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Characterization of the dynamic phenomena that arise when the system is subjected to a perturbation is important in real-time power system monitoring and analysis. This paper discusses the use of Hilbert spectral analysis to visualize and characterize nonlinear oscillations from synchronized wide-area measurements. The method has the potential to be applied for real-time, wide-area monitoring and analysis. As an illustrative example, synchronized phasor measurements of a real event in northern Mexico are used to examine the potential usefulness of nonlinear time series analysis techniques to characterize the time evolution of nonlinear, nonstationary oscillations and to determine the nature and propagation of the system disturbance. The proposed approach is also compared with Prony analysis. Index Terms--Interarea oscillations, spectral analysis, wide-area measurements.

A new approach to online assessment and control of transient oscillations is proposed. It relies on coupling Prony analysis and the SIME transient stability method, with the twofold objective: on one hand, to improve Prony's applicability and reliability, and on the other hand, to design generation rescheduling patterns able to enhance the damping of poorly damped oscillations and/or stabilize them. Simulations performed on two different systems illustrate the technique and show main features: accuracy, ability to uncover and assess the influence of system machines' generation on damping, and compatibility with real-time requirements. Comparison of the results obtained by the proposed approach with conventional eigenanalysis techniques is provided. Additional method's interesting byproducts are also discussed. Index Terms--Control of poorly damped oscillations, damping assessment, modal identification, Prony analysis, SIME method, transient stability.

A general approach to real-time transient stability control is proposed, and two complementary techniques are devised: one for preventive, the other for emergency control. In this paper, the general transient stability control approach is first revisited then applied to real-time preventive control. The technique consists of shifting active power generation. The amount of power and the machines from which to shift it are methodically determined, and various patterns of generation decrease/increase are considered. Further, a standard OPF algorithm is combined with this control technique to get a real-time transient stability-constrained OPF software, able to meet power system security and electricity market requirements. Simulations conducted on the 88-machine EPRI system and the Mexican interconnected power system illustrate the various techniques, highlight their specifics, and assess their performance. Index Terms--DSA, preventive control, SIME method, transient stability, transient stability control, transient stability-constrained OPF.

The transient stability-constrained dispatch of an electric power system is a problematic task for the system operator who, under economic pressure, may be reluctant to take expensive preventive actions against very harmful contingencies. The open-loop emergency control (OLEC) technique proposed in this paper aims to relieve such preventive actions by complementing them with emergency ones. This is achieved by combining generation rescheduling, assessed and taken preventively, with generation tripping, assessed preventively but triggered only if the anticipated harmful contingency actually occurs. The relative size of preventive versus emergency control may be modulated so as to furnish panoply of solutions. Besides, the technique may stabilize simultaneously many contingencies. Simulations conducted on the EPRI 88-machine system illustrate various possibilities of the OLEC technique and compare it with the purely preventive one. Tradeoffs between preventive control and OLEC are also discussed, especially in the context of liberalized electricity markets. It is shown that OLEC is indeed able to provide a good compromise between economics and security, and to realize important savings. Index Terms--DSA, liberalized electricity markets, open loop emergency control, preventive control, SIME method, transient stability, transient stability control.

This paper proposes a steady state method as a solution to the problem of initializing the dynamic models of induction motors in transient stability studies. The results of the proposed method are compared to those obtained by two conventional initialization methods that are used in current production grade simulation programs, in a test power system that includes an industrial subsystem with a significant amount of induction motor loads. It is also shown in this paper that using a correct initialization method for these dynamic devices is important, because the choice of the method can modify the results of the dynamic time-domain simulation, and therefore the assessment of power system stability. Index Terms--Induction motor models, numerical initialization, power flow methods, transient stability simulation.

This paper proposes a unified approach to contingency filtering, ranking and assessment in power system transient stability studies. The approach consists of two-block techniques in which the first block selects from a list of contingencies the a priori 'interesting' ones, that the second block ranks and assesses. This Filtering, Ranking and Assessment (FILTRA) approach relies on SIME (for SIngle Machine Equivalent). SIME is a hybrid direct-time-domain stability method which combines accuracy and flexibility skills of time-domain methods with sound additional possibilities of direct methods. The FILTRA approach is fully general: it may adapt itself to the specifics of any power system (modeling, protection characteristics, etc.), any contingency scenario and mode of (in)stability (first- or multi-swing, local or inter-area mode) and any application context (planning, operation planning and real-time operation). The approach is illustrated on two EHV power systems, having different structures, control and protective devices. The adequacy of its filtering and ranking capabilities is illustrated in terms of performance criteria such as reliability (ability to consistently capture all dangerous contingencies), effectiveness (ability to avoid false alarms) and computational efficiency (ability to comply with real-time requirements). Further, the assessment task is shown to provide the operator with sound information and effective means of control. Index Terms--Contingency filtering and ranking, dynamic security assessment, power system transient stability assessment and control, SIME method.

This paper presents a new approach to transient stability control using global transient stability-constrained optimal power flow (TSC-OPF) methods. Its novelty consists in using the single machine equivalent (SIME) method to perform (and improve) two main important functions of global TSC-OPF approaches: first, SIME is used to efficiently perform the power system transient stability analysis; second, SIME determines a stable one machine infinite bus equivalent rotor angular trajectory that is used as the reference stability constraint, at one specific integration step. In this way, the stability constraint is adjusted by SIME, at each iteration of the TSC-OPF method, in order to accurately reflect power system dynamic behavior. The prowess and main characteristics of the proposed approach are shown by numerical examples. [ABSTRACT FROM AUTHOR]