基于特定频带的短时傅里叶分析

SHORT TIME FOURIER ANALYSIS BASED ON THE SPECIAL FREQUENCY COMPONENT

短时傅里叶分析(STFT)和小波分析部具有分析暂态谐波的能力,但两者部存在不足之处,STFT需要有一个合适的窗才能有满意的分析效果,小波分析不能得到单个的谐波频率和幅值。文中通过比较STFT和小波分析在电力系统暂态信号分析中的优缺点,结合两者的优点,提出了基于特定频带的STFT的方法。该方法利用多分辨率分析确定暂态故障发生的时刻和暂态信号的主要频率范围,在此基础上确定STFT的时窗中心和合适的窗宽,可有效地提高STFT的精度和效率,快速、准确地得到暂态信号中主要谐波频率分量的频率和幅值,通过MATLAB仿真证明了该方法的有效性。

The transient harmonics can be analyzed by short time Fourier transform (STFT) and wavelet transform, however there are defects in both of them. The former cannot have favorable result except for having a suitable window, and the later cannot acquire single harmonic frequency and its amplitude. After comparing the advantages and disadvantages between STFT and wavelet transform which used to analyze signal of transient harmonic in the power system, integrating their merits, a novel short time Fourier transform based on the special frequency component is proposed. In this method, multi-resolution analysis is first used to detect the fault time and determine main frequency domain of transient signal. After that, the central point and proper width for window of STFT is attained. So the accuracy and efficiency of STFT can be improved greatly, and frequency components and its amplitudes of transient signal can be obtained accurately and quickly. The validity has been testified through simulation using MATLAB.