Research On The Evaluation Model And Method Of City Power Grid Security Analysis Based On Power Supply Capability

The city power grid is the major load center of power system, it is a comprehensive power grid which contains the transmission and distribution network. Grid is the important link of connecting power supply and load, assuming the important task of electricity transmission and distribution. The safe operation of power grids is an important foundation to ensure the rapid development of the national economy, so the grid security analysis has been the focus of the study of domestic and foreign scholars. However, traditional city grid security analysis generally separates the transmission and distribution grid, and analyses the grids security separately, which has certain limitations. Therefore, this paper conducted some research on City comprehensive power grid security analysis, the main contents as follows:Firstly, this paper introduced real-time current capacity to grid security analysis, and dynamically calculated the current capacity via Morgan formulas, and utilized linear programming method to calculate real-time power supply capability. It established a real-time security evaluation system for transmission grid based on static security analysis and real-time power supply capability. The evaluation system comprehensively considered two main factors affecting grid security——network structure and operation status, and defined evaluation indexes reflecting transmission grid security states. Accordingly, this paper divided the grid actual operation state into five security classification and provided quantification standard.Then, it proposed partition management concept of grid security analysis, after decomposing the grid, it adopted "decomposition-coordination method" to realize information exchanging between the regions; it summarized the basic principles of decomposing grid and pointed out that it should make a difference between each systems and regional power grids, there is no need to require all regions to have the same security level, it should be based on the actual situation of each regions to adopt different analysis methods or evaluation criteria. It proved that decomposing grid is necessary and significant via simulation example. Finally, it proposed the concept of city comprehensive power grid security analysis and evaluaion method. Starting from maximun power supply, first step, aiming at the characteristics of transmission grid, it adopted linear programming method to analysed maximum power supply capability; second step, aiming at the flexible characteristics of distribution grid, it analysed the distribution transformer maximum power supply capability from substation supply capability and transfer capability; third step, it made a blocking analysis of high voltage distribution grid connecting transmission grid and distribution tranformer. According to the three steps,we can come to the overall security of the city comprehensive power grid. This evaluation system can effectively locate the link of limiting grid overall power supply capability, and evaluate the overall power supply capability and security classification.