EVALUATION OF CONTROL SEQUENCE FOR IMPROVING VOLTAGE STABILITY IN POWER-SYSTEMS

This paper addresses an investigation of control sequence for improvin g voltage stability in power systems. The controllers include transfor mers (step-up, EHV and on-load-tap-changer (OLTC)), generators, and sh unt capacitors. Dynamic simulations are performed first for a typical five-bus system covering the above mechanisms: (1) the time constants for the EHV transformer and the OLTC transformer are evaluated first; (2) the generator voltage and the step-up transformer are utilized to evaluate the performance; (3) the effectiveness of the shunt capacitor s at load buses and at EHV buses is assessed; (4) the effectiveness of lock of the OLTC is examined; and (5) finally, the system voltage evo lutions with different starting times for both EHV/OLTC taps are compa red to ensure a proper control action. Based on the above results, a s et of 12 dynamic simulations is used to explore the control sequence f or effectiveness in improving voltage stability. It is found that the best control sequence is as follows: generator voltages, shunt capacit ors at load buss, EHV transformer taps and then OLTC taps. (C) 1998 El sevier Science S.A. All rights reserved.