Research Of Hybrid Active Power Filter Based On Wavelet Analysis

Economic development, the power should take the lead. The electricity has already become one of the important energy of the contemporary society, and supporting the development of industrial, agricultural, people’s quality of life and the national defense technology, we can say that the development of various fields is inseparable from power. In recent years, with the development of high-voltage direct current transmission, electrified rail transportation and even everyday office use electrical appliances promote the wide application of new power electronic devices, these non-linear load, impact and imbalance of power consumption characteristics, resulting in a large number of harmonic wave into the power grid, causing serious pollution to the grid. Harmonic has become a major factor in the impact of power quality, and effectively measuring and suppressing harmonic has become very important to improve power quality. Harmonic detection and suppression are two important aspects of the harmonic problem, and they are the starting point of the analysis of harmonic problems.This paper first introduces the basic concepts of power system harmonics, the causes of grid harmonics and its harm, the traditional harmonic measurement method and its shortcomings. Compare the current used by the harmonic detection method, starting from the Fourier harmonics measurement method which can not localize in time-frequency field simultaneous, leads to the wavelet transform theory, with emphasis on the wavelet transform theory, explores the continuous wavelet transform, discrete wavelet transform, wavelet packet transform, wavelet theory in several important transform method, analyzing the time-frequency characteristics of these types of wavelet transform. Harmonic suppression method, the first analysis of the current power system common filter characteristics, comparing different types of passive filters and active filters to explore the parameters of the passive filter design method, the main circuit and current control methods of the active power filter, compares the types of filter characteristics, discuss the establishment of a hybrid power filter ,and then gives the simulation results based on MATLAB simulation by SIMULINK to show this method is effective.In this thesis, the work done as follows:(1) The principle of the wavelet transform and its applications in harmonic analysis, comparison of several commonly used harmonic detection method. Gives an argument based on the MATLAB simulation software use cases. Simulation made by using the wavelet toolbox in MATLAB software modules, and to determine the effectiveness of the db20 for the generating function of one-dimensional discrete wavelet transform in the harmonic detection.(2) Analysis of the classification of commonly used passive filters and active filters in power system topology and circuit parameters design method to compare the passive filter alone series and shunt active power filter, and hybrid power filter in dealing with the differences of the grid harmonics. Deep study the main circuit topology of the hybrid power filter design parameters.(3) Design of a hybrid active power filter, the structure of the filter and passive filter parameter design method and the active filter circuit, and discuss its mathematical model.(4) Four sets based on the SIMULINK module of MATLAB software simulation examples are the first group of passive filter used alone, the joint action of the first group and second group of passive filters, active filter used alone and two the group of passive filters and active filters to be put into use. The simulation results show that low power waveform and higher harmonics have been suppressed, the waveform overall aberration rate was significantly lower, show that the design of hybrid power filter is effective to deal with harmonic.