Low voltage power flow solutions and their role in exit time based security measures for voltage collapse

The authors examine the nature of the low-voltage power flow solution in power system models that involve voltage-magnitude-dependent reactive loads. The role of these solutions in exit-time-based measures of security with respect to voltage collapse is considered, and the special role of a 'lowest energy' solution is highlighted. Heuristics for initializing the Newton-Raphson (N-R) iteration for finding this low voltage solution are proposed and illustrated in sample networks. The convergence properties of the N-R algorithm are illustrated by examining the region of attraction associated with various low-voltage power flow solution with respect to the N-R iteration in sample networks.