Abstract:In order to reduce the measurement and calculation errors that were caused by asynchronous sampling due to grid frequency fluctuation, this paper proposed an improved scheme of traditional discrete Fourier transform (DFT) measuring algorithm. In this improved scheme, an eigenvalue equation was constructed using the recurrence relation of sampling point function, a sampling data window with variable data number was chosen, the period truncation error due to system frequency deviation was reduced, and an improved recursive synchronized phasor measurement method was derived. Compared with the traditional DFT algorithm, the phase angle and amplitude measurement accuracies of the improved algorithm were significantly increased, which were tested under the conditions of fundamental frequency rating offsets were set as constant value, sinusoidal quantity, linear function value and random number, etc. And on this basis, this paper studied the impacts of sampling frequency and sampling strategy on algorithm performance, and the application effect of algorithm on the signal contains harmonic. The test results show that the calculation accuracy and realtime performance of the improved DFT algorithm were significantly increased.

Keywords:synchronized phasor measurement, discrete Fourier transform, error, constant frequency sampling