A novel analytical technique for spectral analysis prediction in asynchronous pulsewidth modulated inverter systems

A novel analytical technique, based on a single Fourier series representation for pulsewidth modulation (PWM), is proposed for accurate evaluation of PWM spectra in inverter controlled motor drive systems where complex periodic reference signals are used. This method can thus be usefully employed for prediction of the critical harmonic distortion component amplitudes present and their power content in adjustable speed drives (ASD). Simulations, using the Fourier method, are presented for PWM model validation which are identical to those for asynchronous analog comparator modulator operation. Additional simulation of a typical motor drive system, with a PWM inverter kernel, and comparison with measured data attest to the accuracy of the Fourier approach. Results, identical to those obtained from the alternative FFT approach, are presented for the spectral content of a complex periodic PWM waveform which confirms the accuracy of the new analytical method