The Application Study Of The Hilbert-Huang Transform In The Power System Protection

With the rapid development of China's national economy in recent years, the requirements on the power system are also increasing. The overall development trend of China power grid becomes into a large-capacity, long-distance, high-voltage situation. The characteristic of large transmission power and high voltage has put out higher requirement of the transient stability of power systems.An important solution of enhancing the transmission power of transmission lines and enhancing the transient stability is rapid removal of fault. Therefore,the high-speed even the ultra high-speed transient-based protection for transmission line based on transient fault signals becomes a research focus of power system protection in recent years.In this paper, on the basis of the transmission line fault analysis and transient signal characteristics of the frequency characteristics of system components and their influence on the transient signal,using the absorption of high frequency signal by the transmission line boundary consist of the bus stray capacitance and traps and other components,we proposed the differences characteristics between the inside and outside fault of the EHV transmission line based on transient fault high frequency signals.Further,the FFT found there are significant differences between the inside and outside transient fault signals in high frequency 100kHz-500kHz.By the EMD with HHT which is created by the N.E.Huang and others, complex signal can be decomposed into a number of IMF's group. However, there are many problems in the application of EMD method, which affects its promotion in the practical application. In this paper, the combination of multi-resolution analysis notion of wavelet theory,we used MEMD,it is a method based on multi-resolution analysis,solved the mode mixing and too long computing time and other issues of EMD.Finally, combining the theoretical analysis of the previous chapters, by calculating the ration of marginal spectrum energy density between the low and high frequency fault signal,we proposed transient current protection algorithm based on Hilbert marginal spectrum energy density. A large number of simulation showed the basic criterion is not affected by the different fault type, fault location, fault time and the transition resistance,verified the correctness of the protection algorithm.