Direct Critical Clearing Time Calculation Based on Interior Point Nonlinear Programming

It is very important to assess transient stability and critical clearing time in power system. Traditional trial and error heuristic methods are costly and inaccuracy. Using interpolation formula or curve fitting method and proposing a general criterion for transient stability judgment, a nonlinear programming module that can calculate CCT directly is presented. With the technique of equivalent transformation to convert stability constrains, an interior point algorithm with approximate Newton direction for solving proposed model is derived, too. Based on time domain emulating and numerical calculation completely, they suit for any generator and load modules very well. Simulation on 39-bus (10 machines) and 145-bus (50 machines) systems demonstrates the characteristic mentioned above.