高频信号注入法测量配电网电容电流及滤波的研究

Research on signal injection method with high frequency for distribution network capacitive current measurement and filtering

为解决信号注入法测量配电网电容电流方法的频率选取和工频干扰等问题,分析了高频信号注入法的原理并对高频法进行改进。首先通过注入5 000 Hz高频信号求得电感值,然后通过扫频确定电网谐振频率,根据公式可计算出配电网对地电容值,并在扫频时通过串联电容的方法降低大对地电容系统的电容值,实现大对地电容系统电容电流的测量。同时运用数字信号处理器TMS320F28335,采用有限冲击响应滤波器(FIR)算法实现滤波功能,滤除扫频时注入信号中的工频干扰。通过理论分析和实验验证,该方法能够增加测量对地电容的范围,简化计算,滤除工频信号,使测量时的相对误差均不超过5%。

In order to solve the problems such as frequency selection and power frequency interference of the signal injection method to measure the capacitance current of the distribution network,this paper analyzes and improves the method of high frequency signal injection. Firstly,the inductance value is obtained by injecting 5 000 Hz high frequency signals,and then the resonance frequency of the power grid is determined through the frequency sweep method and the distribution of capacitance current value is calculated according to the formula,and by using the method of series capacitor to reduce the capacitance of big earth capacitance system,so as to realize accurate measuring capacitance current. At the same time,the filtering function is achieved by using the digital signal processor TMS320F28335 and the finite impulse response（ FIR） filter algorithm to filter the power frequency interference signals when frequency sweeping. Through theoretical analysis and experimental verification,this method can increase the range of capacitance to ground measurement,simplify the calculation,filter the power frequency signal,and the relative error of the measurement is less than 5%.