Multi-mode microcontroller based PWM modulator suitable for fast vector control

This paper describes the development and implementation of a PWM modulator that produces waveforms suitable to control all types of voltage source invertor-fed AC motor drives, from fast vector controllers to high power applications. The modulator provides two basic operation modes: (1) an asynchronous mode, performing an improved version of sinusoidal PWM modulation based on the regular-sampling of a modulating waveform; and (2) a kind of synchronous modulation, where commutation instants are set accordingly to stored pre-calculated optimized PWM patterns. Transition between the two modes can be performed without problems. To implement this PWM control strategy, a 16/32 bit microcontroller is used without any additional components. The system was tested for a small power induction motor and the results are presented.