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Power Balance (power + balance)
Selected AbstractsMaintaining the power balance in an ,empty network'EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2006M. Reza Abstract This paper presents the concept of an ,empty network' and shows how the power balance can be maintained in such a system. In this study, an ,empty network' is defined as a power system in which no rotating mass is present; all generators are grid-connected via power electronic interfaces. One generator creates a neat 50,Hz voltage that serves as a frequency reference for the other generators. Consequently, a power unbalance cannot be detected in the classical way, as an altered system frequency. Therefore, in this paper, voltage deviations are used to detect the power unbalances. Simple test systems that consist of 1, 2 and 3 buses are applied on a real time digital simulator (RTDS). A load jump is simulated to cause a power unbalance in the system. The study shows that by using voltage deviations as control signals, the power balance can be maintained in an empty network. Copyright © 2006 John Wiley & Sons, Ltd. [source] Unit commitment at frequency security conditionEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2001X. Lei In island grids and weakly interconnected power systems, the loss of a large proportion of generation will cause the system frequency to fall dramatically. In order to ensure a stable operation with the lowest impact to the system, the disturbed power balance must be equalized within a short specified time by activating the second-reserve of on-line units or by load shedding or both. Unit commitment procedures shall consider these factors to ensure a reliable power supply while minimizing the fuel costs. This paper presents a unit commitment procedure taking the frequency security condition of systems into account. The procedure commits and optimizes units, calculates necessary second-reserve capability, and allocates them among the available on-line units. Parallel to the minimization of daily fuel costs, a specified frequency minimum following the loss of generation is employed as a criterion for maintaining system security. A case study on typical island systems with a large number of different units is demonstrated using the proposed procedure. Results from the study validated robust performance of the proposed procedure that minimizes fuel costs while maintaining frequency security condition. This paper considers only the frequency security condition to be handled. However, it can also be extended with other criteria such transmission capability during transient conditions of interconnected systems. [source] A fractal comminution approach to evaluate the drilling energy dissipationINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2002Alberto Carpinteri The drilling comminution is theoretically and experimentally analysed by a fractal approach. An extension of the Third Comminution Theory is developed to evaluate the energy dissipation in the process: it occurs in a fractal domain intermediate between a surface and a volume. The theoretical assumption of a material ,quantum' is experimentally observed. The experimental fragment analysis evidences the characteristic size of separation between primary cutting and secondary milling. A global power balance for the drilling process is also presented and permits the prediction of drilling velocity. It shows also how the dissipation energy density (drilling strength) is not a constant parameter, but decreases considerably with the size scale. Copyright © 2002 John Wiley & Sons, Ltd. [source] Theoretical facet and experimental results of harmonic tuned PAsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2003Paolo Colantonio Abstract High-efficiency power amplifier design criteria imply a synthesis of input and output networks with particular emphasis on their harmonic behavior. In this article, a simplified approach to clarify the relevance of such terminations is presented. Starting from the implications of power balance for stage performance, design criteria to improve the efficiency of high-frequency applications are presented. In order to validate the approach, comparisons among the performances of single-stage amplifiers, all operated at 5 GHz under a sinusoidal driving signal and synthesized by utilizing different design methodologies, are presented. Drain efficiencies at 1-dB compression of 44.5%, 53.3%, and 61.56% have been measured respectively for the tuned load and harmonically manipulated (2nd and 2nd & 3rd) realized amplifiers, compared with a simulated drain efficiency of 55% using the Class E approach. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 459,472, 2003. [source] September 11, Anti-Terror Laws and Civil Liberties: Britain, France and Germany Compared1GOVERNMENT AND OPPOSITION, Issue 1 2003Dirk Haubrich The attacks on the United States of America in September 2001 have spurred a rapid implementation of new Anti-Terrorism legislation around the world. In an effort to, ostensibly, safeguard against the repetition of similar events on their own territories, many democracies have taken far-reaching legislative steps that might threaten the ideal of liberty on which their societies have traditionally been built. This article examines the laws introduced in Britain, France and Germany to establish the extent to which civil liberties in eight different categories have been curtailed. It concludes that, despite the otherwise similar characteristics of the countries studied, the legal provisions differ significantly in scope and depth, a fact that might be explained by: the different levels of threat perception; Britain's history of anti-terror legislation; and the respective power balances between judiciaries and legislatures. [source] | ||||||||||