Harmonic and Inter-harmonic Detection Based on FFT and Nonlinear Optimization

In order to analyze harmonic and inter-harmonic parameters more accurately, a new detecting method that combined the nonlinear least squares and fast Fourier transform(FFT) was proposed. The FFT was used to produce a rough estimated value of harmonic parameters and then the signal model was set. Finally, the parameters can be estimated more accurately by the use of optimization algorithm which based on damped nonlinear-least squares method. The combined method solves the problem of inaccurate estimate by FFT and solves the problem of how to set the signal model and to choose initial value. The simulation results show that the combined method is effective and far more accuracy than interpolated Hanning window method.