IEEE Transactions on Power Systems

A comprehensive framework for probabilistic steady-state and dynamic security assessment is presented. The time to insecurity is used as the measure of system security. Its probability distribution is obtained from the solution of a linear vector differential equation having coefficients that are expressed in terms of steady-state and dynamic security regions. An illustrative example for a simple ... View full abstract»

A conceptual framework for computer-aided monitoring and assessment during system restoration using analytical tools is proposed. The basic structure is similar to one for security monitoring and assessment (ibid., vol.3, no.1, p.1-9, 1988). State estimation and the related functions, such as observability analysis, bad-data identification and external network modeling which are used in security a... View full abstract»

The concept of integral manifolds is used to create systematically improved reduced-order models of synchronous machines. The approach is illustrated through a detailed example of a single machine connected to an infinite bus. The example shows the advantages of the manifold approach and clarifies several issues regarding such models. The basic objective of the method is to include the effects of ... View full abstract»

A simple, reliable, and effective approach to the solution of hydrothermal dispatch problems is presented. It is based on computing the LU factors corresponding to a permutation of the rows of the Jacobian matrix (Lagrange matrix) at each iteration. The economic operation of hydrothermal systems is further reformulated as a linearly constrained least-squares problem, leading to another iterative t... View full abstract»

The problem of system collapse or blackout characterized by a local severe voltage depression is generally believed to be associated with inadequate VAR support at key busses. The authors discuss techniques for improving the system security with respect to this index. The effect of adding capacitors are examined. They also present a continuation technique that redistributes the system generation t... View full abstract»

Simulation and control studies are carried out on a power system that is subjected to a cyclic load. The simulation method, which is based on singular perturbations, produces accurate results with reduced computation time compared to existing techniques such as the Van Ness method. A suboptimal controller is designed on the basis of slow and fast modes. Its performance is comparable to that of an ... View full abstract»

A very efficient contingency analysis method for detecting branch megawatt flow violation is presented. The efficiency stems from the use of a bounding criterion that drastically reduces the number of branch-flow computations and limits checking, and the use of state-of-the-art compensation and sparse matrix/vector methods. The method requires no offline setup, is highly efficient, and can handle ... View full abstract»

A technique for deriving dynamic equivalents is developed that combines the advantages of modal and coherency analysis. The electromechanical mode shapes are examined to find all the possible coherent groupings of machines in a given system. The results are displayed as a tree structure in which the whole interconnected power system forms the root of the tree and the various subdivisions of the sy... View full abstract»

An efficient comprehensive methodology is described that allows interactive forecasting of distribution-substation load growth and load sharing, with application to the determination of an economically feasible timing schedule for adding substation capacity. A BASIC-language implementation illustrating some of its capabilities is discussed. Load growth is expressed by a Gompertz model using parame... View full abstract»

A method is presented for estimating the magnitude of the demand-side load-control resource of an electric power system so it can be factored into the daily plan of the operating engineers, who are responsible for meeting the needs of utility customers. The critical requirements for developing a demand-reduction-estimating algorithm in order that the demand-control resources can be known are prese... View full abstract»

Improvements made to a relational database management system (DBMS) developed for real-time energy management and control systems for electric utilities are described. The focus is on the software performance improvement features and the dual database concept for coordinated updates. The discussion covers task structuring, buffer usage, active restructuring, and presolving of access routes. Some o... View full abstract»

Three node-ordering algorithms that enhance sparse vector methods without losing sparse matrix method efficiency are presented. The performance of the algorithms is compared with that of the minimum-degree algorithm for eight test systems up to 661 nodes. For the factorization of a sparse matrix into U/sup t/U, the new algorithms give a similar or even better sparsity for U, while clearly improvin... View full abstract»

A theoretical approach is presented for calculating the error involved in the solution of stochastic production costing problems using the method of cumulants. It is proposed to use this calculated error in an algorithm for obtaining an improved stochastic approximation of the equivalent-load-duration curve. The results show that of the three series that can be used for stochastic approximation, n... View full abstract»

The application of a stabilizer to a power system with a pumped-storage plant is investigated. Eigenvalue-eigenvector analysis and time-domain transient stability simulation are used to identify the optimum stabilizer parameters, and are verified by field test results. It is found that for the system considered, the pumped-storage plant is not necessarily the best location for the stabilizer appli... View full abstract»

The ability of a dual-rate adaptive stabilizer to damp multimode oscillations in a power system is investigated. The controller adjusts its parameters to track the dominant frequency of oscillation and damps different modes one by one according to their dominance. The results show that adaptive and conventional stabilizers working on different units within a system can operate cooperatively and mu... View full abstract»

While it is pointed out that probabilistic methods for the reliability assessment of composite generation and bulk transmission in electric power systems are still under development, an overview is given of the purposes and uses of power systems reliability studies. Probabilistic indices and reliability criteria are discussed. The features of a comprehensive reliability program to compute these in... View full abstract»

Five short reports are presented that direct attention to problem areas being worked on by various Working Groups and Task Forces of the System Operations Subcommittee. Two reports deal with problems associated with the replacement of energy management systems (EMS) and predicting resource requirements. One report describes the problem of making EMS alarming effective. Another focuses on problems ... View full abstract»

Results are presented for reduced-order models of power systems as large as 254 generators and 2500 buses, using the modal-coherency method of model reduction. Extension of order estimation, based on balanced realizations, to larger systems is discussed. An alternative order-estimation approach based on the intergenerator coherency ranking table is introduced and compared to the balanced realizati... View full abstract»

A collection of short papers presented at a panel session held at the 1986 Winter Meeting of the IEEE Power Engineering Society is presented. The experiences of five electric utilities in North America and Europe in the area of instrumentation for monitoring power-system dynamic performance during major disturbances are discussed. The focus is on the requirements of the individual utilities, and i... View full abstract»

The requirements of composite generation and transmission system reliability evaluation methods for use in power system planning are described. The focus of this report, which is based on inputs obtained for utility system planners, is on the philosophy and purpose of composite system reliability evaluation rather than on the modeling details.<> View full abstract»

Consideration is given to the impact that terminal-station failure events have on the contingencies of connected lines and generators that should be included in the reliability evaluation of a composite system. Algorithms are described that simulate various failure modes of station components, deduce the resulting contingencies and their reliability indices, group together identical contingencies,... View full abstract»

A general and efficient method is presented for transient simulation of HVDC converters. The method utilizes a novel algorithm that is based on network topological concepts and provides an efficient solution to the problem of modeling the inherently nonlinear characteristics and time-varying topology of static power converters caused by the switching action of the thyristor valves. The application... View full abstract»

For pt.I see ibid., vol.3, no.1, p.166-72 (1988). A flexible and computationally efficient method is presented for transient simulation of integrated AC/DC systems. The method is based on network topological concepts and utilizes the results presented in pt.I. A modular modeling approach is used that facilitates the application of the method to any AC/DC system configuration.<> View full abstract»

A novel method is presented for preparing load models for power flow and stability studies. The LOADSYN load model synthesis software package transforms data on load class mix, composition, and characteristics into the form required for commonly used flow and transient stability simulation programs. Typical default data have been developed for load composition and characteristics. The load-modelin... View full abstract»

A method for transient stability analysis of multimachine power systems has been investigated. This method is based on the comparison of the potential energy transfer that takes place between a critical machine and its cutset with the fault kinetic energy produced during the fault. Three fault cases on the reduced Iowa system have been simulated. The results show that the total energy absorbed by ... View full abstract»