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I want to estimate the THD of a voltage signal (output from a frequency inverter). At the begining, I need to estimate the power of the signal at frequency domain. To doing so, I should use a periodogram or a FFT.

Matlab uses periodogram in his THD function. I know that are differences between FFT and periodogram, as shown in this question. But, wich method should I use? and why?

Thanks.

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Just for answer the question, basically there is no difference at all. My problem was that I've compared a modified periodogram against a FFT. Modified periodogram does have a difference; but simple periodogram doesn't.

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  • $\begingroup$ Might want to note the unit difference between |FFT| and |FFT|^2 (periodogram) in your answer, in case THD is computed using the harmonic power and not amplitude $\endgroup$ – Robert L. Aug 27 '18 at 2:13

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