基于高阶傅里叶同步挤压变换与希尔伯特变换的次同步振荡分析

Analysis of Subsynchronous Oscillation Based on High-order Fourier Synchrosqueezed Transform and Hilbert Transform

针对次同步振荡分量提取存在噪声干扰和模态混叠问题,提出一种结合高阶傅里叶同步挤压变换(high-order Fourier synchrosqueezed transform,HFSST)与希尔伯特变换(Hilbert transform,HT)的次同步振荡分析方法。该方法在傅里叶同步挤压变换(Fourier syn-chrosqueezed transform,FSST)基础上,通过信号幅值和相位的高阶泰勒展开,定义一种调制算子对瞬时频率估计进行修正,从而提高信号时频分布的能量聚集程度和重构精度。然后,将所提方法应用于次同步振荡分析中,利用该方法对次同步振荡进行时频分析和模态分解,并与HT结合得到各分量振荡参数。通过仿真实验和实测数据分析,并与短时傅里叶变换(short-time Fourier transform,STFT)、重排方法(reassignment method,RM)、经验模态分解(empirical mode decomposition,EMD)等对比,结果表明:所提方法能抑制噪声干扰,得到更好的次同步振荡时频分布,同时可实现多分量的次同步振荡模态分解,准确辨识次同步振荡参数,对电力系统安全稳定运行具有一定的参考意义。

Aiming at the problems of noise interference and mode aliasing in the extraction of sub-synchronous oscillation com-ponents,a method of sub-synchronous oscillation analysis based on high-order Fourier synchrosqueezed transform(HFSST)is proposed.Based on the Fourier synchrosqueezed transform(FSST),a modulation operator is defined to modify the instantaneous frequency estimation through the high-order Taylor expansion of signal amplitude and phase,so as to improve the energy aggregation range and reconstruction accuracy of signal time-frequency distribution.Then,the proposed method is applied to the analysis of sub-synchronous oscillation.The time-frequency analysis and modal decomposition of the sub-synchronous oscillation are performed by using this method,and the oscillation parameters of each component are obtained by combining the method with Hilbert transform(HT).Through the simulation experiment and the analysis of the measured data,the results are compared with those of short-time Fourier transform(STFT),reassignment method(RM),and empirical mode decomposition(EMD).The results show that the proposed method can be adopted to suppress noise interference,obtain better time-frequency distribution of sub-synchronous oscillation,realize mul-ti-component mode decomposition of sub-synchronous oscillation,and accurately identify the parameters of sub-synchronous oscillation,which can provide some references for stable operation of power system.