Comparison of Sensitivity and Nonlinear Optimization Methods for Transmission Network LTCs setting

This paper compares the sensitivity method with a proposed nonlinear optimization method for setting of transmission network load tap changers (LTCs) as a preventive action for voltage instability. The aim of preventive actions is to increase voltage stability margin. In contrast to emergency actions, preventive ones implemented when the power system is stable. Thus, in calculation of a preventive action, in addition to increase stability margin, its effects on current operating point of the system must be considered. The sensitivity method is a linearized based method that uses the sensitivity of the loadability margin with respect to tap values. In the proposed optimization method, the tap values are calculated using optimal powerflow model. Two groups of variables are used in optimization problem: one group is related to base case (current operating point) and the other is related to the voltage stability boundary. By this work, the preventive actions do not cause undesirable changes in the system current variables.