Research On Fault Recovery Of Active Distribution Network For Resilience Improvement

In recent years,extreme events including extreme natural disasters such as typhoons,ice and snow,earthquakes,and malicious man-made cyber attacks have occurred frequently,resulting in large-scale power outages in the power system,resulting in huge economic losses.The resilience of the power grid is defined as the ability of the system to resist various hazards,withstand the consequences of initial failures,and quickly return to normal operating conditions,emphasizing the ability to respond to extreme events.The distribution network is located at the end of the power system,and most of them have a radial tree network topology and inherent power resource density characteristics,which make the distribution network more sensitive to strong disturbances.Resilience is the main characteristic of a resilient grid.Under extreme events,the traditional passive distribution network will cause a long-term power outage due to the damage of system components,and the connected distributed generator(DG)will be out of operation.The active distribution network adopts active management and active control technology for the connected DG,and the non-faulty DG can continue to supply power to the load after extreme events,improving the flexibility of the system.In this paper,the research on fault recovery of active distribution network under resilient-oriented centralized control and distributed control is carried out.The main work is as follows:1)The resilience index calculation of active distribution network is carried out.First,the fault response process of resilience active distribution network is introduced.Then,based on the complex network theory,combined with the structural characteristics and operation mode of the active distribution network,a complex network model of the active distribution network is constructed.On this basis,the resilience index system of the active distribution network is established and calculated.Finally,the validity of the proposed index and method is verified by the calculation results of resilience index in two scenarios of traditional distribution network and active distribution network.2)A collaborative method of reconfiguration and faulty component repair oriented to resilience improvement is proposed.First,combined with the resilience index of the active distribution network that takes into account the importance of the load,the main measures of resilience improvement on the fault recovery stage are analyzed.On this basis,a framework of collaborative strategies for reconfiguration and repair of faulty components is proposed,and the update and correlation of line state variables and node load power supply state variables in alternate coordination are given.Then,the objective functions of faulty component repair in the whole process and reconfiguration are established.Aiming at the problem that the upstream and downstream relationship of faulty components is difficult to distinguish due to the characteristics of active distribution network with multiple distributed power sources,a distinguishing method based on the method of eliminating the fault loop and circling source equivalent method is proposed.Finally,examples results show that the proposed method can effectively improve the resilience of the active distribution network.3)A fault recovery method under decentralized control of active distribution network is proposed.Firstly,the distributed control mode of active distribution network is introduced,and the fault recovery framework of active distribution network under distributed control is proposed.Then,a reconstruction scheme under distributed control is proposed,and the distributed expression process of reconstruction optimization objectives and constraints is divided into the search of the non-faulty to-be-recovered area,the search of the tie switch to give priority to the load transfer area,and the division of the island area.The coordinated control process between the Smart Terminal Unit(STU)at each stage is given.In the repairing stage of the faulty component repair,the real-time topology of the associated feeder area is established by proxy STU,and the repairing strategy of the faulty element is formulated in different associated feeder areas.Finally,the results of an example verify the feasibility and effectiveness of the proposed distributed fault recovery method.4)A fault recovery method for active distribution network under communication fault is proposed.First,an analysis framework for the impact of communication system failures on active distribution network fault recovery is established.Then,the fault recovery measures of active distribution network in the state of severe communication failure are proposed,and the GUI software of "active distribution network resilient recovery with/without communication failure" is developed.Finally,taking the active distribution network of IEEE33 nodes as an example,the resilience of normal communication and communication failure is calculated and compared in different scenarios,and the impact of communication system failure on the resilience of active distribution network is analyzed.The measures to improve the resilience of distribution network are also proposed.