Study On Short-circuit Fault Location Method For Transmission Lines Of Large-scale Wind Farms

The replacement of fossil energy by clean energy is an important direction to solve the energy shortage,and wind power has attracted much attention as a form of clean energy generation.At present,the phenomenon of ?abandoned‘ wind caused by the failures of transmission lines has occurred frequently.In order to solve the problem of quickly finding and repairing fault points after wind farm line faults,ensure the safe and reliable delivery of wind power,this paper studies the possibility of fault location for wind farms from different angles considering the structural characteristics of large wind farms and summarizing the existing fault location methods and some existing problems.The research includes the following aspects:A modified wave fault location method based on the traveling wave principle is proposed.The two core points of traveling wave method—— "road wave identification" and "wave speed calculation" are improved to improve the accuracy.The quantization error in the wave head recognition directly determines the recognition effect,so the interpolation effect is used to reduce it.For the wave velocity calculation,although the online wave velocity calculation accuracy is the highest,it is based on the double-end synchronous traveling wave method and it is not realistic for the wind farm.Therefore,a modified traveling wave velocity calculation method based on single-ended information is derived.In addition,according to the zero-sequence current criterion,the faulty branch is identified and then combined with the wave method to obtain the final fault locating result.The simulation results show that the method can effectively realize the fault location of transmission lines in wind farms.A fault location method based on parameter estimation is proposed.Considering the complex hybrid multi-branch transmission lines in wind farms,a set of transmission equations based on terminal information is established,which includes information such as fault location,cable and overhead line wave speed,and arrival time of traveling wave.Solve the equations to get the fault location.However,considering the measurement error in the actual system,etc.,"directly solving the equations" will lead to large errors,so the redundancy parameter estimation method is used to solve,which can make full use of the multi-point information and minimize the error.The sag effect problem is considered in the fault location model to ensure higher fault location accuracy.In addition,in order to solve the problem of branch misjudgment when the fault is near the branch node,a new fault branch criterion is proposed.The simulation results show that the proposed method can achieve good results in fault location,fault location under the influence of sag,and branch judgment when the node is near the fault.It is worth mentioning that the method is versatile and is suitable for arbitrarily complex overhead line-cable hybrid multi-branch line structures.A fault location method for wind farm transmission lines based on vector deviation is proposed.Considering the short distance between the wind turbines of the wind farm,the method gives up the precise locating of the fault point and focuses on finding the fault interval.According to the electrical information of each terminal measurement point,the integrated vector error(TVE)and the three-phase total unbalance degree ? are used to construct the vector deviation degree objective function of the theoretical calculation value and the real measurement value when the wind farm short-circuit fault occurs.Comparing the deviation degree calculation results of each interval,the difference degree between the fault information and the hypothetical fault interval information in real fault can be obtained,and the hypothetical fault interval with the smallest difference is the real fault interval.