功率因数的实时精确测量方案探讨

在对传统的功率因数测量方法分析的基础上 ,提出了电力系统中的功率因数的基本算法 :即基于工频量的功率因数的求取方法。传统的测量方法 ,没有很好地考虑系统的不对称性所造成的谐波以及非周期分量对功率因数测量的准确性的影响 ,测量精度不够。本文提出的基于DSP技术的功率因数测量方法 ,充分利用DSP的计算功能 ,对电压、电流的采样序列信号 ,先进行带通滤波 ,再进行傅氏滤波 ,基本上消除了非周期分量及各次谐波对功率因数测量的影响 ,得到完全的基于工频的功率因数。前置的数字式软件带通滤波能够弥补常用的硬件低通滤波的缺点 ,能得到工频附近的频带信息 ,该信息再进行傅氏滤波 ,能够得到工频分量的电压、电流 ,从而可以得到基于工频分量的功率因数。

Discussion of accurate measurement scheme of power factor

This paper proposed the accurate measurement scheme of power factor on the basis of the conventional scheme:Measurement scheme of power factor based on power frequency.The conventional measurement is not very accurate because they did not consider the effect of the harmonic wave and non periodic component on accurate measurement of factor.The proposed power factor measuring scheme based on DSP technology can make full use of the calculation function.We can use band pass filter to process the sampling series signal of voltage and current,and then we can use Fourier Filter to get the phase of the voltage and the current to get the power factor.This method can remove the influence of the non periodic component and harmonic wave on the measuring accuracy of power factor and get the power factor fully based on the power frequency.Prefix digital band filter can overcome the drawback of the hardware low band filter to get the frequency band information near power frequency.We can use Fourier filter to get voltage and current of power frequency to get power factor based on power frequency.