Research On Topological Structure Planning Of Multi-microgrid Based On Ring Network

Energy supply not only involves national security,but is also an important foundation for maintaining sustainable human development.In order to cope with the energy crisis that may be faced,renewable energy has gradually received extensive attention from the world and has become one of my country’s key development strategies.As a powerful means to solve the impact of distributed power generation on the power system,microgrid has broad application prospects.However,as the penetration rate of distributed power generation in the distribution network is getting higher and higher,the conventional single-source radial structure is transformed into a complex system containing multiple power sources,and its operation mode is similar to the power flow control and ring network structure.If the overall planning of a distribution network containing a large number of distributed power generation as a large microgrid is complicated and difficult to achieve,how to plan a scientific and reasonable microgrid topology becomes an important issue for grid planners task.In order to meet the challenges of microgrid planning caused by the increase in distributed power generation,the microgrid ring network structure was studied,and a multi-microgrid based on the ring network was proposed based on the known location,capacity and quantity of distributed power generation.The main content of the topology planning method is as follows:First,analyze the impact of the continuous increase in distributed generation penetration rate on microgrid planning,summarize the advantages of the microgrid ring network structure,and focus on the shortcomings of a single operating microgrid,analyze and analyze the typical structure of multiple microgrids.The principles to be followed in the planning of multiple microgrids are formulated,and the knowledge of graph theory applied in the planning of the microgrid ring network structure is introduced.Second,in view of the limitations of using a single distributed power generation to plan the microgrid ring network structure,a node allocation method based on weighted distance is used to make a preliminary judgment on whether a single distributed power generation can build a ring network microgrid.Define equivalent indicators based on the impact range of distributed power generation on the load and the correlation between distributed power generation during the construction of the ring network,and combine the equivalent values of distributed power generation that meet the equivalent requirements,and plan the microgrid ring for each distributed power generation.The network structure lays the foundation.Finally,on the basis of equivalence merging of distributed power generation,a multi-microgrid ring network structure planning method based on graph theory is proposed,and the mathematical models of three stages of coarsening,partitioning,and refinement in graph theory are established respectively,and the system is The nodes are allocated to the preliminary ring network.Under the premise of ensuring the balance of distributed power generation and load supply and demand in the planned ring network,the necessary nodes and the proportion of points outside the ring for the construction of the ring network are introduced into the model to avoid open-loop and uninterrupted The emergence of a reasonable ring network structure.Establish the integer linear programming stage model to design the nodes in the preliminary ring network,realize the selection of the given lines,and obtain the multi-microgrid ring network topology.According to the structural characteristics of the ring network,indicators for the rationality,power supply balance and robustness of the microgrid ring network are proposed for evaluation.The simulation results show that the proposed planning method can effectively plan multiple ring-net microgrids with reasonable structure and balanced supply and demand when there are more distributed power generation.