摘要
含有变频器的风力发电机组在并网发电时会给电力系统注入时变谐波。快速傅里叶变换(FFT)是目前谐波分析的主要方法,但是它不适合处理非平稳时变信号。提出利用小波包变换(WPT)的方法对电流信号进行分析。基于Daubechies小波,采用适当的采集频率和小波包分解树,使谐波频率落在小波包频带并利用其小波包系数重构出各次谐波。可以实现信号频带的均匀划分,能够更好地提取信号的时频特性,还具有分辨非平稳时变谐波的能力。仿真结果显示小波包变换的谐波分析能力更好,能根据要求分离任意次谐波。
The wind turbine containing the inverter under grid connected mode will inject time-varying harmonic current into the power system. The fast Fourier transform （FFT） is currently the main method for the electrical harmonic analysis while it is not suitable for analyzing time-varying signals. A novel method for analyzing the current signal based on the wavelet packet transform is proposed, Based on the db wavelet, this method makes use of appropriate sampling frequency and the tree of the wavelet packet decomposition. The harmonic frequency tested will locate in the frequency band and the harmonic is reconstructed by using the wavelet packet coefficient. Using wavelet packet transform, the frequency band of signal can be uniformly divided and the signal features in time domain and frequency domain are extracted better. WPT also has the ability to distinguish non-stationary time-varying harmonic possesses for harmonic analysis. The result of the simulation shows that the wavelet packet transform is more effective in the analysis of the harmonic. WPT can even extract any times of harmonics.
出处
《电力系统及其自动化学报》
CSCD
北大核心
2013年第3期162-166,共5页
Proceedings of the CSU-EPSA
关键词
双馈风力发电机组
傅里叶变换
小波包变换
谐波分析
频率
doubly-fed wind turbine generator system
Fourier transform
wavelet packet transform
harmonic analy-sis
frequency
