Research And Application Of Interharmonic Detection Algorithm In Power System

With the advancement of new energy strategy,a large number of high-power power electronic equipment and other nonlinear loads have been put into use in the power grid,and the harmonic and interharmonic problems in the power grid have become the norm.Efficient power system harmonic and interharmonic detection algorithm can provide detailed data support for the governance of power system harmonic and interharmonic.In depth power system harmonic and interharmonic detection algorithm has important practical significance to promote the construction of green energy grid.Aiming at the problems of the existing windowed function interpolation algorithm of discrete Fourier transform,such as the limited ability to suppress spectrum leakage when adding low-order windowed function,and the difficulty to derive the interpolation formula of high-order windowed function,this paper proposes an improved Hanning windowed function interpolation algorithm based on the simple interpolation formula of Hanning windowed function.The interpolation formula of m-th Hanning window function is obtained.The feasibility of the improved Hanning window function interpolation algorithm and its superiority over the existing algorithm are verified by an example.The improved Hanning window function interpolation algorithm in this paper,with the increase of cosine combination window terms,the main lobe of the spectrum is gradually widened.When the main lobe width is larger than the frequency interval between harmonics and interharmonics,the frequency spectrum of each wave overlaps,and the further improvement of detection accuracy is limited.In order to solve this problem,this paper proposes a second improvement strategy,which uses the real spectrum to do interpolation calculation to get the approximate frequency of the signal,and then uses the spectrum analytical formula to correct the spectrum line,and then carries on interpolation calculation,and finally obtains higher accuracy of harmonic and interharmonic detection results.Finally,an example is used to verify the feasibility of the algorithm,and the detection accuracy is further improved.Based on the analysis and verification of a large number of examples,the high-power NNPC device is selected to build the frequency conversion circuit simulation experiment based on Simulink software,and the algorithm in this paper is applied to check the inter harmonic of the system.According to the inspection results,the corresponding filter circuit is built to verify the reliability and practicability of the algorithm.Based on FPGA development board,the preliminary design and implementation of power system harmonic and interharmonic detector are carried out,and the feasibility of the algorithm is further verified by hardware in the loop simulation experiment.