56 research outputs found
Emerging Power Electronics Technologies for Sustainable Energy Conversion
This Special Issue summarizes, in a single reference, timely emerging topics related to power electronics for sustainable energy conversion. Furthermore, at the same time, it provides the reader with valuable information related to open research opportunity niches
Emerging Power Electronics Technologies for Sustainable Energy Conversion
This Special Issue summarizes, in a single reference, timely emerging topics related to power electronics for sustainable energy conversion. Furthermore, at the same time, it provides the reader with valuable information related to open research opportunity niches
Design, management and control of energy storage DC nano-grid.
Ph.DDOCTOR OF PHILOSOPH
Design, Implementation and Evaluation of a Microgrid in Island and Grid Connected Modes with a Fuel Cell Power Source
The ability to connect a microgrid to the grid is an important step in the development and evolution of the modern power system. The principle objectives of this research are (1) to simulate a simple microgrid consisting of a PEM hydrogen fuel cell, load and connection to the grid and (2) to evaluate the resulting microgrid control system on a corresponding experimental microgrid.
The microgrid simulation demonstrated that the control algorithms can operate the microgrid in both islanded (VSC with voltage and frequency regulation) and grid connected (VSC with current control for power transfer).
The experimental laboratory microgrid was constructed and operated in real-time performing its black start and managed transitions between island and grid connected modes of operation. The synchronization method adjusted the island microgrid to become in phase with the grid and tracked well under steady state and load changing conditions. The synchronization process brought the island in phase with the grid within 400 ms. Passive island detection was demonstrated with the restoration to grid operation. The grid connected voltage and current THD were under 1%
Toward best practice in the design of tidal turbine arrays
In recent years, much research has focused on the possibility of using arrays
of turbines to generate clean and predictable power from tidal currents. The
first such array is now in development but a number of important questions
remain unanswered. Among these, how should turbines be arranged within
a tidal stream to maximise their collective performance? And what impacts
will such devices have on the marine environment? In beginning to address
these questions, this thesis takes two important steps toward establishing
best practice in the design of tidal turbine arrays.
In the first part of the thesis, the social and ecological impacts of marine
energy development are reviewed. This review highlights the importance of
communication and public engagement in securing support for a marine energy
project and identifies the effects of increasing noise and collision risk
on marine life as the most pressing ecological issues to be addressed.
In the second part, theoretical models of tidal turbines are examined
and a simple numerical model is used to extend existing theories on optimal
turbine arrangement. The shallow water equations are used to simulate flow
through an idealised channel and an actuator disc model is used to represent
a single row of tidal turbines as a line sink of momentum. Optimal
turbine arrangements are then sought for different and increasingly realistic
flow conditions. Results provide new and important insights into the
dynamics of flow through partial-width arrays and suggest that arranging
turbines unevenly within the flow cross-section can increase considerably
their collective power output
NASA Tech Briefs, October 1990
Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical' Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences
COBE's search for structure in the Big Bang
The launch of Cosmic Background Explorer (COBE) and the definition of Earth Observing System (EOS) are two of the major events at NASA-Goddard. The three experiments contained in COBE (Differential Microwave Radiometer (DMR), Far Infrared Absolute Spectrophotometer (FIRAS), and Diffuse Infrared Background Experiment (DIRBE)) are very important in measuring the big bang. DMR measures the isotropy of the cosmic background (direction of the radiation). FIRAS looks at the spectrum over the whole sky, searching for deviations, and DIRBE operates in the infrared part of the spectrum gathering evidence of the earliest galaxy formation. By special techniques, the radiation coming from the solar system will be distinguished from that of extragalactic origin. Unique graphics will be used to represent the temperature of the emitting material. A cosmic event will be modeled of such importance that it will affect cosmological theory for generations to come. EOS will monitor changes in the Earth's geophysics during a whole solar color cycle
- …