When using the FFT tool from the powergui, a whole cycle is not analyzed despite indicating the number of cycles is 1.

Question

Frank Mosely 2019-4-21

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回答： Santiago Alfonso Ospina Botero 2023-4-5

The signal being used as the input to the FFT analysis tool is a filtered inverter signal (filtered by hardware and PWM control). I expect the THD to be much less than 48.34% as this is the THD expected from an unfiltered inverter. If I increase the number of cycles to include more of my waveform, the THD increases.

Any suggestions?

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Kuluru Sudarsana Reddy 2021-5-18

I too have encountered the same issue. If anyone can help us to analyze the issue, that would be great

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Answer 1

Santiago Alfonso Ospina Botero 2023-4-5

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https://ww2.mathworks.cn/matlabcentral/answers/457692-when-using-the-fft-tool-from-the-powergui-a-whole-cycle-is-not-analyzed-despite-indicating-the-numb#answer_1209424

I beleive that your problem relies in the fundamental frequency that you have introduced (60Hz) when in reality the fundamental frec of your sinusoid is about 9.3 Hz. This would explain why the red line representing 1Cycle chops at around 0.02 s since 1/60 = 0.0167 s.

So I would recomend to change the fundamental frecuency to the actual sinusoid freaquency or increment the number of cycles to have a better representation of your signal for the FFT computation