Calculation of transient stability-constrained TTC based on OPF method

The maximum relative rotor angle at the end of transient period is chosen as transient stability constraints.Based on optimal control theory,an effective approach ,t o calculate the gradients of transient stability constraints with respect to all control variables, i s proposed by simultaneously computing dynamic equations and co-state equations.According to the proposed approach, t he transient stability constraints are simplified which can improve the calculating efficiency ,a nd a refined OPF-based TTC model is established.Then the SQP( Sequential Quadratic Programming) algorithm is adopted to solve the TTC problem. S ince the high-dimensional transient stability constraints are simplified dramatically ,t he TTC model is suitable for large scale power systems, meanwhile it can deal with multi-contingency effectively .A t last, an IEEE39-bus system is applied to test the proposed approach .T he results indicate that the transient stability- constrained TTC can maintain system stability ,so that it illustrates the effectiveness and efficiency of the proposed approach.