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Multi-frequency fractional harmonic detection method

A technology of fractional harmonics and detection methods, applied in spectrum analysis, measuring devices, measuring electrical variables, etc., can solve problems such as iterative errors and large calculations, and achieve the effects of shortening calculation time, simple algorithms, and reducing calculations

Inactive Publication Date: 2017-03-08
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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Problems solved by technology

The harmonic detection method based on Fourier transform can realize harmonic detection in stages, which is convenient to use, but there is a delay of a fundamental wave cycle, which belongs to the non-real-time detection method, and the Fourier transform is used in the algorithm, and the calculation amount is relatively large. Large; the iterative Fourier transform method is superior to other Fourier transform methods in terms of dynamic response speed, but the detection of each harmonic requires a large amount of storage space to store the signal value within one cycle of the harmonic, and there is an iterative error problem

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[0055] For the convenience of description, this embodiment takes the detection of each harmonic of the three-phase load current as an example, and describes the control frequency f s =10KHz, extract the load current i L Specific methods for harmonic signals of odd numbers and not multiples of 3 (that is, 5, 7, 11, 13, ..., 47, 49 times):

[0056] In this example, if figure 1 As shown, a kind of multi-frequency fractional harmonic detection method of the present invention comprises the following steps:

[0057] (1), to grid voltage U g Carry out AD sampling, and then use the phase-locked loop to measure the sampled grid voltage u a u b u c Perform phase-locking to obtain the grid frequency f pll ,Such as figure 2 Shown:

[0058] (1.1), the three-phase grid voltage u is transformed by Clarke transformation a u b u c Transform to the α-axis and β-axis components in the stationary reference frame:

[0059] u αβ =T abc-αβ u abc (1);

[0060] Among them, u αβ =[u ...

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Abstract

The invention discloses a multi-frequency fractional harmonic detection method. The method is characterized in that through an AD sampling link, collecting a power grid voltage, using a phase-locked loop to carry out phase lock on the power grid voltage so as to acquire a power grid voltage frequency fpll and a phase theta; then collecting a load current iL, carrying out subtraction operation on the load current iL and an output quantity of a fractional harmonic detection system, inputting a difference value into a multi-frequency switch so as to carry out grouping and then outputting different groups of signals through different switch frequencies; and finally, making the signal output by the multi-frequency switch pass through a n-times harmonic band-pass filter, and acquiring n-times harmonics of the detected load current iL. Through the method of the invention, under the condition that a calculated amount of a high frequency control system is reduced, fractional detection extraction of each harmonic of the detected load current iL can be realized.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and more specifically relates to a multi-frequency fractional harmonic detection method. Background technique [0002] With the rapid development of power systems, nonlinear loads have been applied on a large scale, and they generate a large amount of reactive and harmonic currents in the grid. The injection of harmonic current will cause serious distortion of grid current, affect power quality, reduce grid efficiency and threaten the safe operation of electrical system. Therefore, harmonic detection and suppression has great practical and economic significance. [0003] At present, the harmonic detection methods in the power system can be mainly divided into two categories: detection methods based on frequency domain and detection methods based on time domain. Frequency-domain harmonic detection methods mainly include Fast Fourier Transform (FFT), Discrete Fourier Transform (DFT) and...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R23/165
CPCG01R23/165
Inventor 谢川董振华张刚郑宏邹见效徐红兵
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA
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