Dynamic harmonic wave electric energy metering method based on multi-resolution short-time Fourier transformation

Abstract

The invention discloses a dynamic harmonic wave electric energy metering method based on multi-resolution short-time Fourier transformation. The method mainly comprises the steps of 1, conducting discrete sampling on a voltage signal and a current signal to obtain sampling sequence U (n) and I (n) of N points; 2, using a polynomial convolution window to weight the sampling sequence U (n) and I (n) and to conduct short short-time Fourier transformation to obtain a time frequency matrix FSTFT (g, j) of the signals; 3, using a least squares curve fitting method to solve all extreme points Km (g) in an amplitude matrix |FSTFT (g, j)|; 4, according to the extreme points Km (g), calculating the frequency, amplitude and phase of a fundamental wave and a harmonic wave and a duration set Tsm; 5, according to a power calculation formula, solving power of the fundamental wave and all harmonic waves, and then obtaining an electric energy metering result through a short-time Fourier transformation dynamic electric energy calculation formula. According to the dynamic harmonic wave electric energy metering method, based on the multi-resolution short-time Fourier transformation, a frequency domain characteristic and a time domain characteristic of the fundamental wave and the harmonic wave are analyzed, dynamic harmonic wave electric energy metering can be accurately conducted, and the requirement for modern electric power system dynamic electric energy metering is met.

Description

technical field [0001] The invention belongs to the field of power system electric energy measurement, and relates to a dynamic harmonic electric energy measurement method based on multi-resolution short-time Fourier transform. Background technique [0002] The continuous development of my country's economy has led to strong domestic power demand, the construction of long-distance and large-scale transmission networks, and the extensive use of various nonlinear loads. The problem of power quality is becoming more and more serious, the most serious of which is harmonics. The standard frequency of my country's power system is 50Hz, and the voltage and current are both standard sine waves of 50Hz. However, due to various interferences, in the actual power system, the voltage and current waveforms are always distorted to varying degrees, forming non-sinusoidal waveforms, that is Harmonics appear, and due to the changing power environment, the harmonics appear more time-domain cha...

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Problems solved by technology

[0003] Generally, when the harmonic problem is not serious, the measurement error of the fundamental wave electric energy is very small, which is allowed for the system; but when the harmonic problem is serious and the power consumption is large, only measuring the fundamental wave electric energy will give Electricity-related companies or users bring economic losses that cannot be ignored; in a nonlinear system, the total power consumed by the linear load is the sum of the fundamental power and harmonic power, and the energy absorbed by it is greater than the fundamental energy; The total power consumed is the difference between the absorbed fundamental wave power and the harmonic power sent to the grid. The absorbed energy is less than the fundamental wave energy entering the nonlinear load, and the dynamic harmonic time-frequency characteristics are complex, so it is difficult to accurately measure its time frequency parameter

Since the existing electric energy metering method does not consider the electric energy metering in the case of dynamic harmonics, it is difficult to meet the current electric energy measurement needs of the power system

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