This paper deals with the lacement of a minimal set of phasor measurement units PMU9sT so as to make the system placed at a bus measures the voltage as well as all the current phasors at that bus, requiring the extension of the topological observability theory. This concerns the extension of the concept of spanning tree'to that of spanning measurement subgraph with an actual or a pseudo-measurement assi ned to each of its branches. The minimal PMU set is found t%rough a dual search algorithm which uses both a modified bisecting search and a simulated annealing-based method. The former fixes the number of PMU's while the latter looks for a placement set that leads to an observable network for a fixed number of PMU's. In order to accelerate the procedure, an initial PMU placement is provided by a graph-theoretic procedure which builds a spanning measurement subgraph according to a depth-first search. From computer simulation results performed on various test systems it appears that only one fourth to one third of the system buses need to be provided with PMU% in order to make the system observable. measurement model observabe, \ and thereby linear. A PMU -INTRODUCTIONPresently, the supervision of a power system is performed through an open-loop type centralized control. The control actions are taken by the operators with the help of computer-aided software programs that implement steadystate security functions 1). This is due to the fact that the to capture only quasi-steady state operating conditions, preventin the monitoring of transient phenomena. With the advent o f real-time Phasor Measurement Units PMU's), fast transients can be tracked at high sampling rates 121. Hence, it becomes possible to close the loop, that is, to perform an automatic monitoring and control of the system. This is a faster-than-real-time control that aims at steering the system away from transient or voltage instability through corrective actions initiated during an emergency state. A prerequisite to system monitoring and control is the development of an adequate meter placement scheme. Various lacement methodologies have been proposed in the literature P 2-61. Most of them advocate the use of pilot points located at the center of the coherent regions of a system. These re 'om either contain load buses with similar voltage trends for vogage stability analysis or encompass groups of stiffly interconnected machines with common slow modes of oscillations for transient stability analysis. The only control that has so far been implemented is the secondary voltage control scheme which has been applied to the French [5] and Italian systems [ 6 . Two measurements collected t 6, ough a SCADA system are designed major drawbacks of the coherency approach may be fl oreseen. SM 583-5 PWRS A paper recommended and approved by the IEEE Power System Engineering committee of the IEEE Power Engineering Society for presentation at the IEEE/First, the system may not be decomposable into meaningful clusters, signifying the necessity to monitor all load buses...

This paper summarizes the technical activities of the Task Force on Power System Dynamic State and Parameter Estimation. This Task Force was established by the IEEE Working Group on State Estimation Algorithms to investigate the added benefit of dynamic state and parameter estimation for the enhancement of the reliability, security, and resilience of electric power systems. The motivations and engineering values of dynamic state estimation (DSE) are discussed in detail. Then, a set of potential applications that will rely on DSE is presented and discussed. Furthermore, a unifie framework is proposed to clarify the important concepts related to DSE, forecasting-aided state estimation, tracking state estimation and static state estimation. An overview of the current progress in DSE and dynamic parameter estimation is provided. The paper also provides future research needs and directions for the power engineering community.

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a b s t r a c tModern society relies heavily upon complex and widespread electric grids. In recent years, advanced sensors, intelligent automation, communication networks, and information technologies (IT) have been integrated into the electric grid to enhance its performance and efficiency. Integrating these new technologies has resulted in more interconnections and interdependencies between the physical and cyber components of the grid. Natural disasters and man-made perturbations have begun to threaten grid integrity more often. Urban infrastructure networks are highly reliant on the electric grid and consequently, the vulnerability of infrastructure networks to electric grid outages is becoming a major global concern. In order to minimize the economic, social, and political impacts of large-scale power system outages, the grid must be resilient in addition of being robust and reliable. The concept of a power system's cyber-physical resilience centers around maintaining critical functionality of the system backbone in the presence of unexpected extreme disturbances. Resilience is a multidimensional property of the electric grid; it requires managing disturbances originating from physical component failures, cyber component malfunctions, and human attacks. In the electric grid community, there is not a clear and universally accepted definition of cyber-physical resilience. This paper focuses on the definition of resilience for the electric grid and reviews key concepts related to system resilience. This paper aims to advance the field not only by adding cyber-physical resilience concepts to power systems vocabulary, but also by proposing a new way of thinking about grid operation with unexpected extreme disturbances and hazards and leveraging distributed energy resources. The concepts of service availability and quality are not new, but many recognize the need of resilience in maintaining essential services to critical loads, for example to allow home refrigerators to operate for food conservation in the aftermath of a hurricane landfall. By providing a comprehensive definition of power system resilience, this paper paves the way for creating appropriate and effective resilience standards and metrics.

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