Analysis and control of voltage dynamics in electric power systems

This research involves the study of the voltage dynamics of power systems subject to large disturbances. The thesis is divided into two parts: analysis and control of voltage dynamics. In the analysis section, the interaction of machines dynamics with the dynamics of decentralized load voltage controls, such as ULTC (under load tap changers), is investigated. A detailed reduced-order machine dynamical model is proposed for more reliable study of voltage-related problems. The main contribution of the analytical work is in recognizing voltage problems as unacceptable operating conditions. Mathematical and operational conditions are derived for distinguishing among steady-state insecure, oscillatory, and transiently unstable voltage operating conditions as particular categories of the general voltage problem operating conditions.In the control section, nonlinear excitation controllers are proposed so that the system reactive power reserve, which is believed to be the main cause of any voltage problems, is more efficiently used. The performance of the proposed controls, subject to small and large disturbances, respectively, is compared with the conventional IEEE excitation controls which include power system stabilizers and governor dynamics as well.U of I OnlyETDs are only available to UIUC Users without author permissio