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With the increase in the monitoring of operational data at very high rates in high voltage substations and the ability to time synchronize these data with global positioning systems, there is a growing need for transmitting this data for monitoring, operation, protection, and control needs. The sets of data that need to be transferred and the speed at which they need to be transferred depend on the application--for example, slow for postevent analysis, near real rime for monitoring and as close to real rime as possible for control or protection. In this paper, we describe GridStat, a novel middleware framework we have developed to provide flexible, robust, and secure data communications for the power grid's operations. Test results demonstrate that such a flexible framework can also guarantee latency that is suitable for fast wide-area protection and control. Index Terms--Computer control of power systems, distributed control, energy-management systems, power system measurements, power system monitoring, power system protection, quality of service (QoS), supervisory control and data-access (SCADA) systems, wide-area control.

This paper deveiops a systematic procedure of designing a centralized damping control system for power grid interarea oscillations putting emphasis on the signal selection and control system structure assignment. Geometric measures of controllability/observability are used to select the most effective stabilizing signals and control locations. Line power flows and currents are found to be the most effective input signals. The synthesis of the controller is defined as a problem of mixed [H.sub.2]/H[infinity] output-feedback control with regional pole placement and is resolved by the linear matrix inequality (LMI) approach. A tuning process and nonlinear simulations are then used to modify the controller parameters to ensure the performance and robustness of the controller designed with linear techniques. The design process is tested on the New England 39-bus ten-machine system. Index Terms--Damping controller, interarea oscillations, robust control, wide-area control, wide-area measurements.

In this paper, we present the design of a localized competitive market for reactive power ancillary services at the level of individual voltage-control areas. The concept of electrical distance has been used to identify the different voltage-control areas within a power system. The proposed reactive power market is settled on uniform price auction, using a modified optimal power-flow model. Uniform prices for various components of reactive power service are obtained for each voltage-control area. In the study cases described in the paper, we examine whether such a localized reactive power market is more desirable than a common system-wide reactive power market. Index Terms--Ancillary services, deregulation, market design, reactive power, voltage-control areas.

The problem of defining and classifying power system stability has been addressed by several previous CIGRE and IEEE Task Force reports. These earlier efforts, however, do not completely reflect current industry needs, experiences and understanding. In particular, the definitions are not precise and the classifications do not encompass all practical instability scenarios. This report developed by a Task Force, set up jointly by the CIGRE Study Committee 38 and the IEEE Power System Dynamic Performance Committee, addresses the issue of stability definition and classification in power systems from a fundamental viewpoint and closely examines the practical ramifications. The report aims to define power system stability more precisely, provide a systematic basis for its classification, and discuss linkages to related issues such as power system reliability and security. Index Terms--Frequency stability, Lyapunov stability, oscillatory stability, power system stability, small-signal stability, terms and definitions, transient stability, voltage stability.

In this paper, the objectives and detailed analysis of the multistage distribution expansion are presented. The problem is modeled as a directed graph minimum edge cost network flow problem. This new formulation details a multistage framework within a single mathematical program while addressing several deficiencies of previous approaches. The accuracy of a single step approximation of the objective function, without using the conventional linearization techniques, is discussed. Each of the constraints is introduced in terms of industry standard practices. Detailed numerical results for practical study cases are provided in a separate paper. Index Terms--Power system planning, distribution expansion, multistage planning, mixed integer mathematical programming.

In this paper, the numerical analysis of a multistage formulation of the distribution expansion problem developed is presented. The approximate objective function is employed without sacrificing optimality. A complete nonlinear mathematical programming optimization is employed to identify the global optimum. The algorithm is applied here to two practical test cases. Details of the input data and configuration of test systems as well as the solutions are listed and discussed. Computational considerations are addressed. Index Terms--Distribution expansion planning, mixed integer mathematical programming, multistage planning.

With deregulation of the power generation sector, the necessity for an enhanced and open communication infrastructure to support an increasing variety of ancillary services is apparent. A duplex and distributed communication system seems to be the most suitable solution to meet and ensure good quality of these services. Parameters needed and additional limits introduced by this new communication topology must be investigated and defined. This paper focuses on the communication network requirements for a third party load frequency control service. Data communication models are proposed based on queuing theory. Simulation is performed to model the effects of certain types of signal delays ancillary service, on this Index Terms--G/G/1 queues, load frequency control, network delays, queueing theory.

This paper resulted from the research aimed at introducing modeling and simulation as a major methodological approach for enhancing power engineering education. The reasons for such an approach are explained first. Different options and uses of the modeling and simulation tools are discussed next. Several implementations of the teaching examples are outlined. The paper ends with the conclusions reached based on the study. Index Terms--Load-flow analysis, modeling, power engineering education, power system transients, protection, simulation, stability, state estimation.

Fast contingency screening is expected to be an integral part of any practical on-line dynamic security analysis (DSA). Ranking of contingencies requires the use of severity indices, and for DSA such an index must be a measure of stability. From experience in static security analysis, it is well known that some indices work better than others for particular power systems and that combinations of indices usually work better than a single index. For DSA, which is still in its infancy, severity indices are more complex and very few have been tested for screening. In this paper, several indices are proposed for contingency screening in online DSA. These indices are based on the concepts of coherency, transient energy conversion between kinetic energy and potential energy, and three dot products of system variables. Test results on realistic power systems show the promise of these indices in contingency screening. Keywords: Dynamic Security Analysis, Transient Stability, Contingency Screening, Severity Index.

At present, the computational requirement for dynamic security assessment (DSA) is a hurdle for a comprehensive on-line DSA to be implemented in Energy Management Systems. In addition to faster time domain solutions, novel approaches and techniques are being developed for contingency screening and remedial actions. This paper describes one such development in the area of contingency screening which can be seen as an extension of techniques developed over the years for static security analysis. Some new concepts and methods are suggested for both contingency ranking and contingency classification (stable/unstable). Results from realistic test systems illustrate the capabilities and performance of the new approach. Key words: Severity Index, Contingency Screening, Dynamic Security Analysis, Artificial Neural Network

Parallel processing to obtain time domain simulation of power system dynamic behavior has been studied for over a decade. In this paper, a parallel across space implementation of a Waveform Relaxation (WR) based algorithm is presented. The algorithm can take full advantage of the inherent properties of power systems, such as coherency grouping and localized fault response, thus significantly speeding up the simulations. In the proposed implementation, a system is broken up into several subsystems based on its coherency, and then each processor is devoted to the computation of the waveform of each subsystem. This is the first time the WR algorithm has been implemented on a parallel machine (Sequent Symmetry S81) and tested on large power systems. The numerical results show very promising performance compared with the commonly used Very Dishonest Newton algorithm, with overall speedups of up to 27 obtained for a 2500-bus system using 20 processors. Keywords Waveform relaxation, parallel processing, dynamic simulation, network partitioning, multiple stepsizes.

Open transmission access is a legal requirement in the United States, but is not fully implemented. Discussion of deregulation has so far focused principally on the tariff structure for transmission access, but operating the power system in this new environment will present significant problems of an almost purely technical nature. Something as simple as frequency control becomes challenging when implemented in the competitive, distributed control environment that true third party wheeling creates. This paper seeks to identify likely deregulation scenarios, identify the technical issues associated with Load Frequency Control, and identify technical solutions, such as standards and algorithms, needed for the operation of this key component of national infrastructure in the face of profound structural changes.

The W-matrix method has the potential to be efficient for parallel computing as a substitute for the precedence stringent substitution schemes, which are being commonly used on sequential computers for the solution of sparse linear matrix equations, with the support of appropriate reordering and partitioning algorithms. In this paper, the factors which may affect the performance of the W-matrix method are examined first. A bus reordering and partitioning scheme is then proposed which is aimed at reducing the fill-ins in both the triangular matrices L and U and the W-matrices and adjusting the patterns of the W-matrices for better parallel efficiency. Tests conducted on a shared memory parallel computer proved the effectiveness of the proposed algorithm for various systems. Test results are presented and discussed. Key words: parallel algorithms, linear systems, factorization and substitution, sparse techniques, partial matrix inversion

This paper focuses on determining the correctability of bus voltage violations during the contingency selection process. The present day strategy in the contingency selection function consists of flagging the worst contingency cases for further detailed analysis, when preventive and/or corrective actions are obtained. The worst contingency cases are the ones which bear a large severity or performance index (PI). However, one must take into account that contingencies with a large PI may be easily correctable, whereas contingencies with small PI, that had not even been flagged, may be noncorrectable. Thus, the selection process should flag not only those contingencies with large PI but also those that are not easily correctable. In a previous paper, it was shown that correctability of line overloads can be determined using a first order sensitivity approach with an acceptable increase in contingency selection time. In this paper, the correctability of voltage violations is addressed. Because o the nonlinearities, the algorithm used here requires more calculations than the correctability of real power violations, but the additional time needed for the selection process is still quite acceptable for on-line purposes. The paper describes the algorithm, and provides test and timing results.

This paper presents a generic bipolar or monopolar multi-terminal multi-converter High Voltage Direct Current (HVDC) system model suitable for Operator Training Simulators (OTS). This model is designed to train operators for AC-DC system operations and controls so that they can take appropriate actions quickly under emergency conditions. This model was developed for the Electric Power Research Institute (EPRI) OTS and can handle the most complex HVDC configurations and controls like those, for example, in the Pacific Intertie.

In on-line contingency analysis, it has become quite common to screen contingencies by ranking them according to some severity (or performance) index, which is calculated solely as a measure of limit violations. Quite often, however, even large limit violations may not be of concern if they are easily correctable whereas indications of noncorrectable violations may require preventive action. This paper focuses on the idea of correctability of contingencies with limit violations. A fast and efficient method for the correction of line loading limit violations based on sensitivity factors and contingency screening techniques using sparse vector handling is presented. The results show that the additional information about correctability of contingencies can be obtained at a low computational cost.

Many problems in transient network analysis are characterized by the solution of a simultaneous set of coupled algebraic and ordinary differential equations. The urgent need for on-line applications has motivated power system researchers to develop algorithms which can be implemented on parallel computers. Traditional algorithms for simulating power system dynamics do not readily lend themselves to parallel processing and only a limited amount of parallelism can be achieved. In this paper, a class of algorithms which exploits the concurrent solution of many time steps is presented. By applying a stable integration method, the overall algebraic-differential set of equations can be transformed into a unique algebraic problem at each time step. The dynamic behavior of the system can be obtained by solving an enlarged set of algebraic equations relative to the simultaneous solution of many time steps. A class of relaxation/Newton algorithms can be used to solve this problem efficiently. Furthermore, this formulation permits, easily, the implementation of multigrid techniques. Theoretical aspects about the convergence rates and computational complexity of the proposed algorithms are discussed in the paper. Test results on realistic power systems confirm theoretical expectations and show the promise of a several-fold increase speed over that obtainable by traditional parallel-in-space approaches. The synergism obtainable by parallelism in time and in space can allow high speed-up adequate for on-line implementations of transient stability analysis.

A dynamic partitioning method for a large electric power system is used to improve transient stability analysis by using separate step sizes for various portions. Coherent groupings which are assigned in clusters are used to divide the system. These groups are computed at dissimilar integration rates based on their proximity to the fault. The method is used on the IEEE 118 bus system and a 662 bus system and was run on an Alliant FX/8 computer. Results show that the solution for the 118 bus system was quicker but partitioning was more efficient for the 662 bus system with a speedup of 33.5.

The current status of parallel processing as used in electric power systems analysis is presented. The use of parallel processing is induced by the need for rapid solution in power system problems. For a specific problem, a separate derivation has to be made that could be used as a parallel algorithm. The answer has to done in a parallel machine with compatible architecture and algorithms. The last decade has seen research done on algorithm development and the evaluation of multiprocessor architectures has just began. Hardware development still has no definite path with existing machines suitable only for research work.

This paper presents a fast method for use in on-line voltage security assessment. The objective here is to quickly assess the effects of large numbers of contingencies (line outages) to determine the worst case. The methodology is intuitively focused on the relationship between a node voltage and the availability of reactive power in the local neighborhood, and it also takes advantage of other information from the power flow solution. The concept of electrical distance is introduced for choosing the corresponding voltage control area locally around the contingency event. For the calculation of post-contingency electrical distance and power flow, the computation efficiency can be achieved by utilizing many mature algorithms from Static Security Analysis (SSA). Index Terms--Adaptive bounding, electrical distance, power flow, reactive reserves, voltage security.

In the ongoing process to create a competitive electricity market, the problem of Ancillary Services is assuming a fundamental role. Ancillary Services are those services performed by generators, transmission and control equipment, which are necessary to support basic services and to maintain reliable operations and system security. In this paper, we focus our attention on one of these services, load following, and propose a competitive way to provide this service through bilateral contracts between supplier and customer. In general, we assume that there will be both a competitive market for the provision of load following and an authority responsible for the amount of load following not met by bilateral contracts.

An introduction is presented in which the editor discusses various reports within the issue on topics including planning and operating approach for active distribution grids, voltage control for photovoltaic inverters, and optimal scheduling model of microgrid considering battery lifetime.

Accurate bus-oriented, three-phase modeling of power systems is desirable for advanced applications and has become practical due to increased computational capability. To assist research activities in this area, this paper presents a benchmark three-phase test system. The proposed system is based on the 24-bus IEEE Reliability Test System that has been converted into a 24-substation, breaker-oriented, three-phase model. The model is available in electronic form at the site: http:llpscal.ece.gatech.edu/testsys/. The proposed model is intended for use in research for three-phase power flow analysis, reliability analysis, fault analysis, transient stability, evaluation of fault currents through specific breakers, risk assessment of breaker failures, and other applications. [ABSTRACT FROM AUTHOR]