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

Britain Says NO: Voting in the AV Ballot Referendum

The purpose of this paper is to explain why voters made the choices that they did in Britains Alternative Vote (AV) referendum on 5 May 2011. The paper utilises four alternative theoretical models to analyse individual voting behaviour. They are described as the cost-benefit, cognitive engagement, heuristics and mobilisation models. The explanatory power of these models is investigated using a large survey data set gathered in the AV referendum study conducted in conjunction with the British Election Study. Multivariate analyses show that all four models contribute to explaining why some people voted in favour of electoral reform, with the cost-benefit model exhibiting particularly strong effects. The conclusion discusses public reactions to the referendum and possible implications of the decisive rejection of electoral reform after a campaign characterised by disaffection and disengagement. © 2011 The Author Published by Oxford University Press on behalf of the Hansard Society. All rights reserved

Small-signal stability, control and dynamic performance of power systems

A thorough and exhaustive presentation of theoretical analysis and practical techniques for the small-signal analysis and control of large modern electric power systems as well as an assessment of their stability and damping performance. Such systems may contain many hundreds of synchronous generators and high voltage power electronics equipment known as FACTS Devices. The book describes new techniques not only for the tuning and analysis of stabilizers for systems with many generators and FACTS Devices but also for their coordination. Of practical interest, these techniques are illustrated with relevant examples based on a multi-machine power system containing FACTS Devices for operating conditions ranging from light to peak load. By introducing new analytical concepts, using examples, and by employing production-grade software, practical insights are provided into the significance and application of various analytical techniques.M.J. Gibbard, P. Pourbeik and D.J. Vowle

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

Enhanced psychological flexibility and improved quality of life in chronic fatigue syndrome/myalgic encephalomyelitis.

OBJECTIVE: Psychological Flexibility (PF) is a relatively new concept in physical health. It can be defined as an overarching process of being able to accept the presence of wanted/unwanted experiences, choosing whether to change or persist in behaviour in response to those experiences. Associations between processes of PF and quality of life (QoL) have been found in long-term health conditions such as chronic pain, PF has not yet been applied to Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME). METHODS: Changes in PF, fatigue severity and QoL were examined in one hundred and sixty-five patients with CFS/ME engaged in a six-week outpatient interdisciplinary group treatment programme. Participants were assessed using a series of self-report measures at the start of the start (T1) and end of a six-week programme (T2) and at six months follow up (T3). RESULTS: Significant changes in PF and QoL were observed from pre-treatment (T1) to post treatment follow-up (T2 and T3); changes in fatigue severity were observed from T1 to T3 only. Controlling for fatigue severity, changes in the PF dimension of activity/occupational engagement were associated with improvement in QoL at six month follow up (T3) but not at six weeks post programme (T2). CONCLUSION: Findings indicate an interdisciplinary group treatment approach for people with CFS/ME may be associated with improved QoL, processes of PF and fatigue severity, supporting a link between PF and long term health conditions. Results highlight links between PF and patient QoL in CFS/ME and the value of interdisciplinary treatment approaches in this patient population