Research On The Influence Of Wind Farm's Integration On Power System Transient Stability

Since the 21 st century,the world has vigorously developed clear energy generation technology to cope with the global energy crisis and environmental problems.Wind power has become an important part of the clear energy generation field with its mature technology and sufficient reserve content,and the wind power penetration in the power system has increased year by year.Wind turbines are usually integrated in large scale,which changes the topology structure of the grid,resulting in the change of power flow and the stability margin of the power system.In addition,during the period of failure,the wind turbine requires the low voltage ride through(LVRT)capability to keep the wind generators from disconnection.The LVRT of wind turbine will absolutely bring new influence to power system.Therefore,the influence of wind farm integration on power system transient stability should be considered comprehensively.In this paper,the current research of doubly fed induction generator's(DFIG)influence on the transient stability of power system is completely summarized.And it is pointed out that the influence of DFIG on the transient stability of the system should be considered in three aspects: DFIG has no rotor motion characteristic,changes the stability margin of the system and has different power output under each LVRT schemes.Based on the dynamic motion of power system,this paper proposes a transient energy function method to analyze the influence of DFIG on transient angle stability of power system.Firstly,the transient energy function of single machine infinite bus system is constructed based on the classical model of power system.Then,the equivalent parallel grounding admittance model of DFIG is introduced,and by transforming the influence of DFIG on system topology into the change of network parameters,influence on the stability margin of the system is analyzed.Furthermore,the influence mode of DFIG on the system's state variables and energy accumulation process is proposed,and the relationship between DFIG's power change and energy accumulation is analyzed.Through the analysis of transient energy function method,the influence of DFIG on the system stability margin and the analysis of the influence on transient stability during LVRT are both considered.This paper also considers the influence of DFIG's integration to multi-machine system on transient stability.The inertia center angle of all synchronous generators is introduced to be the reference of the whole system,and all the generators are divided into two clusters,which greatly reduces the complexity of the system analysis.According to the reduction of system's augmented network with DFIG,the influence of the external power of DFIG on the electromagnetic power of synchronous machine is converted into the influence of the electric distance between the nodes of the generators,and then the quantitative analysis about the influence of DFIG on the generators' electromagnetic power is realized.The transient energy function of the system is constructed under the motion mode of the two cluster system,and the criterion about the influence of different LVRT schemes on the transient stability during the fault is derived.