摘要
为解决风电场集电系统长期存在的线路单相接地故障处理难题,提出风电场中性点柔性接地方式,理论推导获得柔性接地风电场三序等效电路,与集电线路单相接地故障复合序网模型,建立风电场零序电压柔性调控理论,提出集电线路单相接地故障柔性电压消弧方法,可主动将故障点电压及故障残流迅速抑制到零,实现单相接地故障电弧的可靠消除.进一步提出基于零序电流动态增量的高阻故障辨识与保护方法,通过柔性调控零序补偿电流,逐渐放大故障残流,实现永久性单相接地故障的灵敏感知与保护.利用PSCAD/EMTDC 搭建含双馈异步风电机(doubly-fed induction generator,DFIG)的规模化风电场模型,模拟多种运行与故障条件对所提方法进行验证,仿真结果表明,该方法能够在考虑系统不平衡电压的情况下精准调控集电线路故障点电压,实现瞬时性单相接地故障快速可靠消弧,动态感知并持续抑制永久性单相接地故障残流,实现集电线路高阻接地故障的灵敏保护.该技术有望提升风电场运行灵活性与故障防御能力,有力保障新能源电能外送的持续性、可靠性.
Abstract
To solve the long-standing problem of single-phase grounding fault treatment of the collector line in wind farm collector system,a flexible grounding mode of wind farm is proposed.The three-sequence equivalent circuit of flexible grounding wind farm and composite sequence network of single-phase grounding fault are derived.A novel method of flexible voltage arc suppression based on zero-sequence voltage flexible control is proposed,which can actively suppress the fault voltage and fault residual current to zero to realize reliable arc suppression.Furthermore,a high-resistance fault identification and protection method based on dynamic increment of zero-sequence current is proposed.The fault residual current is gradually amplified by regulating the zero-sequence current to realize the sensitive detection and protection of permanent grounding fault.A large-scale wind farm model with doubly-fed induction generator(DFIG)is established in PSCAD/EMTDC,the simulation results under various fault conditions show that the method can control the fault voltage of the collector line considering system unbalanced voltage.It realizes arc suppression of transient single-phase grounding fault,dynamically detects and suppresses the residual current of permanent grounding fault,and achieves protection of high-resistance grounding fault of the collector line.This technology is expected to improve the operation flexibility and fault defense ability of wind farm,and effectively guarantee the continuity and reliability of new energy power delivery.
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