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Harmonic analysis method

A technology of harmonic analysis and estimation value, applied in the field of harmonic analysis, it can solve the problems of inaccurate harmonic data and high hardware cost, and achieve the effect of reducing the amount of calculation, improving the calculation speed, and reducing the RAM overhead.

Active Publication Date: 2022-08-05
YANTAI DONGFANG WISDOM ELECTRIC
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Problems solved by technology

[0008] The present invention proposes a harmonic analysis method, the purpose of which is to: (1) break through the restriction that the number of data points of the conventional FFT method must be an integer power of 2; (3) Overcome the problem of high hardware cost caused by the use of hardware frequency tracking components; (4) Avoid electric energy measurement errors caused by changes in sampling intervals; (5) Reduce the amount of calculation and improve calculation efficiency , easy to implement

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Embodiment Construction

[0064] Describe the technical scheme of the present invention in detail below in conjunction with accompanying drawing:

[0065] like figure 1 , a harmonic analysis method with a fixed sampling frequency f s Sampling the grid signal also includes the following steps:

[0066] Step 1. Calculate the estimated value of the operating frequency of the signal according to the sampled signal.

[0067] In this embodiment, the zero-crossing method is used to calculate the estimated value of the operating frequency:

[0068] Step 1-1. Pass the sampled signal through a low-pass filter to obtain a signal containing only the fundamental wave;

[0069] Step 1-2, initialize the zero-crossing point count Cnt-zero to 0, and the elapsed time value T-zero to 0;

[0070] Step 1-3, traverse each sampling point until the zero-crossing point count Cnt-zero reaches the required number of points: if the value of the current sampling point is greater than 0 and the value of the previous sampling po...

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Abstract

The invention discloses a harmonic analysis method, which is used for sampling at a fixed sampling frequency and comprises the following steps of: 1, calculating a working frequency estimated value of a signal according to a sampled signal; 2, dynamically adjusting the length of a sampling window according to the estimated value of the working frequency; 3, calculating an initial angle vector and an increment angle vector according to the working frequency estimated value, the sampling frequency, the sampling window length and the harmonic analysis range; step 4, caching a section of sampling signal as a calculation input signal, wherein the length of the calculation input signal is equal to that of the initial angle vector; and calculating the harmonic content in the harmonic analysis range according to the calculation input signal, the initial angle vector and the incremental angle vector. The method breaks through the limitation of the number of data points of a conventional FFT method, solves the problem that the conventional method is inaccurate in result under the condition of frequency offset, and also has the advantages of low hardware cost, no influence on electric energy metering, low operand, high calculation speed, easiness in engineering implementation and the like.

Description

technical field [0001] The invention relates to a method for analyzing harmonics in a power grid. Background technique [0002] The harmonic information of the power grid is an important data to measure the power supply quality of the power grid. The conventional harmonic analysis method is to collect several integer cycles of data at a fixed sampling interval, and then perform Fast Fourier Transform (FFT), and calculate the harmonic content according to the transformed spectral line information. Conventional FFT methods have the following drawbacks: [0003] 1. The number of data points for each FFT must be an integer power of 2, such as 512, 1024, etc. According to IEC61000-4-30, it is recommended to accumulate 10 cycles of data for the first harmonic analysis. If the number of accumulated points is 1024, then the number of sampling points per cycle is 102.4 points, which puts forward higher requirements for the sampling device. [0004] 2. In the case of frequency offs...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R23/16G01R23/165
CPCG01R23/16G01R23/165Y02E40/40
Inventor 胡春华刘笑菲邓文栋刘志军伍韬张玉猛尹西科姜文浩贺岩贾斌
Owner YANTAI DONGFANG WISDOM ELECTRIC
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