Double Fourier Integral Method for PWM Rectifiers to Estimate Harmonics of Uncontrolled Rectifiers

PWM rectifiers are gradually replacing controlled and uncontrolled rectifiers as the preferred technology in industrial applications. While estimating harmonic current emissions from theses devices is well known when connected to clean supplies, there is a need to improve the understanding of harmonic current emissions from PWM rectifiers arising when high levels of background voltage harmonic distortion are present. This paper presents a mathematical approach to describing the harmonic current emissions of an uncontrolled rectifier, as a special case of PWM rectifier, as a first stage to a understanding PWM rectifier harmonic emissions when high level of background harmonics are present. The approach uses derived mathematical equations to assess the influence of background voltage distortion on the harmonic current distortion of the rectifier. The mathematical expression for the harmonic current is derived using the Double Fourier Integral method.