WAMS Based Power Systerm Voltage Stability Assessment

Energy resources and needs distribution is reverse in China. Therefore, grid interconnection has great significance in energy consumption and economic benefit. It also brings great challenges to security and stability of power system. Electrical network of major cities in Eastern China load centers has been receiving end system with high electricity proportion from outside grid. Voltage instability problems would become a major threaten to this power grid. With the development of phasor measurement unit and wide-area measurement system, more and more attention is attracted on on-line voltage stability assessment using wide area synchronous data.Based on summary and commentary of existing voltage stability theory, static analysis method is still considered as an effective measure to assess voltage stability on-line. Effect of dynamic elements should be involved to make the method more practical. This article proposed an on-line voltage stability assessment method based on WAMS.Thevenin equivalent impedance is selected as a stability criterion in this article. It is proven that this criterion has no relevance with load model and power factor. The quantitative relation between this criterion and power margin is analyzed.This thesis proposed an improved recursive least square method with forgetting factors to calculate Thevenin equivalent parameters. This method has good tracking performance to accommodate system changing. A reactive power margin index is also proposed to assess dynamic elements’influence appropriately.The aforementioned criterion is intergrated with the method based on the sensitivity of the minimum singular value for better performance. The intergrated assessment project can determine both key factors of system voltage stability and accurate power margin of certain areas.Finally, several test systems and full dynamic simulation program verify the effectiveness of the aforementioned algorithm and the intergrated assessment project.