西北电网主变充电引起青藏直流闭锁的原因分析及对策

Analysis and Countermeasures of Qinghai-Tibet DC Blocking Caused by Main Transformer Charging in Northwest Power Grid

根据系统谐波阻抗扫描和EMTDC仿真验证,分析了西北电网主变充电产生的2次谐波电压在柴达木换流站放大的原因,提出了抑制变压器合闸励磁涌流的措施。为了降低西北电网主变充电产生的2次谐波对直流系统运行的影响,利用直流系统设备耐受谐波的能力,在交流系统安全稳定的条件下对直流谐波保护进行了优化,并应用到青藏工程中。优化后的谐波保护提高了青藏直流联网工程适应弱交流系统的能力,降低了直流系统强迫停运的概率。

hrough harmonic impedance scanning and EMTDC simulation of AC system, the reason why the second harmonic voltage, generated by the main transformers charging in the northwest power grid, was amplified in Chaidamu converter station is analyzed in this paper. Then some countermeasures are put forward to inhibit the inrush current during transformer switching-in. In order to reduce the impact of secondharmonic on the operation of DC system, based on the equipments＇ harmonic tolerance capacity in DC system, the DC harmonic protection under the security and stability condition of AC system is optimized, which has been applied to the Qinghai-Tibet Project. The optimized harmonic protection can imorove the adaDtabilitv of Oinhai-Tibet DC Project to the weak AC system, and reduce the forced outage rate of DC system.