Location And Recognition Of The Voltage Sag Source Based On The Distribution System

With the continuous development of science and technology, the requirements of power users for power quality continue to increase. As one of the major power quality problems, voltage sag bring serious harm to power systerms and electrical equipments. In this paper, techniques of location and recognition of the voltage sag source are studied, the method based on disturbance power and disturbance energy combined with direct parameter method, and the method based on wavelet transform are propsed. Which are important for analysis and management of power quality.In this paper, the existing methods of location and recognition of the voltage sag source are discussed in detail and compared. A distribution network voltage sag disturbance source model is build based on MATLAB/SIMULINK, and several common disturbance source are analyzed in and compared in different aspects to select the most recognizable feature to make the location and recognition of voltage sag disturbance source.In the practical application, the key to locate the voltage sag source is to determine the position of the source relative to the monitoring device, which is located upstream or downstream. And the recognition of the source is mainly targeted at the downstream, that is, the areas of jurisdiction of the substation. In this context, with the analysis and compare results of the voltage sag source based on the model, characteristic quantities of various types of disturbance source are extracted. Then the method based on disturbance power and disturbance energy combined with rms voltage direct parameter method is proposed. The location relative to the monitoring sites is determined first, and then recognition.In the distribution network, the location of the monitoring device is known, but the location of voltage sag is unknown. So the acquisition of the fault signal at the failure point is diffcult to achieve, resulting the characteristic of the signal is not obvious. For this reason, the method based on the Daubechies4 wavelet is proposed, which has good locality in the time domain and frequency domain, and sensitive to irregular signals. Based on the analysis of the decomposition result, the features are extracted, and the identification rules are build, then the recognition of voltage sag source is achieved.Finally, the two methods are compared, and their own characteristics are obtained. In this paper, from the view of practical point, according to the principles of simple, reliable, and easy to implement, the method based on disturbance power and disturbance energy combined with rms voltage direct parameter method, and the method based on wavelet transform are propsed.