Study on power system out-of-step criterion based on WAMS

In this paper, a novel integrated criterion to identify the critical cluster for power system out-of-step control, which includes both history and future information of WAMS measured rotor angle curves. And a composite criterion is proposed to judge whether the DSP (dynamic saddle point) on electromagnetic output power-rotor angle curve plane is the true DSP which results in losing transient stability. Finally, the flowchart description of the proposed out-of-step criterions is given. The simulation results of WSCC and the `North China-Central China-East China' UHV grid demonstrate that the proposed method works well. It can identify the instability of power system even when the characteristic of instability is not obvious, so it is helpful to realize the fast islanding in large interconnected power systems.