Research On Fault Characteristics And Protection Strategy Of Large-scale Wind Farm

With the vigorous development and support of wind power in various countries,the installed capacity and scale of wind farms are also increasing.At present,the research of single wind turbine is relatively perfect,but we still lack the research about the characteristics of large-scale wind farm.However,the fault characteristics of wind farms are obviously different from those of traditional motors,but the protection of wind farm configuration is mostly based on the protection of traditional synchronous generators,which will affect the normal operation of the protection.Therefore,the three aspects of the aggregate equivalence of wind farms,the fault characteristics of wind farms,the fault characteristics of wind farms,the influence of wind farm side protection and improvement measures are thoroughly studied in this paper.Firstly,this paper presents two methods of aggregated wind farm: the first one is wind farm equivalent method based on 2-D cloud model,assuming the random location and velocity and random fault,extracting active power and voltage drop of each fan output value,according to the value of three digital characteristics of cloud model.According the three digital characteristics,we can obtain the clustering result;second kinds of wind farm equivalent method of multiple fault factors and based on the weight,according to wind speed,capacity and wind farm from the PCC bus to form a respective impedance clustering result,and then according to these factors impact on the fault of short circuit current to determine the final the clustering results.Then,an example is given in the DIgSILENT simulation software,and the two equivalent methods are compared with the detailed model.Finally,the advantages and applicability of the two equivalent methods are illustrated.Then,based on the equivalent model of wind farm,the fault characteristics of wind farm are studied,including the fault characteristics of doubly fed wind farm and direct drive wind farm.Firstly,the influencing factors and the mechanism of the fault are analyzed,then the fault characteristics of the wind farm are obtained,and the causes of each fault characteristic are analyzed,and the model is built in the simulation software to get the simulation results.Finally,the effects of these fault characteristics on relay protection are studied and the corresponding improvement measures are put forward.Firstly,this paper analyzes the influence on longitudinal differential protection,considering the differential current and brake fault current characteristics after wind farm formula,can affect a more intuitive and effective description of the fault characteristics of steady pilot protection based on the traditional formula from the point of view;an improved scheme for longitudinal differential protection based on fault components is proposed.,the first theoretical derivation of the differential current and brake current formula,the formula from the angle that the superiority of improved methods,and then build the equivalent model of wind farm,the simulation results show the correctness of the analysis.After that,the influence of fault characteristics on impedance distance protection is analyzed.Aiming at the impact of wind farm fault characteristics on distance protection,an improved method of time domain R-L model distance protection based on two terminal information is proposed and verified by simulation.