Study Of Identification And Evaluation Of Power Grid Key Parts And Key Transmission Sections

With the rapid economic development and its ever deepening reliance on the power system, modern power system has been further developed in this century, while the scale of power system is ever expanding, the interconnection intensifying, and the modality and operation mechanism are constantly evolving and gaining complexity. In recent years, blackouts have occurred around the world, revealing the inherent hazard of modern power system that a local fault may trigger cascading failures, and may eventually result in a blackout. Possible solution towards this problem lies in accurate identification and evaluation of key parts and key transmission sections that undertake critical power transmission tasks within power grid. By means of reconstruction planning, fault monitoring and emergency dispatching according to the identification and evaluation results, it is possible to improve the security and stability margin of the power grid and block the cascading failures, thus avoiding the risk of a potential blackout.In this thesis, by introducing the concepts of power transmission path, weighted path transmission distance and weighted path transmission capacity into conventional complex network theory, the node degree and betweenness index are modified to represent more realistic physical properties of power grid, and are integrated to establish a key parts identification index system. This proposed index system is capable of assessing the accessibility and adequacy of power transmission, and evaluating the comprehensive criticality of nodes and branches in power transmission in terms of both grid topology structure and system operation status.Based on the identification of key branch, key branches with relatively low capacity margin are chosen as the dominant branch, and a key transmission section identification algorithm is proposed based on electrical relationship discrimination. The algorithm uses the power transmission path analysis and the line outage distribution factor(LODF) to determine the parallel relationship and the electrical relationship between different branches, effectively identify the key transmission section that shares a close electrical relationship with the feeble key branch chosen as the dominant branch.On account of the transmission section identification results, three different transmission section evaluation algorithms are proposed in this thesis, based on the transmission capacity ratio, the average comprehensive criticality and the grid performance variation respectively. These proposed algorithms are capable of quantifying the significance of transmission sections from different angles of stability margin, power transmission criticality, as well as outage impact to the grid. The evaluation results can be used as references in transmission section reconstruction planning, security monitoring, protection configuration and other important decision-making.Simulations on both IEEE typical test systems and a planning provincial power grid are conducted, and the identification and evaluation results are further analyzed and compared with similar studies, demonstrating both feasibility and effectiveness of the proposed index system and the proposed algorithms.