A Novel Method to Estimate the System Damping After Generator Tripping

Generator tripping strategies are generally decided by offline transient stability analysis. However, traditional methods can hardly ensure dynamic stability after GT. Simulation tests show that GT strategies change the topology and the state variables of a power system, which may weaken the system damping after GT. In order to estimate the system damping, this paper proposes a time-varying linearized model under unsteady states based on the virtual equilibrium point (VEP) theory. Then, the changes in dynamic characteristics caused by GT can be represented by the eigenvalues at VEPs before and after GT. An inertia equivalence system is mathematically formulated to analyze the effects of generator inertia, damping ratio, and controllers. Two indices are designed to estimate the system damping changes. Based on the indices, a framework is proposed to improve the current GT strategy decision-making system. The sensitivity analysis and the fault scanning verify the effectiveness and robustness of the proposed method and indices.