Correction Method of Sensitivity of Load Margin Respect to Branch Parameters Based on Thevenin Equivalent of Key Ports

Branch contingency ranking and screening methods based on the linear sensitivity of load margin respect to branch parameters are widely used in the power system security and stability assessment because of the rapid computation speed. However, due to the nonlinear nature of power system, linear estimate value may be erroneous, especially for some serious contingencies. In this paper, Thevenin equivalent of key ports and its fast modification as branch parameter varies is used to observe how the state variable impacted by the change of branch parameter. And then the relationship between the state variables and branch parameter is fitted by a set of quadratic functions. With the nonlinear information between the state variable and branch parameter, traditional linear sensitivity is corrected to get a more accurate estimate. As the branch parameter varies, the correction of Thevenin equivalent of key ports only needs a small amount of additional computation, and the calculation burden does not increase significantly with larger system, so this approach remains high computational efficiency. An IEEE 14-bus case is used to validate the proposed method in this paper.