Identification Of Key Links In Power Grid Considering Topological Structure And Operating State

With the continuous expansion of the scale of the power grid and the continuous increase of the demand for power,the trend of more complicated network architecture has been unavoidable,and the security of the power grid is facing a more severe test.Paying close attention to monitoring and protecting of the key links that may cause serious accidents in the power grid could discover potential risks of the power grid in time and carry out preventive control.Therefore,using reasonable methods to identify the key links of the power grid is of certain reference significance for preventing major power outages and improving the safety of the power grid.Based on learning and drawing on existing research results,this paper uses complex network theory,entropy theory,energy function,etc.to identify key nodes and key lines of the power grid from the aspects of topology and operation status.The main research contents of the paper are as follows:(1)Construct an improved weighted directed power grid complex network model.Based on the weighted directed power grid,the concepts of power transmission path,weighted power transmission distance and path transmission capacity are proposed to supplement and improve the weighted directed power grid.The model considers the electrical characteristics of the power grid and the constraints of line safety,so it is more closely adapted to the actual conditions of the power grid.The improvement of traditional statistical indicators and the establishment of improved weighted directed statistical indicators which are suitable for the new model lay the foundation for studying the complex network characteristics of the power grid and identifying key links in the power grid.The analysis of the calculation example shows that the model can better reflect the topology structure of the power grid,and the calculated improved weighted directional statistical indicators are more in line with the actual situation of the power grid.(2)A key node identification method based on the improved technique for order preference by similarity to ideal solution is proposed.Firstly,a hierarchical key node identification index system is constructed considering the power grid topology,the impact of node getting out operation,and the anti-disturbance ability of the node.Secondly,the Delphi method and the anti-entropy method are used to determine the weights from the subjective and objective aspects.The quadratic programming method combines the subjective and objective weights to obtain the optimal comprehensive weights.Finally,the relative entropy and the gray correlation degree that introduces the dynamic resolution coefficient are used to improve the traditional ideal.Obtain key nodes by the criticality evaluation and ranking of nodes.Simulation results show that the proposed method can effectively identify key nodes of the power grid,and multiindex evaluation can overcome the one-sidedness of single-index evaluation.(3)Consider the probability and the consequences of line breaking,and identify the key lines of the power grid based on the fuzzy comprehensive evaluation method.Firstly,the impact vulnerability index is defined.The probability of line breakage is expressed in three aspects: random load fluctuation,other line disconnection having an impact on target line and the line’s own anti-impact performance.Secondly,the consequences of line disconnection are evaluated from two aspects: state and structure.Drawing on the decomposable characteristics of Theil entropy theory,considering different nodes and line partitions,construct weighted power flow fluctuation theil entropy and voltage fluctuation theil entropy indicators,combined with degree Gini coefficient and the edge toughness.Use the four indicators and the analytic hierarchy process-improving entropy weight fuzzy comprehensive evaluation method to obtain the comprehensive disconnection consequence,and the critical lines are identified together with the disconnection probability.Analysis of examples shows that this method overcomes the shortcomings of the identification method that only considers the consequences of line disconnection and can more accurately identify key lines,having certain feasibility and practicability.