The Whole Process Risk Assessment Method Of UHV AC/DC Power System In Serious Disasters

In China,the distribution of energy resources and load center are very uneven,which needs to build long-distance,large-capacity power transmission channel to achieve intensive development and nationwide optimal allocation of energy resources.The construction and operation of the UHV power grid has solved this problem and has played a huge role in promoting social development.However,its safety has been widely concerned by the community,especially in recent years.Therefore,the scientific assessment of the safety of UHV planning grid is of great significance to analysis the safety level of the system,find security risks and prevent major blackouts.And the ability of the power grid to resist the chain failure in serious disasters is one of the important reflection of the security level.Therefore,a whole process of serious disaster risk assessment method is proposed to evaluate the safety level of power system and to ensure safe operation of the power system.First of all,this thesis summarizes the mechanism and development process of chain failure in severe disaster from the three aspects of overload dominance,protection dominance and structure dominance,and determines the key factors of risk assessment.Secondly,the whole process risk assessment method of UHV AC/DC power system based on risk theory is proposed.The complete modeling research has been carried on from the aspects of initial fault selection,chain fault probability calculation,fault control strategy,judgment condition and fault recovery method.The calculation of the probability of chain failure is based on the combination of Monte Carlo method and PSD stable calculation program,which solves the problem of large computation and time-consuming under large network and improves the calculation efficiency.Then,according to the mixing characteristics of the UHV AC/DC power system and the whole process of the failure caused by the disaster,the risk evaluation index system suitable for UHV AC/DC power system is proposed from the aspects of grid structure,static safety level,fault state and economic loss,and the entropy weight method is adopted to carry out the comprehensive risk assessment.Compared with other risk assessment indicators,this index system not only considers the failure consequences,but also fully reflects the failure process before and after the whole disaster,and more in line with the characteristics of UHV AC/DC power grid.Finally,the risk assessment method is adopted to evaluate the two kinds of planning schemes of UHV power system in a region.By comparing the development process of chain failure and calculating the results according to the risk index of the accident stage and recovery stage,the optimal grid planning scheme is obtained,which proves the scientific and practicability of the research work in this thesis.