Window Frequency Shift Algorithm For Power System Harmonic Analysis

With the operation of of power electronic devices, nonlinear loads and the applicationof DC transmission, FACTS technology, the harmonic pollution problem is becomingmore and more serious. Therefore, the accurate measurement of the harmonic parameters,to master the power of harmonic condition, is very important for the maintenance ofpower grid safety and economic operation. However, errors often appear in harmonicanalysis due to the fact that strictly synchronous sampling is difficult to acheive in thesituation of actural measurement. This paper makes a deep reasearch on the issue ofreducing or eliminating the errors caused by asynchronous sampling.Based on the analysis of spectrum leakage and fence effect caused by asynchronoussampling, the window and interpolation algorithm is introduced. It makes further researchon window criterion in frequency domain and spectral line interpolation algorithm.The window frequency shift algorithm based on window FFT and frequency shift isproposed in the paper. In the aspect of the algorithm realization, the algorithm selects theHanning window through the analysis various windows. On the interval relationship ofpeak spectral lines and the actual spectral lines, the peak spectral lines of samplingsequence are overlapped with its real position by use of spectrum shift method. Thewindow frequency shift algorithm can reduce synchronization error, and simple harmonicparameter estimation formulas are obtained. In this paper, the frequency shift problem isimproved and applied to the harmonic analysis. In addition, this method applies to bothsynchronous and asynchronous sampling.In the aspect of the algorithm verification, multifrequency sine wave signal model isselected according to the actual situation through the computer programming of windowinterpolation algorithm and window frequency shift algorithm in the environment ofMATLAB; the results confirm its reliability and effectiveness.