Island detection method based on wavelet packet energy spectrum

Abstract

The invention relates to an island detection method based on the wavelet packet energy spectrum. In the method, the wavelet theory is applied to decompose the signal into different frequency components, so that the fault information can be obviously displayed. The method is characterized by comprising the stages of signal processing and island identification and comprising the following specific steps: 1) directly measuring the voltage signal at the point of common coupling (PCC) and carrying out wavelet packet decomposition on the detected voltage signal; 2) reconfiguring the wavelet packet decomposition coefficient and extracting the signals in the frequency band ranges; 3) computing the energy characteristic value of each frequency band signal according to the energy expression shown in the specification; 4) constructing the fault characteristic vector T with number of dimensions being 2<j> by adopting the energy of the frequency band signals as the elements; 5) establishing a sample model and then determining the fault characteristic vector P according to the statistical average of the sample space; and 6) establishing mapping relationships between the energy characteristic vectors and the fault conditions, making a fault query table with the congruent relationships between the fault conditions and the parameter variation and storing the fault query table, identifying the faults based on the fault query table and simultaneously displaying the diagnosis results.

Description

technical field [0001] The invention relates to a distributed microgrid grid-connected island monitoring method, in particular to an island detection method based on wavelet packet energy spectrum. Background technique [0002] With the increasingly prominent energy problems, new energy power generation systems such as photovoltaic power generation and wind power generation have developed rapidly. Such as figure 1 As shown, the distributed generation system (DG) is generally located on the distribution line of the regional power system, and is connected to the large power grid through the point of public coupling (PCC) of the regional power system. Parallel operation of DG and large power grid will cause a series of problems to be solved, the most important of which is the detection of island operation status. Islanding detection is a technical problem that must be solved when DG is connected to the grid. It means that after the grid suddenly stops supplying power, the ph...

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Problems solved by technology

[0004] The purpose of the present invention is to solve the problem that the islanding detection is easily disturbed by the power grid disturbance, and the power grid disturbance is misjudged as the islanding situation, causing the DG system to exit the operation. It provides an islanding detection method based on the wavelet packet energy spectrum. It applies Wavelet theory, which decomposes the signal into different frequency components, can clearly display the fault information

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