How do I calculate THD in MATLAB?

[powersolda]

How can I calculate THD (Total Harmonic Distortion) in a MATLAB file?, I have signal out put of the inverter, Please note, I know I can do this in Simulink, I am looking for a way to do this from MATLAB directly.

 

[jjx]

Here is one already started thread
https://www.edaboard.com/threads/57557/
and from your post to the mathworks you seem to be quite eager...

Essentially do the FFT as said in the thread above. Find the power bin, sum all the powers in 2*bin, 3*bin, etc.

If you do not use coherent sampling and if you distortion components are folded around Nyquist, you have to be a bit creative.

Some pseudo code is given here, but you need to adjust for the starting DC point (power_bin+1), etc.

% x is signal
XX = abs(fft(x)).^2;

% assume peak is fundamental
power_bin = min( find(XX==max(XX)));
signal_power = XX(power_bin);
dist_power = sum( [2 3 4 5 6]*power_bin );
THD = dist_power/signal_power; % Or whatever definition you like.

You can also look at the time-domain data and fit a sinusoid to that data. The deviation between measured and fitted sinusoid will be your SNDR (~THD if noise is low).

 

[powersolda]

thank you my friend , i want calculate THD of this single

 

[powersolda]

---------- Post added at 15:54 ---------- Previous post was at 15:10 ----------

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