一种电力系统谐波信号的加窗频移算法

A Window Frequency Shift Algorithm for Power System Harmonic Analysis

为实现非同步采样条件下谐波参数的高精度分析,避免插值过程的非线性导致对谐波相位计算存在较大误差的问题,提出了一种电力系统谐波参数估计新算法,即加窗频移算法。推导了加窗信号频移关系式,将加窗信号在频域上移动该频移量的频率单位,使谐波分量采样序列的离散频点与真实频点一致。通过频移信号的离散傅里叶变换,获取谐波信号真实的频谱,进而求得谐波参数。该算法的优势在于实现了频移思想在谐波分析上的应用,通过对加窗信号进行频域移动,消除非同步采样误差,将非同步问题同步化处理,同时避免了加窗插值算法等校正算法的修正过程,对幅值、相位、频率的估计有较简单的计算公式。算例分析验证了该方法的正确性,表明在噪声干扰下仍可获得很高的分析精度,尤其能改善相位估计的精度。

To exactly obtain the harmonic parameter in case of asynchronous sampling, and avoid the big error of phase estimation in the nonlinear interpolation, this paper proposed a novel window frequency shift algorithm to precisely estimate the harmonic parameters of power system. Using the derived frequency shift formula, the window signal could move the amount of frequency shift in the frequency domain. Then the measured frequency point was overlapped with its practical position. The harmonic parameters could be obtained through the shift signal spectrum correspondingly. The advantage of the novel algorithm is to realize the application of frequency shift in harmonic analysis, based on window signal shift in frequency domain. The asynchronous sampling problem was synchronized through moving the window signal to eliminate the asynchronous sampling error. At the same time, the algorithm avoided the correction process which exists in the interpolation algorithm. Moreover, estimations of amplitude, phase and frequency have more simple calculation formulas in the algorithm. The example results verify the correctness of the presented algorithm, and exhibit higher estimating precision, especially phase precision, compared with the window interpolation algorithm in case of noise jamming.