Efficient look-ahead load margin and voltage profiles contingency analysis using the tangent vector index method

Look-ahead contingency analysis involves how to predict the near-term load margin and voltage profiles with respect to voltage collapse points of a large number of post-outage systems. In this paper, an efficient curve-fitting-based algorithm is developed. Instead of approximating the load margin as a quadratic function of voltage profiles with three unknown coefficients near the collapse point, we reformulate it as a quadratic function of voltage tangent vector profiles with only two unknown coefficients. Only two consecutive voltage tangent vector profiles are needed in the proposed formulation which involves less computational cost in comparisons with those required in existing methods. A numerical stable method to calculate the tangent vector is proposed first. Based on the load margin approximations predicted by the tangent vector, a general framework for look-ahead contingency selection, evaluation, and ranking is developed. We evaluate this method on several power systems. Simulation results demonstrate the efficiency and the accuracy of the proposed method