换流变压器三相直流偏磁的计算研究

为研究相邻架设的交直流线路互感在换流变压器中产生的三相直流偏磁情况，在计算了单相变压器二次侧直流电流所产生的偏置磁通与励磁电流的基础上，对直流线路基波电流引起的换流变阀侧直流电流及其在换流变三相产生的直流偏磁进行了分析，讨论了△绕组的影响，并在Matlab中对换流变三相励磁电流做了仿真计算。其结果表明：交直流线路互感引起的换流变三相直流偏磁大小不等，且会因Y-△连接而发生变化，而由此产生的变压器接地中性点零序电流的直流分量为零。

Calculation and study for three-phase DC bias of converter transformer

In order to study on the DC bias of three-phase converter transformer caused by AC and DC lines＇ mutual induction, after calculating the biasing flux and exciting current of single-phase transformer generated by secondary side DC current, the three-phase DC currents at valve side of converter transformer caused by fundamental current on DC line as well as the threephase DC biases were analyzed, effects of △ connection were discussed, and the three-phase magnetizing currents of transformer were calculated in Matlab in the end. Results show that three phases＇ DC biases generated by AC and DC lines＇ induction are different from each other, which could also change under Y-△ connection. Though the biases cause a zero-sequence current at the grounding neutral, the DC component of the current always equals zero.