基于希尔伯特-黄变换的电力系统谐波分析

准确的谐波分析对电力系统稳定具有重要意义。为克服FFT方法与小波分析方法的缺点，提出将希尔伯特-黄变换(Hilbert-Huang transform, HHT)用于谐波分析。将谐波信号进行经验模态分解(empirical mode decomposition, EMD)，得到一系列经验模态函数(intrinsic mode function, IMF)。由于不同的IMF对应不同的谐波分量，通过对每个IMF分量进行Hilbert变换(HT)及最小二乘拟和，最终可以得到各次谐波的幅值、频率和相位，从而实现电力系统谐波的准确分析。在经验模态分解过程中，采用了分段三次Hermite插值，并通过添加极值的方法减轻边缘效应的影响，使谐波分析能够更准确。仿真表明，Hermite插值比三次样条插值对谐波分析更具优势。该方法分析电力系统谐波精度高，能够取得满意的效果。

Power System Harmonic Analysis Based on Hilbert-Huang Transform

To analyze harmonic accurately is significant to the stability of power system. HHT (Hilbert-Huang Transform) is adopted to analyze harmonic in order to overcome the shortcoming of FFT method and wavelet analysis method. The power quality signals are decomposed by empirical mode decomposition (EMD) method, and then a series of intrinsic mode function (IMF) are obtained. Owing to different IMFs correspond to different harmonic, all harmonic' amplitudes, frequencies and phases can be achieved via Hilbert transform (HT) plus Least Square fitting, to realize accurate analysis of power system harmonic. During the procession of EMD, piecewise Cubic Hermite Interpolating Polynomial is employed. Furthermore, in order to alleviate edge effects the method of adding extremes is used. Simulation indicates that Hermite interpolation is superior to the cubic spline interpolation in harmonic analysis. The method has high precise and is satisfied to analysis power system harmonic.