滇西北特高压直流被动孤岛运行闭锁策略优化研究

Study on Block Strategy Optimization of Passive Isolated Island Operation of Dianxibei UHVDC Project

滇西北直流工程投运初期,送端配套电源开机量不足,若被动进入孤岛会面临谐波不稳定问题,给直流系统稳定运行造成极大风险,在以往的直流工程中,直流控制保护收到孤岛信号后,会尽快完成全切交流滤波器,同时延时闭锁直流的操作。但若孤岛信号异常,会导致直流误闭锁切机、损失功率。基于此,在滇西北直流工程中优化了被动孤岛低功率闭锁策略,通过增加判别交流联络线功率的方法来防止误进入孤岛运行模式。首先详细分析了滇西北直流所采取的控制策略,然后在RTDS试验系统中验证了所实施策略的正确性,通过判别交流联络线功率可有效防止误直流误进入孤岛运行模式,最后通过现场试验证明了所提控制策略也不会导致原有"孤岛闭锁逻辑"拒动。本文所述控制策略可为其他直流工程提供参考。

Due to the lack of generators at sending end in the early operation stage of the Dianxibei UHVDC project,if it is passively entered into island mode,the system will encounter harmonic instability and will cause a great risk to the steady operation. In previous projects,the strategy is to disconnect AC filters and block bipolar DC with a certain time delay when receiving island operation signal.However HVDC system may block valves,cut generation capacity or shed power by error when receiving false island operation signal.Therefore,the locking strategy at lowpower under passive island mode is optimized. In Dianxibei UHVDC project,the power on AC tie lines is used as criteria of island operation to prevent from miscarriage. The logic and realization of the control strategy are illustrated,then RTDS simulations are carried out and it is verified that by judging the power on AC tie lines,the system can effectively prevent entering island mode by error. Finally,the field test proved that the proposed optimized strategy will not cause rejecting of the existing ＂island locking logic＂. The proposed strategy can be a reference to other DC projects.