Look-ahead Q-constrained load margin for large-scale power systems

Fast load margin estimation schemes have been applied to functions of contingency screening and ranking for on-line voltage security assessments. However, the existing load margin estimation schemes do not take reactive power limit into considerations. In this paper, load margins estimation schemes are extended to take Q-limit into considerations, the robustness, speed of look-ahead method is testified when generation reactive power limits are considered. The reactive power margin of generation is used to predict whether the bifurcation type is saddle node bifurcation or structure-induced bifurcation. The numerical studies show that the computation time can be significantly decreased with look-ahead step length control method.