Harmonic Analysis of SPWM Wave for Single-Phase Bridge Inverter

Two-level single-phase bridge inverters are widely used in distributed energy systems due to its topological symmetry and ease of modulation. The harmonic contents of modulated output waves are critical performance index in quantitatively determining the superiority or inferiority of a modulation strategy and in optimizing the modulation and filter parameters. For past decades, harmonic analyses on sinusoidal pulse width modulated (SPWM) waves of single-phase bridge inverters are mostly based on the double Fourier series representation, which is on the premise that SPWM wave is a two-dimensional periodic function of two variables with different frequencies. However, this premise is more tenable for pulse amplitude modulation (PAM) than for SPWM, since PAM is the product of a line-frequency sine wave and a carrier-frequency rectangular wave, whereas SPWM wave is the compared result of a line-frequency sine wave and a carrier- frequency triangular wave. This paper studies the double Fourier series representation of SPWM wave from double Fourier integral essence, develops a harmonic analysis method for SPWM wave with the aid of fast Fourier transform (FFT), correlates the harmonic spectra of PAM and SPWM, and finally, further analyzes the feasibility of double Fourier series on SPWM wave.