Harmonic detector principle and method - Database & Sql Blog Articles

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1. Measurement using analog band stop or band pass filter

This is the earliest method of harmonic measurement, which has the advantages of low circuit cost, simple structure, easy control and low output impedance. The disadvantage is that it is greatly affected by the environment, the detection accuracy is not high, and the detection result contains more fundamental components, resulting in relatively large operation losses.

2. Harmonic detection based on neural network

This is a kind of research result that can be obtained by improving the computing power and approximating any continuous function, and learning through the theory and analyzing the dynamic network, namely neural network. At this stage, the application of the network in power system harmonic detection is still in its infancy, and it is mainly used in power system harmonic prediction, harmonic source identification and harmonic measurement. The use of neural networks in harmonic measurement requires the consideration of network composition, algorithm selection, and sample determination.

3. Wavelet analysis method to measure harmonics

This aspect of research has made significant progress at this stage, mainly to solve the Fourier transform in the time domain without local defects and frequency domain completely localized defects, that is, locality in both the time domain and the frequency domain. This method can be used to project high-order harmonic changes in power systems to different scales, thus reflecting the characteristics of singular, high-frequency harmonic signals, thus providing a basis for harmonic analysis.

4. FFT variation method

The method for detecting the harmonics of the power system is based on the measurement method based on the digital signal processing. The main operation step is to first sample the voltage or current of the signal under test, and then transform and then use the computer to perform the Fourier transform. The phase coefficients and amplitudes of the respective harmonics are obtained. This method is currently the most widely used harmonic detection method in power system, and its accuracy, function and operation are simple, and the accuracy of harmonic detection is realized.