Distribution system and power quality

% % ECE 5750 DS & PQ % % Example on how to use FFT to obtain a waveform frequency spectrum % % Based on a Matlab example % Initialization clear all clc; Fs = 1000; % Sampling frequency T = 1/Fs; % Sample time L = 1000; % Length of signal t = (0:L-1)*T; % Time vector % Sum of a 50 Hz sinusoid and a 120 Hz sinusoid x = 0.7*sin(2*pi*50*t) + sin(2*pi*120*t); y = x + 2*randn(size(t)); % Two sinusoids plus noise figure(1) plot(Fs*t(1:50),y(1:50)) title('Signal Corrupted with Zero-Mean Random Noise') xlabel('Time, milliseconds') NFFT = 2^nextpow2(L); % Next power of 2 from length of y Y = fft(y,NFFT)/L; f = Fs/2*linspace(0,1,NFFT/2+1); % Plot single-sided amplitude spectrum % It is visible from Fig. 2 that the two significant components in y(t) % are 50-Hz and 120-Hz. Other components are noises. figure(2) plot(f,2*abs(Y(1:NFFT/2+1))) title('Single-Sided Amplitude Spectrum of y(t)') xlabel('Frequency (Hz)') ylabel('|Y(f)|')