Naturally commutated current-fed three-phase bidirectional soft-switching DC-DC converter with new modulation technique

Micro-grids with energy storage elements are a reliable solution for the stochastic nature of the renewable energy sources, conventional grids and load fluctuations. Hence, a three-phase current-fed full-bridge dual-active bridge (DAB) bidirectional dc-dc converter with current-fed inverter at Low Voltage Side (LVS) and voltage-fed rectifier at High Voltage Side (HVS) is proposed to integrate the low-voltage, high-current source to the grid. The current-fed DAB is designed for interfacing 48 V and 380 V dc buses. The proposed converter implements 1200 modulation along with secondary-side modulation that helps achieve natural commutation of LVS active switches, ZVS turn-on of LVS bottom switches and ZVS turn-on of HVS active switches. This eliminates the use of passive/active clamp circuits as used in conventional current-fed topologies to mitigate the voltage-spike across the switches. The soft-switching is maintained over the entire range of operation. The detailed modulation scheme, operation mode analysis, design and soft-switching conditions are derived in the paper. The proposed modulation technique is compared with the 1800 modulation to illustrate the improvement in performance and efficiency of the converter with implemented modulation technique. The experimental results have been illustrated for full load (1 kW) and partial load (500 W) conditions as a proof-of-concept to validate the claims.