Research On Technology Of The Adaptive Current Protection Based On Wavelet

At the present stage, low voltage distribution network in power system protection is themain current protection. With the acceleration of China’s urbanization, the rapid increase inthe size of low-voltage power grid, so the current protection on the basis of traditional controltheory and other related fields, and inspired by the theory, related scholars have put forth theconcept of adaptive current protection, adaptive current protection refers to the protectiondevice according to the power system operating mode changes and fault status change inreal-time protection settings.Two key problems are need to be solved to realize adaptive current protection: Real-timemonitoring system operation and fast determine the faults and the fault moment. Real-timemonitoring system operation and fast determining the faults and the fault moment all need tocalculate accurately the steady-state phase amplitude. Full-wave Fourier algorithm and theimproved Fourier algorithm which their data window is long and have high precision ofcalculation, are now commonly used. But when the power network frequency is instability orcalculation of short-circuit the initial stage of the transition process containing aperiodiccomponent and the rich harmonics, Full-wave Fourier algorithm and the improved Fourieralgorithm also can appear bigger error. In order to solve this problem, this paper presents theapplication of wavelet algorithm to achieve steady amplitude of phase extraction and faultdetection scheme.This paper briefly introduces the basic concept of power system fault components andextraction method;Introduces the principle of adaptive current protection and its relatedcalculation problem, and compares it with the traditional current protection; proposed basedon two interphase current difference auto-adapted electric current protection plan.In this paper, I give a detailed account of the Morlet complex wavelet and introduce howto calculate wavelet phase magnitude with Morlet complex. In order to improve thecomputing speed, This paper introduces a kind of differential filter plus whole week Morletcomplex wavelet to calculate the amplitude of phase. This paper presents application ofDmeyer wavelet to determine the fault time. These algorithms and scheme has beensimulation test with PSCAD and MATLAB and other related software. The results of simulation show that the wavelet algorithm is of high accuracy and can satisfy adaptiveprotection’s need, so it is highly valuable for engineering practice.Finally, we test the software part designed by us with Xi’an expedition company YZ600hardware platform and related test equipment. The experimental results show that theadaptive current protection based on complex wavelet can largely improve the line protectionrange.