Study Of Electrical Harmonic Analysis Based On Windows And Interpolated FFT

Since the end of the19Century, DC transmission was gradually replaced by ACtransmission, and the problem of power quality is paid close attention by scholars all over theworld, power quality effect economic and social development directly. However, with theimprovement of the power quality requirements, the harmonics harness becomes animmediate attention, and the premise of harmonics harness is how to detect harmonic signalsaccurately. Aiming at how to improve the harmonic detetion accurately, the following workshave been done.Firstly, this paper analyzes the development of domestic and international harmonicdetection. Aiming at the problems of the FFT, a Nuttall window and triple-spectral-lineinterpolated FFT is adopted. Considering the transient of power system signals, in order todetect the transient, wavelet transform is used to detect transients at first, and then do thefollowing analysis. In order to test the improved algorithm, two signals are used to compare inMATLAB simulation, one of which there is steady-state harmonic signal only, and another isjoined by the transient signal. The simulation of the first signal shows that the relative error ofharmonic ampitude is less than8.45×10-5%, the relative error of harmonic phase is less than4.06×10-3%, Among which the frequency absolute error and the amplitude and phase relativeerror of fundamental wave are4.18×10-10,2.27×10-7%and3.08×10-6%. The simulation of thesecond signal shows that the relative error of harmonic ampitude is less than8.85×10-5%, andthe relative error of harmonic phase is less than5.33×10-3%. The amplitude accuracydecreased0.047%and phase accuracy decreased0.9%compared with accuracy of the firstsignal. In addition, the effect of fitting times to harmonic detection accuracy is compared, thesimulation result show that the number of fitting height affects only the fundamental detectionaccuracy.Secondly, harmonic detection platform based on TMS320F2812which is a32bitfixed-point digital signal processor is constructed. In order to improve the detection accuracy,the filter circuit, the zero crossing detection circuit and phase-locked frequency multiplicationcircuit and AD correction circuit are designed, and the analysis and study of hardware designis analyzed by PROTEUS software.Finally, software design procedure is designed. Using the Code Composer Studio wrotethe SCI communication, GPIO initialization, A/D initialization and calibration procedures. Inaddition, In order to achieve a good human-computer interaction and data visualization,epigynous machine is made in Visual Basic platform, and this epigynous machine couldachieve interactive interface.