应用于电力谐波分析的改进相位差校正法

Improved Phase Difference Correction Method Applied to Power Harmonic Analysis

传统的相位差校正法在应用于电力谐波测量时,由于频谱泄漏问题的存在,在窗函数的旁瓣衰减速度较慢时存在较大误差,而校正过程对频域解析式的依赖又限制了窗函数的选用。采用一种基于汉宁窗的改进相位差校正法,其原理是对非同步采样序列的加窗快速傅里叶变换结果进行多项式变换,再依据变换所得的新频谱序列进行谐波参数的校正。将该方法和其他常用方法进行数值仿真对比,在基频随机变化的情况下进行10 000次仿真计算得到其标准误差,并缩短采样窗长以探究其实时性。结果表明,改进相位差校正法较其他常用方法有更高的精度;当基频在47~53 Hz范围内随机变化时,高次谐波的测量精度达到10-5次;在100 ms的采样窗长下,也能满足IEC 61000—4—7标准的精度要求。在兼顾计算精度的同时,该文校正公式由汉宁窗解析式推导得到,简便明了,所提方法是一种有实用价值的谐波参数检测算法。

Due to spectrum leakage,traditional phase difference methods with little attenuation of side lobe led to a larger error in the measurement of power harmonic. And the selection of window is restricted because the dependence on analytic expression. This paper uses an improved phase difference method that based on Hanning window. It performs polynomial transformation on the result of fast Fourier transform（ FFT） to get a new sequence,then adjusts harmonic parameters with the new sequence. To verify its performance,do simulation calculation and compare it with other common methods,simulate for 10 000 times at random frequency to calculate its standard error,shorten the sampling window to explore its real-time performance. The results show that,the new method is more accurate than other methods,when the frequency ranges between 47 Hz and 53 Hz,the accuracy of harmonic parameters reaches to 10-5. And under the 100 milliseconds sampling length,it also can satisfy the IEC 61000—4—7 standard. Taking computational accuracy into account,the correction formula is derived from Hanning window and it＇s quite simple. It＇s a useful harmonic parameters detection algorithm.