Integral-series Fourier analysis of chaotic PWM patterns for common mode voltage stresses

Abstract

In this study, the theory of pulse width modulation (PWM) is developed for both sine-wave PWM (SPWM) and chaotic sine-wave PWM (CSPWM). In SPWM, power spectra are analysed by an analytical method such as double Fourier series (DFS) technique, and the integral-series Fourier method is fully devised and analytically theorised for CSPWM. It is shown that the root-mean-square value of inverter's zero-sequence voltage does not rely on carrier and reference frequency in fixedfrequency SPWM, while in CSPWM, this depends on frequency modulating gain and chaotic sequence of numbers. Also, the computation time of purely numerical harmonic analysis can be much heavier than analytical ones. Furthermore, the DFS and integral-series Fourier methods are applied to SPWM and CSPWM with two different frame sizes of squirrel cage motors for the shaft voltage and the electro-magnetic interference (EMI). The numerical and experimental results show that CSPWM can have positive effect on the shaft voltage while it definitely weakens the EMI problems.