A Sequential Approach for Small Signal Stability Enhancement with Optimizing Generation Cost

A small signal stability enhancement method is proposed based on optimal power flow model, where small signal stability (SSS) is considered as additional constraint. For handling the discontinuity and high nonlinearity of SSS constraint, a sequential approach is proposed to decompose the original optimization problem into a sequence of sub-problems. For every sub-problem, SSS constraint (i.e., critical eigenvalues) is linearized locally within bounded region. To ensure the effectiveness of eigenvalue sensitivity, a trust region strategy is used for dynamically updating the region size in solving sub-problem sequence. For preventing constrained eigenvalues from varying between critical and uncritical modes in the solving process, an active set strategy is adopted to construct the constraint set and control the solving process. A set of candidate operating points, with different generation cost and minimum damping ratio, is extracted from solution of the sub-problem sequence, which allows to make trade-off between economic efficiency and stability level for system operation. Three test systems are used to validate the effectiveness and applicability of the proposed method.