Research On Cascading Failure Modeling Of AC/DC Hybrid System

In this era of rapid economic growth,the power system is developing rapidly to large-scale AC/DC hybrid grid,and the complexity of the power grid increases.At the same time,with the development of smart grid strategy and information technology,the security and stability of power system brought by information physical integration has become prominent.More and more research shows that many blackouts are related to information system.In this context,based on the research status of AC/DC system cascading failure and AC/DC CPPS cascading failure,a predictive method and evolution model of AC/DC CPPS cascading failure are established.The main work is summarized as follows:Firstly,the research background and significance of this paper are introduced.The simulation model of power system cascading failure so far is summarized.The research status of AC/DC system cascading failure and the research status of AC/DC CPPS cascading failure are summarized.Secondly,the transient process of AC/DC system protection and control is mostly ignored in the current models of AC/DC system chain fault prediction.In this paper,the cascading failures are divided into three time scale processes,and corresponding simulation models are established according to different time scales.Then,based on three time scale process models of AC/DC system cascading failure,a method of forecasting cascading failure of AC/DC system is established and risk assessment is carried out.The interaction model of AC/DC is established.DC modulation,generator scheduling and emergency load shedding measures are used to build a general AC line overload coordination control scheme.The initial fault of AC line is selected by the inherent risk value of the line,the lower level line prediction is carried out according to the weighted fuzzy c-means clustering algorithm,and the end criterion of cascading failure prediction is determined,and the cascading failure prediction method of DC system of interchange is finally determined.IEEE39 node system is taken as an example,the chain fault process simulated by this prediction method is analyzed in the paper,and compared with the chain fault process simulated by other methods.It mainly shows the advantages and disadvantages of the prediction method from the aspects of time scale characteristics and whether it is in line with the actual situation.The results show that the risk difference will be caused by different control measures in different stages of accident chain.The cost of DC modulation can be reduced by adding DC modulation into the control measures.Finally,the CPPS is modeled,including power network modeling,power communication network modeling and communication channel modeling.Based on the above-mentioned methods of AC/DC system chain fault prediction,the information node failure and information up/down failure are considered,and the evolution model of AC/DC CPPS chain fault is established.IEEE39 node system is taken as an example,the case study verifies the effectiveness of the multi-time scale AC/DC CPPS cascading failure model.The results show that the average risk of the failure of the general overload information upload failure caused by the delay of information transmission is the highest,and the control cost of the accident chain will be too high due to the failure of the information node.The information failure should be paid more attention in the grid.This provides guidance for the prevention and control of cascading failures of AC/DC CPPS.