Active Distribution Network Reliability Assessment

The large-scale integration and application of distributed generation will bring extensive influence to the traditional distribution network. The emergence of active distribution network can solve the accessing problem of large amount of distributed generation, and active distribution network can make better use of distributed generation. In active distribution network, the access of distributed generation makes distribution system evolve into a more complex network with multi-power-sources and multi-customers. What’s more, distributed generation can run in island when the system breaks down, so reliability evaluation theory and method of active distribution network is different from traditional distribution network. In order to better evaluate the active distribution network, the reliability evaluation model and method of distribution network need to be studied.Firstly, the concept and characteristics of active distribution network are detailed in the paper. The impact of distributed generation for distribution system is summarized, and three kinds of typical development pattern for active distribution network are proposed. Secondly, island partition of active distribution network is studied, the island running standard and typical island operation modes are introduced, while the principles and constraints of islanding are analyzed. The distribution network model simplified to a root tree model, island partition model is established with the goal of maximizing the effective load, improved Prim algorithm is used for the minimum spanning tree searching and the scope of the search is reduced through the division of power circle, which makes the islanding far more efficient and reasonable. Thirdly, on the basis of traditional power distribution system reliability index, according to the characteristics of to a large amount of distributed generation accessing to active distribution network, the calculation method of relevant indicators are modified, and two new reliability indexes reflecting the contribution of distributed generation to the reliability improvement of the system are put forward. Based on the traditional distribution network reliability evaluation method and component reliability model, the power characteristics model and reliability model of distributed generation are analyzed, and the frequency and duration method is taken to solve the failure rate of the islands. In terms of active distribution network reliability analysis, the reliability evaluation model and method of typical connection mode with distributed generation of are studied on the basis of the traditional reliability evaluation. Finally, the island partition model and algorithm, the reliability evaluation model and method are applied to an active distribution network case, relevant conclusions are obtained.