Convergence measures for contingency screening in continuation power flow

In continuation power flow (CPF), the power flow equations are reformulated to make the problem well-conditioned at all possible loading conditions including the voltage collapse point. Due to this, CPF has become the computational engine for voltage stability analysis (VSA) studies. In studies for calculating the available transfer capability (ATC) to transfer power across different regions of the power system, VSA is used to analyze base case conditions as well as contingency cases. To improve the computational performance, contingency screening has been proposed by various authors. Due to the nonlinear nature of the voltage stability problem, the performance of a screening method depends on the load level at which the screening is performed. The load level considered needs to be sufficiently close enough to the collapse point that it provides correct ranking as well as far away to ensure solvability of contingency cases. This paper addresses the issue of defining convergence measures that would help in selecting a load level in the base case curve for performing contingency screening.