Optimal hybrid control of transient stability. Part one: For cases with a unique unstable mode

This two-part paper develops a global optimization framework for transient stability control to coordinate preventive actions and emergency actions. Based on stability margin and unstable mode provided by EEAC, the unstable contingencies could be classified into subsets according to their unstable modes. In the first part, an algorithm is proposed for a subset of contingencies with a same unstable mode. Instead of iterations between discrete emergency actions and continuous preventive actions, the algorithm straightforwardly searches the globally optimal solution. The procedure includes assessing a set of insufficient emergency schemes identified by EEAC; calculating the related preventive actions needed for stabilizing the system; selecting the scheme with the minimum global costs among the all. Simulations on a Chinese power system highlight its excellent performance. The good results are explained by analogizing settlements for 0-1 knapsack problems using multi-points greedy algorithm.