交流不对称故障类型对HVDC换相失败的影响研究

Influence of AC System Asymmetric Fault on the HVDC System Commutation Failure

文中理论推导了交流电网单相短路接地、两相短路和两相短路接地这3种不对称故障类型下,针对不同换流变接线方式(Y-Y型和Y-D型),故障特征量对直流换相过程的影响。基于向上±800kV直流输电工程PSCAD/EMTD电磁暂态仿真模型,仿真验证不对称故障类型对换流变Y桥和D桥换相失败影响的差异性。此外,还讨论了不对称故障类型对临界过渡电阻的影响规律,得到了不同故障下最易发生换相失败的换流变接线方式和导致换相失败的主要原因,对换相失败有一定的预测作用,并总结了这3种不对称故障类型对换相失败的影响程度。

In this paper, a theoretical analysis of the influence of fault characteristic quantities on commutation pro- cess in HVDC system with different converter transformers（Y-Y type and Y-D type） is put forward, in the case of AC system single-phase grounded, two-phases shorted or two-phases grounded. Based on the electro-magnetic transient model of Xiang-Shang ±800 kV HVDC system program-EMTP, we simulate and prove the different influence of asymmetric fault types on Y- Bridge and D- Bridge of converter transformers. At the same time, the interference to the critical transition resistances caused by types of asymmetric fault is discussed in detail. The bridge, which most likely to have commutation failure under different types of AC fault, and the main reason for commutation failure are also discussed. Furthermore ,we summarize the three types of asymmetry failure impact on commutation failure.