Analytical Calculation Method for Power Supply Reliability of Distribution Systems With Multiple Tie Lines

The existing methods for distribution system reliability assessment mainly adopt the multiple iteration calculation modes of traversal search of failure scenarios one by one to get the failure effect area and degree. However, these methods are time-consuming and low-efficiency, due to the repeated searches and the complexity of failure effect analysis. Meanwhile, the reliability assessment results only representing the system's average level always cannot provide weak link information for the operators. In this article, an analytical calculation method for distribution system reliability index based on the improved failure effect incidence matrix (FEIM) is proposed. First, an incidence matrix-based modeling of the complete topological association of source-network-load of the distribution system is conducted, including node-branch relationships, segment switch's locations, and fuse locations, which are closely related to reliability analysis. And the rules for calculating the source-load power supply association matrix are also provided. Next, an improved FEIM model is established to analytically express the correlation between failure components and affected loads. Finally, the distribution system reliability index analytical calculation method based on the improved FEIM is presented. The proposed method is validated using the IEEE RBTS bus-6 case and a modified 96-node case. The results demonstrate that the method can significantly improve the computation efficiency while ensuring the accuracy of the results. Additionally, it can conveniently provide more efficient information on system bottlenecks and weak points for the reliability improvement of distribution systems.