Voltage Dips Feature Extraction And Disturbance Cause Analysis

In recent years, much attention has been given to the power quality problems by power incorporations and customers gradually because of the significant development of the computer technology and industry automation. Voltage sag is a particular power quality disturbance; it has become a key question of the power quality research for its occurrence frequency, influence area and damage. In this circumstances, four problems, i.e. the cause of the voltage sag, extraction of the voltage sag characters, voltage sag cause identifying and power quality monitor have been discussed in this paper. The main achievements are summarized as follows: This paper analyzes the mechanism of the sag causations and summarizes the characters of the sag by the dissimilar causation. This paper uses kalman filter to extract the sag characters. To accelerate the response of the high-order filter,this paper presents a fundamental component coefficient amending method,so that high-order filter can be more adapt to sag characters extracting . Then this paper validates the filter method by comparing the real record analysis output with the mechanism analysis output. This paper analyzes the filter output further and computes the three-phase voltage unbalance factor, harmonics distortion factor and voltage sag ending amplitude information to identify the cause of the sags. Then to utilize the monitor data more efficiently and reduce the sag monitor hardwires cost, this paper puts the sags caused by system fault into five kinds and analyzes the spreading of the sags in the power system. This paper introduces a new concept, virtual instrument (VI), into power quality monitor. Firstly, it studies the instrument hardware. Secondly, it analyzes the software's fundamental functions and characters. Finally, it introduces the workflow of the data acquisition, data storing and data processing; offers two solutions for the cooperation of the LabVIEW environment and data acquisition card produced by domestic manufacturer by CIN node in LabVIEW or dynamic link library (DLL).