Research On Vulnerable Lines Identification And Early Warning Of Cascading Failures In Power System Integrated With Wind Farms

With the rapid growth of the on-grid energy of wind power,the security and stability issues of power systems has become increasingly significant.In addition,due to the long-distance diverse distribution between energy resources and load centers in our country,the development of wind power is characterized by large-scale integration.Wind power integration has led to great changes in the topology structure and the distribution characteristic of power flow of power grid,bringing new challenges to the vulnerability analysis and fault early warning of the power system.In consideration of the influence of wind power integration,it is proposed that a model that can quickly identify the vulnerable lines in the system and can detect early-warning signals before the cascading fault occurs should be built by using the monitored operation data,and this model has important directive significance to the prevention of large blackouts.Firstly,for the identification of vulnerable lines in the power system considering the wind power integration,in this paper,the vulnerable lines that can easily lead to cascading faults in the system are identified by making use of the power flow data and the incremental power flow entropy considering the power line itself carrying capacity of the power flow margin is proposed based on the traditional transfer entropy,so as to adapt to the great change in real-time power flow of the lines after wind power integration;then,the structural changes of power grid caused by the integration of wind power is characterized by structural importance;Last,the two assessment indexes are merged into a novel line vulnerability assessment index by using entropy weight analysis method,which can assess the vulnerability of the lines from the two aspects of the power flow transmission and structural link.In this paper,a synchronization model considering the inner topology of wind farm is built based on the ADPSS system to study the vulnerability of the internal lines of the wind farm and the lines of the system,and the simulation results show that the proposed assessment method and indexes is effective.Secondly,to detect early-warning signals of the power system considering the wind power integration,in this paper,the information indicating the sign of cascading fault of the system is found out through analysis on the time domain monitoring data;in other words,time-domain measurements taken from the system before the transition show the statistical patterns(i.e.the increase of variance and autocorrelation coefficient).so a method that can identify the “critical slowing down” signals in the time series data without detailed network models,are be proposed to warn operators when a power system approaches critical operating points(such as voltage drop)and obtaining the cascading fault early-warning system for wind power.The simulationresults show that the variance and the autocorrelation coefficient are obviously increasing before the voltage drop,which verify the validity of the cascading fault early-warning system for wind power in this paper.In this paper,the vulnerable line identification model and the early warning model of cascading failure considering the wind farm integration have certain timeliness and extensive application value because they can be easily obtained through analysis on the operation data without the need for building a cascading failure evolution model by using a large amount of parameter data.