Synchronized phasor measuring method using recursive DFT with a window function

In uses, such as stability surveillance of an electric power system, the synchronous voltage current phasor measurement using GPS satellite base timing keeping technology is demanded. In the past, the synchronous phasor measurement technique of a voltage current based in DFT conversion theory was proposed, and it was established as an IEC standard[1]. In the actual electric power system, the frequency of voltage in each place is delicately different, and it is always changing. Since the sampling data in the time window of fixed width cannot take in the integer cycle of a voltage waveform and does not satisfy the signal periodicity conditions of Fourier transform, a spectrum leakage phenomenon occurs. By this, the accuracy of the synchronous phasor measurement by single DFT-BIN frequency falls. This paper proposes the method of realizing recursively DFT conversion with a window function [RWDFT] which can reduce the influence of system voltage frequency change. Moreover, the method of calculating Phasor of true signal frequency is proposed by compounding three or more DFT conversion factors. In simulation verification, the synchronous phasor measuring method which applied the above two methods has checked that a highly precise Phasor measurement result was obtained in system voltage frequency change.