Three-phase current-fed soft-switching PWM converter with switched capacitor type resonant DC-link

This paper presents a novel prototype suitable for three-phase current-fed PWM converter with a switched capacitor type resonant DC link circuit, which can operate under a principle of zero current soft switching commutation. In this converter, the optimum PWM pattern processing method is applied. In this paper, the operating principle in steady-state of the current-fed converter with a new resonant DC link circuit treated is described by using the equivalent operating circuit. The practical design procedure of the switched capacitor type resonant DC link circuit designed for three-phase current-fed PWM converter is discussed from a theoretical viewpoint, together with a design example for high-power applications. The active delayed time compensation method to revise distorted currents due to resonant commutation time to improve the input current waveforms of this converter is newly implemented in the control scheme so as to acquire the optimum PWM pattern. The feasible experiment to confirm zero current soft switching commutation of this converter is demonstrated. The comparative studies between current-fed hard switching PWM and soft-switching PWM are described and discussed for their PWM converter characteristics.