A Method of Amplitude Calculation in Harmonic Analysis

Abstract

The invention discloses an amplitude solving method in harmonic analysis. The method comprises the following steps of discretizing a stable-state harmonic wave; performing windowing cutting on the discretized signal for obtaining the frequency spectrum of a windowing signal; obtaining an amplitude expression in a weighted form; solving a least value of a differential value of the amplitude to a frequency offset, thereby obtaining an optimal weight; on the condition of existence of an interference component, solving the frequency offset by means of a traditional ratio method; establishing an optimization problem according to the optimal weight and the frequency offset, and finally solving the amplitude. According to the method of the invention, a harmonic analysis amplitude optimal weight solving method is presented, and amplitude solving precision is improved.

Description

technical field [0001] The invention belongs to the field of power quality analysis and control, and in particular relates to a method for solving amplitude in harmonic analysis. Background technique [0002] The complex harmonics of the actual power grid contain rich inter-harmonic components, and the inter-harmonics have some characteristics different from the integer harmonics. If the FFT method is simply used, many problems will arise, which is also the biggest problem in the analysis of complex stationary harmonics. challenge. Compared with integer harmonics, interharmonics have the following characteristics: [0003] 1. The inter-harmonic frequency is not an integer multiple of the fundamental frequency, and it is even difficult to determine its approximate period, so it is basically impossible to achieve synchronous sampling of the inter-harmonic components; [0004] 2. The spectrum of inter-harmonics and integer harmonics / inter-harmonics may be very close, which re...

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Problems solved by technology

[0003] 1. The inter-harmonic frequency is not an integer multiple of the fundamental frequency, and it is even difficult to determine its approximate period, so it is basically impossible to achieve synchronous sampling of the inter-harmonic components;

[0004] 2. The spectrum of inter-harmonics and integer harmonics / inter-harmonics may be very close, which requires the analysis method of complex harmonics to have a high resolution;

[0005] 3. The strength of inter-harmonics is very weak, making it more susceptible to spectrum leakage, especially when inter-harmonics and integer harmonics are close together, this effect is more obvious

However, for inter-harmonics, since the frequency of inter-harmonics is not an integer multiple of the fundamental wave, it is difficult to achieve high-precision analysis of inter-harmonics even during synchronous sampling (for integer-order harmonics). ;

[0008] 2. Since the amplitude of the inter-harmonic is only a few percent or less of the integer harmonic, the spectrum leakage of the adjacent relatively strong harmonic component may lead to false inter-harmonic components or inter-harmonic spectra The peak disappears, and this phenomenon will be more prominent when the interharmonic and harmonic intervals are relatively small;

[0009] 3. The problem of resolution

[0010] Usually, the method of calculating the harmonic amplitude in the frequency domain is to calculate the frequency offset by the ratio method, and then use the peak value of the three spectral lines combined with the frequency offset to estimate the amplitude. In fact, there are infinitely many groups of such estimation methods. When the spectrum leakage is weak , the estimated results of these methods are not much different, but when the energy of the leakage component is large, arbitrary weighting may further enhance the adverse effect of leakage, which has not been noticed before

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