Research On Active Power Emergency Control Strategy Of The Sending-out System With Large Scale Wind Power

In recent years,the demand for electricity from economic development has been increasing and in pursuit of sustainable social and economic development,the grid-connected technology for new-energy power generation has been rapidly developed.In particular,more attention has been paid to the development and utilization of wind power.In China,a number of large-scale wind power bases has been put into operation in the "Three Norths" region,where wind energy resources are abundant.However,due to little demand of local loads and the obstruction of wind power consumption,the typical sending-out system with large scale wind power and local thermal power units has been formed to achieve large-scale centralized delivery.Since the wind turbine is different from the conventional unit in the weak damping characteristic,the integration of large-scale wind power has changed the transient characteristics of power system and posed new challenges to the formulation of the transient stability emergency control strategy.Therefore,it is of great significance to study the active emergency control strategy of sending-out system with large-scale wind power.The research content of this paper includes the following three parts:Firstly,aiming at the sending-out system with large-scale wind power,this paper studies the dynamic mathematical model of DFIG wind turbine and thermal power synchronous generator.The transient operation characteristics of DFIG and synch-ronous generator are analyzed and compared theoretically.It is found that wind turbine has less mechanical inertia and acceleration energy,which is more conducive to the transient stability of the system.Then through the time domain simulation and analysis,it is found that the wind power integration is beneficial to improve the system transient power angle stability and the stability margin of the first swing,but not conducive to the transient voltage recovery.Secondly,based on extended equal-area criterion(EEAC),the influence of wind power integration on the system transient power angle stability is deduced.It is found that the impact of wind power integration on the system transient power angle stability is mainly reflected in the system equivalent mechanical power.After that,the inherent correlation between the wind-thermal power capacity tripped of the emergency control is studied,and come to the conclusion that they meet certain relational equation.And verify the validity of this conclusion through simulation on the 10-machine 39-Bus New England system.Finally,based on the correlation between wind-thermal power capacity tripped,this paper proposes an active emergency control strategy of sending-out system with large scale wind power.The control strategy clearly gives both the control object and the control amount.By calculating the correlation coefficient of wind-thermal power capacity tripped,a method of determining the units to be tripped is put forward.And based on the equation of the correlation between wind-thermal power capacity tripped,a set of alternative tripping schemes considering wind-thermal power tripped are generated.Then,based on three aspects of economy,transient stability margin and transient recovery characteristics,a comprehensive evaluation index system for tripping schemes is put forward,and a subjective and objective weighting method is used to generate the optimal tripping schemes with the highest satisfaction.Through the example analysis,the results verify the effectiveness of the proposed active emergency control strategy.