Robust, harmonic-injection system for single-switch, three-phase, discontinuous-conduction-mode boost rectifiers

摘要

In a single-switch, three-phase DCM boost rectifier, a voltage signal proportional to the inverted ac component of the rectified, three- phase, line-to-line input voltages is injected as a modulating signal into the control circuit to vary the duty cycle of the rectifier within one line cycle. As a result of its generation method, the injected signal is naturally synchronized with the three-phase, line-to-neutral input voltage. In addition, the injection method of this invention does not affect the closed-loop feedback control of the DCM boost rectifier since the injected signal is generated in an open-loop fashion. Three alternative methods to generate the injection signal are described. One method uses three low-frequency, step down transformers in generating the injection signal. The other two methods use operational amplifiers instead of the transformers.