多馈入高压直流输电系统中功率倒向问题

Power converse in multi-infeed HVDC system

高压直流输电系统逆变侧电力系统发生故障时,可能导致换流站出现线路的功率倒向。介绍了传统功率倒向的发生原因及解决方法,针对多馈入直流系统,建立了交直流互联系统EMTDC仿真模型。对于逆变站交流侧各种故障以及直流输电线路故障进行了分析。研究表明,在电气距离较近的多馈入直流系统交流侧发生严重故障时,可能导致两换流站同时发生换相失败,并导致换流站邻近多条交流线路发生功率倒向,纵联方向保护可能误动;直流线路故障一般不易引起功率倒向。对换相失败导致的功率倒向发生机理进行了阐述,故障恢复时无功需求急剧增加是倒向的主要原因。针对纵联方向保护易误动提出了实用的解决方案。

When fault occurs at the inverter side of HVDC power system,the power converse of power lines near converter station may happen. The causes and solutions of the traditional power converse are introduced and the AC-DC interconnected power system model is established with EMTDC for the multi -infeed HVDC system. The faults occurred at the AC side of inverter stations and of the HVDC transmission lines are analyzed,which shows that,if severe fault occurs at the AC side of the muhi-infeed HVDC system,especially when the fault distance is short,it may lead to the commutation failure in both converter stations simultaneously,the power converse of AC lines adjacent to inverter stations and the misoperation of pilot protection. In general,the fault of HVDC transmission line is unlikely to cause the power converse. The mechanism of power converse caused by commutation failure is presented ：the demand of reactive power during fault recovery increases rapidly. Practical solutions to pilot protection misoperation are put forward.