This dissertation proposes a novel approach for controlled splitting of a power system into stable islands to prevent blackout. In this approach, coherent generator groups are identified by an online method, in which neither choosing the coherency degree of the generators nor executing several offline simulations for finding the proper number of coherent groups is required. A new index is introduced which its sign change indicates when the system need to be islanded. This index has no need to be compared with a predefined threshold, which must be obtained for every system based on its operating conditions. New active and reactive power flow tracing methods are then used for determining the domains of the generators that are at the same group to form the initial islands. To acquire final islanding scheme, a binary linear programming (BLP) problem is formulated and solved with the objective of minimizing the disruption of the total apparent power transferred between the initial islands. A comparison between the proposed approach and some existing algorithms for intentional islanding of 39 and 118-bus IEEE test systems shows that by implementing the proposed approach, bus voltages are more stable and island frequencies are closer to the base values.
