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The paper deals with the critical parameter tracking problem which arises when online identification strategies are used to model the dynamics of the power system. A tracking constrained identification scheme is proposed to achieve a smooth model transition under operation schedule change or disturbances. Based on the identified model, an adaptive PSS is designed by using an improved self-optimising pole shifting control algorithm and tested on a multimachine power system. Behaviour of the adaptive PSS and its coordination ability with other PSSs in the system are discussed and demonstrated.

Eight commercially available selenides, a selenol, and selenourea were examined for substrate activity with purified pig liver flavin-containing monooxygenase (FMO). While none of the aromatic heterocyclic selenides tested showed detectable activity, all dialkyl- and alkylaryl-selenides free from ionic groups stimulated NADPH- and FMO-dependent oxygen uptake. With limiting substrate the molar ratio of oxygen reduced to selenide added was 1:1. Analysis of products from N-[2-(methylseleno)ethyl]benzamide demonstrated that the selenide was quantitatively oxidized to selenoxide. Further oxidation of either the FMO-generated or synthetic selenoxides was not detected. The dialkyl- and alkylaryl-selenoxides are potent thiol oxidants and reaction rates for the oxidation of thiols by methylphenylselenoxide and N-[2-(methylseleninyl)ethyl]benzamide followed second order kinetics with rate constants from 3-4 × 103 M−1 s−1 at pH 7.4, 37°C. The rapid oxidation of thiols by these selenoxides demonstrates that the oxidation of selenides to selenoxides catalyzed by crude tissue preparations can be measured by following selenide-dependent oxidation of thiocholine by the procedure described earlier for the oxidation of thiourea (WXA Guo and D. M. Ziegler, 1991, Anal. Biochem. 198, 143-148). Activity measurements by this procedure indicated that the oxidation of dialkyl selenides by rat, guinea pig, or pig liver microsomes was catalyzed primarily by a monooxygenase with the properties of FMO. However, from 20 to 40% of the microsome-catalyzed oxidation of selenides bearing aryl substituents was sensitive to N-benzylimidazole, suggesting that P450-dependent monooxygenases also contribute, at least in part, to the oxidation of these xenobiotics.Copyright 1994, 1999 Academic Press, Inc.

Control limit constraints exist in nearly all practical systems. Using a concept of short-term behaviour index, their influence on the closed-loop system performance is investigated. With the proposed dynamic control limits method, control limit constraints can be adequately considered in the discrete controller design process. A general discrete model with time delay and coloured noise are of most interest and are discussed in detail. Combining the advantages of both minimum variance and pole assignment control strategies, a pole-shifting control algorithm is proposed. Successful application of the proposed method to several examples demonstrates its valuable features.