Research On The Phase Angle Difference Between Phasors Measured By DFT Under The Influence Of Grid Frequency Vibration

With the continuous expansion of grid scale,large power system interconnection and large capacity,long distance transmission has become an important development trend of modern power system.Real-time monitoring of the grid,timely finding the hidden trouble,and effectively controlling the trouble prevent large-scale blackout accident emergence after the fault occurs,is an important and urgent task for power system researchers and workers.Accurate measurement of phasor angle is an important research content of power system,at present,based on GPS of generator power angle and bus voltage angle measurement research is one of the three frontier subject of power system.Aiming at the defect problems of PMU measurement of phasor angle,this paper theoretically deduced the DFT calculate phasor angle equation when the frequency of actual power grid is vibrating,proposed the solve method of tracking frequency when DFT algorithm calculate signal angle,analyzed the composition of DFT algorithm calculated phasor angle differences on different nodes point,proposed the corrected method of phasor angle differences on different nodes point use PMU proposed phasor angle data,thereby enhanced the use of PMU data value.The main work and achievements of this paper are listed as follows:1)According to the principle of phase angle measured by DFT,the expression of influence of frequency fluctuation on DFT phase angle error is deduced and analyzed;2)The characteristics of grid frequency tracking algorithm used in DFT are analyzed,using the phase angle and frequency data provided by the PMU phase angle data and using the one-time function fitting method,the expression of grid tracking frequency used in DFT is deduced and verified;3)According to the influence of frequency fluctuation on the phase angle difference of DFT measurement,a method to correct the error factor in DFT phase angle error correction is proposed,the correctness of the method is verified by the measured PMU phase angle data,this method realizes the accurate calculation of the phase angle difference between the voltage phasors at different nodes in the power grid,which is of great significance to improve the utilization value of PMU phase angle data.