应用于智能电网的高压直流电流及谐波测量方法研究

Research on current and harmonic measurement method for HVDC applied in smart grid

智能电网的发展对相应的测量设备提出了更高的要求,包括体积小、重量轻、准确度高、测量频带宽等.本文研究了一种应用于智能电网的高压直流电流及谐波电流测量方法.直流电流测量采用基于霍尔磁场传感阵列的测量方式,采用多个传感器构成传感阵列,有效降低导体偏心、偏角等因素的影响;直流谐波电流测量采用4个直线型线圈构成的方形Rogowski线圈作为传感单元,并利用改进的高精度数字积分算法实现线圈输出的积分还原,大大降低了频率变化等因素的影响.同时,提出一种基于梯形自卷积窗的四谱线插值DFT算法,有效提高了直流分量及谐波分量的提取准确度.测试及应用结果表明,该新型高压直流测量互感器直流电流测量误差小于0.10%,谐波测量比差变化小于0.2%,角差变化小于8′,输出信号为数字量.该测量设备具有准确度高、测量频带宽、体积小等优点.

The development of smart grid has put forward higher requirements for the measuring equipment,such as small size,light weight,high accuracy and wide frequency band.A current and harmonic measurement method for HVDC applied in smart grid is studied in this paper.A measuring method based on the Hall sensor array is proposed to measure the DC current.Multiple Hall magnetic field sensors are used to form a sensor array,which can effectively reduce the influence of conductor off center and angular deflection.For the harmonic current measurement,a square Rogowski coil which made of four straight bar coils is designed and a high precision digital integral algorithm is used to realize the integral of coil output,which can reduce the influence of frequency changing.Besides,a four-spectral line interpolation DFT algorithm based on trapezoid convolution window is proposed,which can improve the extraction accuracy of DC component and harmonic components.The test results show that the DC current measurement error is less than 0.10%,the variation of the harmonic measurement ratio difference is less than 0.2%,and the angle difference is less than 8′.The output of the HVDC transformer is a digital output,which has the advantages of high accuracy,wide measuring frequency band and small volume.