A PMU Dynamic Data Processing Method Based on Feedback Iterative Frequency Tracking

Abstract

The invention discloses a PMU (Phasor Measurement Unit) dynamic data processing method based on feedback iterative frequency tracking. The method comprises the following steps: 1) a frequency value of a measurement system is obtained through a difference of a phase angle of a current cyclic wave phasor and the phase angle of a previous cyclic wave phasor, and the frequency value serves as the input frequency of a frequency tracking processing link after time delay correspondence is carried out, so that the tracking compensation correction of a system can be regulated immediately along with the change of the real-time frequency of the system so as to show high measurement precision in a dynamic environment which is changed along with time; and 2) on the basis of a DFT (Discrete Fourier Transform) equalization effect, a time scale of a measurement phasor is required to select the window center of a processing data window, so that a Lagrange interpolation and digital filter of frequency tracking is required as follow: the time scale point is taken as the center, and the processing data point numbers of two sides of the time scale point are completely equal. The method is still high in measurement precision when a power system is under dynamic conditions including frequency drift, amplitude oscillation, phase position oscillation and the like. The reliability of the data measurement and the state control of the system under an unstable state can be improved so as to be favorable for the digitized high-precision measurement and control of a power grid system to be safe and effective.

Description

technical field [0001] The invention belongs to the technical field of electric power systems and automation thereof, and in particular relates to a PMU dynamic data processing method based on feedback iterative frequency tracking. Background technique [0002] The fixed sampling rate of the data acquisition unit is 4kHz, and the sampling interval △T=250μs, which corresponds to working at the rated frequency f 0 = 50Hz power system, equivalent to N = 80 sampling points per cycle. When the system frequency shifts, the original sampling signal cannot constitute a complete cycle. The current frequency fre is obtained by software frequency measurement, and then the second-order Lagrange interpolation is performed on the original sampling points according to this frequency to fit the equiphase points corresponding to the power frequency signal 50Hz, and then these equiphase points are used for Fourier transform. In order to realize the synchronous correction of the sampling val...

AI Technical Summary

Problems solved by technology

[0009] It can be seen that the amplitude of the calculated phasor is the average value of the signal amplitude in the time window, and this effect will affect the dynamic measurement accuracy of the PMU

When the system signal changes linearly or approximately linearly, the average value of the phasor in the time window is equal to the actual phasor at the midpoint of the time window, that is, when the phasor time scale is selected as the midpoint of the time window, it is caused by the DFT averaging effect The error can be canceled out, such as image 3 When the signal changes nonlinearly, although the average value of the phasor in the time window cannot be consistent with the real value of the phasor at the midpoint of the time window, it can still be greatly reduced if the phasor time scale is selected at the midpoint of the time window, so that the phase The calculated value of the quantity is consistent with the true value of the signal to the greatest extent, such as Figure 4 shown

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