Evaluating bound on voltage and thermal security margins under power transfer uncertainty.

This paper deals with the evaluation of bounds on voltage and thermal security margins with respect to contingencies. A margin is the maximal pre-contingency power transfer between either a generation and a load area or two generation areas, such that specirfied contingencies do not overload lines or make the system voltage unstable. The minimum and maximum margins are computed for given intervals of variations of bus injections. Each bound is the solution of a constrained L1-norm minimization (or maximization) problem, for which specific algorithms are given. Thermal overloads are handled through linearization, while for voltage stability, fast time simulation and instability mode analysis are used. Nonlinear situations of branch overload are also considered. The method is illustrated on an 80-bus test system.