Research On Fault Recovery Strategy Of AC And DC Distribution Network

With the development of flexible HVDC technology,DC power distribution technology has become more and more widely used in distribution networks.DC distribution lines access distributed power sources and DC loads in AC distribution networks and DC distribution lines.It will increase the power supply efficiency of the distribution network.The future distribution network must be a hybrid AC-DC distribution network.The rapid processing of power distribution faults is an effective means to improve the reliability of power supply and ensure the stable operation of the system.Fault recovery is an important part of distribution feeder automation.The level of fault recovery directly affects the power quality of the grid to the user.The distribution network is directly oriented to users.Perfecting the fast fault recovery system can effectively reduce the outage range,shorten the power outage time,and improve the intelligent level of fault handling.Existing fault recovery algorithms mainly study the fault recovery of multi-contact AC distribution lines.Some studies have considered the access of distributed power sources,but do not consider the impact of DC distribution lines.This paper studies the fault recovery of distribution networks with DC distribution lines.Firstly,the status quo of the distribution network and fault recovery methods are introduced.Fault recovery methods are mainly divided into mathematical programming methods,heuristic algorithms and artificial intelligence methods.Secondly,the network topology of AC distribution lines and DC distribution lines is summarized.The AC distribution lines mainly include single-supply radial networks,single-loop network hand-in-hand connections,multi-segment multi-contact connections,and 1/3 ring network connections.1/4 ring network connection and double ring network connection;DC distribution line mainly has chain topology,two-end topology and ring topology.Based on the above network topology analysis and the principle of fault recovery of AC power distribution lines,the network loss,the number of voltage-limiting nodes at the end of the line,and the number of switching operations are selected as indicators to construct an objective function and list the AC and DC side constraints.The DIgSILENT/PowerFactory software performs fault recovery simulation on the improved IEEE123 node study.When the AC side fault occurs,consider the impact of the DC sidecircuit,DC load,and distributed power supply for fault recovery;on the DC side,consider changing the DC side operation mode or Planning island operations to complete the restoration of DC line faults.The research on fault recovery technology of AC/DC power distribution network can effectively reduce the time of power outage of AC/DC hybrid power distribution network,improve the reliability of power supply,and provide technical support for the operation and control of high-density distributed power supply after accessing distribution network.