A Novel Three-Phase Current-Fed ZCS-PWM Converter Incorporating A Single Resonant DC Link Soft Commutation Snubber

Abstract

This paper presents a novel prototype three-phase current-fed PWM converter with switched-capacitor type resonant DC link commutation circuit operating with a new optimum PWM pattern strategy under a design consideration of low-pass filter, which can operate on the basis of the principle of zero current soft-switching commutation.In the first place, the steady-state operating principle of this converter with a new resonant DC link snubber circuit is described in connection with the equivalent operating circuit, together with the practical design procedure of the switched-capacitor type resonant DC link circuit. In the second place, the three-phase current-fed PWM converter with the switched-capacitor type resonant DC link circuit is discussed from a theoretical viewpoint on the basis of a design example for high-power applications. The actively delayed time correction method to compensate distorted currents due to a relatively long resonant commutation time is newly implemented in the open loop control scheme so as to acquire the new optimum PWM pattern. Finally, the experiment of set-up in laboratory system of this converter is concretely demonstrated herein to confirm a zero current soft-switching commutation of this converter. The comparative evaluations between current-fed hard-switching PWM and soft-switching PWM converters are carried out from a viewpoint of their PWM converter characteristics.