The Research On The Detection Of Transient Power Quality

Electrical energy plays an important role in the life and industrial production.However,with the increase of nonlinear impact load in grid,it results a variety of power quality problems.Power quality can be divided into steady state power quality and transient power quality problem.Because the transient power quality has the characteristics of short duration and great harm,it makes the research of the transient power become more difficult.The paper introduces several common single transient power quality and mixed disturbances.By analyzing the characteristic of the disturbance signals,the signals are classified as single-frequency disturbances and multi-frequency disturbances.Single-frequency disturbances includes voltage sag,voltage sag,voltage interruption and pulse transient;Multi-frequency disturbances includes oscillation transient,the mixture of voltage sag(temporary rise,interrupt)and short time harmonics,the mixing of pulse transient and short time harmonics;In the algorithm analysis,the S transform and Hilbert Huang transform(HHT)are studied.Because the S transform can not meet the requirement of time resolution and frequency resolution,the generalized S transform is proposed.That is to say,by increasing the frequency adjustment ?f=?f+? coefficient to enhance the adaptability;Because HHT has the end effect and the mode mixing phenomenon,the improved HHT algorithm is proposed.That is to say,by increasing the Gauss white noise to reduce the error of HHT.The single-frequency disturbance signals are detected by the generalized S transform directly.In addition,the composite of two improved algorithms are proposed for the multi-frequency disturbances.First the multi-frequency signals do HHT decomposition into some single frequency signals,then these single-frequency signals are analyzed by generalized S transform,which can both reduce the computation and improve the detection accuracy.Through the MATLAB to establish a mathematical model of the disturbance,and extract their detection of the basic frequency curve,contour map and other information.The simulation results verify the effectiveness and feasibility of the proposed algorithm in this paper.