PROSPECTS FOR RAPID LARGE DISTURBANCE STABILITY ASSESSMENT.

The increasing complexity of modern interconnected power systems has made on-line stability assessment a requirement to consider seriously in security control. Recent developments in the so-called energy function methods (EFMs) give considerable promise of their suitability for this purpose. This paper will review these advances. Then consideration is given to applying EFMs in a control centre. This will be largely based on current feasibility studies for the Queensland Electricity Commission (QEC) system.link_to_subscribed_fulltex

PROSPECTS FOR RAPID LARGE DISTURBANCE STABILITY ASSESSMENT.

The increasing complexity of modern interconnected power systems has made on-line stability assessment a requirement to consider seriously in security control. Recent developments in the so-called energy function methods (EFMs) give considerable promise of their suitability for this purpose. This paper will review these advances. Then consideration is given to applying EFMs in a control center. This will be largely based on current feasibility studies for the Queensland Electricity Commission (QEC) system.link_to_subscribed_fulltex

Robust, adaptive of nonlinear control for modern power systems

Major objectives in power system control design include regulation of voltages and frequency, adequate damping of oscillations and preservation of synchronism in the face of large disturbances. These objectives must bee met in the face of changing operating conditions some of which may not be anticipated a priori. Further, modern operating schemes will enhance the level of uncertainty. For instance, Flexible AC Transmission Systems (FACTS) will give a variable structure power system to which all controllers must be tuned on-line. It is unlikely that traditional off-line tuning of simple decentralized controllers will be adequate. This paper looks at what some modern control tools have to offer in the power systems context. In particular, we review robust, adaptive and nonlinear control and their possible combinations. Their applicability to various classes of power system control problem is considered. In particular, the type of modelling uncertainty (structured or unstructured) and type of disturbance (small or large) is important. In system theoretic terms there seems to be many opportunities for further use of centralized (and decentralized) nonlinear control.link_to_subscribed_fulltex

Stability analysis of power system loads with recovery dynamics

This paper develops an approach to stability analysis for long-term dynamics of load systems. A novel approach to modelling aggregate dynamic load is used. This leads naturally to differential-algebraic models and an analytical basis which closely ties together static (load flow sensitivity) and dynamic (small and large disturbance) criteria for stability. Further theoretical insights are seen to be possible. A series of examples illustrates the results. © 1994.link_to_subscribed_fulltex

Stability analysis of induction motor networks

This paper presents a stability analysis of power systems where induction motors constitute a main portion of the system load. Various stability questions are analysed in terms of network and induction motor characteristics. The issue of dynamic behaviour of induction motors under low voltage conditions is particularly addressed, highlighting the role of limits on slip variables in identifying and understanding potential (in)stability phenomena. © 1998 Elsevier Science Ltd. All rights reserved.link_to_subscribed_fulltex

Stability theory of differential/algebraic models of power systems

Lyapunov stability results are given for differential/algebraic models of power systems which include the effect of generator damping and nonlinear loads. The global dynamical structure of such a system is studied in terms of multivalued energy functions defined on so-called 'voltage causal regions' where voltage behaviour is predicted from angle behaviour. These regions are separated by 'impasse surfaces' related to singularity in the load flow equations. © 1993 Indian Academy of Sciences.link_to_subscribed_fulltex

Properties of quadratic equations and their application to power system analysis

A number of facts about quadratic algebraic problems and applied Newton-Raphson like methods are presented. The main results are about solution structure, loading trajectories, load flow feasibility boundaries and Newton-Raphson solutions. Various practically important applications of these properties are discussed. Although motivated by power flow problems, the results are valid for any problem described by an algebraic system of quadratic equations.link_to_subscribed_fulltex

Investigations of load-tap changer interaction

This paper explores the dynamic behaviour of loads and tap changers during the process of voltage collapse in power systems. Using an exponential recovery load model representing the dynamic behaviour of aggregate loads, the mechanism of voltage collapse is illustrated. Dynamic interaction between loads and transformers is investigated. Based on such dynamic considerations, a tap locking strategy is proposed which ensures that voltage collapse does not occur. Investigations focus on determining a critical value of tap position such that locking at a smaller value of tap results in stable behaviour, but locking at a larger value results in voltage collapse.link_to_subscribed_fulltex

Stability theory of differential/algebraic models of power systems

Lyapunov stability results are given for differential/algebraic models of power systems which include the effect of generator damping and nonlinear loads. The global dynamical structure of such a system is studied in terms of multivalued energy functions defined on so-called 'voltage casual regions' where voltage behaviour is predicted from angle behaviour. These regions are separated by 'impasse surfaces' related to singularity in the load flow equations.link_to_subscribed_fulltex