Microcontroller-Based Implementation of a Direct AC-AC SPWM Power Converter

A novel low frequency AC-AC SPWM modulated frequency converter is implemented based on Microcontroller chip. The control function performed by the Microcontroller chip AT89C51 is twofold: firstly, to achieve frequency conversion by changing number N of half wave, between two natural commutation points. Secondly, to obtain voltage regulation by changing the duty-cycle of PWM pulse (high frequency) in the half wave of grid power passing through. As a result, the Microcontroller-based direct AC-AC converter can achieve voltage regulation and frequency conversion at the same time, which is suitable for motor of flexible low-frequency speed regulation. The Microcontroller-based control algorithm and the implementation are presented in detail and the design is verified by both simulation and experimental testing results.