A transient voltage stability index based on critical equivalent impedance

Criteria and indices of transient voltage stability have attracted much attention recent years. It is a difficult problem since dynamics of load components are involved, such as induction motors and HVDC converters. A transient voltage stability index based on critical equivalent impedance and time-domain simulation is proposed in this paper. Firstly, two different static voltage stability indices based on Thevenin equivalence are introduced, and the second one provides a new idea to transient voltage stability analysis. Secondly, a transient voltage stability index is proposed, and an equivalent system is built up after a large disturbance, with a time-variant Thevenin equivalent circuit and a dynamic load. Thirdly, the algorithm process and flowchart are put forward. Fourthly, online applications of the proposed index are discussed. Finally, the proposed index and algorithm are tested on two test systems and a practical power system. Simulation results demonstrate its effectiveness and feasibility.