Research On The Small Disturbance Stability Of Power System After Wind Power Is Connected

Because of the increasingly serious global energy and environmental problems,the world has begun to vigorously develop wind power generation technology,and China is one of the leading ones.There are many wind-power bases of ten million kilowatts level in China to realize grid connection,but with the gradual increase of wind power grid connected capacity,the power system may have weak damping or even negative damping,which seriously affects small disturbance stability of the system.Therefore,it has important theoretical and practical significance to study the small disturbance stability characteristics of power system after wind power grid connection.This paper is based on the dynamic model of the second generation of WECC type ? and type ? wind turbine generators,the following research is carried out on the small disturbance stability of power system after wind power is connected:(1)The influence of wind turbine generators with different control methods on the small disturbance stability of the system is different.However,when the wind turbine generators adopt the local constant Q control,the local constant power factor control and the plant level Q control,the impact on the damping ratio and frequency of the common control oscillation mode and the inter-oscillation mode is consistent.(2)Through eigenvalue analysis,time domain simulation analysis and Prony analysis,it is found that the grid connection of type III wind turbine generators will introduce a new of wind turbine control oscillation mode.The damping and frequency characteristics of wind turbine control oscillation mode introduced by different wind turbine control methods are different for type III wind turbine generators.When type III wind turbine generators adopt the local constant Q control,the local constant power factor control and the plant level V control + coordinated local Q/V control,the introduced wind turbine control oscillation modes all have high damping ratios,so it will not cause adverse effects on the small disturbance stability of system.When wind turbine generators use the plant level Q control + coordinated local Q/V control,the wind turbine generators do not participate in the electromechanical oscillation mode,but it will introduce the control oscillation mode that wind turbine generators and traditional synchronous generators participate in together.In this method,when the wind power penetration is high,that control oscillation mode will have a negative damping ratio,which will have a negative impact on the stable operation of the system.In other control methods,the damping and frequency characteristics of the wind turbine control oscillation mode introduced by the type III wind turbine generators are different.But there all has an oscillation mode in which the damping ratio decreases gradually with the increase of the penetration of the wind turbine in different control methods,which makes the system unstable after small disturbances.(3)It is found that new wind turbine drive train oscillation modes will be introduced when the type ? wind turbine generators are connected to the power system.When wind turbine generators use the local constant Q control,the local constant power factor control,the plant level Q control and the plant level V control,there is a wind turbine drive train oscillation mode involving most wind turbines.Its damping ratio and frequency will change with the increase of the wind power penetration.When the wind power penetration of the system is high,its damping ratio is low.This low damping oscillation mode is not conducive to the small disturbance stability of the system.In other control methods,the increase of the penetration of wind power has no effect on the damping ratio and frequency of the wind turbine drive train oscillation mode.