Software frequency tracking algorithm on basis of weighted double fitting

Abstract

The invention provides a software frequency tracking algorithm on the basis of the weighted double fitting, which comprises the following steps of: extracting sampling data of the maximum value of a sine wave and extracting sampling data of two points and two points, which are respectively positioned in front of and at the rear of the maximum value, in the same wave crest so as to obtain the sampling data of five points; substituting the data of the maximum value and the first two points into a fitted parabolic equation to obtain coordinate values of the position at which the maximum value of a first fitted parabola is positioned; substituting the data of the maximum value and the last two points into the fitted parabolic equation to obtain coordinate values of the position at which the maximum value of a second fitted parabola is positioned; according to the coordinate values obtained by the two fitted parabolas, calculating coordinate values of the positions at which the maximum values of a sampling value waveform are positioned in accordance with weighting factors; and calculating the coordinate value difference of two adjacent maximum values of the sampling value waveform to obtain the frequency of the sampling value waveform. The algorithm is simple and effective, has high response speed and high reliability, has low requirement on the sampling accuracy, is not influenced by the frequency variation and has high applicability.

Description

technical field [0001] The invention relates to the technical field of electric power, in particular to a software measurement method for grid frequency. Background technique [0002] The grid frequency is an important basis for indicating the working status of the power system, and it is also the main control parameter for the operation of the power system. The frequency quality directly affects the safety, stability and high-quality operation of the power system. Many algorithms for microcomputer protection are based on the basis related to the sampling frequency Therefore, it is necessary to monitor the frequency change of the system in real time, and obtain the accuracy of measurement and calculation according to the fluctuation of the system frequency. [0003] There are two main methods of frequency measurement: hardware measurement and software measurement: hardware measurement is to measure the transition width of the square wave after the AC signal is shaped into a ...

AI Technical Summary

Problems solved by technology

[0003] There are two main methods of frequency measurement: hardware measurement and software measurement: hardware measurement is to measure the transition width of the square wave after the AC signal is shaped into a square wave, but when the AC crosses zero, there is a linearity between the op amp and the opto-isolator. Area, it is easy to generate square wave jitter, causing frequency measurement error, and additional hardware frequency measurement circuit is required, occupying the external interrupt of the single chip microcomputer

The software measurement is based on the frequency calculation method of similar triangles, and uses the characteristics of the approximate straight line when the AC signal crosses zero to calculate the width of the two zero-crossing points. Small, large dispersion, unstable frequency measurement results

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