Research On Generation And Suppression Of Low Frequency Oscillation In Wind Power Grid

In recent years,wind power is developing rapidly in our country due to its advantages of non-polluting,renewable and abundant reserves.However,large-scale integration of wind power will cause the system stability issues,etc.,in which low frequency oscillation problem is an important factor affecting the stability of the system.Based on the actual needs of national wind power development and based on the single machine infinite system with doubly-fed wind turbine,the subject focuses on the influence of grid-connected wind power on the low-frequency oscillation characteristics of power system and discusses the specific solutions to suppress low-frequency oscillation.Researching wind turbines needs to establish generator model and converter model.Based on the general analysis method of asynchronous motor,this paper first deduces the voltage equation and flux linkage equation of the generator,then obtains the differential state equation of the generator and builds a corresponding simulation model.Then the rotor side control according to the design of this article is followed.The variables in the control loop are deduced,the control equations for achieving double closed-loop control in the controller are derived,and corresponding simulation models are built.Finally,adding mechanical part model.The entire mathematical modeling and simulation experiment model building process.In order to suppress the low-frequency oscillation of the wind power grid-connected system,this paper proposes two methods: Firstly,for the PI controller parameters in projects through the experimental debugging set will cause a lot of repeated and blind work and the accuracy is low,this paper proposes using particle swarm algorithm(PSO)to tune the excitation control parameters of the PI controller of DFIG in a wind power grid-connected system,and optimizes the parameters according to the analysis results.Secondly,this paper also proposes the method of adding PSS to make a feedback link in the rotor-side controller of DFIG,by adding a closed-loop feedback control loop to effectively increase the system damping and suppress the low-frequency oscillation.In order to verify the correctness of the proposed method,a grid-connected system with DFIG has been established.Firstly,observing the influence of wind power when DFIG is connected to the power system.Secondly,using time domain analysis method and eigenvalue analysis method to analyze the low frequency oscillation characteristics of the integration system and the suppression effects of the proposed method on the low-frequency oscillation are analyzed.The experimental results show that the excitation control parameters are adjusted and on the rotor side of the DFIG.The addition of PSS in the controller constitutes a feedback link,which can effectively suppress the low-frequency oscillation when the wind power is connected to the grid,improve the stability of the system,guarantee the power quality obtained after the grid-connected load,and ensure the transmission safety.