United States Department of Energy

About: United States Department of Energy is a government organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Coal & Catalysis. The organization has 13656 authors who have published 14177 publications receiving 556962 citations. The organization is also known as: DOE & Department of Energy.

Modelling and control of variable-speed multi-pole permanent magnet synchronous generator wind turbine

Abstract: Emphasis of this article is on variable-speed pitch-controlled wind turbines with multi-pole permanent magnet synchronous generator (PMSG) and on their extremely soft drive-train shafts. A model and a control strategy for a full back-to-back converter wind turbine with multi-pole PMSG are described. The model comprises submodels of the aerodynamic rotor, the drive-train by a two-mass model, the permanent magnet generator and the full-scale converter system. The control strategy, which embraces both the wind turbine control itself and the control of the full-scale converter, has tasks to control independently the active and reactive powers, to assist the power system and to ensure a stable normal operation of the wind turbine itself. A multi-pole PMSG connected to the grid through a full-scale converter has no inherent damping, and therefore, such configuration can become practically unstable, if no damping by means of external measures is applied. In this work, the frequency converter is designed to damp actively the drive-train oscillations, thus ensuring stable operation. The dynamic performance of the presented model and control strategy is assessed and emphasized in normal operation conditions by means of simulations in the power system simulation tool DIgSILENT. Copyright © 2008 John Wiley & Sons, Ltd.

A practical field guide to thermoelectrics: Fundamentals, synthesis, and characterization

Abstract: The study of thermoelectric materials spans condensed matter physics, materials science and engineering, and solid-state chemistry. The diversity of the participants and the inherent complexity of the topic mean that it is difficult, if not impossible, for a researcher to be fluent in all aspects of the field. This review, which grew out of a one-week summer school for graduate students, aims to provide an introduction and practical guidance for selected conceptual, synthetic, and characterization approaches and to craft a common umbrella of language, theory, and experimental practice for those engaged in the field of thermoelectric materials. This review does not attempt to cover all major aspects of thermoelectric materials research or review state-of-the-art thermoelectric materials. Rather, the topics discussed herein reflect the expertise and experience of the authors. We begin by discussing a universal approach to modeling electronic transport using Landauer theory. The core sections of the review are focused on bulk inorganic materials and include a discussion of effective strategies for powder and single crystal synthesis, the use of national synchrotron sources to characterize crystalline materials, error analysis, and modeling of transport data using an effective mass model, and characterization of phonon behavior using inelastic neutron scattering and ultrasonic speed of sound measurements. The final core section discusses the challenges faced when synthesizing carbon-based samples and the measuring or interpretation of their transport properties. We conclude this review with a brief discussion of some of the grand challenges and opportunities that remain to be addressed in the study of thermoelectrics.

Wind Resource Estimation—An Overview

Abstract: This article gives an overview of the different ways the wind resource at a site can be estimated. Eight separate ways have been identified. Each of these will be described in some detail, and advantages and disadvantages of each of them will be discussed. Copyright © 2003 John Wiley & Sons, Ltd.

Passive Control of Combustion Dynamics in Stationary Gas Turbines

Abstract: This paper summarizes passive methods used to improve the stability of low-emission combustors in stationary power gas turbines. Common passive methods are reviewed, including discussion of control model concepts, application of simple time-lag models, and a review of acoustic dampers. Applications of time-lag modie cations are presented, and limitations of this approach are discussed. Nyquist analysis is used to show how changing the time lag can be confounded by the presence of multiple acoustic modes. Experimental results demonstrating the frequency shifts predicted by Nyquist analysis are also shown. Stabilizing effects of distributed time lags are discussed, along with some e eld applications. A review of acousticdampers showsthat these devices are not widely applied in stationary engines compared to rocket or afterburner combustors, but have shown good results where applied. Nomenclature ¤ AB;C; D, = combustor sections and the acoustic E; F; G transfer matrices that represent these sections; elements of these 2 £2 matrices are identie ed using subscripts Ai;j where i D0;1 and j D0;1 c