Research And Design Of Double-fed Wind Farm Short-circuit Calculation And Protection Setting Optimization

With the large-scale grid connection of doubly fed wind farms,the design requirements are constantly improving.The topology of centralized grid connected wind farms is complex,and the existing wind turbines generally have the ability of low voltage ride through(LVRT),which makes the calculation of short-circuit current in the whole wind turbine group difficult.In the past,most of the short-circuit fault points were bus PCC points,few other fault points were considered,and crowbar protection was not considered.Because of the long distance and many circuits of wind power collection lines,there are not only adaptability problems in the application of conventional power relay protection,but also coordination problems between wind power relay protection and LVRT and regional protection.In view of the above problems,the short-circuit current calculation algorithm and protection coordination of doubly fed wind farm are studied.Firstly,the accuracy and practicability of the algorithm are improved.The simulation analysis of the wind farm fault when crowbar protection is put into operation and the converter is working is carried out,and the simulation analysis of the impact of the value of crowbar protection put into operation and the time of putting into operation on the fault is carried out.Research on doubly fed induction with crowbar protection Based on the analysis of the practical impedance model of the generator(DFIG),this paper cluster and group the crowbar protection after the fault occurs by considering whether the crowbar protection is put into operation or not,and at the same time take into account the transfer impedance of the collector line and transmission line,and simplify the topology of the wind farm by using the equivalent idea of equal power loss and single machine weighting An improved algorithm for calculating the short circuit current of typical fault points in the meter.Using PSCAD / EMTDC software,a wind turbine group simulation model is built based on the project example,and compared with the national standard method,the accuracy and feasibility of the improved algorithm are verified.Secondly,it studies the setting scheme of wind power collection system to solve the coordination problem of regional relay protection and LVRT.This paper analyzes the coordination between the existing box type transformer protection and the collector line protection,and analyzes the short-circuit current change curve of the collector line considering the main influencing factors.Combined with the current three section protection setting scheme of current collection line,considering its cooperation with box type transformer protection,adjacent collection line protection and LVRT,the adaptive inverse time low voltage directional protection is proposed as the main protection and current protection as the backup protection.On this basis,the PSCAD software is used to carry out the simulation calculation of an example to verify the correctness of the theoretical analysis.Finally,according to the above research results,a design and calculation software of doubly fed wind farm is developed by using C# and SQL server,which preliminarily meets the use requirements of the design unit and has available value.