A strategy for frequency stability of islanded power systems

Power system islanding is the last defense in protecting power grids from wide-area blackout. This paper introduces a novel approach for separation of the entire power system into several stable islands. The proposed method combines both the dynamic and static characteristics of interconnected power network and determines the proper splitting schemes. The presented algorithm searches for proper islanding strategy in the boundary of primary determined coherent-machines and finds the proper splitting points by transferring some of the buses in one island to another island such that total load shedding is minimized. The method reduces the huge initial search space of islanding strategy considering dynamic characteristics of integrated power system and reduction of search space to only boundary network. A spanning tree based on breath first search algorithm is used to find all possible combination of transferred buses. The speed of the proposed algorithm is remarkably high and can be applied for islanding the power system in real-time. The proposed algorithm is applied to NPCC 68BUS test system. Results show the effectiveness and capability of the algorithm to determine fast and accurate proper islanding strategy. Time domain simulation of the islanding strategies confirms that all the islands which are determined by the method are stable.