A new direct digital PWM technique for microprocessor-based PWM inverters

This paper describes a new pulse width modulation (PWM) scheme suitable for a microprocessor-based PWM inverter. Optimal switching patterns (i.e., width and position of the pulses) minimizing a performance index can be generated in real time by numerical calculation using the microprocessor-based control system. The switching patterns and harmonics of the output waveforms have been investigated by simulation. This PWM method is compared with conventional methods, such as the natural PWM and the direct PWM. The simulation results show that the proposed scheme has much less low-order harmonics than the other methods. Finally, the microprocessor-based implementation of the scheme is presented. The validity of the proposed method is verified by experiments using a microprocessor-based control system.