An efficient method to compute closest loadability limit in power systems

Abstract

AbstractA closest loadability limit (CLL) is considered as a most reliable index in the assessment and enhancement of voltage stability of a power system. Two kinds of methods, the iterative method and the direct N‐R method, have been proposed so far, but the computation of CLL is known to be troublesome. The former method is quite time‐consuming and its convergence is sometimes distributed due to the existence of multiple local CLLs, while the latter method is hardly useful unless a very accurate initial condition is available.This paper proposes a new method to compute a CLL, consisting of three stages of computations. The first stage is to obtain a rough initial estimate of a CLL, where multiple local CLLs can be approximated by the multiple load flow solutions. The initial estimate is refined by the second stage computation based on a method similar to the conventional iterative method. The third stage is to obtain a direct solution by mean of the N‐R method. The effectiveness of the proposed method is demonstrated using IEEE 14, 30, 57, and 118 bus test systems. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(1): 57–67, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.1171