M.G. Lauby

On-line power system security analysis

A broad overview of on-line power system security analysis is provided, with the intent of identifying areas needing additional research and development. Current approaches to state estimation are reviewed and areas needing improvement, such as external system modeling, are discussed. On-line contingency selection has become practical, particularly for static security. Additional work is necessary to identify better indices of power system stress to be used in on-line screening filters for both static and dynamic security analysis. Use of optimal power flow schemes to recommend optimal preventive and corrective strategies is presented on a conceptual level. Techniques must be further developed to provide more practical contingency action plans, which include real-world operating considerations and use a reasonably small number of control actions. Techniques must be developed for costing operating variables which are not easily quantified in dollars. Soft or flexible constraints and time variables must be included in the preventive and corrective strategy formulation. Finally, the area of on-line transient and dynamic security analysis is presented. >

Chaos in a simple power system

Chaotic behavior has been observed in computer simulations for a simple power system over a range of loading conditions. The existence of the chaos, also called a strange attractor, is confirmed by calculation of its Lyapunov exponents and by its broad-band spectrum. Some implications of this analysis are discussed. >

A comprehensive computer program package for small signal stability analysis of power systems

A package of integrated programs for small-signal stability analysis of large interconnected power systems is described. The package has extensive modeling capability and uses alternative eigenvalue calculation techniques, making it suitable for the analysis of a wide range of stability and control problems. Results of eigenvalue calculations for three power systems of differing size and complexity are presented and the accuracy, consistency and convergence of the alternative calculation methods are discussed. >

Complete bounding method for AC contingency screening

The analysis of the effects of hundreds of outages on line flows and bus voltages is required for the real-time security analysis and contingency enumeration. This increases the demands on the speed, accuracy and adaptability of the solution methods. Ideally, an ac power flow should be solved for each contingency, followed by a check for limit violations and major shifts from the initial system conditions. Such an approach is not feasible for practical systems consisting of hundreds of buses. To cope with this computational barrier, various approximate methods have been developed based on the idea that the vast majority of outages does not cause major shifts/violations. There are two classes of such methods, explicit and implicit techniques, which ease the computational burden by identifying cases with severe system limit violations. The explicit methods do not identify or solve for specific violations. Rather, they quantify the severity of each outage by a scalar index by which all the contingencies can be ranked. The explicit methods are not completely reliable since they are prone to masking errors. Specifically, a contingency with a few severe violations can be ranked equally with one with many minor violations or even worse, with one without violations. The implicit methods, though more demanding in CPU resources, permit the identification of actual violations/ major shifts and, therefore avoid masking errors. This paper describes a new contingency analysis technique which overcomes the deficiencies of existing methods. This technique has been implemented in a production-grade program designed for real-time applications.

Measurement-based dynamic load models: derivation, comparison, and validation

Accurate load modeling is essential for power system dynamic simulation. In this paper, four dynamic load models are identified based on multiple online measurement data from the Taiwan Power System. The performances in modeling real and reactive power behaviors by dynamic and selected static load models are evaluated. Parameter variation with respect to different loading conditions is analyzed. A simple and efficient method is presented to estimate a representative parameter set for different loading conditions. The cross-validation technique is applied to validate the four dynamic load models in order to obtain a better estimate of their performance. Numerical studies indicate that linear dynamic load models studied in this paper give better results than two nonlinear dynamic load models in modeling reactive power behaviors during disturbance while they are comparable in modeling real power behaviors

Evaluation of the transient energy function method for on-line dynamic security analysis

The transient energy function (TEF) method is a direct method of power system transient stability analysis. While research work on the subject continues, questions have been raised regarding potential applications of the method for online dynamic security analysis (DSA). Some of the problems are investigated, and solutions for problems arising in the use of TEF in DSA, based on tests using real utility data, are suggested. A prerelease version of a TEF program called DIRECT (version 2.9) was used in the tests. The results indicate that TEF does have a place in DSA in conjunction with other available DSA methods. >

Engineering the Future

A collaborative effort to strengthen the U.S. power and energy workforce. Some of us are old, some of us are young, and some of us refuse to acknowledge the difference. At any age, electric power and energy engineers contribute to the sustainability of life on this planet and the future growth of technology and society on all fronts. At a time when the U.S. economy is still struggling to employ more people, the power and energy sector worries about new talent to replace retiring experience. This article introduces readers to the Power and Energy Engineering Workforce Collaborative (PWC), an initiative on the part of IEEE Power & Energy Society (PES). The PWC was created to strengthen the U.S. power and energy workforce needed for the smart grid of the future and related technologies. Much of the material included here comes from the document shown in Figure 1. As these workforce issues greatly affect the United States, this work is being closely coordinated with IEEE-USA.

Power system reliability planning practices in North America

The authors present selected results from a recently completed research project for the Electric Power Research Institute. One component of the project was intended to develop and test methodologies for gathering data on how utility customers value service reliability, as measured by either the cost of outages or the willingness to pay for reliability. Another component of this project involved a survey of current and emerging reliability planning practices in the North American utility industry, especially regarding interest in value-based reliability planning. The results of the survey, including the survey design and methodology, are given. The authors briefly discuss potential applications of interruption costs in generation and composite system reliability planning. >

Evaluation of a local DC load flow screening method for branch contingency selection of overloads

The author presents a novel screening method, involving a local DC solution, for branch flow limit violations (overloads) which, when incorporated with a performance index (PI) method, can greatly enhance the selection capabilities for online as well as study purposes. The local DC screening method and PI method are compared to results obtained from a full-system DC load flow assessment of two cases: a 24-bus system and a 584-bus representation of the Mid-Continent Area Power Pool system. The results indicate that, when these two methods are combined, excellent contingency selection capabilities are produced. The philosophy for this implementation and the details needed to implement the local DC screening method are presented. >

Pre-screening of single contingencies causing network topology changes

A multilevel contingency screening method is introduced to process large sets of candidate power system contingencies. The idea is to apply a series of increasingly more accurate and time-consuming algorithms so that each higher screening level processes a reduced set of candidates. A practical implementation of the method uses a fast prescreening step whose algorithm is based upon the local network solution concept. The method is designed to process contingencies whose effects can be localized, e.g. branch outages and bus section faults. The accuracy of the new algorithm is controlled via an automatically calculated small network adequacy ratio while its reliability is enhanced by the use of different contingency severity measures. >