基于双层负序差值与负序测距的风电场集电线不对称故障定位OA北大核心CSTPCD

The collecting line in wind farms is accessed in a dense fashion by complex power sources.This makes existing fault localization methods inapplicable.Therefore a fault localization method for asymmetric faults is proposed based on bi-level negative-sequence difference and negative-sequence fault distance calculation.First,the fault current characteristics of wind turbines(WTs)are analyzed,based on which mathematical models of WTs can be constructed from the perspective of negative-sequence.The equivalence of wind farm negative-sequence networks is further implemented considering the structural characteristics of wind farms.Then,introducing a fault simulation strategy,the difference between simulated and actual faults is characterized by the negative-sequence voltage difference to identify the first node of faulty areas.The variation trend of negative-sequence voltage from actual fault scenarios to specific simulated fault scenarios is explored,and the negative-sequence voltage ratio is defined to eliminate the effect of fault point current.From this a criterion based on the negative-sequence voltage ratio difference is proposed to achieve identification of the second node of faulty areas.Finally,fault locations are determined by a fault distance calculation formula derived from the two-terminal negative-sequence quantity of faulty areas.Verification results from PSCAD/EMTDC show that the proposed method can accurately locate various asymmetric faults of collecting lines by just a few measurement points.The applicability to collecting lines with line branches is also considered.The localization performance is not affected by fault locations,fault resistance,WTs,wind speed distribution or asynchronous data.