考虑CVT输出特性的换流变剩磁测算方法

特高压换流变空载合闸时，其剩磁会改变铁心磁通的大小和方向，极易造成严重的励磁涌流，导致换流变无法正常投入运行。针对换流变剩磁测算，分析电容式电压互感器(CVT)输出数据存在误差是由系统频率变化引起的，根据误差式进行校正并基于电压积分法给出考虑CVT输出特性的换流变剩磁测算方法。在PSCAD/EMTDC中搭建相关仿真模型，对Y、D桥换流变的电压正向、负向峰值处分别进行分闸实验，并根据所提测算方法确定换流变剩磁。利用校正前、校正后以及监测的换流变剩磁完成选相合闸对比实验，实验结果表明所提方法能够有效测算换流变剩磁，为励磁涌流抑制手段提供参考依据。

Calculation method of converter transformer residual flux considering CVT output characteristics

When the ultra high voltage converter transformer is closed without load, its residual flux changes the size and direction of the iron core magnetic flux, which easily causes serious inrush current, leading to the converter transformer failing to operate normally. For calculating the converter transformer residual flux, it is analyzed that the error in the capacitor voltage transformer(CVT) output data is caused by the change of system frequency. Correction is made based on the error formula and a calculation method of the converter transformer residual flux considering the CVT output characteristics is proposed based on the voltage integration method. The relevant simulation models are built in PSCAD/EMTDC, the opening experiments are conducted in the positive and negative voltage peaks of the Y and D bridge converter transformers, and the converter transformer residual flux is determined based on the proposed calculation method. The comparative experiment of phase selection closing is completed using pre-correction, post-correction and monitored converter transformer residual flux. The experimental results show that the proposed method can effectively calculate the residual flux of converter transformer, providing a reference basis for the suppression of inrush current.