Efficient algorithms are presented for the solution of two important problems in the area of damping control of electromechanical oscillations in large-scale systems. The proposed algorithms allow the determination of: the most suitable generators for installing power system stabilizers; the most suitable buses in the system for placing static VAr compensators in order to damp the critical modes of oscillation. These algorithms involve the calculation of transfer function residues and represent an important extension of the powerful methodology described by V. Arcidiaconos et al. (see IEEE Trans. Power Apparatus and Systems, vol.PAS-99, p.769-78, 1980), whose use was up to now restricted to power systems of limited size. A major advantage of this methodology is that there is no limitation on the degree of modeling of the power system being studied. >

Determination of suitable locations for power system stabilizers and static VAr compensators for damping electromechanical oscillations in large scale power systems

Selective Modal Analysis (or SMA) is a physically motivated framework for understanding, simplifying and analyzing complicated linear time-invariant (or LTI) models of dynamic systems [1,2,3]. SMA allows one to focus on any prespecified dynamic pattern of intrest in the model. In particular, One can efficiently and accurately compute the eigene values and eigenvectors of the natural modes of interest and their sensitivities, and also determine physically meaningful reduced order models containing these natural modes. SMA is particularly suitable for dealing with composite models, i.e. models consisting of several dynamic subsystems interrelated by static constraints. An introduction to the basic concepts of SMA pertinent to the applications being considered here is presented in the companion paper [3]. This paper concerns the application of SMA to the Dynamic Stability problem in electric power systems; it is shown how SMA is well suited to meet the demanding requirements of Dynamic Stability analysis. This is illustrated in [3] with examples, including a 60-machine model of a dynamic instability occurrence in an actual power system.

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Selective Modal Analysis With Applications to Electric Power Systems, Part II: The Dynamic Stability Problem

Techniques are presented for the evaluation and interpretation of eigenvalue sensitivities, in the context of the analysis and control of oscillatory stability in multimachine power systems These techniques combine the numeric power of model analysis of state-space modals with the insight that can be obtained from transfer-function descriptions Relationships with tools from selective model analysis (namely, participations) are stressed Examples of applications to a detailed multimachine power system model are given >

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On sensitivities, residues and participations: applications to oscillatory stability analysis and control

The application of superconducting magnet energy storage (SMES) to the stabilization of a power system with long-distance bulk power transmission lines which has the problem of poorly damped power oscillations is presented. Control schemes for stabilization using SMES capable of controlling active and reactive power simultaneously in four quadrant ranges are proposed. The effective locations and the necessary capacities of SMES for power-system-stabilizing control are discussed in detail. Results of numerical analysis and experiments in an artificial power-transmission system demonstrate the significant effect of the control by SMES on the improvement of power-system oscillatory performance. >

Application of superconducting magnet energy storage to improve power system dynamic performance

A design method to lay emphasis on a differential geometric approach for decentralized nonlinear optimal excitation control of multimachine power systems is suggested in this paper. The control law achieved is implemented via purely local measurements. Moreover, it is independent of the parameters of power networks. Simulations are performed on a six-machine power system. It has been demonstrated that the nonlinear optimal excitation control could adapt to the conditions under large disturbances. Besides, this paper has verified that the optimal control in the sense of LQR principle for the linearized system is equivalent to an optimal control in the sense of a quasi-quadratic performance index for the primitive nonlinear control system.

Decentralized nonlinear optimal excitation control

This paper addresses the problem of the most effective selection of generating units to be equipped with excitation system stabilizers in multimachine systems which exhibit dynamic instability and poor damping of several inter-machine modes of oscillation. Practical means have been developed using eigenvalue analysis techniques to guide the selection process. The linear state space matrix is derived directly from perturbation of the states of a large scale power system dynamic simulation and a subset of this matrix is used to yield the sensitivity of damping ratios of eigenvalues to stabilization measures in individual machines.

Coordinated Application of Stabilizers in Multimachine Power Systems

Different numerical techniques for power system dynamic simulation are described. Examples of large-scale system simulations using the extended term simulation option of the power system simulation program (PSS/E) which incorporates these features are presented. Sample results from the simulation of a 2941-bus, 831-machine system are given. >

T.F. Laskowski

Papers

Coordinated Application of Stabilizers in Multimachine Power Systems

Simulating fast and slow dynamic effects in power systems