Impact Of Large-scale Wind Power Access On Power System Cascading Failures And Risk Assessment

At present,with the access of large-scale new energy sources,the power system is becoming more and more complex,and the uncertainty in the system is greatly increased,which will increase the risk of cascading failure in the power grid.Using a reasonable method to search for cascading failure paths can detect the weak lines in the power grid in advance,which is of great significance for preventing the occurrence of cascading failures.This thesis focuses on cascading failure path search of power system and impact of wind power access on cascading failure paths.The main research work is as follows:(1)Based on the traditional power grid,the influencing factors that may cause cascading failures are analyzed.The evidence theory is improved to make it suitable for path searching for cascading failures.The various influencing factors are combined to find possible cascading failure paths.The searched cascading failure paths are analyzed,and the critical lines of the system are identified by the defined line vulnerability indicator.(2)The static model and dynamic model of the doubly-fed wind turbine are introduced.According to this model,an IEEE39 node system simulation mode with large-scale wind power is built.The relationship between wind power permeabilit y and system frequency stability,voltage stability and power angle stability is explored by constantly changing the permeability of wind power in the IEEE39 node systems.The simulation analysis shows that system stability is degraded and the stability margin is reduced with the increasing penetration of wind power.(3)A longitudinal time series model of wind turbine output is Established.A time probability model of wind turbine output is established based on 24-hour wind turbine output power in a quarterly time interval.On this basis,the plant growth simulation algorithm is used to search the cascading failure path of the system with large-scale wind power,and the probability distribution of the wind turbine output power with time is considered to obtain the time pro bability path of cascading failure.