基于布莱克曼窗与窗宽比的S变换电能质量扰动特征提取

Feature Extraction Based on S-transform of Blackman Window and Window Ratio in Power Quality Disturbances

鉴于多分辨率广义S变换(MGST)时频分辨率低、且计算量大,提出了基于布莱克曼窗口与窗宽比的S变换(BST)及其快速算法(FBST)。BST采用了布莱克曼窗宽函数,相较于MGST采用的高斯窗口,有更好的时域分辨率,并且BST采用了窗宽比控制窗口宽度,摆脱了频率控制窗口宽度,在分析高频扰动,能够保持较好的时频分辨率,因此相较于MGST,BST更加适用于电能质量分析。首先,通过设置条件,测得最佳窗宽比,然后使用快速傅立叶变换得到频谱,再使用降噪消除噪声在频谱引起的尖峰,确定信号包含信息的频率范围,更好保留信息的完整性。然后根据确定的频率范围,计算对应频率范围内BST的频谱,进一步提高了频域分辨率。通过仿真与现场数据分析表明,FBST能够更加精确快速提取时频特征,满足工业精度与时效性需求。

In view of the low time-frequency resolution and large computational complexity of multiresolution generalized S-transform(MGST),an S-transform based on Blackman window and window width ratio(BST)and its fast algorithm(FBST)are proposed in this paper.The Blackman window width function is used in BST.Compared with the Gauss window used in MGST,BST has better time-domain resolution.Moreover,in the BST,the window width ratio is adopted to control the window width,which can get rid of the control of frequency over window width.In the analysis of high-frequency disturbances,BST can maintain better time-frequency resolution.Therefore,BST is more suitable for power quality analysis than MGST.Firstly,the optimum window width ratio is determined by setting conditions.Next,the spectrum is obtained by the Fast Fourier Transform.And then noise reduction is used to eliminate the peaks caused by noise in the spectrum,so as to determine the frequency range of the signal containing information and better preserve the integrity of the information.Lastly,according to the determined frequency range,the frequency spectrum of BST in corresponding frequency range is calculated,which further improves the resolution in frequency domain.The simulation and field data analysis show that FBST can be adopted to extract time-frequency characteristics more accurately.Therefore,FBST can meet the needs of industrial accuracy and timeliness.