Reliability Assessment Of AC/DC Hybrid Distribution Network

The high penetration of distributed renewable energy and the application of DC distribution technology is an inevitable trend in the future development of distribution network.AC/DC hybrid distribution network will become one of the main forms of distribution network in the future.Compared with the traditional AC distribution network,the AC/DC hybrid distribution network can flexibly adjust the power flow in two directions,reduce the power outage range after failure and shorten the switching time of the operating state,thereby effectively enhancing the regulation capability of the network and improving the reliability and the renewable energy utilization efficiency of the network.For the reliability assessment of AC/DC hybrid distribution network with high penetration of renewable energy,it is necessary to fully consider the fluctuation of renewable energy,control characteristics and failure modes of AC/DC devices,and the coordinated regulation characteristics of AC/DC distribution network.Existing reliability assessment methods for distribution network cannot solve these problems,this paper conducts some studies on the reliability assessment of AC/DC hybrid distribution network.The main contents are as follows:(1)According to the topology of the component,the reliability models of components such as VSC converter,DC transformer and DC breaker are established,and the reliability parameters are calculated according to the actual statistical data.(2)A reliability assessment method for AC/DC distribution network based on nonsequential Monte Carlo method is proposed.Aiming at the fluctuation of renewable energy and load,a time series sampling probability model suitable for simulation method is established.The adjustment strategy of the control mode of VSC after failure is given.For the scenario where the operational constraints of the system is violated,an optimal load shedding model that considers the control modes of the VSC is developed,and realizes the reliability assessment of AC/DC hybrid distribution network with VSC control characteristics considered.(3)A reliability assessment method for AC/DC hybrid distribution network based on influence increment is proposed.Aiming at the fluctuation of renewable energy and load,a source-load joint scene clustering method suitable for analytical methods is proposed.Aiming at the low efficiency of traditional state enumeration method,the multipul failure state elimination method suitable for AC/DC distribution network is proposed.On this basis,the reliability evaluation method of AC/DC hybrid distribution network based on influence increment is proposed,which effectively improves the efficiency of the reliability assessment for AC/DC hybrid distribution network.