换流变压器空载励磁涌流选相关合控制策略

针对由单相变压器构成的500 kV换流变压器组,建立了考虑铁芯非线性磁滞特性的变压器模型。仿真分析了关合角度及铁芯剩磁对换流变压器空载合闸励磁涌流的影响。研究了变压器空载合闸时抑制励磁涌流的选相关合策略。研究结果表明,当铁芯剩磁可忽略时选相关合策略为:A相在电压峰值时刻关合,B、C相延时5 ms同时关合。当考虑剩磁影响时,空载关合的选相控制策略必须考虑变压器切除时断路器三相开断的顺序,选取剩磁最大的第二开断相最先关合。当最大剩磁为正(或负)时,以该相母线电压负(或正)峰值时刻提前约0.6 ms作为该相关合时刻,变压器切除时最先开断的相延时5.45 ms关合,最后开断的相延时6.14 ms关合,可以起到抑制励磁涌流的良好效果。

Controlled switching strategies to eliminate the inrush current of converter transformer

An equivalent circuit model considering the non-linear hysteresis characteristics of iron core is established for 500 kV converter transformer composed of single-phase transformers. The influence of closing angle and core remanence on the no-load excitation inrush currents of converter transformer is simulated and analyzed. The results show that when the core remanence is negligible, the phase controlled switching strategy is that phase A closes at the peak voltage moment, and phase B and C close simultaneously with a delay of 5 ms. When considering the effect of core remanence, the no-load switching strategy must consider the order of three-phase breaking moment as the transformer is removed, the phase controlled closing strategy is that the second breaking phase with the largest remanence closes first. If the maximum remanence is positive (or negative), the moment of switch is about 0.6 ms ahead of the negative (or positive) peak time of the bus voltage, the delay time of first break phase is about 5.45 ms and the last break phase is about 6.14 ms. The method can restrain the inrush current effectively. This work is supported by National Key Research and Development Program of China (No. 2017YFB0903700) and Science and Technology Project of China Southern Power Grid Company (No. CGYKJXM20160021).