Grid Topology Modelling And Cascading Failure Research Based On Complex Network Theory

With the development and application of new energy sources,the topology of power system source,grid,loads and energy storage has a new structural model.The flow of AC and DC hybrid power grids has also changed from traditional one-direction flow to double or multi-direction flow.And the generation,transmission,distribution and utilization systems are also developing toward strong,high voltage,large capacity and high tech parameters smart grids.The distribution of power flow in a complex power system is controlled on the network structure and load variation.With the user's needs increasing and scale of the power grid rapidly developing,the scope and influence of blackout is also expanding,resulting in huge economic losses.Therefore,it is difficult to solve the drawbacks of modern smart grid,safe operation and maintenance by relying on the analysis and design methods of the traditional reductionism.The complex network theory compensates for the insufficiency of reductionism and has macroscopically guiding significance towards complex power systems.Topological characteristics of the power grid are calculated and the common network features of complex power grids are extracted out.Based on the analysis of actual grid data,the grid topologies and corresponding random networks are generated.The statistical characteristics of the actual grid and random network are compared,such as the average degree,average path length and aggregation coefficient.It shows that the average path length of the grid is larger than that of the random network,and the clustering coefficient is much larger than that of the random network.That means power grids are small world networks.The grid is a sparse network and the grid topology is related to the voltage level.Because grid topology is related to the voltage level,power grid model can be established hierarchically.Grid invulnerability is simulated after component importance and measuring network performance are identified.And the power grid centrality is investigated.The removal strategies and reliability measurement for the power grid are chosen.While studying the changing trend of the connectivity under different removal method grids,the removal results based on different centrality parameters are compared.From the perspective of nodes and edges removal,the study shows that grid connectivity tends to be long tailed.Deliberate attacks have a huge impact on the operation of the power grid.The attack on the bus is more damaging to the grid than attacks on the transmission line.The hierarchical evolution power grid is modelled and analyzed.The analysis of the small-world network model and scale-free model shows that the grid has both small-world and scale-free network characteristics.The development laws of the power grid are analyzed from the time and space scales,while the features of the power grid hierarchy are extracted,leading to the proposal of the structure of hierarchically-structured power grids.Based on the above analysis,a hierarchical evolution grid model is proposed.By contrasting average degree,average path length and clustering coefficient of the grid models with those of the real grids,as well as by determining if the degree distribution curve obeys the power law distribution,the study turns out that the grid model can describe the dynamic evolution of the grid.Cascade failure models are proposed.The evolution of the power system is compared with the sandpile model in order to give constraints and driving forces for the development of the power grid.The OPA model for the growth evolution model and the OPA model for the evolved structural are proposed.The self-organized criticality of the two models is validated and the research shows that the failure scale is inversely proportional to the probability.