基于偏磁模拟的换流变选相合闸励磁涌流抑制策略

Inrush Current Suppression Strategy of Converter Transformer Phase Selection Closing Based on Magnetic Bias Simulation

特高压直流输电系统换流变压器在检修停运、切换运行方式后重新充电投运时,其剩磁和偏磁会改变铁芯工作状态,易产生严重的励磁涌流,极大增加受端换流器换相失败风险。研究了励磁涌流产生机理和串联合闸电阻对励磁涌流的影响,根据合闸电阻对合闸时磁链幅值和相位的影响特性构建偏磁函数,针对星形和三角形接线换流变压器,分别提出相应的基于偏磁模拟的选相合闸策略,计算剩磁与合闸时偏磁相互抵消的理想合闸时间,进行选相合闸。通过PSCAD/EMTDC建立特高压直流输电换流变压器空载合闸模型进行仿真分析,并基于RTDS实验平台进行实时测试验证,针对20次不同剩磁工况,Y桥换流变60个合闸涌流结果均低于0.14 kA,D桥换流变51个合闸涌流低于0.3 kA,其余结果低于0.43 kA,实验结果表明所提选相合闸策略可以有效抑制换流变压器投运时引发的励磁涌流。

After maintenance and switching operation mode,when converter transformer of ultra high voltage direct current(UHVDC)system is recharged and put into operation,its residual flux and magnetic bias can transform the working condition of iron core,which is easy to produce inrush current,and greatly increases the risk of commutation failure of receiving end converter.This paper studies the generation mechanism of inrush current and the influence of series closing resistance on inrush current.Meanwhile,according to the influence characteristics of closing resistance on the amplitude and phase of flux during closing,the magnetic bias function is constructed;for star and delta connection converter transformers,the corresponding phase selection closing strategies based on magnetic bias simulation are proposed,respectively;the ideal closing time of mutual cancellation between residual flux and magnetic bias during closing is calculated,and phase selection closing is carried out.The no-load closing model of UHVDC converter transformer is established using PSCAD/EMTDC for simulation analysis,and the real-time test verification is carried out based on RTDS experimental platform.For 20 different residual flux conditions,60 inrush current results of Y-bridge converter transformer are all less than 0.14 kA,51 inrush currents of D-bridge converter transformer are less than 0.3 kA,and the other results are less than 0.43 kA.The experimental results show that the proposed phase selection closing strategy can effectively suppress inrush current caused by the operation of converter transformer.