消除负频率影响的低频间谐波快速检测方法

Rapid low-frequency interharmonic detection with negative-frequency elimination

对电网采样信号进行离散频谱分析时存在负频率分量,负频率对低频间谐波分量具有干扰作用;当间谐波频率邻近基波、谐波或直流分量时,其频谱会泄漏到附近的基波、谐波或直流谱线上,此时会产生主瓣干涉而无法准确检测间谐波。建立了包含负频率在内的间谐波数学模型,通过组建和求解不同位置的谱线方程组,消除了负频率的影响,得到低频间谐波参数的显式求解公式,实现了在IEC标准同步采样要求下对低频间谐波的快速检测。特别是当间谐波与附近的基波、谐波或直流分量间隔小于1个频率分辨率时,该方法仍能在有限的采样数据长度下快速精确地检测出间谐波。仿真结果表明,该方法不受直流偏移和谐波分量的影响,同时具有较好的检测速度和抗噪性能。

The spectrum analysis of discrete power grid signal samples results in negative-frequency components,which interferes with the low-frequency interharmonic. When the frequency of interharmonic nears that of fundamental,harmonic or DC component,its spectrum will leak into the spectrum lines of the later and the generated main lobe interference will influence the accurate detection of interbarmonic. A mathematical interharmonic model containing the negative-frequency is built and the influence of negativefrequency is eliminated by establishing and solving different spectrum line equations,based on which,the explicit formulas for calculating the low-frequency interharmonic parameters are obtained and the rapid lowfrequency interharmonic detection satisfying the requirements of IEC standard for synchronous sampling is realized. The proposed method can rapidly and accurately detect the interharmonic based on a limited data length of samples,especially when the interval between the interharmonic and the near fundamental,harmonic or DC component is smaller than one frequency resolution. Simulative results show that,not affected by the DC offset and harmonic components,it has better detection speed and noise immunity.