基于改进DFT和时域准同步的间谐波检测算法

快速傅里叶变换(FFT)在非同步采样时存在频谱泄漏和栅栏效应,由此产生的谐波与间谐波之间的频谱干扰会严重影响间谐波参数测量的准确度。为减小谐波与间谐波之间的频谱干扰,提出一种基于改进离散傅里叶变换(DFT)和时域准同步的间谐波检测算法,采用改进DFT算法精确估计基波频率,利用三次样条插值重构准同步采样序列,用FFT算法对单个周期重构序列进行处理,得到基波和谐波的参数,并将基波和谐波成分从重构序列中减去,再次用FFT算法和最大谱峰搜索法对剩余序列进行处理,确定每一个间谐波成分的参数。仿真结果表明,该算法不仅能提高频率分辨率,还可以有效排除谐波和间谐波的频谱干扰,且间谐波检测的准确度高、稳定性好、运算量小。

Inter-harmonic detection based on improved DFT and time-domain quasi-synchronization

The spectrum interference between harmonic and inter-harmonic due to the spectrum leakage and fence effect occurred in the FFT(Fast Fourier Transform) under asynchronous sampling condition may seriously affect the measuring accuracy of inter-harmonic parameters, aiming at which, an inter-harmonic detection algorithm based on improved DFT(Discrete Fourier Transform) and time-domain quasi-synchronization is proposed. It adopts the improved DFT algorithm to accurately estimate the fundamental frequency, uses the cubic spline interpolation to reconstruct the quasi-synchronous sampling sequence, applies the FFT to process the reconstructed quasi-synchronous sampling sequence for one cycle to obtain all parameters of fundamental and harmonics, subtracts the fundamental and harmonic components from the reconstructed quasi-synchronous sampling sequence, and applies the FFT again, together with the maximum peak search, to process the remaining sequence for determining the parameters of each inter-harmonic. Simulative results show that, the proposed algorithm not only improves the frequency resolution but also effectively eliminates the spectrum interference between harmonic and inter-harmonic. It has high inter-harmonic detection accuracy, good stability and small calculating load.