Analysis And Evaluation Of Small Signal Stability In Random Power Systems

As new energy is connected to the power system,its penetration rate continues to increase,and the problem of small signal stability of the system becomes more and more significant.Therefore,the problem of small signal stability of the power system with new energy access represented by wind energy is a direction worthy of research.This article focuses on the problem of small signal stability probability distribution of the power system when wind power is connected to the power system.In this paper,a small signal stability model of doubly-fed wind turbines connected to the power system is established based on the tool of matlab.The accuracy of the established wind power model is verified using Prony identification.Based on the established wind power model,this paper mainly conducts the following aspects:jobs.First,this paper analyzes the effect of the change of the internal voltage control parameter Kv of the doubly-fed wind turbines on the small signal stability of the power system.It is found that the change of the control parameter can effectively change the small signal stable state of the system,so it can be used as a small signal instability system.An effective means to control the small signal stability of the system;Secondly,this paper also analyzes the small signal stability change of the system when the wind power permeability changes,and studies the change of the characteristic value of the system when the wind power permeability increases,and It is concluded as follows: when the wind power permeability of the system is increasing,the double-fed wind turbine will have a decisive effect on the system of the small signal stability;the oscillation mode damping between the synchronous units will increase with the increase of the wind power permeability.It is good for the small signal stability of the system;but at the same time,the damping ratio of the associated oscillation mode of the wind turbine is reduced,which is not good for the small signal stability of the system.When the permeability is low,the damping ratio of the synchronous unit oscillation mode is the first consideration.Finally,this paper presents a method for evaluating small signal probability stability of power systems based on polynomial function expansion.This method does not consider complex non-linear structures inside the power system,but uses a high-dimensional non-linear explicit function expression to approximate complex power systems Performance,so as to achieve the purpose of obtaining small signal stability probability through a large number of simulations of function expressions,and effectively calculate the small signal probability density distribution(PDF)and cumulative density distribution(CDF)of the power system,compared to traditional point estimation The method evaluation results have higher accuracy and calculation speed.Compared with the modal analysis results of the IEEE3 machine 9-node system connected to wind power,the accuracy of the proposed probability evaluation method is verified.