I am trying to find THD of 2 H-Bridge cascade Multilevel inverter. THD calculated using THD Formula and the THD in FFT analysis are different for a particular case, in all other cases it matches exactly. so which one is accurate THD in MATLAB or THD by formula?
Please find the THD formula which have used attached
You can model the FFT in Matlab or simulink, then you can compare them,
i did try FFT for more then 100 simulations, both matched were same for 80-90%. and rest were different. so i got this doubt about which is is accurate.
what about the "particular case" in which you found the discrepancy? Does it correspond to limit conditions (e.g. very low or very high THD) ? Have you cheched if the simulated waveforms seem to be reasonable in that case?
Dear Paolo Stefano Crovetti,
Yes wave form which has been considered for FFT seems responsible, in a particular condition 01 modulation index, 2 sources H-Bridge Multilevel inverter. Switching angles generated by SHE equation eliminating 3rd harmonics. I have attached the angles and waveform, if carefully examining the waveform it has considered only one step 0-25v instead of the whole waveform. There is a minor change in THD. Equation generates 38% whereas MATLAB generates 36%. But checking the fundamental it just 26V. It has to be 50. This is why I got this doubt.
Thanks and Regards
Vadhiraj
Hello,
From the simulated waveform itself you understand that matched one gives accuracy.
So you take that THD in FFT for your analysis
All the best
by
R.Suresh Babu
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