Research on the Detection Method of Voltage Sag Characteristics

The correct detection of the voltage sag characteristics (its magnitude,duration and phase angle jump) is of great importance for the power quality evaluation and its mitigation.The existing methods including RMS voltage,peak voltage,fundamental voltage component and single phase average voltage are introduced.A fictitious three phase system is created from a reference single phase voltage by a 60 ° delay.With the d q conversion of voltages,two new methods,which are the average method of the d q conversion of instantaneous voltages and the low pass filter method of the d q conversion of instantaneous voltages,are proposed.The proposed methods can instantaneously quantify the phase angle jump,magnitude and duration for single phase voltage sag.By simulative calculation,the applicability of different methods is compared in detail.The result shows that the proposed methods possess the superiority of fast dynamic tracing performance and they are suitable for the analysis of voltage sag and the real time test of DVR.