Frequency Estimation by Two-Layered Iterative DFT with Re-Sampling Under Transient Condition
Frequency deviation incurred by sudden changes of frequency introduces harmonics and inter-harmonics in the power system, which influences the accuracy of frequency estimation with the method of discrete Fourier transform (DFT). A two-layered iterative DFT (TLI-DFT) with re-sampling was presented to measure the frequency in non-steady states. A simple frequency estimation method named exponential sampling is amended to calculate the initial sampling frequency in the inner-layered process of the DFT iteration. TLI-DFT can track the frequency in non-steady states that is contaminated by decaying direct current offsets. Mean squared error of measured frequency and rate of change of frequency indicate that the proposed algorithm is valid and more accurate than the traditional one under a transient condition in the power system.
KeywordsPhasor measurement Frequency tracking Transient condition DFT Exponential re-sampling
This work was supported by Hainan Provincial Key R. & D. Projects of China (ZDYF2016010 and ZDYF2018012) and the National Natural Science Foundation of China (No. 61661018).
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