Method for measuring harmonic waves and interharmonic waves in electric power system by adopting spectrum estimation and chaology

Abstract

The invention provides a method for measuring harmonic waves and interharmonic waves in an electric power system by adopting spectrum estimation and chaology. The method provided by the invention mainly comprises the steps of: firstly, preliminarily measuring the quantity and the frequency of harmonic waves and interharmonic waves in waveform of the electric power system by adopting spectrum estimation; and then constructing a chaotic detection oscillator based on the measured frequencies of the harmonic waves and the interharmonic waves, and measuring the amplitude value of the chaotic detection oscillator, wherein in order to improve the detection precision, the largest Lyapunov exponent is applied as the basis for judgment of a critical condition for phase change of the chaotic detection oscillator in a chaotic state and a large-scale periodic state. According to the method provided by the invention, with higher frequency resolution and amplitude-value measurement accuracy, the frequencies and the amplitude values of the harmonic waves and the interharmonic waves in the electric power system can be highly efficiently measured, and the anti-jamming capability to background noises is strong.

Description

technical field [0001] The invention patent relates to a method for measuring harmonics and interharmonics of a power system using spectrum estimation and chaos theory. technical background [0002] The ideal voltage and current waveforms of the power system are sine waves, but due to the existence of various nonlinear elements in the power system, the voltage and current waveforms are distorted to generate harmonics and interharmonics (that is, signals with non-integer multiples of the fundamental frequency portion). The existence of harmonics (inter-harmonics) will not only increase the power loss of the grid, shorten the life of equipment, and malfunction of protection functions, but also cause partial parallel or series resonance of substations. In recent years, with the rapid development of power electronics technology, more and more harmonic source loads and devices have been widely used in power systems, industries, transportation and households. Harmonics have been ...

AI Technical Summary

Problems solved by technology

Fast Fourier transform is currently the most widely used harmonic measurement method, but this method has problems such as spectrum aliasing, fence effect and spectrum leakage, which make the measurement results unable to meet the requirements of the power system to a certain extent; The interpolation correction algorithm can improve the measurement accuracy and reduce the error caused by the fence effect, but the algorithm is often complicated, the programming is cumbersome, and the real-time performance is poor

The wavelet transform method proposed in recent years is adaptive to the signal and has good time-frequency localization characteristics. It has made a useful attempt in harmonic measurement, but wavelet transform is a linear transformation, and there are frequency band aliasing and spectrum leakage. The suppression of pulse interference is not ideal and the characteristics of transient power quality signals are gradually weakened with the increase of scale.

Although the harmonic detection method based on the theory of instantaneous reactive power has good real-time performance and can be realized by analog circuits, this method is only suitable for the occasions where the three-phase voltage waveform is symmetrical and has no distortion, and the current does not contain zero-sequence components.

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