Simplifications for Area Security Analysis : A New Look at Equivalence

Hernando Duran and N.V. Arvanitidis, PAS 91, No.2, March/April 1972, pp 670-679

Analysis of an area within a large interconnected power system under various system configurations and load conditions is often needed in off- and on-line applications. Equivalence isolates the study area and represent the rest of the system by a simplified equivalent model. A new and more comprehensive approach to the equivalence problem is presented which emphasize the design and operational aspect rather than conventional network reduction, and which is based on meeting application specified operational requirements. Result from a test case demonstrate the validity and accuracy of the method as applied to outage analysis load flow studies.

Power System Model Reduction - A Canonical Representation

Abstracts : J.B. Woodward and F.C. Schwepe, PAS 93 No.31 No.1 January/February 1974 P.6

Many Studies of system frequency response to load changes or generation losses use average frequency and energy balance concepts. This paper discusses an approximate technique for reducing the number of differential equations required to represent a power system for such a study. The average system frequency model is briefly summarized and canonical representation technique is refunded and greatly extended. The result is an average system frequency model (including nonlinear valve limit effects) whose number of state (differential equation) is independent of the number of the machines. An operational, conversational computer program is discussed and a few example of the accuracy achieved with the canonical representation technique are presented. The paper is concludes with a brief discussion of the useful properties and limitations of the canonical representation of the average frequency.

Sparsity-Oriented Network Reduction

Abstract: W.F. Tinney, W.L. Powel N.M Peterson, PAS 93 No.1, January/February 1974, p.6

The conventional approach to network reduction in which all non essential nodes are limited usually results in an equivalent that is so densely interconnected that sparse matrix methods cannot be effectively used on it. In order to obtain an equivalent that is suitable for sparsity exploitation, it is usually necessary to retain certain non essential node that would normally be eliminated. This paper identifies the main factors affecting sparsity of network equivalents, describes a practical algorithm for determining the non essential nodes that should be retained and makes suggestions for better algorithms. This paper is of importance in any network application in which sparse matrix method are used.