Novel harmonic high-precision detection method

Abstract

The invention discloses a novel harmonic high-precision detection method. The method comprises: establishing a novel time-frequency filter, restraining frequency of a minus semiaxis by Hilbert transformation, and detecting frequency, amplitude, and phase positions of each subharmonic and inter-harmonics by a time domain convolution method in a high precision manner. From theoretical analysis basis and calculation formula derivation of the method, the method prevents Fourier (FFT) region spectrum leakage, picket fence effect, and non-integral subwave phenomenon. Results of experiment simulation shows that the time domain filtering convolution method is flexible in design and realization, and convenient in engineering real-time realization, and overcomes influence of fundamental frequency on harmonic analysis, and detection precision of frequency, amplitude values, and initial phases of signals including multiple harmonics and inter-harmonics. Frequency, amplitude, and phase of a voltage flicker signal can be obtained by a signal converting equation. For flicker signals polluted by the inter-harmonics, detection results are not influenced.

Description

technical field [0001] The invention belongs to the technical field of signal processing, in particular to a novel harmonic high-precision detection method. Background technique [0002] With the rapid development of my country's industrialization process, the installed capacity of the power grid continues to increase, and the use of power electronic components in the power grid is also increasing, resulting in a large number of harmonic currents injected into the power grid, resulting in sine wave distortion and a decline in power quality. Some important equipment of the system have had a major impact; it has also caused serious harm to the majority of users; at present, harmonics, electromagnetic interference, and power factor reduction are listed as the three major public hazards of the power system; harmonic hazards of the power system: [0003] (1) Harmonics will cause additional losses to power equipment in the public grid, reducing the efficiency of power generation, t...

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Problems solved by technology

A large number of third harmonics flowing through the neutral line will overheat the line, and may even cause a fire if it is serious;

[0004](2) Harmonics will affect the normal operation of electrical equipment, causing mechanical vibration and noise faults in the motor, severe local overheating of transformers, overheating of capacitors, cables and other equipment, The insulation part is aging and deteriorating, and the life of the equipment is shortened until it is finally damaged;

[0005](3) Harmonics will cause grid resonance, which may amplify the harmonic current several times or even dozens of times, and pose a major threat to the system, especially for capacitors and The reactor connected in series with it will often burn out due to grid resonance;

[0006](4) Harmonics will cause relay protection and automatic devices to malfunction, resulting in unnecessary interruption and loss of power supply;

[0007](5) Harmonics will cause inaccurate measurement of electrical measuring instruments, resulting in measurement errors, which will bring direct economic losses to power supply departments or power users;

[0008](6) Harmonics will interfere with the communication system near the equipment, which may cause noise, reduce communication quality and cause information loss, making the communication system unable to work normally ;

[0009](7) Harmonics will interfere with the normal operation of computer systems and other electronic equipment, resulting in data loss or crashes;

[0010](8) Harmonics will affect the performance of radio transmission systems, radar systems, nuclear magnetic resonance and other equipment, causing noise interference and image disorder

[0011]The high-precision analysis of power harmonics is of great significance to electric energy metering, harmonic power flow calculation, equipment network detection, power system harmonic compensation and suppression, etc.; due to asynchronous Sampling and data truncation, using the fast Fourier transform (FFT) algorithm for harmonic analysis produces spectrum leakage and fence effects, which affect the accuracy of harmonic analysis;

[0012]In order to reduce this kind of error, domestic and foreign scholars have proposed based on rectangular window, Hanning window, Hamming window], Blackman window, Blackman- Harris window, Kaiser window, and various improved window ] signal window interpolation FFT analysis algorithms can alleviate the spectrum leakage and fence effect problems encountered when FFT is applied alone, and improve the accuracy of harmonic parameters. Detection accuracy, but cannot detect inter-harmonics near integer harmonics; use bispectral ] or multi-spectral interpolation FFT algorithm based on high-order cosine combination window to estimate fundamental and harmonic parameters When the high-order equation needs to be solved, the calculation is complicated; the continuous wavelet transform can realize the detection of inter / sub-harmonic, but the wavelet functions of different scales interfere with each other in the frequency domain. When the detected signal contains harmonics with similar frequencies The detection method will fail when there are no components; the Prony method is an effective method for harmonic and interharmonic analysis and modeling, and can accurately estimate the frequency, amplitude and phase angle of each sinusoidal component, but it needs to solve two sets of odd-order equations and a Polynomial, high computational complexity and sensitive to noise; there are other methods, or the frequency resolution is limited, or the amount of calculation is large, and there are limitations in specific applications

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