Reconciliation of methods of compensation for PSSs in multimachine systems

Copyright © 2004 IEEESeveral methods for the design of compensation for power system stabilizers (PSSs) are used in practice. The object of this paper is to reconcile the methods and explore their relative advantages and disadvantages. Three methods are investigated: the GEP and the P-Vr frequency response approaches, and the method of residues. It is shown the phase response of a modified GEP transfer function (TF) agrees closely with that of the P-Vr TF, thus providing the basis for the design of a robust PSS. Residues yield only a limited number of phase angles that can be used with confidence for design purposes and are consistent with the P-Vr phase response. The remaining residues for rotor modes are affected by variability of participation factor angles and interactions from other machines. Unlike other methods, the P-Vr approach yields magnitude and phase information that simplifies the synthesis of the PSS TF and yields a robust stabilizer.Michael J. Gibbard and David J. Vowle

Discussion of "The application of power system stabilizers to a multigenerator plant"

M.J. Gibbard et al. comment on the paper by G.J. Rogers (see ibid., vol.15, no.1, p.350-5, 2000). They discuss their application of a different design procedure to the author's four-machine infinite bus system. The original author replies to the comments.M. J. Gibbard and D. J. Vowles, G Roger

Interactions between, and effectiveness of, power system stabilizers and FACTS device stabilizers in multimachine systems

Copyright © 2000 IEEEIn this paper it is shown that interactions occur between stabilizers in multimachine power systems, the stabilizers being power system stabilizers (PSSs), FACTS device stabilizers (FDSs) or both. The interactions, which are identified and quantified, may enhance or degrade the damping of certain modes of rotor oscillation. In particular, interactions between PSSs are found to adversely affect the damping of inter-area modes. The analysis of interactions also provides a practical means for quantifying and assessing simultaneously the relative effectiveness of both PSSs and FDS in damping the rotor modes of oscillation. This is achieved using a stabilizer damping contribution diagram. A theoretical basis is given for the analysis of interactions and the effectiveness of stabilizers; the practical significance and applications are illustrated using a case study on a 3-area, 400 state system having 28 generator groups and a number of FDSs. For systems of more than 600-700 states the modified Arnoldi method is used for eigenanalysis-based calculationsMichael J. Gibbard, David J. Vowles and Pouyan Pourbei

The stratigraphic basis of the Anthropocene Event

This paper outlines the stratigraphic basis of a proposed Anthropocene Event. It considers a diachronous event framework to be more appropriate for understanding the Anthropocene than treating it as a new geological series/epoch. Four general categories of material evidence are identified as of particular relevance: ‘artificial’ strata with natural constituents; humanly modified ground; legacy sediments; and ‘natural’ geo-deposits containing artefactual material. All these arise from the interaction and mixing of human, natural, and hybrid human-natural forces. Taken together, such stratigraphic evidence supports the case for recognising the Anthropocene as an unfolding event

A new 1.6-micron map of Titan’s surface

We present a new map of Titan's surface obtained in the spectral 'window' at ∼1.6 μm between strong methane absorption. This pre-Cassini view of Titan's surface was created from images obtained using adaptive optics on the W.M. Keck II telescope and is the highest resolution map yet made of Titan's surface. Numerous surface features down to the limits of the spatial resolution (∼200–300 km) are apparent. No features are easily identifiable in terms of their geologic origin, although several are likely craters

Complexity of Manipulative Actions When Voting with Ties

Most of the computational study of election problems has assumed that each voter's preferences are, or should be extended to, a total order. However in practice voters may have preferences with ties. We study the complexity of manipulative actions on elections where voters can have ties, extending the definitions of the election systems (when necessary) to handle voters with ties. We show that for natural election systems allowing ties can both increase and decrease the complexity of manipulation and bribery, and we state a general result on the effect of voters with ties on the complexity of control.Comment: A version of this paper will appear in ADT-201

Holocene sea levels and palaeoenvironments, Malay-Thai Peninsula, southeast Asia

Sedimentological and palynological investigations of Great Songkhla Lakes, east coast of the Malay-Thai Peninsula, Southeast Asia, reveal sedimentary sequences rich in palynomorph assemblages dominated by pollen of mangroves and freshwater swamps. Compared with other regions in Southeast Asia the assemblages are of relatively low diversity. Geochronological data indicate that the Great Songkhla Lakes record one of the earliest mangrove environments in Southeast Asia (8420–8190 cal. yr BP), which are subsequently replaced by a freshwater swamp at 7880–7680 cal. yr BP owing to the decline of marine influence. Sea-level observations from Great Songkhla Lakes and other areas of the Malay-Thai Peninsula reveal an upward trend of Holocene relative sea level from a minimum of − 22 m at 9700–9250 cal. yr BP to a mid-Holocene high stand of 4850–4450 cal. yr BP, which equates to a rise of c. 5.5 mm/yr. The sea-level fall from the high stand is steady at c. − 1.1 mm/yr. Geophysical modelling shows that hydroisostasy contributes a significant spatial variation to the sea-level signal between some site locations (3–4 m during the mid-Holocene), indicating that it is not correct to construct a single relative sea-level history for the Malay-Thai Peninsula

Inclusion of higher order terms for small-signal (modal) analysis: Committee report - task force on assessing the need to include higher order terms for small-signal (modal) analysis

© 2005 IEEE.This paper summarizes the work done by the Task Force on Assessing the Need to Include Higher Order Terms for Small-Signal (Modal) Analysis. This Task Force was created by the Power System Dynamic Performance Committee to investigate the need to include higher order terms for small signal (modal) analysis. The focus of the work reported here is on establishing and documenting the practical significance of these terms in stability analysis using the method of Normal Forms. Special emphasis was placed on determining and describing conditions when higher order terms need to be included to accurately describe modal interactions. Test cases were developed on a standard test system to demonstrate the application of appropriate indices to detect the occurrence of nonlinear interaction and hence the need for higher order terms in stability analyzes. The use of the higher order terms in the site selection for a damping controller is also documented.Sanchez-Gasca, Juan J.,Vittal, Vijay; Gibbard, Michael J.; Messina, Arturo Roman; Vowles, David J.; Liu, Shu; Annakkage, Udaya D

Why the Realist-Instrumentalist Debate about Rational Choice Rests on a Mistake

Within the social sciences, much controversy exists about which status should be ascribed to the rationality assumption that forms the core of rational choice theories. Whilst realists argue that the rationality assumption is an empirical claim which describes real processes that cause individual action, instrumentalists maintain that it amounts to nothing more than an analytically set axiom or ‘as if’ hypothesis which helps in the generation of accurate predictions. In this paper, I argue that this realist-instrumentalist debate about rational choice theory can be overcome once it is realised that the rationality assumption is neither an empirical description nor an ‘as if’ hypothesis, but a normative claim