Islanding of systems of distributed generation using optimization methodology

With the introduction of distributed generation (DG) into distribution systems, island operation of DGs is regarded as a promising approach to improve system reliability. During system outages, DGs can be utilized to support part of the loads in the de-energized area and guarantee the continuity of power supply to these customers. To maximize the benefit of reliability improvement from island operation, the load amount included in the island should be maximized. Therefore the boundary of the islands should be carefully designed. In this paper, the problem of optimal island boundary design in radial distribution systems with single DG is formulated as a modified knapsack problem. The system topology constraint is considered, via a subtle formulation of the objective function. Voltage constraint is also included, by modifying the traditional manual voltage calculation method in distribution network. Moreover, the problem of optimal island boundary design with double DGs is also investigated. Based on the idea of reformulating the problem into single DG island boundary design problem, methods for system representation modification are proposed to maximize the load amount supported by double DGs. Both mathematic models are tested on the IEEE 41 bus distribution system. Simulation results have verified the effectiveness of these models, and discussions are given based on the test results.