The Research Of Voltage Sag Detection Method Based On Space Vector

Nowadays,with the fast development of national economy and technology,the extensive application of various nonlinear and impact loads in industrial production,the power quality problem becomes more and more serious.Voltage sag has ranked among the most concerned power quality problems because of its high frequency and high degree of harm in the field of power quality.Accurately and effectively detect the various characteristics of the voltage sag is the premise of the effective control of voltage sags.This paper describes the related concepts of voltage sags and the domestic and foreign research status for voltage sag detection problem,and then introduces the principle of space vector,and the application of space vector to detect the voltage sag.The main work of this paper is as follows:(1)The detection of voltage sag based on space vector is researched in this paper.In view of the traditional space vector method analysis of voltage sag can’t solve the voltage sag problem with phase angle jump,the space vector is constructed by applying Clarke Transformation and Euler’s Formula to the three-phase voltage signals.According to the trajectory shape of space vector in the complex plane,the voltage sag type and fault phase is determined.Through the ellipse parameters of space vector,the voltage phase angle jump value is calculated by solving equations.Then the original signal data is shifted according to the phase angle jump to eliminate the influence of phase angle jump.Finally,the depth of voltage sag can be quickly calculated.The simulation results show that the researched method can identify the fault type of voltage sag and calculate the voltage phase angle jump value and voltage sag depth.(2)A modified voltage sag detection method based on space vector is researched.The detection of voltage sag by space vector method requires a full cycle of three-phase voltage data.In order to improve the speed of calculation,an ellipse fitting method is combined with the space vector method.The equation of the space vector’s trajectory is calculated by applying Clarke Transformation and fast ellipse fitting method to the voltage signals of three different times of one voltage cycle.Based on the space vector trajectory,voltage sag is detected and the fault phase is identified.The voltage sag characteristics could be also calculated.The experimental results show that the researched method can identify the fault types of voltage sags and calculate the characteristic,with less data or computation.