FFT Analysis // 0Hz component fundamental?

Altair Forum User
Altair Forum User
Altair Employee
edited August 2023 in Community Q&A

Greetings,

While attempting to preform harmonic analysis on my 3-phase inverter circuit, there is a significant component at 0Hz in the frequency spectrum. The fundamental frequency of the inverter is 23.4kHz which has an amplitude significantly less than that of the 0Hz component. In particular, I am interested in the 3rd harmonic component and am not sure how PSIM preforms the FFT analysis.

Is the 0Hz component the 1st harmonic in the PSIM analysis (making 46.8kHz the 3rd harmonic), or does the fundamental frequency remain at 23.4kHz (making 70.2kHz the 3rd harmonic as I expected to see)?

Any assistance on this matter would be most appreciated.

Thank you kindly,
P. Hetzel

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2023

    Hi Philip,

    PSIM performs the FFT of the data on screen. It is a good idea to zoom in a on a few cycles of the converter working in steady state otherwise startup transients will be included.

    This tutorial video gets into things https://youtu.be/OciQhywsGww

    Please contact our support email for help with you simulaiton.

    The frequencies in the sweep are the real frequencies so the content that you'll be interested in will be at 46.8KHz there is no frequency normalization. Make sure your timestep is small enough to properly resolve 46.8K, I would suggest a minimum of 10 data points per cycle. Time step = 1/(46.8k*10)

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