Charging pile harmonic wave detection algorithm based on windowing interpolation FFT and wavelet packet

Abstract

The invention discloses a charging pile harmonic wave detection algorithm based on a windowing interpolation FFT and a wavelet packet; the algorithm comprises the following steps: windowing interpolation FFT transformation, using a Blair window and double-spectral line interpolation to carry out FFT transformation for an obtained signal, thus obtaining various harmonic waves in the signal; selecting a to-be analyzed frequency range, extracting harmonic waves having big influence on power grid characteristics, and neglecting harmonic waves with almost no influence, thus improving detection instantaneity; using the wavelet packet to decompose and reconstruct the selected frequency range , applying DB3 wavelet packet transformation on the signal, thus obtaining start-stop times of various generated harmonic waves. The algorithm can fast and accurately detect each harmonic wave of the electric vehicle charging pile, and can determine harmonic wave generation start-stop times.

Description

technical field [0001] The invention relates to an electric vehicle charging pile harmonic detection algorithm based on windowed interpolation FFT and wavelet packets. Background technique [0002] The charging mechanism inside the electric vehicle charging pile is a nonlinear component. When the charging device is running, it will cause a decrease in system power factor and harmonic pollution in the power system. Moreover, as an electric load, the charging behavior of electric vehicles is random and intermittent. . Therefore, it usually reduces the efficiency of equipment, affects the normal operation of electrical equipment, and even causes local resonance of the power grid, which amplifies harmonics and aggravates harm; leads to malfunctions of relay protection and automatic devices; and interferes with communication systems. In particular, harmonic pollution is the most serious hazard in the power system, so it is imminent to propose an excellent harmonic detection algo...

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Problems solved by technology

The analog filter method has high requirements on the parameters of circuit components, and the accuracy is relatively low; the detection method based on instantaneous reactive power has a large error in the detection results, and the detection algorithm is complex and difficult to implement; based on Fourier transform and its improved method There are certain spectrum leakage phenomenon and fence effect in the detection, and more importantly, it is impossible to locate the time when the transient signal occurs and ends; the detection method based on wavelet transform only decomposes the low-frequency band of the signal, resulting in relatively low resolution in the high-frequency band. Low, reducing the detection accuracy of higher harmonics

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