Strategy for switching period selection in random pulse width modulation to shape the noise spectrum

In this study a new random pulse width modulation (RPWM) has been proposed. The aim of this method is to create a gap at selective frequency in voltage spectrum to prevent the resonant frequencies excitation. This gap can be placed in human hearing band. Hence, the proposed method can reduce acoustic noise in loads supplied by power electronic converters. Unlike conventional RPWM techniques, in this method the switching period is dependent on the duty ratio. In other words, in each switching cycle the switching period is determined as a function of duty ratio and switching periods in pervious switching cycles. The experimental results confirm the ability of the proposed method for reducing noise power at a selected frequency in voltage spectrum.