Reserach On The Method Of Correcting Voltage Phase Angle Difference Error In Power Grid Using Recorded Data

With the continuous development of electric power construction and regional interconnected power grid,the scale of power grid is becoming larger and larger.In order to ensure the safe and stable operation of the power system,it is necessary to monitor the running of the growing power grid in real time.As the global positioning system(GPS)is widely applied in the power system,it is possible to synchronously measure the current and voltage angle at different nodes in the power grid.Then the phase angle difference of voltage phase at different grid nodes could be calculated.The accurate measurement of the phase angle difference between voltage phase is of great value to the monitoring of the stable operation state of the power grid and rapid calculation.Since the introduction of the WAMS system in China in 1993,China has built the largest WAMS system in the world,DFT algorithm is widely applied in it,however,not all of the current PMU are modified for frequency offset.In this paper,the phase angle measurement error of traditional DFT algorithm in frequency offset is analyzed.A method is presented to calculate phase angle difference between two points by using correlation function with recorded data.And the results are verified by the calculation results of the line parameter model.In the end,a method is proposed to calculate the phase angle difference in power grid for fast real-time detection.The main work and results of this paper are as follows:(1)According to the principle of measuring the phase angle by DFT,error of phase angle difference of traditional DFT measurement under the frequency offset is analyzed and deduced.(2)In order to analyze the error of the phase angle difference measured by current installed PMU.Taking the Qinghai power grid in Western China as an example,the voltage phase angle difference at both ends of the line is calculated by PMU measurement data,and the voltage phase angle difference at both ends of the line is calculated by using the cross correlation function method with the recorded wave data.Finally,the results of the recorded wave method are verified by using the line parameter model.And,the cross correlation function method is used to modify the voltage angle difference measured by PMU.(3)In order to real-time detect the voltage phase angle difference between two points in the PMU calculation in power grid,a peak time method is proposed to calculate the voltage phase angle difference in the power grid.The measured data show that the peak time method has a series of advantages,such as simple principle,small amount of operation and so on.