Study On The Limiting Factors Of Large-scale Wind Power Delivery Capacity

Because the wind energy resources are mainly concentrated in the north area,far away from the load center,and the local market is difficult to absorb,it needs to rely on transmission lines to implement cross-regional transmission.With the rapid development of UHV HVDC project,the scale of HVDC transmission in the power grid continues to increase,and a new UHV AC-DC hybrid pattern has been basically formed in China.UHVDC transmission has the advantages of large transmission capacity and long transmission distance,and it is the main transmission mode to solve the contradiction between energy and power load.Under this condition,a power transmission mode of large-scale centralized wind power access and long-distance ACDC combined transmission for load supply has gradually formed.However,because the new energy collection area is mostly at the end of the power grid,the short circuit capacity is small,and the local disturbance will also cause a chain reaction,which will seriously affect the delivery capacity of the collection area.The delivery capacity of new energy is affected by many factors.This paper carries out the work from the following aspects:Firstly,the paper analyzes the limiting factors of the delivery capacity of largescale new energy delivery system,mainly focusing on the voltage stability limit,thermal stability limit and the ratio of wind power combined delivery.Through the analysis of the sending capacity limitation factors,understand the reason of the limitation of the power transmission capacity,in order to better improve the power transmission capacity of the system,to obtain the maximum benefit.Secondly,the model of typical wind power gathering system is established,and the mechanism of transient overvoltage in large scale wind power gathering area is deeply analyzed.In this paper,considering the influence of the potential in the infinite system,the voltage stability of the wind power collection system under different control modes of the dynamic reactive power compensation device and the sensitivity of the voltage-internal potential in the parallel point are analyzed and deduced,and the simulation verification is carried out.The simulation results show that: when the dynamic reactive power compensation device adopts the constant reactive power control mode,the voltage of the parallel point of the fan will increase with the increase of the internal potential,so the constant reactive power control mode will raise the assisting effect on the transient pressure of the fan side.When the dynamic reactive power compensation device adopts constant voltage control,the voltage of the fan parallel dot is determined by the output voltage of the infinite power supply and the reference voltage of the dynamic reactive power compensation device,and the transient overvoltage is low after the fault.Finally,based on the large-scale wind power gathering system in the Xi Tai League region,the BPA example simulation model of the Xi Tai League wind power gathering region is established.The influence of transient overvoltage limit and thermal stability limit on the power transmission capacity of the system is simulated and analyzed,and the feasible region of combined wind and fire power transmission under the constraints of transient overvoltage stability and power Angle stability is given.The simulation results show that when the AC N-1 fault or DC commutation failure occurs in the system,the transient pressure rise of some wind power gathering stations exceeds 0.2p.u.,and with the increase of wind power allocation proportion,the transient overvoltage becomes higher and higher,so it is necessary to adopt the safety control strategy to cut off some wind farms.