An Inproved Power Flow for a Ill-Conditioned Power System with FACTS Devices

Abstract

This paper addresses the issue of the computation techniques for assessing the steady state power flows controlled by Flexible AC transmission Systems (FACTS), which contain variable series compensators (VSC), phase shifters (PS), interphase power controllers (IPC), unified power flow controllers (UPFC). An improved Newton-Raphson load flow program has been developed based on an analysis of convergence characteristic of the conventional method. It is shown that the conventional method tends to suffer from ill-conditioning problem, resulting in the shrink of the convergence region. Based on examinations of the condition number of the Jacobian, a penalty function method is adopted in order to avoid the ill-conditioning problem and to guarantee a successful convergence. Although the computational burden is increased about twice to three times, the proposed method much extends the region of convergence. The effectiveness of the proposed method is demonstrated through numerical examinations using IEEE 57 and 118 bus systems.