Research On Harmonic Control Method Of Grid-connected Doubly-fed Wind Farm

Wind power has gradually dominate the power industry,and the doubly-fed wind farm in the wind power generation system in a large proportion will inevitably produce various harmonics affect the power output and the quality of the network process.In the process of grid connection,various harmonics will inevitably affect the power output quality.The impact of the output power quality of wind farms on the stability of the power grid has attracted wide attention from experts and scholars.Xinjiang has sufficient wind energy resources.Wind farms installed in the wild are prone to generate harmonics due to the changeable and complex environment.At the same time,traditional doubly-fed induction generators(DFIG)use a large number of nonlinear power electronic components.Harmonics will increase the difficulty of grid governance.Improving the ability of doubly-fed wind farms to control harmonics is of great significance to the study of doubly-fed wind farms connected to the grid.Aiming at the problem of harmonic pollution caused by grid-connected doublyfed wind farms,this paper studies the harmonic control methods of doubly-fed wind turbines and doubly-fed wind farms.Improve the output power quality of doubly-fed wind farms and reduce harmonic pollution to the grid.The specific research content is as follows:(1)The working principle of the double fed wind turbine is performed analysis,a mathematical model of DFIG grid-side converter and a vector control method of the voltage oriented Network Based,on this basis of wind power in the normal grid voltage Analyze and study the harmonics under the conditions.(2)Aiming at the problem of harmonic pollution on the side of doubly-fed wind turbines,a repetitive control theory is proposed to design grid-side converters.Converter control implemented method for analyzing network side,illustrates hysteresis current control method,the parameters of the repetitive controller was designed,after comparing with a conventional double-loop control system,the controller repeats the mathematical model,using simulation The comparison of the method proved that the repetitive control theory is significantly better than the traditional PI control,and can effectively reduce the harmonic pollution on the side of the doubly-fed wind turbine.(3)Aiming at the problem of harmonic pollution on the side of the doubly-fed wind farm,it is proposed to apply the chain STATCOM with resonance control function to the doubly-fed wind farm.The control characteristics of the chain-type STATCOM internal resonant controller are improved,and a PIR-VPI hybrid control method with low-order harmonic control is proposed.The working principle of the hybrid control method is studied,and a mathematical model is established to design the parameters of the hybrid control.It is verified in MATLAB through simulation.Theoretical analysis and simulation results show the effectiveness of this scheme to a doubly fed wind farm side harmonic control.