Time-frequency analysis for transient responses of power system faults

• Main Authors: Meng-Liang Chen, 陳孟良
• Other Authors: Pei-Hwa Huang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/25930912418186123658

碩士 === 國立臺灣海洋大學 === 電機工程學系 === 96 === One of the main purposes of signal analyses is to describe the characteristics of signals, of which the most essential variables are time and frequency. The two main kinds of conventional signal analysis are time-domain analysis and frequency-domain analysis. However, it is usually the frequency that changes with time. With time-frequency analysis, it could not only show the change of frequency and amplitude with respect to time simultaneously but also discern the overall attribute and structure of the signal. In this thesis, Hilbert-Huang transform (HHT) is applied to analyze the transient responses of power system faults. The transient responses resulted by power system faults are essentially non-linear and non-stationary signals, and HHT is a suitable method for dealing with such kind of signals. The method of HHT consists mainly of the empirical mode decomposition (EMD) and the Hilbert transform. By means of EMD, the encountered signals can be decomposed into a collection of intrinsic mode functions (IMFs). And followed by the Hilbert transform the instantaneous frequency and instantaneous amplitude of each IMF can be obtained. The energy variation of voltage signals associated with the transient responses of power system faults is investigated, and then the type of fault signals in power system can be identified. Besides, in view of visualization, the methods of HHT and wavelet transform are correlated for depicting the time-frequency graph in which the frequency band of the signal of power fault responses can be clearly demonstrated.