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

Bi-level negative-sequence difference and negative-sequence fault distance calculation-based fault localization for asymmetric faults of collecting lines in wind farms

针对风电场集电线上复杂电源密集接入使得现有定位方法应用困难的问题,提出一种基于双层负序差值与负序测距的风电场集电线故障定位方案。首先,深入分析风机故障电流特性,从负序分量出发实现风机建模,同时计及风电场结构特点对其负序网络实施等效。然后,引入故障模拟策略,通过负序电压差值表征模拟故障与实际故障的差异以识别故障区域第一节点,进一步探究从实际故障场景到特定模拟故障场景的负序电压变化趋势,并定义负序电压比消除故障点电流影响,由此提出负序电压比差值判据以实现故障区域第二节点识别。最后,针对故障区域利用双端负序量推导测距公式确定故障位置。PSCAD/EMTDC验证表明,所提方案能够以较少测点计及含线路分支集电线的适用性准确定位集电线各类不对称故障,且定位效果不受故障位置、过渡电阻、风机、风速分布及相量不同步等因素影响。

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.