The Model And Method For Obtaining Critical Clearing Time For Transient Stability Analysis Based On Critical Trajectory

Due to the expansion of the grid size, the emergence of new technologies and the desire to use large amounts of renewable energy, the structure, control system and operation of power grid have become more and more sophisticated. Power system operation stability analysis, especially its transient stability analy-sis, obtaining critical clearing time(CCT) has become increasingly important.Main topics of this thesis is the research of calculating the critical clearing time based on critical trajectory. An improved formulation based on critical locus for computing CCT has been proposed while analyzing the method suggested by Japanese scholars Yorino.The new model describes a post-fault locus which connects the fault-on trajectory and the critical point. And it uses a new critical stability criterion. Solving the model gets a post-fault trajectory which meets the critical stable state and it’s called critical trajectory also. The fault clearing time corresponds to the initial point of critical trajectory is the critical clearing time. The principle and structure of new model are very simple. And the model is able to solve by using modern interior point method.In the dissertation, expected faults are set on typical one-machine system,3-machine9-bus system,10-machine39-bus system and IEEE-118system ahead of calculating the CCT by which using traditional time domain simulation method and critical trajectory method respectively. Finally, simulation results are compared and analyzed to verify the validity of the new model.The critical trajectory method proposed by this thesis provides a new idea and approach to find CCT. It plays a reference role for the enrichment and development of theory and solution of transient stability analysis.