess of −80 db ripple attenuation in one decade

Voyager spacecraft. Volume V - Alternate designs, subsystems considerations Study report, phase IA

Telecommunication, propulsion, control, electric, and mechanical subsystems design for Voyager spacecraf

Goddard Laboratory for Atmospheric Science, collected reprints 1978-1979, volume 1

A ready reference is presented to 61 papers by members of the Laboratory published between January 1, 1978 and December 31, 1979. To avoid unnecessary duplication, only abstracts or introductions of NASA reports and conference proceedings are included with reprints of articles from various journals

Proceedings of the First International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics

1st International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Kruger Park, 8-10 April 2002.This lecture is a principle-based review of a growing body of fundamental work stimulated by multiple opportunities to optimize geometric form (shape, structure, configuration, rhythm, topology, architecture, geography) in systems for heat and fluid flow. Currents flow against resistances, and by generating entropy (irreversibility) they force the system global performance to levels lower than the theoretical limit. The system design is destined to remain imperfect because of constraints (finite sizes, costs, times). Improvements can be achieved by properly balancing the resistances, i.e., by spreading the imperfections through the system. Optimal spreading means to endow the system with geometric form. The system construction springs out of the constrained maximization of global performance. This 'constructal' design principle is reviewed by highlighting applications from heat transfer engineering. Several examples illustrate the optimized internal structure of convection cooled packages of electronics. The origin of optimal geometric features lies in the global effort to use every volume element to the maximum, i.e., to pack the element not only with the most heat generating components, but also with the most flow, in such a way that every fluid packet is effectively engaged in cooling. In flows that connect a point to a volume or an area, the resulting structure is a tree with high conductivity branches and low-conductivity interstices.tm201

Development and evaluation of GIS-based models for planning and management of coastal aquaculture : a case study in Sinaloa, Mexico

This study describes the development and exploration of environmental and socioeconomic land-based models, implemented in a Geographical Information System (GIS) for coastal aquaculture development at two planning levels using the State of Sinaloa, Mexico as an example. At a state-level, a very large database was constructed and models were created which focused on different themes: natural resources, land uses, social impacts, production modifiers and market potential. These models enabled multi-criteria decision-making of land allocation for aquaculture. In assessing final aquaculture site considerations models identified wider management options and resolved conflicts of land allocation and land use between production activities competing for resources through the use of multi-objective land allocation decision-making techniques. At a site-level, the Huizache-Caimanero lagoon system was identified by the state-level models as being a suitable site for testing the state model's accuracy. Moreover, these smaller more detailed models showed potential to model the wider effects of an activity and clearly had potential for dynamic modelling of environmental impacts. To evaluate the spatial accuracy and primary data content of the site-levels models and consequently the state-level models a Global Positioning System (GPS) was programmed in Stirling for use in Sinaloa through which it was possible to update and/or modify the database and confirm the general accuracy of the models. This study objectively showed the extent of opportunities for land-based aquacuiture in Sinaloa and further demonstrates the usefulness of GIS as an aquaculture planning tool. Model programming was found to be a very useful tool, enabling regeneration of multiple scenarios very quickly. In general, creating submodels for criteria in natural groupings such as water availability, water quality, etc., allowed the user to evaluate and manipulate these criteria before integrating them into a general model. Thus, spatial modelling provided a more comprehensive and integrated treatment for aquaculture development criteria than is usually possible by manual processing. Overall, it was found that GIS can be used to assess and direct aquaculture development very comprehensively and has enormous potential in aquaculture and related studies