Research On Improving The Resilience Of Urban Distribution Network

Urban distribution network is located at the end of the power supply network,directly facing the vast number of power customers.It is the key link in the power supply chain to connect power grid enterprises and end users.It is also an important carrier to ensure the safety of urban energy supply,achieve economic benefits,and highlight the social responsibility and high-quality service level of power grid enterprises.With the increasing prosperity of the economy and the rapid improvement of living standards,the development of eletric distribution network is also changing with each passing day,its scale is gradually expanding,and the mode of power supply is becoming more and more complex.In recent years,the frequent blackouts in the world have also attracted great attention from the government,experts and scholars.The importance of electric distribution network has also been affirmed by power supply enterprises.Extreme weather or major accidents directly destroy the electric distribution network,and on this basis,it is particularly important to improve the resilience of the distribution network.The influencing factors of resilience can be traced back to all aspects of urban distribution networks.Targeted measures can be used to improve the toughness of the distribution network under different operating conditions.This paper takes the urban distribution network with voltage level of lOkV and below as the research object.The main work includes analysis of influencing factors of distribution network toughness,fault type analysis,toughness improvement means and system simulation.The specific work can be summarized as follows:1.Analysis of the background and significance of the resilience of urban distribution network.Explain the means proposed by domestic and foreign research scholars to improve the resilience of urban distribution network,provide the basis for follow-up research.2.Analyze the topological structure of urban distribution network and summarize the existing distribution network structure and operation and maintenance means.The factors affecting the toughness of the distribution network are mainly the selection and change of different topologies such as single radiation or ring network of distribution network,design of grid structure such as distribution network segmentation or contact switch,power supply radius and grounding mode,equipment inspection and fault handling.Representing the system function of the distribution network through the "tough trapezoid" method,proposed calculation method for evaluation index of distribution network toughness,provide quantitative standards for improvement measures for distribution network resilience.3.Analysis of the types of failures in urban distribution networks,protection improvement method for phase-to-phase faults with the highest frequency of single-phase ground faults and faults,study the protection strategy applicable to the existing urban distribution network.Using small current grounding line selection method to improve fault handling efficiency for single-phase ground faults,analyze the principle of small current grounding line selection and select the zero sequence current ratio amplitude ratio phase method to verify the protection strategy.Tliree-level coordination method for protection against phase failure,improve the resilience of the distribution network through the three-stage matching mode of "Outlet Switch+Branch Switch+Demarcation Switch".4.Research on toughness improvement for distribution network fault recovery process and propose a fault recovery method based on multi-source collaboration.By interconnecting power generation resources such as microgrid,distributed power,and energy storage in the distribution network.Establish a fault recovery model under consideration of topology constraints and operational constraints.Validation of the model in the IEEE13 node standard study.Constructing a model in PSCAD for transient simulation of fault recovery process,analyzing the fault recovery transient process.5.Propose an emergency management system.Building a disaster prevention system by combining power operations with a multi-sensor monitoring system.Combined with the power supply protection measures,an important load power supply method is proposed to improve the toughness of the system.