Application Research Of Four Winding Induction Filtering Trans-Former In Wind Farm Substation

The vigorous development of wind energy alleviates the global energy crisis,en-vironmental pollution and other problems.However,the wind power output has the characteristics of intermittent and undulation.At the same time,the power electronic devices exist in a large number of wind farms,which bring complicated power quality problems such as harmonic pollution,voltage fluctuation and low power factor to the wind farm.In this paper,the actual wind farm in Hunan province is tested by power quality analyzer for a long time,and the actual operation data of the wind farm are obtained.The harmonic,voltage fluctuation and voltage deviation of the wind farm are analyzed by the scatter plot,95%probability large value method and probability dis-tribution function.The existence rule of power quality in harmonic,voltage fluctuation and voltage deviation of the wind farm is revealed.In the dense area of wind farms,multiple wind farms are often connected to the grid through the same substation,which will further exacerbate the power quality prob-lems at the connection point.This paper mainly focuses on the power quality problems in the substation with connection to wind farms.Based on the induction filtering theory,the four winding induction filtering transformer is used to control the power quality of the substation.In this paper,the working mechanism of the four winding induction filtering transformer is studied,and the impedance characteristics and the filtering mechanism of the transformer are analyzed in detail.Secondly,the mathematical model and the equivalent circuit of the four winding induction filtering transformer are stud-ied.Then,in order to realize the design of the filter winding,the layout method of filter windings and the parameter calculation method of the four winding induction filtering transformer are introduced.Based on the background of the proposed wind farm substation in Hunan Province,this paper first derives the harmonic current of the full load of the wind farm with connection to the collection station according to the measured data,and the superposi-tion principle of harmonic current is used to calculate the harmonic content of all wind farms to the 110kV side.The load side harmonic content is calculated according to the 35kV side load of the collection station.Then,based on the theoretical knowledge of the four winding induction filtering transformer,combined with the winding design and impedance design method,based on the background of this project,the parameters of the four winding induction filtering transformer and the traditional three winding transformer are designed and selected,respectively.According to the demand of reac-tive power compensation,the configuration parameters of full tuning device of the induction filtering can be calculated.According to the obtained parameters,the simulation model of the substation with connection to multiple wind farms is built on the PSCAD/EMTDC platform,and the harmonic current and harmonic voltage of the 220kV grid side of the substation are simulated and analyzed.In this paper,the filtering performance of the four winding induction filtering transformer and the traditional three winding transformer is com-pared and analyzed under the two modes including full load and under load of the wind farm.The simulation results show that compared with the traditional three winding transformer,the four winding induction filtering transformer has a significant effect on the control of the 220kV grid side harmonics of the wind power substation.After using the four winding induction filtering transformer,the power factor and voltage of the 220kV grid side of the substation can meet the actual operation requirements of the grid.In particular,the four winding induction filtering transformer can still achieve good filtering effect and have good dynamic response performance when the wind farm output is abrupt.