Experimental Verification of a Two-Stage Bidirectional DC/DC Converter with Separated Commutation and Asymmetrical Structure of Current-Source Stage

This paper analyses a topology and control algorithm of an isolated bidirectional two stage DC/DC converter. The low-voltage primary stage is a voltage-source inverter (VSI) and the high-voltage secondary stage is a current-source inverter (CSI). The CSI topology is a full bridge, where the switches of the positive rail are conventional (IGBT with an antiparallel diode), while the negative rail switches are four-quadrant (anti-series connected IGBTs with antiparallel diodes). A special modulation method (separated commutation algorithm) is analysed for the energy transfer mode from the VSI to the CSI. This algorithm provides zero voltage switching (ZVS) turn-on and capacitive snubber-assisted turn-off for the VSI transistors. The CSI transistors turn-off with zero current switching (ZCS), while their turn-on is assisted by an inductive snubber. The proposed concepts are verified with simulations in MATLAB and experimental prototype. The topology is proposed for high power battery or fuel cell systems.