MATLAB: Is the fundamental frequency at the 15th harmonic order

fast fourier transformfftfourier analysisfourier transformharmonicsthd

Dear Matlab Community.
I am trying to implement a code to show harmonic content and order in Matlab. my fundamental is supposed to be at harmonic order 1, however the ouput plot I am getting is wrong and I am having difficulies proceeding.
I would really apreciate any help. Thanks 
[D,S,R] = xlsread('test data.xls');    
v = D(:,2);
Signal = D(:,2);                                                 
Ts = 0.00005;                                               % Sampling Interval (seconds)
Fs = 1/Ts;                                                  % Sampling Frequency (Hz)
Fn = Fs/2; 
%PERFOM FFT
N = length(Signal);
meanSignal = mean(Signal);                                  % ‘Signal’ Mean
FTSignal = fft(Signal-meanSignal)/N;                    
Fv = linspace(0, 1, fix(numel(FTSignal)/2)+1)*Fn;           % Frequency Vector
Iv = 1:numel(Fv);                                           % Index Vector
%Plotting Harmonics (THD)
har_mag = abs(FTSignal(Iv))*2;
figure;
bar(har_mag(1:20),0.4)
xlabel('Harmonic Order','fontsize',10);
ylabel('Voltage (V)','fontsize',10)
hold off

Best Answer

I am not certain what you are doing, or what result you want.
One problem is that you also need to specify the x-values of the bars in your bar call: 
bar(Fv(1:20), har_mag(1:20),0.4)
If you want to find all the relevant peaks and their frequencies, add these lines after your existing (posted) code: 
[pks,locs] = findpeaks(har_mag, 'MinPeakProminence',0.5);
FreqPeaks = table(Fv(locs)', pks, 20*log10(pks), 'VariableNames',{'Freq', 'Amp', 'dB'})
figure
plot(Fv, 20*log10(har_mag))
hold on
plot(Fv(locs), 20*log10(har_mag(locs)), '+r')
hold off
grid
axis([0  1200    -15  60])
The ‘FreqPeaks’ table has all the identified peaks (linear and dB) and their associated frequencies.
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