多频振荡下失步解列判据的适用性分析

Applicability Analysis of Out-of-step Splitting Criteria Under Multi-frequency Oscillation

目前国内使用的失步解列装置应用的失步判据都是在两机失稳的情况下推导得出,在多频失步振荡情况下是否仍然适用值得探讨。以三机等值系统为模型,推导出各电气量的表达式,得出在多频振荡时失步中心在不同线路之间以及同一线路的不同位置之间发生迁移,而且各机组越不同调,失步中心可能在更多的线路之间发生迁移。此外,对基于Ucosφ轨迹、测量阻抗轨迹以及视在阻抗角变化规律的三种失步解列判据在多频振荡情况下的适用性进行分析研究,可知三种失步判据都存在误判的风险,建议将基于视在阻抗角判据与线路两端相角差判据配合使用,提高失步解列装置的正确性。

The criteria for out-of-step separation equipment in current domestic engineering fields are acquired from the out-oL step two machine equivalent power system. Its applicability under multi-frequency oscillation is yet to be found out. Expressions of electrical quantities are inferred based on a three-machine equivalent system. And it is found that the out-of step center would migrate between different transmission lines and different positions even on one and the same transmission line. In addition, the more distinct the different modulations are, the more transmission lines will there be for the out-of-step center to migrate in between. Besides, the three out-of-step splitting criteria based on Ucos φ characteristic, the measured impedance locus and the apparent impedance angle can hardly adapt to the multi frequency oscillation scenario. It is advised that the two splitting criteria, apparent impedance angle and phase angle difference cooperate with each other to improve the correctness of out-of-step separation equipment.