| In recent years, frequent blackout accidents all over the world, have attracted widely attention. On the one hand, the interconnection of power grid can improve economy and reliability of the power grid; on the other hand, it increased the complexity of the power system dynamic behavior. Partial failure is likely to spread to the entire grid, causing a cascading failure blackout. Power system blackout accidents, exposed the inherent structure vulnerability of interconnected power grid. The traditional power system analysis method based on reductionism is hard to identify weak links from the global perspective. From the perspective of complex networkstheory, structure of the system determines its function, so we can study the network structure of the power system to identify its weak link.This paper employs complex network theory to make detailed study on small-world feature identification of power grid, self-organized criticality of power system operation section, vulnerable line identification of complex power grid, and power grid efficiency assessment index integrated with Large-scale DG. The main research contents are summarized as follows:Firstly, considering the characteristics of power grid, weighted reactance simplified power grid model is established. The electrical distance index based on the equivalent impedance substitues path length index based on the shortest path, and characteristic path length index based on the equivalent impedance is proposed. A new method of small-world feature identification based on equivalent impedance for power system is presented. Numeric examples show that the presented method can reflect the small-world feature of power grid as existed methods.Secondly, taking into account some shortages of the OPA model, The SOC model only considering power system operation section is established. The SOC model assumes that power system load capacity remains unchanged over a period of time, and initial disturbance of the SOC model is to add a random load to the randomly selected load node. Numeric simulation of IEEE-39 node system shows that if power system operation section is in a self-organized criticality, the relationship between the scale of blackout accident and its cumulative probability satisfies power law.Thirdly, combined with network topological structure and power system state information, the electrical betweenness index based on power transmission distributed factors is proposed to identify the vulnerable lines in the complex power grid. The electrical betweenness index not only considers the impact of the capacity and distribution of generators and loads, but also takes into account the impact of the capacity of lines on the importance of the lines. At the same time, a new net efficieny index based on electrical distance is proposed to evualuate state of power grid after the attack. The efficiency index also considers the influence of maximum transmission capacity of each "plant-load" pair. Numeric simulations of IEEE39 and IEEE118 node system show that the lines with high electrical betweenness usually belong to long-distance in the network topology and the power flows which they bear are relatively large. To attack these lines intentionally will influence the efficiency of power grid greatly.Lastly, in the view of complex power grid integrated with a large number of distributed generations, a new net efficiency index considering the power transmission characteristics is proposed to evaluate the grid effectiveness. The efficiency index considers that DGs preferentially satisfy local load, and the impact of DGs on load decreases exponentially with increasing electrical distance. Based on the efficiency index, the line attack efficiency index and power grid operation vulnerability assessment index are established. Numeric simulations of IEEE118 node system show that DGs can improve the transmission efficiency of power grid, reduce the line attack efficiency and the operation vulnerability of power grid. |
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