fft algorithm.
in [Matlab]
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From: Issopui on 19 Jun 2010 07:37 Hello there. I have just implemented a 3 phase PWM DC/AC converter in Simulink using IGBTD with a "RL" load and I have to write and algorithm to show the Frequency domain. I don't really know how to do it.I have just try to write something down onmy M-file which is: % tstep = t(2)- t(1); % fsample = 1/tstep; % time1 = t1; % time2 = t2; t = 0:1/50:50-1/50; x = 0.8*500*sin (2*pi*t); y = fft(x); m = abs(y); f = (0:length(y)-1)*50/length(y); plot(f,20*log10(m)), % stem(x,y,'.'), ylabel('Abs. Magnitude'), I think I may need to use the commented line to be able to visualize any load voltage like line to line or line to neutral Hope u guys can help me Many Thanks
From: Greg Heath on 19 Jun 2010 13:42 On Jun 19, 7:37 am, "Issopui " <manka_...(a)yahoo.com> wrote: > Hello there. > I have just implemented a 3 phase PWM DC/AC converter in Simulink using IGBTD with a "RL" load and I have to write and algorithm to show the Frequency domain. I don't really know how to do it.I have just try to write something down onmy M-file which is: > % tstep = t(2)- t(1); > % fsample = 1/tstep; > % time1 = t1; > % time2 = t2; > > t = 0:1/50:50-1/50; > x = 0.8*500*sin (2*pi*t); > y = fft(x); > m = abs(y); > f = (0:length(y)-1)*50/length(y); > plot(f,20*log10(m)), > % stem(x,y,'.'), > ylabel('Abs. Magnitude'), Fs = 50 N = length(x) df = Fs/N f = df*(0:N-1); fb = f-df*(N/2); % Zero centered frequency interval PSD = abs(y).^2/N; Power Spectral density PSDdb = 10*log10(PSD); plot(fb, fftshift(PSDdB)) ylabel('Power Spectral Density (dB)') > I think I may need to use the commented line to be able to > visualize any load voltage like line to line or line to neutral Too many points to use "stem" (personal opinion). > Hope u guys can help me Have a specific question? Hope this helps. Greg
From: Issopui on 21 Jun 2010 16:30 > Fs = 50 > N = length(x) > df = Fs/N > f = df*(0:N-1); > fb = f-df*(N/2); % Zero centered frequency interval > > PSD = abs(y).^2/N; Power Spectral density > PSDdb = 10*log10(PSD); > plot(fb, fftshift(PSDdB)) > ylabel('Power Spectral Density (dB)') > > > I think I may need to use the commented line to be able to > > visualize any load voltage like line to line or line to neutral > > Too many points to use "stem" (personal opinion). > > > Hope u guys can help me > > Have a specific question? Thanks for ur help. I have another question how can I introduce it as a function so that when I called it on Matlab workspace I can see the plot? I mean something like this one from one of the function I got in the lab. myfft(voltage1.time,voltage1.signals.values,0,0.02,0.1) When I type the above line on the matlad i got the plot is there any way I can do the same for the program u help me with? Many Thanks > Hope this helps. > > Greg
From: Greg Heath on 21 Jun 2010 20:10 On Jun 21, 4:30 pm, "Issopui " <manka_...(a)yahoo.com> wrote: > > Fs = 50 > > N = length(x) > > df = Fs/N > > f = df*(0:N-1); > > fb = f-df*(N/2); % Zero centered frequency interval > > > PSD = abs(y).^2/N; Power Spectral density > > PSDdb = 10*log10(PSD); > > plot(fb, fftshift(PSDdB)) > > ylabel('Power Spectral Density (dB)') > > > > I think I may need to use the commented line to be able to > > > visualize any load voltage like line to line or line to neutral > > > Too many points to use "stem" (personal opinion). > > > > Hope u guys can help me > > > Have a specific question? > > Thanks for ur help. > I have another question how can I introduce it as a function so that when I called it on Matlab workspace I can see the plot? > I mean something like this one from one of the function I got in the lab. > myfft(voltage1.time,voltage1.signals.values,0,0.02,0.1) > When I type the above line on the matlad i got the plot is there any way I can do the same for the program u help me with? Yes. It is straightforward. Post your code if you have debugging trouble. Hope this helps. Greg
From: Issopui on 25 Jun 2010 18:48
Hi Greg, Many thanks for ur help it has worked as required.I would like to show u some file I have got I don't know if I can send it by ur e-mail as I think I can send a file here and in case u know how to do it here (sending a file) just let me know and i will send it to u. Many thanks. |