Research And Implementation Of Voltage Fluctuation And Flicker Detection Algorithm Based On Null Space Pursuit

With the development of power system, the phenomenon of voltage fluctuations and flicker in power grid has become more and more serious, because lots of high-power variable load and other nonlinear loads flood into the power grid. Thus, the detection of voltage fluctuation and flicker has become an important part to evaluate the power quality.The traditional detection methods of voltage fluctuations and flicker have a great of advantages when they deal with stable voltage fluctuation signal modulated by single frequency. However, the power signal in actuality is non-stationary and disturbed by noise and harmonic. For this type of voltage flicker signal, the traditional detection method is inadequate.According to above problems, a new method, proposed in this paper, is based on null space pursuit for voltage flicker extraction from voltage wave from of power systems. Null space pursuit, proposed in recent years, is an adaptive narrow-band signal analysis method based on a local singular linear operator. This algorithm can design a local singular linear operator, which depends on signal model, in order to decompose complicated signal. In this paper, it firstly designs a local singular linear operator according to the voltage flicker model; secondly, it separates a signal into narrow-band subcomponents by this adaptive operator; finally, it deals with these subcomponents by using different analysis methods. Thus, the pursuit of voltage fluctuation and flicker signal detection can be achieved. Here, numerical simulation experiments are carried out in the signal component flicker signal, flicker signal with multi-component flicker frequency, time-variant flicker frequency, impulses, white noises and harmonic components. Experimental results show that the proposed scheme performs better in terms of accurate extracting flicker components and suppressing noise. Moreover, the proposed method can accurately figure out the instantaneous frequency of the time-variant voltage signals.The main work of this paper is as follows:1) Researching the characteristics of null space pursuit algorithm and realization the process of different operator;2) Analyzing method of null space pursuit and design operator suitable for detecting voltage fluctuations and flicker;3) Decomposing the voltage signal by using the null space pursuit and different voltage flicker signal model are used to test the proposed method;4) Citing other application of null space pursuit.This paper will analyze the principle of null space pursuit algorithm and research application in the detection of voltage fluctuation and flicker field.