A AS THE ELECTRICAL UTILITY INDUSTRY ADDRESSES ENERGY AND environmental needs through greater use of renewable energy, storage, and other technologies, power systems are becoming more complex and stressed. Increased dynamic changes that require improvements in real-time monitoring, protection, and control increase the complexity of managing modern grids. In an effort to ensure the secure operation of power systems, more attention is being given to voltage management. Voltage management includes addressing voltage stability and fault-induced delayed voltage recovery (FIDVR) phenomena. Deployment of phasor measurement unit (PMU) technology, in combination with recently developed methodologies for tracking voltage behavior, has resulted in improved real-time voltage monitoring, protection, and control. This article describes simple and accurate methodologies based on real-time measurement-and independent of the system model-designed for tracking both slowdeveloping and transient voltage stability conditions under various and changing system confi gurations. Tests with real-time supervisory control and data acquisition (SCADA) and PMU data, as well as data from comprehensive simulation studies, from the Bonneville Power Administration (BPA) and Southern California Edison (SCE) systems show very accurate detection as the system is approaching voltage instability. The calculated reactive power margin and other indices are easily visualized for operator awareness. For quickly developing disturbances, they allow the initiation of fast control and protection actions. This methodology also discriminates well between FIDVR and short-term

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In our recent work [1] we constructed a reduced-order model of the Western Electricity Coordinating Council (WECC) power system using mathematically derived parameters from real Synchrophasor data. These parameters include inter and intra-area impedances, inertias, and damping factors for aggregate synchronous generators representing five geographical, and yet coherent, areas of WECC. In this paper we use this reduced-order model as a tool to design a supplementary controller for a Static VAr Compensator (SVC), located at the terminal bus of one of the aggregate generators. Widearea feedback consisting of phase angle and frequency measurements from Phasor Measurement Units (PMUs) in the other areas is used to design this controller. The objective is to damp the inter-machine oscillation modes of the reduced-order model, which in the full-order system corresponds to inter-area oscillations. The controller input is chosen via statistical variance analysis, and its parameters are tuned to improve the damping factors of the slow modes. The model is implemented in a real-time digital simulator, and validated using a wide range of disturbance scenarios. The closed-loop system is observed to be highly robust to all of these disturbances as well as the

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In this paper we develop a procedure for estimating the parameters (reflection coefficients and travel times) of lossless layered media systems. The estimation criterion is maximum likelihood. It is shown that maximum-likelihood estimates of the parameters of a layer may be obtained by first determining the maximum-likelihood estimate of the upgoing waveform (one of the states) in that layer, and then estimating the parameters from the estimated upgoing waveform as if the estimated waveform is the output of the layer under consideration.A masimumlikelihood state estimator is developed. It is shown that the state waveforms are composed of overlapping wavelets, and estimation of the parameters of a layer is essentially equivalent to estimation of the amplitude and time-delay of the first wavelet in the upgoing waveform of the layer under consideration. A suboptimal maximum-likelihood parameter estimator is developed.It consists of two filters connected in series: a matched filter to treat noise; and a transversal equalizing-filter to correct for wavelet overlapping effects. Numerical results which illustrate the performance of this masimumlikelihood procedure for different noise levels are presented.