Harmonic current by using FFT

Question

OMAR MOUSA 2021-11-15

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1586664-harmonic-current-by-using-fft

回答： Star Strider 2021-11-15

Hi all,

I'm new in matlab and i need help how to write a code for harmonics current (1,3,5,7) by using FFT, I wrote some codes but the problem is how can i get the harmonics if i have time serie of data??

I attached the code that i got

data_all=xlsread('main reading-day1-1sec');

x=data_all(:,10);

%%Signal in Time-domain for x

fs=1/1; %sampling freq

ts=1/fs; %sampling time

L=length(x); %length of the signal (x)

t=(0:L-1)/fs; %the time require for block data t=N/fs ot t=N*ts

%Signal in Frequency-domain for x

fhs_fin = zeros(L,1);

NEFT=2^nextpow2(L); % Next power of 2 from length of x

x_fft=abs(fft(x,NEFT));

freq=fs/2*linspace(0,2,NEFT+1/2);

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Answer 1

Star Strider 2021-11-15

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1586664-harmonic-current-by-using-fft#answer_831399

That looks like it should work, although for the most accurrate results, divide ‘x_fft’ by the row size of ‘x’ or since it is a column vector, ‘L’. If ‘data_all’ has a time vector, first be certain that it is sampled regularly and consistently, and then use it to define the frequency vector to use with theFourier transfoorm plot.

The findpeaks function will probably help identify the harmonic peaks.

.