PWM Systems in Power Converters: An Extension of the ``Subharmonic'' Method

In this paper the extension of the subharmonic method for pulse-width modulation (PWM) systems, in the case in which the ratio between modulating and carrier wave amplitudes can be varied from 0 to ∞, is studied in an analytical way. This method allows us to obtain an inverter output waveform variable continuously from a nearly sinusoidal to a square wave and to increase somewhat the amplitude of the fundamental output wave without a significant worsening of the harmonic content, a feature particularly useful for drives with wide speed variations or which need an optimized use of dc power supply.