Determination of available transfer capability by means of Ralston's method incorporating cubic-spline interpolation technique

Abstract

This paper presents a fast and accurate method to determine the power transfer so-called the available transfer capability (ATC). The methodology utilizes the cubic-spline interpolation technique that is incorporated into the Ralston's method in order to provide fast and accurate assessment of ATC. The Ralston's method is used to predict the two trajectory points of voltage magnitude (U), power flow (S), and maximum generator rotor angle difference (Δδ). Then, the cubic-spline interpolation technique is used to accurately trace the P-U, P-S, or P-Δδ curves between two points of trajectory. The P-U, P-S, and P-Δδ curves represent as the variations of voltage magnitude, power flow and maximum generator rotor angle difference due to the increase of power transfer or ATC. The actual value of ATC is then determined when either the voltage magnitude limit, power flow limit or generator rotor angle difference limit intersects the curve. The effectiveness of the proposed method is verified by referring to the results of ATC for a case study of 2737-Polish system and 39-New England bus system. The proposed method gives a satisfactorily accurate and fast computation of ATC as compared to recursive AC power flow method. Copyright © 2010 John Wiley & Sons, Ltd.