Based on Quasi-synchronous Sampling Harmonic Analysis Method and Its DSP Realization

The synchronous integrated period sampling is difficult to realize in practice when the grid frequency fluctuates, which results in the problem of spectral leakage when the Fast Fourier Transform (FFT) is used for harmonic analysis. In order to deal with the problem posed by FFT, the Discrete Fourier Transform (DFT) based on quasi-synchronous sampling algorithm is proposed in the paper. The hardware architecture is built with a 16-bit AD converter and 32-bit high speed DSP processor as the core. This analysis method and its realization based on DSP can obviously correct the synchronization error caused by the small deviation of the power network frequency, which ensures a higher accuracy of the harmonic amplitudes and phase angles. The accuracy is about 0.1 percent when the frequency variation is in the range of ±10%, more than adequate for power quality surveys.