基于负频率频谱干扰消除的高精度低频间谐波检测算法

High-precision low-frequency inter-harmonic detection algorithm based on negative-frequency spectrum-interference cancellation

采用离散频谱分析的快速检测电网信号中存在的间谐波时,离散傅里叶变换(DFT)后的负频率频谱泄露干扰会降低检测精度。为有效消除负频率频谱泄露干扰,建立了含有负频率分量的频谱解析表达式,推导出基于最大旁瓣衰减窗的改进三谱线插值DFT,以实现间谐波的快速高精度检测。对新算法进行系统误差和噪声灵敏度分析,仿真结果表明新算法不仅能够有效消除负频率频谱泄露干扰,对加性白噪声也具有很强的鲁棒性;而且在被测间谐波低于1个频率分辨率时,新算法也能够达到很高的检测精度。

When there are inter-harmonics in the grid signal, the fast detection using discrete spectrum analysis causes the accuracy to decrease due to the negative frequency spectrum leakage interference after the discrete Fourier transform(DFT). In order to effectively eliminate the negative frequency spectrum leakage interference, the analytical expression of the spectrum containing the negative frequency component is established, and the improved three-line interpolation DFT based on the maximum side-lobe attenuation window is derived to realize the fast and high-precision detection of inter-harmonics. The systematic error and noise sensitivity of the new algorithm are analyzed. The simulation results show that the new algorithm can not only effectively eliminate the negative frequency spectrum leakage interference, but also has strong robustness to additive white noise. When the inter-harmonics are lower than one frequency resolution, the new algorithm can still achieve high detection accuracy.