The Research Of Harmonic Detection Methods In Gird Based On FFT

As the starting point of research harmonic question , harmonic measurement becomes first subject on study harmonics. The harmonics measurement based on Fourier Transform has been used widely,but it may appear the deviation (sampling synchronous deviation) because of the fluctuation of signal frequency.The deviation will lead to spectral leakage and picket fence effect which will degrade the accuracy of harmonics determination.To the above question, the new Synch-sampling——frequency adjustment sampling method——is proposed on the basis of the study. This method is the sampling frequency no longer a fixed, but it calculated by the real frequency of power grid. The key problem in the new AC sampling method is the precise measurement of the signal frequency. So it introduces a simple,reliable way which can be used in real-time conditions to calculate the signal frequency.Then the real-time calculate signal frequency algorithms solved with matlab. The results showed that method can quickly to Measure accurately the signal frequency. second, the frequency adjustment sampling method is solved with matlab when the frequency of electric network flutters. The results showed that frequency adjustment sampling method can reduce the synchronous deviation,and improve sampling effect.Finally, a high performance electric harmonic monitoring device is introduced which is based on TMS320LF2407 processor. the design of hardware frame,the development flow of DSP signal sampling program and signal processing program in this paper. A harmonic System Based on java is developing in this paper.