Direct Transient Stability Analysis Using Energy Functions Application to Large Power Networks

Abstract

This paper deals with the demonstration of the Transient Energy Function (TEF) method in large, realistic power networks.Documented examples of application in power system operation and associated software development for systems up to 228-generators and 1644-buses are given.An overview of the analytical and computational problems encountered in the large scale application of the TEF method is presented.Approaches used to overcome the problems are provided, and the relevant improvements and modifications to the TEF software are discussed. I. INTRODUCTIONConsiderable progress has been made in first swing power system transient stability analysis using the transient energy function method (TEF) [1]. This progress covered two main areas that are essential to the TEF's potential for use by the electric utility industry (2-5]:imore accurate accounting of the system transient energy responsible for separation of some generators from the rest, and iibetter estimation of the critical energy against which transient stability assessment is made.To date, the TEF technique has been investigated and its usefulness demonstrated, in a research environment. In these demonstrations small-to-medium size power systems have been used.Most of the applications were limited to simple disturbances with the critical clearing time being a "figure of merit" used to compare results obtained with the TEF method to those obtained by conventional means. Recently other applications of TEF have been reported upon in the literature: fast dynamic security assessment in a utility operations environment, in terms of stabilitylimited interface flows, for a radial-type system configuration [6]; stability-limited load supply capability for incorporation in the optimal power flow problem [7]; and estimation of generation-shedding requirements in the B.C. Hydro system [8]. These applications have also been used with relatively small systems. Further developments are needed for large scale power systems. 86 WM 066-5 A paper recommended and approved by the IEEE Power System Engineering Committee of the IEEE Power Engineering Society for presentation at the IEEE/PES

Determination of Transient Stability-Constrained Plant Generation Limits

“…The Transient Energy Function (TEF) method [4][5][6][7] is a candidate tool for dynamic security assessment because it provides a qualitative measure of the degree of stability or instability in the form of the transient energy margin Δν.…”

“…The solutions of equations (6) at the equilibrium points are obtained by using the Newton-Raphson method together with cubic interpolation and scaling of variables to obtain greater numerical stability [ 7 ] . The equations in the Newton's formulation are given by…”