Application of Hanning window and interpolation algorithm in transformer terminal unit frequency analysis module and its influencing factors analysis

The Hanning window and interpolation algorithm is used to the frequency estimation for voltage and current signals acquired in transformer terminal unit (TTU), and the algorithm is validated by the frequency estimation for actual voltage signals. On this basis, the influence of signal frequency, harmonic, signal-to-noise ratio (SNR), sampling duration, sampling frequency and quantization of analog digital converter (ADC) on the accuracy of frequency estimation is investigated based on the numerically generated voltage signal. The results reveal that the error is proportional to the difference between the actual signal frequency and the rated value (50 Hz). When the total harmonic distortion (THD) varies in the range of 0~10%, the error is almost independent of THD. The error decreases with SNR, and the rate of decrease reduces with SNR. The sampling frequency has little effect on the error when the sampling duration is kept constant. When the quantization bit varies from 4 to 16, it has little effect on the error. Suggestions on the selection of sampling parameters for TTU frequency analysis using the Hanning window and interpolation algorithm are also given.