A hybrid technique for three phase synchronous PWM waveform generation for static converters

Analog controllers for PWM waveform generation with on-line optimization like delta modulation and model reference adaptive schemes are popular for inverters and synchronous rectifiers operating at unity power factor. Three dedicated analog controllers are required in such applications. In this paper a scheme is suggested for microcomputer based PWM implementation with only one analog controller. The other two PWM patterns are generated by the microcomputer and real time synchronous PWM control signals are communicated to the power converter through the parallel port of the computer. The resultant three phase pattern is of analog quality. The proposed controller provides fast dynamic response and smooth control over the entire operating range similar to analog controllers. A digital scheme is also presented which uses standard modulation techniques to obtain the PWM waveforms and generates synchronized PWM patterns. Analysis, implementation schemes and experimental results are presented in this paper