Naturally Commutated Current-fed Three-Phase Bidirectional Soft-switching DC-DC Converter With 120° Modulation Technique

A three-phase current-fed full-bridge dual-active bridge bidirectional dc-dc converter is proposed to integrate 48 and 380 V dc buses or energy storage to dc microgrid. 120 degrees plus secondary-side modulation technique is implemented to achieve natural commutation of low-voltage-side current-fed devices and zero voltage switching turn-on of high-voltage-side devices. This eliminates the use of passive/active clamp circuits as used in conventional current-fed topologies to mitigate the voltage-spike across the switches. Soft-switching is attained over entire operating range (200 W to 1 kW). Detailed analysis of proposed modulation scheme is reported and soft-switching conditions are derived. Proposed modulation is compared with the 180 degrees modulation scheme to demonstrate converter performance and efficiency. Experimental results have been illustrated for proof-of-concept to validate the claims. Peak efficiencies of 95.8% and 93.8% are obtained at around half load for 59 and 48 V inputs, respectively.