A Multi-Frequency Subharmonic Detecting Method
A technology of sub-harmonics and detection methods, applied in spectrum analysis, measurement devices, measurement of electrical variables, etc., can solve problems such as large amount of calculation, iteration error, etc., achieve simple algorithm, shorten calculation time, and meet the requirements of control frequency Effect
Inactive Publication Date: 2019-02-01
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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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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The invention discloses a multi-frequency subharmonic detection method, which collects the grid voltage through an AD sampling link, and then uses a phase-locked loop to lock the phase of the grid voltage to obtain the grid voltage frequency fpll and phase θ, and then collects the load current iL, Subtract it from the output of the subharmonic detection system, and then input the resulting difference to the multi-frequency switch for grouping, and then output the signals of different groups through different switching frequencies; finally, output the multi-frequency switch The signal passes through the nth harmonic bandpass filter to obtain the nth harmonic of the detected load current iL. Through the method of the invention, it is possible to realize the step-by-step detection and extraction of each harmonic of the detected load current iL under the premise of reducing the calculation amount of the high-frequency control system.
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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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